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    <lastmod>2019-03-23</lastmod>
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    <loc>https://www.gregschool.org/new-blog/super-intelligence-rise-of-the-machines-btkn7</loc>
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    <lastmod>2019-03-21</lastmod>
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      <image:title>Articles - Super Intelligence: Rise of the Machines</image:title>
      <image:caption>Infographic source: https://www.huawei.com/en/about-huawei/publications/winwin-magazine/ai/how-intelligent-will-ai-get</image:caption>
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      <image:title>Articles - Super Intelligence: Rise of the Machines</image:title>
      <image:caption>The two robots above help clean the floor and give directions to passengers at the Seoul-Incheon International Airport.</image:caption>
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      <image:title>Articles - Super Intelligence: Rise of the Machines</image:title>
      <image:caption>Cover art from the Sci-Fi Masterworks edition of Do Androids Dream of Electric Sheep?</image:caption>
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      <image:title>Articles - Super Intelligence: Rise of the Machines</image:title>
      <image:caption>An example environment fed to the AI physicist. Here, the field of view is divided into four quadrants, each of which is governed by a different physical effect, such as gravity or an electromagnetic field. The dots and lines represent the ball’s trajectory through the environment. Based on how a ball moves through the environment, the AI must use the strategies it was given to describe the physical laws that are governing the ball’s motion. Image: Tegmark and Wu/arXiv</image:caption>
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      <image:title>Articles - Super Intelligence: Rise of the Machines</image:title>
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  </url>
  <url>
    <loc>https://www.gregschool.org/new-blog/robots-and-their-uses-br26w</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2019-03-22</lastmod>
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      <image:title>Articles - Robots and their Uses</image:title>
      <image:caption>https://www.artstation.com/artwork/YxRbq</image:caption>
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      <image:title>Articles - Robots and their Uses</image:title>
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      <image:caption>Atlas from Boston Dynamics</image:caption>
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      <image:title>Articles - Robots and their Uses</image:title>
      <image:caption>https://me.me/i/if-you-could-visualize-grahams-curiosity-number-your-head-would-3896085</image:caption>
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      <image:title>Articles - Robots and their Uses</image:title>
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      <image:title>Articles - Robots and their Uses</image:title>
      <image:caption>Image retrieved from: https://wall.alphacoders.com/big.php?i=524246</image:caption>
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  </url>
  <url>
    <loc>https://www.gregschool.org/new-blog/rotational-inertia-nkczj</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2019-03-23</lastmod>
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      <image:title>Articles - Rotational Inertia</image:title>
      <image:caption>Figure 1: The rotational inertia of a hollow sphere is given by \(I=\frac{2}{3}MR^2\) and the rotational inertia of a solid ball is given by \(\frac{2}{5}MR^2\). Since the lever arms \(r\) (perpendicular distance from the axis of rotation) of each mass element in the solid sphere is smaller (because each mass is closer to the axis of rotation) than the lever arms in the hollow sphere (since each mass is farther away from the axis of rotation), the solid sphere must have a smaller rotational inertia. According to Equation (2), if \(r\) is smaller, then the function \(r^2\) that we are taking the area under is smaller.</image:caption>
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  </url>
  <url>
    <loc>https://www.gregschool.org/new-blog/2019/2/7/leaving-the-solar-system-4aahb</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2019-02-17</lastmod>
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      <image:title>Articles - Leaving the Solar System: Introduction to the Outward Bound Series</image:title>
      <image:caption>Infographic retrieved from: https://www.spaceanswers.com/issue-previews/5025/5025/</image:caption>
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      <image:title>Articles - Leaving the Solar System: Introduction to the Outward Bound Series</image:title>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5c69ae4815fcc00f43ca1f63/1549578332475/WH-Phoebe-1024x599%5B1%5D.jpg</image:loc>
      <image:title>Articles - Leaving the Solar System: Introduction to the Outward Bound Series</image:title>
      <image:caption>Image retrieved from: https://crossingzebras.com/wormhole-space-after-phoebe/</image:caption>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5c69ae4815fcc00f43ca1f65/1549567172244/quote-the-moral-landscape-is-the-framework-i-use-for-thinking-about-questions-of-morality-sam-harris-12-51-41%5B1%5D.jpg</image:loc>
      <image:title>Articles - Leaving the Solar System: Introduction to the Outward Bound Series</image:title>
      <image:caption>Quote by Sam Harris, author of the book, The Moral Landscape.</image:caption>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5c69ae4815fcc00f43ca1f71/1549574245734/wright_brothers%5B1%5D.jpg</image:loc>
      <image:title>Articles - Leaving the Solar System: Introduction to the Outward Bound Series</image:title>
      <image:caption>The Wright brothers on the steps of their boyhood home at 7 Hawthorn St. in Dayton.\(^{[1]}\) Carillon Historical Park</image:caption>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5c69ae4815fcc00f43ca1f77/1549579569564/grav_lens_telescope%5B1%5D%5B1%5D.jpg</image:loc>
      <image:title>Articles - Leaving the Solar System: Introduction to the Outward Bound Series</image:title>
      <image:caption>A gravitational lens telescope, as envisioned by Claudio Maccone in his 2009 book Deep Space Flight and Communications. (Claudio Maccone)</image:caption>
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    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/5c69ae4815fcc00f43ca1f73/5c69ae4815fcc00f43ca1f74/1549578964152/This-is-How-Earth-Moves-1.jpg</image:loc>
      <image:title>Articles - Leaving the Solar System: Introduction to the Outward Bound Series</image:title>
      <image:caption>This image illustrates the fact that the Sun is actually moving through space relative to the Milky Way galaxy; from this frame of reference, the Earth is moving in a spiral-shaped path. Of course, we can actually alter this path as well as the Sun’s speed using a type of megastructure known as a Shkadov thruster; you could, in fact, give the Sun (and the Earth which goes around it) a radically different path which heads off-course away from the galaxy. Image retrieved from: https://wordlesstech.com/this-is-how-earth-moves/</image:caption>
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      <image:title>Articles - Leaving the Solar System: Introduction to the Outward Bound Series</image:title>
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      <image:title>Articles - Leaving the Solar System: Introduction to the Outward Bound Series</image:title>
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  <url>
    <loc>https://www.gregschool.org/new-blog/2018/5/23/preliminary-interstellar-missions-prelude-to-the-stars-336f8-saywf</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2019-02-22</lastmod>
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      <image:title>Articles - Preliminary Interstellar Missions: Prelude to the Stars</image:title>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5c6f634aa4222f0da6e6f0ff/1549254809131/Stromatolites_in_Sharkbay%5B1%5D.jpg</image:loc>
      <image:title>Articles - Preliminary Interstellar Missions: Prelude to the Stars</image:title>
      <image:caption>The stromatolites shown in the photograph above are fossils which were produced by cyanobacteria 3.5 billion years in Shark Bay, Australia. Cyanobacteria - a simple, single-celled lifeform - produced large amounts of oxygen via photosynthesis causing the first major oxygenation even in Earth’s history. Photograph taken by Paul Harrison.</image:caption>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5c6f634aa4222f0da6e6f101/1549254809133/Great+Oxidization+Event.jpg</image:loc>
      <image:title>Articles - Preliminary Interstellar Missions: Prelude to the Stars</image:title>
      <image:caption>Diagram of the evolution of atmospheric oxygen concentration during the history of the planet. © Ido, Pierre Sans-Jofre</image:caption>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/5c6f634aa4222f0da6e6f0f1/5c6f634aa4222f0da6e6f0f2/1537289631769/grav_lens_telescope%5B1%5D.jpg</image:loc>
      <image:title>Articles - Preliminary Interstellar Missions: Prelude to the Stars</image:title>
      <image:caption>A gravitational lens telescope, as envisioned by Claudio Maccone in his 2009 book Deep Space Flight and Communications. (Claudio Maccone)</image:caption>
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    <image:image>
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      <image:title>Articles - Preliminary Interstellar Missions: Prelude to the Stars</image:title>
      <image:caption>Illustration of the James Webb Space Telescope, current as of September 2009. Top side. Image Source: https://web.archive.org/web/20100527230418/http://www.jwst.nasa.gov/images_artist13532.html</image:caption>
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      <image:title>Articles - Preliminary Interstellar Missions: Prelude to the Stars</image:title>
      <image:caption>Artist's impression of the planet Ross 128 b, with the star Ross 128 visible in the background\(^{[1]}\) Credit: European Southern Observatory</image:caption>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5c6f634aa4222f0da6e6f103/1549254809135/50lys%5B1%5D.gif</image:loc>
      <image:title>Articles - Preliminary Interstellar Missions: Prelude to the Stars</image:title>
      <image:caption>The image above is a map of a small fraction of nearby stars in our stellar neighborhood. It is a map of 130 stars located within 50 lightyears of us which are visible with the naked eye. This map shows only a tiny percent of that stars within 50 lightyears away from the Sun. There are in fact 1,800 known stars within this volume of space. To eliminate the threat of nearby supernovae, our descendants will one day visit all of these stars, either directly in which case their species actually arrives at the star, or indirectly by sending spacecraft and robots to those stars.</image:caption>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5c6f634aa4222f0da6e6f0fd/1549254809129/NASA-WhatBiosignaturesDoesLifeProduce-20180625%5B1%5D.jpg</image:loc>
      <image:title>Articles - Preliminary Interstellar Missions: Prelude to the Stars</image:title>
      <image:caption>The combination of certain molecules and the absence of certain molecules in an exoplanet’s atmosphere is only likely if life is inhabited on that world: such combinations are called disequilibrium mixtures. As the light emitted from a star passes through an exoplanet’s atmosphere, the molecules in that exoplanet’s atmosphere absorb only certain wavelengths. Given which wavelengths were absorbed, we can determine whether or not disequilibrium mixtures are present in that exoplanet’s atmosphere and, consequently, assess the likelihood that extraterrestrial life inhabits that world. NASA/Aaron Gronsta</image:caption>
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      <image:title>Articles - Preliminary Interstellar Missions: Prelude to the Stars</image:title>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5c6f634aa4222f0da6e6f0f7/1549254809125/mars_hs-2016-15-a-full_tif%5B1%5D.jpg</image:loc>
      <image:title>Articles - Preliminary Interstellar Missions: Prelude to the Stars</image:title>
      <image:caption>“This Hubble Space Telescope image of Mars shows details 20 to 30 miles across. A solar gravitational lens telescope would get even sharper views of exoplanets up to 100 light years away.”\(^{[4]}\) (STScI/AURA), J. Bell (ASU), and M. Wolff) Source URL: https://www.airspacemag.com/daily-planet/ultimate-space-telescope-would-use-sun-lens-180962499/</image:caption>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5c6f634aa4222f0da6e6f105/1549254809137/Welcome_to_the_Universe_by_Neil_deGrasse_Tyson%3B_book_cover.jpg</image:loc>
      <image:title>Articles - Preliminary Interstellar Missions: Prelude to the Stars</image:title>
      <image:caption>Welcome to the Universe: An Astrophysical Tour is a popular science book by Neil deGrasse Tyson, Michael A. Strauss, and J. Richard Gott, based on an introductory astrophysics course they co-taught at Princeton University. The book was published by the Princeton University Press on September 20, 2016.\(^{[6]}\)</image:caption>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/5c6f634aa4222f0da6e6f109/5c6f634aa4222f0da6e6f10a/1549254809141/dvv.jpg</image:loc>
      <image:title>Articles - Preliminary Interstellar Missions: Prelude to the Stars</image:title>
      <image:caption>Infographic above is from Time Magazine April 10, 2000.</image:caption>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/new-blog/spaceship-comets-and-highways-through-space-5ec48</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2019-02-24</lastmod>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/5c73127ce79c704c50c881c6/5c73127ce79c704c50c881c7/1536859707540/Asteroid+Mining+Station+by+Bas+Ruhe%5B1%5D.jpg</image:loc>
      <image:title>Articles - Spaceship Comets and Highways Through Space - Copy of Asteroid Mining Station</image:title>
      <image:caption>Artist’s depicion of a colonized asteroid. Artwork by Bas Ruhe from Artstation.</image:caption>
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      <image:title>Articles - Spaceship Comets and Highways Through Space - Copy of Spaceship Asteroid</image:title>
      <image:caption>“The concept of turning an asteroid into a spacecraft is not entirely new: conceptual designer Bryan Versteeg has been working with the Mars One Team to imagine how we could use large asteroids for mining, transportation and habitat.”\(^{[2]}\) Credit: http://www.spacehabs.com/</image:caption>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5c73127ce79c704c50c881f6/1536901738138/yyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyy.png</image:loc>
      <image:title>Articles - Spaceship Comets and Highways Through Space</image:title>
      <image:caption>“Each of the hexagons in this figure represents one of the mirror farms shown in [previous image]. The dots are schematic representations of the habitats occupied by each twent-five-member “band.” in reality the habitats would probably be much too small to be seen on this scale.”\(^{[37]}\)</image:caption>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5c73127ce79c704c50c881f2/1536978228964/pale+blue+dottttttttttttttttttttttttttttttttttttttttttttttttttt.jpg</image:loc>
      <image:title>Articles - Spaceship Comets and Highways Through Space</image:title>
      <image:caption>In Carl Sagan’s book, Pale Blue Dot, he talked about the possibility of interstellar human communities living in comets in the Kuiper belt, the Oort cloud, and beyond.</image:caption>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5c73127ce79c704c50c881f4/1536900915403/hexagonal+array.png</image:loc>
      <image:title>Articles - Spaceship Comets and Highways Through Space</image:title>
      <image:caption>“This hexagonal array of starlight mirrors might support a co-living group of twenty-five adults and children. Each of the mirrors is about the size of the continental United States, and the entire mirror “farm” is about 30,000 kilometers across.”\(^{[37]}\)</image:caption>
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      <image:title>Articles - Spaceship Comets and Highways Through Space - Copy of Death Star</image:title>
      <image:caption>Artist’s depiction of a death star. By building a shell world of the kind described by the scientist Paul Birch around a faint dead star (i.e. a brown dwarf), the faint radiation which that star gives off could be collected and used to power a gigantic laser mounted on the surface of a shell world. Thus, as far fetched as the idea might seem, it isn’t totally implausable. Image retrieved from: Artist’s depiction of a comet being used as a spaceship. Image retrieved from: http://earth-chronicles.ru/news/2014-04-21-63940</image:caption>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/5c73127ce79c704c50c8819c/5c73127ce79c704c50c8819d/1536986254211/lunar-mining-base.jpg</image:loc>
      <image:title>Articles - Spaceship Comets and Highways Through Space</image:title>
      <image:caption>The power requirements of buried human habitats and propellant production plants could be met by the widely spaced solar power panels shown above. Image: anna.j.nesterova@gmail.com</image:caption>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/5c73127ce79c704c50c881d8/5c73127ce79c704c50c881d9/1536987150213/MarsAndTheSpaceElevator%5B1%5D.jpg</image:loc>
      <image:title>Articles - Spaceship Comets and Highways Through Space</image:title>
      <image:caption>“Here is a new montage showing the base of the space elevator on the tented town called "Sheffield", built on the summit of Pavonis Mons volcano (see Red Mars). The cable is supposed to be 10m thick, which means here that Sheffield city is very big here, at a large level of development. On the foreground, you can see colored urban lights. I imagine the main entry to the planet's surface would be like a rich and welcoming show for new settlers. I also imagine the tent' skin would be blue, to balance the red and grey landscape.”\(^{[59]}\)</image:caption>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/5c73127ce79c704c50c881d8/5c73127ce79c704c50c881db/1537230346111/SheffieldAndTheSpaceElevator%5B1%5D.jpg</image:loc>
      <image:title>Articles - Spaceship Comets and Highways Through Space</image:title>
      <image:caption>Artist’s impression of a space elevator connecting to the domed over city, Sheifeild, located on Pvonic Mons in Kim Robinson’s Mars trilogy. Images retrieved from: http://davinci-marsdesign.blogspot.com/2012/04/sheffield-and-space-elevator.html</image:caption>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5c73127ce79c704c50c881e8/1536896886414/jhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhh.jpg</image:loc>
      <image:title>Articles - Spaceship Comets and Highways Through Space</image:title>
      <image:caption>“This artist's concept puts solar system distances in perspective. The scale bar is in astronomical units, with each set distance beyond 1 AU representing 10 times the previous distance. One AU is the distance from the Sun to the Earth, which is about 93 million miles or 150 million kilometers. Neptune, the most distant planet from the Sun, is about 30 AU.”\(^{[4]}\) Image Credit: NASA/JPL-Caltech</image:caption>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5c73127ce79c704c50c881fc/1538678002285/1449-enz.jpg</image:loc>
      <image:title>Articles - Spaceship Comets and Highways Through Space</image:title>
      <image:caption>The map above shows the migration patterns and timeline of the Polynesians who traveled from Asia to America by hopping from one tiny archipelago to another. Our descendants who travel from the Earth to the exoplanet Proxima B might adopt an analogous strategy by hopping from one comet to another until they reach their final destination. Image retrieved from: https://teara.govt.nz/en/map/1449/map-of-pacific-migrations</image:caption>
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      <image:title>Articles - Spaceship Comets and Highways Through Space - Copy of Trip to Alpha Centauri using a Starshot Probe</image:title>
      <image:caption>SCMP Graphic: Dennis Wong, Dang Elland Sources: Universe Today, SIMBAD Dacabase, SCMP research</image:caption>
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      <image:title>Articles - Spaceship Comets and Highways Through Space</image:title>
      <image:caption>Image Source: https://i4is.org/wp-content/uploads/2018/05/Principium21.pdf</image:caption>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5c73127ce79c704c50c881fe/1538678306195/photosynthesis-process-2.jpg</image:loc>
      <image:title>Articles - Spaceship Comets and Highways Through Space</image:title>
      <image:caption>The infographic above shows how plants, via the process of photosynethesis, use light (sunlight or artificial light), carbon dioxide and water to produce breathable oxygen.</image:caption>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/5c73127ce79c704c50c881c2/5c73127ce79c704c50c881c3/1536859913266/evolvingaste%5B1%5D.jpg</image:loc>
      <image:title>Articles - Spaceship Comets and Highways Through Space</image:title>
      <image:caption>Credit: Nils Faber &amp; Angelo Vermeulen</image:caption>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/5c73127ce79c704c50c881f8/5c73127ce79c704c50c881f9/1538604155467/1_hHjG69bPm3VrMyUG2idPKg.jpeg</image:loc>
      <image:title>Articles - Spaceship Comets and Highways Through Space</image:title>
      <image:caption>“Conceptual model of a growing and evolving asteroid starship. The image of comet 67P by ESA is used as a placeholder for a large asteroid.”\(^{[6]}\) Composite image by Francisco Muñoz and Anton Dobrevski</image:caption>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5c73127ce79c704c50c881ea/1537041005162/energy-from-space-1.jpg</image:loc>
      <image:title>Articles - Spaceship Comets and Highways Through Space</image:title>
      <image:caption>Using a nuclear reactor to fuse together deuterium and helium-3 would generate a lot of energy; that energy would be transferred to a shock absorber on the rear of a spaceship which would give the spaceship thrust thereby causing it to accelerate. Image retrieved from: https://science.howstuffworks.com/environmental/green-science/energy-from-space.htm</image:caption>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/5c73127ce79c704c50c881ec/5c73127ce79c704c50c881ef/1536898850377/jhm27etrwqj7fgpuxvuj%5B1%5D.jpg</image:loc>
      <image:title>Articles - Spaceship Comets and Highways Through Space</image:title>
      <image:caption>Asteroid settlement concept. Credit and Copyright: Bryan Versteeg / DSI.</image:caption>
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    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/5c73127ce79c704c50c881ec/5c73127ce79c704c50c881ed/1536898837446/liian1htqo3l6hvx4kkj%5B1%5D.jpg</image:loc>
      <image:title>Articles - Spaceship Comets and Highways Through Space</image:title>
      <image:caption>Concept art for DSI's "Harvestor" craft. Credit and Copyright: Bryan Versteeg / DSI.</image:caption>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/5c73127ce79c704c50c88196/5c73127ce79c704c50c88197/1537229057732/maxresdefault.jpg</image:loc>
      <image:title>Articles - Spaceship Comets and Highways Through Space - Copy of Starshot Probe</image:title>
      <image:caption>Depiction of a Starshot probe being accellerated by Earth-based lasers. Credit: Breakthrough Starshot</image:caption>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/5c73127ce79c704c50c881ae/5c73127ce79c704c50c881af/1536889609120/jakub-grygier-026-interstellar-travel-ad.jpg</image:loc>
      <image:title>Articles - Spaceship Comets and Highways Through Space - Copy of Interstellar Spaceship</image:title>
      <image:caption>Artist’s depiction of an interstellar spaceship accellerated by laser beams. Artwork by Jakub Grygier from Artstation.</image:caption>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5c73127ce79c704c50c88194/1536288589788/Skylab-73-HC-440HR%5B1%5D.jpg</image:loc>
      <image:title>Articles - Spaceship Comets and Highways Through Space</image:title>
      <image:caption>Image of the Saturn V rocket launching to space. Image courtesy of NASA.</image:caption>
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    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5c73127ce79c704c50c8819a/1536985604633/41WSCf9QqtL._SX333_BO1%2C204%2C203%2C200_.jpg</image:loc>
      <image:title>Articles - Spaceship Comets and Highways Through Space</image:title>
      <image:caption>Robert Zubrin’s book, Entering Space, covers topics ranging from colonizing Mars and the solar system and explores the feasibility of interstellar travel with known physics.\(^{[1]}\)</image:caption>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/5c73127ce79c704c50c881de/5c73127ce79c704c50c881e3/1537243316507/kkkk.png</image:loc>
      <image:title>Articles - Spaceship Comets and Highways Through Space</image:title>
      <image:caption>Infographics represent a visual explanation of the so-called terrariums discussed in Kim Stanley Robinsons, 2312. Also, there is a slight error in the last infographic: the asteroid does not spin, rather a cylinder inside of the hollowed out asteroid is the thing which is actually spinning. Infographics created by Pablo Defendini. Infographics retrieved from: http://www.defendini.com/2312.html</image:caption>
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  </url>
  <url>
    <loc>https://www.gregschool.org/new-blog/utopia-life-in-the-year-2100-4e9ga</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2019-03-22</lastmod>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/5c952727419202e734058a06/5c952727419202e734058a07/1544066498793/524246%5B1%5D.jpg</image:loc>
      <image:title>Articles - Utopia: Life in the Year 2100</image:title>
      <image:caption>Image retrieved from: https://wall.alphacoders.com/big.php?i=524246</image:caption>
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      <image:title>Articles - Utopia: Life in the Year 2100</image:title>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5c952727419202e734058a02/1553277163807/Neolithic-revolution-ancient-farmers.jpg</image:loc>
      <image:title>Articles - Utopia: Life in the Year 2100</image:title>
      <image:caption>The Neolithic Revolution (which began, independently, in multiple different civilization 10 to 12 thousand years ago) occurred when, for the first time, we humans began to domesticate plants and animals.</image:caption>
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      <image:title>Articles - Utopia: Life in the Year 2100</image:title>
      <image:caption>“Civilians watch a small fleet orbit around Uranus' moon Miranda.” Credit: https://www.artstation.com/artwork/mqZVx9</image:caption>
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      <image:title>Articles - Utopia: Life in the Year 2100</image:title>
      <image:caption>Image (click to enlarge) of lab-grown meat.</image:caption>
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      <image:title>Articles - Utopia: Life in the Year 2100</image:title>
      <image:caption>Robert McCall, “The Prologue and the Promise”</image:caption>
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      <image:title>Articles - Utopia: Life in the Year 2100</image:title>
      <image:caption>”Flipping good ... the Japanese cuisine machine hasn't dropped a pancake yet.”\(^{[3]}\) Image: Huis Ten Bosch/Facebook</image:caption>
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      <image:title>Articles - Utopia: Life in the Year 2100</image:title>
      <image:caption>“Base jumping off the tallest cliff in the Solar System, located on Uranus' moon Miranda. Uranus itself, along with a few other moons (from the top left to bottom right: Ariel (here on the far side of Uranus), Belinda, Puck and Portia) are seen in the background of the last shot. On Uranus´small moon Miranda lies a monumental cliff wall believed to be the tallest in the Solar System. It is called Verona Rupes. Observations are limited but it is certain that the cliffs rise at least 5 kilometers above the ground below. Maybe even twice as much. This extreme height combined with Miranda´s low gravity (0,018g) would make for a spectacular base-jump. After taking the leap from the top edge you could fall for at least 12 minutes and, with the help of a small rocket to brake your fall toward the bottom, end up landing safely on your feet. Miranda´s close orbit around giant Uranus also makes a magnificent huge cyan ball in the sky. The scene is built mostly in CG, except for the people who are shot live action and composited into the environment, and the foreground cliffs in the first shot which are made from several photos of a place in Norway known as "The Pulpit Rock". For building the landscape I used (amongst others) this satellite photo of Verona Rupes, taken by NASAs Voyager 2 during the flyby of Uranus in 1986. For the color and texture of Uranus I used this photo as reference. Also by Voyager 2, NASA.”\({[4]}\) Source: http://www.erikwernquist.com/wanderers/gallery_verona_rupes.html</image:caption>
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      <image:title>Articles - Utopia: Life in the Year 2100</image:title>
      <image:caption>Photographs of the two pioneers of rocketry science, Konstantin Tsiolkovsky (left) and Robert Goddard (right).</image:caption>
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      <image:title>Articles - Utopia: Life in the Year 2100</image:title>
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      <image:title>Articles - Utopia: Life in the Year 2100</image:title>
      <image:caption>“A diorama showing Homo erectus, the earliest human species that is known to have controlled fire, from inside the National Museum of Mongolian History in Ulaanbaatar, Mongolia.”\(^{[1]}\)</image:caption>
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  </url>
  <url>
    <loc>https://www.gregschool.org/new-blog/technological-revolutions-98ybg</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2019-03-22</lastmod>
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      <image:title>Articles - Technological Revolutions</image:title>
      <image:caption>“Ploughing with a yoke of horned cattle in Ancient Egypt. Painting from the burial chamber of Sennedjem, c. 1200 BC.”\(^{[2]}\)</image:caption>
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      <image:title>Articles - Technological Revolutions</image:title>
      <image:caption>Credit: https://en.wikipedia.org/wiki/File:Ending_Aging.jpg</image:caption>
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      <image:title>Articles - Technological Revolutions</image:title>
      <image:caption>Artist’s depiction of nanobots patroling the human bloodstream. Image retrieved from: https://www.cnet.com/news/nanobots-can-now-swarm-like-fish-to-perform-complex-medical-tasks/</image:caption>
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      <image:title>Articles - Technological Revolutions</image:title>
      <image:caption>A plot of CPU transistor counts against dates of introduction. Source URL: https://commons.wikimedia.org/wiki/File:Moore%27s_Law_Transistor_Count_1971-2016.png</image:caption>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5c954a577817f7912a1c34bf/1546631734569/Newcomens_Dampfmaschine_aus_Meyers_1890%5B1%5D.png</image:loc>
      <image:title>Articles - Technological Revolutions</image:title>
      <image:caption>“Newcomen's steam-powered atmospheric engine was the first practical piston steam engine. Subsequent steam engines were to power the Industrial Revolution.”\(^{[7]}\)</image:caption>
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      <image:title>Articles - Technological Revolutions</image:title>
      <image:caption>Image retrieved from: https://iconshots.com/concept/the-future-of-technology-should-we-be-worried/</image:caption>
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      <image:title>Articles - Technological Revolutions</image:title>
      <image:caption>The following graph reflects the empirical fact that as time has progressed, we have achieved superconductivity at higher and higher temperatures. Credit: Pia Jensen Ray</image:caption>
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      <image:caption>In the book, Life 3.0, the cosmologist and AI researcher Max Tegmark explores the implications of AI and robotics.</image:caption>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5c954a587817f7912a1c34cd/1546553988948/stock-photo-the-train-moving-on-the-overpass-and-the-city-on-the-water-concept-of-modern-transport-futuristic-769589683%5B1%5D.jpg</image:loc>
      <image:title>Articles - Technological Revolutions</image:title>
      <image:caption>Arcologies on the surface of the sea could be connected by maglev transportation systems. As we discuss in the article, How to Colonize the Earth?, these sea-steading towers would extend within the depths of the oceans; the cities underneath the sea surface could also be connected by maglev monorail systems. Image Credit: https://www.shutterstock.com/image-illustration/train-moving-on-overpass-city-water-769589683?src=l4eCjvmchovnXUJuJH_WrQ-1-29</image:caption>
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      <image:title>Articles - Technological Revolutions</image:title>
      <image:caption>This graph illustrates the increase in standards of living and life expectancy that occurred during the time of the first two industrial revolutions.\(^{[3]}\)</image:caption>
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      <image:title>Articles - Technological Revolutions</image:title>
      <image:caption>“The Principia states Newton's laws of motion, forming the foundation of classical mechanics; Newton's law of universal gravitation; and a derivation of Kepler's laws of planetary motion (which Kepler first obtained empirically). The Principia is considered one of the most important works in the history of science.”\(^{[5]}\)</image:caption>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5c954a577817f7912a1c34bd/1546631010156/Joule%27s_Apparatus_%28Harper%27s_Scan%29%5B1%5D.png</image:loc>
      <image:title>Articles - Technological Revolutions</image:title>
      <image:caption>“Engraving of James Joule's apparatus for measuring the mechanical equivalent of heat, in which altitude potential energy from the weight on the right is converted into heat at the left, through stirring of water.”\(^{[7]}\)</image:caption>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5c954a577817f7912a1c34c9/1546462732450/stock-photo-concept-of-magnetic-levitation-train-moving-on-the-sky-way-in-vacuum-tunnel-across-the-city-modern-755107045%5B1%5D.jpg</image:loc>
      <image:title>Articles - Technological Revolutions</image:title>
      <image:caption>The image above portrays how large buildings (which could be arcologies that people live in) could be connected by maglev trains operating within evacuated tunnels. Image Credit: https://www.shutterstock.com/image-illustration/concept-magnetic-levitation-train-moving-on-755107045</image:caption>
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      <image:title>Articles - Technological Revolutions</image:title>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5c954a577817f7912a1c34bb/1546630451461/Newtons_laws_in_latin%5B1%5D.jpg</image:loc>
      <image:title>Articles - Technological Revolutions</image:title>
      <image:caption>“Newton's First and Second laws, in Latin, from the original 1687 Principia Mathematica”\(^{[6]}\)</image:caption>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5c954a577817f7912a1c34a5/1546555589793/</image:loc>
      <image:title>Articles - Technological Revolutions</image:title>
      <image:caption>“Smithsonian scientists and their Chinese colleagues found this and other handaxes in the same sediment layer with tektites, small rocks that formed during a meteor impact 803,000 years ago. Since the handaxes and tektites were in the same layer, both are the same age. Early humans must have moved into the area right after the impact. They may have made the handaxes from rocks that were exposed when forests burned.”\(^{[1]}\) Image Credit: James Di Loreto, &amp; Donald H. Hurlbert, Smithsonian Institution</image:caption>
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    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5c954a577817f7912a1c34c7/1546635697448/Meissner_effect_p1390048%5B1%5D.jpg</image:loc>
      <image:title>Articles - Technological Revolutions</image:title>
      <image:caption>“A magnet levitating above a high-temperature superconductor, cooled with liquid nitrogen. Persistent electric current flows on the surface of the superconductor, acting to exclude the magnetic field of the magnet (Faraday's law of induction). This current effectively forms an electromagnet that repels the magnet.” Image source: https://en.wikipedia.org/wiki/Superconductivity#/media/File:Meissner_effect_p1390048.jpg</image:caption>
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  </url>
  <url>
    <loc>https://www.gregschool.org/new-blog/2018/5/23/star-lifting-colonizing-the-stars-and-the-galaxies-5mjpt-9w4hc</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2019-03-19</lastmod>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5c9015faee6eb0728acd220c/1552852554589/Local_Group_and_nearest_galaxies%5B1%5D.jpg</image:loc>
      <image:title>Articles - Star Lifting: Colonizing the Stars and the Galaxies</image:title>
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    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/5c9015faee6eb0728acd2206/5c9015faee6eb0728acd2207/1536791569975/neil-blevins-megastructures-1-ringworld-color-sketch%5B1%5D.jpg</image:loc>
      <image:title>Articles - Star Lifting: Colonizing the Stars and the Galaxies</image:title>
      <image:caption>Artist’s depiction of a ring world. Artwork by Neil Blevins.</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/5c9015faee6eb0728acd2206/5c9015faee6eb0728acd2209/1536791569979/neil-blevins-megastructures-1-ringworld-design-packet%5B1%5D.jpg</image:loc>
      <image:title>Articles - Star Lifting: Colonizing the Stars and the Galaxies</image:title>
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      <image:title>Articles - Star Lifting: Colonizing the Stars and the Galaxies</image:title>
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      <image:title>Articles - Star Lifting: Colonizing the Stars and the Galaxies</image:title>
      <image:caption>Artist’s depiction of a star lifter. Artwork by Neil Blevins.</image:caption>
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    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5c9015faee6eb0728acd2202/1536791569973/Physics_of_the_future_Kaku_2011%5B1%5D.jpg</image:loc>
      <image:title>Articles - Star Lifting: Colonizing the Stars and the Galaxies</image:title>
      <image:caption>"Physics of the Future: How Science Will Shape Human Destiny and Our Daily Lives by the Year 2100 is a 2011 book by theoretical physicist Michio Kaku, author of Hyperspace and Physics of the Impossible. In it Kaku speculates about possible future technological development over the next 100 years. He interviews notable scientists about their fields of research and lays out his vision of coming developments in medicine, computing, artificial intelligence, nanotechnology, and energy production. The book was on the New York Times Bestseller List for five weeks."</image:caption>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/5c9015faee6eb0728acd21f0/5c9015faee6eb0728acd21f1/1552943531025/1080p-Space-Desktop-Background-hd-desktop-wallpapers-cool-images-hd-apple-background-wallpapers-colourfull-free-display-lovely-wallpapers.jpg</image:loc>
      <image:title>Articles - Star Lifting: Colonizing the Stars and the Galaxies</image:title>
      <image:caption>Image retrieved from: https://thewallpaper.co/preview/?wallpaper=1080p-space-desktop-background-hd-desktop-wallpapers-cool-images-hd-apple-background-wallpapers-colourfull-free-display-lovely-wallpapers-1920x1080</image:caption>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5c9015faee6eb0728acd21ee/1552861724343/neil-blevins-megastructures-9-gas-giant-refinery-5.jpg</image:loc>
      <image:title>Articles - Star Lifting: Colonizing the Stars and the Galaxies</image:title>
      <image:caption>Artist’s depiction of gas giant refineries used to extract materials such as helium-3 and deuterium from the atmosphere of one of the Jovian planets. Artwork by Neil Blevins at Artstation.</image:caption>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/5c9015faee6eb0728acd21f4/5c9015faee6eb0728acd21f5/1552862368589/neil-blevins-megastructures-12-nicoll-dyson-laser-design-packet.jpg</image:loc>
      <image:title>Articles - Star Lifting: Colonizing the Stars and the Galaxies</image:title>
      <image:caption>Artist’s depiction of a Nicoll-Dyson Laser. Artwork by Neil Blevins at ArtStation.</image:caption>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/5c9015faee6eb0728acd21e6/5c9015faee6eb0728acd21e7/1552959611722/jeremy-jozwik-ia-kuiperbeltterrain-comp2-0084.jpg</image:loc>
      <image:title>Articles - Star Lifting: Colonizing the Stars and the Galaxies - Kuiper Belt Laser Array</image:title>
      <image:caption>Artist’s impression of an array of lasers built on a comet in the Kuiper Belt. These laser stations would also be built on comets within Oort clouds (not jude our own) and interstellar space to create an interstellar highway. Artwork by Jeremy Jozwik from Artstation who is also a member of the SFIA production team.</image:caption>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5c9015faee6eb0728acd2200/1528407608550/Star_lifting_1.svg%5B1%5D.png</image:loc>
      <image:title>Articles - Star Lifting: Colonizing the Stars and the Galaxies</image:title>
      <image:caption>Figure 1: A star lifter would consist of a ring of solar power stations and ion accelerators distributed around a star in the shape of a ring.</image:caption>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5c9015faee6eb0728acd2204/1528412559259/star+lifter.jpg</image:loc>
      <image:title>Articles - Star Lifting: Colonizing the Stars and the Galaxies</image:title>
      <image:caption>Figure 2</image:caption>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/5c9015faee6eb0728acd21e2/5c9015faee6eb0728acd21e3/1552959594319/neil-blevins-megastructures-7-star-lifter-3d-sketch.jpg</image:loc>
      <image:title>Articles - Star Lifting: Colonizing the Stars and the Galaxies - Star Lifting</image:title>
      <image:caption>“A star lifter removes mass from a star for either raw materials or to change the nature of the star itself. For example, you may remove mass from the star to collect hydrogen or other elements. Or you could remove mass in order to extend the life of the star, to make the star dimmer, or reduce the chances of a super nova.” Artwork by Neil Blevins from Artstation.</image:caption>
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      <image:title>Articles - Star Lifting: Colonizing the Stars and the Galaxies</image:title>
      <image:caption>Concept art by Mark Molnar</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5c9015faee6eb0728acd21f8/1552862976200/lzlsart9qi311%5B1%5D.jpg</image:loc>
      <image:title>Articles - Star Lifting: Colonizing the Stars and the Galaxies</image:title>
      <image:caption>Nicoll-Dyson Beam “Unleashing The Nicoll-Dyson Beam from Gigastructural Engineering &amp; More. Inward Perfection has never been so easy when you can delete your enemies Capital systems with the press of a button. Edit: It also has multiple settings. Ranging from reducing all infrastructure to rubble to Solar System Deleter.” Image retrieved from: https://www.reddit.com/r/Stellaris/comments/8qgwe9/fear_me_for_i_am_your_apocalypse/</image:caption>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/new-blog/string-theory-and-colonizing-the-multiverse-mbzy6-94szd</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2019-03-21</lastmod>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5c92fac0c83025f04d004da3/1552974215990/universeismath.jpg</image:loc>
      <image:title>Articles - String Theory and Colonizing the Multiverse</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/5c92fac0c83025f04d004d9f/5c92fac0c83025f04d004da0/1536805148903/gateway_hub_04_by_lorddoomhammer-d9u3226.png</image:loc>
      <image:title>Articles - String Theory and Colonizing the Multiverse</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5c92fac0c83025f04d004da5/1553057433719/four_forces%5B1%5D.jpg</image:loc>
      <image:title>Articles - String Theory and Colonizing the Multiverse</image:title>
      <image:caption>Image Credit: https://physicswithsampurkis.files.wordpress.com/2014/01/four_forces.jpg</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5c92fac0c83025f04d004dab/1541982430321/shutterstock_84250684.jpg</image:loc>
      <image:title>Articles - String Theory and Colonizing the Multiverse</image:title>
      <image:caption>Our universe may be one of many, physicists say. Credit: Shutterstock/Victor Habbick</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5c92fac0c83025f04d004daf/1553060137245/CERN_LHC%5B1%5D.jpg</image:loc>
      <image:title>Articles - String Theory and Colonizing the Multiverse</image:title>
      <image:caption>The image above shows a section of the LHC (Large Hadron Collider).</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5c92fac0c83025f04d004da9/1553058165874/crystal_to_string%5B1%5D.jpg</image:loc>
      <image:title>Articles - String Theory and Colonizing the Multiverse</image:title>
      <image:caption>The image above shows how various different small objects compare to each other in terms of size. Image retrieved from: http://www.particlecentral.com/strings_page.html</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5c92fac0c83025f04d004db1/1553060486672/matrioshka+brainnnn.png</image:loc>
      <image:title>Articles - String Theory and Colonizing the Multiverse</image:title>
      <image:caption>“A matrioshka brain is a hypothetical megastructure proposed by Robert Bradbury, based on the Dyson sphere, of immense computational capacity. It is an example of a Class B stellar engine, employing the entire energy output of a star to drive computer systems.”\(^{[2]}\) Image from Steve Bowers</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5c92fac0c83025f04d004dad/1553060002632/LeonardSusskindStanford2009_cropped%5B1%5D.jpg</image:loc>
      <image:title>Articles - String Theory and Colonizing the Multiverse</image:title>
      <image:caption>Leonard Susskind</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5c92fac0c83025f04d004da7/1553057859737/calabi-yau7%5B1%5D.gif</image:loc>
      <image:title>Articles - String Theory and Colonizing the Multiverse</image:title>
      <image:caption>“String Theory predicts the existence of more than the 3 space dimensions and 1 time dimension we are all familiar with. According to string theory, there are additional dimensions that we are unfamiliar with because they are curled up into tiny complicated shapes that can only be seen on tiny scales. If we could shrink to this tiny, Planck-sized scale we could see that at every 3D point in space, we can also explore 6 additional dimensions. This animation shows an array of Calabi-Yau spaces which are projections of these higher dimensions into the more familiar dimensions we are aware of.”\(^{[1]}\)</image:caption>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/classical-mechanics</loc>
    <changefreq>daily</changefreq>
    <priority>0.75</priority>
    <lastmod>2018-07-04</lastmod>
  </url>
  <url>
    <loc>https://www.gregschool.org/classical-mechanics/2017/5/14/rotational-kinematics</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-09</lastmod>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59dbf83c59cc688076b7fdd1/1507588166242/gfnf.jpg</image:loc>
      <image:title>Oscillatory and rotational motion - Rotational Kinematics</image:title>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/classical-mechanics/2017/5/14/torque</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-11</lastmod>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59dbf930c027d89dcc0d2228/1507588404050/gfnf.jpg</image:loc>
      <image:title>Oscillatory and rotational motion - Torque</image:title>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/classical-mechanics/2017/5/14/introduction-to-rotational-kinetic-energy</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-09</lastmod>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59dbf8b9197aeaa9a58d0716/1507588284735/gfnf.jpg</image:loc>
      <image:title>Oscillatory and rotational motion - Introduction to Rotational Kinetic Energy</image:title>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/classical-mechanics/2017/5/14/4ufuuy7fweohxl2tk6hryzmsq50amd</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-09</lastmod>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59dbf78990badec5d2319ab7/1507587980466/gfnf.jpg</image:loc>
      <image:title>Oscillatory and rotational motion - Introduction to Mechanical Waves</image:title>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/classical-mechanics/category/Classical+Mechanics</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
  </url>
  <url>
    <loc>https://www.gregschool.org/electromagnetism</loc>
    <changefreq>daily</changefreq>
    <priority>0.75</priority>
    <lastmod>2017-09-06</lastmod>
  </url>
  <url>
    <loc>https://www.gregschool.org/electromagnetism/2017/5/14/columns-law</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-09</lastmod>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59dc434d32601e9d148bf0b6/1507607378489/electromagnetism+thumbnaillllll+imageeee.jpg</image:loc>
      <image:title>Electromagnetism - Column's Law</image:title>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/electromagnetism/2017/5/14/electric-flux</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-09</lastmod>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59dc3ee0914e6b12a393fde8/1507606244584/electromagnetism+thumbnaillllll+imageeee.jpg</image:loc>
      <image:title>Electromagnetism - Electric Flux</image:title>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/electromagnetism/2017/6/20/derivation-of-guasss-law-from-columns-law</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-09</lastmod>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59dc41027131a52388a3d5dc/1507606793199/electromagnetism+thumbnaillllll+imageeee.jpg</image:loc>
      <image:title>Electromagnetism - Derivation of Guass's Law from Column's Law</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5983b6ff1e5b6c1be89f919b/1504719682344/</image:loc>
      <image:title>Electromagnetism - Derivation of Guass's Law from Column's Law</image:title>
      <image:caption>Figure 2 (click to enlarge)</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5983af90ebbd1ab6e030c458/1504719682340/guass.jpg</image:loc>
      <image:title>Electromagnetism - Derivation of Guass's Law from Column's Law</image:title>
      <image:caption>Figure 1 (click to enlarge)</image:caption>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/electromagnetism/2017/7/20/using-guasss-law-to-find-the-electric-field-produced-by-a-single-point-charge</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-09</lastmod>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5983ba441e5b6c1be89fc0fe/1504719696428/</image:loc>
      <image:title>Electromagnetism - Using Guass's Law to find the Electric Field Produced by a Single Point Charge</image:title>
      <image:caption>Figure 2</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5983c1f2f7e0ab6f61d65054/1504719696432/</image:loc>
      <image:title>Electromagnetism - Using Guass's Law to find the Electric Field Produced by a Single Point Charge</image:title>
      <image:caption>Figure 3</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59dc41392994ca84b39c5432/1507606855719/electromagnetism+thumbnaillllll+imageeee.jpg</image:loc>
      <image:title>Electromagnetism - Using Guass's Law to find the Electric Field Produced by a Single Point Charge</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5983b8899f745676d8a84980/1504719696421/guass.jpg</image:loc>
      <image:title>Electromagnetism - Using Guass's Law to find the Electric Field Produced by a Single Point Charge</image:title>
      <image:caption>Figure 1</image:caption>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/special-relativity</loc>
    <changefreq>daily</changefreq>
    <priority>0.75</priority>
    <lastmod>2017-09-06</lastmod>
  </url>
  <url>
    <loc>https://www.gregschool.org/special-relativity/2017/5/14/introduction-to-special-relativity</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-09</lastmod>
  </url>
  <url>
    <loc>https://www.gregschool.org/special-relativity/2017/5/14/8c5knwf9nztiio7uwnvvotz1pj86ht</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-09</lastmod>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/598d0d3ea803bb1ee4694f07/1504673327843/</image:loc>
      <image:title>Special Relativity - Time Dilation</image:title>
      <image:caption>Figure 1</image:caption>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/cosmology</loc>
    <changefreq>daily</changefreq>
    <priority>0.75</priority>
    <lastmod>2017-11-08</lastmod>
  </url>
  <url>
    <loc>https://www.gregschool.org/cosmology/2017/5/14/dark-matter</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-11</lastmod>
  </url>
  <url>
    <loc>https://www.gregschool.org/cosmology/2017/5/14/bentleys-and-olbers-paradoxes</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-10</lastmod>
  </url>
  <url>
    <loc>https://www.gregschool.org/cosmology/2017/5/14/cosmic-microwave-background-radiation</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-11</lastmod>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59193ff4893fc0567ac5bcf7/1504672850810/</image:loc>
      <image:title>Cosmology - Cosmic Microwave Background Radiation</image:title>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/cosmology/2017/5/14/surface-of-last-scattering</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-11</lastmod>
  </url>
  <url>
    <loc>https://www.gregschool.org/cosmology/2017/5/14/dark-energy</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-11</lastmod>
  </url>
  <url>
    <loc>https://www.gregschool.org/cosmology/2017/5/14/friedman-robertson-walker-frw-equation</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-11</lastmod>
  </url>
  <url>
    <loc>https://www.gregschool.org/cosmology/2017/5/14/spectroscopy</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-11</lastmod>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59194323be659485a8d5abe4/1504672500784/</image:loc>
      <image:title>Cosmology - Spectroscopy</image:title>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/cosmology/2017/5/14/xe30zrw2tke0y051q8xdpf9cxaff19</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-11</lastmod>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5919442515cf7d45e9761c26/1504672412824/</image:loc>
      <image:title>Cosmology - Scaling Factor, Hubble's Parameter, and the Age of the Universe</image:title>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/cosmology/2017/5/23/g76bh7ssk8up16r4w2ptuwsm37kpho</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-06</lastmod>
  </url>
  <url>
    <loc>https://www.gregschool.org/cosmology/2017/5/14/solving-the-frw-equation-for-the-scaling-factor-in-different-scenarios-hdsrg-x7nsb</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-09</lastmod>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a007a5c8165f5ff004353ad/1509937688558/AT_7e_Figure_27_01%5B2%5D.jpg</image:loc>
      <image:title>Cosmology - Solving the FRW Equation for the Scaling Factor in different scenarios</image:title>
      <image:caption>Figure 1: As you can see from the graph above, for the first roughly 10,000 years most of the energy density in the universe was due to the presence of radiation. During the time interval from when the universe was 10,000 years old to when it was several billion years old, the energy density of the universe was dominated by matter. In our present epoch, the energy density of the universe is dominated by dark energy (or vacuum energy). This graph has profound implications. As time progresses, dark energy will become more and more dominant and will remain the dominant source of energy in the universe; since dark energy causes everything in the universe to expand, the universe will continue to expand without ever stopping. This graph, essentially, implies the ultimate fate of the universe. The universe will continue to expand more and more until it becomes dark, empty, and lifeless.</image:caption>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/cosmology/2017/5/14/genesis-of-the-elements-xz53h-yww35</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-09</lastmod>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a032d3b24a69487b355d17d/1509985102690/</image:loc>
      <image:title>Cosmology - Genesis of the Elements</image:title>
      <image:caption>Figure 3: The Alpha-Beta-Gamma paper demonstrated that after the first roughly three minutes of the universe since its initial Bang, hydrogen and helium nuclei were synthesized via nuclear fusion. After about three minutes, the universe cooled enough for fusion to stop; but the universe was still so hot that all of the matter comprising the universe was a plasma and plasma's are opaque to radiation. The matter comprising the universe was in a plasma state for the first roughly 300,000 years since the Big Bang; since plasma is opaque to radiation, for the first roughly 300,000 years light could not freely travel throughout the universe without constantly "bumping into stuff (atomic nuclei)." At sometime when the universe was about 300,000 to 400,000 years old, matter cooled enough for electrons to bind to atomic nuclei and for light to freely pass through the universe. Due to the expansion of space, Alpher and Herman estimated that wavelengths of this light should now be stretched into the microwave region.</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a032d3b24a69487b355d17b/1509983399387/nuclear-fusion-stars%5B1%5D.png</image:loc>
      <image:title>Cosmology - Genesis of the Elements</image:title>
      <image:caption>Figure 2: All stars in the universe generate light and energy by fusing lighter elements into heavier elements. For stars up to the mass of about that of our Sun, light and energy is created by fusing hydrogen into helium. The image above illustrates the chain of nuclear reactions which occur in small to medium sized stars and very massive stars that allow them to generate light and energy. Stellar fusion accounts for where many of the light to medium-sized elements in the periodic table come from.</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a032d3b24a69487b355d179/1509981827221/RutherfordGoilFoil+%281%29%5B1%5D.jpg</image:loc>
      <image:title>Cosmology - Genesis of the Elements</image:title>
      <image:caption>Figure 1: Rutherford's experiment involved putting a radioactive element known as radium inside of a lead box. The radium spontaneously emitted \(α\) particles in a narrow beam through a small hole in the box. These \(α\) particles were directed towards a gold foil. Most \(α\) particles passed straight through the gold foil but occasional one would get reflected back at an acute angle with the beam of \(α\) particles. This meant that atoms must have tiny, but very dense, nuclei. Image credit: http://m.teachastronomy.com/astropedia/article/The-Structure-of-the-Atom</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a032d3b24a69487b355d17f/1509987202844/</image:loc>
      <image:title>Cosmology - Genesis of the Elements</image:title>
      <image:caption>Figure 4: As a star undergoes nuclear fusion in its core, it generates light. This light exerts an outward radiation pressure on the star which balances the inward gravitational forces that tend to pull the star's matter towards its center. But at the end of a star's life, nuclear fusion begins to slow down and eventually stop; this means that there is no outward radiation pressure to balance the gravitational forces exerted on the outward layers of the star and star eventually collapses. If the star is very massive, such a collapse will result in one of the most spectacular events in the universe: a supernova. The energy generated by a supernova explosion is so stupendous that it results in nuclear reactions which create the heavier elements in the period table.</image:caption>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/quantum-mechanics</loc>
    <changefreq>daily</changefreq>
    <priority>0.75</priority>
    <lastmod>2017-11-08</lastmod>
  </url>
  <url>
    <loc>https://www.gregschool.org/quantum-mechanics/2017/5/14/quantum-dynamics</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-11</lastmod>
  </url>
  <url>
    <loc>https://www.gregschool.org/quantum-mechanics/2017/5/14/how-initial-states-of-definite-energy-change-with-time</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-11</lastmod>
  </url>
  <url>
    <loc>https://www.gregschool.org/quantum-mechanics/2017/5/15/particle-in-one-dimensional-box</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-09</lastmod>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/592479e7c534a50553d99559/1504671394203/sch.png</image:loc>
      <image:title>Schrodinger's Equation - Time-Independant Schrodinger Equation: Free Particle and Particle in One-Dimensional Box</image:title>
      <image:caption>Figure 2 (click to expand): The probability amplitude of measuring the particle at a position \(x\) in the presence of a potential \(V_0\) decreases exponentially with increasing \(V_0\).</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/591952af1b10e3f7ad2c98e2/1504671394205/</image:loc>
      <image:title>Schrodinger's Equation - Time-Independant Schrodinger Equation: Free Particle and Particle in One-Dimensional Box</image:title>
      <image:caption>Figure 3 (click to expand): Illustration of a free particle moving in a one-dimensional box which is "pinned down" by a finite well. The probability amplitude of finding the particle outside of the box decreases exponentially as a function of distance.</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/592354ce6b8f5b37844cd500/1504671394207/</image:loc>
      <image:title>Schrodinger's Equation - Time-Independant Schrodinger Equation: Free Particle and Particle in One-Dimensional Box</image:title>
      <image:caption>Figure 4: Illustration shows the allowed energy levels of a particle trapped inside of a one-dimensional box.</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/592351e99de4bb9c550b497d/1504671394201/kjkjnj.png</image:loc>
      <image:title>Schrodinger's Equation - Time-Independant Schrodinger Equation: Free Particle and Particle in One-Dimensional Box</image:title>
      <image:caption>Figure 1 (click to expand): Illustration of a free particle moving in a "one-dimensional box" which is trapped inside of an infinite potential well.</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59234aac03596ed573bce9ab/1504671394198/</image:loc>
      <image:title>Schrodinger's Equation - Time-Independant Schrodinger Equation: Free Particle and Particle in One-Dimensional Box</image:title>
      <image:caption>"A wave function that satisfies the nonrelativistic Schrödinger equation with V = 0. In other words, this corresponds to a particle traveling freely through empty space. The real part of the wave function is plotted here."\(^{[1]}\)</image:caption>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/quantum-mechanics/2017/5/15/time-evolution-of-state-vectors</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-09</lastmod>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a026d3bf9619a62ab661666/1510108644648/photon_double_slit2%5B1%5D.gif</image:loc>
      <image:title>Schrodinger's Equation - Schrodinger's Time-Dependent Equation: Time-Evolution of State Vectors</image:title>
      <image:caption>Figure 2: Schrodinger's equation is deterministic because the past or future quantum state \(|\psi(t)⟩\) of a quantum system can be determined with infinite precision. But, in general, a quantum system can be in a superposition of many different states where the measurement of any physical quantity is uncertain. For example, if anything the size of a small molecule or smaller passes through a double-slit in a double-slit experiment, where it hits the screen (which is to say, its final position) is uncertain (see illustration above). The quantum state of a quantum system is deterministic; but the eigenvalue that you'll measure after an experiment is done is the quantity which is not deterministic in quantum mechanics. Source: http://abyss.uoregon.edu/~js/21st_century_science/lectures/lec13.html</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a0267fc652dea4ceb34e37d/1510108644645/1_Lwu5UJMmcuFVJLZ1Ln4E0Q%5B1%5D.png</image:loc>
      <image:title>Schrodinger's Equation - Schrodinger's Time-Dependent Equation: Time-Evolution of State Vectors</image:title>
      <image:caption>Figure 1: The motion of a simple pendulum is an example of the time-reversibility of Newton's second law. Given the initial state of the pendulum, Newton's second law can be used to determine the past or future state of the system. For example, one could determine the velocity and position of the pendulum at any past or future time given its present state.</image:caption>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/quantum-mechanics/2017/5/15/periodic-wavefunctions-that-is-ones-that-come-back-to-themselves-have-quantized-eigenvalues-of-momenta-and-angular-momenta-2k3el-yckar</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-09</lastmod>
  </url>
  <url>
    <loc>https://www.gregschool.org/lagrangian-mechanics</loc>
    <changefreq>daily</changefreq>
    <priority>0.75</priority>
    <lastmod>2017-09-06</lastmod>
  </url>
  <url>
    <loc>https://www.gregschool.org/lagrangian-mechanics/2017/5/18/v7t2klwmycopiblvbhzkhyw2duujqy</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-09</lastmod>
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      <image:title>Lagrangian Mechanics - Introduction to Lagrangian Mechanics</image:title>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/lagrangian-mechanics/2017/5/18/derivation-of-the-euler-lagrange-equation</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-09</lastmod>
    <image:image>
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      <image:title>Lagrangian Mechanics - Derivation of the Euler-Lagrange Equation</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59207875a5790a9f652af8b8/1504719745581/</image:loc>
      <image:title>Lagrangian Mechanics - Derivation of the Euler-Lagrange Equation</image:title>
      <image:caption>Figure 1 (click to expand)</image:caption>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/lagrangian-mechanics/2017/5/18/finding-the-geodesic-on-a-cylinder</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2019-02-22</lastmod>
    <image:image>
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      <image:title>Lagrangian Mechanics - Finding the geodesic on a cylinder</image:title>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/lagrangian-mechanics/2017/5/18/brachistochrone-problem</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-09</lastmod>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5920889cbe659438f080cba9/1504719809377/</image:loc>
      <image:title>Lagrangian Mechanics - Brachistochrone problem</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/592088d1cd0f6872c792b474/1504719809380/</image:loc>
      <image:title>Lagrangian Mechanics - Brachistochrone problem</image:title>
      <image:caption>Credit\(^{[3]}\)</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5920887d6a49635fddd51175/1504719809373/</image:loc>
      <image:title>Lagrangian Mechanics - Brachistochrone problem</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59dbfa1751a58476eaac9b16/1507588635069/gfnf.jpg</image:loc>
      <image:title>Lagrangian Mechanics - Brachistochrone problem</image:title>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/lagrangian-mechanics/2017/5/18/generalized-coordinates</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-09</lastmod>
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      <image:title>Lagrangian Mechanics - Generalized coordinates</image:title>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/lagrangian-mechanics/2017/5/18/noethers-theorem</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-09</lastmod>
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      <image:title>Lagrangian Mechanics - Noether’s Theorem</image:title>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/schrodingers-equation-1</loc>
    <changefreq>daily</changefreq>
    <priority>0.75</priority>
    <lastmod>2017-11-08</lastmod>
  </url>
  <url>
    <loc>https://www.gregschool.org/schrodingers-equation-1/2017/5/23/math-interlude</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-11</lastmod>
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      <image:title>Introduction to Matrix Mechanics - Quantum Mechanics: Math Interlude</image:title>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/schrodingers-equation-1/2017/5/23/pauli-matrices</loc>
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    <priority>0.5</priority>
    <lastmod>2017-11-11</lastmod>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59dc4cd0f7e0ab3dbb237c96/1507609811147/electromagnetism+thumbnaillllll+imageeee.jpg</image:loc>
      <image:title>Introduction to Matrix Mechanics - Pauli Matrices</image:title>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/schrodingers-equation-1/2017/5/23/measuring-the-spin-of-an-electron</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-11</lastmod>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59dc4ca951a58476eab05ece/1507609773311/electromagnetism+thumbnaillllll+imageeee.jpg</image:loc>
      <image:title>Introduction to Matrix Mechanics - Measuring the Spin of an Electron</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/592483b1be6594a48944dd65/1504671946323/</image:loc>
      <image:title>Introduction to Matrix Mechanics - Measuring the Spin of an Electron</image:title>
      <image:caption>Figure 1</image:caption>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/schrodingers-equation-1/2017/5/23/the-eigenvalues-of-any-observable-hatl-must-be-real</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-11</lastmod>
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      <image:title>Introduction to Matrix Mechanics - The Eigenvalues of any Observable \(\hat{L}\) must be Real</image:title>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/schrodingers-equation-1/2017/5/23/fundamental-principles-and-postulates-of-quantum-mechanics</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-11</lastmod>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59dc4c10d2b857fa05900fea/1507609620648/electromagnetism+thumbnaillllll+imageeee.jpg</image:loc>
      <image:title>Introduction to Matrix Mechanics - Fundamental Principles and Postulates of Quantum Mechanics</image:title>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/schrodingers-equation-1/2017/5/23/calculating-the-wavefunction-collection-of-probability-amplitudes-associated-with-any-ket-vector-skh4m</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-09</lastmod>
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      <image:title>Introduction to Matrix Mechanics - Calculating the Wavefunction Associated with any Ket Vector</image:title>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/schrodingers-equation-1/2017/5/23/the-eigenvectors-of-any-hermitian-operator-must-be-orthogonal-w2jps-sthp6</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-09</lastmod>
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      <image:title>Introduction to Matrix Mechanics - The Eigenvectors of any Hermitian Operator must be Orthogonal</image:title>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/cosmology2</loc>
    <changefreq>daily</changefreq>
    <priority>0.75</priority>
    <lastmod>2017-09-06</lastmod>
  </url>
  <url>
    <loc>https://www.gregschool.org/cosmology2/2017/5/27/origin-of-structure-and-clumpyness</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-11</lastmod>
  </url>
  <url>
    <loc>https://www.gregschool.org/new-blog-2</loc>
    <changefreq>daily</changefreq>
    <priority>0.75</priority>
    <lastmod>2019-03-23</lastmod>
  </url>
  <url>
    <loc>https://www.gregschool.org/new-blog-2/2017/9/25/colonizing-and-terraforming-venus-59y59</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2018-04-08</lastmod>
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      <image:title>Articles Page 2 - Colonizing and Terraforming Venus</image:title>
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      <image:title>Articles Page 2 - Colonizing and Terraforming Venus</image:title>
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      <image:title>Articles Page 2 - Colonizing and Terraforming Venus</image:title>
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      <image:title>Articles Page 2 - Colonizing and Terraforming Venus</image:title>
      <image:caption>Artist concept of lightning on Venus. Image credit: ESA</image:caption>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5ac95be42b6a289d089bfe07/1507060053549/venus-cloud-city.jpg</image:loc>
      <image:title>Articles Page 2 - Colonizing and Terraforming Venus</image:title>
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      <image:title>Articles Page 2 - Colonizing and Terraforming Venus</image:title>
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      <image:title>Articles Page 2 - Colonizing and Terraforming Venus</image:title>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5ac95be42b6a289d089bfe09/1510882341344/TerraformedVenus%5B1%5D.jpg</image:loc>
      <image:title>Articles Page 2 - Colonizing and Terraforming Venus</image:title>
      <image:caption>"A conceptual picture I made of Venus if it were terraformed. (Credit: Daein Ballard) Notice the interesting cloud formations and that the planet has polar caps. I decided to show the planet this way after studying Venus' atmosphere. The two Hadley cells the planet has stop at 70 degrees north and south. So the polar regions are cut off from the warm air. Also the slow rotation of the planet causes the clouds to whip around the planet very fast, especially at the equator, to balance out the temperature difference between day and night sides of the planet."\(^{[5]}\) Image credit: Ittiz at the English language Wikipedia [GFDL (http://www.gnu.org/copyleft/fdl.html) or CC-BY-SA-3.0 (http://creativecommons.org/licenses/by-sa/3.0/)], via Wikimedia Commons</image:caption>
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      <image:title>Articles Page 2 - Colonizing and Terraforming Venus</image:title>
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  </url>
  <url>
    <loc>https://www.gregschool.org/new-blog-2/2017/11/2/gravitational-force-exerted-by-a-rod-zf4pf</loc>
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    <priority>0.5</priority>
    <lastmod>2018-04-09</lastmod>
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      <image:title>Articles Page 2 - Gravitational Force Exerted by a Rod</image:title>
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      <image:title>Articles Page 2 - Gravitational Force Exerted by a Rod</image:title>
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      <image:title>Articles Page 2 - Gravitational Force Exerted by a Rod</image:title>
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      <image:title>Articles Page 2 - Gravitational Force Exerted by a Rod</image:title>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5acb886a8a922dc773e2f7e9/1509666905146/rod.png</image:loc>
      <image:title>Articles Page 2 - Gravitational Force Exerted by a Rod</image:title>
      <image:caption>Figure 1: A rod of mass \(M\) and a particle of mass \(m\) are separated from each other by a distance of \(d\) along the \(x\)-axis. Each mass element \(dm\) comprising the rod is located at some position \(x\) along the \(x\)-axis and is separated from the particle \(m\) by some amount \(r\). By summing all the gravitational forces \(d\vec{F}_g\) exerted by each mass element \(dm\) comprising the rod, we can find the total gravitational force exerted on \(m\) by the entire rod.</image:caption>
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      <image:title>Articles Page 2 - Gravitational Force Exerted by a Rod</image:title>
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      <image:title>Articles Page 2 - Gravitational Force Exerted by a Rod</image:title>
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  </url>
  <url>
    <loc>https://www.gregschool.org/new-blog-2/2018/6/12/01kbzrqg971y7cr7mw0lgnob5i1y43</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2018-07-19</lastmod>
  </url>
  <url>
    <loc>https://www.gregschool.org/new-blog-2/2017/11/14/drakes-equation-d4hkm</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2018-07-19</lastmod>
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      <image:title>Articles Page 2 - Drake's Equation and Searching for Life in the Milky Way</image:title>
      <image:caption>"Mr. Spock (Leonard Nimoy), communicating with the Horta through a Vulcan mind meld."\(^{[3]}\)</image:caption>
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      <image:caption>An artist's depiction of the starship proposed by Project Daedalus.\(^{[5]}\)</image:caption>
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      <image:title>Articles Page 2 - Drake's Equation and Searching for Life in the Milky Way</image:title>
      <image:caption>Artist's depiction of an exoplanet orbiting a pulsar. Due to the pulsar's radiation, the exoplanet glows.</image:caption>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/5b5117cc1ae6cfef2ad2178d/5b5117cc1ae6cfef2ad21792/1510878250166/20131102_cosmos-episode-2-hfs-herd-of-floaters%5B1%5D.jpg</image:loc>
      <image:title>Articles Page 2 - Drake's Equation and Searching for Life in the Milky Way</image:title>
      <image:caption>A Lazy Herd of Floaters "An updated digital restoration by Adolf Schaller of detail in his original Hunters, Floaters, Sinkers mural which appeared on Cosmos, Episode 2, which speculates about life in the atmosphere of a gas-giant planet."\(^{[4]}\) Image by Adolf Schaller.</image:caption>
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      <image:title>Articles Page 2 - Drake's Equation and Searching for Life in the Milky Way</image:title>
      <image:caption>Hunters, Floaters, and Sinkers "This painting speculates about possible forms of life on a Jupiter-like gas giant. Airbrushed water-based acrylic."\(^{[4]}\) Image by Adolf Schaller.</image:caption>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/5b5117cc1ae6cfef2ad2178d/5b5117cc1ae6cfef2ad21794/1510878262303/20131102_cosmos-episode-2-hfs-a-hunter-close-up%5B1%5D.jpg</image:loc>
      <image:title>Articles Page 2 - Drake's Equation and Searching for Life in the Milky Way</image:title>
      <image:caption>A Hunter "A speculative hunter animal evolved in the atmosphere of a gas-giant planet. Developed for Cosmos, Episode 2."\(^{[4]}\) Image by Adolf Schaller.</image:caption>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/5b5117cc1ae6cfef2ad2178d/5b5117cc1ae6cfef2ad21790/1510878236692/20131102_cosmos-episode-2-hfs-floater-close-up%5B1%5D.jpg</image:loc>
      <image:title>Articles Page 2 - Drake's Equation and Searching for Life in the Milky Way</image:title>
      <image:caption>A "Floater" from Cosmos, Episode 2 "Part of the larger mural, "Hunters, Floaters, and Sinkers" painted for the series."\(^{[4]}\) Image by Adolf Schaller.</image:caption>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5b5117cc1ae6cfef2ad2179d/1510868724096/Heic0612b_H%5B1%5D.jpg</image:loc>
      <image:title>Articles Page 2 - Drake's Equation and Searching for Life in the Milky Way</image:title>
      <image:caption>Artist's depiction of an exoplanet crossing our line of sight in front of its home-star.</image:caption>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5b5117cc1ae6cfef2ad21799/1510874187182/Habitable-zone%5B1%5D.jpg</image:loc>
      <image:title>Articles Page 2 - Drake's Equation and Searching for Life in the Milky Way</image:title>
      <image:caption>The habitable zone is a range of orbital distances (between an exoplanet and the star it orbits) where the planet is neither too hot nor too cold. This is also sometimes called the Goldilocks zone. In order for a planet to be truly "Earth-like," it must also have a mass 1-2 times that of the Earth, have an atmosphere, and orbit in a stable elliptical orbit that is not too essentric.</image:caption>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/5b5117cc1ae6cfef2ad2179f/5b5117cc1ae6cfef2ad217a2/1510875294374/HT-trappist-1-star-surface-3-jt-170221_4x3_992%5B1%5D.jpg</image:loc>
      <image:title>Articles Page 2 - Drake's Equation and Searching for Life in the Milky Way</image:title>
      <image:caption>Imagine standing on the surface of the exoplanet TRAPPIST-1f. This artist's concept is one interpretation of what it could look like.</image:caption>
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    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/5b5117cc1ae6cfef2ad2179f/5b5117cc1ae6cfef2ad217a0/1510875160635/proximasurface%5B1%5D.jpg</image:loc>
      <image:title>Articles Page 2 - Drake's Equation and Searching for Life in the Milky Way</image:title>
      <image:caption>"This artist’s impression shows a view of the surface of the planet Proxima b orbiting the red dwarf star Proxima Centauri, the closest star to the solar system. The double star Alpha Centauri AB also appears in the image. Proxima b is a little more massive than the Earth and orbits in the habitable zone around Proxima Centauri, where the temperature is suitable for liquid water to exist on its surface."\(^{[1]}\) https://www.nasa.gov/feature/jpl/eso-discovers-earth-size-planet-in-habitable-zone-of-nearest-star Credits: ESO/M. Kornmesser</image:caption>
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      <image:title>Articles Page 2 - Drake's Equation and Searching for Life in the Milky Way</image:title>
      <image:caption>Artist's depiction of the Kepler space telescope.</image:caption>
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  </url>
  <url>
    <loc>https://www.gregschool.org/new-blog-2/2017/9/24/introduction-to-double-integrals-1-9ekxy-2wbc7</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2018-04-08</lastmod>
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      <image:title>Articles Page 2 - Introduction to Double Integrals</image:title>
      <image:caption>Figure 1: When we were deriving an expression for the definite integral in terms of the Riemann sum, we first approximated the area underneath \(f(x)\) by summing the areas of many very skinny rectangles as illustrated in (A). To define a double integral in terms of a Riemann sum, we first approximate the volume underneath a surface by summing the volumes of many very skinny columns as depicted in (C). The width and depth of each column is given by \(Δx\) and \(Δy\) and the height of each rectangle is given by the surface \(f(x,y)\) as shown in (B).</image:caption>
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      <image:title>Articles Page 2 - Introduction to Double Integrals</image:title>
      <image:caption>Figure 2: The volume underneath the surface \(f(x,y)\) can be approximated by summing the volumes of an \(nm\) number of columns underneath the surface. As these columns become infinitesimally skinny and as the number \(nm\) of them approaches infinity, this sum gives the exact volume underneath the surface \(f(x,y)\).</image:caption>
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  </url>
  <url>
    <loc>https://www.gregschool.org/new-blog-2/2017/10/30/gravitational-force-exerted-by-a-sphere-rdyjt</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2018-09-14</lastmod>
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      <image:title>Articles Page 2 - Gravitational Force Exerted by a Sphere</image:title>
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      <image:title>Articles Page 2 - Gravitational Force Exerted by a Sphere</image:title>
      <image:caption>Figure 1: A shell can be subdivided into many very skinny rings. Anyone of these rings can be represented by the ring \(QRR_1Q_1\) illustrated above. Image credit\(^{[1]}\).</image:caption>
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      <image:title>Articles Page 2 - Gravitational Force Exerted by a Sphere</image:title>
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      <image:title>Articles Page 2 - Gravitational Force Exerted by a Sphere</image:title>
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      <image:title>Articles Page 2 - Gravitational Force Exerted by a Sphere</image:title>
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      <image:title>Articles Page 2 - Gravitational Force Exerted by a Sphere</image:title>
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  </url>
  <url>
    <loc>https://www.gregschool.org/new-blog-2/2017/9/30/proof-of-greens-theorem-4kbde</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2018-06-28</lastmod>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5b34709caa4a993c621b4aee/1530156044345/share+calculus+img.png</image:loc>
      <image:title>Articles Page 2 - Proof of Green's Theorem</image:title>
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      <image:title>Articles Page 2 - Proof of Green's Theorem</image:title>
      <image:caption>Figure 3: We can break up the curve \(c\) into the two separate curves, \(c_1\) and \(c_2\). This also allows us to break up the function \(x(y)\) into the two separate functions, \(x(y_1)\) and \(x(y_2)\).</image:caption>
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      <image:title>Articles Page 2 - Proof of Green's Theorem</image:title>
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      <image:title>Articles Page 2 - Proof of Green's Theorem</image:title>
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      <image:title>Articles Page 2 - Proof of Green's Theorem</image:title>
      <image:caption>Figure 2: We can split the curve \(c\) into two separate curves, \(c_1\) and \(c_2\). This also allows us to split the function \(y(x)\) into the two separate functions, \(y(x_1)\) and \(y(x_2)\).</image:caption>
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      <image:title>Articles Page 2 - Proof of Green's Theorem</image:title>
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      <image:title>Articles Page 2 - Proof of Green's Theorem</image:title>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5b34709caa4a993c621b4afa/1506810526998/429px-Green%27s-theorem-simple-region.svg.png</image:loc>
      <image:title>Articles Page 2 - Proof of Green's Theorem</image:title>
      <image:caption>Figure 1: The curve \(C=C_1+C_2+C_3+C_4\) is piece-wise smooth. It is "piece-wise" because it is split up into an \(n=4\) number of separate curves with an \(n=4\) number of "edges." It is "smooth" because each individual curve itself is smooth without any sharp edges or cusps. This curve is also positively-oriented because its direction goes counter-clockwise. Image by Cronholm 144.</image:caption>
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      <image:title>Articles Page 2 - Proof of Green's Theorem</image:title>
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  </url>
  <url>
    <loc>https://www.gregschool.org/new-blog-2/2018/6/20/the-diversity-of-exoplanets-in-the-galaxy-me459</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2018-07-19</lastmod>
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      <image:title>Articles Page 2 - The Diversity of Exoplanets in the Galaxy</image:title>
      <image:caption>Image of auroras just above the Earth's surface obtained by the International Space Station. Image credit: NASA</image:caption>
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      <image:title>Articles Page 2 - The Diversity of Exoplanets in the Galaxy</image:title>
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      <image:title>Articles Page 2 - The Diversity of Exoplanets in the Galaxy</image:title>
      <image:caption>Artists impressions of subsurface oceans underneath thick ice sheets on Jupiter’s moon Europa and Saturn’s moon Enceladus. Top image by NASA.</image:caption>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5b51175f758d46a40f4dd223/1530236766508/Graphite-and-diamond-with-scale%5B1%5D.jpg</image:loc>
      <image:title>Articles Page 2 - The Diversity of Exoplanets in the Galaxy</image:title>
      <image:caption>Graphite (left) and diamond (right) are both, essentially, just made up of a bunch of carbon atoms. The difference between the two substances is how those carbon atoms are arranged.</image:caption>
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      <image:title>Articles Page 2 - The Diversity of Exoplanets in the Galaxy</image:title>
      <image:caption>Artist's impression of the Archipelago world, Kepler 186f. Credit: Danielle Futselaar</image:caption>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5b51175f758d46a40f4dd22f/1530743975575/trappist.png</image:loc>
      <image:title>Articles Page 2 - The Diversity of Exoplanets in the Galaxy</image:title>
      <image:caption>This artist's concept shows what the TRAPPIST-1 planetary system may look like, based on available data about the planets' diameters, masses and distances from the host star. Credits: NASA/JPL-Caltech View full image and caption</image:caption>
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      <image:title>Articles Page 2 - The Diversity of Exoplanets in the Galaxy</image:title>
      <image:caption>X-ray image of Pluto obtained by Chandra X-Ray Observatory (blue spot on right) and up-close photograph of Pluto obtained by the spacecraft Deep Horizons as it flew by Pluto.</image:caption>
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      <image:title>Articles Page 2 - The Diversity of Exoplanets in the Galaxy</image:title>
      <image:caption>Artist's depiction of the exoplanet 55 Cancri E. Image credit: ESA/Hubble [CC BY 4.0 (https://creativecommons.org/licenses/by/4.0)], via Wikimedia Commons.</image:caption>
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      <image:title>Articles Page 2 - The Diversity of Exoplanets in the Galaxy</image:title>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5b51175f758d46a40f4dd21f/1530132981476/Planets_everywhere_%28artist%E2%80%99s_impression%29%5B1%5D.jpg</image:loc>
      <image:title>Articles Page 2 - The Diversity of Exoplanets in the Galaxy</image:title>
      <image:caption>"This artist's cartoon view gives an impression of how common planets are around the stars in the Milky Way. The planets, their orbits and their host stars are all vastly magnified compared to their real separations. A six-year search that surveyed millions of stars using the microlensing technique concluded that planets around stars are the rule rather than the exception. The average number of planets per star is greater than one."\(^{[1]}\) Image credit: by ESO/M. Kornmesser (http://www.eso.org/public/images/eso1204a/) [CC BY 4.0 (https://creativecommons.org/licenses/by/4.0)], via Wikimedia Commons</image:caption>
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      <image:title>Articles Page 2 - The Diversity of Exoplanets in the Galaxy</image:title>
      <image:caption>This poster imagines what a trip to TRAPPIST-1e might be like. Credits: NASA/JPL-Caltech View full image</image:caption>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5b51175f758d46a40f4dd229/1530047402295/1920px-Kepler186f-ComparisonGraphic-20140417%5B1%5D.jpg</image:loc>
      <image:title>Articles Page 2 - The Diversity of Exoplanets in the Galaxy</image:title>
      <image:caption>Size comparison of Kepler-186f (artist's impression) with Earth along with their projected habitable zones.</image:caption>
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      <image:title>Articles Page 2 - The Diversity of Exoplanets in the Galaxy</image:title>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5b51175f758d46a40f4dd21d/1529888319405/aHR0cDovL3d3dy5zcGFjZS5jb20vaW1hZ2VzL2kvMDAwLzA2Mi8wODkvb3JpZ2luYWwvaG90LWp1cGl0ZXItY29uY2VwdGlvbi5qcGc%3D%5B1%5D.jpg</image:loc>
      <image:title>Articles Page 2 - The Diversity of Exoplanets in the Galaxy</image:title>
      <image:caption>Artist's depiction of a so-called hot Jupiter orbiting its planet star.</image:caption>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5b51175f758d46a40f4dd21b/1531436786142/pular+planet.png</image:loc>
      <image:title>Articles Page 2 - The Diversity of Exoplanets in the Galaxy</image:title>
      <image:caption>Artist's conception of a planet orbiting a Pulsar. The Pulsar's radiation blasting the exoplanet would cause its surface to glow.</image:caption>
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  </url>
  <url>
    <loc>https://www.gregschool.org/new-blog-2/2018/7/20/space-based-solar-power-3ptal-jreey-fh4ws</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2018-09-18</lastmod>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/5b8b4e4b40ec9a2651daf4ae/5b8b4e4b40ec9a2651daf4b1/1535827901771/hades__star___warp_lane_hub_by_gabriel_bs-db8y989.png</image:loc>
      <image:title>Articles Page 2 - Orbital Rings and Planet Building: Prelude to Colonizing the Solar System</image:title>
      <image:caption>“Two hubs that can connect to create a temporary Warp Lane in your system The Warp Lane Hub can be connected to another Hub for one day, for a fixed Hydrogen cost. Once connected, ships can travel between the two end points instantly and without consuming Hydrogen.”\(^{[31]}\) Image credit: https://www.deviantart.com/gabrielbstiernstrom/art/Hades-Star-Warp-Lane-Hub-680163129</image:caption>
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      <image:title>Articles Page 2 - Orbital Rings and Planet Building: Prelude to Colonizing the Solar System</image:title>
      <image:caption>Artist’s scifi depiction of a galactic empire using portals to travel across space.\(^{[30]}\) Image credit: https://www.deviantart.com/lorddoomhammer/art/Galactic-Network-594726702</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5b8b4e4b40ec9a2651daf40c/1535354571685/img_index_01.jpg</image:loc>
      <image:title>Articles Page 2 - Orbital Rings and Planet Building: Prelude to Colonizing the Solar System</image:title>
      <image:caption>"Since ancient times, people have always dreamed of going to space. Only astronauts have been able to go until now, but progress has been made on efforts to enable even private citizens to experience space, and space travel is finally about to become an industry. Shimizu foresaw the era of space travel early on, and has proposed a space hotel concept."\(^{[4]}\)</image:caption>
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      <image:title>Articles Page 2 - Orbital Rings and Planet Building: Prelude to Colonizing the Solar System</image:title>
      <image:caption>Artist’s depiction of hoop worlds (also known as ring worlds). These megastructures can be built by building many adjacent orbital rings next to each other, side by side, and laying a surface down over those orbital rings. Image retrieved from https://www.iamag.co/espen-olsen-saetervik/espen-saetervik-rings/</image:caption>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/5b8b4e4b40ec9a2651daf44a/5b8b4e4b40ec9a2651daf44b/1535827690138/earthring_1024.jpg</image:loc>
      <image:title>Articles Page 2 - Orbital Rings and Planet Building: Prelude to Colonizing the Solar System</image:title>
      <image:caption>Artist’s depiction of an orbital ring which appeared in Issue 7 of the magazine, All About Space. Image by Adrian Mann.\(^{[18]}\)</image:caption>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5b8b4e4b40ec9a2651daf448/1535355196399/Kohlenstoffnanoroehre_Animation.gif</image:loc>
      <image:title>Articles Page 2 - Orbital Rings and Planet Building: Prelude to Colonizing the Solar System</image:title>
      <image:caption>Animation of a sheet of pure graphene rolled up into a carbon nanotube. Credit: https://commons.wikimedia.org/wiki/File:Kohlenstoffnanoroehre_Animation.gif</image:caption>
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      <image:title>Articles Page 2 - Orbital Rings and Planet Building: Prelude to Colonizing the Solar System</image:title>
      <image:caption>Image above portrays Nikola Tesla, the famous inventor who first conceived of the notion of orbital rings in the 1870s shortly after recovering from malaria.</image:caption>
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      <image:caption>Artist's conception of the Kepler Space Telescope.</image:caption>
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      <image:title>Articles Page 2 - Orbital Rings and Planet Building: Prelude to Colonizing the Solar System</image:title>
      <image:caption>Artist's illustration of a hypothetical ocean planet with two natural satellites. Image credit: https://commons.wikimedia.org/wiki/File:Oceanplanet_lucianomendez.JPG</image:caption>
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      <image:caption>Public Area "The public area would be assembled into a complex structure in the form of a truncated octahedron. It would have a great room consisting of a lobby, restaurant, entertainment room, and other spaces where people could enjoy a dining experience, sports, and a variety of amusements under low-gravity conditions."\(^{[4}\)</image:caption>
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      <image:title>Articles Page 2 - Orbital Rings and Planet Building: Prelude to Colonizing the Solar System - Copy of Copy of Space Elevator</image:title>
      <image:caption>Depiction of a space elevator.\(^{[7]}\) Artwork retrieved from: http://prospective-tourisme.com/index.php/2017/08/10/entretien-laurent-queige-directeur-welcome-city-lab/</image:caption>
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      <image:title>Articles Page 2 - Orbital Rings and Planet Building: Prelude to Colonizing the Solar System - Copy of Copy of Space Elevator</image:title>
      <image:caption>Depiction of a space elevator. Artwork by Glenn Clovis at Artstation.\(^{[6]}\)</image:caption>
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      <image:caption>Artist's depiction of the interior of a Stanford torus. Painted by Donald E. Davis.</image:caption>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5b8b4e4b40ec9a2651daf478/1534192981008/shell+world.jpg</image:loc>
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      <image:caption>"An engineer suggests building a roof over a small planet so that Earthlike conditions could be maintained."\(^{[26]}\) The Shell World could be used to maintain Earth-like conditions on the surface of an alien planet or moon; hanging cities could be suspended from the interior wall of the shell world; or the outer-surface of the Shell World could be engineered to closely resemble the Earth. Some combination of all of the above could be possible, albeit only to a certain extent. Credit: by Karl Tate, Infographics Artist</image:caption>
    </image:image>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5b8b4e4b40ec9a2651daf47a/1534192981013/cities+dangling+from+shell+world.jpg</image:loc>
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      <image:caption>"Full cities could hang from the top of the shell that holds in the newly terraformed world's atmosphere."\(^{[27]}\) Image uploaded Oct. 7, 2013. Credit: Ken Roy/Tennessee Valley Interstellar Workshop</image:caption>
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      <image:caption>Larry Niven's Ringworld. Image credit: https://bargainbin4u.wordpress.com/2008/07/14/ringworld-by-larry-niven/</image:caption>
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      <image:caption>Artist’s depiction of a ring world. Image credit: https://www.deviantart.com/tomislavtikulin/art/Ringworld-Engineers-665659952</image:caption>
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      <image:title>Articles Page 2 - Orbital Rings and Planet Building: Prelude to Colonizing the Solar System</image:title>
      <image:caption>Artist’s depiction of a ring world. Image credit: https://www.deviantart.com/julian-faylona/art/Halcyon-Days-423868574</image:caption>
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      <image:title>Articles Page 2 - Orbital Rings and Planet Building: Prelude to Colonizing the Solar System - Copy of Copy of Lunar Mass Driver</image:title>
      <image:caption>Artist’s depiction of a lunar mass driver. The physicist Gerard K. O’Neil imagined using this device to electromagnetically launch lunar material into space for the purpose of being using to construct artificial space habitats for human residence and to move most industry off the Earth and into space. Image courtesy of NASA.</image:caption>
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      <image:title>Articles Page 2 - Orbital Rings and Planet Building: Prelude to Colonizing the Solar System - Copy of Copy of Lunar Mass Driver</image:title>
      <image:caption>Artist’s depiction of a Lunar mass driver. Artwork by Jay Wong.</image:caption>
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      <image:title>Articles Page 2 - Orbital Rings and Planet Building: Prelude to Colonizing the Solar System - Copy of Copy of Matrioshka Brain</image:title>
      <image:caption>Artist's impression of a Matrioshka Brain. Artwork by Jakub Grygier who is also a member of the SFIA production team.</image:caption>
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      <image:caption>"The inner and outer static orbital rings around Bronx are linked to a central geostationary ring by by carbon nanotube cables. The inner ring is only 265km above the clouds, while the outer ring is 75,600km from the planet's core."\(^{[19]}\) Image from Steve Bowers.</image:caption>
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      <image:caption>"The High Frontier: Human Colonies in Space is a 1976 book by Gerard K. O'Neill. It envisions large manned habitats in the Earth-Moon system, especially near stable Lagrangian points. Three designs are proposed: Island one (a modified Bernal sphere), Island two (a Stanford torus), and Island 3, two O'Neill cylinders. These would be constructed using raw materials from the lunar surface launched into space using a mass driver and from near-Earth asteroids. The habitats were to spin for simulated gravity and be illuminated and powered by the sun. Solar power satellites were proposed as a possible industry to support the habitats. The book won the 1977 Phi Beta Kappa Award in Science."\(^{[9]}\)</image:caption>
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      <image:caption>"Damocles is a large space port and elevator hub with stations fixed on [E]arth, located in an enormous, peaceful and very prosperous city, in a not-so-distant future.”\(^{[2]}\) In the year 2117 the most economical way to send people and cargo to outer space is using a space elevator. It’s not the quickest option but a very practical and effective one. Just like other similar Orbitowers placed on the Equator, the Damocles elevator hub provides this service. Space freight elevators are crucial to carry large components of interplanetary and the earlier interstellar vehicles into orbit, so they can be assembled in space instead of being launched by rockets. Autonomous trucks and cars arrive at the base’s ground to take passengers and cargo to the space elevator cabs. Flying vehicles land on the pads. The building itself is headquarters for many logistics companies, there are some offices and a hotel."\(^{[2]}\) Artwork by Sergio Botero at Artstation.\(^{[2]}\)</image:caption>
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      <image:caption>Artist's depiction of a Model 3 O'Neil cylinder which would be capable of supporting millions of a people, a complete biosphere, and all of the Earth's natural habitats. An O'Neil cylinder could also be used as an arc ship (sometimes also called a generation ship) to travel to other stars or galaxies. Image by Glenn Clovis from Artstation.\(^{[11]}\)</image:caption>
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      <image:caption>Solar eclipse inside an O'Neill cylinder\(^{[10]}\)</image:caption>
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      <image:caption>Interior of an O'Neill cylinder\(^{[10]}\)</image:caption>
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      <image:caption>Interior of an O'Neill cylinder\(^{[10]}\)</image:caption>
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      <image:caption>O'Neill cylinders\(^{[10]}\)</image:caption>
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      <image:caption>Artist's depiction of solar panels attached to a space elevator.</image:caption>
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      <image:caption>Artist’s depiction of an orbital ring.</image:caption>
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      <image:title>Articles Page 2 - Orbital Rings and Planet Building: Prelude to Colonizing the Solar System - Copy of Copy of Fusion Candles</image:title>
      <image:caption>Artist's impression of Fusion Candles which could be used to move Jupiter and its moons across interstellar or even intergalactic space and away from our solar system. Spaceship Jupiter! Artwork by Jeremy Jozwik from Artstation.</image:caption>
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      <image:caption>Artist’s depiction of an O’Neil cylinder. Artwork by Bruno Xavier.\(^{[12]}\)</image:caption>
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      <image:caption>"Terraformed Venus is surrounded by a Dynamic Orbital Ring, mosty constructed from carbon extracted from its original atmosphere."\(^{[24]}\) Image by Steve Bowers.</image:caption>
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      <image:caption>The concept of the Ocean Spiral was first unveiled by Shimizu Corporation, in conjunction with Tokyo University and Japan Agency for Marine-Earth Science and Technology, in 2014. The company excepts it to take 5 years to build an Ocean Spiral. The company expects the project to cost ¥3 trillion (approximately £20 billion). The company claims it could be ready for human habitation by 2030. Learn more by reading the article, Ocean Spiral is a conceptual city proposed beneath the surface of the ocean.</image:caption>
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      <image:caption>Guest Room Module "A module with 104 individual rooms, including 64 guest rooms, would be arranged on a ring that is 140 meters in diameter. The ring would generate an artificial gravity field of 0.7 G by rotating around three times per minute, so people could relax almost in the same manner as on earth."\(^{[4]}\)</image:caption>
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      <image:caption>Cut-away view of the interior of a Standford Torus. Image courtesy of NASA Ames Research Center.</image:caption>
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      <image:caption>“A suprajovian ring suspended above the gas giant Mungo.” Image from Steve Bowers. Image can also be found at Orion’s Arm.</image:caption>
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      <image:title>Articles Page 2 - Orbital Rings and Planet Building: Prelude to Colonizing the Solar System - Copy of Copy of Designer Planet</image:title>
      <image:caption>Artist’s depiction of a designer planet. Artwork by Alexey Shirokikh.</image:caption>
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      <image:caption>“Athelan, a suprashell erected around the gas giant Uranus in the Old Solar System.” Image from Steve Bowers. Image can also be found on Orion’s Arm.</image:caption>
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      <image:caption>“A Dreamsphere, a suprastellar shell completely surrounding a brown dwarf in the Stellar Umma region.” Image from Steve Bowers. Image can also be found on Orion’s Arm.</image:caption>
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      <image:caption>Artists depictions of gas giant refineries on two different gas giant planets. The gas giants depicted in these images are suspended by large blimps which hold a lifting gas. But it would also be possible, as we discuss in this article, to attach those gas giant refineries to the ceiling of a shell world or orbital ring. Artwork by Neil Blevins (top) and Jeremy Jozwik at Artstation.</image:caption>
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      <image:caption>"Arthur C. Clarke’s 3001: The Final Odyssey features an orbital ring held aloft by four enormous inhabitable towers (assumed successors to space elevators) at the Equator."\(^{[15]}\) For book summary, see: https://en.wikipedia.org/wiki/3001:_The_Final_Odyssey</image:caption>
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      <image:caption>Artist’s depiction of a Matrioshka brain. Image retrieved from: https://www.reddit.com/r/Futurology/comments/zu399/this_day_will_come_the_matrioshka_brain/</image:caption>
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      <image:caption>The infographic above shows the differences between a Type I (or K1), a Type II (or K2), and a Type III (or K3) civilization.</image:caption>
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      <image:title>Articles Page 2 - Orbital Rings and Planet Building: Prelude to Colonizing the Solar System - Copy of Copy of Anywhere in the World in Under an Hour</image:title>
      <image:caption>Elon Musk proposed using BFR rockets (see image above) as a planetary transportation system which could get you anywhere in the world in under one hour. Image courtesy of Space X.</image:caption>
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      <image:caption>Final Frontier Voyager (2007), George Grie. Óleo sobre lienzo.\(^{[13]}\)Credit: https://commons.wikimedia.org/wiki/File:Final-Frontier.jpg</image:caption>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5b8b4e4b40ec9a2651daf4a6/1535415737889/677_gas_interiors%5B1%5D.jpg</image:loc>
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      <image:caption>Illustration showing the rocky, icy, metallic cores of the four Jovian planets. Credit: NASA/Lunar and Planetary Institute Retrieved from: https://solarsystem.nasa.gov/resources/677/gas-giant-interiors-2003/</image:caption>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/5b8b4e4b40ec9a2651daf47c/5b8b4e4b40ec9a2651daf47d/1535351435005/shell_world_by_johnmalcolm1970.jpg</image:loc>
      <image:title>Articles Page 2 - Orbital Rings and Planet Building: Prelude to Colonizing the Solar System</image:title>
      <image:caption>Artist’s depiction of atlas towers connecting two separate shells in a shell world. Image credit: https://www.deviantart.com/johnmalcolm1970/art/Shell-World-114062545</image:caption>
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  </url>
  <url>
    <loc>https://www.gregschool.org/new-blog-2/2018/7/5/proof-of-the-theorem-fracsinxx1-t6c3x</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2018-07-19</lastmod>
    <image:image>
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      <image:title>Articles Page 2 - Proof of the Theorem: \(\lim_{ϴ→0}\frac{sinϴ}{ϴ}=1\)</image:title>
      <image:caption>Figure 2: As you can see graphically, for values of \(ϴ\) in the range \(\frac{-π}{2}&lt;ϴ&lt;\frac{π}{2}\), the following inequalities are true \(1≥\frac{sinϴ}{ϴ}≥cosϴ\). Notice that as \(ϴ\) approaches zero from both the negative and positive directions, the function \(\frac{sinϴ}{ϴ}\) gets "squeezed" into the same point on the graph.</image:caption>
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      <image:title>Articles Page 2 - Proof of the Theorem: \(\lim_{ϴ→0}\frac{sinϴ}{ϴ}=1\)</image:title>
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      <image:title>Articles Page 2 - Proof of the Theorem: \(\lim_{ϴ→0}\frac{sinϴ}{ϴ}=1\)</image:title>
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      <image:title>Articles Page 2 - Proof of the Theorem: \(\lim_{ϴ→0}\frac{sinϴ}{ϴ}=1\)</image:title>
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      <image:title>Articles Page 2 - Proof of the Theorem: \(\lim_{ϴ→0}\frac{sinϴ}{ϴ}=1\)</image:title>
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      <image:title>Articles Page 2 - Proof of the Theorem: \(\lim_{ϴ→0}\frac{sinϴ}{ϴ}=1\)</image:title>
      <image:caption>Figure 1: The wedge \(⪦OBA\) (colored blue) comprises a portion of the unit circle. The lengths \(AB\) and \(AC\) are the radius of the unit circle and are therefore equal to one. The heights of the triangles \(△OBA\) and \(△OCA\) can be found using basic trigonometry.</image:caption>
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      <image:title>Articles Page 2 - Proof of the Theorem: \(\lim_{ϴ→0}\frac{sinϴ}{ϴ}=1\)</image:title>
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      <image:title>Articles Page 2 - Proof of the Theorem: \(\lim_{ϴ→0}\frac{sinϴ}{ϴ}=1\)</image:title>
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  </url>
  <url>
    <loc>https://www.gregschool.org/new-blog-3</loc>
    <changefreq>daily</changefreq>
    <priority>0.75</priority>
    <lastmod>2017-09-06</lastmod>
  </url>
  <url>
    <loc>https://www.gregschool.org/new-blog-3/2017/6/20/76hgztk8ogz149g9acwmizq62okwe4</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-09</lastmod>
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      <image:title>Kinematics - Position Vectors, Displacement, Velocity, and Acceleration</image:title>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/598367b32994ca1073c1770b/1504720181840/</image:loc>
      <image:title>Kinematics - Position Vectors, Displacement, Velocity, and Acceleration</image:title>
      <image:caption>Figure 1 (click to enlarge)</image:caption>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5983789de3df28da0533f26f/1504720181845/</image:loc>
      <image:title>Kinematics - Position Vectors, Displacement, Velocity, and Acceleration</image:title>
      <image:caption>Figure 2</image:caption>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/new-blog-3/2017/6/20/faxkbn1icm37pyljps0j38mgdt0t22</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-09</lastmod>
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      <image:title>Kinematics - Basic Equations of Kinematics</image:title>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/work-and-energy</loc>
    <changefreq>daily</changefreq>
    <priority>0.75</priority>
    <lastmod>2017-09-06</lastmod>
  </url>
  <url>
    <loc>https://www.gregschool.org/work-and-energy/2017/6/21/the-dependency-of-theta-in-the-dot-product</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-09</lastmod>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59dbf476b7411c84d5126620/1507587195387/gfnf.jpg</image:loc>
      <image:title>Work and Energy - The Dependency of theta in the dot product</image:title>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5983aa73b8a79b354104890d/1504719988092/</image:loc>
      <image:title>Work and Energy - The Dependency of theta in the dot product</image:title>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/work-and-energy/2017/8/26/work-measure-of-energy-transfer</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2018-01-07</lastmod>
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      <image:title>Work and Energy - Work: Measure of Energy Transfer</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59ad885ebe42d663bf2e1c81/1504719976201/ff.png</image:loc>
      <image:title>Work and Energy - Work: Measure of Energy Transfer</image:title>
      <image:caption>Figure 1: Work done on a block by a constant force of \(-10\) newtons over a displacement of \(5\) meters.</image:caption>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/work-and-energy/2017/8/26/work-done-by-earths-gravity</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-09</lastmod>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59ad84c2cf81e0f6ca8266f6/1504720009155/vv.png</image:loc>
      <image:title>Work and Energy - Work done by Earth's Gravity</image:title>
      <image:caption>Figure 1: As an object moves along the path \(\vec{R}(t)\) from an initial height of \(y_i\) to a final height of \(y_f\), the Earth's gravitational force \(-m\vec{g}\) does work on the object.</image:caption>
    </image:image>
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      <image:title>Work and Energy - Work done by Earth's Gravity</image:title>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/work-and-energy/2017/8/27/work-done-by-force-moving-an-object-at-constant-height</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-09</lastmod>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59ac5f3ee6f2e1f1571bd04c/1504719999473/wet2.gif</image:loc>
      <image:title>Work and Energy - Work-Kinetic Energy Theorem</image:title>
      <image:caption>Figure 1: "Sunil Kumar Singh, Work - Kinetic Energy Theorem. February 2, 2013." http://cnx.org/content/m14095/latest/OpenStax CNX CC BY 3.0.</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59dbf6d151a58476eaac6e57/1507587794859/gfnf.jpg</image:loc>
      <image:title>Work and Energy - Work-Kinetic Energy Theorem</image:title>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/quasars</loc>
    <changefreq>daily</changefreq>
    <priority>0.75</priority>
    <lastmod>2017-11-04</lastmod>
  </url>
  <url>
    <loc>https://www.gregschool.org/new-blog-4</loc>
    <changefreq>daily</changefreq>
    <priority>0.75</priority>
    <lastmod>2019-02-24</lastmod>
  </url>
  <url>
    <loc>https://www.gregschool.org/new-blog-4/2017/6/28/colonizing-the-moon</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-09</lastmod>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59dd20fb4c326d6f4eaa4f5e/1534379535900/space+travela+nd+colonization+thumbnail.jpg</image:loc>
      <image:title>Outward Bound - Colonizing the Moon</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/598bef5915d5db7e604f616f/598bef5949fc2bdf477ecb94/1504670814209/LunarColonyRawlings650.jpg</image:loc>
      <image:title>Outward Bound - Colonizing the Moon</image:title>
      <image:caption>Domed lunar settlement illustration by Pat Rawlings, courtesy NASA.</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/598bef5915d5db7e604f616f/598bef5c6a49636f7039c911/1504670814212/57c6c882c29938af2da30517ba011ce4--wallpaper-space-make-money.jpg</image:loc>
      <image:title>Outward Bound - Colonizing the Moon</image:title>
      <image:caption>Painting by Pat Rawlings courtesy NASA</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/598bef5915d5db7e604f616f/598bef5ebebafb811d543e0f/1504670814216/landscape-1436809198-1197px-inflatable-habitat-s89-20084.jpg</image:loc>
      <image:title>Outward Bound - Colonizing the Moon</image:title>
      <image:caption>Artist concept of a moon colony via NASA</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/598bef5915d5db7e604f616f/598bef60ebbd1a5963bcdcc4/1504670814220/3130B2CE00000578-3446968-The_colonisation_of_the_Moon_and_then_Mars_will_have_taken_place-a-4_1455490616552.jpg</image:loc>
      <image:title>Outward Bound - Colonizing the Moon</image:title>
      <image:caption>The Smart Things Future Living Report</image:caption>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/new-blog-4/2017/6/28/colonizing-the-asteroids-and-comets-in-our-solar-system</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-09</lastmod>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59dd2242914e6b94c00e16ea/1534379569084/space+travela+nd+colonization+thumbnail.jpg</image:loc>
      <image:title>Outward Bound - Colonizing the Asteroids and Comets in our Solar System</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/598bf9fa6b8f5b57cf888b37/1504670946289/gjh.jpg</image:loc>
      <image:title>Outward Bound - Colonizing the Asteroids and Comets in our Solar System</image:title>
      <image:caption>Figure 1 (click to enlarge)</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/598bfaa1c534a55657b23a6f/1504670946291/</image:loc>
      <image:title>Outward Bound - Colonizing the Asteroids and Comets in our Solar System</image:title>
      <image:caption>Figure 2 - click to enlarge (Source) "This shot shows the inside of the asteroid from the previous scene. Just as I wrote about that scene, this is a highly speculative vision of an impressive piece of human engineering - a concept that science fiction author Kim Stanley Robinson calls a "terraruim" in his novel "2312". It is also not unlike what Arthur C. Clarke described in his novel "Rendezvous with Rama". What we see here is the inside of a hollowed out asteroid, pressurized and filled with a breathable atmosphere. Like I described in the previous scene, the whole structure is put into a revolving rotation, simulating the effect of gravity toward the inside "walls" of the cylinder shape we see. The structure in this scene has a diameter of about 7 kilometers and revolves with a speed of 1 rotation every 2 minutes, simulating the effect of 1g (the gravity pull we feel on Earth) at the surface of the inside. This place is also filled with water, creating lakes and seas wrapped along with the landscape. An artificial sun is running along a rail in the middle of the space, simulating a daylight cycle. This scene is of course built from scratch, but I used countless satellite photos of the Earth to texture the landscape. I actually used a slightly warped world map to create the outlines between land and water, as some may notice a couple of familiar shorelines."\(^{[3]}\)</image:caption>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/new-blog-4/2017/6/28/terraforming-mars</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-09</lastmod>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59545d4f197aeae989d892c0/1504671069022/</image:loc>
      <image:title>Outward Bound - Terraforming and Colonizing Mars</image:title>
    </image:image>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59dd22ee268b966b06470ce6/1534475777294/space+travela+nd+colonization+thumbnail.jpg</image:loc>
      <image:title>Outward Bound - Terraforming and Colonizing Mars</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/598b820737c581cb56c4ac02/1504671069020/ares2.jpg</image:loc>
      <image:title>Outward Bound - Terraforming and Colonizing Mars</image:title>
      <image:caption>Artist's depiction of the Ares spaceship from Kim Stanley Robinson's novel, Red Mars.</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59545d7ce3df28275b0a516e/1504671069037/</image:loc>
      <image:title>Outward Bound - Terraforming and Colonizing Mars</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/598b84109f745655815f327d/1504671069032/</image:loc>
      <image:title>Outward Bound - Terraforming and Colonizing Mars</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/598b8142a5790a2392f5caa1/1504671069028/</image:loc>
      <image:title>Outward Bound - Terraforming and Colonizing Mars</image:title>
      <image:caption>"This shot follows the cabin of a space elevator descending on a cable towards the northern parts of the Terra Cimmeria highlands on Mars. A large settlement, hinted as glowing lights in the dark, can be seen far below on the ground. One of Mars' two moons - Phobos - is seen above the cabin to the left of the cable in the beginning of the shot." This image was produced by Erik Wernquist.</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/598b808915d5db8c6665223f/1504671069034/olympus.jpg</image:loc>
      <image:title>Outward Bound - Terraforming and Colonizing Mars</image:title>
      <image:caption>Poster by SpaceX</image:caption>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/new-blog-4/2017/8/13/why-colonize-the-universe</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-08</lastmod>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59d3e300f5e231a4eced49e7/1507688500138/51i54HqlYHL._SY344_BO1%2C204%2C203%2C200_.jpg</image:loc>
      <image:title>Outward Bound - Why Colonize the Universe?</image:title>
      <image:caption>In Carl Sagan's book Pale Blue Dot, he argued that humans evolved a love for exploration as an essential part of our survival as a species. It was this evolutionary trait which compelled our hunter-gather ancestors to leave their home—Africa—when times were getting rough and to meander across the planet. As planetary catastrophes become increasingly likely as time rolls by, Sagan argues that this same "survival strategy" will perhaps compell humanity to colonize the solar system, and beyond.</image:caption>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59dd7f918fd4d260ef9b9a70/1507688500135/space+travela+nd+colonization+thumbnail.jpg</image:loc>
      <image:title>Outward Bound - Why Colonize the Universe?</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59d3e5550abd046aead94cf7/1507688500140/factoriesins.jpg</image:loc>
      <image:title>Outward Bound - Why Colonize the Universe?</image:title>
      <image:caption>An O'Neil cylinder is a type of megastructure and artificial space habitat which was first proposed by the physicist Gerard O'Neil in 1976. An O'Neil cylinder would consist of two immense, rotating, cylindrical habitats (illustrated above) which would spin at a angular velocity that generated centrifugal forces along the interior surfaces of the cylinders which would emulate Earth-gravity. Each cylindrical habitat would be 5 miles in diameter and 20 miles long.</image:caption>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/new-blog-4/2017/9/11/harvesting-resources-from-saturn-and-titan</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2018-04-08</lastmod>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59fbba62ec212defc9fec86f/1509918211623/facebook+img+thumbnail.jpg</image:loc>
      <image:title>Outward Bound - Harvesting Resources from Saturn and Titan</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59ff83a2f9619a4291a4561b/1509918211631/space+travela+nd+colonization+thumbnail.png</image:loc>
      <image:title>Outward Bound - Harvesting Resources from Saturn and Titan</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59fbba7d085229ec68487ed1/1509918211627/google+img+thumbnail.jpg</image:loc>
      <image:title>Outward Bound - Harvesting Resources from Saturn and Titan</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59fbba908165f5e83ce1f7ee/1509918211625/twiiter+img+thumbnail.jpg</image:loc>
      <image:title>Outward Bound - Harvesting Resources from Saturn and Titan</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59fbbac00d9297e902c593aa/1509918211620/share+img+for+spacetrav+and+col+thumbnail.png</image:loc>
      <image:title>Outward Bound - Harvesting Resources from Saturn and Titan</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59fbba6cc830255c2b87cd6a/1509918211629/email+img+thumbnail.jpg</image:loc>
      <image:title>Outward Bound - Harvesting Resources from Saturn and Titan</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59b70924e45a7cbc861db975/1509918211633/WANDERERS_ligeia_mare_01.jpg</image:loc>
      <image:title>Outward Bound - Harvesting Resources from Saturn and Titan</image:title>
      <image:caption>"With an average temperature of -180 C all water here is frozen hard as rock. In fact, the surface landscape of Titan is indeed mostly made of frozen water ice. But Titan's atmosphere is rich in hydrocarbons such as methane and ethane, and the low temperature is perfect for these elements to occur naturally in three states; frozen, liquid and gas. So, just as on Earth where we have a water cycle (ice melts, becomes water, water evaporates into clouds, turning into liquid and becomes rain and so forth), Titan has a methane cycle. Methane evaporates and rises to form clouds, eventually turning into rain, falling over the surface. And this is the most amazing part; the rain in some places is enough to fill entire lakes. Lakes of methane! Titan is the only place in the Solar System, other than Earth, known to have large bodies of liquid on its surface. And they are really there, huge lakes, with shorelines, islands and small archipelagos. This scene takes place over a lake know as Ligeia Mare, the second largest on Titan, about 500 kilometers in diameter, located in the north polar region of the moon. The second fantastic feature I wanted to illustrate is the combination of Titan's very dense atmosphere and its relatively low gravity. As a human on Titan you would weigh about 14% of what you do on Earth, and in the dense atmosphere it would be enough to strap wings on your arms to make you able to fly like a bird. On Titan you could fly like a bird, over lakes of methane! (If you wore some really warm clothes of course.)" Image and image description credit: WANDERERS - a short film by EriK Wernquist</image:caption>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/new-blog-4/2017/9/19/the-kardeshev-scale</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-08</lastmod>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/59c1db0d6f4ca36e46f4b75b/59c1db0d1f318d7984d23891/1507687265519/dyson_sphere_second_1024.jpg</image:loc>
      <image:title>Outward Bound - The Kardeshev Scale</image:title>
      <image:caption>Dyson sphere. Credit: capnhack.com</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/59c1db0d6f4ca36e46f4b75b/59c1db131f318d7984d238db/1507750791352/17202572._SX540_.jpg</image:loc>
      <image:title>Outward Bound - The Kardeshev Scale</image:title>
      <image:caption>Artist's depiction of a ring world. Credit: http://richardfrazer.com/</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59d3df2ecf81e01fd0318dfe/1507687265518/1024px-Consommations_%C3%A9nerg%C3%A9tiques_des_trois_types_de_l%27%C3%A9chelle_de_Kardashev.svg.png</image:loc>
      <image:title>Outward Bound - The Kardeshev Scale</image:title>
      <image:caption>The Kardeshev scale ranks how advanced a technological civilization is based upon their total power consumption. A Type I civilization is capable of harnessing all of their home plant's power of \(~10^{16}W\); a Type II civilization has harnessed the power of their star ( \(~10^{26}W\)); and a Type III civilization has harnessed the power output of their entire galaxy ( \(~10^{36}W\)). There are even Type IV and Type V civilization which go beyond Kardeshev's original scale.</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59dd6e1159cc68c004650b88/1507687265526/bubble-universes-computer-illustration-of-multiple-bubble-universes-G4C3H0.jpg</image:loc>
      <image:title>Outward Bound - The Kardeshev Scale</image:title>
      <image:caption>Artist's depiction of the multi-verse.</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59dd7aff80bd5ee9087223bd/1507687265516/space+travela+nd+colonization+thumbnail.jpg</image:loc>
      <image:title>Outward Bound - The Kardeshev Scale</image:title>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/new-blog-4/2017/9/25/colonizing-and-terraforming-venus-59y59-aty88</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2018-04-08</lastmod>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5ac960e68a922dc773a0185b/1523144000964/space+colon+author+date.jpg</image:loc>
      <image:title>Outward Bound - Colonizing and Terraforming Venus</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5ac960e68a922dc773a01851/1523145768016/share+b.jpg</image:loc>
      <image:title>Outward Bound - Colonizing and Terraforming Venus</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5ac960e68a922dc773a01857/1523144061656/google+share+thumbnail_preview.jpg</image:loc>
      <image:title>Outward Bound - Colonizing and Terraforming Venus</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5ac960e68a922dc773a01853/1523144015110/facebook+thumbnail.jpg</image:loc>
      <image:title>Outward Bound - Colonizing and Terraforming Venus</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5ac960e68a922dc773a01859/1523144044465/email+thumbnail_preview.jpg</image:loc>
      <image:title>Outward Bound - Colonizing and Terraforming Venus</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5ac960e68a922dc773a0185d/1508644545185/1.10-1024x768.jpg</image:loc>
      <image:title>Outward Bound - Colonizing and Terraforming Venus</image:title>
      <image:caption>Artist concept of lightning on Venus. Image credit: ESA</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5ac960e68a922dc773a0185f/1507060053549/venus-cloud-city.jpg</image:loc>
      <image:title>Outward Bound - Colonizing and Terraforming Venus</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5ac960e68a922dc773a01855/1523144026480/Twitter+thumbnail_preview.jpg</image:loc>
      <image:title>Outward Bound - Colonizing and Terraforming Venus</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5ac960e68a922dc773a01861/1510882341344/TerraformedVenus%5B1%5D.jpg</image:loc>
      <image:title>Outward Bound - Colonizing and Terraforming Venus</image:title>
      <image:caption>"A conceptual picture I made of Venus if it were terraformed. (Credit: Daein Ballard) Notice the interesting cloud formations and that the planet has polar caps. I decided to show the planet this way after studying Venus' atmosphere. The two Hadley cells the planet has stop at 70 degrees north and south. So the polar regions are cut off from the warm air. Also the slow rotation of the planet causes the clouds to whip around the planet very fast, especially at the equator, to balance out the temperature difference between day and night sides of the planet."\(^{[5]}\) Image credit: Ittiz at the English language Wikipedia [GFDL (http://www.gnu.org/copyleft/fdl.html) or CC-BY-SA-3.0 (http://creativecommons.org/licenses/by-sa/3.0/)], via Wikimedia Commons</image:caption>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/new-blog-4/2017/9/12/colonizing-the-kuiper-belt-and-oort-cloud-g53ff-smdal</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2018-04-08</lastmod>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/59fce5b264265f1222b3f728/59fce5b264265f1222b3f72b/1507689697156/uranus-gas-zoom.jpg</image:loc>
      <image:title>Outward Bound - Colonizing the Kuiper Belt and Oort Cloud</image:title>
      <image:caption>Artist’s depiction of Neptune’s (above image) and Uranus’s (below image) atmosphere being harvested for resources such as nitrogen.</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/59fce5b264265f1222b3f728/59fce5b264265f1222b3f729/1507689697153/george-dennis-the-fountains-of-neptune.jpg</image:loc>
      <image:title>Outward Bound - Colonizing the Kuiper Belt and Oort Cloud</image:title>
      <image:caption />
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59fce5b264265f1222b3f71c/1509746045831/twiiter+img+thumbnail.jpg</image:loc>
      <image:title>Outward Bound - Colonizing the Kuiper Belt and Oort Cloud</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59fce5b264265f1222b3f72e/1507689697158/OortCloud_P-sys%28PNG-fin%291.png</image:loc>
      <image:title>Outward Bound - Colonizing the Kuiper Belt and Oort Cloud</image:title>
      <image:caption>Another size comparison of the solar system to the Oort Cloud.</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59fce5b264265f1222b3f726/1507689697151/Ancient_Mars3_02.jpg</image:loc>
      <image:title>Outward Bound - Colonizing the Kuiper Belt and Oort Cloud</image:title>
      <image:caption>Artist's depiction of Fesenkov Crater on Mars filled with liquid water.</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59fce5b264265f1222b3f722/1507689697148/space+travela+nd+colonization+thumbnail.jpg</image:loc>
      <image:title>Outward Bound - Colonizing the Kuiper Belt and Oort Cloud</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59fce5b264265f1222b3f71e/1509746082746/google+img+thumbnail.jpg</image:loc>
      <image:title>Outward Bound - Colonizing the Kuiper Belt and Oort Cloud</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59fce5b264265f1222b3f724/1507689697150/Kuiper_oort.jpg</image:loc>
      <image:title>Outward Bound - Colonizing the Kuiper Belt and Oort Cloud</image:title>
      <image:caption>A size comparison of the Kuiper belt and outer solar system to the Oort Cloud.</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59fce5b264265f1222b3f718/1509745876713/share+technology++img.jpg</image:loc>
      <image:title>Outward Bound - Colonizing the Kuiper Belt and Oort Cloud</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59fce5b264265f1222b3f71a/1509746065358/facebook+img+thumbnail.jpg</image:loc>
      <image:title>Outward Bound - Colonizing the Kuiper Belt and Oort Cloud</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59fce5b264265f1222b3f720/1509745710543/email+img+thumbnail.jpg</image:loc>
      <image:title>Outward Bound - Colonizing the Kuiper Belt and Oort Cloud</image:title>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/new-blog-4/2017/9/10/how-to-produce-water-and-oxygen-on-mars-njmkh-3ym9w</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2018-04-08</lastmod>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5ac960ff88251b53483274e2/1523144687004/google+share+thumbnail_preview.jpg</image:loc>
      <image:title>Outward Bound - How to Produce Water and Oxygen on Mars</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5ac960ff88251b53483274de/1523144639537/facebook+thumbnail.jpg</image:loc>
      <image:title>Outward Bound - How to Produce Water and Oxygen on Mars</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5ac960ff88251b53483274ea/1511021201272/mars3%5B1%5D.jpg</image:loc>
      <image:title>Outward Bound - How to Produce Water and Oxygen on Mars</image:title>
      <image:caption>The rover above is capable of releasing frozen water from regolith by heating it using microwaves. Credit: SUTD/Gilmour Space Corporation</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5ac960ff88251b53483274e6/1523144599773/space+colon+author+date.jpg</image:loc>
      <image:title>Outward Bound - How to Produce Water and Oxygen on Mars</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5ac960ff88251b53483274e0/1523144648835/Twitter+thumbnail_preview.jpg</image:loc>
      <image:title>Outward Bound - How to Produce Water and Oxygen on Mars</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5ac960ff88251b53483274e4/1523144671889/email+thumbnail_preview.jpg</image:loc>
      <image:title>Outward Bound - How to Produce Water and Oxygen on Mars</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5ac960ff88251b53483274dc/1523145434173/share+b.jpg</image:loc>
      <image:title>Outward Bound - How to Produce Water and Oxygen on Mars</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5ac960ff88251b53483274e8/1510888610952/extracting+water+from+Mars%27+regolith.jpg</image:loc>
      <image:title>Outward Bound - How to Produce Water and Oxygen on Mars</image:title>
      <image:caption>"Truck, oven, and slag pile system for extracting water from Martian soil."\(^{[2]}\) Artwork by Michael Carroll.</image:caption>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/new-blog-4/2018/7/20/space-based-solar-power-3ptal-jreey-fh4ws-wk9fy</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2018-09-18</lastmod>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/5b8f60e140ec9ad5c875b0ba/5b8f60e140ec9ad5c875b0bb/1535488899287/moon+mass+drive-finished-jayproductspainting%5B1%5D.jpg</image:loc>
      <image:title>Outward Bound - Orbital Rings and Planet Building: Prelude to Colonizing the Solar System - Copy of Copy of Copy of Lunar Mass Driver</image:title>
      <image:caption>Artist’s depiction of a Lunar mass driver. Artwork by Jay Wong.</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/5b8f60e140ec9ad5c875b0ba/5b8f60e140ec9ad5c875b0bd/1535488181201/Lunar_base_concept_drawing_s78_23252%5B1%5D.jpg</image:loc>
      <image:title>Outward Bound - Orbital Rings and Planet Building: Prelude to Colonizing the Solar System - Copy of Copy of Copy of Lunar Mass Driver</image:title>
      <image:caption>Artist’s depiction of a lunar mass driver. The physicist Gerard K. O’Neil imagined using this device to electromagnetically launch lunar material into space for the purpose of being using to construct artificial space habitats for human residence and to move most industry off the Earth and into space. Image courtesy of NASA.</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5b8f60e140ec9ad5c875b0ce/1535309406755/bigggstandfordtoruss.jpg</image:loc>
      <image:title>Outward Bound - Orbital Rings and Planet Building: Prelude to Colonizing the Solar System</image:title>
      <image:caption>Cut-away view of the interior of a Standford Torus. Image courtesy of NASA Ames Research Center.</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/5b8f60e140ec9ad5c875b110/5b8f60e140ec9ad5c875b111/1535487301500/jeremy-jozwik-ia-neptune-comp2-0000.jpg</image:loc>
      <image:title>Outward Bound - Orbital Rings and Planet Building: Prelude to Colonizing the Solar System</image:title>
      <image:caption>Artists depictions of gas giant refineries on two different gas giant planets. The gas giants depicted in these images are suspended by large blimps which hold a lifting gas. But it would also be possible, as we discuss in this article, to attach those gas giant refineries to the ceiling of a shell world or orbital ring. Artwork by Neil Blevins (top) and Jeremy Jozwik at Artstation.</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/5b8f60e140ec9ad5c875b110/5b8f60e140ec9ad5c875b113/1535487143670/neil-blevins-megastructures-9-gas-giant-refinery-color-sketch.jpg</image:loc>
      <image:title>Outward Bound - Orbital Rings and Planet Building: Prelude to Colonizing the Solar System</image:title>
      <image:caption />
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/5b8f60e140ec9ad5c875b110/5b8f60e140ec9ad5c875b115/1535351657862/neil-blevins-megastructures-9-gas-giant-refinery-design-packet.jpg</image:loc>
      <image:title>Outward Bound - Orbital Rings and Planet Building: Prelude to Colonizing the Solar System</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5b8f60e140ec9ad5c875b072/1535847641084/gggggggggggggggggggggggg.png</image:loc>
      <image:title>Outward Bound - Orbital Rings and Planet Building: Prelude to Colonizing the Solar System</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5b8f60e140ec9ad5c875b0ac/1535609604928/c58d9cac14778ce30b60c5c6d63fee2a.jpg</image:loc>
      <image:title>Outward Bound - Orbital Rings and Planet Building: Prelude to Colonizing the Solar System</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/5b8f60e140ec9ad5c875b0d6/5b8f60e140ec9ad5c875b0d7/1535611132816/SpaceX+crew+Big+Falcon+Rocket+%28BFR%29+launching+from+Earth.jpg</image:loc>
      <image:title>Outward Bound - Orbital Rings and Planet Building: Prelude to Colonizing the Solar System - Copy of Copy of Copy of Anywhere in the World in Under an Hour</image:title>
      <image:caption>Elon Musk proposed using BFR rockets (see image above) as a planetary transportation system which could get you anywhere in the world in under one hour. Image courtesy of Space X.</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/5b8f60e140ec9ad5c875b08e/5b8f60e140ec9ad5c875b08f/1535827243822/seattle_space_elevator_observatory_by_alterbr33d-d5j8j2p-750x375%402x%5B1%5D.png</image:loc>
      <image:title>Outward Bound - Orbital Rings and Planet Building: Prelude to Colonizing the Solar System - Copy of Copy of Copy of Space Elevator</image:title>
      <image:caption>Depiction of a space elevator.\(^{[7]}\) Artwork retrieved from: http://prospective-tourisme.com/index.php/2017/08/10/entretien-laurent-queige-directeur-welcome-city-lab/</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/5b8f60e140ec9ad5c875b08e/5b8f60e140ec9ad5c875b091/1535827236841/space-elevator%5B1%5D.jpg</image:loc>
      <image:title>Outward Bound - Orbital Rings and Planet Building: Prelude to Colonizing the Solar System - Copy of Copy of Copy of Space Elevator</image:title>
      <image:caption>Depiction of a space elevator. Artwork by Glenn Clovis at Artstation.\(^{[6]}\)</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5b8f60e140ec9ad5c875b128/1535500914749/main-qimg-c723f245065082e7f3de09cd458d893e%5B1%5D.png</image:loc>
      <image:title>Outward Bound - Orbital Rings and Planet Building: Prelude to Colonizing the Solar System</image:title>
      <image:caption>The infographic above shows the differences between a Type I (or K1), a Type II (or K2), and a Type III (or K3) civilization.</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/5b8f60e140ec9ad5c875b074/5b8f60e140ec9ad5c875b083/1535343290369/sergio-botero-tflp-damocles-presentation-freight-cab-web.jpg</image:loc>
      <image:title>Outward Bound - Orbital Rings and Planet Building: Prelude to Colonizing the Solar System</image:title>
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      <image:title>Outward Bound - Orbital Rings and Planet Building: Prelude to Colonizing the Solar System</image:title>
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      <image:title>Outward Bound - Orbital Rings and Planet Building: Prelude to Colonizing the Solar System</image:title>
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      <image:title>Outward Bound - Orbital Rings and Planet Building: Prelude to Colonizing the Solar System</image:title>
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      <image:title>Outward Bound - Orbital Rings and Planet Building: Prelude to Colonizing the Solar System</image:title>
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      <image:title>Outward Bound - Orbital Rings and Planet Building: Prelude to Colonizing the Solar System</image:title>
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      <image:title>Outward Bound - Orbital Rings and Planet Building: Prelude to Colonizing the Solar System</image:title>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/5b8f60e140ec9ad5c875b074/5b8f60e140ec9ad5c875b079/1535825798962/sergio-botero-tflp-damocles-comp-4-v1-web.jpg</image:loc>
      <image:title>Outward Bound - Orbital Rings and Planet Building: Prelude to Colonizing the Solar System</image:title>
      <image:caption>"Damocles is a large space port and elevator hub with stations fixed on [E]arth, located in an enormous, peaceful and very prosperous city, in a not-so-distant future.”\(^{[2]}\) In the year 2117 the most economical way to send people and cargo to outer space is using a space elevator. It’s not the quickest option but a very practical and effective one. Just like other similar Orbitowers placed on the Equator, the Damocles elevator hub provides this service. Space freight elevators are crucial to carry large components of interplanetary and the earlier interstellar vehicles into orbit, so they can be assembled in space instead of being launched by rockets. Autonomous trucks and cars arrive at the base’s ground to take passengers and cargo to the space elevator cabs. Flying vehicles land on the pads. The building itself is headquarters for many logistics companies, there are some offices and a hotel."\(^{[2]}\) Artwork by Sergio Botero at Artstation.\(^{[2]}\)</image:caption>
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      <image:title>Outward Bound - Orbital Rings and Planet Building: Prelude to Colonizing the Solar System</image:title>
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      <image:title>Outward Bound - Orbital Rings and Planet Building: Prelude to Colonizing the Solar System</image:title>
      <image:caption>"The High Frontier: Human Colonies in Space is a 1976 book by Gerard K. O'Neill. It envisions large manned habitats in the Earth-Moon system, especially near stable Lagrangian points. Three designs are proposed: Island one (a modified Bernal sphere), Island two (a Stanford torus), and Island 3, two O'Neill cylinders. These would be constructed using raw materials from the lunar surface launched into space using a mass driver and from near-Earth asteroids. The habitats were to spin for simulated gravity and be illuminated and powered by the sun. Solar power satellites were proposed as a possible industry to support the habitats. The book won the 1977 Phi Beta Kappa Award in Science."\(^{[9]}\)</image:caption>
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      <image:title>Outward Bound - Orbital Rings and Planet Building: Prelude to Colonizing the Solar System</image:title>
      <image:caption>Animation of a sheet of pure graphene rolled up into a carbon nanotube. Credit: https://commons.wikimedia.org/wiki/File:Kohlenstoffnanoroehre_Animation.gif</image:caption>
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      <image:title>Outward Bound - Orbital Rings and Planet Building: Prelude to Colonizing the Solar System</image:title>
      <image:caption>Artist’s depiction of a Matrioshka brain. Image retrieved from: https://www.reddit.com/r/Futurology/comments/zu399/this_day_will_come_the_matrioshka_brain/</image:caption>
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      <image:title>Outward Bound - Orbital Rings and Planet Building: Prelude to Colonizing the Solar System</image:title>
      <image:caption>Artist's depiction of a Model 3 O'Neil cylinder which would be capable of supporting millions of a people, a complete biosphere, and all of the Earth's natural habitats. An O'Neil cylinder could also be used as an arc ship (sometimes also called a generation ship) to travel to other stars or galaxies. Image by Glenn Clovis from Artstation.\(^{[11]}\)</image:caption>
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      <image:title>Outward Bound - Orbital Rings and Planet Building: Prelude to Colonizing the Solar System</image:title>
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      <image:title>Outward Bound - Orbital Rings and Planet Building: Prelude to Colonizing the Solar System</image:title>
      <image:caption>Image above portrays Nikola Tesla, the famous inventor who first conceived of the notion of orbital rings in the 1870s shortly after recovering from malaria.</image:caption>
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      <image:title>Outward Bound - Orbital Rings and Planet Building: Prelude to Colonizing the Solar System</image:title>
      <image:caption>Artist's depiction of solar panels attached to a space elevator.</image:caption>
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      <image:title>Outward Bound - Orbital Rings and Planet Building: Prelude to Colonizing the Solar System</image:title>
      <image:caption>Public Area "The public area would be assembled into a complex structure in the form of a truncated octahedron. It would have a great room consisting of a lobby, restaurant, entertainment room, and other spaces where people could enjoy a dining experience, sports, and a variety of amusements under low-gravity conditions."\(^{[4}\)</image:caption>
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      <image:title>Outward Bound - Orbital Rings and Planet Building: Prelude to Colonizing the Solar System</image:title>
      <image:caption>Artist's illustration of a hypothetical ocean planet with two natural satellites. Image credit: https://commons.wikimedia.org/wiki/File:Oceanplanet_lucianomendez.JPG</image:caption>
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      <image:title>Outward Bound - Orbital Rings and Planet Building: Prelude to Colonizing the Solar System - Copy of Copy of Copy of Fusion Candles</image:title>
      <image:caption>Artist's impression of Fusion Candles which could be used to move Jupiter and its moons across interstellar or even intergalactic space and away from our solar system. Spaceship Jupiter! Artwork by Jeremy Jozwik from Artstation.</image:caption>
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      <image:title>Outward Bound - Orbital Rings and Planet Building: Prelude to Colonizing the Solar System</image:title>
      <image:caption>Artist’s depiction of an orbital ring which appeared in Issue 7 of the magazine, All About Space. Image by Adrian Mann.\(^{[18]}\)</image:caption>
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      <image:title>Outward Bound - Orbital Rings and Planet Building: Prelude to Colonizing the Solar System</image:title>
      <image:caption>"Terraformed Venus is surrounded by a Dynamic Orbital Ring, mosty constructed from carbon extracted from its original atmosphere."\(^{[24]}\) Image by Steve Bowers.</image:caption>
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      <image:title>Outward Bound - Orbital Rings and Planet Building: Prelude to Colonizing the Solar System</image:title>
      <image:caption>Artist’s depiction of an O’Neil cylinder. Artwork by Bruno Xavier.\(^{[12]}\)</image:caption>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/5b8f60e140ec9ad5c875b0de/5b8f60e140ec9ad5c875b0e3/1535505977487/A2ljC-Qaok-kAJvzyNWu_Shimizu2%5B1%5D.jpg</image:loc>
      <image:title>Outward Bound - Orbital Rings and Planet Building: Prelude to Colonizing the Solar System</image:title>
      <image:caption>The concept of the Ocean Spiral was first unveiled by Shimizu Corporation, in conjunction with Tokyo University and Japan Agency for Marine-Earth Science and Technology, in 2014. The company excepts it to take 5 years to build an Ocean Spiral. The company expects the project to cost ¥3 trillion (approximately £20 billion). The company claims it could be ready for human habitation by 2030. Learn more by reading the article, Ocean Spiral is a conceptual city proposed beneath the surface of the ocean.</image:caption>
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      <image:title>Outward Bound - Orbital Rings and Planet Building: Prelude to Colonizing the Solar System</image:title>
      <image:caption>Interior of an O'Neill cylinder\(^{[10]}\)</image:caption>
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      <image:title>Outward Bound - Orbital Rings and Planet Building: Prelude to Colonizing the Solar System</image:title>
      <image:caption>O'Neill cylinders\(^{[10]}\)</image:caption>
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      <image:caption>Solar eclipse inside an O'Neill cylinder\(^{[10]}\)</image:caption>
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      <image:title>Outward Bound - Orbital Rings and Planet Building: Prelude to Colonizing the Solar System</image:title>
      <image:caption>Interior of an O'Neill cylinder\(^{[10]}\)</image:caption>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5b8f60e140ec9ad5c875b0b8/1535488475236/3001TheFinalOdyssey%5B1%5D.jpg</image:loc>
      <image:title>Outward Bound - Orbital Rings and Planet Building: Prelude to Colonizing the Solar System</image:title>
      <image:caption>"Arthur C. Clarke’s 3001: The Final Odyssey features an orbital ring held aloft by four enormous inhabitable towers (assumed successors to space elevators) at the Equator."\(^{[15]}\) For book summary, see: https://en.wikipedia.org/wiki/3001:_The_Final_Odyssey</image:caption>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5b8f60e140ec9ad5c875b0f4/1534192981008/shell+world.jpg</image:loc>
      <image:title>Outward Bound - Orbital Rings and Planet Building: Prelude to Colonizing the Solar System</image:title>
      <image:caption>"An engineer suggests building a roof over a small planet so that Earthlike conditions could be maintained."\(^{[26]}\) The Shell World could be used to maintain Earth-like conditions on the surface of an alien planet or moon; hanging cities could be suspended from the interior wall of the shell world; or the outer-surface of the Shell World could be engineered to closely resemble the Earth. Some combination of all of the above could be possible, albeit only to a certain extent. Credit: by Karl Tate, Infographics Artist</image:caption>
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      <image:title>Outward Bound - Orbital Rings and Planet Building: Prelude to Colonizing the Solar System</image:title>
      <image:caption>Guest Room Module "A module with 104 individual rooms, including 64 guest rooms, would be arranged on a ring that is 140 meters in diameter. The ring would generate an artificial gravity field of 0.7 G by rotating around three times per minute, so people could relax almost in the same manner as on earth."\(^{[4]}\)</image:caption>
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      <image:title>Outward Bound - Orbital Rings and Planet Building: Prelude to Colonizing the Solar System - Copy of Copy of Copy of Designer Planet</image:title>
      <image:caption>Artist’s depiction of a designer planet. Artwork by Alexey Shirokikh.</image:caption>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/5b8f60e140ec9ad5c875b118/5b8f60e140ec9ad5c875b11b/1535487329539/Dreamsphere.jpg</image:loc>
      <image:title>Outward Bound - Orbital Rings and Planet Building: Prelude to Colonizing the Solar System</image:title>
      <image:caption>“A Dreamsphere, a suprastellar shell completely surrounding a brown dwarf in the Stellar Umma region.” Image from Steve Bowers. Image can also be found on Orion’s Arm.</image:caption>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/5b8f60e140ec9ad5c875b118/5b8f60e140ec9ad5c875b11d/1535352753554/med_suprajupiter.png</image:loc>
      <image:title>Outward Bound - Orbital Rings and Planet Building: Prelude to Colonizing the Solar System</image:title>
      <image:caption>“A suprajovian ring suspended above the gas giant Mungo.” Image from Steve Bowers. Image can also be found at Orion’s Arm.</image:caption>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/5b8f60e140ec9ad5c875b118/5b8f60e140ec9ad5c875b11f/1535352742220/Athelan.jpg</image:loc>
      <image:title>Outward Bound - Orbital Rings and Planet Building: Prelude to Colonizing the Solar System</image:title>
      <image:caption>“Athelan, a suprashell erected around the gas giant Uranus in the Old Solar System.” Image from Steve Bowers. Image can also be found on Orion’s Arm.</image:caption>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5b8f60e140ec9ad5c875b0f6/1534192981013/cities+dangling+from+shell+world.jpg</image:loc>
      <image:title>Outward Bound - Orbital Rings and Planet Building: Prelude to Colonizing the Solar System</image:title>
      <image:caption>"Full cities could hang from the top of the shell that holds in the newly terraformed world's atmosphere."\(^{[27]}\) Image uploaded Oct. 7, 2013. Credit: Ken Roy/Tennessee Valley Interstellar Workshop</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/5b8f60e140ec9ad5c875b108/5b8f60e140ec9ad5c875b109/1535483823007/jakub-grygier-005-matrioshka-brain-ab.jpg</image:loc>
      <image:title>Outward Bound - Orbital Rings and Planet Building: Prelude to Colonizing the Solar System - Copy of Copy of Copy of Matrioshka Brain</image:title>
      <image:caption>Artist's impression of a Matrioshka Brain. Artwork by Jakub Grygier who is also a member of the SFIA production team.</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/5b8f60e140ec9ad5c875b0fc/5b8f60e140ec9ad5c875b101/1535351231677/ringworld.jpg</image:loc>
      <image:title>Outward Bound - Orbital Rings and Planet Building: Prelude to Colonizing the Solar System</image:title>
      <image:caption>Larry Niven's Ringworld. Image credit: https://bargainbin4u.wordpress.com/2008/07/14/ringworld-by-larry-niven/</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/5b8f60e140ec9ad5c875b0fc/5b8f60e140ec9ad5c875b0fd/1535350325687/ringworld_engineers_by_tomislavtikulin-db0bei8.jpg</image:loc>
      <image:title>Outward Bound - Orbital Rings and Planet Building: Prelude to Colonizing the Solar System</image:title>
      <image:caption>Artist’s depiction of a ring world. Image credit: https://www.deviantart.com/tomislavtikulin/art/Ringworld-Engineers-665659952</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/5b8f60e140ec9ad5c875b0fc/5b8f60e140ec9ad5c875b0ff/1535350338882/halcyon_days_by_julian_faylona-d70cz32.jpg</image:loc>
      <image:title>Outward Bound - Orbital Rings and Planet Building: Prelude to Colonizing the Solar System</image:title>
      <image:caption>Artist’s depiction of a ring world. Image credit: https://www.deviantart.com/julian-faylona/art/Halcyon-Days-423868574</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5b8f60e140ec9ad5c875b0ca/1535355718877/med_bronx4.jpg</image:loc>
      <image:title>Outward Bound - Orbital Rings and Planet Building: Prelude to Colonizing the Solar System</image:title>
      <image:caption>"The inner and outer static orbital rings around Bronx are linked to a central geostationary ring by by carbon nanotube cables. The inner ring is only 265km above the clouds, while the outer ring is 75,600km from the planet's core."\(^{[19]}\) Image from Steve Bowers.</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/5b8f60e140ec9ad5c875b0f8/5b8f60e140ec9ad5c875b0f9/1535351435005/shell_world_by_johnmalcolm1970.jpg</image:loc>
      <image:title>Outward Bound - Orbital Rings and Planet Building: Prelude to Colonizing the Solar System</image:title>
      <image:caption>Artist’s depiction of atlas towers connecting two separate shells in a shell world. Image credit: https://www.deviantart.com/johnmalcolm1970/art/Shell-World-114062545</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5b8f60e140ec9ad5c875b0aa/1535609875282/final-frontier.jpg</image:loc>
      <image:title>Outward Bound - Orbital Rings and Planet Building: Prelude to Colonizing the Solar System</image:title>
      <image:caption>Final Frontier Voyager (2007), George Grie. Óleo sobre lienzo.\(^{[13]}\)Credit: https://commons.wikimedia.org/wiki/File:Final-Frontier.jpg</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5b8f60e140ec9ad5c875b122/1535415737889/677_gas_interiors%5B1%5D.jpg</image:loc>
      <image:title>Outward Bound - Orbital Rings and Planet Building: Prelude to Colonizing the Solar System</image:title>
      <image:caption>Illustration showing the rocky, icy, metallic cores of the four Jovian planets. Credit: NASA/Lunar and Planetary Institute Retrieved from: https://solarsystem.nasa.gov/resources/677/gas-giant-interiors-2003/</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5b8f60e140ec9ad5c875b0ec/1535738151212/Kepler_spacecraft_artist_render_%28crop%29%5B1%5D.jpg</image:loc>
      <image:title>Outward Bound - Orbital Rings and Planet Building: Prelude to Colonizing the Solar System</image:title>
      <image:caption>Artist's conception of the Kepler Space Telescope.</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/5b8f60e140ec9ad5c875b0f0/5b8f60e140ec9ad5c875b0f1/1535356149316/espen-saetervik-rings.jpg</image:loc>
      <image:title>Outward Bound - Orbital Rings and Planet Building: Prelude to Colonizing the Solar System</image:title>
      <image:caption>Artist’s depiction of hoop worlds (also known as ring worlds). These megastructures can be built by building many adjacent orbital rings next to each other, side by side, and laying a surface down over those orbital rings. Image retrieved from https://www.iamag.co/espen-olsen-saetervik/espen-saetervik-rings/</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5b8f60e140ec9ad5c875b088/1535354571685/img_index_01.jpg</image:loc>
      <image:title>Outward Bound - Orbital Rings and Planet Building: Prelude to Colonizing the Solar System</image:title>
      <image:caption>"Since ancient times, people have always dreamed of going to space. Only astronauts have been able to go until now, but progress has been made on efforts to enable even private citizens to experience space, and space travel is finally about to become an industry. Shimizu foresaw the era of space travel early on, and has proposed a space hotel concept."\(^{[4]}\)</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5b8f60e140ec9ad5c875b0a8/1535568397254/13220830_239617033095862_8671672187626094751_n%5B1%5D.jpg</image:loc>
      <image:title>Outward Bound - Orbital Rings and Planet Building: Prelude to Colonizing the Solar System</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/5b8f60e140ec9ad5c875b06e/5b8f60e140ec9ad5c875b06f/1535427182885/espen-saetervik-rings%5B2%5D.jpg</image:loc>
      <image:title>Outward Bound - Orbital Rings and Planet Building: Prelude to Colonizing the Solar System</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5b8f60e140ec9ad5c875b0cc/1535309001976/Stanford_Torus_interior+highhd.jpg</image:loc>
      <image:title>Outward Bound - Orbital Rings and Planet Building: Prelude to Colonizing the Solar System</image:title>
      <image:caption>Artist's depiction of the interior of a Stanford torus. Painted by Donald E. Davis.</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/5b8f60e140ec9ad5c875b12a/5b8f60e140ec9ad5c875b12d/1535827892994/gateway_hub_04_by_lorddoomhammer-d9u3226.png</image:loc>
      <image:title>Outward Bound - Orbital Rings and Planet Building: Prelude to Colonizing the Solar System</image:title>
      <image:caption>Artist’s scifi depiction of a galactic empire using portals to travel across space.\(^{[30]}\) Image credit: https://www.deviantart.com/lorddoomhammer/art/Galactic-Network-594726702</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/5b8f60e140ec9ad5c875b12a/5b8f60e140ec9ad5c875b12b/1535827901771/hades__star___warp_lane_hub_by_gabriel_bs-db8y989.png</image:loc>
      <image:title>Outward Bound - Orbital Rings and Planet Building: Prelude to Colonizing the Solar System</image:title>
      <image:caption>“Two hubs that can connect to create a temporary Warp Lane in your system The Warp Lane Hub can be connected to another Hub for one day, for a fixed Hydrogen cost. Once connected, ships can travel between the two end points instantly and without consuming Hydrogen.”\(^{[31]}\) Image credit: https://www.deviantart.com/gabrielbstiernstrom/art/Hades-Star-Warp-Lane-Hub-680163129</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/5b8f60e140ec9ad5c875b0c0/5b8f60e140ec9ad5c875b0c1/1535355566180/1492030052266.jpg</image:loc>
      <image:title>Outward Bound - Orbital Rings and Planet Building: Prelude to Colonizing the Solar System</image:title>
      <image:caption>Artist’s depiction of an orbital ring.</image:caption>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/space-transportation</loc>
    <changefreq>daily</changefreq>
    <priority>0.75</priority>
    <lastmod>2018-08-17</lastmod>
  </url>
  <url>
    <loc>https://www.gregschool.org/space-transportation/2017/6/28/8fldcv2rgvjvjwb42w67qh0ude4ii0</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-09</lastmod>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59dd396429f1872f5a463699/1534475664383/space+travela+nd+colonization+thumbnail.jpg</image:loc>
      <image:title>Space Transportation - Alcubierre Warp Drive</image:title>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/space-transportation/2017/8/13/nuclear-fusion-engines</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-11</lastmod>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59dd246fd55b41029c6b484a/1534475588401/space+travela+nd+colonization+thumbnail.jpg</image:loc>
      <image:title>Space Transportation - Nuclear Fusion Engines</image:title>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/space-transportation/2017/9/21/shkadov-thruster</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2018-06-28</lastmod>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59f919608165f502329be917/1509497981395/facebook+img+thumbnail.jpg</image:loc>
      <image:title>Space Transportation - Megastructures: Shkadov Thrusters</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59f9195210952678f8a11958/1509497981402/email+img+thumbnail.jpg</image:loc>
      <image:title>Space Transportation - Megastructures: Shkadov Thrusters</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59ebd617268b9699fe3844c0/1509497981406/Shkadov_diagram.jpg</image:loc>
      <image:title>Space Transportation - Megastructures: Shkadov Thrusters</image:title>
      <image:caption>Figure 1: An arc mirror (dark orange arc) subtended by an angle \(2\phi\) reflects a star's radiation back towards itself. Photons collide against the portion of the star's surface which is subtended by the angle \(2\phi\). These collisions result in a net force \(\vec{F}\) exerted on the star causing the entire star to move in the direction of the arrow. The star's gravity pulls everything else in the star system along with it.</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59f91bdf4192021625efc477/1509497981404/space+travela+nd+colonization+thumbnail.png</image:loc>
      <image:title>Space Transportation - Megastructures: Shkadov Thrusters</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59ebccc47131a59c37b07cb4/1509497981409/neil-blevins-megastructures-5-shkadov-thruster-design-packet.jpg</image:loc>
      <image:title>Space Transportation - Megastructures: Shkadov Thrusters</image:title>
      <image:caption>Figure 2: Artist's depiction of a Shkadov thruster. Credit: https://www.artstation.com/artofsoulburn</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59f91a6ce2c48325471de5a0/1509497981393/share+img+for+spacetrav+and+col+thumbnail.png</image:loc>
      <image:title>Space Transportation - Megastructures: Shkadov Thrusters</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59f91985ec212d39ca0ab20e/1509497981397/twiiter+img+thumbnail.jpg</image:loc>
      <image:title>Space Transportation - Megastructures: Shkadov Thrusters</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59f919716c3194e9a685663b/1509497981400/google+img+thumbnail.jpg</image:loc>
      <image:title>Space Transportation - Megastructures: Shkadov Thrusters</image:title>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/space-transportation/2018/6/12/01kbzrqg971y7cr7mw0lgnob5i1y43-6kjrd</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2018-06-28</lastmod>
  </url>
  <url>
    <loc>https://www.gregschool.org/black-holes-summary</loc>
    <changefreq>daily</changefreq>
    <priority>0.75</priority>
    <lastmod>2017-07-01</lastmod>
  </url>
  <url>
    <loc>https://www.gregschool.org/new-blog-5</loc>
    <changefreq>daily</changefreq>
    <priority>0.75</priority>
    <lastmod>2017-07-13</lastmod>
  </url>
  <url>
    <loc>https://www.gregschool.org/new-blog-76</loc>
    <changefreq>daily</changefreq>
    <priority>0.75</priority>
    <lastmod>2017-09-06</lastmod>
  </url>
  <url>
    <loc>https://www.gregschool.org/new-blog-76/2017/8/10/introduction-to-einsteins-general-theory-of-relativity</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-09</lastmod>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/598c16d46a49636f703b3191/1504673164151/Starshot.png</image:loc>
      <image:title>General Relativity - Introduction to Einstein's General Theory of Relativity</image:title>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/new-blog-76/2017/8/10/einstein-equivalence-principle</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-09</lastmod>
  </url>
  <url>
    <loc>https://www.gregschool.org/new-blog-31</loc>
    <changefreq>daily</changefreq>
    <priority>0.75</priority>
    <lastmod>2018-07-19</lastmod>
  </url>
  <url>
    <loc>https://www.gregschool.org/new-blog-31/2017/6/16/overview-of-calculus-hmtnx-fptl9</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-09</lastmod>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a01f94053450a989d5a57f2/1497934508324/</image:loc>
      <image:title>Overview of calculus - Overview of Single-Variable Calculus</image:title>
      <image:caption>Figure 2</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a01f93f53450a989d5a57ed/1507581121093/Untitled.jpg</image:loc>
      <image:title>Overview of calculus - Overview of Single-Variable Calculus</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a01f94053450a989d5a57f6/1497933573517/</image:loc>
      <image:title>Overview of calculus - Overview of Single-Variable Calculus</image:title>
      <image:caption>Figure 4</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a01f94053450a989d5a57f8/1497933579348/</image:loc>
      <image:title>Overview of calculus - Overview of Single-Variable Calculus</image:title>
      <image:caption>Figure 5</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a01f94053450a989d5a57f4/1497931192368/</image:loc>
      <image:title>Overview of calculus - Overview of Single-Variable Calculus</image:title>
      <image:caption>Figure 3</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a01f94053450a989d5a57f0/1497934480889/</image:loc>
      <image:title>Overview of calculus - Overview of Single-Variable Calculus</image:title>
      <image:caption>Figure 1</image:caption>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/new-blog-78</loc>
    <changefreq>daily</changefreq>
    <priority>0.75</priority>
    <lastmod>2017-09-06</lastmod>
  </url>
  <url>
    <loc>https://www.gregschool.org/new-blog-78/2017/8/10/introduction-to-linear-momentum</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-09</lastmod>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59dbf25d18b27de5f10403e9/1507586657951/gfnf.jpg</image:loc>
      <image:title>Momentum - Introduction to Linear Momentum</image:title>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/new-blog-78/2017/8/10/derivation-on-momentum-conservation</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-09</lastmod>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59dbf3088a02c75c23e4b539/1507586829847/gfnf.jpg</image:loc>
      <image:title>Momentum - Derivation of Momentum Conservation</image:title>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/new-blog-78/2017/8/10/inelastic-collisions</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-10</lastmod>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59dbf3af64b05fea9d3ca96c/1507586994321/gfnf.jpg</image:loc>
      <image:title>Momentum - Inelastic Collisions</image:title>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/overview-of-physics</loc>
    <changefreq>daily</changefreq>
    <priority>0.75</priority>
    <lastmod>2017-09-06</lastmod>
  </url>
  <url>
    <loc>https://www.gregschool.org/overview-of-physics/2017/5/14/introduction-to-newtonian-mechanics</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-09</lastmod>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59dac3f92278e744bbca7672/1507509247062/stock-vector-physics-and-science-icons-set-classical-mechanics-397461406.jpg</image:loc>
      <image:title>Overview of Physics - Introduction to Physics and the Scientific Method</image:title>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/overview-of-physics/2017/5/18/what-do-we-mean-by-kinematics-dynamics-and-mechanics</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-09</lastmod>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59dac5f6edaed84653190072/1507509756584/classical+mechanics+thumbnail.jpg</image:loc>
      <image:title>Overview of Physics - What do we mean by "kinematics," "dynamics," and "mechanics?"</image:title>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/overview-of-physics/2017/6/21/the-abstract-has-a-lot-to-say-about-the-physical-world</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-09</lastmod>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59dac64390bade192a01a33c/1507509840450/classical+mechanics+thumbnail.jpg</image:loc>
      <image:title>Overview of Physics - The Abstract has a lot to say about the Physical World</image:title>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/new-blog-73</loc>
    <changefreq>daily</changefreq>
    <priority>0.75</priority>
    <lastmod>2017-09-09</lastmod>
  </url>
  <url>
    <loc>https://www.gregschool.org/new-blog-73/2017/6/12/p-series-convergence-and-divergence</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-09</lastmod>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/593f64108419c276ef637188/1497326618764/</image:loc>
      <image:title>Series - P-Series Convergence and Divergence</image:title>
      <image:caption>Figure 1 (click to enlarge)</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59dbde8564b05fea9d3b6371/1507581577144/Untitled.jpg</image:loc>
      <image:title>Series - P-Series Convergence and Divergence</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/593f63cfbf629a891ee6c94b/1497326554506/</image:loc>
      <image:title>Series - P-Series Convergence and Divergence</image:title>
      <image:caption>Figure 2 (click to enlarge)</image:caption>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/new-blog-73/2017/8/16/maclaurin-polynomial-and-series</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2018-07-06</lastmod>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59dbdff14c0dbffb014aa46a/1507581942436/Untitled.jpg</image:loc>
      <image:title>Series - Maclaurin/Taylor Polynomials and Series</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59add11437c581dc3568a902/1504985107253/Exp_series.gif</image:loc>
      <image:title>Series - Maclaurin/Taylor Polynomials and Series</image:title>
      <image:caption>Figure 1. Maclaurin polynomials of different order \(n\) (red curves) approximating the function \(e^x\) (blue curve).</image:caption>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/astronomy</loc>
    <changefreq>daily</changefreq>
    <priority>0.75</priority>
    <lastmod>2018-07-19</lastmod>
  </url>
  <url>
    <loc>https://www.gregschool.org/astronomy/2017/10/29/quasars</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2018-07-20</lastmod>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59fe2251084665ad8a56cb82/1509827914262/share+technology++img.jpg</image:loc>
      <image:title>Astronomy - Quasars</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59fded47e31d1945636849d4/1509827914278/PIA13033%5B1%5D.jpg</image:loc>
      <image:title>Astronomy - Quasars</image:title>
      <image:caption>Figure 1: "The 200-inch (5.1 m) Hale Telescope (f/3.3) was the world's largest effective telescope for 45 years (1948-1993). It is still a workhorse of modern astronomy. It is used nightly for a wide range of astronomical studies. On average the weather allows for at least some data collection about 290 nights a year."\(^{[1]}\) Image credit: Caltech/Palomar Observatory</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59fe2165e31d1945636e00b9/1509827914269/twiiter+img+thumbnail.jpg</image:loc>
      <image:title>Astronomy - Quasars</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59fe214a24a6943fd0cb7e59/1509827914266/facebook+img+thumbnail.jpg</image:loc>
      <image:title>Astronomy - Quasars</image:title>
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    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59fe217364265f6a40130891/1509827914271/google+img+thumbnail.jpg</image:loc>
      <image:title>Astronomy - Quasars</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59fdfee10852295261a453d8/1509827914285/Quasar%5B1%5D.png</image:loc>
      <image:title>Astronomy - Quasars</image:title>
      <image:caption>Figure 4: Illustration of the various different components of a quasar.\(^{[4]}\) Image credit: Futurism.</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59fe211fe2c483f6d0418c71/1509827914276/astronomy+and+cosmology+thumbnail.png</image:loc>
      <image:title>Astronomy - Quasars</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59fdf9c353450a448c6deb43/1509827914282/Best_image_of_bright_quasar_3C_273%5B1%5D.jpg</image:loc>
      <image:title>Astronomy - Quasars</image:title>
      <image:caption>Figure 3: "This image from Hubble’s Wide Field and Planetary Camera 2 (WFPC2) is likely the best of ancient and brilliant quasar 3C 273, which resides in a giant elliptical galaxy in the constellation of Virgo (The Virgin). Its light has taken some 2.5 billion years to reach us. Despite this great distance, it is still one of the closest quasars to our home. It was the first quasar ever to be identified, and was discovered in the early 1960s by astronomer Allan Sandage. The term quasar is an abbreviation of the phrase “quasi-stellar radio source”, as they appear to be star-like on the sky. In fact, quasars are the intensely powerful centres of distant, active galaxies, powered by a huge disc of particles surrounding a supermassive black hole. As material from this disc falls inwards, some quasars — including 3C 273 — have been observed to fire off super-fast jets into the surrounding space. In this picture, one of these jets appears as a cloudy streak, measuring some 200 000 light-years in length. Quasars are capable of emitting hundreds or even thousands of times the entire energy output of our galaxy, making them some of the most luminous and energetic objects in the entire Universe. Of these very bright objects, 3C 273 is the brightest in our skies. If it was located 30 light-years from our own planet — roughly seven times the distance between Earth and Proxima Centauri, the nearest star to us after the Sun — it would still appear as bright as the Sun in the sky. WFPC2 was installed on Hubble during shuttle mission STS-125. It is the size of a small piano and was capable of seeing images in the visible, near-ultraviolet, and near-infrared parts of the spectrum."\(^{[3]}\) Image Credit: ESA/Hubble [CC BY 4.0 (http://creativecommons.org/licenses/by/4.0)], via Wikimedia Commons</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59fe2131e31d1945636dfb00/1509827914273/email+img+thumbnail.jpg</image:loc>
      <image:title>Astronomy - Quasars</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59fdf4d5e4966b0f25678cd5/1509827914280/3C273z%5B1%5D.gif</image:loc>
      <image:title>Astronomy - Quasars</image:title>
      <image:caption>Figure 2: "The spectrum of the quasar 3C 273. The strongest emission lines present are Balmer lines of hydrogen, as marked. In each case, the arrow is drawn from the rest wavelength to the observed wavelength of the line— shifted redward in each case by 15.8%. The other emission lines apparent in the spectrum are due to oxygen, helium, iron, and other elements. Credit: Michael A. Strauss, from data taken by the New Technology Telescope at La Silla, Chile; M. Türler et al. 2006, Astronomy and Astrophysics 451: L1– L4, http:// isdc.unige.ch/ 3c273/# emmi, http:// casswww.ucsd.edu/ archive/ public/ tutorial/ images/ 3C273z.gif Tyson, Neil deGrasse; Strauss, Michael A.; Gott, J. Richard. Welcome to the Universe: An Astrophysical Tour (p. 242). Princeton University Press. Kindle Edition."\(^{[2]}\)</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59fdf333f9619a429181a1e6/1509827914286/orangepie%5B1%5D.jpg</image:loc>
      <image:title>Astronomy - Quasars</image:title>
      <image:caption>Figure 5: A 3-d map obtained by the Sloan Digital Survey of billions of light years of our local universe. Each dot is an entire galaxy and this survey shows millions of them. As you can see from this image, on the scale of billions of light-years the galaxies of congregated into a "web"-like structure of filaments and strands known as the cosmic web. Image Credit: M. Blanton and SDSS</image:caption>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/astronomy/2018/6/20/the-diversity-of-exoplanets-in-the-galaxy-me459-3nb2d</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2018-07-20</lastmod>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5b5120def950b7b766e34d77/1531966283722/astronomy+and+cosmology+thumbnail.png</image:loc>
      <image:title>Astronomy - The Diversity of Exoplanets in the Galaxy</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5b5120def950b7b766e34d87/1530132981476/Planets_everywhere_%28artist%E2%80%99s_impression%29%5B1%5D.jpg</image:loc>
      <image:title>Astronomy - The Diversity of Exoplanets in the Galaxy</image:title>
      <image:caption>"This artist's cartoon view gives an impression of how common planets are around the stars in the Milky Way. The planets, their orbits and their host stars are all vastly magnified compared to their real separations. A six-year search that surveyed millions of stars using the microlensing technique concluded that planets around stars are the rule rather than the exception. The average number of planets per star is greater than one."\(^{[1]}\) Image credit: by ESO/M. Kornmesser (http://www.eso.org/public/images/eso1204a/) [CC BY 4.0 (https://creativecommons.org/licenses/by/4.0)], via Wikimedia Commons</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5b5120def950b7b766e34d8f/1530042426129/aHR0cDovL3d3dy5zcGFjZS5jb20vaW1hZ2VzL2kvMDAwLzAzOC81ODAvb3JpZ2luYWwva2VwbGVyLTE4NmYtYXJ0LmpwZz8xMzk3Njg3MTkw%5B1%5D.jpg</image:loc>
      <image:title>Astronomy - The Diversity of Exoplanets in the Galaxy</image:title>
      <image:caption>Artist's impression of the Archipelago world, Kepler 186f. Credit: Danielle Futselaar</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5b5120def950b7b766e34d6f/1531966586224/facebook+img+thumbnail.jpg</image:loc>
      <image:title>Astronomy - The Diversity of Exoplanets in the Galaxy</image:title>
    </image:image>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5b5120def950b7b766e34d79/1531960026632/10629328_1041033252591158_1987130945153076812_o.jpg</image:loc>
      <image:title>Astronomy - The Diversity of Exoplanets in the Galaxy</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5b5120def950b7b766e34d93/1530306062728/PIA21061-Pluto-DwarfPlanet-XRays-20160914%5B1%5D.jpg</image:loc>
      <image:title>Astronomy - The Diversity of Exoplanets in the Galaxy</image:title>
      <image:caption>X-ray image of Pluto obtained by Chandra X-Ray Observatory (blue spot on right) and up-close photograph of Pluto obtained by the spacecraft Deep Horizons as it flew by Pluto.</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5b5120def950b7b766e34d8d/1530138555487/maxresdefault.jpg</image:loc>
      <image:title>Astronomy - The Diversity of Exoplanets in the Galaxy</image:title>
      <image:caption>Image of auroras just above the Earth's surface obtained by the International Space Station. Image credit: NASA</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5b5120def950b7b766e34d89/1530305727092/aHR0cDovL3d3dy5zcGFjZS5jb20vaW1hZ2VzL2kvMDAwLzA1My8yNjkvb3JpZ2luYWwvc3VwZXItZWFydGgtY2FuY3JpLTU1LWUuanBn%5B1%5D.jpg</image:loc>
      <image:title>Astronomy - The Diversity of Exoplanets in the Galaxy</image:title>
      <image:caption>Artist's depiction of the exoplanet 55 Cancri E. Image credit: ESA/Hubble [CC BY 4.0 (https://creativecommons.org/licenses/by/4.0)], via Wikimedia Commons.</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5b5120def950b7b766e34d97/1530743975575/trappist.png</image:loc>
      <image:title>Astronomy - The Diversity of Exoplanets in the Galaxy</image:title>
      <image:caption>This artist's concept shows what the TRAPPIST-1 planetary system may look like, based on available data about the planets' diameters, masses and distances from the host star. Credits: NASA/JPL-Caltech View full image and caption</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5b5120def950b7b766e34d91/1530047402295/1920px-Kepler186f-ComparisonGraphic-20140417%5B1%5D.jpg</image:loc>
      <image:title>Astronomy - The Diversity of Exoplanets in the Galaxy</image:title>
      <image:caption>Size comparison of Kepler-186f (artist's impression) with Earth along with their projected habitable zones.</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5b5120def950b7b766e34d73/1531966612320/google+img+thumbnail.jpg</image:loc>
      <image:title>Astronomy - The Diversity of Exoplanets in the Galaxy</image:title>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5b5120def950b7b766e34d6d/1531966550594/share+astronomy+and+cosmology+img.png</image:loc>
      <image:title>Astronomy - The Diversity of Exoplanets in the Galaxy</image:title>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/5b5120def950b7b766e34d7b/5b5120def950b7b766e34d80/1530135817506/PIA19656-SaturnMoon-Enceladus-Ocean-ArtConcept-20150915%5B2%5D.jpg</image:loc>
      <image:title>Astronomy - The Diversity of Exoplanets in the Galaxy</image:title>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/5b5120def950b7b766e34d7b/5b5120def950b7b766e34d7c/1530135242345/PIA19058-SaturnMoon-Enceladus-PossibleHydrothermalActivity-ArtistConcept-20150311%5B2%5D.jpg</image:loc>
      <image:title>Astronomy - The Diversity of Exoplanets in the Galaxy</image:title>
      <image:caption>Artists impressions of subsurface oceans underneath thick ice sheets on Jupiter’s moon Europa and Saturn’s moon Enceladus. Top image by NASA.</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/5b5120def950b7b766e34d7b/5b5120def950b7b766e34d7e/1530133614272/image_4610_3e-Europa-Lander%5B1%5D.jpg</image:loc>
      <image:title>Astronomy - The Diversity of Exoplanets in the Galaxy</image:title>
      <image:caption />
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5b5120def950b7b766e34d8b/1530236766508/Graphite-and-diamond-with-scale%5B1%5D.jpg</image:loc>
      <image:title>Astronomy - The Diversity of Exoplanets in the Galaxy</image:title>
      <image:caption>Graphite (left) and diamond (right) are both, essentially, just made up of a bunch of carbon atoms. The difference between the two substances is how those carbon atoms are arranged.</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5b5120def950b7b766e34d75/1531966570270/email+img+thumbnail.jpg</image:loc>
      <image:title>Astronomy - The Diversity of Exoplanets in the Galaxy</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5b5120def950b7b766e34d85/1529888319405/aHR0cDovL3d3dy5zcGFjZS5jb20vaW1hZ2VzL2kvMDAwLzA2Mi8wODkvb3JpZ2luYWwvaG90LWp1cGl0ZXItY29uY2VwdGlvbi5qcGc%3D%5B1%5D.jpg</image:loc>
      <image:title>Astronomy - The Diversity of Exoplanets in the Galaxy</image:title>
      <image:caption>Artist's depiction of a so-called hot Jupiter orbiting its planet star.</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5b5120def950b7b766e34d71/1531966632845/twiiter+img+thumbnail.jpg</image:loc>
      <image:title>Astronomy - The Diversity of Exoplanets in the Galaxy</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5b5120def950b7b766e34d95/1531960599987/2159_TRAPPIST-1e_1200_preview%5B1%5D.jpg</image:loc>
      <image:title>Astronomy - The Diversity of Exoplanets in the Galaxy</image:title>
      <image:caption>This poster imagines what a trip to TRAPPIST-1e might be like. Credits: NASA/JPL-Caltech View full image</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5b5120def950b7b766e34d83/1531436786142/pular+planet.png</image:loc>
      <image:title>Astronomy - The Diversity of Exoplanets in the Galaxy</image:title>
      <image:caption>Artist's conception of a planet orbiting a Pulsar. The Pulsar's radiation blasting the exoplanet would cause its surface to glow.</image:caption>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/astronomy/2017/6/16/formation-of-planets-and-stars-xa5hw-2rxlj</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2018-07-20</lastmod>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59ffc275652dea4f72000cb4/1498157418533/mwpan_aitoff_s.jpg</image:loc>
      <image:title>Astronomy - A Brief Tour of our Milky Way Galaxy</image:title>
      <image:caption>Picture of the Milky Way Galaxy as seen edge on.</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59ffc275652dea4f72000cb8/1498195183058/430453main_crabmosaic_hst_big_full.jpg</image:loc>
      <image:title>Astronomy - A Brief Tour of our Milky Way Galaxy</image:title>
      <image:caption>Image of Crab Nebula. (Image credit: NASA)</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59ffc275652dea4f72000cb2/1498195845727/</image:loc>
      <image:title>Astronomy - A Brief Tour of our Milky Way Galaxy</image:title>
      <image:caption>Artist's depiction of the Milky Way Galaxy.</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59ffc275652dea4f72000cb6/1498193304895/</image:loc>
      <image:title>Astronomy - A Brief Tour of our Milky Way Galaxy</image:title>
      <image:caption>Inferred image of the center of the Milky Way Galaxy. (Source)</image:caption>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/astronomy/2017/11/14/drakes-equation-d4hkm-bs6gg</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2018-07-20</lastmod>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5b5121706d2a73943bc49b51/1531967526142/</image:loc>
      <image:title>Astronomy - Drake's Equation and Searching for Life in the Milky Way</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5b5121706d2a73943bc49b69/1510874927808/Kepler_spacecraft_artist_render_%28crop%29%5B1%5D.jpg</image:loc>
      <image:title>Astronomy - Drake's Equation and Searching for Life in the Milky Way</image:title>
      <image:caption>Artist's depiction of the Kepler space telescope.</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/5b5121706d2a73943bc49b6d/5b5121706d2a73943bc49b70/1510875294374/HT-trappist-1-star-surface-3-jt-170221_4x3_992%5B1%5D.jpg</image:loc>
      <image:title>Astronomy - Drake's Equation and Searching for Life in the Milky Way</image:title>
      <image:caption>Imagine standing on the surface of the exoplanet TRAPPIST-1f. This artist's concept is one interpretation of what it could look like.</image:caption>
    </image:image>
    <image:image>
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      <image:title>Astronomy - Drake's Equation and Searching for Life in the Milky Way</image:title>
      <image:caption>"This artist’s impression shows a view of the surface of the planet Proxima b orbiting the red dwarf star Proxima Centauri, the closest star to the solar system. The double star Alpha Centauri AB also appears in the image. Proxima b is a little more massive than the Earth and orbits in the habitable zone around Proxima Centauri, where the temperature is suitable for liquid water to exist on its surface."\(^{[1]}\) https://www.nasa.gov/feature/jpl/eso-discovers-earth-size-planet-in-habitable-zone-of-nearest-star Credits: ESO/M. Kornmesser</image:caption>
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      <image:title>Astronomy - Drake's Equation and Searching for Life in the Milky Way</image:title>
      <image:caption>"Mr. Spock (Leonard Nimoy), communicating with the Horta through a Vulcan mind meld."\(^{[3]}\)</image:caption>
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      <image:title>Astronomy - Drake's Equation and Searching for Life in the Milky Way</image:title>
      <image:caption>An artist's depiction of the starship proposed by Project Daedalus.\(^{[5]}\)</image:caption>
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      <image:title>Astronomy - Drake's Equation and Searching for Life in the Milky Way</image:title>
      <image:caption>Artist's depiction of an exoplanet crossing our line of sight in front of its home-star.</image:caption>
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      <image:title>Astronomy - Drake's Equation and Searching for Life in the Milky Way</image:title>
      <image:caption>A Hunter "A speculative hunter animal evolved in the atmosphere of a gas-giant planet. Developed for Cosmos, Episode 2."\(^{[4]}\) Image by Adolf Schaller.</image:caption>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/5b5121706d2a73943bc49b5b/5b5121706d2a73943bc49b5c/1510878250166/20131102_cosmos-episode-2-hfs-herd-of-floaters%5B1%5D.jpg</image:loc>
      <image:title>Astronomy - Drake's Equation and Searching for Life in the Milky Way</image:title>
      <image:caption>A Lazy Herd of Floaters "An updated digital restoration by Adolf Schaller of detail in his original Hunters, Floaters, Sinkers mural which appeared on Cosmos, Episode 2, which speculates about life in the atmosphere of a gas-giant planet."\(^{[4]}\) Image by Adolf Schaller.</image:caption>
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      <image:title>Astronomy - Drake's Equation and Searching for Life in the Milky Way</image:title>
      <image:caption>A "Floater" from Cosmos, Episode 2 "Part of the larger mural, "Hunters, Floaters, and Sinkers" painted for the series."\(^{[4]}\) Image by Adolf Schaller.</image:caption>
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      <image:title>Astronomy - Drake's Equation and Searching for Life in the Milky Way</image:title>
      <image:caption>Hunters, Floaters, and Sinkers "This painting speculates about possible forms of life on a Jupiter-like gas giant. Airbrushed water-based acrylic."\(^{[4]}\) Image by Adolf Schaller.</image:caption>
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      <image:title>Astronomy - Drake's Equation and Searching for Life in the Milky Way</image:title>
      <image:caption>Artist's depiction of an exoplanet orbiting a pulsar. Due to the pulsar's radiation, the exoplanet glows.</image:caption>
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      <image:title>Astronomy - Drake's Equation and Searching for Life in the Milky Way</image:title>
      <image:caption>The habitable zone is a range of orbital distances (between an exoplanet and the star it orbits) where the planet is neither too hot nor too cold. This is also sometimes called the Goldilocks zone. In order for a planet to be truly "Earth-like," it must also have a mass 1-2 times that of the Earth, have an atmosphere, and orbit in a stable elliptical orbit that is not too essentric.</image:caption>
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  <url>
    <loc>https://www.gregschool.org/articles-page-3</loc>
    <changefreq>daily</changefreq>
    <priority>0.75</priority>
    <lastmod>2019-03-23</lastmod>
  </url>
  <url>
    <loc>https://www.gregschool.org/articles-page-3/2017/5/4/chaos</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-09</lastmod>
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      <image:title>Articles page 3 - Chaos and Fractals</image:title>
      <image:caption>Figure 3: After rolling the dice (and drawing a new point for each dice roll) billions of times, a fractal pattern known as the Siepinski triangle will eventually form. Remarkable! Image credit: by Beojan Stanislaus (Own work) [CC BY-SA 3.0 (https://creativecommons.org/licenses/by-sa/3.0)], via Wikimedia Commons.</image:caption>
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      <image:title>Articles page 3 - Chaos and Fractals</image:title>
      <image:caption>Figure 1: "Edward Norton Lorenz (May 23, 1917 – April 16, 2008) was an American mathematician, meteorologist, and a pioneer of chaos theory, along with Mary Cartwright. He introduced the strange attractor notion and coined the term butterfly effect."\(^{[3]}\) This image is for educational purposes only. Image credit: https://history.aip.org/history/Thumbnails/lorenz_edward_a1.jpg</image:caption>
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      <image:caption>Figure 4: An image of the Cantor set.</image:caption>
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      <image:title>Articles page 3 - Chaos and Fractals</image:title>
      <image:caption>Figure 2: The three points \((1,2)\), \((3,4)\), and \((5,6)\) form an equilateral triangle. Choose any arbitrary point \((x,y)\) anywhere on the plane either inside or outside the triangle. If you rolled a 1 or 2, then draw a new point \((x_0,y_0)\) whose distance is half way between the points \((x,y)\) and \((1,2)\). Repeat this many times.</image:caption>
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  <url>
    <loc>https://www.gregschool.org/articles-page-3/2017/8/21/our-future-as-cyborgs</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-09</lastmod>
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  </url>
  <url>
    <loc>https://www.gregschool.org/articles-page-3/2017/10/30/derivation-of-snells-law-a8sne</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-09</lastmod>
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      <image:title>Articles page 3 - Derivation of Snell's Law</image:title>
      <image:caption>Figure 2: As a light ray travels along the line \(QO\) through medium 1 and comes into contact with the interface between medium 1 and medium 2, it gets refracted—meaning, it passes through medium 2. Image credit: By Smedlib (Own work) [CC BY-SA 4.0 (https://creativecommons.org/licenses/by-sa/4.0)], via Wikimedia Commons</image:caption>
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      <image:title>Articles page 3 - Derivation of Snell's Law</image:title>
      <image:caption>Figure 1: A light ray traveling along the line \(QO\) comes into contact with a surface at an \(θ_i\) (where \(θ_i\) is measured relative to the line perpendicular to the surface). Once this light ray comes into contact with this surface, it is reflected at an angle \(θ_r\) (\(θ_r\) is also measured relative to the perpendicular). According to the law of reflection, \(θ_i=θ_r\). Image credit: Download for free at http://cnx.org/contents/60b4727b-829e-4ea7-9238-9140b6a1b20c@4.</image:caption>
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  </url>
  <url>
    <loc>https://www.gregschool.org/articles-page-3/2017/9/21/shkadov-thruster-ljar4</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2018-06-28</lastmod>
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      <image:title>Articles page 3 - Megastructures: Shkadov Thrusters</image:title>
      <image:caption>Figure 2: Artist's depiction of a Shkadov thruster. Credit: https://www.artstation.com/artofsoulburn</image:caption>
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      <image:caption>Figure 1: An arc mirror (dark orange arc) subtended by an angle \(2\phi\) reflects a star's radiation back towards itself. Photons collide against the portion of the star's surface which is subtended by the angle \(2\phi\). These collisions result in a net force \(\vec{F}\) exerted on the star causing the entire star to move in the direction of the arrow. The star's gravity pulls everything else in the star system along with it.</image:caption>
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  </url>
  <url>
    <loc>https://www.gregschool.org/articles-page-3/2017/9/11/harvesting-resources-from-saturn-and-titan-l5msz</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-09</lastmod>
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      <image:title>Articles page 3 - Harvesting Resources from Saturn and Titan</image:title>
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      <image:caption>"With an average temperature of -180 C all water here is frozen hard as rock. In fact, the surface landscape of Titan is indeed mostly made of frozen water ice. But Titan's atmosphere is rich in hydrocarbons such as methane and ethane, and the low temperature is perfect for these elements to occur naturally in three states; frozen, liquid and gas. So, just as on Earth where we have a water cycle (ice melts, becomes water, water evaporates into clouds, turning into liquid and becomes rain and so forth), Titan has a methane cycle. Methane evaporates and rises to form clouds, eventually turning into rain, falling over the surface. And this is the most amazing part; the rain in some places is enough to fill entire lakes. Lakes of methane! Titan is the only place in the Solar System, other than Earth, known to have large bodies of liquid on its surface. And they are really there, huge lakes, with shorelines, islands and small archipelagos. This scene takes place over a lake know as Ligeia Mare, the second largest on Titan, about 500 kilometers in diameter, located in the north polar region of the moon. The second fantastic feature I wanted to illustrate is the combination of Titan's very dense atmosphere and its relatively low gravity. As a human on Titan you would weigh about 14% of what you do on Earth, and in the dense atmosphere it would be enough to strap wings on your arms to make you able to fly like a bird. On Titan you could fly like a bird, over lakes of methane! (If you wore some really warm clothes of course.)" Image and image description credit: WANDERERS - a short film by EriK Wernquist</image:caption>
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  </url>
  <url>
    <loc>https://www.gregschool.org/articles-page-3/2017/10/27/gravitational-force-exerted-by-a-sphere-lm293</loc>
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    <priority>0.5</priority>
    <lastmod>2017-11-09</lastmod>
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      <image:title>Articles page 3 - Gravitational Force Exerted by a Disk</image:title>
      <image:caption>Figure 1: A ring of mass \(M=\int{dm}\) exerts a gravitational force on a particle of mass \(m\) a horizontal distance \(h\) away from the center of the ring. The vertical component of force \(dF_y\) for every mass element \(dm\) in the ring is canceled out by the vertical component of force \(dF'_y\) for another mass element \(dm'\) located on the opposite side of the ring.</image:caption>
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      <image:title>Articles page 3 - Gravitational Force Exerted by a Disk</image:title>
      <image:caption>Figure 2: A disk of mass \(M=\int{m_{ring}}\) exerts a gravitational force on a particle of mass \(m\) a distance \(h\) away from the center of the disk along the \(x\)-axis. By summing the gravitational force exerted on \(m\) by each ring of radius \(r\) from \(r=0\) to \(r=R\), we can find the total gravitational force exerted on \(m\) by the entire disk.</image:caption>
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  <url>
    <loc>https://www.gregschool.org/articles-page-3/2017/11/2/how-fast-does-water-rise-up-a-cone</loc>
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    <priority>0.5</priority>
    <lastmod>2017-11-09</lastmod>
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      <image:caption>Figure 1: Water being poured into a rectangular box with dimensions \(4ft×4ft×h\) at a rate of \(\frac{dV}{dt}=4\frac{ft^3}{min}\). The container at time \(t=0\) starts out empty.</image:caption>
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      <image:title>Articles page 3 - How Fast Does Water Rise Up a Cone?</image:title>
      <image:caption>Figure 2: Water is poured into a cone of height \(h\) and radius \(r\) at a rate of \(\frac{dV}{dt}=4\frac{ft^3}{min}. The height of the water is given by \(y\). This image was modified under a Create Commons license. Image credit: https://www.mathalino.com/blog/romel-verterra/calculator-technique-solving-volume-flow-rate-problems-calculus</image:caption>
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  <url>
    <loc>https://www.gregschool.org/articles-page-3/2017/10/22/volume-of-an-oblate-spheroid-rl852</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-09</lastmod>
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      <image:caption>Figure 1: Graph of the ellipse \(\frac{x^2}{9}+\frac{y^2}{4}=1\) centered at the origin of the \(xy\)-plane. Also, I have drawn the \(i^{th}\) rectangle underneath the quarter-ellipse within the first quadrant. There are an \(n\) number of such rectangles underneath this quarter-ellipse along the interval \(Δx=3-0\).  </image:caption>
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      <image:caption>Figure 2: A cylindrical shell is obtained by revolving the rectangle \(f(x_i)Δx\) about the \(y\)-axis. Doing this for all \(n\) rectangles, we get an \(n\) number of shells. By summing the volumes of these \(n\) number of cylindrical shells, we can obtain an estimate for total volume enclosed inside of the paraboloid obtained by rotating the quarter-ellipse (the one in the upper-right quadrant) about the \(x\)-axis.</image:caption>
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      <image:caption>Figure 3: If \(a\) and \(c\) represents the semi-major and semi-minor axes of an ellipse, respectively, and if \(a=3\) and \(c=2\) then by rotating such an ellipse about an axis we can obtain an oblate spheroid.</image:caption>
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  <url>
    <loc>https://www.gregschool.org/articles-page-3/2017/10/29/quasars-3xbmj</loc>
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    <priority>0.5</priority>
    <lastmod>2017-11-09</lastmod>
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      <image:caption>Figure 3: "This image from Hubble’s Wide Field and Planetary Camera 2 (WFPC2) is likely the best of ancient and brilliant quasar 3C 273, which resides in a giant elliptical galaxy in the constellation of Virgo (The Virgin). Its light has taken some 2.5 billion years to reach us. Despite this great distance, it is still one of the closest quasars to our home. It was the first quasar ever to be identified, and was discovered in the early 1960s by astronomer Allan Sandage. The term quasar is an abbreviation of the phrase “quasi-stellar radio source”, as they appear to be star-like on the sky. In fact, quasars are the intensely powerful centres of distant, active galaxies, powered by a huge disc of particles surrounding a supermassive black hole. As material from this disc falls inwards, some quasars — including 3C 273 — have been observed to fire off super-fast jets into the surrounding space. In this picture, one of these jets appears as a cloudy streak, measuring some 200 000 light-years in length. Quasars are capable of emitting hundreds or even thousands of times the entire energy output of our galaxy, making them some of the most luminous and energetic objects in the entire Universe. Of these very bright objects, 3C 273 is the brightest in our skies. If it was located 30 light-years from our own planet — roughly seven times the distance between Earth and Proxima Centauri, the nearest star to us after the Sun — it would still appear as bright as the Sun in the sky. WFPC2 was installed on Hubble during shuttle mission STS-125. It is the size of a small piano and was capable of seeing images in the visible, near-ultraviolet, and near-infrared parts of the spectrum."\(^{[3]}\) Image Credit: ESA/Hubble [CC BY 4.0 (http://creativecommons.org/licenses/by/4.0)], via Wikimedia Commons</image:caption>
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      <image:caption>Figure 4: Illustration of the various different components of a quasar.\(^{[4]}\) Image credit: Futurism.</image:caption>
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      <image:caption>Figure 5: A 3-d map obtained by the Sloan Digital Survey of billions of light years of our local universe. Each dot is an entire galaxy and this survey shows millions of them. As you can see from this image, on the scale of billions of light-years the galaxies of congregated into a "web"-like structure of filaments and strands known as the cosmic web. Image Credit: M. Blanton and SDSS</image:caption>
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      <image:caption>Figure 1: "The 200-inch (5.1 m) Hale Telescope (f/3.3) was the world's largest effective telescope for 45 years (1948-1993). It is still a workhorse of modern astronomy. It is used nightly for a wide range of astronomical studies. On average the weather allows for at least some data collection about 290 nights a year."\(^{[1]}\) Image credit: Caltech/Palomar Observatory</image:caption>
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      <image:caption>Figure 2: "The spectrum of the quasar 3C 273. The strongest emission lines present are Balmer lines of hydrogen, as marked. In each case, the arrow is drawn from the rest wavelength to the observed wavelength of the line— shifted redward in each case by 15.8%. The other emission lines apparent in the spectrum are due to oxygen, helium, iron, and other elements. Credit: Michael A. Strauss, from data taken by the New Technology Telescope at La Silla, Chile; M. Türler et al. 2006, Astronomy and Astrophysics 451: L1– L4, http:// isdc.unige.ch/ 3c273/# emmi, http:// casswww.ucsd.edu/ archive/ public/ tutorial/ images/ 3C273z.gif Tyson, Neil deGrasse; Strauss, Michael A.; Gott, J. Richard. Welcome to the Universe: An Astrophysical Tour (p. 242). Princeton University Press. Kindle Edition."\(^{[2]}\)</image:caption>
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  <url>
    <loc>https://www.gregschool.org/articles-page-3/2017/10/22/partial-derivatives-6cjz9</loc>
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    <priority>0.5</priority>
    <lastmod>2017-11-09</lastmod>
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      <image:caption>Figure 1: Graph of the surface \(f(x,y)=x^2+y^2\). Image courtesy of Wolfram Alpha.</image:caption>
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      <image:caption>Figure 2: The entire blue surface is given by the function \(f(x,y)=x^2+y^2\). By letting \(y=1\), we that \(y^2=1\) and \(f(x,1)=x^2+1\) giving us a parabola shifted up one unit along the \(z\)-axis. That is how we can analytically obtain the parabola \(f(x,y)\). We can also obtain \(f(x,1)\) by passing the plane \(y=1\) (illustrated as the black plane above) through the surface \(f(x,y)\). The points at which the two surfaces (the surface \(f(x,y)\) and the plane \(y=1\)) intersect form the red parabola drawn in the image above. Image credit: By IkamusumeFan (Own work) [CC BY-SA 4.0 (https://creativecommons.org/licenses/by-sa/4.0)], via Wikimedia Commons.</image:caption>
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      <image:title>Articles page 3 - Introduction to Partial Derivatives</image:title>
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    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59fe287871c10b5cf3169bc6/1509828608825/twiiter+img+thumbnail.jpg</image:loc>
      <image:title>Articles page 3 - Introduction to Partial Derivatives</image:title>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59fe287871c10b5cf3169bc8/1509828652953/google+img+thumbnail.jpg</image:loc>
      <image:title>Articles page 3 - Introduction to Partial Derivatives</image:title>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/articles-page-4</loc>
    <changefreq>daily</changefreq>
    <priority>0.75</priority>
    <lastmod>2019-03-23</lastmod>
  </url>
  <url>
    <loc>https://www.gregschool.org/articles-page-4/2017/9/27/introduction-to-line-integrals-bywel</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-08</lastmod>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59daa50d2aeba571e4098dbe/1510175532388/sdf.jpg</image:loc>
      <image:title>Articles page 4 - Introduction to Line Integrals</image:title>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59d9a6c0a803bb45f4162a6f/1507432031391/VIBrO.jpg</image:loc>
      <image:title>Articles page 4 - Introduction to Line Integrals</image:title>
      <image:caption>Figure 1: The width and height of each blue rectangle is given by the arc length \(ds\) and the function \(f(x,y)\), respectively. The line integral, \(\int_Cf(x,y)ds\), represents the infinite sum of the area of each blue rectangle along the curve \(C\) (the purple line on the \(xy\)-plane). This image is a derivative work. Original image: https://www.wikihow.com/User:Atheia</image:caption>
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    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59d9a6c0a803bb45f4162a71/1507433707547/fhdhfdg.jpg</image:loc>
      <image:title>Articles page 4 - Introduction to Line Integrals</image:title>
      <image:caption>Figure 2: By the Pythagorean theorem, each infinitesimal arc length \(ds\) can be represented in terms of \(x\) and \(y\) as \(\sqrt{x+2+y^2}\).</image:caption>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/articles-page-4/2017/9/30/solving-problems-using-line-integrals-z8s7t</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-08</lastmod>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59dabac5e5dd5b959940473e/1507491891563/156px-Circular_cylinder_rh.jpg</image:loc>
      <image:title>Articles page 4 - Solving Problems using Line Integrals</image:title>
      <image:caption>Figure 1: A cylinder with height \(h=2\) and radius \(r=1\). The "top" and "bottom" pieces of the cylinder are removed.</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59dabac5e5dd5b9599404740/1507147436235/Untitled.jpg</image:loc>
      <image:title>Articles page 4 - Solving Problems using Line Integrals</image:title>
      <image:caption>Figure 2: A proton \(P_2\) seperated by an initil seperation distance \(r_0\) from a station proton \(P_1\) moves along an arbitrary path until it reaches a seperation distance of \(r\). According to Column's law, the proton \(P_1\) will exert an electric force and, hence, also do work on the proton \(P_2\) as it moves from \(r_0\) to \(r\). The electric force forms a vector field and by calculuating the line integral along \(P_2\)'s path, we can calculate the amount of work done on \(P_2\).</image:caption>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59dabac5e5dd5b9599404742/1506906635307/main-qimg-ef54da6034b7e89fb771a40923f089ca.gif</image:loc>
      <image:title>Articles page 4 - Solving Problems using Line Integrals</image:title>
      <image:caption>Figure 3: A mass \(m\) is attached to the end of a rope of length \(L\). The mass falls and travels a distance \(s\) with a total angular displacement of \(θ\).</image:caption>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59dabac5e5dd5b959940473c/1507502227235/sdfsdfdsdfdfdf+october+8.jpg</image:loc>
      <image:title>Articles page 4 - Solving Problems using Line Integrals</image:title>
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  </url>
  <url>
    <loc>https://www.gregschool.org/articles-page-4/2017/8/30/5g8xs8bx2yk4rez4xp70hkmry35965-k5dj3</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-09</lastmod>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59dc39b4f6576e8869f79927/1507603176920/electromagnetism+thumbnaillllll+imageeee.jpg</image:loc>
      <image:title>Articles page 4 - Calculating the amount of Electric Potential Energy Stored in a Capacitor</image:title>
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    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59dc39b4f6576e8869f79929/1504719624283/kkk.png</image:loc>
      <image:title>Articles page 4 - Calculating the amount of Electric Potential Energy Stored in a Capacitor</image:title>
      <image:caption>Figure 1</image:caption>
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  </url>
  <url>
    <loc>https://www.gregschool.org/articles-page-4/2017/9/19/the-kardeshev-scale-ge4gb</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-08</lastmod>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59dd7b6129f187ed8e5f80ff/1507687169817/space+travela+nd+colonization+thumbnail.jpg</image:loc>
      <image:title>Articles page 4 - The Kardeshev Scale</image:title>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59dd7b6129f187ed8e5f8109/1507683863314/bubble-universes-computer-illustration-of-multiple-bubble-universes-G4C3H0.jpg</image:loc>
      <image:title>Articles page 4 - The Kardeshev Scale</image:title>
      <image:caption>Artist's depiction of the multi-verse.</image:caption>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59dd7b6129f187ed8e5f8101/1507057461266/1024px-Consommations_%C3%A9nerg%C3%A9tiques_des_trois_types_de_l%27%C3%A9chelle_de_Kardashev.svg.png</image:loc>
      <image:title>Articles page 4 - The Kardeshev Scale</image:title>
      <image:caption>The Kardeshev scale ranks how advanced a technological civilization is based upon their total power consumption. A Type I civilization is capable of harnessing all of their home plant's power of \(~10^{16}W\); a Type II civilization has harnessed the power of their star ( \(~10^{26}W\)); and a Type III civilization has harnessed the power output of their entire galaxy ( \(~10^{36}W\)). There are even Type IV and Type V civilization which go beyond Kardeshev's original scale.</image:caption>
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      <image:title>Articles page 4 - The Kardeshev Scale</image:title>
      <image:caption>Dyson sphere. Credit: capnhack.com</image:caption>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/59dd7b6129f187ed8e5f8103/59dd7b6129f187ed8e5f8106/1507750720730/17202572._SX540_.jpg</image:loc>
      <image:title>Articles page 4 - The Kardeshev Scale</image:title>
      <image:caption>Artist's depiction of a ring world. Credit: http://richardfrazer.com/</image:caption>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/articles-page-4/2017/10/6/calculating-the-arc-length-of-a-curve-hk54b</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-08</lastmod>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59dd7e3d2994cac72c703af8/1507687678074/calculus+thumbnail.jpg</image:loc>
      <image:title>Articles page 4 - Calculating the Arc Length of a Curve</image:title>
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    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59dd7e3d2994cac72c703afa/1507341957781/arclengthimg1.jpg</image:loc>
      <image:title>Articles page 4 - Calculating the Arc Length of a Curve</image:title>
      <image:caption>Figure 1: The curve \(P_1P_n\) split up into an \(n\) number of chords \(P_iP_{i+1}\) where \(i=1,...,n\). By taking the sum of the lengths of each chord (represented by \(\sum_{i=1}^nL(P_iP_{i+1})\)) and then taking the limit as \(n→∞\), we obtain the exact arc length \(s\) of the entire curve.</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59dd7e3d2994cac72c703afc/1507343004584/arclengthimg2.jpg</image:loc>
      <image:title>Articles page 4 - Calculating the Arc Length of a Curve</image:title>
      <image:caption>Figure 2: A close up view of the \(i^{th}\) chord subdividing the curve \(P_1P_n\). Since the chord \(P_iP_{i+1}\) forms a right triangle, by using the Pythagorean theorem we can express \(L(P_iP_{i+1})\) as \(\sqrt{(Δx_i)^2+(Δy_i)^2}\).</image:caption>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/articles-page-4/2017/8/13/why-colonize-the-universe-z48ay</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-08</lastmod>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59dd8034bebafb7a8ad973ef/1507059034215/factoriesins.jpg</image:loc>
      <image:title>Articles page 4 - Why Colonize the Universe?</image:title>
      <image:caption>An O'Neil cylinder is a type of megastructure and artificial space habitat which was first proposed by the physicist Gerard O'Neil in 1976. An O'Neil cylinder would consist of two immense, rotating, cylindrical habitats (illustrated above) which would spin at a angular velocity that generated centrifugal forces along the interior surfaces of the cylinders which would emulate Earth-gravity. Each cylindrical habitat would be 5 miles in diameter and 20 miles long.</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59dd8034bebafb7a8ad973ed/1507058438785/51i54HqlYHL._SY344_BO1%2C204%2C203%2C200_.jpg</image:loc>
      <image:title>Articles page 4 - Why Colonize the Universe?</image:title>
      <image:caption>In Carl Sagan's book Pale Blue Dot, he argued that humans evolved a love for exploration as an essential part of our survival as a species. It was this evolutionary trait which compelled our hunter-gather ancestors to leave their home—Africa—when times were getting rough and to meander across the planet. As planetary catastrophes become increasingly likely as time rolls by, Sagan argues that this same "survival strategy" will perhaps compell humanity to colonize the solar system, and beyond.</image:caption>
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      <image:title>Articles page 4 - Why Colonize the Universe?</image:title>
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  </url>
  <url>
    <loc>https://www.gregschool.org/articles-page-4/2017/9/12/colonizing-the-kuiper-belt-and-oort-cloud-g53ff</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-08</lastmod>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59dd84eea8b2b090a391a372/1507689697151/Ancient_Mars3_02.jpg</image:loc>
      <image:title>Articles page 4 - Colonizing the Kuiper Belt and Oort Cloud</image:title>
      <image:caption>Artist's depiction of Fesenkov Crater on Mars filled with liquid water.</image:caption>
    </image:image>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59fce4d1e2c483b3c8a7dadb/1509746098354/share+technology++img.jpg</image:loc>
      <image:title>Articles page 4 - Colonizing the Kuiper Belt and Oort Cloud</image:title>
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      <image:title>Articles page 4 - Colonizing the Kuiper Belt and Oort Cloud</image:title>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/59dd84eea8b2b090a391a374/59dd84eea8b2b090a391a377/1507689697156/uranus-gas-zoom.jpg</image:loc>
      <image:title>Articles page 4 - Colonizing the Kuiper Belt and Oort Cloud</image:title>
      <image:caption>Artist’s depiction of Neptune’s (above image) and Uranus’s (below image) atmosphere being harvested for resources such as nitrogen.</image:caption>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/59dd84eea8b2b090a391a374/59dd84eea8b2b090a391a375/1507689697153/george-dennis-the-fountains-of-neptune.jpg</image:loc>
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      <image:title>Articles page 4 - Colonizing the Kuiper Belt and Oort Cloud</image:title>
      <image:caption>Another size comparison of the solar system to the Oort Cloud.</image:caption>
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      <image:title>Articles page 4 - Colonizing the Kuiper Belt and Oort Cloud</image:title>
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      <image:title>Articles page 4 - Colonizing the Kuiper Belt and Oort Cloud</image:title>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59fce41a64265f1222b3c4c7/1509746098361/email+img+thumbnail.jpg</image:loc>
      <image:title>Articles page 4 - Colonizing the Kuiper Belt and Oort Cloud</image:title>
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      <image:title>Articles page 4 - Colonizing the Kuiper Belt and Oort Cloud</image:title>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59dd84eea8b2b090a391a370/1507689697150/Kuiper_oort.jpg</image:loc>
      <image:title>Articles page 4 - Colonizing the Kuiper Belt and Oort Cloud</image:title>
      <image:caption>A size comparison of the Kuiper belt and outer solar system to the Oort Cloud.</image:caption>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/articles-page-4/2017/10/14/optimizatio-z7f59</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-08</lastmod>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59f911acf9619acf1651011e/1509295467142/Optimization+Problem.jpg</image:loc>
      <image:title>Articles page 4 - Optimization Problem</image:title>
      <image:caption>Figure 1: A graph of the circle \(x^2+y^2=4\) which is centered at the origin of the \(x\)-axis. If \((x,y)\) represents any point on the circle, if \(P\) is a point fixed at the coordinate point \((4,0)\), and if \(d\) represents the distance between those two points then, by using only calculus, we can find the point \((x,y)\) on the circle associated with the minimum distance \(d\).</image:caption>
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      <image:title>Articles page 4 - Optimization Problem</image:title>
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      <image:title>Articles page 4 - Optimization Problem</image:title>
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      <image:title>Articles page 4 - Optimization Problem</image:title>
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      <image:title>Articles page 4 - Optimization Problem</image:title>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59f911acf9619acf1651011c/1509492607607/Calculus+thumbnail.png</image:loc>
      <image:title>Articles page 4 - Optimization Problem</image:title>
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      <image:title>Articles page 4 - Optimization Problem</image:title>
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  </url>
  <url>
    <loc>https://www.gregschool.org/articles-page-4/2017/10/14/maximizing-the-area-of-a-rectangle-stk62</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-08</lastmod>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59f911bff9619acf165102a5/1509491428650/facebook+img+thumbnail.jpg</image:loc>
      <image:title>Articles page 4 - Maximizing the Area of a Rectangle</image:title>
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      <image:title>Articles page 4 - Maximizing the Area of a Rectangle</image:title>
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      <image:title>Articles page 4 - Maximizing the Area of a Rectangle</image:title>
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      <image:title>Articles page 4 - Maximizing the Area of a Rectangle</image:title>
      <image:caption>Figure 1: Given any rectangle \(xy\) where the perimeter \(2x+2y\) is the constant, we can use calculus to find that particular rectangle \(xy\) with the maximum area \(A\). The solution to this problem has practical applications. For example, suppose that someone had only 30 meters of fencing to enclose their backyard and they wanted to know what fencing layout would maximize the size and total area of their backyard.</image:caption>
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      <image:title>Articles page 4 - Maximizing the Area of a Rectangle</image:title>
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  </url>
  <url>
    <loc>https://www.gregschool.org/articles-page-4/2017/6/24/finding-the-minima-and-maxima-of-a-function-9g3gp</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-08</lastmod>
    <image:image>
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      <image:title>Articles page 4 - Finding the Minima and Maxima of a Function</image:title>
    </image:image>
    <image:image>
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      <image:title>Articles page 4 - Finding the Minima and Maxima of a Function</image:title>
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    <image:image>
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      <image:title>Articles page 4 - Finding the Minima and Maxima of a Function</image:title>
    </image:image>
    <image:image>
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      <image:title>Articles page 4 - Finding the Minima and Maxima of a Function</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59f911cac830259dbcf14c34/1509495139377/email+img+thumbnail.jpg</image:loc>
      <image:title>Articles page 4 - Finding the Minima and Maxima of a Function</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59f911cac830259dbcf14c36/1509495139379/Calculus+thumbnail.jpg</image:loc>
      <image:title>Articles page 4 - Finding the Minima and Maxima of a Function</image:title>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/newtons-laws</loc>
    <changefreq>daily</changefreq>
    <priority>0.75</priority>
    <lastmod>2018-09-14</lastmod>
  </url>
  <url>
    <loc>https://www.gregschool.org/newtons-laws/2017/8/28/newtons-law-of-gravity</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-09</lastmod>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59dbe349c027d89dcc0b93e5/1507582796854/Untitled.jpg</image:loc>
      <image:title>Newton's Laws - Newton's Law of Gravity</image:title>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/newtons-laws/2017/8/29/newtons-three-laws-of-motion</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-09</lastmod>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59dbe2a064b05fea9d3ba7ff/1507582628254/Untitled.jpg</image:loc>
      <image:title>Newton's Laws - Newton's Three Laws of Motion</image:title>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/newtons-laws/2017/8/28/motion-of-objects-experiancing-air-friction</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2018-04-09</lastmod>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59dbf14cf9a61e6c50bbbcc8/1507586382008/gfnf.jpg</image:loc>
      <image:title>Newton's Laws - Motion of objects experiancing air friction</image:title>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/newtons-laws/2017/11/2/gravitational-force-exerted-by-a-rod</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2018-04-09</lastmod>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5acb87b1562fa79982a0128d/1523288170413/google+share+thumbnail.jpg</image:loc>
      <image:title>Newton's Laws - Gravitational Force Exerted by a Rod</image:title>
    </image:image>
    <image:image>
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      <image:title>Newton's Laws - Gravitational Force Exerted by a Rod</image:title>
    </image:image>
    <image:image>
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      <image:title>Newton's Laws - Gravitational Force Exerted by a Rod</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59fbb054e2c483cd2604f07c/1523288170419/rod.png</image:loc>
      <image:title>Newton's Laws - Gravitational Force Exerted by a Rod</image:title>
      <image:caption>Figure 1: A rod of mass \(M\) and a particle of mass \(m\) are separated from each other by a distance of \(d\) along the \(x\)-axis. Each mass element \(dm\) comprising the rod is located at some position \(x\) along the \(x\)-axis and is separated from the particle \(m\) by some amount \(r\). By summing all the gravitational forces \(d\vec{F}_g\) exerted by each mass element \(dm\) comprising the rod, we can find the total gravitational force exerted on \(m\) by the entire rod.</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5acb87bf2b6a289d08df6b17/1523288170411/Twitter+thumbnail.jpg</image:loc>
      <image:title>Newton's Laws - Gravitational Force Exerted by a Rod</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5acb87ee70a6adaedb5b9ad5/1523288170407/sharee.png</image:loc>
      <image:title>Newton's Laws - Gravitational Force Exerted by a Rod</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5acb8729aa4a998f3f755542/1523288170418/classical+mechanics+thumbnail.png</image:loc>
      <image:title>Newton's Laws - Gravitational Force Exerted by a Rod</image:title>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/newtons-laws/2017/10/27/gravitational-force-exerted-by-a-sphere-geml5</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2018-04-09</lastmod>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59fa2d5a692670838629cc86/1509567663517/twiiter+img+thumbnail.jpg</image:loc>
      <image:title>Newton's Laws - Gravitational Force Exerted by a Disk</image:title>
    </image:image>
    <image:image>
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      <image:title>Newton's Laws - Gravitational Force Exerted by a Disk</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59fa2d5a692670838629cc90/1509567663526/diskss.jpg</image:loc>
      <image:title>Newton's Laws - Gravitational Force Exerted by a Disk</image:title>
      <image:caption>Figure 2: A disk of mass \(M=\int{m_{ring}}\) exerts a gravitational force on a particle of mass \(m\) a distance \(h\) away from the center of the disk along the \(x\)-axis. By summing the gravitational force exerted on \(m\) by each ring of radius \(r\) from \(r=0\) to \(r=R\), we can find the total gravitational force exerted on \(m\) by the entire disk.</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59fa2d5a692670838629cc82/1509567663512/share+img+for+classical+mechanics+thumbnail.png</image:loc>
      <image:title>Newton's Laws - Gravitational Force Exerted by a Disk</image:title>
    </image:image>
    <image:image>
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      <image:title>Newton's Laws - Gravitational Force Exerted by a Disk</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59fa2d5a692670838629cc8e/1509567663524/ring1.jpg</image:loc>
      <image:title>Newton's Laws - Gravitational Force Exerted by a Disk</image:title>
      <image:caption>Figure 1: A ring of mass \(M=\int{dm}\) exerts a gravitational force on a particle of mass \(m\) a horizontal distance \(h\) away from the center of the ring. The vertical component of force \(dF_y\) for every mass element \(dm\) in the ring is canceled out by the vertical component of force \(dF'_y\) for another mass element \(dm'\) located on the opposite side of the ring.</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59fa2d5a692670838629cc8a/1509567663521/email+img+thumbnail.jpg</image:loc>
      <image:title>Newton's Laws - Gravitational Force Exerted by a Disk</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59fa2d5a692670838629cc84/1509567663515/facebook+img+thumbnail.jpg</image:loc>
      <image:title>Newton's Laws - Gravitational Force Exerted by a Disk</image:title>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/newtons-laws/2017/10/30/gravitational-force-exerted-by-a-sphere-rdyjt-btx7m</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2018-09-14</lastmod>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5aca743e2b6a289d08b99219/1523208340227/Twitter+thumbnail.jpg</image:loc>
      <image:title>Newton's Laws - Gravitational Force Exerted by a Sphere</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5aca743e2b6a289d08b99215/1523209738312/sharee.png</image:loc>
      <image:title>Newton's Laws - Gravitational Force Exerted by a Sphere</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5aca743e2b6a289d08b99221/1523204866420/sphere+force.png</image:loc>
      <image:title>Newton's Laws - Gravitational Force Exerted by a Sphere</image:title>
      <image:caption>Figure 1: A shell can be subdivided into many very skinny rings. Anyone of these rings can be represented by the ring \(QRR_1Q_1\) illustrated above. Image credit\(^{[1]}\).</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5aca743e2b6a289d08b99217/1523208313862/facebook+thumbnail.jpg</image:loc>
      <image:title>Newton's Laws - Gravitational Force Exerted by a Sphere</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5aca743e2b6a289d08b9921d/1523208400289/google+share+thumbnail.jpg</image:loc>
      <image:title>Newton's Laws - Gravitational Force Exerted by a Sphere</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5aca743e2b6a289d08b9921b/1523208363916/email+thumbnail.jpg</image:loc>
      <image:title>Newton's Laws - Gravitational Force Exerted by a Sphere</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5aca743e2b6a289d08b9921f/1523208206453/classical+mechanics+thumbnail.png</image:loc>
      <image:title>Newton's Laws - Gravitational Force Exerted by a Sphere</image:title>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/new-blog-20</loc>
    <changefreq>daily</changefreq>
    <priority>0.75</priority>
    <lastmod>2017-10-10</lastmod>
  </url>
  <url>
    <loc>https://www.gregschool.org/new-blog-20/2017/8/30/5g8xs8bx2yk4rez4xp70hkmry35965</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-09</lastmod>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59ad98afcd39c3b55fa78ad2/1504719624283/kkk.png</image:loc>
      <image:title>Capacitors - Calculating the amount of Electric Potential Energy Stored in a Capacitor</image:title>
      <image:caption>Figure 1</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59dc32db6f4ca35190cf1592/1507604916120/electromagnetism+thumbnaillllll+imageeee.jpg</image:loc>
      <image:title>Capacitors - Calculating the amount of Electric Potential Energy Stored in a Capacitor</image:title>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/new-blog-20/2017/8/30/capacitance</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-09</lastmod>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59dc30356f4ca35190cef5c2/1507604869354/electromagnetism+thumbnaillllll+imageeee.jpg</image:loc>
      <image:title>Capacitors - Capacitance</image:title>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/new-blog-20/2017/8/30/finding-the-electric-field-produced-by-a-parallel-plate-capacitor</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-10-10</lastmod>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59ad8bd2a803bb10bef9ec85/1504719611725/ddd.png</image:loc>
      <image:title>Capacitors - Finding the Electric Field produced by a Parallel-Plate Capacitor</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59ad953b4c0dbfd7d6d763d4/1504719611734/ddfdf.png</image:loc>
      <image:title>Capacitors - Finding the Electric Field produced by a Parallel-Plate Capacitor</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59dc311bb1ffb66362919e6d/1507604895368/electromagnetism+thumbnaillllll+imageeee.jpg</image:loc>
      <image:title>Capacitors - Finding the Electric Field produced by a Parallel-Plate Capacitor</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59ad9111d55b41db66cc93d2/1504719611739/fff.png</image:loc>
      <image:title>Capacitors - Finding the Electric Field produced by a Parallel-Plate Capacitor</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59adce43e5dd5b60a9d4efef/1504719611731/sf.png</image:loc>
      <image:title>Capacitors - Finding the Electric Field produced by a Parallel-Plate Capacitor</image:title>
      <image:caption>Figure 2</image:caption>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/new-blog-20/2017/8/30/finding-the-capacitance-of-a-parallel-plate-capacitor</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-10</lastmod>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59dc30b3edaed80a4b246912/1507604675198/electromagnetism+thumbnaillllll+imageeee.jpg</image:loc>
      <image:title>Capacitors - Finding the Capacitance of a Parallel-Plate Capacitor</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59ac8b523e00bebf33d119f8/1504719599258/Fig1.jpg</image:loc>
      <image:title>Capacitors - Finding the Capacitance of a Parallel-Plate Capacitor</image:title>
      <image:caption>Figure 1: Parallel-plate capacitor. Each conductor is a flat plate with charges \(-Q\) and \(+Q\), areas of \(A\), and separated at a distance of \(d\). Courtesy of the Department of Physics and Astronomy, Michigan State University</image:caption>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/integrals</loc>
    <changefreq>daily</changefreq>
    <priority>0.75</priority>
    <lastmod>2018-09-14</lastmod>
  </url>
  <url>
    <loc>https://www.gregschool.org/integrals/2017/9/24/introduction-to-double-integrals-1</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2018-04-09</lastmod>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59d2ee4218b27d3b0d81a37e/1523152770189/riemann_boxes_m.jpg</image:loc>
      <image:title>Integrals - Introduction to Double Integrals</image:title>
      <image:caption>Figure 1: When we were deriving an expression for the definite integral in terms of the Riemann sum, we first approximated the area underneath \(f(x)\) by summing the areas of many very skinny rectangles as illustrated in (A). To define a double integral in terms of a Riemann sum, we first approximate the volume underneath a surface by summing the volumes of many very skinny columns as depicted in (C). The width and depth of each column is given by \(Δx\) and \(Δy\) and the height of each rectangle is given by the surface \(f(x,y)\) as shown in (B).</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59d68b35a803bbe90ed071c1/1523152770191/partial+der.jpg</image:loc>
      <image:title>Integrals - Introduction to Double Integrals</image:title>
      <image:caption>Figure 2: The volume underneath the surface \(f(x,y)\) can be approximated by summing the volumes of an \(nm\) number of columns underneath the surface. As these columns become infinitesimally skinny and as the number \(nm\) of them approaches infinity, this sum gives the exact volume underneath the surface \(f(x,y)\).</image:caption>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/integrals/2017/9/27/introduction-to-line-integrals</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2018-04-09</lastmod>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59d99659e9bfdf464d3e4f50/1507436224647/VIBrO.jpg</image:loc>
      <image:title>Integrals - Introduction to Line Integrals</image:title>
      <image:caption>Figure 1: The width and height of each blue rectangle is given by the arc length \(ds\) and the function \(f(x,y)\), respectively. The line integral, \(\int_Cf(x,y)ds\), represents the infinite sum of the area of each blue rectangle along the curve \(C\) (the purple line on the \(xy\)-plane). This image is a derivative work. Original image: https://www.wikihow.com/User:Atheia</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59d99cb03e00beb58c4e7323/1507436224649/fhdhfdg.jpg</image:loc>
      <image:title>Integrals - Introduction to Line Integrals</image:title>
      <image:caption>Figure 2: By the Pythagorean theorem, each infinitesimal arc length \(ds\) can be represented in terms of \(x\) and \(y\) as \(\sqrt{x+2+y^2}\).</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59daa41a64b05f268bb33242/1507501085579/sdf.jpg</image:loc>
      <image:title>Integrals - Introduction to Line Integrals</image:title>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/integrals/2017/9/30/solving-problems-using-line-integrals</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2018-04-09</lastmod>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59d53ea029f18722e25634f2/1507506885589/Untitled.jpg</image:loc>
      <image:title>Integrals - Solving Problems using Line Integrals</image:title>
      <image:caption>Figure 2: A proton \(P_2\) seperated by an initil seperation distance \(r_0\) from a station proton \(P_1\) moves along an arbitrary path until it reaches a seperation distance of \(r\). According to Column's law, the proton \(P_1\) will exert an electric force and, hence, also do work on the proton \(P_2\) as it moves from \(r_0\) to \(r\). The electric force forms a vector field and by calculuating the line integral along \(P_2\)'s path, we can calculate the amount of work done on \(P_2\).</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59d188183e00be69b7c3517a/1507506885588/156px-Circular_cylinder_rh.jpg</image:loc>
      <image:title>Integrals - Solving Problems using Line Integrals</image:title>
      <image:caption>Figure 1: A cylinder with height \(h=2\) and radius \(r=1\). The "top" and "bottom" pieces of the cylinder are removed.</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59daa883a803bb45f41dc507/1507506885586/sdfsdfdsdfdfdf+october+8.jpg</image:loc>
      <image:title>Integrals - Solving Problems using Line Integrals</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59d19207017db22813f4a100/1507506885591/main-qimg-ef54da6034b7e89fb771a40923f089ca.gif</image:loc>
      <image:title>Integrals - Solving Problems using Line Integrals</image:title>
      <image:caption>Figure 3: A mass \(m\) is attached to the end of a rope of length \(L\). The mass falls and travels a distance \(s\) with a total angular displacement of \(θ\).</image:caption>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/integrals/2017/10/27/gravitational-force-exerted-by-a-sphere</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2018-04-09</lastmod>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59fa23fe0846657c0d448696/1509567663517/twiiter+img+thumbnail.jpg</image:loc>
      <image:title>Integrals - Gravitational Force Exerted by a Disk</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59fa2ed053450ad9f171a760/1509568216076/Calculus+thumbnail.png</image:loc>
      <image:title>Integrals - Gravitational Force Exerted by a Disk</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59fa23de9140b71df4373eb4/1509567663519/google+img+thumbnail.jpg</image:loc>
      <image:title>Integrals - Gravitational Force Exerted by a Disk</image:title>
    </image:image>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59fa23c0d6839ae2db9f574f/1509567663521/email+img+thumbnail.jpg</image:loc>
      <image:title>Integrals - Gravitational Force Exerted by a Disk</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59f4bc8f71c10b247dd586fb/1509567663524/ring1.jpg</image:loc>
      <image:title>Integrals - Gravitational Force Exerted by a Disk</image:title>
      <image:caption>Figure 1: A ring of mass \(M=\int{dm}\) exerts a gravitational force on a particle of mass \(m\) a horizontal distance \(h\) away from the center of the ring. The vertical component of force \(dF_y\) for every mass element \(dm\) in the ring is canceled out by the vertical component of force \(dF'_y\) for another mass element \(dm'\) located on the opposite side of the ring.</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59f4c83071c10b247dd675cb/1509567663526/diskss.jpg</image:loc>
      <image:title>Integrals - Gravitational Force Exerted by a Disk</image:title>
      <image:caption>Figure 2: A disk of mass \(M=\int{m_{ring}}\) exerts a gravitational force on a particle of mass \(m\) a distance \(h\) away from the center of the disk along the \(x\)-axis. By summing the gravitational force exerted on \(m\) by each ring of radius \(r\) from \(r=0\) to \(r=R\), we can find the total gravitational force exerted on \(m\) by the entire disk.</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59fa23cc08522944c7d66daf/1509567663515/facebook+img+thumbnail.jpg</image:loc>
      <image:title>Integrals - Gravitational Force Exerted by a Disk</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59fa2656692670838628b567/1509567663512/share+img+for+classical+mechanics+thumbnail.png</image:loc>
      <image:title>Integrals - Gravitational Force Exerted by a Disk</image:title>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/integrals/2017/8/29/finding-the-integral-of-kxm</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-09</lastmod>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59d96b287131a562e4837142/1507421210861/areaoftriangle.jpg</image:loc>
      <image:title>Integrals - Finding the integral of \(kx^m\)</image:title>
      <image:caption>Figure 1: The area underneath the function \(f(x)=2x\) is simply just the area of a triangle. The base of the triangle is \(x\) and its height is \(f(x)=2x\). Using the formula for the area of a triangle, we find that the area underneath \(f(x)=2x\) is \(x^2\).</image:caption>
    </image:image>
    <image:image>
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      <image:title>Integrals - Finding the integral of \(kx^m\)</image:title>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/integrals/2017/8/29/introduction-to-integrals</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-09</lastmod>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59addf52d7bdcecfe13491cf/1504735588352/Riemann_Integration_and_Darboux_Upper_Sums.gif</image:loc>
      <image:title>Integrals - Introduction to Integrals</image:title>
      <image:caption>Figure 2. The approximate area, \(\sum_{i=1}^nf(x_n)Δx\), underneath the curve \(y=x^2\) becomes closer and closer to the exact area underneath the curve as the number \(n\) of terms increases.</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59dbd989914e6b12a38ed4a4/1507580301436/Untitled.jpg</image:loc>
      <image:title>Integrals - Introduction to Integrals</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59adde90e5dd5b60a9d5d03b/1504735588348/dfgd.png</image:loc>
      <image:title>Integrals - Introduction to Integrals</image:title>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/integrals/2017/10/30/gravitational-force-exerted-by-a-sphere-jx7yd</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2018-09-14</lastmod>
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      <image:title>Integrals - Gravitational Force Exerted by a Sphere</image:title>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5acb8e01352f53a44f12f831/1523209296664/google+share+thumbnail.jpg</image:loc>
      <image:title>Integrals - Gravitational Force Exerted by a Sphere</image:title>
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    <image:image>
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      <image:title>Integrals - Gravitational Force Exerted by a Sphere</image:title>
    </image:image>
    <image:image>
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      <image:title>Integrals - Gravitational Force Exerted by a Sphere</image:title>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5acb8e01352f53a44f12f82d/1523209296659/Twitter+thumbnail.jpg</image:loc>
      <image:title>Integrals - Gravitational Force Exerted by a Sphere</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5acb8e01352f53a44f12f833/1523209296666/classical+mechanics+thumbnail.png</image:loc>
      <image:title>Integrals - Gravitational Force Exerted by a Sphere</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5acb8e01352f53a44f12f835/1523209296668/sphere+force.png</image:loc>
      <image:title>Integrals - Gravitational Force Exerted by a Sphere</image:title>
      <image:caption>Figure 1: A shell can be subdivided into many very skinny rings. Anyone of these rings can be represented by the ring \(QRR_1Q_1\) illustrated above. Image credit\(^{[1]}\).</image:caption>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/integrals/2017/10/6/calculating-the-arc-length-of-a-curve-hk54b-xg8k6</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-08</lastmod>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59f54ea50852291b228d44b6/1507687678074/calculus+thumbnail.jpg</image:loc>
      <image:title>Integrals - Calculating the Arc Length of a Curve</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59f54ea50852291b228d44b8/1507341957781/arclengthimg1.jpg</image:loc>
      <image:title>Integrals - Calculating the Arc Length of a Curve</image:title>
      <image:caption>Figure 1: The curve \(P_1P_n\) split up into an \(n\) number of chords \(P_iP_{i+1}\) where \(i=1,...,n\). By taking the sum of the lengths of each chord (represented by \(\sum_{i=1}^nL(P_iP_{i+1})\)) and then taking the limit as \(n→∞\), we obtain the exact arc length \(s\) of the entire curve.</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59f54ea50852291b228d44ba/1507343004584/arclengthimg2.jpg</image:loc>
      <image:title>Integrals - Calculating the Arc Length of a Curve</image:title>
      <image:caption>Figure 2: A close up view of the \(i^{th}\) chord subdividing the curve \(P_1P_n\). Since the chord \(P_iP_{i+1}\) forms a right triangle, by using the Pythagorean theorem we can express \(L(P_iP_{i+1})\) as \(\sqrt{(Δx_i)^2+(Δy_i)^2}\).</image:caption>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/integrals/2017/11/2/gravitational-force-exerted-by-a-rod-zf4pf-np6lw-pz3ga</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2018-04-09</lastmod>
    <image:image>
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      <image:title>Integrals - Gravitational Force Exerted by a Rod</image:title>
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    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5acb8e1a88251b534876c3a2/1523288004050/Twitter+thumbnail.jpg</image:loc>
      <image:title>Integrals - Gravitational Force Exerted by a Rod</image:title>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5acb8e1a88251b534876c3a8/1523287857170/classical+mechanics+thumbnail.png</image:loc>
      <image:title>Integrals - Gravitational Force Exerted by a Rod</image:title>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5acb8e1a88251b534876c3a6/1523287964387/email+thumbnail.jpg</image:loc>
      <image:title>Integrals - Gravitational Force Exerted by a Rod</image:title>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5acb8e1a88251b534876c3a0/1523287944108/facebook+thumbnail.jpg</image:loc>
      <image:title>Integrals - Gravitational Force Exerted by a Rod</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5acb8e1a88251b534876c3aa/1509666905146/rod.png</image:loc>
      <image:title>Integrals - Gravitational Force Exerted by a Rod</image:title>
      <image:caption>Figure 1: A rod of mass \(M\) and a particle of mass \(m\) are separated from each other by a distance of \(d\) along the \(x\)-axis. Each mass element \(dm\) comprising the rod is located at some position \(x\) along the \(x\)-axis and is separated from the particle \(m\) by some amount \(r\). By summing all the gravitational forces \(d\vec{F}_g\) exerted by each mass element \(dm\) comprising the rod, we can find the total gravitational force exerted on \(m\) by the entire rod.</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5acb8e1a88251b534876c3a4/1523287988805/google+share+thumbnail.jpg</image:loc>
      <image:title>Integrals - Gravitational Force Exerted by a Rod</image:title>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/integrals/2017/9/30/proof-of-greens-theorem-4kbde-fms6d</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2018-06-28</lastmod>
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      <image:title>Integrals - Proof of Green's Theorem</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5b3475f68a922d73de4c00af/1530156441620/google+img+thumbnail.jpg</image:loc>
      <image:title>Integrals - Proof of Green's Theorem</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5b3475f68a922d73de4c00b3/1530156011880/Calculus+thumbnail.png</image:loc>
      <image:title>Integrals - Proof of Green's Theorem</image:title>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5b3475f68a922d73de4c00ad/1530162636743/twiiter+img+thumbnail.jpg</image:loc>
      <image:title>Integrals - Proof of Green's Theorem</image:title>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5b3475f68a922d73de4c00b7/1530147999505/images.png</image:loc>
      <image:title>Integrals - Proof of Green's Theorem</image:title>
      <image:caption>Figure 2: We can split the curve \(c\) into two separate curves, \(c_1\) and \(c_2\). This also allows us to split the function \(y(x)\) into the two separate functions, \(y(x_1)\) and \(y(x_2)\).</image:caption>
    </image:image>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5b3475f68a922d73de4c00a9/1530156044345/share+calculus+img.png</image:loc>
      <image:title>Integrals - Proof of Green's Theorem</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5b3475f68a922d73de4c00b9/1530155160565/images.png</image:loc>
      <image:title>Integrals - Proof of Green's Theorem</image:title>
      <image:caption>Figure 3: We can break up the curve \(c\) into the two separate curves, \(c_1\) and \(c_2\). This also allows us to break up the function \(x(y)\) into the two separate functions, \(x(y_1)\) and \(x(y_2)\).</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5b3475f68a922d73de4c00b5/1506810526998/429px-Green%27s-theorem-simple-region.svg.png</image:loc>
      <image:title>Integrals - Proof of Green's Theorem</image:title>
      <image:caption>Figure 1: The curve \(C=C_1+C_2+C_3+C_4\) is piece-wise smooth. It is "piece-wise" because it is split up into an \(n=4\) number of separate curves with an \(n=4\) number of "edges." It is "smooth" because each individual curve itself is smooth without any sharp edges or cusps. This curve is also positively-oriented because its direction goes counter-clockwise. Image by Cronholm 144.</image:caption>
    </image:image>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5b3475f68a922d73de4c00b1/1530157315746/email+img+thumbnail.jpg</image:loc>
      <image:title>Integrals - Proof of Green's Theorem</image:title>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/articles-page-5</loc>
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    <priority>0.75</priority>
    <lastmod>2019-03-23</lastmod>
  </url>
  <url>
    <loc>https://www.gregschool.org/articles-page-5/2017/8/13/nuclear-fusion-engines-g9fdd</loc>
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    <priority>0.5</priority>
    <lastmod>2017-11-09</lastmod>
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      <image:title>Articles page 5 - Nuclear Fusion Engines</image:title>
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  <url>
    <loc>https://www.gregschool.org/articles-page-5/2017/6/28/terraforming-mars-gz3x8</loc>
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    <lastmod>2017-11-09</lastmod>
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      <image:title>Articles page 5 - Terraforming and Colonizing Mars</image:title>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59af755cf14aa16cb28c3ab3/1502315090185/ares2.jpg</image:loc>
      <image:title>Articles page 5 - Terraforming and Colonizing Mars</image:title>
      <image:caption>Artist's depiction of the Ares spaceship from Kim Stanley Robinson's novel, Red Mars.</image:caption>
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    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59af755cf14aa16cb28c3ab9/1502431153897/</image:loc>
      <image:title>Articles page 5 - Terraforming and Colonizing Mars</image:title>
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      <image:title>Articles page 5 - Terraforming and Colonizing Mars</image:title>
      <image:caption>"This shot follows the cabin of a space elevator descending on a cable towards the northern parts of the Terra Cimmeria highlands on Mars. A large settlement, hinted as glowing lights in the dark, can be seen far below on the ground. One of Mars' two moons - Phobos - is seen above the cabin to the left of the cable in the beginning of the shot." This image was produced by Erik Wernquist.</image:caption>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59af755cf14aa16cb28c3abb/1502314679613/olympus.jpg</image:loc>
      <image:title>Articles page 5 - Terraforming and Colonizing Mars</image:title>
      <image:caption>Poster by SpaceX</image:caption>
    </image:image>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59dd23c08419c2764d7dbf1c/1510177067128/space+travela+nd+colonization+thumbnail.jpg</image:loc>
      <image:title>Articles page 5 - Terraforming and Colonizing Mars</image:title>
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      <image:title>Articles page 5 - Terraforming and Colonizing Mars</image:title>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/articles-page-5/2017/5/15/particle-in-one-dimensional-box-dwfnl</loc>
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    <lastmod>2017-11-09</lastmod>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59af76a2d55b416b4ae15650/1495487701759/</image:loc>
      <image:title>Articles page 5 - Time-Independant Schrodinger Equation: Free Particle and Particle in One-Dimensional Box</image:title>
      <image:caption>Figure 4: Illustration shows the allowed energy levels of a particle trapped inside of a one-dimensional box.</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59af76a2d55b416b4ae1564a/1495487069613/kjkjnj.png</image:loc>
      <image:title>Articles page 5 - Time-Independant Schrodinger Equation: Free Particle and Particle in One-Dimensional Box</image:title>
      <image:caption>Figure 1 (click to expand): Illustration of a free particle moving in a "one-dimensional box" which is trapped inside of an infinite potential well.</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59af76a2d55b416b4ae1564c/1495562943423/sch.png</image:loc>
      <image:title>Articles page 5 - Time-Independant Schrodinger Equation: Free Particle and Particle in One-Dimensional Box</image:title>
      <image:caption>Figure 2 (click to expand): The probability amplitude of measuring the particle at a position \(x\) in the presence of a potential \(V_0\) decreases exponentially with increasing \(V_0\).</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59af76a2d55b416b4ae15648/1495485871466/</image:loc>
      <image:title>Articles page 5 - Time-Independant Schrodinger Equation: Free Particle and Particle in One-Dimensional Box</image:title>
      <image:caption>"A wave function that satisfies the nonrelativistic Schrödinger equation with V = 0. In other words, this corresponds to a particle traveling freely through empty space. The real part of the wave function is plotted here."\(^{[1]}\)</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59af76a2d55b416b4ae1564e/1494831797145/</image:loc>
      <image:title>Articles page 5 - Time-Independant Schrodinger Equation: Free Particle and Particle in One-Dimensional Box</image:title>
      <image:caption>Figure 3 (click to expand): Illustration of a free particle moving in a one-dimensional box which is "pinned down" by a finite well. The probability amplitude of finding the particle outside of the box decreases exponentially as a function of distance.</image:caption>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/articles-page-5/2017/5/14/friedman-robertson-walker-frw-equation-s6f2m</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-11</lastmod>
  </url>
  <url>
    <loc>https://www.gregschool.org/articles-page-5/2017/5/14/solving-the-frw-equation-for-the-scaling-factor-in-different-scenarios-hdsrg</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-09</lastmod>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59ffd039ec212d4734becb0c/1509980764068/AT_7e_Figure_27_01%5B2%5D.jpg</image:loc>
      <image:title>Articles page 5 - Solving the FRW Equation for the Scaling Factor in different scenarios</image:title>
      <image:caption>Figure 1: As you can see from the graph above, for the first roughly 10,000 years most of the energy density in the universe was due to the presence of radiation. During the time interval from when the universe was 10,000 years old to when it was several billion years old, the energy density of the universe was dominated by matter. In our present epoch, the energy density of the universe is dominated by dark energy (or vacuum energy). This graph has profound implications. As time progresses, dark energy will become more and more dominant and will remain the dominant source of energy in the universe; since dark energy causes everything in the universe to expand, the universe will continue to expand without ever stopping. This graph, essentially, implies the ultimate fate of the universe. The universe will continue to expand more and more until it becomes dark, empty, and lifeless.</image:caption>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/articles-page-5/2017/5/14/bentleys-and-olbers-paradoxes-e6hj4</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-10</lastmod>
  </url>
  <url>
    <loc>https://www.gregschool.org/articles-page-5/2017/5/14/8c5knwf9nztiio7uwnvvotz1pj86ht-thkb7</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-09</lastmod>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59af7e2fd55b416b4ae1a923/1502416195791/</image:loc>
      <image:title>Articles page 5 - Time Dilation</image:title>
      <image:caption>Figure 1</image:caption>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/articles-page-5/2017/8/29/introduction-to-integrals-xl5rn</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-09</lastmod>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59b071649f7456145d0c076e/1504567134996/Riemann_Integration_and_Darboux_Upper_Sums.gif</image:loc>
      <image:title>Articles page 5 - Introduction to Integrals</image:title>
      <image:caption>Figure 2. The approximate area, \(\sum_{i=1}^nf(x_n)Δx\), underneath the curve \(y=x^2\) becomes closer and closer to the exact area underneath the curve as the number \(n\) of terms increases.</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59dbd9d3c534a5f2363c4d29/1510176997141/Untitled.jpg</image:loc>
      <image:title>Articles page 5 - Introduction to Integrals</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59b071649f7456145d0c076c/1504566939599/dfgd.png</image:loc>
      <image:title>Articles page 5 - Introduction to Integrals</image:title>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/articles-page-5/2017/8/16/maclaurin-polynomial-and-series-9cll7</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-08</lastmod>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59dbdfbbedaed80a4b204a38/1510176987588/Untitled.jpg</image:loc>
      <image:title>Articles page 5 - Maclaurin/Taylor Polynomials and Series</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59b44013d55b4168dbddb011/1504563483921/Exp_series.gif</image:loc>
      <image:title>Articles page 5 - Maclaurin/Taylor Polynomials and Series</image:title>
      <image:caption>Figure 1. Maclaurin polynomials of different order \(n\) (red curves) approximating the function \(e^x\) (blue curve).</image:caption>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/articles-page-5/2017/10/6/calculating-the-volume-of-a-sphere-e6jde-bs7ml</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-09</lastmod>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59d95d69cd0f688947d834b5/1507412420221/moment-of-inertia-of-sphere.jpg</image:loc>
      <image:title>Articles page 5 - Calculating the Volume of a Sphere</image:title>
      <image:caption>Figure 4: By taking the infinite sum of the volumes, \(π(f(x))^2dx\), of every cylinder from \(x=0\) to \(x=R\), we can obtain the volume of half of the sphere depicted above. By multiplying our answer by two, we can obtain the volume of the whole sphere. Image credit: https://www.miniphysics.com/uy1-calculation-of-moment-of-inertia-of-solid-sphere.html</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59daa4b28a02c7abc31c7c36/1510175551473/sdf.jpg</image:loc>
      <image:title>Articles page 5 - Calculating the Volume of a Sphere</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59d95d69cd0f688947d834b3/1507412420216/s9NuK.jpg</image:loc>
      <image:title>Articles page 5 - Calculating the Volume of a Sphere</image:title>
      <image:caption>Figure 3: By rotating the \(i^{th}\) rectangle about the \(x\)-axis, the cylinder depicted above is obtained. By doing this for each rectangle, an \(n\) number of cylinders are obtained. All of these cylinders fit inside of a hemisphere of radius \(r\) and the sum of the volumes of all of those cylinders approximate the volume of the hemisphere.</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59d95d69cd0f688947d834b1/1507412420213/volumeofsphereimg1.jpg</image:loc>
      <image:title>Articles page 5 - Calculating the Volume of a Sphere</image:title>
      <image:caption>Figure 2: A graph of the quarter circle \(x^2+y^2=r^2\) for \(x≥0\) and \(y≥0\). An \(n\) number of rectangles, \(f(x_i\)Δx\), are drawn underneath the curve.</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59d95d69cd0f688947d834af/1507412420207/320px-Rotationskoerper_animation.gif</image:loc>
      <image:title>Articles page 5 - Calculating the Volume of a Sphere</image:title>
      <image:caption>Figure 1: The "vase" shaped surface is obtained by revolving a curve about the vertical axis. The region of space that the surface encloses is called a solid of revolution.</image:caption>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/articles-page-6</loc>
    <changefreq>daily</changefreq>
    <priority>0.75</priority>
    <lastmod>2019-03-21</lastmod>
  </url>
  <url>
    <loc>https://www.gregschool.org/articles-page-6/2017/5/14/dark-energy-exgdc</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-11</lastmod>
  </url>
  <url>
    <loc>https://www.gregschool.org/articles-page-6/2017/5/14/cosmic-microwave-background-radiation-lfmal</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-11</lastmod>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59af7c52c027d8e9bfa7d30a/1494827005244/</image:loc>
      <image:title>Articles page 6 - Cosmic Microwave Background Radiation</image:title>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/articles-page-6/2017/5/14/dark-matter-yla9j</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-11</lastmod>
  </url>
  <url>
    <loc>https://www.gregschool.org/articles-page-6/2017/8/30/finding-the-capacitance-of-a-parallel-plate-capacitor-ajby4</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-10</lastmod>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59dc3c75b1ffb66362922088/1510177451011/electromagnetism+thumbnaillllll+imageeee.jpg</image:loc>
      <image:title>Articles page 6 - Finding the Capacitance of a Parallel-Plate Capacitor</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59b032efc534a58c97cb0d19/1504480094587/Fig1.jpg</image:loc>
      <image:title>Articles page 6 - Finding the Capacitance of a Parallel-Plate Capacitor</image:title>
      <image:caption>Figure 1: Parallel-plate capacitor. Each conductor is a flat plate with charges \(-Q\) and \(+Q\), areas of \(A\), and separated at a distance of \(d\). Courtesy of the Department of Physics and Astronomy, Michigan State University</image:caption>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/articles-page-6/2017/5/14/columns-law-7fdl2</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-09</lastmod>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59dc43e5f43b55f79a348b9d/1510177552288/electromagnetism+thumbnaillllll+imageeee.jpg</image:loc>
      <image:title>Articles page 6 - Column's Law</image:title>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/articles-page-6/2017/6/20/derivation-of-guasss-law-from-columns-law-mbxrn</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-09</lastmod>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59b03342d2b857ba2834b3fc/1501802501336/guass.jpg</image:loc>
      <image:title>Articles page 6 - Derivation of Guass's Law from Column's Law</image:title>
      <image:caption>Figure 1 (click to enlarge)</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59dc41cc1f318db010fdb87c/1510177532479/electromagnetism+thumbnaillllll+imageeee.jpg</image:loc>
      <image:title>Articles page 6 - Derivation of Guass's Law from Column's Law</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59b03342d2b857ba2834b3fe/1501804297766/</image:loc>
      <image:title>Articles page 6 - Derivation of Guass's Law from Column's Law</image:title>
      <image:caption>Figure 2 (click to enlarge)</image:caption>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/articles-page-6/2017/5/18/v7t2klwmycopiblvbhzkhyw2duujqy-bjxsk</loc>
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    <priority>0.5</priority>
    <lastmod>2017-11-09</lastmod>
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      <image:title>Articles page 6 - Introduction to Lagrangian Mechanics</image:title>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/articles-page-6/2017/5/18/finding-the-geodesic-on-a-cylinder-mley2</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2019-02-22</lastmod>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59dbfa73cd39c33ffeae251e/1510177524654/gfnf.jpg</image:loc>
      <image:title>Articles page 6 - Finding the geodesic on a cylinder</image:title>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/articles-page-6/2017/5/18/brachistochrone-problem-8bgmb</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-09</lastmod>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59dbfa5ef5e2317170efd405/1510177508786/gfnf.jpg</image:loc>
      <image:title>Articles page 6 - Brachistochrone problem</image:title>
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    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59b033c19f745650b3ec7ec7/1495304408606/</image:loc>
      <image:title>Articles page 6 - Brachistochrone problem</image:title>
      <image:caption>Credit\(^{[3]}\)</image:caption>
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    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59b033c19f745650b3ec7ec3/1495304339104/</image:loc>
      <image:title>Articles page 6 - Brachistochrone problem</image:title>
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    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59b033c19f745650b3ec7ec5/1495304353556/</image:loc>
      <image:title>Articles page 6 - Brachistochrone problem</image:title>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/articles-page-6/2017/5/18/generalized-coordinates-7r5bn</loc>
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    <priority>0.5</priority>
    <lastmod>2017-11-09</lastmod>
    <image:image>
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      <image:title>Articles page 6 - Generalized coordinates</image:title>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/articles-page-7</loc>
    <changefreq>daily</changefreq>
    <priority>0.75</priority>
    <lastmod>2019-03-21</lastmod>
  </url>
  <url>
    <loc>https://www.gregschool.org/articles-page-7/2017/5/14/electric-flux-enbx3</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-09</lastmod>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59dc3f77b07869b58368dafd/1510177608894/electromagnetism+thumbnaillllll+imageeee.jpg</image:loc>
      <image:title>Articles page 7 - Electric Flux</image:title>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/articles-page-7/2017/7/20/using-guasss-law-to-find-the-electric-field-produced-by-a-single-point-charge-8m3gx</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-09</lastmod>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59b033507131a5ba424f1743/1501805131555/</image:loc>
      <image:title>Articles page 7 - Using Guass's Law to find the Electric Field Produced by a Single Point Charge</image:title>
      <image:caption>Figure 2</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59b033507131a5ba424f1745/1501807096166/</image:loc>
      <image:title>Articles page 7 - Using Guass's Law to find the Electric Field Produced by a Single Point Charge</image:title>
      <image:caption>Figure 3</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59dc41fe29f1876a45849d25/1510177599547/electromagnetism+thumbnaillllll+imageeee.jpg</image:loc>
      <image:title>Articles page 7 - Using Guass's Law to find the Electric Field Produced by a Single Point Charge</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59b033507131a5ba424f1741/1501804682969/guass.jpg</image:loc>
      <image:title>Articles page 7 - Using Guass's Law to find the Electric Field Produced by a Single Point Charge</image:title>
      <image:caption>Figure 1</image:caption>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/articles-page-7/2017/5/18/derivation-of-the-euler-lagrange-equation-s8wam</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-09</lastmod>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59dbfaa93e00bed1b4262679/1510177576339/gfnf.jpg</image:loc>
      <image:title>Articles page 7 - Derivation of the Euler-Lagrange Equation</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59b033813e00be820cf34912/1495304730085/</image:loc>
      <image:title>Articles page 7 - Derivation of the Euler-Lagrange Equation</image:title>
      <image:caption>Figure 1 (click to expand)</image:caption>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/articles-page-7/2017/5/18/noethers-theorem-78d8y</loc>
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    <priority>0.5</priority>
    <lastmod>2017-11-09</lastmod>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59dbfaf7c027d89dcc0d3a58/1510177619502/gfnf.jpg</image:loc>
      <image:title>Articles page 7 - Noether’s Theorem</image:title>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/articles-page-7/2017/8/29/newtons-three-laws-of-motion-62d9d</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-09</lastmod>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59dbe2d7e9bfdf322eccd41d/1510177711160/Untitled.jpg</image:loc>
      <image:title>Articles page 7 - Newton's Three Laws of Motion</image:title>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/articles-page-7/2017/8/28/newtons-law-of-gravity-ybhff</loc>
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    <priority>0.5</priority>
    <lastmod>2017-11-09</lastmod>
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      <image:title>Articles page 7 - Newton's Law of Gravity</image:title>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/articles-page-7/2017/6/20/76hgztk8ogz149g9acwmizq62okwe4-cz2yr</loc>
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    <lastmod>2017-11-09</lastmod>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59dbe203197aeaa9a58bbb65/1510177702121/Untitled.jpg</image:loc>
      <image:title>Articles page 7 - Position Vectors, Displacement, Velocity, and Acceleration</image:title>
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      <image:title>Articles page 7 - Position Vectors, Displacement, Velocity, and Acceleration</image:title>
      <image:caption>Figure 1 (click to enlarge)</image:caption>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59b03535cd0f68dbd2291c19/1501788322829/</image:loc>
      <image:title>Articles page 7 - Position Vectors, Displacement, Velocity, and Acceleration</image:title>
      <image:caption>Figure 2</image:caption>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/articles-page-7/2017/6/20/faxkbn1icm37pyljps0j38mgdt0t22-ch2g2</loc>
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    <lastmod>2017-11-09</lastmod>
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      <image:title>Articles page 7 - Basic Equations of Kinematics</image:title>
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  </url>
  <url>
    <loc>https://www.gregschool.org/articles-page-7/2017/5/14/introduction-to-newtonian-mechanics-25a5e</loc>
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    <lastmod>2017-11-09</lastmod>
  </url>
  <url>
    <loc>https://www.gregschool.org/articles-page-7/2017/5/18/what-do-we-mean-by-kinematics-dynamics-and-mechanics-xr2cr</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-09</lastmod>
  </url>
  <url>
    <loc>https://www.gregschool.org/articles-page-8</loc>
    <changefreq>daily</changefreq>
    <priority>0.75</priority>
    <lastmod>2019-03-21</lastmod>
  </url>
  <url>
    <loc>https://www.gregschool.org/articles-page-8/2017/5/14/xe30zrw2tke0y051q8xdpf9cxaff19-fyzrj</loc>
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    <priority>0.5</priority>
    <lastmod>2017-11-11</lastmod>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59af7a9cf7e0ab91b22cc150/1494828080386/</image:loc>
      <image:title>Articles page 8 - Scaling Factor, Hubble's Parameter, and the Age of the Universe</image:title>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/articles-page-8/2017/5/14/4ufuuy7fweohxl2tk6hryzmsq50amd-a67kn</loc>
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    <lastmod>2017-11-09</lastmod>
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      <image:title>Articles page 8 - Introduction to Mechanical Waves</image:title>
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  </url>
  <url>
    <loc>https://www.gregschool.org/articles-page-8/2017/5/14/rotational-kinematics-5xef2</loc>
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    <priority>0.5</priority>
    <lastmod>2017-11-09</lastmod>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59dbf864b07869b583657f74/1510177833044/gfnf.jpg</image:loc>
      <image:title>Articles page 8 - Rotational Kinematics</image:title>
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  </url>
  <url>
    <loc>https://www.gregschool.org/articles-page-8/2017/5/14/introduction-to-rotational-kinetic-energy-b8hy8</loc>
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    <priority>0.5</priority>
    <lastmod>2017-11-09</lastmod>
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      <image:title>Articles page 8 - Introduction to Rotational Kinetic Energy</image:title>
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  </url>
  <url>
    <loc>https://www.gregschool.org/articles-page-8/2017/5/14/torque-6zmaw</loc>
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    <priority>0.5</priority>
    <lastmod>2017-11-11</lastmod>
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      <image:title>Articles page 8 - Torque</image:title>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/articles-page-8/2017/8/10/introduction-to-linear-momentum-mbs6h</loc>
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    <priority>0.5</priority>
    <lastmod>2017-11-09</lastmod>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59dbf285d7bdcefd90867d48/1510177736905/gfnf.jpg</image:loc>
      <image:title>Articles page 8 - Introduction to Linear Momentum</image:title>
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  </url>
  <url>
    <loc>https://www.gregschool.org/articles-page-8/2017/8/10/derivation-on-momentum-conservation-bxjp5</loc>
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    <priority>0.5</priority>
    <lastmod>2017-11-09</lastmod>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59dbf33d46c3c48d6775f6cb/1510177725819/gfnf.jpg</image:loc>
      <image:title>Articles page 8 - Derivation of Momentum Conservation</image:title>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/articles-page-8/2017/8/10/inelastic-collisions-mjsnh</loc>
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    <priority>0.5</priority>
    <lastmod>2017-11-10</lastmod>
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      <image:title>Articles page 8 - Inelastic Collisions</image:title>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/articles-page-8/2017/8/28/motion-of-objects-experiancing-air-friction-wheys</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-09</lastmod>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59dbf1911f318db010f9f294/1510177749331/gfnf.jpg</image:loc>
      <image:title>Articles page 8 - Motion of objects experiancing air friction</image:title>
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  </url>
  <url>
    <loc>https://www.gregschool.org/articles-page-8/2017/6/21/the-abstract-has-a-lot-to-say-about-the-physical-world-xk4tb</loc>
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    <priority>0.5</priority>
    <lastmod>2017-11-09</lastmod>
  </url>
  <url>
    <loc>https://www.gregschool.org/solidsofrevolution</loc>
    <changefreq>daily</changefreq>
    <priority>0.75</priority>
    <lastmod>2017-11-04</lastmod>
  </url>
  <url>
    <loc>https://www.gregschool.org/solidsofrevolution/2017/10/22/volume-of-an-oblate-spheroid</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-09</lastmod>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59fd163ee2c483f6d02defca/1509760277356/email+thumbnail.jpg</image:loc>
      <image:title>Solids of Revolution - Volume of an Oblate Spheroid</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59fd16029140b72e25d930d6/1509760277357/Calculus+thumbnail.png</image:loc>
      <image:title>Solids of Revolution - Volume of an Oblate Spheroid</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59fd161464265f6a40ff563c/1509760277350/facebook+thumbnail.jpg</image:loc>
      <image:title>Solids of Revolution - Volume of an Oblate Spheroid</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59fd166c4192021a540ae4e6/1509760277354/google+share+thumbnail.jpg</image:loc>
      <image:title>Solids of Revolution - Volume of an Oblate Spheroid</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59fd18c7e31d1945635a85d8/1509760277348/temporary+shareeeeee.png</image:loc>
      <image:title>Solids of Revolution - Volume of an Oblate Spheroid</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59fd0a0053450a448c5d5d7a/1509760277361/oblate+spheroid+img2.png</image:loc>
      <image:title>Solids of Revolution - Volume of an Oblate Spheroid</image:title>
      <image:caption>Figure 2: A cylindrical shell is obtained by revolving the rectangle \(f(x_i)Δx\) about the \(y\)-axis. Doing this for all \(n\) rectangles, we get an \(n\) number of shells. By summing the volumes of these \(n\) number of cylindrical shells, we can obtain an estimate for total volume enclosed inside of the paraboloid obtained by rotating the quarter-ellipse (the one in the upper-right quadrant) about the \(x\)-axis.</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59f63ca00846653ab7a4fa4c/1509760277363/oblate+sphereoid.jpg</image:loc>
      <image:title>Solids of Revolution - Volume of an Oblate Spheroid</image:title>
      <image:caption>Figure 3: If \(a\) and \(c\) represents the semi-major and semi-minor axes of an ellipse, respectively, and if \(a=3\) and \(c=2\) then by rotating such an ellipse about an axis we can obtain an oblate spheroid.</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59fd1697e4966b0f2558c951/1509760277352/Twitter+thumbnail.jpg</image:loc>
      <image:title>Solids of Revolution - Volume of an Oblate Spheroid</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59fcff39e2c483f6d02baa0a/1509760277359/oblate+spheroid+img1.png</image:loc>
      <image:title>Solids of Revolution - Volume of an Oblate Spheroid</image:title>
      <image:caption>Figure 1: Graph of the ellipse \(\frac{x^2}{9}+\frac{y^2}{4}=1\) centered at the origin of the \(xy\)-plane. Also, I have drawn the \(i^{th}\) rectangle underneath the quarter-ellipse within the first quadrant. There are an \(n\) number of such rectangles underneath this quarter-ellipse along the interval \(Δx=3-0\).  </image:caption>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/solidsofrevolution/2017/10/6/calculating-the-volume-of-a-sphere-e6jde-mcsyn</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-09</lastmod>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59fd1ae6e2c483f6d02e5cf9/1507412420221/moment-of-inertia-of-sphere.jpg</image:loc>
      <image:title>Solids of Revolution - Calculating the Volume of a Sphere</image:title>
      <image:caption>Figure 4: By taking the infinite sum of the volumes, \(π(f(x))^2dx\), of every cylinder from \(x=0\) to \(x=R\), we can obtain the volume of half of the sphere depicted above. By multiplying our answer by two, we can obtain the volume of the whole sphere. Image credit: https://www.miniphysics.com/uy1-calculation-of-moment-of-inertia-of-solid-sphere.html</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59fd1ae6e2c483f6d02e5cf1/1507501386946/sdf.jpg</image:loc>
      <image:title>Solids of Revolution - Calculating the Volume of a Sphere</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59fd1ae6e2c483f6d02e5cf3/1507412420207/320px-Rotationskoerper_animation.gif</image:loc>
      <image:title>Solids of Revolution - Calculating the Volume of a Sphere</image:title>
      <image:caption>Figure 1: The "vase" shaped surface is obtained by revolving a curve about the vertical axis. The region of space that the surface encloses is called a solid of revolution.</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59fd1ae6e2c483f6d02e5cf5/1507412420213/volumeofsphereimg1.jpg</image:loc>
      <image:title>Solids of Revolution - Calculating the Volume of a Sphere</image:title>
      <image:caption>Figure 2: A graph of the quarter circle \(x^2+y^2=r^2\) for \(x≥0\) and \(y≥0\). An \(n\) number of rectangles, \(f(x_i\)Δx\), are drawn underneath the curve.</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59fd1ae6e2c483f6d02e5cf7/1507412420216/s9NuK.jpg</image:loc>
      <image:title>Solids of Revolution - Calculating the Volume of a Sphere</image:title>
      <image:caption>Figure 3: By rotating the \(i^{th}\) rectangle about the \(x\)-axis, the cylinder depicted above is obtained. By doing this for each rectangle, an \(n\) number of cylinders are obtained. All of these cylinders fit inside of a hemisphere of radius \(r\) and the sum of the volumes of all of those cylinders approximate the volume of the hemisphere.</image:caption>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/arc-length</loc>
    <changefreq>daily</changefreq>
    <priority>0.75</priority>
    <lastmod>2017-10-10</lastmod>
  </url>
  <url>
    <loc>https://www.gregschool.org/pulley-and-incline-problems</loc>
    <changefreq>daily</changefreq>
    <priority>0.75</priority>
    <lastmod>2017-10-07</lastmod>
  </url>
  <url>
    <loc>https://www.gregschool.org/articles9blog</loc>
    <changefreq>daily</changefreq>
    <priority>0.75</priority>
    <lastmod>2019-03-21</lastmod>
  </url>
  <url>
    <loc>https://www.gregschool.org/articles9blog/2017/2/13/introduction-to-einsteins-theory-of-general-relativity</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-09</lastmod>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/58dac9e2be6594b226ab6aec/1510178006735/</image:loc>
      <image:title>articles page 9 - Introduction to Einstein's Theory of General Relativity</image:title>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/articles9blog/2017/4/27/colonizing-the-asteroids-and-comets-of-our-solar-system</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-09</lastmod>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59dd21c880bd5e3fd03f894a/1510177997939/space+travela+nd+colonization+thumbnail.jpg</image:loc>
      <image:title>articles page 9 - Colonizing the Asteroids and Comets of our Solar System</image:title>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5904f28029687f041ca549d9/1510177997941/</image:loc>
      <image:title>articles page 9 - Colonizing the Asteroids and Comets of our Solar System</image:title>
      <image:caption>Figure 1 (click to enlarge)</image:caption>
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    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/590283f76b8f5be39de0ffbf/1510177997943/WANDERERS_terrarium_01.jpg</image:loc>
      <image:title>articles page 9 - Colonizing the Asteroids and Comets of our Solar System</image:title>
      <image:caption>Figure 2 - click to enlarge (Source) "This shot shows the inside of the asteroid from the previous scene. Just as I wrote about that scene, this is a highly speculative vision of an impressive piece of human engineering - a concept that science fiction author Kim Stanley Robinson calls a "terraruim" in his novel "2312". It is also not unlike what Arthur C. Clarke described in his novel "Rendezvous with Rama". What we see here is the inside of a hollowed out asteroid, pressurized and filled with a breathable atmosphere. Like I described in the previous scene, the whole structure is put into a revolving rotation, simulating the effect of gravity toward the inside "walls" of the cylinder shape we see. The structure in this scene has a diameter of about 7 kilometers and revolves with a speed of 1 rotation every 2 minutes, simulating the effect of 1g (the gravity pull we feel on Earth) at the surface of the inside. This place is also filled with water, creating lakes and seas wrapped along with the landscape. An artificial sun is running along a rail in the middle of the space, simulating a daylight cycle. This scene is of course built from scratch, but I used countless satellite photos of the Earth to texture the landscape. I actually used a slightly warped world map to create the outlines between land and water, as some may notice a couple of familiar shorelines."\(^{[3]}\)</image:caption>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/articles9blog/2017/5/4/colonizing-the-moon</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-09</lastmod>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/590c101dbe659408c6859363/590d02ff2994cac296bf1023/1498698373172/.jpg</image:loc>
      <image:title>articles page 9 - Colonizing the Moon</image:title>
      <image:caption>The Smart Things Future Living Report</image:caption>
    </image:image>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/590c101dbe659408c6859363/590c105be6f2e13e8402dcac/1498698373171/landscape-1436809198-1197px-inflatable-habitat-s89-20084.jpg</image:loc>
      <image:title>articles page 9 - Colonizing the Moon</image:title>
      <image:caption>Artist concept of a moon colony via NASA</image:caption>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/590c101dbe659408c6859363/590c103a893fc0ef1a3691de/1498698373169/LeapOfFaith.jpg</image:loc>
      <image:title>articles page 9 - Colonizing the Moon</image:title>
      <image:caption>Painting by Pat Rawlings courtesy NASA</image:caption>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/590c101dbe659408c6859363/590c101d20099e8a5502e809/1498698373166/LunarColonyRawlings650.jpg</image:loc>
      <image:title>articles page 9 - Colonizing the Moon</image:title>
      <image:caption>Domed lunar settlement illustration by Pat Rawlings, courtesy NASA.</image:caption>
    </image:image>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59dd2126be42d6ad78e8e1ef/1510177977619/space+travela+nd+colonization+thumbnail.jpg</image:loc>
      <image:title>articles page 9 - Colonizing the Moon</image:title>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/articles9blog/2017/6/8/early-earth-history</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-09</lastmod>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/593addbf725e25a4294e7e2a/1510177967240/Archean.png</image:loc>
      <image:title>articles page 9 - Early Earth History</image:title>
      <image:caption>Click to enlarge - (Source\(^{[2]}\))</image:caption>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/593a328c6a4963644179b180/1510177967236/</image:loc>
      <image:title>articles page 9 - Early Earth History</image:title>
      <image:caption>Click to enlarge - (Source\(^{[2]}\))</image:caption>
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      <image:title>articles page 9 - Early Earth History</image:title>
      <image:caption>Modern stromatolites in Shark Bay, Western Australia.</image:caption>
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  </url>
  <url>
    <loc>https://www.gregschool.org/articles9blog/2017/6/12/snowball-earth</loc>
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    <priority>0.5</priority>
    <lastmod>2017-11-09</lastmod>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/593efd59440243f1b89935ac/1510177949269/</image:loc>
      <image:title>articles page 9 - Snowball Earth</image:title>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/593efc13e4fcb594910df733/1510177949267/</image:loc>
      <image:title>articles page 9 - Snowball Earth</image:title>
      <image:caption>Picture of Earth 750 million years ago when the supercontinent Rodinia was getting torn apart. (Click to expand.)</image:caption>
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  </url>
  <url>
    <loc>https://www.gregschool.org/articles9blog/2017/8/26/work-measure-of-energy-transfer-5kccp</loc>
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    <priority>0.5</priority>
    <lastmod>2017-11-09</lastmod>
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      <image:title>articles page 9 - Work: Measure of Energy Transfer</image:title>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59b03468d7bdce7d68cac713/1504544870969/ff.png</image:loc>
      <image:title>articles page 9 - Work: Measure of Energy Transfer</image:title>
      <image:caption>Figure 1: Work done on a block by a constant force of \(-10\) newtons over a displacement of \(5\) meters.</image:caption>
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  </url>
  <url>
    <loc>https://www.gregschool.org/articles9blog/2017/5/14/genesis-of-the-elements-xz53h</loc>
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    <priority>0.5</priority>
    <lastmod>2017-11-09</lastmod>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a009a5171c10bb0d5b68e8f/1509981827221/RutherfordGoilFoil+%281%29%5B1%5D.jpg</image:loc>
      <image:title>articles page 9 - Genesis of the Elements</image:title>
      <image:caption>Figure 1: Rutherford's experiment involved putting a radioactive element known as radium inside of a lead box. The radium spontaneously emitted \(α\) particles in a narrow beam through a small hole in the box. These \(α\) particles were directed towards a gold foil. Most \(α\) particles passed straight through the gold foil but occasional one would get reflected back at an acute angle with the beam of \(α\) particles. This meant that atoms must have tiny, but very dense, nuclei. Image credit: http://m.teachastronomy.com/astropedia/article/The-Structure-of-the-Atom</image:caption>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a009a5171c10bb0d5b68e95/1509987202844/</image:loc>
      <image:title>articles page 9 - Genesis of the Elements</image:title>
      <image:caption>Figure 4: As a star undergoes nuclear fusion in its core, it generates light. This light exerts an outward radiation pressure on the star which balances the inward gravitational forces that tend to pull the star's matter towards its center. But at the end of a star's life, nuclear fusion begins to slow down and eventually stop; this means that there is no outward radiation pressure to balance the gravitational forces exerted on the outward layers of the star and star eventually collapses. If the star is very massive, such a collapse will result in one of the most spectacular events in the universe: a supernova. The energy generated by a supernova explosion is so stupendous that it results in nuclear reactions which create the heavier elements in the period table.</image:caption>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a009a5171c10bb0d5b68e93/1509985102690/</image:loc>
      <image:title>articles page 9 - Genesis of the Elements</image:title>
      <image:caption>Figure 3: The Alpha-Beta-Gamma paper demonstrated that after the first roughly three minutes of the universe since its initial Bang, hydrogen and helium nuclei were synthesized via nuclear fusion. After about three minutes, the universe cooled enough for fusion to stop; but the universe was still so hot that all of the matter comprising the universe was a plasma and plasma's are opaque to radiation. The matter comprising the universe was in a plasma state for the first roughly 300,000 years since the Big Bang; since plasma is opaque to radiation, for the first roughly 300,000 years light could not freely travel throughout the universe without constantly "bumping into stuff (atomic nuclei)." At sometime when the universe was about 300,000 to 400,000 years old, matter cooled enough for electrons to bind to atomic nuclei and for light to freely pass through the universe. Due to the expansion of space, Alpher and Herman estimated that wavelengths of this light should now be stretched into the microwave region.</image:caption>
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    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a009a5171c10bb0d5b68e91/1509983399387/nuclear-fusion-stars%5B1%5D.png</image:loc>
      <image:title>articles page 9 - Genesis of the Elements</image:title>
      <image:caption>Figure 2: All stars in the universe generate light and energy by fusing lighter elements into heavier elements. For stars up to the mass of about that of our Sun, light and energy is created by fusing hydrogen into helium. The image above illustrates the chain of nuclear reactions which occur in small to medium sized stars and very massive stars that allow them to generate light and energy. Stellar fusion accounts for where many of the light to medium-sized elements in the periodic table come from.</image:caption>
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  </url>
  <url>
    <loc>https://www.gregschool.org/articles9blog/2017/6/21/the-dependency-of-theta-in-the-dot-product-a6rdd</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-09</lastmod>
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      <image:title>articles page 9 - The Dependency of theta in the dot product</image:title>
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      <image:title>articles page 9 - The Dependency of theta in the dot product</image:title>
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  </url>
  <url>
    <loc>https://www.gregschool.org/articles9blog/2017/8/27/work-done-by-force-moving-an-object-at-constant-height-dxkzp</loc>
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    <priority>0.5</priority>
    <lastmod>2017-11-09</lastmod>
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      <image:title>articles page 9 - Work-Kinetic Energy Theorem</image:title>
      <image:caption>Figure 1: "Sunil Kumar Singh, Work - Kinetic Energy Theorem. February 2, 2013." http://cnx.org/content/m14095/latest/OpenStax CNX CC BY 3.0.</image:caption>
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      <image:title>articles page 9 - Work-Kinetic Energy Theorem</image:title>
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  </url>
  <url>
    <loc>https://www.gregschool.org/articles9blog/2017/8/26/work-done-by-earths-gravity-nfmxr</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-09</lastmod>
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      <image:title>articles page 9 - Work done by Earth's Gravity</image:title>
      <image:caption>Figure 1: As an object moves along the path \(\vec{R}(t)\) from an initial height of \(y_i\) to a final height of \(y_f\), the Earth's gravitational force \(-m\vec{g}\) does work on the object.</image:caption>
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      <image:title>articles page 9 - Work done by Earth's Gravity</image:title>
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  </url>
  <url>
    <loc>https://www.gregschool.org/optimization-problems</loc>
    <changefreq>daily</changefreq>
    <priority>0.75</priority>
    <lastmod>2017-11-02</lastmod>
  </url>
  <url>
    <loc>https://www.gregschool.org/optimization-problems/2017/10/14/maximizing-the-area-of-a-rectangle</loc>
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    <priority>0.5</priority>
    <lastmod>2017-11-08</lastmod>
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      <image:title>Optimization Problems - Maximizing the Area of a Rectangle</image:title>
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      <image:title>Optimization Problems - Maximizing the Area of a Rectangle</image:title>
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      <image:title>Optimization Problems - Maximizing the Area of a Rectangle</image:title>
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      <image:title>Optimization Problems - Maximizing the Area of a Rectangle</image:title>
      <image:caption>Figure 1: Given any rectangle \(xy\) where the perimeter \(2x+2y\) is the constant, we can use calculus to find that particular rectangle \(xy\) with the maximum area \(A\). The solution to this problem has practical applications. For example, suppose that someone had only 30 meters of fencing to enclose their backyard and they wanted to know what fencing layout would maximize the size and total area of their backyard.</image:caption>
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      <image:title>Optimization Problems - Maximizing the Area of a Rectangle</image:title>
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      <image:title>Optimization Problems - Maximizing the Area of a Rectangle</image:title>
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      <image:title>Optimization Problems - Maximizing the Area of a Rectangle</image:title>
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  </url>
  <url>
    <loc>https://www.gregschool.org/optimization-problems/2017/10/14/optimizatio</loc>
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    <priority>0.5</priority>
    <lastmod>2017-11-08</lastmod>
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      <image:title>Optimization Problems - Optimization Problem</image:title>
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      <image:title>Optimization Problems - Optimization Problem</image:title>
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      <image:title>Optimization Problems - Optimization Problem</image:title>
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      <image:title>Optimization Problems - Optimization Problem</image:title>
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      <image:title>Optimization Problems - Optimization Problem</image:title>
      <image:caption>Figure 1: A graph of the circle \(x^2+y^2=4\) which is centered at the origin of the \(x\)-axis. If \((x,y)\) represents any point on the circle, if \(P\) is a point fixed at the coordinate point \((4,0)\), and if \(d\) represents the distance between those two points then, by using only calculus, we can find the point \((x,y)\) on the circle associated with the minimum distance \(d\).</image:caption>
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      <image:title>Optimization Problems - Optimization Problem</image:title>
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      <image:title>Optimization Problems - Optimization Problem</image:title>
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  </url>
  <url>
    <loc>https://www.gregschool.org/optimization-problems/2017/10/30/derivation-of-snells-law</loc>
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    <priority>0.5</priority>
    <lastmod>2017-11-09</lastmod>
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      <image:title>Optimization Problems - Derivation of Snell's Law</image:title>
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      <image:title>Optimization Problems - Derivation of Snell's Law</image:title>
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      <image:title>Optimization Problems - Derivation of Snell's Law</image:title>
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      <image:title>Optimization Problems - Derivation of Snell's Law</image:title>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59f88cbf53450a66f3f4a05e/1509495184214/snellslaw2.jpg</image:loc>
      <image:title>Optimization Problems - Derivation of Snell's Law</image:title>
      <image:caption>Figure 1: A light ray traveling along the line \(QO\) comes into contact with a surface at an \(θ_i\) (where \(θ_i\) is measured relative to the line perpendicular to the surface). Once this light ray comes into contact with this surface, it is reflected at an angle \(θ_r\) (\(θ_r\) is also measured relative to the perpendicular). According to the law of reflection, \(θ_i=θ_r\). Image credit: Download for free at http://cnx.org/contents/60b4727b-829e-4ea7-9238-9140b6a1b20c@4.</image:caption>
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      <image:title>Optimization Problems - Derivation of Snell's Law</image:title>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59f88981e2c48368e55888e3/1509495184220/snells+law.jpg</image:loc>
      <image:title>Optimization Problems - Derivation of Snell's Law</image:title>
      <image:caption>Figure 2: As a light ray travels along the line \(QO\) through medium 1 and comes into contact with the interface between medium 1 and medium 2, it gets refracted—meaning, it passes through medium 2. Image credit: By Smedlib (Own work) [CC BY-SA 4.0 (https://creativecommons.org/licenses/by-sa/4.0)], via Wikimedia Commons</image:caption>
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      <image:title>Optimization Problems - Derivation of Snell's Law</image:title>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/optimization-problems/2017/6/24/finding-the-minima-and-maxima-of-a-function</loc>
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    <priority>0.5</priority>
    <lastmod>2017-11-08</lastmod>
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      <image:title>Optimization Problems - Finding the Minima and Maxima of a Function</image:title>
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      <image:title>Optimization Problems - Finding the Minima and Maxima of a Function</image:title>
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      <image:title>Optimization Problems - Finding the Minima and Maxima of a Function</image:title>
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      <image:title>Optimization Problems - Finding the Minima and Maxima of a Function</image:title>
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  </url>
  <url>
    <loc>https://www.gregschool.org/articles-page-10</loc>
    <changefreq>daily</changefreq>
    <priority>0.75</priority>
    <lastmod>2019-03-21</lastmod>
  </url>
  <url>
    <loc>https://www.gregschool.org/articles-page-10/2017/1/23/superconductors-the-future-of-transportation-and-electric-transmission</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-09</lastmod>
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      <image:title>articles page 10 - Superconductors: the Future of Transportation and Electric Transmission</image:title>
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      <image:title>articles page 10 - Superconductors: the Future of Transportation and Electric Transmission</image:title>
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      <image:title>articles page 10 - Superconductors: the Future of Transportation and Electric Transmission</image:title>
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      <image:title>articles page 10 - Superconductors: the Future of Transportation and Electric Transmission</image:title>
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      <image:title>articles page 10 - Superconductors: the Future of Transportation and Electric Transmission</image:title>
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      <image:title>articles page 10 - Superconductors: the Future of Transportation and Electric Transmission</image:title>
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  </url>
  <url>
    <loc>https://www.gregschool.org/articles-page-10/2017/6/12/crispr-cas9-gene-editing</loc>
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    <priority>0.5</priority>
    <lastmod>2017-11-09</lastmod>
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      <image:title>articles page 10 - CRISPR-CAS9 Gene Editing</image:title>
      <image:caption>Figure 1                            Source\(^{[1]}\)</image:caption>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/593f60523a041171e036d6d3/1510178188884/rrr.png</image:loc>
      <image:title>articles page 10 - CRISPR-CAS9 Gene Editing</image:title>
      <image:caption>Figure 3                                         Source</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/593f5f6f59cc6882f35c19d2/1510178188881/</image:loc>
      <image:title>articles page 10 - CRISPR-CAS9 Gene Editing</image:title>
      <image:caption>Figure 2                                          Source</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/593f609a8419c276ef634893/1510178188888/</image:loc>
      <image:title>articles page 10 - CRISPR-CAS9 Gene Editing</image:title>
      <image:caption>Figure 4 (click to enlarge)</image:caption>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/articles-page-10/2017/6/16/overview-of-calculus-hmtnx</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-09</lastmod>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59dbdcbb29f1876a457f9167/1510078784067/Untitled.jpg</image:loc>
      <image:title>articles page 10 - Overview of Single-Variable Calculus</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59a39f767131a55eb412021e/1497934480889/</image:loc>
      <image:title>articles page 10 - Overview of Single-Variable Calculus</image:title>
      <image:caption>Figure 1</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59a39f767131a55eb4120226/1497933579348/</image:loc>
      <image:title>articles page 10 - Overview of Single-Variable Calculus</image:title>
      <image:caption>Figure 5</image:caption>
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    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59a39f767131a55eb4120220/1497934508324/</image:loc>
      <image:title>articles page 10 - Overview of Single-Variable Calculus</image:title>
      <image:caption>Figure 2</image:caption>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59a39f767131a55eb4120224/1497933573517/</image:loc>
      <image:title>articles page 10 - Overview of Single-Variable Calculus</image:title>
      <image:caption>Figure 4</image:caption>
    </image:image>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59a39f767131a55eb4120222/1497931192368/</image:loc>
      <image:title>articles page 10 - Overview of Single-Variable Calculus</image:title>
      <image:caption>Figure 3</image:caption>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/articles-page-10/2017/5/15/periodic-wavefunctions-that-is-ones-that-come-back-to-themselves-have-quantized-eigenvalues-of-momenta-and-angular-momenta-2k3el</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-09</lastmod>
  </url>
  <url>
    <loc>https://www.gregschool.org/articles-page-10/2017/5/14/how-initial-states-of-definite-energy-change-with-time-5hyrx</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-11</lastmod>
  </url>
  <url>
    <loc>https://www.gregschool.org/articles-page-10/2017/5/14/quantum-dynamics-2nhll</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-11</lastmod>
  </url>
  <url>
    <loc>https://www.gregschool.org/articles-page-10/2017/5/23/the-eigenvectors-of-any-hermitian-operator-must-be-orthogonal-w2jps</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-09</lastmod>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59dc4e8a1f318db010fe3230/1510110338040/electromagnetism+thumbnaillllll+imageeee.jpg</image:loc>
      <image:title>articles page 10 - The Eigenvectors of any Hermitian Operator must be Orthogonal</image:title>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/articles-page-10/2017/5/27/origin-of-structure-and-clumpyness-dbe4t</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-11</lastmod>
  </url>
  <url>
    <loc>https://www.gregschool.org/articles-page-10/2017/5/15/time-evolution-of-state-vectors-c6g7n</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-09</lastmod>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a026de4652dea4ceb35eb78/1510108488383/photon_double_slit2%5B1%5D.gif</image:loc>
      <image:title>articles page 10 - Schrodinger's Time-Dependent Equation: Time-Evolution of State Vectors</image:title>
      <image:caption>Figure 2: Schrodinger's equation is deterministic because the past or future quantum state \(|\psi(t)⟩\) of a quantum system can be determined with infinite precision. But, in general, a quantum system can be in a superposition of many different states where the measurement of any physical quantity is uncertain. For example, if anything the size of a small molecule or smaller passes through a double-slit in a double-slit experiment, where it hits the screen (which is to say, its final position) is uncertain (see illustration above). The quantum state of a quantum system is deterministic; but the eigenvalue that you'll measure after an experiment is done is the quantity which is not deterministic in quantum mechanics. Source: http://abyss.uoregon.edu/~js/21st_century_science/lectures/lec13.html</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a026de4652dea4ceb35eb76/1510107139616/1_Lwu5UJMmcuFVJLZ1Ln4E0Q%5B1%5D.png</image:loc>
      <image:title>articles page 10 - Schrodinger's Time-Dependent Equation: Time-Evolution of State Vectors</image:title>
      <image:caption>Figure 1: The motion of a simple pendulum is an example of the time-reversibility of Newton's second law. Given the initial state of the pendulum, Newton's second law can be used to determine the past or future state of the system. For example, one could determine the velocity and position of the pendulum at any past or future time given its present state.</image:caption>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/articles-page-10/2017/5/23/calculating-the-wavefunction-collection-of-probability-amplitudes-associated-with-any-ket-vector-skh4m-ey7ag</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-09</lastmod>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a027ccae2c48322bcc11559/1507610296214/electromagnetism+thumbnaillllll+imageeee.jpg</image:loc>
      <image:title>articles page 10 - Calculating the Wavefunction Associated with any Ket Vector</image:title>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/chain-rule</loc>
    <changefreq>daily</changefreq>
    <priority>0.75</priority>
    <lastmod>2017-11-05</lastmod>
  </url>
  <url>
    <loc>https://www.gregschool.org/chain-rule/2017/11/2/how-fast-does-water-rise-up-a-cone-tca7n</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-09</lastmod>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59ff7eeae4966b0f258977ea/1509916111643/share+calculus+img.png</image:loc>
      <image:title>Chain rule - How Fast Does Water Rise Up a Cone?</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59ff7eeae4966b0f258977ee/1509916171756/twiiter+img+thumbnail.jpg</image:loc>
      <image:title>Chain rule - How Fast Does Water Rise Up a Cone?</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59ff7eeae4966b0f258977f0/1509916335679/google+img+thumbnail.jpg</image:loc>
      <image:title>Chain rule - How Fast Does Water Rise Up a Cone?</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59ff7eeae4966b0f258977f6/1509910135829/flow-rate-cone.gif</image:loc>
      <image:title>Chain rule - How Fast Does Water Rise Up a Cone?</image:title>
      <image:caption>Figure 1: Water being poured into a rectangular box with dimensions \(4ft×4ft×h\) at a rate of \(\frac{dV}{dt}=4\frac{ft^3}{min}\). The container at time \(t=0\) starts out empty.</image:caption>
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      <image:title>Chain rule - How Fast Does Water Rise Up a Cone?</image:title>
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      <image:title>Chain rule - How Fast Does Water Rise Up a Cone?</image:title>
    </image:image>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59ff7eeae4966b0f258977f4/1509915966119/Calculus+thumbnail.png</image:loc>
      <image:title>Chain rule - How Fast Does Water Rise Up a Cone?</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59ff7eeae4966b0f258977f8/1509906523011/flow-rate-cone.gif</image:loc>
      <image:title>Chain rule - How Fast Does Water Rise Up a Cone?</image:title>
      <image:caption>Figure 2: Water is poured into a cone of height \(h\) and radius \(r\) at a rate of \(\frac{dV}{dt}=4\frac{ft^3}{min}. The height of the water is given by \(y\). This image was modified under a Create Commons license. Image credit: https://www.mathalino.com/blog/romel-verterra/calculator-technique-solving-volume-flow-rate-problems-calculus</image:caption>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/gregschoollessons</loc>
    <changefreq>daily</changefreq>
    <priority>0.75</priority>
    <lastmod>2020-06-16</lastmod>
  </url>
  <url>
    <loc>https://www.gregschool.org/gregschoollessons/2018/6/12/shkadov-thrusters</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2018-07-06</lastmod>
  </url>
  <url>
    <loc>https://www.gregschool.org/gregschoollessons/2018/7/5/proof-of-the-theorem-fracsinxx1</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2018-07-19</lastmod>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5b4ff1de03ce6465a2fc5403/1532040995867/twiiter+img+thumbnail.jpg</image:loc>
      <image:title>gregschool-lessons - Proof of the Theorem: \(\lim_{ϴ→0}\frac{sinϴ}{ϴ}=1\)</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5b3e6ab92b6a28dc000daaa8/1532040995874/squeezzeee.png</image:loc>
      <image:title>gregschool-lessons - Proof of the Theorem: \(\lim_{ϴ→0}\frac{sinϴ}{ϴ}=1\)</image:title>
      <image:caption>Figure 2: As you can see graphically, for values of \(ϴ\) in the range \(\frac{-π}{2}&lt;ϴ&lt;\frac{π}{2}\), the following inequalities are true \(1≥\frac{sinϴ}{ϴ}≥cosϴ\). Notice that as \(ϴ\) approaches zero from both the negative and positive directions, the function \(\frac{sinϴ}{ϴ}\) gets "squeezed" into the same point on the graph.</image:caption>
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      <image:title>gregschool-lessons - Proof of the Theorem: \(\lim_{ϴ→0}\frac{sinϴ}{ϴ}=1\)</image:title>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5b44efc81ae6cff42b6ec0bf/1532040995872/Limit_of_Sine_of_X_over_X-Proof_3.png</image:loc>
      <image:title>gregschool-lessons - Proof of the Theorem: \(\lim_{ϴ→0}\frac{sinϴ}{ϴ}=1\)</image:title>
      <image:caption>Figure 1: The wedge \(⪦OBA\) (colored blue) comprises a portion of the unit circle. The lengths \(AB\) and \(AC\) are the radius of the unit circle and are therefore equal to one. The heights of the triangles \(△OBA\) and \(△OCA\) can be found using basic trigonometry.</image:caption>
    </image:image>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5b4ff0c6758d46506ec951fa/1532040995871/Calculus+thumbnail.png</image:loc>
      <image:title>gregschool-lessons - Proof of the Theorem: \(\lim_{ϴ→0}\frac{sinϴ}{ϴ}=1\)</image:title>
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      <image:title>gregschool-lessons - Proof of the Theorem: \(\lim_{ϴ→0}\frac{sinϴ}{ϴ}=1\)</image:title>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5b4ff11f03ce6465a2fc38d3/1532040995860/share+calculus+img.png</image:loc>
      <image:title>gregschool-lessons - Proof of the Theorem: \(\lim_{ϴ→0}\frac{sinϴ}{ϴ}=1\)</image:title>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5b4ff247758d46506ec98957/1532040995863/facebook+img+thumbnail.jpg</image:loc>
      <image:title>gregschool-lessons - Proof of the Theorem: \(\lim_{ϴ→0}\frac{sinϴ}{ϴ}=1\)</image:title>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/gregschoollessons/2019/2/7/leaving-the-solar-system</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2019-02-24</lastmod>
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      <image:title>gregschool-lessons - Leaving the Solar System: Introduction to the Outward Bound Series</image:title>
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      <image:title>gregschool-lessons - Leaving the Solar System: Introduction to the Outward Bound Series</image:title>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5c5cb052f4e1fcec460236fb/1550429768522/WH-Phoebe-1024x599%5B1%5D.jpg</image:loc>
      <image:title>gregschool-lessons - Leaving the Solar System: Introduction to the Outward Bound Series</image:title>
      <image:caption>Image retrieved from: https://crossingzebras.com/wormhole-space-after-phoebe/</image:caption>
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      <image:title>gregschool-lessons - Leaving the Solar System: Introduction to the Outward Bound Series</image:title>
      <image:caption>A gravitational lens telescope, as envisioned by Claudio Maccone in his 2009 book Deep Space Flight and Communications. (Claudio Maccone)</image:caption>
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      <image:title>gregschool-lessons - Leaving the Solar System: Introduction to the Outward Bound Series</image:title>
      <image:caption>The Wright brothers on the steps of their boyhood home at 7 Hawthorn St. in Dayton.\(^{[1]}\) Carillon Historical Park</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/5c5cb1e4e5e5f09c9b9ab007/5c5cb1e4e4966b3a9884e747/1550429768539/This-is-How-Earth-Moves-1.jpg</image:loc>
      <image:title>gregschool-lessons - Leaving the Solar System: Introduction to the Outward Bound Series</image:title>
      <image:caption>This image illustrates the fact that the Sun is actually moving through space relative to the Milky Way galaxy; from this frame of reference, the Earth is moving in a spiral-shaped path. Of course, we can actually alter this path as well as the Sun’s speed using a type of megastructure known as a Shkadov thruster; you could, in fact, give the Sun (and the Earth which goes around it) a radically different path which heads off-course away from the galaxy. Image retrieved from: https://wordlesstech.com/this-is-how-earth-moves/</image:caption>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/5c5c88186e9a7f7629ce39c3/5c5c881853450aa0aa44e214/1550429768528/034-035_AAS_024%5B1%5D.jpg</image:loc>
      <image:title>gregschool-lessons - Leaving the Solar System: Introduction to the Outward Bound Series</image:title>
      <image:caption>Infographic retrieved from: https://www.spaceanswers.com/issue-previews/5025/5025/</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5c5c84bd9b747a54aaaa7950/1550429768524/quote-the-moral-landscape-is-the-framework-i-use-for-thinking-about-questions-of-morality-sam-harris-12-51-41%5B1%5D.jpg</image:loc>
      <image:title>gregschool-lessons - Leaving the Solar System: Introduction to the Outward Bound Series</image:title>
      <image:caption>Quote by Sam Harris, author of the book, The Moral Landscape.</image:caption>
    </image:image>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/5c5c833ab208fccb907b9a26/5c5c833b53450aa0aa449ec4/1550429768519/84v8X%5B1%5D.jpg</image:loc>
      <image:title>gregschool-lessons - Leaving the Solar System: Introduction to the Outward Bound Series</image:title>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/gregschoollessons/2018/6/20/the-diversity-of-exoplanets-in-the-galaxy</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2019-04-01</lastmod>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5b47dee2758d462b097c5dbf/1532041055813/pular+planet.png</image:loc>
      <image:title>gregschool-lessons - The Diversity of Exoplanets in the Galaxy</image:title>
      <image:caption>Artist's conception of a planet orbiting a Pulsar. The Pulsar's radiation blasting the exoplanet would cause its surface to glow.</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5b3d4c9e575d1fd7a47b9757/1532041055839/trappist.png</image:loc>
      <image:title>gregschool-lessons - The Diversity of Exoplanets in the Galaxy</image:title>
      <image:caption>This artist's concept shows what the TRAPPIST-1 planetary system may look like, based on available data about the planets' diameters, masses and distances from the host star. Credits: NASA/JPL-Caltech View full image and caption</image:caption>
    </image:image>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/5b33fb8770a6ad47c2974f19/5b33fb871ae6cf9caeda770d/1532041055805/image_4610_3e-Europa-Lander%5B1%5D.jpg</image:loc>
      <image:title>gregschool-lessons - The Diversity of Exoplanets in the Galaxy</image:title>
      <image:caption />
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/5b33fb8770a6ad47c2974f19/5b34019c2b6a2849de2b95a3/1532041055809/PIA19058-SaturnMoon-Enceladus-PossibleHydrothermalActivity-ArtistConcept-20150311%5B2%5D.jpg</image:loc>
      <image:title>gregschool-lessons - The Diversity of Exoplanets in the Galaxy</image:title>
      <image:caption>Artists impressions of subsurface oceans underneath thick ice sheets on Jupiter’s moon Europa and Saturn’s moon Enceladus. Top image by NASA.</image:caption>
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      <image:title>gregschool-lessons - The Diversity of Exoplanets in the Galaxy</image:title>
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      <image:title>gregschool-lessons - The Diversity of Exoplanets in the Galaxy</image:title>
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      <image:title>gregschool-lessons - The Diversity of Exoplanets in the Galaxy</image:title>
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      <image:title>gregschool-lessons - The Diversity of Exoplanets in the Galaxy</image:title>
      <image:caption>Artist's depiction of the exoplanet 55 Cancri E. Image credit: ESA/Hubble [CC BY 4.0 (https://creativecommons.org/licenses/by/4.0)], via Wikimedia Commons.</image:caption>
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      <image:title>gregschool-lessons - The Diversity of Exoplanets in the Galaxy</image:title>
      <image:caption>Image of auroras just above the Earth's surface obtained by the International Space Station. Image credit: NASA</image:caption>
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      <image:title>gregschool-lessons - The Diversity of Exoplanets in the Galaxy</image:title>
      <image:caption>This poster imagines what a trip to TRAPPIST-1e might be like. Credits: NASA/JPL-Caltech View full image</image:caption>
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      <image:title>gregschool-lessons - The Diversity of Exoplanets in the Galaxy</image:title>
      <image:caption>Graphite (left) and diamond (right) are both, essentially, just made up of a bunch of carbon atoms. The difference between the two substances is how those carbon atoms are arranged.</image:caption>
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      <image:title>gregschool-lessons - The Diversity of Exoplanets in the Galaxy</image:title>
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      <image:title>gregschool-lessons - The Diversity of Exoplanets in the Galaxy</image:title>
      <image:caption>Artist's impression of the Archipelago world, Kepler 186f. Credit: Danielle Futselaar</image:caption>
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      <image:title>gregschool-lessons - The Diversity of Exoplanets in the Galaxy</image:title>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5b33f9d488251b744df1cd00/1532041055818/Planets_everywhere_%28artist%E2%80%99s_impression%29%5B1%5D.jpg</image:loc>
      <image:title>gregschool-lessons - The Diversity of Exoplanets in the Galaxy</image:title>
      <image:caption>"This artist's cartoon view gives an impression of how common planets are around the stars in the Milky Way. The planets, their orbits and their host stars are all vastly magnified compared to their real separations. A six-year search that surveyed millions of stars using the microlensing technique concluded that planets around stars are the rule rather than the exception. The average number of planets per star is greater than one."\(^{[1]}\) Image credit: by ESO/M. Kornmesser (http://www.eso.org/public/images/eso1204a/) [CC BY 4.0 (https://creativecommons.org/licenses/by/4.0)], via Wikimedia Commons</image:caption>
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      <image:title>gregschool-lessons - The Diversity of Exoplanets in the Galaxy</image:title>
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      <image:title>gregschool-lessons - The Diversity of Exoplanets in the Galaxy</image:title>
      <image:caption>X-ray image of Pluto obtained by Chandra X-Ray Observatory (blue spot on right) and up-close photograph of Pluto obtained by the spacecraft Deep Horizons as it flew by Pluto.</image:caption>
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      <image:title>gregschool-lessons - The Diversity of Exoplanets in the Galaxy</image:title>
      <image:caption>Size comparison of Kepler-186f (artist's impression) with Earth along with their projected habitable zones.</image:caption>
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      <image:title>gregschool-lessons - The Diversity of Exoplanets in the Galaxy</image:title>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5b303e32758d46fa6607b4b4/1532041055816/aHR0cDovL3d3dy5zcGFjZS5jb20vaW1hZ2VzL2kvMDAwLzA2Mi8wODkvb3JpZ2luYWwvaG90LWp1cGl0ZXItY29uY2VwdGlvbi5qcGc%3D%5B1%5D.jpg</image:loc>
      <image:title>gregschool-lessons - The Diversity of Exoplanets in the Galaxy</image:title>
      <image:caption>Artist's depiction of a so-called hot Jupiter orbiting its planet star.</image:caption>
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  </url>
  <url>
    <loc>https://www.gregschool.org/gregschoollessons/2017/9/11/harvesting-resources-from-saturn-and-titan-l5msz-te4fd</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-12-11</lastmod>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a03767d8165f5ed71a9742a/1513008775554/WANDERERS_ligeia_mare_01.jpg</image:loc>
      <image:title>gregschool-lessons - Harvesting Resources from Saturn and Titan</image:title>
      <image:caption>"With an average temperature of -180 C all water here is frozen hard as rock. In fact, the surface landscape of Titan is indeed mostly made of frozen water ice. But Titan's atmosphere is rich in hydrocarbons such as methane and ethane, and the low temperature is perfect for these elements to occur naturally in three states; frozen, liquid and gas. So, just as on Earth where we have a water cycle (ice melts, becomes water, water evaporates into clouds, turning into liquid and becomes rain and so forth), Titan has a methane cycle. Methane evaporates and rises to form clouds, eventually turning into rain, falling over the surface. And this is the most amazing part; the rain in some places is enough to fill entire lakes. Lakes of methane! Titan is the only place in the Solar System, other than Earth, known to have large bodies of liquid on its surface. And they are really there, huge lakes, with shorelines, islands and small archipelagos. This scene takes place over a lake know as Ligeia Mare, the second largest on Titan, about 500 kilometers in diameter, located in the north polar region of the moon. The second fantastic feature I wanted to illustrate is the combination of Titan's very dense atmosphere and its relatively low gravity. As a human on Titan you would weigh about 14% of what you do on Earth, and in the dense atmosphere it would be enough to strap wings on your arms to make you able to fly like a bird. On Titan you could fly like a bird, over lakes of methane! (If you wore some really warm clothes of course.)" Image and image description credit: WANDERERS - a short film by EriK Wernquist</image:caption>
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      <image:title>gregschool-lessons - Harvesting Resources from Saturn and Titan</image:title>
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      <image:title>gregschool-lessons - Harvesting Resources from Saturn and Titan</image:title>
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      <image:title>gregschool-lessons - Harvesting Resources from Saturn and Titan</image:title>
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      <image:title>gregschool-lessons - Harvesting Resources from Saturn and Titan</image:title>
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      <image:title>gregschool-lessons - Harvesting Resources from Saturn and Titan</image:title>
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      <image:title>gregschool-lessons - Harvesting Resources from Saturn and Titan</image:title>
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    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a2eae9553450a8ff1cc6d61/1513008820293/neil-blevins-megastructures-9-gas-giant-refinery-design-packet%5B1%5D.jpg</image:loc>
      <image:title>gregschool-lessons - Harvesting Resources from Saturn and Titan</image:title>
      <image:caption>Artist's depiction of aerostats harvesting resources from a gas giant's atmosphere. Credit: https://www.artstation.com/artofsoulburn</image:caption>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/gregschoollessons/2017/11/2/how-fast-does-water-rise-up-a-cone-l22x2</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-12</lastmod>
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      <image:title>gregschool-lessons - How Fast Does Water Rise Up a Cone?</image:title>
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      <image:title>gregschool-lessons - How Fast Does Water Rise Up a Cone?</image:title>
    </image:image>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a03768a24a694f5e24e8710/1509916394700/flow-rate-cone.gif</image:loc>
      <image:title>gregschool-lessons - How Fast Does Water Rise Up a Cone?</image:title>
      <image:caption>Figure 1: Water being poured into a rectangular box with dimensions \(4ft×4ft×h\) at a rate of \(\frac{dV}{dt}=4\frac{ft^3}{min}\). The container at time \(t=0\) starts out empty.</image:caption>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a03768a24a694f5e24e8712/1509916394702/flow-rate-cone.gif</image:loc>
      <image:title>gregschool-lessons - How Fast Does Water Rise Up a Cone?</image:title>
      <image:caption>Figure 2: Water is poured into a cone of height \(h\) and radius \(r\) at a rate of \(\frac{dV}{dt}=4\frac{ft^3}{min}. The height of the water is given by \(y\). This image was modified under a Create Commons license. Image credit: https://www.mathalino.com/blog/romel-verterra/calculator-technique-solving-volume-flow-rate-problems-calculus</image:caption>
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      <image:title>gregschool-lessons - How Fast Does Water Rise Up a Cone?</image:title>
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      <image:title>gregschool-lessons - How Fast Does Water Rise Up a Cone?</image:title>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a03768a24a694f5e24e8704/1509916394688/share+calculus+img.png</image:loc>
      <image:title>gregschool-lessons - How Fast Does Water Rise Up a Cone?</image:title>
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      <image:title>gregschool-lessons - How Fast Does Water Rise Up a Cone?</image:title>
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  </url>
  <url>
    <loc>https://www.gregschool.org/gregschoollessons/2017/5/4/chaos-3gdk9</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-09</lastmod>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a037699ec212ddbe21808f6/1510175075096/share+chaos+theory+img.png</image:loc>
      <image:title>gregschool-lessons - Chaos and Fractals</image:title>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a037699ec212ddbe2180904/1510175075110/dice+game.jpg</image:loc>
      <image:title>gregschool-lessons - Chaos and Fractals</image:title>
      <image:caption>Figure 2: The three points \((1,2)\), \((3,4)\), and \((5,6)\) form an equilateral triangle. Choose any arbitrary point \((x,y)\) anywhere on the plane either inside or outside the triangle. If you rolled a 1 or 2, then draw a new point \((x_0,y_0)\) whose distance is half way between the points \((x,y)\) and \((1,2)\). Repeat this many times.</image:caption>
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      <image:title>gregschool-lessons - Chaos and Fractals</image:title>
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    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a037699ec212ddbe2180902/1510175075108/Edward_lorenz%5B1%5D.jpg</image:loc>
      <image:title>gregschool-lessons - Chaos and Fractals</image:title>
      <image:caption>Figure 1: "Edward Norton Lorenz (May 23, 1917 – April 16, 2008) was an American mathematician, meteorologist, and a pioneer of chaos theory, along with Mary Cartwright. He introduced the strange attractor notion and coined the term butterfly effect."\(^{[3]}\) This image is for educational purposes only. Image credit: https://history.aip.org/history/Thumbnails/lorenz_edward_a1.jpg</image:caption>
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      <image:title>gregschool-lessons - Chaos and Fractals</image:title>
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      <image:title>gregschool-lessons - Chaos and Fractals</image:title>
      <image:caption>Figure 3: After rolling the dice (and drawing a new point for each dice roll) billions of times, a fractal pattern known as the Siepinski triangle will eventually form. Remarkable! Image credit: by Beojan Stanislaus (Own work) [CC BY-SA 3.0 (https://creativecommons.org/licenses/by-sa/3.0)], via Wikimedia Commons.</image:caption>
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      <image:title>gregschool-lessons - Chaos and Fractals</image:title>
      <image:caption>Figure 4: An image of the Cantor set.</image:caption>
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      <image:title>gregschool-lessons - Chaos and Fractals</image:title>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a037699ec212ddbe21808fe/1510249147234/email+img+thumbnail.jpg</image:loc>
      <image:title>gregschool-lessons - Chaos and Fractals</image:title>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a037699ec212ddbe2180900/1510175075106/chaos+theory+thumbnail.png</image:loc>
      <image:title>gregschool-lessons - Chaos and Fractals</image:title>
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  </url>
  <url>
    <loc>https://www.gregschool.org/gregschoollessons/2017/10/22/partial-derivatives-6cjz9-njhjd</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-09</lastmod>
    <image:image>
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      <image:title>gregschool-lessons - Introduction to Partial Derivatives</image:title>
    </image:image>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a0376a88165f5ed71a97d6d/1508723598292/MSP5083101ccb77dc1c84hg00003d8bb0b0083b496c.gif</image:loc>
      <image:title>gregschool-lessons - Introduction to Partial Derivatives</image:title>
      <image:caption>Figure 1: Graph of the surface \(f(x,y)=x^2+y^2\). Image courtesy of Wolfram Alpha.</image:caption>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a0376a88165f5ed71a97d6b/1509828263016/Calculus+thumbnail.png</image:loc>
      <image:title>gregschool-lessons - Introduction to Partial Derivatives</image:title>
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      <image:title>gregschool-lessons - Introduction to Partial Derivatives</image:title>
      <image:caption>Figure 2: The entire blue surface is given by the function \(f(x,y)=x^2+y^2\). By letting \(y=1\), we that \(y^2=1\) and \(f(x,1)=x^2+1\) giving us a parabola shifted up one unit along the \(z\)-axis. That is how we can analytically obtain the parabola \(f(x,y)\). We can also obtain \(f(x,1)\) by passing the plane \(y=1\) (illustrated as the black plane above) through the surface \(f(x,y)\). The points at which the two surfaces (the surface \(f(x,y)\) and the plane \(y=1\)) intersect form the red parabola drawn in the image above. Image credit: By IkamusumeFan (Own work) [CC BY-SA 4.0 (https://creativecommons.org/licenses/by-sa/4.0)], via Wikimedia Commons.</image:caption>
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      <image:title>gregschool-lessons - Introduction to Partial Derivatives</image:title>
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      <image:title>gregschool-lessons - Introduction to Partial Derivatives</image:title>
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      <image:title>gregschool-lessons - Introduction to Partial Derivatives</image:title>
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      <image:title>gregschool-lessons - Introduction to Partial Derivatives</image:title>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/gregschoollessons/2017/10/29/quasars-3xbmj-geyeg</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-09</lastmod>
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      <image:title>gregschool-lessons - Quasars</image:title>
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      <image:title>gregschool-lessons - Quasars</image:title>
      <image:caption>Figure 5: A 3-d map obtained by the Sloan Digital Survey of billions of light years of our local universe. Each dot is an entire galaxy and this survey shows millions of them. As you can see from this image, on the scale of billions of light-years the galaxies of congregated into a "web"-like structure of filaments and strands known as the cosmic web. Image Credit: M. Blanton and SDSS</image:caption>
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      <image:title>gregschool-lessons - Quasars</image:title>
      <image:caption>Figure 2: "The spectrum of the quasar 3C 273. The strongest emission lines present are Balmer lines of hydrogen, as marked. In each case, the arrow is drawn from the rest wavelength to the observed wavelength of the line— shifted redward in each case by 15.8%. The other emission lines apparent in the spectrum are due to oxygen, helium, iron, and other elements. Credit: Michael A. Strauss, from data taken by the New Technology Telescope at La Silla, Chile; M. Türler et al. 2006, Astronomy and Astrophysics 451: L1– L4, http:// isdc.unige.ch/ 3c273/# emmi, http:// casswww.ucsd.edu/ archive/ public/ tutorial/ images/ 3C273z.gif Tyson, Neil deGrasse; Strauss, Michael A.; Gott, J. Richard. Welcome to the Universe: An Astrophysical Tour (p. 242). Princeton University Press. Kindle Edition."\(^{[2]}\)</image:caption>
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      <image:title>gregschool-lessons - Quasars</image:title>
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      <image:title>gregschool-lessons - Quasars</image:title>
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      <image:title>gregschool-lessons - Quasars</image:title>
      <image:caption>Figure 1: "The 200-inch (5.1 m) Hale Telescope (f/3.3) was the world's largest effective telescope for 45 years (1948-1993). It is still a workhorse of modern astronomy. It is used nightly for a wide range of astronomical studies. On average the weather allows for at least some data collection about 290 nights a year."\(^{[1]}\) Image credit: Caltech/Palomar Observatory</image:caption>
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      <image:title>gregschool-lessons - Quasars</image:title>
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      <image:title>gregschool-lessons - Quasars</image:title>
      <image:caption>Figure 4: Illustration of the various different components of a quasar.\(^{[4]}\) Image credit: Futurism.</image:caption>
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      <image:title>gregschool-lessons - Quasars</image:title>
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      <image:title>gregschool-lessons - Quasars</image:title>
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      <image:title>gregschool-lessons - Quasars</image:title>
      <image:caption>Figure 3: "This image from Hubble’s Wide Field and Planetary Camera 2 (WFPC2) is likely the best of ancient and brilliant quasar 3C 273, which resides in a giant elliptical galaxy in the constellation of Virgo (The Virgin). Its light has taken some 2.5 billion years to reach us. Despite this great distance, it is still one of the closest quasars to our home. It was the first quasar ever to be identified, and was discovered in the early 1960s by astronomer Allan Sandage. The term quasar is an abbreviation of the phrase “quasi-stellar radio source”, as they appear to be star-like on the sky. In fact, quasars are the intensely powerful centres of distant, active galaxies, powered by a huge disc of particles surrounding a supermassive black hole. As material from this disc falls inwards, some quasars — including 3C 273 — have been observed to fire off super-fast jets into the surrounding space. In this picture, one of these jets appears as a cloudy streak, measuring some 200 000 light-years in length. Quasars are capable of emitting hundreds or even thousands of times the entire energy output of our galaxy, making them some of the most luminous and energetic objects in the entire Universe. Of these very bright objects, 3C 273 is the brightest in our skies. If it was located 30 light-years from our own planet — roughly seven times the distance between Earth and Proxima Centauri, the nearest star to us after the Sun — it would still appear as bright as the Sun in the sky. WFPC2 was installed on Hubble during shuttle mission STS-125. It is the size of a small piano and was capable of seeing images in the visible, near-ultraviolet, and near-infrared parts of the spectrum."\(^{[3]}\) Image Credit: ESA/Hubble [CC BY 4.0 (http://creativecommons.org/licenses/by/4.0)], via Wikimedia Commons</image:caption>
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  </url>
  <url>
    <loc>https://www.gregschool.org/gregschoollessons/2017/10/22/volume-of-an-oblate-spheroid-rl852-8yer8</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-10</lastmod>
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      <image:title>gregschool-lessons - Volume of an Oblate Spheroid</image:title>
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      <image:title>gregschool-lessons - Volume of an Oblate Spheroid</image:title>
      <image:caption>Figure 2: A cylindrical shell is obtained by revolving the rectangle \(f(x_i)Δx\) about the \(y\)-axis. Doing this for all \(n\) rectangles, we get an \(n\) number of shells. By summing the volumes of these \(n\) number of cylindrical shells, we can obtain an estimate for total volume enclosed inside of the paraboloid obtained by rotating the quarter-ellipse (the one in the upper-right quadrant) about the \(x\)-axis.</image:caption>
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      <image:title>gregschool-lessons - Volume of an Oblate Spheroid</image:title>
      <image:caption>Figure 3: If \(a\) and \(c\) represents the semi-major and semi-minor axes of an ellipse, respectively, and if \(a=3\) and \(c=2\) then by rotating such an ellipse about an axis we can obtain an oblate spheroid.</image:caption>
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      <image:title>gregschool-lessons - Volume of an Oblate Spheroid</image:title>
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      <image:title>gregschool-lessons - Volume of an Oblate Spheroid</image:title>
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      <image:title>gregschool-lessons - Volume of an Oblate Spheroid</image:title>
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      <image:title>gregschool-lessons - Volume of an Oblate Spheroid</image:title>
      <image:caption>Figure 1: Graph of the ellipse \(\frac{x^2}{9}+\frac{y^2}{4}=1\) centered at the origin of the \(xy\)-plane. Also, I have drawn the \(i^{th}\) rectangle underneath the quarter-ellipse within the first quadrant. There are an \(n\) number of such rectangles underneath this quarter-ellipse along the interval \(Δx=3-0\).  </image:caption>
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      <image:title>gregschool-lessons - Volume of an Oblate Spheroid</image:title>
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      <image:title>gregschool-lessons - Volume of an Oblate Spheroid</image:title>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/gregschoollessons/2017/8/21/our-future-as-cyborgs-lfz6p</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2019-03-23</lastmod>
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      <image:title>gregschool-lessons - Our Future as Cyborgs</image:title>
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      <image:title>gregschool-lessons - Our Future as Cyborgs</image:title>
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      <image:title>gregschool-lessons - Our Future as Cyborgs</image:title>
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      <image:title>gregschool-lessons - Our Future as Cyborgs</image:title>
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      <image:title>gregschool-lessons - Our Future as Cyborgs</image:title>
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      <image:title>gregschool-lessons - Our Future as Cyborgs</image:title>
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      <image:title>gregschool-lessons - Our Future as Cyborgs</image:title>
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      <image:title>gregschool-lessons - Our Future as Cyborgs</image:title>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/gregschoollessons/2017/10/27/gravitational-force-exerted-by-a-sphere-lm293-p3sph</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-09</lastmod>
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      <image:title>gregschool-lessons - Gravitational Force Exerted by a Disk</image:title>
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      <image:title>gregschool-lessons - Gravitational Force Exerted by a Disk</image:title>
      <image:caption>Figure 2: A disk of mass \(M=\int{m_{ring}}\) exerts a gravitational force on a particle of mass \(m\) a distance \(h\) away from the center of the disk along the \(x\)-axis. By summing the gravitational force exerted on \(m\) by each ring of radius \(r\) from \(r=0\) to \(r=R\), we can find the total gravitational force exerted on \(m\) by the entire disk.</image:caption>
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      <image:title>gregschool-lessons - Gravitational Force Exerted by a Disk</image:title>
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      <image:title>gregschool-lessons - Gravitational Force Exerted by a Disk</image:title>
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      <image:title>gregschool-lessons - Gravitational Force Exerted by a Disk</image:title>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a0376f9e4966b6eaa5b6a98/1509567101995/ring1.jpg</image:loc>
      <image:title>gregschool-lessons - Gravitational Force Exerted by a Disk</image:title>
      <image:caption>Figure 1: A ring of mass \(M=\int{dm}\) exerts a gravitational force on a particle of mass \(m\) a horizontal distance \(h\) away from the center of the ring. The vertical component of force \(dF_y\) for every mass element \(dm\) in the ring is canceled out by the vertical component of force \(dF'_y\) for another mass element \(dm'\) located on the opposite side of the ring.</image:caption>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/gregschoollessons/2017/9/21/shkadov-thruster-ljar4-xp8c5</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-11</lastmod>
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      <image:title>gregschool-lessons - Shkadov thruster</image:title>
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      <image:title>gregschool-lessons - Shkadov thruster</image:title>
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      <image:title>gregschool-lessons - Shkadov thruster</image:title>
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      <image:title>gregschool-lessons - Shkadov thruster</image:title>
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      <image:title>gregschool-lessons - Shkadov thruster</image:title>
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      <image:title>gregschool-lessons - Shkadov thruster</image:title>
      <image:caption>Figure 2: Artist's depiction of a Shkadov thruster. Credit: https://www.artstation.com/artofsoulburn</image:caption>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a037716f9619acb4fed3c8a/1509497981406/Shkadov_diagram.jpg</image:loc>
      <image:title>gregschool-lessons - Shkadov thruster</image:title>
      <image:caption>Figure 1: An arc mirror (dark orange arc) subtended by an angle \(2\phi\) reflects a star's radiation back towards itself. Photons collide against the portion of the star's surface which is subtended by the angle \(2\phi\). These collisions result in a net force \(\vec{F}\) exerted on the star causing the entire star to move in the direction of the arrow. The star's gravity pulls everything else in the star system along with it.</image:caption>
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      <image:title>gregschool-lessons - Shkadov thruster</image:title>
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  </url>
  <url>
    <loc>https://www.gregschool.org/gregschoollessons/2017/10/30/derivation-of-snells-law-a8sne-a8e5w</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-12</lastmod>
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      <image:title>gregschool-lessons - Derivation of Snell's Law</image:title>
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      <image:title>gregschool-lessons - Derivation of Snell's Law</image:title>
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      <image:title>gregschool-lessons - Derivation of Snell's Law</image:title>
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      <image:title>gregschool-lessons - Derivation of Snell's Law</image:title>
      <image:caption>Figure 1: A light ray traveling along the line \(QO\) comes into contact with a surface at an \(θ_i\) (where \(θ_i\) is measured relative to the line perpendicular to the surface). Once this light ray comes into contact with this surface, it is reflected at an angle \(θ_r\) (\(θ_r\) is also measured relative to the perpendicular). According to the law of reflection, \(θ_i=θ_r\). Image credit: Download for free at http://cnx.org/contents/60b4727b-829e-4ea7-9238-9140b6a1b20c@4.</image:caption>
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      <image:title>gregschool-lessons - Derivation of Snell's Law</image:title>
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      <image:title>gregschool-lessons - Derivation of Snell's Law</image:title>
      <image:caption>Figure 2: As a light ray travels along the line \(QO\) through medium 1 and comes into contact with the interface between medium 1 and medium 2, it gets refracted—meaning, it passes through medium 2. Image credit: By Smedlib (Own work) [CC BY-SA 4.0 (https://creativecommons.org/licenses/by-sa/4.0)], via Wikimedia Commons</image:caption>
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      <image:title>gregschool-lessons - Derivation of Snell's Law</image:title>
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      <image:title>gregschool-lessons - Derivation of Snell's Law</image:title>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/gregschoollessons/2017/10/14/optimizatio-z7f59-3jc23</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-08</lastmod>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a03783153450ac45add7552/1509493612642/facebook+img+thumbnail.jpg</image:loc>
      <image:title>gregschool-lessons - Optimization Problem</image:title>
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      <image:title>gregschool-lessons - Optimization Problem</image:title>
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      <image:title>gregschool-lessons - Optimization Problem</image:title>
      <image:caption>Figure 1: A graph of the circle \(x^2+y^2=4\) which is centered at the origin of the \(x\)-axis. If \((x,y)\) represents any point on the circle, if \(P\) is a point fixed at the coordinate point \((4,0)\), and if \(d\) represents the distance between those two points then, by using only calculus, we can find the point \((x,y)\) on the circle associated with the minimum distance \(d\).</image:caption>
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      <image:title>gregschool-lessons - Optimization Problem</image:title>
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    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a03783153450ac45add755b/1509492607607/Calculus+thumbnail.png</image:loc>
      <image:title>gregschool-lessons - Optimization Problem</image:title>
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      <image:title>gregschool-lessons - Optimization Problem</image:title>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a03783153450ac45add7558/1509492674642/email+img+thumbnail.jpg</image:loc>
      <image:title>gregschool-lessons - Optimization Problem</image:title>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/gregschoollessons/2017/10/14/maximizing-the-area-of-a-rectangle-stk62-kh39r</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-08</lastmod>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a03784ac830253dadebc1ad/1509490767138/Calculus+thumbnail.png</image:loc>
      <image:title>gregschool-lessons - Maximizing the Area of a Rectangle</image:title>
    </image:image>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a03784ac830253dadebc1a3/1509491428650/facebook+img+thumbnail.jpg</image:loc>
      <image:title>gregschool-lessons - Maximizing the Area of a Rectangle</image:title>
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      <image:title>gregschool-lessons - Maximizing the Area of a Rectangle</image:title>
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      <image:title>gregschool-lessons - Maximizing the Area of a Rectangle</image:title>
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    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a03784ac830253dadebc1af/1509297168705/Optimization+Problem+1.jpg</image:loc>
      <image:title>gregschool-lessons - Maximizing the Area of a Rectangle</image:title>
      <image:caption>Figure 1: Given any rectangle \(xy\) where the perimeter \(2x+2y\) is the constant, we can use calculus to find that particular rectangle \(xy\) with the maximum area \(A\). The solution to this problem has practical applications. For example, suppose that someone had only 30 meters of fencing to enclose their backyard and they wanted to know what fencing layout would maximize the size and total area of their backyard.</image:caption>
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      <image:title>gregschool-lessons - Maximizing the Area of a Rectangle</image:title>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a03784ac830253dadebc1a1/1509490953440/share+img.jpg</image:loc>
      <image:title>gregschool-lessons - Maximizing the Area of a Rectangle</image:title>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/gregschoollessons/2017/6/24/finding-the-minima-and-maxima-of-a-function-9g3gp-jzmsa</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-08</lastmod>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a037854c830253dadebc51b/1509495139379/Calculus+thumbnail.jpg</image:loc>
      <image:title>gregschool-lessons - Finding the Minima and Maxima of a Function</image:title>
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    <image:image>
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      <image:title>gregschool-lessons - Finding the Minima and Maxima of a Function</image:title>
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    <image:image>
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      <image:title>gregschool-lessons - Finding the Minima and Maxima of a Function</image:title>
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      <image:title>gregschool-lessons - Finding the Minima and Maxima of a Function</image:title>
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    <image:image>
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      <image:title>gregschool-lessons - Finding the Minima and Maxima of a Function</image:title>
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      <image:title>gregschool-lessons - Finding the Minima and Maxima of a Function</image:title>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/gregschoollessons/2017/9/12/colonizing-the-kuiper-belt-and-oort-cloud-g53ff-66yzf</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-12-12</lastmod>
    <image:image>
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      <image:title>gregschool-lessons - Colonizing the Kuiper Belt and Oort Cloud</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a03785f8165f5ed71a9ead9/1507689697151/Ancient_Mars3_02.jpg</image:loc>
      <image:title>gregschool-lessons - Colonizing the Kuiper Belt and Oort Cloud</image:title>
      <image:caption>Artist's depiction of Fesenkov Crater on Mars filled with liquid water.</image:caption>
    </image:image>
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      <image:title>gregschool-lessons - Colonizing the Kuiper Belt and Oort Cloud</image:title>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a03785f8165f5ed71a9eae1/1507689697158/OortCloud_P-sys%28PNG-fin%291.png</image:loc>
      <image:title>gregschool-lessons - Colonizing the Kuiper Belt and Oort Cloud</image:title>
      <image:caption>Another size comparison of the solar system to the Oort Cloud.</image:caption>
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      <image:title>gregschool-lessons - Colonizing the Kuiper Belt and Oort Cloud</image:title>
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      <image:title>gregschool-lessons - Colonizing the Kuiper Belt and Oort Cloud</image:title>
      <image:caption />
    </image:image>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/5a03785f8165f5ed71a9eadb/5a03785f8165f5ed71a9eade/1507689697156/uranus-gas-zoom.jpg</image:loc>
      <image:title>gregschool-lessons - Colonizing the Kuiper Belt and Oort Cloud</image:title>
      <image:caption>Artist’s depiction of Neptune’s (above image) and Uranus’s (below image) atmosphere being harvested for resources such as nitrogen.</image:caption>
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      <image:title>gregschool-lessons - Colonizing the Kuiper Belt and Oort Cloud</image:title>
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    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a03785f8165f5ed71a9ead1/1509746098359/google+img+thumbnail.jpg</image:loc>
      <image:title>gregschool-lessons - Colonizing the Kuiper Belt and Oort Cloud</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a03785f8165f5ed71a9ead3/1509746098361/email+img+thumbnail.jpg</image:loc>
      <image:title>gregschool-lessons - Colonizing the Kuiper Belt and Oort Cloud</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a03785f8165f5ed71a9ead7/1507689697150/Kuiper_oort.jpg</image:loc>
      <image:title>gregschool-lessons - Colonizing the Kuiper Belt and Oort Cloud</image:title>
      <image:caption>A size comparison of the Kuiper belt and outer solar system to the Oort Cloud.</image:caption>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/gregschoollessons/2017/8/13/why-colonize-the-universe-z48ay-f5rbb</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-08</lastmod>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a03786bc830253dadebcb42/1507058438785/51i54HqlYHL._SY344_BO1%2C204%2C203%2C200_.jpg</image:loc>
      <image:title>gregschool-lessons - Why Colonize the Universe?</image:title>
      <image:caption>In Carl Sagan's book Pale Blue Dot, he argued that humans evolved a love for exploration as an essential part of our survival as a species. It was this evolutionary trait which compelled our hunter-gather ancestors to leave their home—Africa—when times were getting rough and to meander across the planet. As planetary catastrophes become increasingly likely as time rolls by, Sagan argues that this same "survival strategy" will perhaps compell humanity to colonize the solar system, and beyond.</image:caption>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a03786bc830253dadebcb40/1507688339362/space+travela+nd+colonization+thumbnail.jpg</image:loc>
      <image:title>gregschool-lessons - Why Colonize the Universe?</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a03786bc830253dadebcb44/1507059034215/factoriesins.jpg</image:loc>
      <image:title>gregschool-lessons - Why Colonize the Universe?</image:title>
      <image:caption>An O'Neil cylinder is a type of megastructure and artificial space habitat which was first proposed by the physicist Gerard O'Neil in 1976. An O'Neil cylinder would consist of two immense, rotating, cylindrical habitats (illustrated above) which would spin at a angular velocity that generated centrifugal forces along the interior surfaces of the cylinders which would emulate Earth-gravity. Each cylindrical habitat would be 5 miles in diameter and 20 miles long.</image:caption>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/gregschoollessons/2017/10/6/calculating-the-arc-length-of-a-curve-hk54b-l6tsz</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-08</lastmod>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a03787fe2c483a1fc725184/1507687678074/calculus+thumbnail.jpg</image:loc>
      <image:title>gregschool-lessons - Calculating the Arc Length of a Curve</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a03787fe2c483a1fc725186/1507341957781/arclengthimg1.jpg</image:loc>
      <image:title>gregschool-lessons - Calculating the Arc Length of a Curve</image:title>
      <image:caption>Figure 1: The curve \(P_1P_n\) split up into an \(n\) number of chords \(P_iP_{i+1}\) where \(i=1,...,n\). By taking the sum of the lengths of each chord (represented by \(\sum_{i=1}^nL(P_iP_{i+1})\)) and then taking the limit as \(n→∞\), we obtain the exact arc length \(s\) of the entire curve.</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a03787fe2c483a1fc725188/1507343004584/arclengthimg2.jpg</image:loc>
      <image:title>gregschool-lessons - Calculating the Arc Length of a Curve</image:title>
      <image:caption>Figure 2: A close up view of the \(i^{th}\) chord subdividing the curve \(P_1P_n\). Since the chord \(P_iP_{i+1}\) forms a right triangle, by using the Pythagorean theorem we can express \(L(P_iP_{i+1})\) as \(\sqrt{(Δx_i)^2+(Δy_i)^2}\).</image:caption>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/gregschoollessons/2017/9/19/the-kardeshev-scale-ge4gb-3zfyp</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-08</lastmod>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a037896085229fe4473034d/1507683863314/bubble-universes-computer-illustration-of-multiple-bubble-universes-G4C3H0.jpg</image:loc>
      <image:title>gregschool-lessons - The Kardeshev Scale</image:title>
      <image:caption>Artist's depiction of the multi-verse.</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a037896085229fe44730343/1507687169817/space+travela+nd+colonization+thumbnail.jpg</image:loc>
      <image:title>gregschool-lessons - The Kardeshev Scale</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a037896085229fe44730345/1507057461266/1024px-Consommations_%C3%A9nerg%C3%A9tiques_des_trois_types_de_l%27%C3%A9chelle_de_Kardashev.svg.png</image:loc>
      <image:title>gregschool-lessons - The Kardeshev Scale</image:title>
      <image:caption>The Kardeshev scale ranks how advanced a technological civilization is based upon their total power consumption. A Type I civilization is capable of harnessing all of their home plant's power of \(~10^{16}W\); a Type II civilization has harnessed the power of their star ( \(~10^{26}W\)); and a Type III civilization has harnessed the power output of their entire galaxy ( \(~10^{36}W\)). There are even Type IV and Type V civilization which go beyond Kardeshev's original scale.</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/5a037896085229fe44730347/5a037896085229fe4473034a/1507750720730/17202572._SX540_.jpg</image:loc>
      <image:title>gregschool-lessons - The Kardeshev Scale</image:title>
      <image:caption>Artist's depiction of a ring world. Credit: http://richardfrazer.com/</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/5a037896085229fe44730347/5a037896085229fe44730348/1507676111750/dyson_sphere_second_1024.jpg</image:loc>
      <image:title>gregschool-lessons - The Kardeshev Scale</image:title>
      <image:caption>Dyson sphere. Credit: capnhack.com</image:caption>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/gregschoollessons/2017/9/30/solving-problems-using-line-integrals-z8s7t-e2kk8</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-08</lastmod>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a0378a00d9297d83e408b34/1507491891563/156px-Circular_cylinder_rh.jpg</image:loc>
      <image:title>gregschool-lessons - Solving Problems using Line Integrals</image:title>
      <image:caption>Figure 1: A cylinder with height \(h=2\) and radius \(r=1\). The "top" and "bottom" pieces of the cylinder are removed.</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a0378a00d9297d83e408b36/1507147436235/Untitled.jpg</image:loc>
      <image:title>gregschool-lessons - Solving Problems using Line Integrals</image:title>
      <image:caption>Figure 2: A proton \(P_2\) seperated by an initil seperation distance \(r_0\) from a station proton \(P_1\) moves along an arbitrary path until it reaches a seperation distance of \(r\). According to Column's law, the proton \(P_1\) will exert an electric force and, hence, also do work on the proton \(P_2\) as it moves from \(r_0\) to \(r\). The electric force forms a vector field and by calculuating the line integral along \(P_2\)'s path, we can calculate the amount of work done on \(P_2\).</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a0378a00d9297d83e408b32/1507502227235/sdfsdfdsdfdfdf+october+8.jpg</image:loc>
      <image:title>gregschool-lessons - Solving Problems using Line Integrals</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a0378a00d9297d83e408b38/1506906635307/main-qimg-ef54da6034b7e89fb771a40923f089ca.gif</image:loc>
      <image:title>gregschool-lessons - Solving Problems using Line Integrals</image:title>
      <image:caption>Figure 3: A mass \(m\) is attached to the end of a rope of length \(L\). The mass falls and travels a distance \(s\) with a total angular displacement of \(θ\).</image:caption>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/gregschoollessons/2017/9/27/introduction-to-line-integrals-bywel-5asgd</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-08</lastmod>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a0378aa085229fe447309d4/1507433707547/fhdhfdg.jpg</image:loc>
      <image:title>gregschool-lessons - Introduction to Line Integrals</image:title>
      <image:caption>Figure 2: By the Pythagorean theorem, each infinitesimal arc length \(ds\) can be represented in terms of \(x\) and \(y\) as \(\sqrt{x+2+y^2}\).</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a0378aa085229fe447309d0/1510175532388/sdf.jpg</image:loc>
      <image:title>gregschool-lessons - Introduction to Line Integrals</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a0378aa085229fe447309d2/1507432031391/VIBrO.jpg</image:loc>
      <image:title>gregschool-lessons - Introduction to Line Integrals</image:title>
      <image:caption>Figure 1: The width and height of each blue rectangle is given by the arc length \(ds\) and the function \(f(x,y)\), respectively. The line integral, \(\int_Cf(x,y)ds\), represents the infinite sum of the area of each blue rectangle along the curve \(C\) (the purple line on the \(xy\)-plane). This image is a derivative work. Original image: https://www.wikihow.com/User:Atheia</image:caption>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/gregschoollessons/2017/10/6/calculating-the-volume-of-a-sphere-e6jde-bs7ml-nl5p5</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-11</lastmod>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a0378b824a694f5e24f19d6/1507412420221/moment-of-inertia-of-sphere.jpg</image:loc>
      <image:title>gregschool-lessons - Calculating the Volume of a Sphere</image:title>
      <image:caption>Figure 4: By taking the infinite sum of the volumes, \(π(f(x))^2dx\), of every cylinder from \(x=0\) to \(x=R\), we can obtain the volume of half of the sphere depicted above. By multiplying our answer by two, we can obtain the volume of the whole sphere. Image credit: https://www.miniphysics.com/uy1-calculation-of-moment-of-inertia-of-solid-sphere.html</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a0378b824a694f5e24f19d0/1507412420207/320px-Rotationskoerper_animation.gif</image:loc>
      <image:title>gregschool-lessons - Calculating the Volume of a Sphere</image:title>
      <image:caption>Figure 1: The "vase" shaped surface is obtained by revolving a curve about the vertical axis. The region of space that the surface encloses is called a solid of revolution.</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a0378b824a694f5e24f19d4/1507412420216/s9NuK.jpg</image:loc>
      <image:title>gregschool-lessons - Calculating the Volume of a Sphere</image:title>
      <image:caption>Figure 3: By rotating the \(i^{th}\) rectangle about the \(x\)-axis, the cylinder depicted above is obtained. By doing this for each rectangle, an \(n\) number of cylinders are obtained. All of these cylinders fit inside of a hemisphere of radius \(r\) and the sum of the volumes of all of those cylinders approximate the volume of the hemisphere.</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a0378b824a694f5e24f19ce/1510175551473/sdf.jpg</image:loc>
      <image:title>gregschool-lessons - Calculating the Volume of a Sphere</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a0378b824a694f5e24f19d2/1507412420213/volumeofsphereimg1.jpg</image:loc>
      <image:title>gregschool-lessons - Calculating the Volume of a Sphere</image:title>
      <image:caption>Figure 2: A graph of the quarter circle \(x^2+y^2=r^2\) for \(x≥0\) and \(y≥0\). An \(n\) number of rectangles, \(f(x_i\)Δx\), are drawn underneath the curve.</image:caption>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/gregschoollessons/2017/8/16/maclaurin-polynomial-and-series-9cll7-my4k9</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-08</lastmod>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a0378db9140b70c95b2253f/1504563483921/Exp_series.gif</image:loc>
      <image:title>gregschool-lessons - Maclaurin/Taylor Polynomials and Series</image:title>
      <image:caption>Figure 1. Maclaurin polynomials of different order \(n\) (red curves) approximating the function \(e^x\) (blue curve).</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a0378db9140b70c95b2253d/1507581887299/Untitled.jpg</image:loc>
      <image:title>gregschool-lessons - Maclaurin/Taylor Polynomials and Series</image:title>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/gregschoollessons/2017/8/29/introduction-to-integrals-xl5rn-y4ls9</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-08</lastmod>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a0378eb9140b70c95b2292a/1504566939599/dfgd.png</image:loc>
      <image:title>gregschool-lessons - Introduction to Integrals</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a0378eb9140b70c95b22926/1510176997141/Untitled.jpg</image:loc>
      <image:title>gregschool-lessons - Introduction to Integrals</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a0378eb9140b70c95b22930/1504567134996/Riemann_Integration_and_Darboux_Upper_Sums.gif</image:loc>
      <image:title>gregschool-lessons - Introduction to Integrals</image:title>
      <image:caption>Figure 2. The approximate area, \(\sum_{i=1}^nf(x_n)Δx\), underneath the curve \(y=x^2\) becomes closer and closer to the exact area underneath the curve as the number \(n\) of terms increases.</image:caption>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/gregschoollessons/2017/6/28/8fldcv2rgvjvjwb42w67qh0ude4ii0-3yepp-2p2s7</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-08</lastmod>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a0378f50d9297d83e40a2d1/1507670521347/space+travela+nd+colonization+thumbnail.jpg</image:loc>
      <image:title>gregschool-lessons - Alcubierre Warp Drive</image:title>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/gregschoollessons/2017/6/28/terraforming-mars-gz3x8-s9hg4</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2019-03-19</lastmod>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a03792b0d9297d83e40af22/1502413444230/</image:loc>
      <image:title>gregschool-lessons - Terraforming and Colonizing Mars</image:title>
      <image:caption>"This shot follows the cabin of a space elevator descending on a cable towards the northern parts of the Terra Cimmeria highlands on Mars. A large settlement, hinted as glowing lights in the dark, can be seen far below on the ground. One of Mars' two moons - Phobos - is seen above the cabin to the left of the cable in the beginning of the shot." This image was produced by Erik Wernquist.</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a03792b0d9297d83e40af28/1498701189016/</image:loc>
      <image:title>gregschool-lessons - Terraforming and Colonizing Mars</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a03792b0d9297d83e40af20/1498701139592/</image:loc>
      <image:title>gregschool-lessons - Terraforming and Colonizing Mars</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a03792b0d9297d83e40af1e/1502315090185/ares2.jpg</image:loc>
      <image:title>gregschool-lessons - Terraforming and Colonizing Mars</image:title>
      <image:caption>Artist's depiction of the Ares spaceship from Kim Stanley Robinson's novel, Red Mars.</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/5c90777eee6eb06073b7a7f1/5c90777e15fcc09c62fa950d/1552971654919/marsssssssssssssssssssssss.jpg</image:loc>
      <image:title>gregschool-lessons - Terraforming and Colonizing Mars</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/5c907dfa9140b7ad40265fd1/5c907eb4ee6eb06073b7dca0/1552973573193/iceteroiddd.jpg</image:loc>
      <image:title>gregschool-lessons - Terraforming and Colonizing Mars - Absolute Zero</image:title>
      <image:caption>Artist’s depiction of iceteroids located within a nebula. Image Credit: https://store.steampowered.com/news/?appids=310380&amp;enddate=1498892400&amp;appgroupname=Fractured+Space</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/5c907d0ae79c709a0f3604d4/5c907d0a9b747a6c2b91b21c/1552973117109/dn10573-1_800%5B1%5D.jpg</image:loc>
      <image:title>gregschool-lessons - Terraforming and Colonizing Mars</image:title>
      <image:caption>An orbiting array of reflective balloons focuses sunlight onto the surface of Mars, providing extra heat and solar power for human colonists (Illustration: Rigel Woida)</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/5c907d0ae79c709a0f3604d4/5c907d0c0852294993ed240b/1552973137671/dn10573-2_700%5B1%5D.jpg</image:loc>
      <image:title>gregschool-lessons - Terraforming and Colonizing Mars</image:title>
      <image:caption>The lake of water ice seen here could be melted to provide liquid water for future Mars astronauts (Image: ESA/DLR/F U Berlin/G Neukum)</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a03792b0d9297d83e40af1c/1507664835657/space+travela+nd+colonization+thumbnail.jpg</image:loc>
      <image:title>gregschool-lessons - Terraforming and Colonizing Mars</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5c9079d90852294993ed09ab/1552972255054/Mars-VR-570x300%5B1%5D.jpg</image:loc>
      <image:title>gregschool-lessons - Terraforming and Colonizing Mars</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a03792b0d9297d83e40af26/1502314679613/olympus.jpg</image:loc>
      <image:title>gregschool-lessons - Terraforming and Colonizing Mars</image:title>
      <image:caption>Poster by SpaceX</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5c907b81971a186e678a4034/1552972687082/Cpw8t4nVUAA7e5L%5B1%5D.jpg</image:loc>
      <image:title>gregschool-lessons - Terraforming and Colonizing Mars</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a03792b0d9297d83e40af24/1502431153897/</image:loc>
      <image:title>gregschool-lessons - Terraforming and Colonizing Mars</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5c907c79ec212d7ca9d3fb33/1552972940780/dis03_fig1_hires_0%5B1%5D.jpg</image:loc>
      <image:title>gregschool-lessons - Terraforming and Colonizing Mars</image:title>
      <image:caption>Mars’ south polar ice cap, as seen in April of 2000 by the Mars Odyssey mission. Credit: NASA/JPL/MSSS</image:caption>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/gregschoollessons/2017/5/14/introduction-to-special-relativity-d23j8-p3zt4</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-10</lastmod>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a05c2bee2c48388cba1d71e/1510326979408/Figure_29_02_05a%5B1%5D.jpg</image:loc>
      <image:title>gregschool-lessons - Introduction to Special Relativity</image:title>
      <image:caption>Figure 1: A clock onboard a spacecraft or plane circumnavigating the Earth will tick more slowly than a clock on the Earth's surface. All physical processes run more slowly at very high altitudes above the Earth's surface. This is even true if the relative velocity between both objects is zero; according to Einstein's general theory of relativity, the Earth's mass warps time in such a way where the flow of time (how rapidly or how slowly the clock ticks) varies with altitude above the Earth's surface. This is a mindboggling prediction!</image:caption>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/gregschoollessons/2017/5/14/8c5knwf9nztiio7uwnvvotz1pj86ht-thkb7-c33w6</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-10</lastmod>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a05d8d1e2c483f86324d3c0/1510332630437/time+dil.jpg</image:loc>
      <image:title>gregschool-lessons - Time Dilation</image:title>
      <image:caption>Figure 1: Right at the moment the train is passing by the observer standing at the train station, both observers clocks are synchronized; in other words, right at this moment, \(t=t'=0\). Also, right at this moment, a light source \(S'\) emits light in a direction towards a mirror (colored pink in image above) attached to the top of the train. The light beam eventually reaches the mirror and is reflected back towards \(S'\).</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a05cf789140b7ac4ec648dd/1510333018414/480px-Time_dilation.svg%5B1%5D.png</image:loc>
      <image:title>gregschool-lessons - Time Dilation</image:title>
      <image:caption>Figure 2: Using Equation (1), we can calculate the Lorenz factor for various different values of relative speed to obtain the graph above. As you can see, when the relative velocity between two reference frames is greater than 90% the speed of light, the effects of time dilation become enormous. Image by Zayani (Own work) [CC BY-SA 3.0 (https://creativecommons.org/licenses/by-sa/3.0) or GFDL (http://www.gnu.org/copyleft/fdl.html)], via Wikimedia Commons</image:caption>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/gregschoollessons/2017/5/15/particle-in-one-dimensional-box-dwfnl-dex28</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2019-03-21</lastmod>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a0379520d9297d83e40bb31/1495487069613/kjkjnj.png</image:loc>
      <image:title>gregschool-lessons - Time-Independant Schrodinger Equation: Free Particle and Particle in One-Dimensional Box</image:title>
      <image:caption>Figure 1 (click to expand): Illustration of a free particle moving in a "one-dimensional box" which is trapped inside of an infinite potential well.</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a0379520d9297d83e40bb33/1495562943423/sch.png</image:loc>
      <image:title>gregschool-lessons - Time-Independant Schrodinger Equation: Free Particle and Particle in One-Dimensional Box</image:title>
      <image:caption>Figure 2 (click to expand): The probability amplitude of measuring the particle at a position \(x\) in the presence of a potential \(V_0\) decreases exponentially with increasing \(V_0\).</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a0379520d9297d83e40bb37/1495487701759/</image:loc>
      <image:title>gregschool-lessons - Time-Independant Schrodinger Equation: Free Particle and Particle in One-Dimensional Box</image:title>
      <image:caption>Figure 4: Illustration shows the allowed energy levels of a particle trapped inside of a one-dimensional box.</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a0379520d9297d83e40bb2f/1495485871466/</image:loc>
      <image:title>gregschool-lessons - Time-Independant Schrodinger Equation: Free Particle and Particle in One-Dimensional Box</image:title>
      <image:caption>"A wave function that satisfies the nonrelativistic Schrödinger equation with V = 0. In other words, this corresponds to a particle traveling freely through empty space. The real part of the wave function is plotted here."\(^{[1]}\)</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a0379520d9297d83e40bb35/1494831797145/</image:loc>
      <image:title>gregschool-lessons - Time-Independant Schrodinger Equation: Free Particle and Particle in One-Dimensional Box</image:title>
      <image:caption>Figure 3 (click to expand): Illustration of a free particle moving in a one-dimensional box which is "pinned down" by a finite well. The probability amplitude of finding the particle outside of the box decreases exponentially as a function of distance.</image:caption>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/gregschoollessons/2017/8/13/nuclear-fusion-engines-g9fdd-hjd78</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-09</lastmod>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a03795d085229fe447339b3/1507665154586/space+travela+nd+colonization+thumbnail.jpg</image:loc>
      <image:title>gregschool-lessons - Nuclear Fusion Engines</image:title>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/gregschoollessons/2017/8/29/finding-the-integral-of-kxm-lbzkf-wtznt</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-08</lastmod>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a037965e2c483a1fc729396/1507419408151/author+date.jpg</image:loc>
      <image:title>gregschool-lessons - Finding the integral of \(kx^m\)</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a037965e2c483a1fc729398/1507420992695/areaoftriangle.jpg</image:loc>
      <image:title>gregschool-lessons - Finding the integral of \(kx^m\)</image:title>
      <image:caption>Figure 1: The area underneath the function \(f(x)=2x\) is simply just the area of a triangle. The base of the triangle is \(x\) and its height is \(f(x)=2x\). Using the formula for the area of a triangle, we find that the area underneath \(f(x)=2x\) is \(x^2\).</image:caption>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/gregschoollessons/2017/8/30/capacitance-32sgr-ssdas</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-10</lastmod>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a03798f71c10b1e516768b9/1507602491385/electromagnetism+thumbnaillllll+imageeee.jpg</image:loc>
      <image:title>gregschool-lessons - Capacitance</image:title>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/gregschoollessons/2017/8/30/5g8xs8bx2yk4rez4xp70hkmry35965-k5dj3-6lkj3</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-08</lastmod>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a0379ab24a694f5e24f5ce3/1507603176920/electromagnetism+thumbnaillllll+imageeee.jpg</image:loc>
      <image:title>gregschool-lessons - Calculating the amount of Electric Potential Energy Stored in a Capacitor</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a0379ab24a694f5e24f5ce5/1504719624283/kkk.png</image:loc>
      <image:title>gregschool-lessons - Calculating the amount of Electric Potential Energy Stored in a Capacitor</image:title>
      <image:caption>Figure 1</image:caption>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/gregschoollessons/2017/5/23/math-interlude-cddln-phcd6</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-11</lastmod>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a0379bd71c10b1e5167755b/1507610424966/electromagnetism+thumbnaillllll+imageeee.jpg</image:loc>
      <image:title>gregschool-lessons - Quantum Mechanics: Math Interlude</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a065ff941920291503726c2/1510367229774/200px-Complex_Impedance.svg%5B1%5D.jpg</image:loc>
      <image:title>gregschool-lessons - Quantum Mechanics: Math Interlude</image:title>
      <image:caption>Figure 1: Any complex number \(z\) can be represented in either Cartesian coordinates as \(x+iy\) or in polar coordinates as \(re^{iθ}\).</image:caption>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/gregschoollessons/2017/5/14/quantum-dynamics-2nhll-s9x7c</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-08</lastmod>
  </url>
  <url>
    <loc>https://www.gregschool.org/gregschoollessons/2017/5/23/the-eigenvalues-of-any-observable-hatl-must-be-real-3jrk4-gja8k</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-09</lastmod>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a0379dd9140b70c95b26f1a/1507610471341/electromagnetism+thumbnaillllll+imageeee.jpg</image:loc>
      <image:title>gregschool-lessons - The Eigenvalues of any Observable \(\hat{L}\) must be Real</image:title>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/gregschoollessons/2017/5/23/pauli-matrices-wf87n-fgty6</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-08</lastmod>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a0379e50d9297d83e40e669/1507610581346/electromagnetism+thumbnaillllll+imageeee.jpg</image:loc>
      <image:title>gregschool-lessons - Pauli Matrices</image:title>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/gregschoollessons/2017/8/10/einstein-equivalence-principle-8j2w9-76xjn</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-08</lastmod>
  </url>
  <url>
    <loc>https://www.gregschool.org/gregschoollessons/2017/5/23/fundamental-principles-and-postulates-of-quantum-mechanics-5hrka-4pedm</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-08</lastmod>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a0379f6419202d77c15f7a2/1507610679168/electromagnetism+thumbnaillllll+imageeee.jpg</image:loc>
      <image:title>gregschool-lessons - Fundamental Principles and Postulates of Quantum Mechanics</image:title>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/gregschoollessons/2017/5/23/measuring-the-spin-of-an-electron-e5rzd-gmtdl</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-08</lastmod>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a037a10419202d77c15fe4e/1495565239455/</image:loc>
      <image:title>gregschool-lessons - Measuring the Spin of an Electron</image:title>
      <image:caption>Figure 1</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a037a10419202d77c15fe51/1507610719385/electromagnetism+thumbnaillllll+imageeee.jpg</image:loc>
      <image:title>gregschool-lessons - Measuring the Spin of an Electron</image:title>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/gregschoollessons/2017/5/14/solving-the-frw-equation-for-the-scaling-factor-in-different-scenarios-hdsrg-6tdyy</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-08</lastmod>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a037a3a0d9297d83e40fabd/1509980764068/AT_7e_Figure_27_01%5B2%5D.jpg</image:loc>
      <image:title>gregschool-lessons - Solving the FRW Equation for the Scaling Factor in different scenarios</image:title>
      <image:caption>Figure 1: As you can see from the graph above, for the first roughly 10,000 years most of the energy density in the universe was due to the presence of radiation. During the time interval from when the universe was 10,000 years old to when it was several billion years old, the energy density of the universe was dominated by matter. In our present epoch, the energy density of the universe is dominated by dark energy (or vacuum energy). This graph has profound implications. As time progresses, dark energy will become more and more dominant and will remain the dominant source of energy in the universe; since dark energy causes everything in the universe to expand, the universe will continue to expand without ever stopping. This graph, essentially, implies the ultimate fate of the universe. The universe will continue to expand more and more until it becomes dark, empty, and lifeless.</image:caption>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/gregschoollessons/2017/5/14/bentleys-and-olbers-paradoxes-e6hj4-pzpcf</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-10</lastmod>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a049ed5c8302552e4b72d05/1510252249221/</image:loc>
      <image:title>gregschool-lessons - Bentley's and Olber's Paradoxes</image:title>
      <image:caption>According to Olbers' paradox, if the universe is infinitely large with a uniform distribution of stars then the night sky should be blindingly bright.</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a05f1f2652dea8f286e5d9d/1510339073364/Olber%27s_Paradox_-_All_Points%5B1%5D.gif</image:loc>
      <image:title>gregschool-lessons - Bentley's and Olber's Paradoxes</image:title>
      <image:caption>"As more distant stars are revealed in this animation depicting an infinite, homogeneous and static universe, they fill the gaps between closer stars. Olbers's paradox argues that as the night sky is dark, one of these three assumptions about the nature of the universe must be false."\(^{[1]}\) Image by Kmarinas86 [GFDL (http://www.gnu.org/copyleft/fdl.html) or CC-BY-SA-3.0 (http://creativecommons.org/licenses/by-sa/3.0/)], via Wikimedia Commons</image:caption>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/gregschoollessons/2017/5/14/friedman-robertson-walker-frw-equation-s6f2m-ryshd</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-11</lastmod>
  </url>
  <url>
    <loc>https://www.gregschool.org/gregschoollessons/2017/5/14/surface-of-last-scattering-blnaz-936jb</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-11</lastmod>
  </url>
  <url>
    <loc>https://www.gregschool.org/gregschoollessons/2017/5/14/spectroscopy-9cnt6-tkzdb</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-11</lastmod>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a037a6ce4966bbdfaf2aed6/1494827814784/</image:loc>
      <image:title>gregschool-lessons - Spectroscopy</image:title>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/gregschoollessons/2017/6/16/formation-of-planets-and-stars-xa5hw-skf5t</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-08</lastmod>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a037a77652dea086dc9def3/1498195845727/</image:loc>
      <image:title>gregschool-lessons - A Brief Tour of our Milky Way Galaxy</image:title>
      <image:caption>Artist's depiction of the Milky Way Galaxy.</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a037a77652dea086dc9def5/1498157418533/mwpan_aitoff_s.jpg</image:loc>
      <image:title>gregschool-lessons - A Brief Tour of our Milky Way Galaxy</image:title>
      <image:caption>Picture of the Milky Way Galaxy as seen edge on.</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a037a77652dea086dc9def7/1498193304895/</image:loc>
      <image:title>gregschool-lessons - A Brief Tour of our Milky Way Galaxy</image:title>
      <image:caption>Inferred image of the center of the Milky Way Galaxy. (Source)</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a037a77652dea086dc9def9/1498195183058/430453main_crabmosaic_hst_big_full.jpg</image:loc>
      <image:title>gregschool-lessons - A Brief Tour of our Milky Way Galaxy</image:title>
      <image:caption>Image of Crab Nebula. (Image credit: NASA)</image:caption>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/gregschoollessons/2017/5/14/dark-matter-yla9j-kgnpm</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-08</lastmod>
  </url>
  <url>
    <loc>https://www.gregschool.org/gregschoollessons/2017/5/14/cosmic-microwave-background-radiation-lfmal-shpkt</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-08</lastmod>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a037a8ac830257e2fa357af/1494827005244/</image:loc>
      <image:title>gregschool-lessons - Cosmic Microwave Background Radiation</image:title>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/gregschoollessons/2017/5/14/dark-energy-exgdc-7538n</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-11</lastmod>
  </url>
  <url>
    <loc>https://www.gregschool.org/gregschoollessons/2017/8/30/finding-the-capacitance-of-a-parallel-plate-capacitor-ajby4-584gb</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-10</lastmod>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a037aabe4966bbdfaf2c466/1504480094587/Fig1.jpg</image:loc>
      <image:title>gregschool-lessons - Finding the Capacitance of a Parallel-Plate Capacitor</image:title>
      <image:caption>Figure 1: Parallel-plate capacitor. Each conductor is a flat plate with charges \(-Q\) and \(+Q\), areas of \(A\), and separated at a distance of \(d\). Courtesy of the Department of Physics and Astronomy, Michigan State University</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a037aaae4966bbdfaf2c464/1507605626845/electromagnetism+thumbnaillllll+imageeee.jpg</image:loc>
      <image:title>gregschool-lessons - Finding the Capacitance of a Parallel-Plate Capacitor</image:title>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/gregschoollessons/2017/5/18/brachistochrone-problem-8bgmb-zrgw7</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-08</lastmod>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a037ae453450a088000d620/1507588702724/gfnf.jpg</image:loc>
      <image:title>gregschool-lessons - Brachistochrone problem</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a037ae453450a088000d624/1495304353556/</image:loc>
      <image:title>gregschool-lessons - Brachistochrone problem</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a037ae453450a088000d626/1495304408606/</image:loc>
      <image:title>gregschool-lessons - Brachistochrone problem</image:title>
      <image:caption>Credit\(^{[3]}\)</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a037ae453450a088000d622/1495304339104/</image:loc>
      <image:title>gregschool-lessons - Brachistochrone problem</image:title>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/gregschoollessons/2017/5/18/generalized-coordinates-7r5bn-wlsm4</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-09</lastmod>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a037aec419202d77c1644b6/1507588890423/gfnf.jpg</image:loc>
      <image:title>gregschool-lessons - Generalized coordinates</image:title>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/gregschoollessons/2017/5/18/finding-the-geodesic-on-a-cylinder-mley2-h44tn</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-08</lastmod>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a037af4085229fe4473b195/1507588727041/gfnf.jpg</image:loc>
      <image:title>gregschool-lessons - Finding the geodesic on a cylinder</image:title>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/gregschoollessons/2017/6/20/derivation-of-guasss-law-from-columns-law-mbxrn-syd52</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-09</lastmod>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a037afcec212d3e0f543bb5/1501802501336/guass.jpg</image:loc>
      <image:title>gregschool-lessons - Derivation of Guass's Law from Column's Law</image:title>
      <image:caption>Figure 1 (click to enlarge)</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a037afcec212d3e0f543bb7/1501804297766/</image:loc>
      <image:title>gregschool-lessons - Derivation of Guass's Law from Column's Law</image:title>
      <image:caption>Figure 2 (click to enlarge)</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a037afcec212d3e0f543bb3/1507606994080/electromagnetism+thumbnaillllll+imageeee.jpg</image:loc>
      <image:title>gregschool-lessons - Derivation of Guass's Law from Column's Law</image:title>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/gregschoollessons/2017/5/18/v7t2klwmycopiblvbhzkhyw2duujqy-bjxsk-sxxc8</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-08</lastmod>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a037b0653450a088000e1ba/1507588749777/gfnf.jpg</image:loc>
      <image:title>gregschool-lessons - Introduction to Lagrangian Mechanics</image:title>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/gregschoollessons/2017/5/14/columns-law-7fdl2-rws49</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-11</lastmod>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a037b109140b70c95b2ccd8/1507607529720/electromagnetism+thumbnaillllll+imageeee.jpg</image:loc>
      <image:title>gregschool-lessons - Column's Law</image:title>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/gregschoollessons/2017/5/18/derivation-of-the-euler-lagrange-equation-s8wam-zntyn</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-08</lastmod>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a037b2853450a088000eb97/1507588781308/gfnf.jpg</image:loc>
      <image:title>gregschool-lessons - Derivation of the Euler-Lagrange Equation</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a037b2853450a088000eb99/1495304730085/</image:loc>
      <image:title>gregschool-lessons - Derivation of the Euler-Lagrange Equation</image:title>
      <image:caption>Figure 1 (click to expand)</image:caption>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/gregschoollessons/2017/7/20/using-guasss-law-to-find-the-electric-field-produced-by-a-single-point-charge-8m3gx-l22p3</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-08</lastmod>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a037b3f8165f535a0971fcb/1501807096166/</image:loc>
      <image:title>gregschool-lessons - Using Guass's Law to find the Electric Field Produced by a Single Point Charge</image:title>
      <image:caption>Figure 3</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a037b3f8165f535a0971fc7/1501804682969/guass.jpg</image:loc>
      <image:title>gregschool-lessons - Using Guass's Law to find the Electric Field Produced by a Single Point Charge</image:title>
      <image:caption>Figure 1</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a037b3f8165f535a0971fc9/1501805131555/</image:loc>
      <image:title>gregschool-lessons - Using Guass's Law to find the Electric Field Produced by a Single Point Charge</image:title>
      <image:caption>Figure 2</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a037b3f8165f535a0971fc5/1507607040412/electromagnetism+thumbnaillllll+imageeee.jpg</image:loc>
      <image:title>gregschool-lessons - Using Guass's Law to find the Electric Field Produced by a Single Point Charge</image:title>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/gregschoollessons/2017/5/14/electric-flux-enbx3-2af5w</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-10</lastmod>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a037b4853450a088000f2dc/1507606396620/electromagnetism+thumbnaillllll+imageeee.jpg</image:loc>
      <image:title>gregschool-lessons - Electric Flux</image:title>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/gregschoollessons/2017/5/18/noethers-theorem-78d8y-89f2j</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-08</lastmod>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a037b53c830257e2fa3972d/1507588859663/gfnf.jpg</image:loc>
      <image:title>gregschool-lessons - Noether’s Theorem</image:title>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/gregschoollessons/2017/5/18/what-do-we-mean-by-kinematics-dynamics-and-mechanics-xr2cr-fkz2j</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-08</lastmod>
  </url>
  <url>
    <loc>https://www.gregschool.org/gregschoollessons/2017/6/20/faxkbn1icm37pyljps0j38mgdt0t22-ch2g2-plga4</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-08</lastmod>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a037b84652dea086dca2eb4/1507582425469/Untitled.jpg</image:loc>
      <image:title>gregschool-lessons - Basic Equations of Kinematics</image:title>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/gregschoollessons/2017/8/28/newtons-law-of-gravity-ybhff-cl6dx</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-08</lastmod>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a037b95ec212d3e0f5465ca/1507582895064/Untitled.jpg</image:loc>
      <image:title>gregschool-lessons - Newton's Law of Gravity</image:title>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/gregschoollessons/2017/5/14/introduction-to-newtonian-mechanics-25a5e-xcb9m</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-08</lastmod>
  </url>
  <url>
    <loc>https://www.gregschool.org/gregschoollessons/2017/6/20/76hgztk8ogz149g9acwmizq62okwe4-cz2yr-m7abr</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-08</lastmod>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a037ba5c830257e2fa3ae1b/1501788322829/</image:loc>
      <image:title>gregschool-lessons - Position Vectors, Displacement, Velocity, and Acceleration</image:title>
      <image:caption>Figure 2</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a037ba5c830257e2fa3ae17/1507582470969/Untitled.jpg</image:loc>
      <image:title>gregschool-lessons - Position Vectors, Displacement, Velocity, and Acceleration</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a037ba5c830257e2fa3ae19/1501784000999/</image:loc>
      <image:title>gregschool-lessons - Position Vectors, Displacement, Velocity, and Acceleration</image:title>
      <image:caption>Figure 1 (click to enlarge)</image:caption>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/gregschoollessons/2017/8/29/newtons-three-laws-of-motion-62d9d-emyyp</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-08</lastmod>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a037baf24a6943d6bba4413/1507582682482/Untitled.jpg</image:loc>
      <image:title>gregschool-lessons - Newton's Three Laws of Motion</image:title>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/gregschoollessons/2017/8/10/derivation-on-momentum-conservation-bxjp5-pe7wa</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-08</lastmod>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a037bbde2c483e53cae60f5/1507586881155/gfnf.jpg</image:loc>
      <image:title>gregschool-lessons - Derivation of Momentum Conservation</image:title>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/gregschoollessons/2017/8/10/introduction-to-linear-momentum-mbs6h-a3eh4</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-11</lastmod>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a037bc8419202d77c1682f3/1507586693883/gfnf.jpg</image:loc>
      <image:title>gregschool-lessons - Introduction to Linear Momentum</image:title>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/gregschoollessons/2017/8/28/motion-of-objects-experiancing-air-friction-wheys-9sakr</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-11</lastmod>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a037bd58165f535a0974945/1507586453265/gfnf.jpg</image:loc>
      <image:title>gregschool-lessons - Motion of objects experiencing air friction</image:title>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/gregschoollessons/2017/6/21/the-abstract-has-a-lot-to-say-about-the-physical-world-xk4tb-7mtn7</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-08</lastmod>
  </url>
  <url>
    <loc>https://www.gregschool.org/gregschoollessons/2017/5/14/xe30zrw2tke0y051q8xdpf9cxaff19-fyzrj-85zyn</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-11</lastmod>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a0631b824a6942e849f5e6e/1510355396579/cosmolg.jpg</image:loc>
      <image:title>gregschool-lessons - Scaling Factor, Hubble's Parameter, and the Age of the Universe</image:title>
      <image:caption>Figure 1: The coordinate value \(x^i\) assigned to each tick mark in the rectangular coordinate system above remains the same as the coordinate system stretches or contracts. Only the scaling factor \(a(t)\) changes when the coordinate system stretches or contracts.</image:caption>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/gregschoollessons/2017/8/10/inelastic-collisions-mjsnh-ygw3m</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-10</lastmod>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a05bb30652dea801332e747/1510325044804/InelCol%5B1%5D.gif</image:loc>
      <image:title>gregschool-lessons - Inelastic Collisions</image:title>
      <image:caption>Figure 1: An inelastic collision is when two objects collide and stick together. Each object becomes conjoined and moves away with equal velocities.</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a037c189140b70c95b31521/1507587059265/gfnf.jpg</image:loc>
      <image:title>gregschool-lessons - Inelastic Collisions</image:title>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/gregschoollessons/2017/5/14/4ufuuy7fweohxl2tk6hryzmsq50amd-a67kn-yp26b</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-08</lastmod>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a037c1fe2c483e53cae7f87/1507588058521/gfnf.jpg</image:loc>
      <image:title>gregschool-lessons - Introduction to Mechanical Waves</image:title>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/gregschoollessons/2017/5/14/rotational-kinematics-5xef2-wy987</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-08</lastmod>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a037c29e4966bbdfaf330e9/1507588198193/gfnf.jpg</image:loc>
      <image:title>gregschool-lessons - Rotational Kinematics</image:title>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/gregschoollessons/2017/5/14/introduction-to-rotational-kinetic-energy-b8hy8-dreh5</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-08</lastmod>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a037c319140b70c95b31c75/1507588322330/gfnf.jpg</image:loc>
      <image:title>gregschool-lessons - Introduction to Rotational Kinetic Energy</image:title>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/gregschoollessons/2017/5/14/torque-6zmaw-amjpk</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-11</lastmod>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a037c42f9619a0fd0c17cc7/1507588457714/gfnf.jpg</image:loc>
      <image:title>gregschool-lessons - Torque</image:title>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/gregschoollessons/2017/8/26/work-measure-of-energy-transfer-5kccp-p3dsg</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-08</lastmod>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a037c4dec212d3e0f5498d2/1507587499632/gfnf.jpg</image:loc>
      <image:title>gregschool-lessons - Work: Measure of Energy Transfer</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a037c4dec212d3e0f5498d0/1504544870969/ff.png</image:loc>
      <image:title>gregschool-lessons - Work: Measure of Energy Transfer</image:title>
      <image:caption>Figure 1: Work done on a block by a constant force of \(-10\) newtons over a displacement of \(5\) meters.</image:caption>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/gregschoollessons/2017/6/21/the-dependency-of-theta-in-the-dot-product-a6rdd-m5x4z</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-08</lastmod>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a037c55c830257e2fa3ddaa/1507587268526/gfnf.jpg</image:loc>
      <image:title>gregschool-lessons - The Dependency of theta in the dot product</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a037c55c830257e2fa3dda8/1501801080881/</image:loc>
      <image:title>gregschool-lessons - The Dependency of theta in the dot product</image:title>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/gregschoollessons/2017/8/26/work-done-by-earths-gravity-nfmxr-wpxmy</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2018-09-11</lastmod>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a037c66419202d77c16ad11/1507587669020/gfnf.jpg</image:loc>
      <image:title>gregschool-lessons - Work done by Earth's Gravity</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a037c66419202d77c16ad0f/1504580902846/vv.png</image:loc>
      <image:title>gregschool-lessons - Work done by Earth's Gravity</image:title>
      <image:caption>Figure 1: As an object moves along the path \(\vec{R}(t)\) from an initial height of \(y_i\) to a final height of \(y_f\), the Earth's gravitational force \(-m\vec{g}\) does work on the object.</image:caption>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/gregschoollessons/2017/8/27/work-done-by-force-moving-an-object-at-constant-height-dxkzp-m6742</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-08</lastmod>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a037c6f652dea086dca6e9d/1507587696400/gfnf.jpg</image:loc>
      <image:title>gregschool-lessons - Work-Kinetic Energy Theorem</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a037c6f652dea086dca6e9f/1504580497144/wet2.gif</image:loc>
      <image:title>gregschool-lessons - Work-Kinetic Energy Theorem</image:title>
      <image:caption>Figure 1: "Sunil Kumar Singh, Work - Kinetic Energy Theorem. February 2, 2013." http://cnx.org/content/m14095/latest/OpenStax CNX CC BY 3.0.</image:caption>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/gregschoollessons/2017/5/14/genesis-of-the-elements-xz53h-kphyl</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-11</lastmod>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a037c91e4966bbdfaf349c0/1509987202844/</image:loc>
      <image:title>gregschool-lessons - Genesis of the Elements</image:title>
      <image:caption>Figure 4: As a star undergoes nuclear fusion in its core, it generates light. This light exerts an outward radiation pressure on the star which balances the inward gravitational forces that tend to pull the star's matter towards its center. But at the end of a star's life, nuclear fusion begins to slow down and eventually stop; this means that there is no outward radiation pressure to balance the gravitational forces exerted on the outward layers of the star and star eventually collapses. If the star is very massive, such a collapse will result in one of the most spectacular events in the universe: a supernova. The energy generated by a supernova explosion is so stupendous that it results in nuclear reactions which create the heavier elements in the period table.</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a037c91e4966bbdfaf349ba/1509981827221/RutherfordGoilFoil+%281%29%5B1%5D.jpg</image:loc>
      <image:title>gregschool-lessons - Genesis of the Elements</image:title>
      <image:caption>Figure 1: Rutherford's experiment involved putting a radioactive element known as radium inside of a lead box. The radium spontaneously emitted \(α\) particles in a narrow beam through a small hole in the box. These \(α\) particles were directed towards a gold foil. Most \(α\) particles passed straight through the gold foil but occasional one would get reflected back at an acute angle with the beam of \(α\) particles. This meant that atoms must have tiny, but very dense, nuclei. Image credit: http://m.teachastronomy.com/astropedia/article/The-Structure-of-the-Atom</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a037c91e4966bbdfaf349bc/1509983399387/nuclear-fusion-stars%5B1%5D.png</image:loc>
      <image:title>gregschool-lessons - Genesis of the Elements</image:title>
      <image:caption>Figure 2: All stars in the universe generate light and energy by fusing lighter elements into heavier elements. For stars up to the mass of about that of our Sun, light and energy is created by fusing hydrogen into helium. The image above illustrates the chain of nuclear reactions which occur in small to medium sized stars and very massive stars that allow them to generate light and energy. Stellar fusion accounts for where many of the light to medium-sized elements in the periodic table come from.</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a037c91e4966bbdfaf349be/1509985102690/</image:loc>
      <image:title>gregschool-lessons - Genesis of the Elements</image:title>
      <image:caption>Figure 3: The Alpha-Beta-Gamma paper demonstrated that after the first roughly three minutes of the universe since its initial Bang, hydrogen and helium nuclei were synthesized via nuclear fusion. After about three minutes, the universe cooled enough for fusion to stop; but the universe was still so hot that all of the matter comprising the universe was a plasma and plasma's are opaque to radiation. The matter comprising the universe was in a plasma state for the first roughly 300,000 years since the Big Bang; since plasma is opaque to radiation, for the first roughly 300,000 years light could not freely travel throughout the universe without constantly "bumping into stuff (atomic nuclei)." At sometime when the universe was about 300,000 to 400,000 years old, matter cooled enough for electrons to bind to atomic nuclei and for light to freely pass through the universe. Due to the expansion of space, Alpher and Herman estimated that wavelengths of this light should now be stretched into the microwave region.</image:caption>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/gregschoollessons/2017/6/12/snowball-earth-p5pbn</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2019-03-23</lastmod>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/5c967da34e17b612ddddc14c/5c967f3824a694bdfd470e9a/1553366841813/cosmos_9035489_001_72dpi.jpg</image:loc>
      <image:title>gregschool-lessons - Snowball Earth</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/5c967fed9140b79a9b3337f3/5c9680d81972fb0001fb6dd3/1553367257073/Facts-2.jpg</image:loc>
      <image:title>gregschool-lessons - Snowball Earth</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a037c9d53450a0880014c79/1497300036844/</image:loc>
      <image:title>gregschool-lessons - Snowball Earth</image:title>
      <image:caption>Picture of Earth 750 million years ago when the supercontinent Rodinia was getting torn apart. (Click to expand.)</image:caption>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/gregschoollessons/2017/5/4/colonizing-the-moon-yl6rd</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2019-02-22</lastmod>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/5b98a960575d1ff027c1f3fc/5b98a9634d7a9cbbeab1dda1/1536731624539/Lunar_base_concept_drawing_s78_23252%5B1%5D.jpg</image:loc>
      <image:title>gregschool-lessons - Colonizing the Moon - Lunar Mass Driver</image:title>
      <image:caption>Artist’s depiction of a lunar mass driver. The physicist Gerard K. O’Neil imagined using this device to electromagnetically launch lunar material into space for the purpose of being using to construct artificial space habitats for human residence and to move most industry off the Earth and into space. Image courtesy of NASA.</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5b98a8770e2e72043c39e14f/1536731258919/fig0801%5B1%5D.gif</image:loc>
      <image:title>gregschool-lessons - Colonizing the Moon</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/5a037cb908522944d44c5796/5a037cb908522944d44c579d/1498698373172/.jpg</image:loc>
      <image:title>gregschool-lessons - Colonizing the Moon</image:title>
      <image:caption>The Smart Things Future Living Report</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/5a037cb908522944d44c5796/5a037cb908522944d44c5797/1498698373166/LunarColonyRawlings650.jpg</image:loc>
      <image:title>gregschool-lessons - Colonizing the Moon</image:title>
      <image:caption>Domed lunar settlement illustration by Pat Rawlings, courtesy NASA.</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/5a037cb908522944d44c5796/5a037cb908522944d44c579b/1498698373171/landscape-1436809198-1197px-inflatable-habitat-s89-20084.jpg</image:loc>
      <image:title>gregschool-lessons - Colonizing the Moon</image:title>
      <image:caption>Artist concept of a moon colony via NASA</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/5a037cb908522944d44c5796/5a037cb908522944d44c5799/1498698373169/LeapOfFaith.jpg</image:loc>
      <image:title>gregschool-lessons - Colonizing the Moon</image:title>
      <image:caption>Painting by Pat Rawlings courtesy NASA</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a037cb908522944d44c5794/1507664167600/space+travela+nd+colonization+thumbnail.jpg</image:loc>
      <image:title>gregschool-lessons - Colonizing the Moon</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5b98a88b2b6a28301fa44fb2/1536731281125/fig0802%5B1%5D.gif</image:loc>
      <image:title>gregschool-lessons - Colonizing the Moon</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/5b98a8f4562fa774edff9e54/5b98a8f44d7a9cbbeab1da5c/1536731782111/Oneilcylinder1.jpg</image:loc>
      <image:title>gregschool-lessons - Colonizing the Moon</image:title>
      <image:caption>O’Neill cylinders</image:caption>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/gregschoollessons/2017/4/27/colonizing-the-asteroids-and-comets-of-our-solar-system-clyl4</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-08</lastmod>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a037ccd08522944d44c5d78/1502343637033/</image:loc>
      <image:title>gregschool-lessons - Colonizing the Asteroids and Comets of our Solar System</image:title>
      <image:caption>Figure 1 (click to enlarge)</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a037ccd08522944d44c5d7a/1493345091357/WANDERERS_terrarium_01.jpg</image:loc>
      <image:title>gregschool-lessons - Colonizing the Asteroids and Comets of our Solar System</image:title>
      <image:caption>Figure 2 - click to enlarge (Source) "This shot shows the inside of the asteroid from the previous scene. Just as I wrote about that scene, this is a highly speculative vision of an impressive piece of human engineering - a concept that science fiction author Kim Stanley Robinson calls a "terraruim" in his novel "2312". It is also not unlike what Arthur C. Clarke described in his novel "Rendezvous with Rama". What we see here is the inside of a hollowed out asteroid, pressurized and filled with a breathable atmosphere. Like I described in the previous scene, the whole structure is put into a revolving rotation, simulating the effect of gravity toward the inside "walls" of the cylinder shape we see. The structure in this scene has a diameter of about 7 kilometers and revolves with a speed of 1 rotation every 2 minutes, simulating the effect of 1g (the gravity pull we feel on Earth) at the surface of the inside. This place is also filled with water, creating lakes and seas wrapped along with the landscape. An artificial sun is running along a rail in the middle of the space, simulating a daylight cycle. This scene is of course built from scratch, but I used countless satellite photos of the Earth to texture the landscape. I actually used a slightly warped world map to create the outlines between land and water, as some may notice a couple of familiar shorelines."\(^{[3]}\)</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a037ccd08522944d44c5d76/1507664334394/space+travela+nd+colonization+thumbnail.jpg</image:loc>
      <image:title>gregschool-lessons - Colonizing the Asteroids and Comets of our Solar System</image:title>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/gregschoollessons/2017/2/13/introduction-to-einsteins-theory-of-general-relativity-mp9y7</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-08</lastmod>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a037cd6652dea086dca87b2/1490733558102/</image:loc>
      <image:title>gregschool-lessons - Introduction to Einstein's Theory of General Relativity</image:title>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/gregschoollessons/2017/1/23/superconductors-the-future-of-transportation-and-electric-transmission-d5e6r</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2019-03-23</lastmod>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a037cea652dea086dca8c03/1509744550746/email+img+thumbnail.jpg</image:loc>
      <image:title>gregschool-lessons - Superconductors: the Future of Transportation and Electric Transmission</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a037cea652dea086dca8bfd/1509744831827/facebook+img+thumbnail.jpg</image:loc>
      <image:title>gregschool-lessons - Superconductors: the Future of Transportation and Electric Transmission</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a037cea652dea086dca8bff/1509744812574/twiiter+img+thumbnail.jpg</image:loc>
      <image:title>gregschool-lessons - Superconductors: the Future of Transportation and Electric Transmission</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a037cea652dea086dca8c05/1509744531017/technology+thumbnail.png</image:loc>
      <image:title>gregschool-lessons - Superconductors: the Future of Transportation and Electric Transmission</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a037cea652dea086dca8c01/1509744847045/</image:loc>
      <image:title>gregschool-lessons - Superconductors: the Future of Transportation and Electric Transmission</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a037cea652dea086dca8bfb/1509744676939/</image:loc>
      <image:title>gregschool-lessons - Superconductors: the Future of Transportation and Electric Transmission</image:title>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/gregschoollessons/2017/2/17/thermodynamics-and-the-arrow-of-time-zsgz8</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-08</lastmod>
  </url>
  <url>
    <loc>https://www.gregschool.org/gregschoollessons/2017/3/27/light-fidelity-li-fi-ultra-fast-wireless-communications-system-49mxf</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2019-03-23</lastmod>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a037cfde2c483e53caeb602/1509744407032/twiiter+img+thumbnail.jpg</image:loc>
      <image:title>gregschool-lessons - Light Fidelity (Li-Fi): Ultra-Fast, Wireless Communications System</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a037cfde2c483e53caeb60a/1490641020901/</image:loc>
      <image:title>gregschool-lessons - Light Fidelity (Li-Fi): Ultra-Fast, Wireless Communications System</image:title>
      <image:caption>Figure 1</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a037cfde2c483e53caeb606/1509744154145/email+img+thumbnail.jpg</image:loc>
      <image:title>gregschool-lessons - Light Fidelity (Li-Fi): Ultra-Fast, Wireless Communications System</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a037cfde2c483e53caeb604/1509744456561/google+img+thumbnail.jpg</image:loc>
      <image:title>gregschool-lessons - Light Fidelity (Li-Fi): Ultra-Fast, Wireless Communications System</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a037cfde2c483e53caeb600/1509744439536/facebook+img+thumbnail.jpg</image:loc>
      <image:title>gregschool-lessons - Light Fidelity (Li-Fi): Ultra-Fast, Wireless Communications System</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a037cfde2c483e53caeb5fc/1509744247982/share+technology++img.jpg</image:loc>
      <image:title>gregschool-lessons - Light Fidelity (Li-Fi): Ultra-Fast, Wireless Communications System</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a037cfde2c483e53caeb608/1509744129041/technology+thumbnail.png</image:loc>
      <image:title>gregschool-lessons - Light Fidelity (Li-Fi): Ultra-Fast, Wireless Communications System</image:title>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/gregschoollessons/2017/3/14/exponential-growth-of-information-technology-1-hkykf</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-10</lastmod>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a037d138165f535a0979af5/1509744984223/email+img+thumbnail.jpg</image:loc>
      <image:title>gregschool-lessons - Exponential Growth of Information Technology</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a037d138165f535a0979aed/1509745093086/share+technology++img.jpg</image:loc>
      <image:title>gregschool-lessons - Exponential Growth of Information Technology</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a037d138165f535a0979af3/1509745212285/google+img+thumbnail.jpg</image:loc>
      <image:title>gregschool-lessons - Exponential Growth of Information Technology</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a037d138165f535a0979aef/1509745182840/facebook+img+thumbnail.jpg</image:loc>
      <image:title>gregschool-lessons - Exponential Growth of Information Technology</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a037d138165f535a0979af1/1509745198013/twiiter+img+thumbnail.jpg</image:loc>
      <image:title>gregschool-lessons - Exponential Growth of Information Technology</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a037d138165f535a0979af7/1509744969681/technology+thumbnail.png</image:loc>
      <image:title>gregschool-lessons - Exponential Growth of Information Technology</image:title>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/gregschoollessons/2017/5/23/calculating-the-wavefunction-collection-of-probability-amplitudes-associated-with-any-ket-vector-skh4m-ey7ag-jtfne</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-11</lastmod>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a037d3171c10b64691e0cc8/1507610296214/electromagnetism+thumbnaillllll+imageeee.jpg</image:loc>
      <image:title>gregschool-lessons - Calculating the Wavefunction Associated with any Ket Vector</image:title>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/gregschoollessons/2017/5/15/time-evolution-of-state-vectors-c6g7n-dwall</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-08</lastmod>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a037d40ec212d3e0f54dc6d/1510107139616/1_Lwu5UJMmcuFVJLZ1Ln4E0Q%5B1%5D.png</image:loc>
      <image:title>gregschool-lessons - Schrodinger's Time-Dependent Equation: Time-Evolution of State Vectors</image:title>
      <image:caption>Figure 1: The motion of a simple pendulum is an example of the time-reversibility of Newton's second law. Given the initial state of the pendulum, Newton's second law can be used to determine the past or future state of the system. For example, one could determine the velocity and position of the pendulum at any past or future time given its present state.</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a037d40ec212d3e0f54dc6f/1510108488383/photon_double_slit2%5B1%5D.gif</image:loc>
      <image:title>gregschool-lessons - Schrodinger's Time-Dependent Equation: Time-Evolution of State Vectors</image:title>
      <image:caption>Figure 2: Schrodinger's equation is deterministic because the past or future quantum state \(|\psi(t)⟩\) of a quantum system can be determined with infinite precision. But, in general, a quantum system can be in a superposition of many different states where the measurement of any physical quantity is uncertain. For example, if anything the size of a small molecule or smaller passes through a double-slit in a double-slit experiment, where it hits the screen (which is to say, its final position) is uncertain (see illustration above). The quantum state of a quantum system is deterministic; but the eigenvalue that you'll measure after an experiment is done is the quantity which is not deterministic in quantum mechanics. Source: http://abyss.uoregon.edu/~js/21st_century_science/lectures/lec13.html</image:caption>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/gregschoollessons/2017/6/16/overview-of-calculus-hmtnx-xzysh</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-08</lastmod>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a037d50e2c483e53caeca88/1497934508324/</image:loc>
      <image:title>gregschool-lessons - Overview of Single-Variable Calculus</image:title>
      <image:caption>Figure 2</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a037d50e2c483e53caeca8e/1497933579348/</image:loc>
      <image:title>gregschool-lessons - Overview of Single-Variable Calculus</image:title>
      <image:caption>Figure 5</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a037d50e2c483e53caeca86/1497934480889/</image:loc>
      <image:title>gregschool-lessons - Overview of Single-Variable Calculus</image:title>
      <image:caption>Figure 1</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a037d50e2c483e53caeca8c/1497933573517/</image:loc>
      <image:title>gregschool-lessons - Overview of Single-Variable Calculus</image:title>
      <image:caption>Figure 4</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a037d50e2c483e53caeca84/1510078784067/Untitled.jpg</image:loc>
      <image:title>gregschool-lessons - Overview of Single-Variable Calculus</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a037d50e2c483e53caeca8a/1497931192368/</image:loc>
      <image:title>gregschool-lessons - Overview of Single-Variable Calculus</image:title>
      <image:caption>Figure 3</image:caption>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/gregschoollessons/2017/5/15/periodic-wavefunctions-that-is-ones-that-come-back-to-themselves-have-quantized-eigenvalues-of-momenta-and-angular-momenta-2k3el-hrfk7</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-08</lastmod>
  </url>
  <url>
    <loc>https://www.gregschool.org/gregschoollessons/2017/5/23/the-eigenvectors-of-any-hermitian-operator-must-be-orthogonal-w2jps-fm7r7</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-08</lastmod>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a037d6dc830257e2fa42154/1510110338040/electromagnetism+thumbnaillllll+imageeee.jpg</image:loc>
      <image:title>gregschool-lessons - The Eigenvectors of any Hermitian Operator must be Orthogonal</image:title>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/gregschoollessons/2017/5/27/origin-of-structure-and-clumpyness-dbe4t-snxy5</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-11</lastmod>
  </url>
  <url>
    <loc>https://www.gregschool.org/gregschoollessons/2017/5/14/how-initial-states-of-definite-energy-change-with-time-5hyrx-9wkx4</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-08</lastmod>
  </url>
  <url>
    <loc>https://www.gregschool.org/gregschoollessons/2017/6/12/crispr-cas9-gene-editing-rz8n7</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-08</lastmod>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a037d8ce4966bbdfaf38714/1497325314908/</image:loc>
      <image:title>gregschool-lessons - CRISPR-CAS9 Gene Editing</image:title>
      <image:caption>Figure 1                            Source\(^{[1]}\)</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a037d8ce4966bbdfaf38718/1497325759187/rrr.png</image:loc>
      <image:title>gregschool-lessons - CRISPR-CAS9 Gene Editing</image:title>
      <image:caption>Figure 3                                         Source</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a037d8ce4966bbdfaf38716/1497325436986/</image:loc>
      <image:title>gregschool-lessons - CRISPR-CAS9 Gene Editing</image:title>
      <image:caption>Figure 2                                          Source</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a037d8ce4966bbdfaf3871a/1497325731797/</image:loc>
      <image:title>gregschool-lessons - CRISPR-CAS9 Gene Editing</image:title>
      <image:caption>Figure 4 (click to enlarge)</image:caption>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/gregschoollessons/2017/3/22/p-series-convergence-and-divergence-r69x7</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-08</lastmod>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a037d95e2c483e53caedb0e/1490229889184/</image:loc>
      <image:title>gregschool-lessons - P-Series Convergence and Divergence</image:title>
      <image:caption>Figure 2 (click to enlarge)</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a037d95e2c483e53caedb0c/1490231132628/</image:loc>
      <image:title>gregschool-lessons - P-Series Convergence and Divergence</image:title>
      <image:caption>Figure 1 (click to enlarge)</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a037d95e2c483e53caedb0a/1507581648482/Untitled.jpg</image:loc>
      <image:title>gregschool-lessons - P-Series Convergence and Divergence</image:title>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/gregschoollessons/2017/9/25/colonizing-and-terraforming-venus</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2018-04-08</lastmod>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5ac95549352f53a44fcd4b06/1523145700558/facebook+thumbnail.jpg</image:loc>
      <image:title>gregschool-lessons - Colonizing and Terraforming Venus</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59d3eb791f318d2d58af61ee/1523145700569/1.10-1024x768.jpg</image:loc>
      <image:title>gregschool-lessons - Colonizing and Terraforming Venus</image:title>
      <image:caption>Artist concept of lightning on Venus. Image credit: ESA</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5ac955750e2e72f4e58b5a70/1523145700562/google+share+thumbnail_preview.jpg</image:loc>
      <image:title>gregschool-lessons - Colonizing and Terraforming Venus</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59d3e94ecd39c3acbc034421/1523145700570/venus-cloud-city.jpg</image:loc>
      <image:title>gregschool-lessons - Colonizing and Terraforming Venus</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5ac955652b6a289d089b266f/1523145700565/email+thumbnail_preview.jpg</image:loc>
      <image:title>gregschool-lessons - Colonizing and Terraforming Venus</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5ac95554562fa799825bd630/1523145700560/Twitter+thumbnail_preview.jpg</image:loc>
      <image:title>gregschool-lessons - Colonizing and Terraforming Venus</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a0e3b1ec830258272ef160e/1523145700572/TerraformedVenus%5B1%5D.jpg</image:loc>
      <image:title>gregschool-lessons - Colonizing and Terraforming Venus</image:title>
      <image:caption>"A conceptual picture I made of Venus if it were terraformed. (Credit: Daein Ballard) Notice the interesting cloud formations and that the planet has polar caps. I decided to show the planet this way after studying Venus' atmosphere. The two Hadley cells the planet has stop at 70 degrees north and south. So the polar regions are cut off from the warm air. Also the slow rotation of the planet causes the clouds to whip around the planet very fast, especially at the equator, to balance out the temperature difference between day and night sides of the planet."\(^{[5]}\) Image credit: Ittiz at the English language Wikipedia [GFDL (http://www.gnu.org/copyleft/fdl.html) or CC-BY-SA-3.0 (http://creativecommons.org/licenses/by-sa/3.0/)], via Wikimedia Commons</image:caption>
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      <image:title>gregschool-lessons - Colonizing and Terraforming Venus</image:title>
    </image:image>
    <image:image>
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      <image:title>gregschool-lessons - Colonizing and Terraforming Venus</image:title>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/gregschoollessons/2017/9/10/how-to-produce-water-and-oxygen-on-mars</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2018-04-08</lastmod>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5ac957c588251b5348314cf2/1523144855332/Twitter+thumbnail_preview.jpg</image:loc>
      <image:title>gregschool-lessons - How to Produce Water and Oxygen on Mars</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a0e4a8ff9619ae2895df378/1523144855341/mars3%5B1%5D.jpg</image:loc>
      <image:title>gregschool-lessons - How to Produce Water and Oxygen on Mars</image:title>
      <image:caption>The rover above is capable of releasing frozen water from regolith by heating it using microwaves. Credit: SUTD/Gilmour Space Corporation</image:caption>
    </image:image>
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      <image:title>gregschool-lessons - How to Produce Water and Oxygen on Mars</image:title>
    </image:image>
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      <image:title>gregschool-lessons - How to Produce Water and Oxygen on Mars</image:title>
    </image:image>
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      <image:title>gregschool-lessons - How to Produce Water and Oxygen on Mars</image:title>
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    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a0e549de2c48384bd2b1733/1523144855339/extracting+water+from+Mars%27+regolith.jpg</image:loc>
      <image:title>gregschool-lessons - How to Produce Water and Oxygen on Mars</image:title>
      <image:caption>"Truck, oven, and slag pile system for extracting water from Martian soil."\(^{[2]}\) Artwork by Michael Carroll.</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5ac957a603ce649b2a21efee/1523144855328/share+b.jpg</image:loc>
      <image:title>gregschool-lessons - How to Produce Water and Oxygen on Mars</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5ac9579188251b534831466e/1523144855337/space+colon+author+date.jpg</image:loc>
      <image:title>gregschool-lessons - How to Produce Water and Oxygen on Mars</image:title>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/gregschoollessons/2017/9/24/introduction-to-double-integrals-1-9ekxy</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2018-04-08</lastmod>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5ac97c64aa4a998f3f360dd8/1523154033161/sharee.png</image:loc>
      <image:title>gregschool-lessons - Introduction to Double Integrals</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5ac979d703ce649b2a262570/1523153372892/Calculus+thumbnail.png</image:loc>
      <image:title>gregschool-lessons - Introduction to Double Integrals</image:title>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5ac97a212b6a289d089fb811/1523153455649/email+thumbnail.jpg</image:loc>
      <image:title>gregschool-lessons - Introduction to Double Integrals</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5ac97782aa4a998f3f357921/1509398380899/riemann_boxes_m.jpg</image:loc>
      <image:title>gregschool-lessons - Introduction to Double Integrals</image:title>
      <image:caption>Figure 1: When we were deriving an expression for the definite integral in terms of the Riemann sum, we first approximated the area underneath \(f(x)\) by summing the areas of many very skinny rectangles as illustrated in (A). To define a double integral in terms of a Riemann sum, we first approximate the volume underneath a surface by summing the volumes of many very skinny columns as depicted in (C). The width and depth of each column is given by \(Δx\) and \(Δy\) and the height of each rectangle is given by the surface \(f(x,y)\) as shown in (B).</image:caption>
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      <image:title>gregschool-lessons - Introduction to Double Integrals</image:title>
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      <image:title>gregschool-lessons - Introduction to Double Integrals</image:title>
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      <image:title>gregschool-lessons - Introduction to Double Integrals</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5ac97782aa4a998f3f357923/1507232588323/partial+der.jpg</image:loc>
      <image:title>gregschool-lessons - Introduction to Double Integrals</image:title>
      <image:caption>Figure 2: The volume underneath the surface \(f(x,y)\) can be approximated by summing the volumes of an \(nm\) number of columns underneath the surface. As these columns become infinitesimally skinny and as the number \(nm\) of them approaches infinity, this sum gives the exact volume underneath the surface \(f(x,y)\).</image:caption>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/gregschoollessons/2017/10/30/gravitational-force-exerted-by-a-sphere</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2018-09-03</lastmod>
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      <image:title>gregschool-lessons - Gravitational Force Exerted by a Sphere</image:title>
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      <image:title>gregschool-lessons - Gravitational Force Exerted by a Sphere</image:title>
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      <image:title>gregschool-lessons - Gravitational Force Exerted by a Sphere</image:title>
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      <image:title>gregschool-lessons - Gravitational Force Exerted by a Sphere</image:title>
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      <image:title>gregschool-lessons - Gravitational Force Exerted by a Sphere</image:title>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5aca50a7352f53a44fe5ac6e/1523209296661/email+thumbnail.jpg</image:loc>
      <image:title>gregschool-lessons - Gravitational Force Exerted by a Sphere</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5aca42ec88251b5348475405/1523209296668/sphere+force.png</image:loc>
      <image:title>gregschool-lessons - Gravitational Force Exerted by a Sphere</image:title>
      <image:caption>Figure 1: A shell can be subdivided into many very skinny rings. Anyone of these rings can be represented by the ring \(QRR_1Q_1\) illustrated above. Image credit\(^{[1]}\).</image:caption>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/gregschoollessons/2017/11/2/gravitational-force-exerted-by-a-rod-zf4pf-np6lw</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2019-02-09</lastmod>
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      <image:title>gregschool-lessons - Gravitational Force Exerted by a Rod</image:title>
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      <image:title>gregschool-lessons - Gravitational Force Exerted by a Rod</image:title>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5acb88c56d2a73d3a0140067/1509666905146/rod.png</image:loc>
      <image:title>gregschool-lessons - Gravitational Force Exerted by a Rod</image:title>
      <image:caption>Figure 1: A rod of mass \(M\) and a particle of mass \(m\) are separated from each other by a distance of \(d\) along the \(x\)-axis. Each mass element \(dm\) comprising the rod is located at some position \(x\) along the \(x\)-axis and is separated from the particle \(m\) by some amount \(r\). By summing all the gravitational forces \(d\vec{F}_g\) exerted by each mass element \(dm\) comprising the rod, we can find the total gravitational force exerted on \(m\) by the entire rod.</image:caption>
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      <image:title>gregschool-lessons - Gravitational Force Exerted by a Rod</image:title>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5acb88c56d2a73d3a014005f/1523288004050/Twitter+thumbnail.jpg</image:loc>
      <image:title>gregschool-lessons - Gravitational Force Exerted by a Rod</image:title>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5acb88c56d2a73d3a014005b/1523288053202/sharee.png</image:loc>
      <image:title>gregschool-lessons - Gravitational Force Exerted by a Rod</image:title>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5acb88c56d2a73d3a0140065/1523287857170/classical+mechanics+thumbnail.png</image:loc>
      <image:title>gregschool-lessons - Gravitational Force Exerted by a Rod</image:title>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/gregschoollessons/2017/9/30/proof-of-greens-theorem</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2018-09-03</lastmod>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5b3455ab0e2e7239ad71b4df/1530163356513/twiiter+img+thumbnail.jpg</image:loc>
      <image:title>gregschool-lessons - Proof of Green's Theorem</image:title>
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    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59d01a96f43b5501b2e62104/1530163356523/429px-Green%27s-theorem-simple-region.svg.png</image:loc>
      <image:title>gregschool-lessons - Proof of Green's Theorem</image:title>
      <image:caption>Figure 1: The curve \(C=C_1+C_2+C_3+C_4\) is piece-wise smooth. It is "piece-wise" because it is split up into an \(n=4\) number of separate curves with an \(n=4\) number of "edges." It is "smooth" because each individual curve itself is smooth without any sharp edges or cusps. This curve is also positively-oriented because its direction goes counter-clockwise. Image by Cronholm 144.</image:caption>
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      <image:title>gregschool-lessons - Proof of Green's Theorem</image:title>
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      <image:title>gregschool-lessons - Proof of Green's Theorem</image:title>
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      <image:title>gregschool-lessons - Proof of Green's Theorem</image:title>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5b3453e70e2e7239ad7177f7/1530163356521/Calculus+thumbnail.png</image:loc>
      <image:title>gregschool-lessons - Proof of Green's Theorem</image:title>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5b3557262b6a28a0366206ba/1530222380477/images.png</image:loc>
      <image:title>gregschool-lessons - Proof of Green's Theorem</image:title>
      <image:caption>Figure 3: We can break up the curve \(c\) into the two separate curves, \(c_1\) and \(c_2\). This also allows us to break up the function \(x(y)\) into the two separate functions, \(x_1(y)\) and \(x_2(y)\).</image:caption>
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      <image:title>gregschool-lessons - Proof of Green's Theorem</image:title>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5b355639575d1f7d68cd861b/1530222142601/images.png</image:loc>
      <image:title>gregschool-lessons - Proof of Green's Theorem</image:title>
      <image:caption>Figure 2: We can split the curve \(c\) into two separate curves, \(c_1\) and \(c_2\). This also allows us to split the function \(y(x)\) into the two separate functions, \(y_1(x)\) and \(y_2(x)\).</image:caption>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/gregschoollessons/2017/11/14/drakes-equation</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2018-07-19</lastmod>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5b4ff7c4562fa778928bbc13/1532041164233/astronomy+and+cosmology+thumbnail.png</image:loc>
      <image:title>gregschool-lessons - Drake's Equation and Searching for Life in the Milky Way</image:title>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/5a0cacc4e4966b4ad90d9612/5a0cacc49140b7e76cf5e3b3/1532041164240/20131102_cosmos-episode-2-jovian-life-full%5B1%5D.jpg</image:loc>
      <image:title>gregschool-lessons - Drake's Equation and Searching for Life in the Milky Way</image:title>
      <image:caption>Hunters, Floaters, and Sinkers "This painting speculates about possible forms of life on a Jupiter-like gas giant. Airbrushed water-based acrylic."\(^{[4]}\) Image by Adolf Schaller.</image:caption>
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    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/5a0cacc4e4966b4ad90d9612/5a0cad818165f525ba090942/1532041164243/20131102_cosmos-episode-2-hfs-floater-close-up%5B1%5D.jpg</image:loc>
      <image:title>gregschool-lessons - Drake's Equation and Searching for Life in the Milky Way</image:title>
      <image:caption>A "Floater" from Cosmos, Episode 2 "Part of the larger mural, "Hunters, Floaters, and Sinkers" painted for the series."\(^{[4]}\) Image by Adolf Schaller.</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/5a0cacc4e4966b4ad90d9612/5a0cae0824a6944522e4ff4d/1532041164245/20131102_cosmos-episode-2-hfs-herd-of-floaters%5B1%5D.jpg</image:loc>
      <image:title>gregschool-lessons - Drake's Equation and Searching for Life in the Milky Way</image:title>
      <image:caption>A Lazy Herd of Floaters "An updated digital restoration by Adolf Schaller of detail in his original Hunters, Floaters, Sinkers mural which appeared on Cosmos, Episode 2, which speculates about life in the atmosphere of a gas-giant planet."\(^{[4]}\) Image by Adolf Schaller.</image:caption>
    </image:image>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/5a0cacc4e4966b4ad90d9612/5a0cba949140b72564c34318/1532041164247/20131102_cosmos-episode-2-hfs-a-hunter-close-up%5B1%5D.jpg</image:loc>
      <image:title>gregschool-lessons - Drake's Equation and Searching for Life in the Milky Way</image:title>
      <image:caption>A Hunter "A speculative hunter animal evolved in the atmosphere of a gas-giant planet. Developed for Cosmos, Episode 2."\(^{[4]}\) Image by Adolf Schaller.</image:caption>
    </image:image>
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      <image:title>gregschool-lessons - Drake's Equation and Searching for Life in the Milky Way</image:title>
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      <image:title>gregschool-lessons - Drake's Equation and Searching for Life in the Milky Way</image:title>
      <image:caption>The habitable zone is a range of orbital distances (between an exoplanet and the star it orbits) where the planet is neither too hot nor too cold. This is also sometimes called the Goldilocks zone. In order for a planet to be truly "Earth-like," it must also have a mass 1-2 times that of the Earth, have an atmosphere, and orbit in a stable elliptical orbit that is not too essentric.</image:caption>
    </image:image>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a0e06eaf9619adb9189c6ca/1532041164256/Heic0612b_H%5B1%5D.jpg</image:loc>
      <image:title>gregschool-lessons - Drake's Equation and Searching for Life in the Milky Way</image:title>
      <image:caption>Artist's depiction of an exoplanet crossing our line of sight in front of its home-star.</image:caption>
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      <image:title>gregschool-lessons - Drake's Equation and Searching for Life in the Milky Way</image:title>
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      <image:title>gregschool-lessons - Drake's Equation and Searching for Life in the Milky Way</image:title>
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    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a0cabc20d9297328dca11b9/1532041164238/75C0D4ADBC26486DAD4D19D3CBCEB9E1%5B1%5D.jpg</image:loc>
      <image:title>gregschool-lessons - Drake's Equation and Searching for Life in the Milky Way</image:title>
      <image:caption>"Mr. Spock (Leonard Nimoy), communicating with the Horta through a Vulcan mind meld."\(^{[3]}\)</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a0dc6d64192020bbec9dded/1532041164264/qiao-chen-ship9-3%5B1%5D.jpg</image:loc>
      <image:title>gregschool-lessons - Drake's Equation and Searching for Life in the Milky Way</image:title>
      <image:caption>An artist's depiction of the starship proposed by Project Daedalus.\(^{[5]}\)</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5b4ff822f950b763cde2be1d/1532041164230/</image:loc>
      <image:title>gregschool-lessons - Drake's Equation and Searching for Life in the Milky Way</image:title>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5b4ff7e870a6ad94de39f830/1532041164222/share+astronomy+and+cosmology+img.png</image:loc>
      <image:title>gregschool-lessons - Drake's Equation and Searching for Life in the Milky Way</image:title>
    </image:image>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/5a0e1fd4419202f344874dce/5a0e201f24a694cb082d3777/1532041164261/HT-trappist-1-star-surface-3-jt-170221_4x3_992%5B1%5D.jpg</image:loc>
      <image:title>gregschool-lessons - Drake's Equation and Searching for Life in the Milky Way</image:title>
      <image:caption>Imagine standing on the surface of the exoplanet TRAPPIST-1f. This artist's concept is one interpretation of what it could look like.</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/5a0e1fd4419202f344874dce/5a0e1fd5f9619ae28956d607/1532041164258/proximasurface%5B1%5D.jpg</image:loc>
      <image:title>gregschool-lessons - Drake's Equation and Searching for Life in the Milky Way</image:title>
      <image:caption>"This artist’s impression shows a view of the surface of the planet Proxima b orbiting the red dwarf star Proxima Centauri, the closest star to the solar system. The double star Alpha Centauri AB also appears in the image. Proxima b is a little more massive than the Earth and orbits in the habitable zone around Proxima Centauri, where the temperature is suitable for liquid water to exist on its surface."\(^{[1]}\) https://www.nasa.gov/feature/jpl/eso-discovers-earth-size-planet-in-habitable-zone-of-nearest-star Credits: ESO/M. Kornmesser</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5b4cf448758d463a3bf9d754/1532041164249/pular+planet.png</image:loc>
      <image:title>gregschool-lessons - Drake's Equation and Searching for Life in the Milky Way</image:title>
      <image:caption>Artist's depiction of an exoplanet orbiting a pulsar. Due to the pulsar's radiation, the exoplanet glows.</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a0e1f27419202f344872e8d/1532041164254/Kepler_spacecraft_artist_render_%28crop%29%5B1%5D.jpg</image:loc>
      <image:title>gregschool-lessons - Drake's Equation and Searching for Life in the Milky Way</image:title>
      <image:caption>Artist's depiction of the Kepler space telescope.</image:caption>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/gregschoollessons/2017/6/8/early-earth-history-5mbef</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-08</lastmod>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a037caff9619a0fd0c194f1/1497031483687/</image:loc>
      <image:title>gregschool-lessons - Early Earth History</image:title>
      <image:caption>Click to enlarge - (Source\(^{[2]}\))</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a037caff9619a0fd0c194f5/1497222105007/</image:loc>
      <image:title>gregschool-lessons - Early Earth History</image:title>
      <image:caption>Modern stromatolites in Shark Bay, Western Australia.</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a037caff9619a0fd0c194f3/1497030292093/Archean.png</image:loc>
      <image:title>gregschool-lessons - Early Earth History</image:title>
      <image:caption>Click to enlarge - (Source\(^{[2]}\))</image:caption>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/gregschoollessons/utopia-life-in-the-year-2100</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2019-03-22</lastmod>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/5c228b0d6d2a7362341e50a2/5c228b0d6d2a7362341e50a7/1544408466566/WANDERERS_verona_rupes_03%5B1%5D.jpg</image:loc>
      <image:title>gregschool-lessons - Utopia: Life in the Year 2100</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/5c228b0d6d2a7362341e50a2/5c228b0d6d2a7362341e50a3/1553278214216/WANDERERS_verona_rupes_01%5B1%5D.jpg</image:loc>
      <image:title>gregschool-lessons - Utopia: Life in the Year 2100</image:title>
      <image:caption>“Base jumping off the tallest cliff in the Solar System, located on Uranus' moon Miranda. Uranus itself, along with a few other moons (from the top left to bottom right: Ariel (here on the far side of Uranus), Belinda, Puck and Portia) are seen in the background of the last shot. On Uranus´small moon Miranda lies a monumental cliff wall believed to be the tallest in the Solar System. It is called Verona Rupes. Observations are limited but it is certain that the cliffs rise at least 5 kilometers above the ground below. Maybe even twice as much. This extreme height combined with Miranda´s low gravity (0,018g) would make for a spectacular base-jump. After taking the leap from the top edge you could fall for at least 12 minutes and, with the help of a small rocket to brake your fall toward the bottom, end up landing safely on your feet. Miranda´s close orbit around giant Uranus also makes a magnificent huge cyan ball in the sky. The scene is built mostly in CG, except for the people who are shot live action and composited into the environment, and the foreground cliffs in the first shot which are made from several photos of a place in Norway known as "The Pulpit Rock". For building the landscape I used (amongst others) this satellite photo of Verona Rupes, taken by NASAs Voyager 2 during the flyby of Uranus in 1986. For the color and texture of Uranus I used this photo as reference. Also by Voyager 2, NASA.”\({[4]}\) Source: http://www.erikwernquist.com/wanderers/gallery_verona_rupes.html</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/5c228b0d6d2a7362341e50a2/5c228b0d6d2a7362341e50a5/1544408463612/WANDERERS_verona_rupes_02%5B1%5D.jpg</image:loc>
      <image:title>gregschool-lessons - Utopia: Life in the Year 2100</image:title>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5c299a9221c67c14302feca2/1553278760133/2483808_landscape.jpg</image:loc>
      <image:title>gregschool-lessons - Utopia: Life in the Year 2100</image:title>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5c228b0d6d2a7362341e5098/1544156143514/central+dome+super+computer.jpg</image:loc>
      <image:title>gregschool-lessons - Utopia: Life in the Year 2100</image:title>
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    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5c228b0d6d2a7362341e50aa/1544073254525/26166483_911930292319504_5468126342370460385_n%5B1%5D.jpg</image:loc>
      <image:title>gregschool-lessons - Utopia: Life in the Year 2100</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5c29a899758d46566d036a11/1553278760164/large_-085MyVwIWu7CejYdKdZJ_6R-zaYCURcCPnuQyPhrbA.jpg</image:loc>
      <image:title>gregschool-lessons - Utopia: Life in the Year 2100</image:title>
      <image:caption>”Flipping good ... the Japanese cuisine machine hasn't dropped a pancake yet.”\(^{[3]}\) Image: Huis Ten Bosch/Facebook</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/5c2998ea70a6adae0b2b46b4/5c2998ea575d1f0c317ebfb5/1553278760127/1*ekxLnZoSewL3p7pVUrMEhQ.jpeg</image:loc>
      <image:title>gregschool-lessons - Utopia: Life in the Year 2100</image:title>
      <image:caption>Robert McCall, “The Prologue and the Promise”</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5c228b0d6d2a7362341e509a/1546233660364/11908915_472363736276164_3837059669263559235_o%5B1%5D.jpg</image:loc>
      <image:title>gregschool-lessons - Utopia: Life in the Year 2100</image:title>
      <image:caption>Image (click to enlarge) of lab-grown meat.</image:caption>
    </image:image>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/5c2d216940ec9ae70fd9b9c0/5c2d216903ce64d68f4b5590/1553278760150/The-Venus-Project-Architecture-1-889x500%5B1%5D.jpg</image:loc>
      <image:title>gregschool-lessons - Utopia: Life in the Year 2100</image:title>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/5c2d216940ec9ae70fd9b9c0/5c2d216a4ae2373e5b77f816/1553278760154/The-Venus-Project-Buildings-889x493%5B1%5D.jpg</image:loc>
      <image:title>gregschool-lessons - Utopia: Life in the Year 2100</image:title>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/5c2d216940ec9ae70fd9b9c0/5c2d216a4ae2373e5b77f825/1553278760157/The-Venus-Project-Design-889x500%5B1%5D.jpg</image:loc>
      <image:title>gregschool-lessons - Utopia: Life in the Year 2100</image:title>
    </image:image>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/5c2d216940ec9ae70fd9b9c0/5c2d216c40ec9ae70fd9ba1f/1553278760160/The-Venus-Project-Restaurant-889x544%5B1%5D.jpg</image:loc>
      <image:title>gregschool-lessons - Utopia: Life in the Year 2100</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/5c228b0d6d2a7362341e509c/5c228b0d6d2a7362341e509d/1544408785580/benjamin-parker-fleetovermiranda-render-wip.jpg</image:loc>
      <image:title>gregschool-lessons - Utopia: Life in the Year 2100</image:title>
      <image:caption>“Civilians watch a small fleet orbit around Uranus' moon Miranda.” Credit: https://www.artstation.com/artwork/mqZVx9</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/5c228b0d6d2a7362341e509c/5c228b0d6d2a7362341e509f/1544408724395/benjamin-parker-fleetovermiranda-render-k.jpg</image:loc>
      <image:title>gregschool-lessons - Utopia: Life in the Year 2100</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5c93285f971a1866cb5cdfe2/1553278760138/Diorama%2C_cavemen_-_National_Museum_of_Mongolian_History%5B1%5D.jpg</image:loc>
      <image:title>gregschool-lessons - Utopia: Life in the Year 2100</image:title>
      <image:caption>“A diorama showing Homo erectus, the earliest human species that is known to have controlled fire, from inside the National Museum of Mongolian History in Ulaanbaatar, Mongolia.”\(^{[1]}\)</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5c932b4041920263332ff208/1553278760142/goddardtsiolkovsky%5B1%5D.jpg</image:loc>
      <image:title>gregschool-lessons - Utopia: Life in the Year 2100</image:title>
      <image:caption>Photographs of the two pioneers of rocketry science, Konstantin Tsiolkovsky (left) and Robert Goddard (right).</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5c2ab77d2b6a28bef1af0bf3/1553278760167/42276747_2080497328640659_4459771513339379712_o%5B1%5D.jpg</image:loc>
      <image:title>gregschool-lessons - Utopia: Life in the Year 2100</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5c9520e79140b7f2bbf8d473/1553278760146/Neolithic-revolution-ancient-farmers.jpg</image:loc>
      <image:title>gregschool-lessons - Utopia: Life in the Year 2100</image:title>
      <image:caption>The Neolithic Revolution (which began, independently, in multiple different civilization 10 to 12 thousand years ago) occurred when, for the first time, we humans began to domesticate plants and animals.</image:caption>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5c952de7104c7bde94c94c4e/1553280493180/13312851_249672685423630_2457750922315756964_n.jpg</image:loc>
      <image:title>gregschool-lessons - Utopia: Life in the Year 2100</image:title>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/gregschoollessons/orbital-rings-and-planet-building</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2019-06-01</lastmod>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5b8b4bd10ebbe8ab9ff647d1/1535610747216/med_venus2.jpg</image:loc>
      <image:title>gregschool-lessons - Orbital Rings and Planet Building: Prelude to Colonizing the Solar System</image:title>
      <image:caption>"Terraformed Venus is surrounded by a Dynamic Orbital Ring, mosty constructed from carbon extracted from its original atmosphere."\(^{[24]}\) Image by Steve Bowers.</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/5b8b4bd10ebbe8ab9ff64810/5b8b4bd10ebbe8ab9ff64817/1535487396885/alexey+shirokikh.jpg</image:loc>
      <image:title>gregschool-lessons - Orbital Rings and Planet Building: Prelude to Colonizing the Solar System - Copy of Designer Planet</image:title>
      <image:caption>Artist’s depiction of a designer planet. Artwork by Alexey Shirokikh.</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/5b8b4bd10ebbe8ab9ff64810/5b8b4bd10ebbe8ab9ff64815/1535487329539/Dreamsphere.jpg</image:loc>
      <image:title>gregschool-lessons - Orbital Rings and Planet Building: Prelude to Colonizing the Solar System</image:title>
      <image:caption>“A Dreamsphere, a suprastellar shell completely surrounding a brown dwarf in the Stellar Umma region.” Image from Steve Bowers. Image can also be found on Orion’s Arm.</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/5b8b4bd10ebbe8ab9ff64810/5b8b4bd10ebbe8ab9ff64813/1535352753554/med_suprajupiter.png</image:loc>
      <image:title>gregschool-lessons - Orbital Rings and Planet Building: Prelude to Colonizing the Solar System</image:title>
      <image:caption>“A suprajovian ring suspended above the gas giant Mungo.” Image from Steve Bowers. Image can also be found at Orion’s Arm.</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/5b8b4bd10ebbe8ab9ff64810/5b8b4bd10ebbe8ab9ff64811/1535352742220/Athelan.jpg</image:loc>
      <image:title>gregschool-lessons - Orbital Rings and Planet Building: Prelude to Colonizing the Solar System</image:title>
      <image:caption>“Athelan, a suprashell erected around the gas giant Uranus in the Old Solar System.” Image from Steve Bowers. Image can also be found on Orion’s Arm.</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5b8b4bd10ebbe8ab9ff64789/1535328074668/405001%5B1%5D.jpg</image:loc>
      <image:title>gregschool-lessons - Orbital Rings and Planet Building: Prelude to Colonizing the Solar System</image:title>
      <image:caption>"The High Frontier: Human Colonies in Space is a 1976 book by Gerard K. O'Neill. It envisions large manned habitats in the Earth-Moon system, especially near stable Lagrangian points. Three designs are proposed: Island one (a modified Bernal sphere), Island two (a Stanford torus), and Island 3, two O'Neill cylinders. These would be constructed using raw materials from the lunar surface launched into space using a mass driver and from near-Earth asteroids. The habitats were to spin for simulated gravity and be illuminated and powered by the sun. Solar power satellites were proposed as a possible industry to support the habitats. The book won the 1977 Phi Beta Kappa Award in Science."\(^{[9]}\)</image:caption>
    </image:image>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/5b8b4bd10ebbe8ab9ff647fb/5b8b4bd10ebbe8ab9ff647fc/1535354345044/1pAZfg0WDtvCEBWpd997Kr9YV49FlqTHnQMz55sxqPc.jpg</image:loc>
      <image:title>gregschool-lessons - Orbital Rings and Planet Building: Prelude to Colonizing the Solar System</image:title>
      <image:caption>Artist’s depiction of a Matrioshka brain. Image retrieved from: https://www.reddit.com/r/Futurology/comments/zu399/this_day_will_come_the_matrioshka_brain/</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/5b8b4bd10ebbe8ab9ff6481c/5b8b4bd10ebbe8ab9ff6481d/1536720334659/jeremy-jozwik-ia-coljupiter-comp2-raw-jpeg-0214.jpg</image:loc>
      <image:title>gregschool-lessons - Orbital Rings and Planet Building: Prelude to Colonizing the Solar System - Fusion Candles</image:title>
      <image:caption>Artist's impression of Fusion Candles which could be used to move Jupiter and its moons across interstellar or even intergalactic space and away from our solar system. Spaceship Jupiter! Artwork by Jeremy Jozwik from Artstation.</image:caption>
    </image:image>
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      <image:title>gregschool-lessons - Orbital Rings and Planet Building: Prelude to Colonizing the Solar System</image:title>
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      <image:title>gregschool-lessons - Orbital Rings and Planet Building: Prelude to Colonizing the Solar System - Matrioshka Brain</image:title>
      <image:caption>Artist's impression of a Matrioshka Brain. Artwork by Jakub Grygier who is also a member of the SFIA production team.</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/5b8b4bd10ebbe8ab9ff647a3/5b8b4bd10ebbe8ab9ff647aa/1535329173143/neil-blevins-megastructures-7-star-lifter-color-sketch.jpg</image:loc>
      <image:title>gregschool-lessons - Orbital Rings and Planet Building: Prelude to Colonizing the Solar System</image:title>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/5b8b4bd10ebbe8ab9ff647a3/5b8b4bd10ebbe8ab9ff647a4/1535329245230/neil-blevins-megastructures-7-star-lifter-3d-sketch.jpg</image:loc>
      <image:title>gregschool-lessons - Orbital Rings and Planet Building: Prelude to Colonizing the Solar System</image:title>
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      <image:title>gregschool-lessons - Orbital Rings and Planet Building: Prelude to Colonizing the Solar System</image:title>
      <image:caption>"The inner and outer static orbital rings around Bronx are linked to a central geostationary ring by carbon nanotube cables. The inner ring is only 265km above the clouds, while the outer ring is 75,600km from the planet's core."\(^{[19]}\) Image from Steve Bowers.</image:caption>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/5b8b4bd10ebbe8ab9ff64769/5b8b4bd10ebbe8ab9ff6476a/1535825798962/sergio-botero-tflp-damocles-comp-4-v1-web.jpg</image:loc>
      <image:title>gregschool-lessons - Orbital Rings and Planet Building: Prelude to Colonizing the Solar System</image:title>
      <image:caption>"Damocles is a large space port and elevator hub with stations fixed on [E]arth, located in an enormous, peaceful and very prosperous city, in a not-so-distant future.”\(^{[2]}\) In the year 2117 the most economical way to send people and cargo to outer space is using a space elevator. It’s not the quickest option but a very practical and effective one. Just like other similar Orbitowers placed on the Equator, the Damocles elevator hub provides this service. Space freight elevators are crucial to carry large components of interplanetary and the earlier interstellar vehicles into orbit, so they can be assembled in space instead of being launched by rockets. Autonomous trucks and cars arrive at the base’s ground to take passengers and cargo to the space elevator cabs. Flying vehicles land on the pads. The building itself is headquarters for many logistics companies, there are some offices and a hotel."\(^{[2]}\) Artwork by Sergio Botero at Artstation.\(^{[2]}\)</image:caption>
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      <image:title>gregschool-lessons - Orbital Rings and Planet Building: Prelude to Colonizing the Solar System</image:title>
      <image:caption>Artist's depiction of solar panels attached to a space elevator.</image:caption>
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      <image:title>gregschool-lessons - Orbital Rings and Planet Building: Prelude to Colonizing the Solar System</image:title>
      <image:caption>Artist's depiction of a Model 3 O'Neil cylinder which would be capable of supporting millions of a people, a complete biosphere, and all of the Earth's natural habitats. An O'Neil cylinder could also be used as an arc ship (sometimes also called a generation ship) to travel to other stars or galaxies. Image by Glenn Clovis from Artstation.\(^{[11]}\)</image:caption>
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      <image:title>gregschool-lessons - Orbital Rings and Planet Building: Prelude to Colonizing the Solar System</image:title>
      <image:caption>Artist’s depiction of atlas towers connecting two separate shells in a shell world. Image credit: https://www.deviantart.com/johnmalcolm1970/art/Shell-World-114062545</image:caption>
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      <image:title>gregschool-lessons - Orbital Rings and Planet Building: Prelude to Colonizing the Solar System</image:title>
      <image:caption>"Arthur C. Clarke’s 3001: The Final Odyssey features an orbital ring held aloft by four enormous inhabitable towers (assumed successors to space elevators) at the Equator."\(^{[15]}\) For book summary, see: https://en.wikipedia.org/wiki/3001:_The_Final_Odyssey</image:caption>
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      <image:caption>Interior of an O'Neill cylinder\(^{[10]}\)</image:caption>
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      <image:caption>Solar eclipse inside an O'Neill cylinder\(^{[10]}\)</image:caption>
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      <image:title>gregschool-lessons - Orbital Rings and Planet Building: Prelude to Colonizing the Solar System</image:title>
      <image:caption>Interior of an O'Neill cylinder\(^{[10]}\)</image:caption>
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      <image:caption>O'Neill cylinders\(^{[10]}\)</image:caption>
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      <image:title>gregschool-lessons - Orbital Rings and Planet Building: Prelude to Colonizing the Solar System</image:title>
      <image:caption>Artist’s depiction of an orbital ring.</image:caption>
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      <image:title>gregschool-lessons - Orbital Rings and Planet Building: Prelude to Colonizing the Solar System</image:title>
      <image:caption>Artist’s depiction of hoop worlds (also known as ring worlds). These megastructures can be built by building many adjacent orbital rings next to each other, side by side, and laying a surface down over those orbital rings. Image retrieved from https://www.iamag.co/espen-olsen-saetervik/espen-saetervik-rings/</image:caption>
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      <image:title>gregschool-lessons - Orbital Rings and Planet Building: Prelude to Colonizing the Solar System</image:title>
      <image:caption>Animation of a sheet of pure graphene rolled up into a carbon nanotube. Credit: https://commons.wikimedia.org/wiki/File:Kohlenstoffnanoroehre_Animation.gif</image:caption>
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      <image:caption>Artist's depiction of the interior of a Stanford torus. Painted by Donald E. Davis.</image:caption>
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      <image:title>gregschool-lessons - Orbital Rings and Planet Building: Prelude to Colonizing the Solar System</image:title>
      <image:caption>Image above portrays Nikola Tesla, the famous inventor who first conceived of the notion of orbital rings in the 1870s shortly after recovering from malaria.</image:caption>
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      <image:caption>"Full cities could hang from the top of the shell that holds in the newly terraformed world's atmosphere."\(^{[27]}\) Image uploaded Oct. 7, 2013. Credit: Ken Roy/Tennessee Valley Interstellar Workshop</image:caption>
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      <image:caption>Artist's conception of the Kepler Space Telescope.</image:caption>
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      <image:title>gregschool-lessons - Orbital Rings and Planet Building: Prelude to Colonizing the Solar System</image:title>
      <image:caption>Larry Niven's Ringworld. Image credit: https://bargainbin4u.wordpress.com/2008/07/14/ringworld-by-larry-niven/</image:caption>
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      <image:title>gregschool-lessons - Orbital Rings and Planet Building: Prelude to Colonizing the Solar System</image:title>
      <image:caption>Artist’s depiction of a ring world. Image credit: https://www.deviantart.com/tomislavtikulin/art/Ringworld-Engineers-665659952</image:caption>
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      <image:title>gregschool-lessons - Orbital Rings and Planet Building: Prelude to Colonizing the Solar System</image:title>
      <image:caption>Artist’s depiction of a ring world. Image credit: https://www.deviantart.com/julian-faylona/art/Halcyon-Days-423868574</image:caption>
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      <image:caption>"An engineer suggests building a roof over a small planet so that Earthlike conditions could be maintained."\(^{[26]}\) The Shell World could be used to maintain Earth-like conditions on the surface of an alien planet or moon; hanging cities could be suspended from the interior wall of the shell world; or the outer-surface of the Shell World could be engineered to closely resemble the Earth. Some combination of all of the above could be possible, albeit only to a certain extent. Credit: by Karl Tate, Infographics Artist</image:caption>
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      <image:title>gregschool-lessons - Orbital Rings and Planet Building: Prelude to Colonizing the Solar System</image:title>
      <image:caption>Artist’s depiction of an orbital ring which appeared in Issue 7 of the magazine, All About Space. Image by Adrian Mann.\(^{[18]}\)</image:caption>
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      <image:caption>Public Area "The public area would be assembled into a complex structure in the form of a truncated octahedron. It would have a great room consisting of a lobby, restaurant, entertainment room, and other spaces where people could enjoy a dining experience, sports, and a variety of amusements under low-gravity conditions."\(^{[4}\)</image:caption>
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      <image:caption>Guest Room Module "A module with 104 individual rooms, including 64 guest rooms, would be arranged on a ring that is 140 meters in diameter. The ring would generate an artificial gravity field of 0.7 G by rotating around three times per minute, so people could relax almost in the same manner as on earth."\(^{[4]}\)</image:caption>
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      <image:title>gregschool-lessons - Orbital Rings and Planet Building: Prelude to Colonizing the Solar System</image:title>
      <image:caption>"Since ancient times, people have always dreamed of going to space. Only astronauts have been able to go until now, but progress has been made on efforts to enable even private citizens to experience space, and space travel is finally about to become an industry. Shimizu foresaw the era of space travel early on, and has proposed a space hotel concept."\(^{[4]}\)</image:caption>
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      <image:title>gregschool-lessons - Orbital Rings and Planet Building: Prelude to Colonizing the Solar System</image:title>
      <image:caption>“Two hubs that can connect to create a temporary Warp Lane in your system The Warp Lane Hub can be connected to another Hub for one day, for a fixed Hydrogen cost. Once connected, ships can travel between the two end points instantly and without consuming Hydrogen.”\(^{[31]}\) Image credit: https://www.deviantart.com/gabrielbstiernstrom/art/Hades-Star-Warp-Lane-Hub-680163129</image:caption>
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      <image:title>gregschool-lessons - Orbital Rings and Planet Building: Prelude to Colonizing the Solar System</image:title>
      <image:caption>Artist’s scifi depiction of a galactic empire using portals to travel across space.\(^{[30]}\) Image credit: https://www.deviantart.com/lorddoomhammer/art/Galactic-Network-594726702</image:caption>
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      <image:title>gregschool-lessons - Orbital Rings and Planet Building: Prelude to Colonizing the Solar System</image:title>
      <image:caption>Artist’s depiction of an O’Neil cylinder. Artwork by Bruno Xavier.\(^{[12]}\)</image:caption>
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      <image:title>gregschool-lessons - Orbital Rings and Planet Building: Prelude to Colonizing the Solar System - Anywhere in the World in Under an Hour</image:title>
      <image:caption>Elon Musk proposed using BFR rockets (see image above) as a planetary transportation system which could get you anywhere in the world in under one hour. Image courtesy of Space X.</image:caption>
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      <image:title>gregschool-lessons - Orbital Rings and Planet Building: Prelude to Colonizing the Solar System - Lunar Mass Driver</image:title>
      <image:caption>Artist’s depiction of a lunar mass driver. The physicist Gerard K. O’Neil imagined using this device to electromagnetically launch lunar material into space for the purpose of being using to construct artificial space habitats for human residence and to move most industry off the Earth and into space. Image courtesy of NASA.</image:caption>
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      <image:title>gregschool-lessons - Orbital Rings and Planet Building: Prelude to Colonizing the Solar System - Lunar Mass Driver</image:title>
      <image:caption>Artist’s depiction of a Lunar mass driver. Artwork by Jay Wong.</image:caption>
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      <image:title>gregschool-lessons - Orbital Rings and Planet Building: Prelude to Colonizing the Solar System</image:title>
      <image:caption>The concept of the Ocean Spiral was first unveiled by Shimizu Corporation, in conjunction with Tokyo University and Japan Agency for Marine-Earth Science and Technology, in 2014. The company excepts it to take 5 years to build an Ocean Spiral. The company expects the project to cost ¥3 trillion (approximately £20 billion). The company claims it could be ready for human habitation by 2030. Learn more by reading the article, Ocean Spiral is a conceptual city proposed beneath the surface of the ocean.</image:caption>
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      <image:title>gregschool-lessons - Orbital Rings and Planet Building: Prelude to Colonizing the Solar System</image:title>
      <image:caption>Final Frontier Voyager (2007), George Grie. Óleo sobre lienzo.\(^{[13]}\)Credit: https://commons.wikimedia.org/wiki/File:Final-Frontier.jpg</image:caption>
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      <image:title>gregschool-lessons - Orbital Rings and Planet Building: Prelude to Colonizing the Solar System</image:title>
      <image:caption>Illustration showing the rocky, icy, metallic cores of the four Jovian planets. Credit: NASA/Lunar and Planetary Institute Retrieved from: https://solarsystem.nasa.gov/resources/677/gas-giant-interiors-2003/</image:caption>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5b8b4bd10ebbe8ab9ff64820/1535500914749/main-qimg-c723f245065082e7f3de09cd458d893e%5B1%5D.png</image:loc>
      <image:title>gregschool-lessons - Orbital Rings and Planet Building: Prelude to Colonizing the Solar System</image:title>
      <image:caption>The infographic above shows the differences between a Type I (or K1), a Type II (or K2), and a Type III (or K3) civilization.</image:caption>
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      <image:title>gregschool-lessons - Orbital Rings and Planet Building: Prelude to Colonizing the Solar System</image:title>
      <image:caption>Cut-away view of the interior of a Standford Torus. Image courtesy of NASA Ames Research Center.</image:caption>
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      <image:title>gregschool-lessons - Orbital Rings and Planet Building: Prelude to Colonizing the Solar System - Copy of Space Elevator</image:title>
      <image:caption>Depiction of a space elevator. Artwork by Glenn Clovis at Artstation.\(^{[6]}\)</image:caption>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/5b8b4bd10ebbe8ab9ff64783/5b8b4bd10ebbe8ab9ff64786/1535827243822/seattle_space_elevator_observatory_by_alterbr33d-d5j8j2p-750x375%402x%5B1%5D.png</image:loc>
      <image:title>gregschool-lessons - Orbital Rings and Planet Building: Prelude to Colonizing the Solar System - Copy of Space Elevator</image:title>
      <image:caption>Depiction of a space elevator.\(^{[7]}\) Artwork retrieved from: http://prospective-tourisme.com/index.php/2017/08/10/entretien-laurent-queige-directeur-welcome-city-lab/</image:caption>
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      <image:title>gregschool-lessons - Orbital Rings and Planet Building: Prelude to Colonizing the Solar System</image:title>
      <image:caption>Artist's illustration of a hypothetical ocean planet with two natural satellites. Image credit: https://commons.wikimedia.org/wiki/File:Oceanplanet_lucianomendez.JPG</image:caption>
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      <image:caption />
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      <image:title>gregschool-lessons - Orbital Rings and Planet Building: Prelude to Colonizing the Solar System</image:title>
      <image:caption>Artists depictions of gas giant refineries on two different gas giant planets. The gas giants depicted in these images are suspended by large blimps which hold a lifting gas. But it would also be possible, as we discuss in this article, to attach those gas giant refineries to the ceiling of a shell world or orbital ring. Artwork by Neil Blevins (top) and Jeremy Jozwik (bottom) at Artstation.</image:caption>
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      <image:title>gregschool-lessons - Orbital Rings and Planet Building: Prelude to Colonizing the Solar System</image:title>
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  </url>
  <url>
    <loc>https://www.gregschool.org/gregschoollessons/2017/10/30/gravitational-force-exerted-by-a-sphere-rdyjt-dcss2</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2018-09-14</lastmod>
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      <image:title>gregschool-lessons - Gravitational Force Exerted by a Sphere</image:title>
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      <image:title>gregschool-lessons - Gravitational Force Exerted by a Sphere</image:title>
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      <image:title>gregschool-lessons - Gravitational Force Exerted by a Sphere</image:title>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5b9c0ca1758d46af9e69fa2f/1523204866420/sphere+force.png</image:loc>
      <image:title>gregschool-lessons - Gravitational Force Exerted by a Sphere</image:title>
      <image:caption>Figure 1: A shell can be subdivided into many very skinny rings. Anyone of these rings can be represented by the ring \(QRR_1Q_1\) illustrated above. Image credit\(^{[1]}\).</image:caption>
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      <image:title>gregschool-lessons - Gravitational Force Exerted by a Sphere</image:title>
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      <image:title>gregschool-lessons - Gravitational Force Exerted by a Sphere</image:title>
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      <image:title>gregschool-lessons - Gravitational Force Exerted by a Sphere</image:title>
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  </url>
  <url>
    <loc>https://www.gregschool.org/gregschoollessons/technological-revolutions</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2019-03-23</lastmod>
    <image:image>
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      <image:title>gregschool-lessons - Technological Revolutions</image:title>
      <image:caption>“Smithsonian scientists and their Chinese colleagues found this and other handaxes in the same sediment layer with tektites, small rocks that formed during a meteor impact 803,000 years ago. Since the handaxes and tektites were in the same layer, both are the same age. Early humans must have moved into the area right after the impact. They may have made the handaxes from rocks that were exposed when forests burned.”\(^{[1]}\) Image Credit: James Di Loreto, &amp; Donald H. Hurlbert, Smithsonian Institution</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5c2fc9862b6a28ff22bd5c66/1553287768116/Meissner_effect_p1390048%5B1%5D.jpg</image:loc>
      <image:title>gregschool-lessons - Technological Revolutions</image:title>
      <image:caption>“A magnet levitating above a high-temperature superconductor, cooled with liquid nitrogen. Persistent electric current flows on the surface of the superconductor, acting to exclude the magnetic field of the magnet (Faraday's law of induction). This current effectively forms an electromagnet that repels the magnet.” Image source: https://en.wikipedia.org/wiki/Superconductivity#/media/File:Meissner_effect_p1390048.jpg</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5c2fba140e2e72f08ab291af/1553287768105/Newcomens_Dampfmaschine_aus_Meyers_1890%5B1%5D.png</image:loc>
      <image:title>gregschool-lessons - Technological Revolutions</image:title>
      <image:caption>“Newcomen's steam-powered atmospheric engine was the first practical piston steam engine. Subsequent steam engines were to power the Industrial Revolution.”\(^{[7]}\)</image:caption>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/5c2fa74888251b069d1ca774/5c2fa748758d46fb365b0a9e/1553287768088/392448062_orig%5B1%5D.jpg</image:loc>
      <image:title>gregschool-lessons - Technological Revolutions</image:title>
      <image:caption>Artist’s depiction of nanobots patroling the human bloodstream. Image retrieved from: https://www.cnet.com/news/nanobots-can-now-swarm-like-fish-to-perform-complex-medical-tasks/</image:caption>
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    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/5c954d8a9b747a5c37086ff1/5c954e0a71c10b6eca224078/1553288732301/nanotechn.jpg</image:loc>
      <image:title>gregschool-lessons - Technological Revolutions</image:title>
      <image:caption>Image source : Google</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5c2d25e688251be3e0ed5117/1553287768119/stock-photo-concept-of-magnetic-levitation-train-moving-on-the-sky-way-in-vacuum-tunnel-across-the-city-modern-755107045%5B1%5D.jpg</image:loc>
      <image:title>gregschool-lessons - Technological Revolutions</image:title>
      <image:caption>The image above portrays how large buildings (which could be arcologies that people live in) could be connected by maglev trains operating within evacuated tunnels. Image Credit: https://www.shutterstock.com/image-illustration/concept-magnetic-levitation-train-moving-on-755107045</image:caption>
    </image:image>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5c2fb3ad70a6adad0a563e6a/1553287768096/</image:loc>
      <image:title>gregschool-lessons - Technological Revolutions</image:title>
      <image:caption>“The Principia states Newton's laws of motion, forming the foundation of classical mechanics; Newton's law of universal gravitation; and a derivation of Kepler's laws of planetary motion (which Kepler first obtained empirically). The Principia is considered one of the most important works in the history of science.”\(^{[5]}\)</image:caption>
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    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5c2fb74fc2241b2a8d20d99d/1553287768103/Joule%27s_Apparatus_%28Harper%27s_Scan%29%5B1%5D.png</image:loc>
      <image:title>gregschool-lessons - Technological Revolutions</image:title>
      <image:caption>“Engraving of James Joule's apparatus for measuring the mechanical equivalent of heat, in which altitude potential energy from the weight on the right is converted into heat at the left, through stirring of water.”\(^{[7]}\)</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5c2faeb4758d463079f878eb/1553287768093/shopping%5B2%5D.jpg</image:loc>
      <image:title>gregschool-lessons - Technological Revolutions</image:title>
      <image:caption>In the book, Life 3.0, the cosmologist and AI researcher Max Tegmark explores the implications of AI and robotics.</image:caption>
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    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5c2fb5104ae2370b648878aa/1553287768099/Newtons_laws_in_latin%5B1%5D.jpg</image:loc>
      <image:title>gregschool-lessons - Technological Revolutions</image:title>
      <image:caption>“Newton's First and Second laws, in Latin, from the original 1687 Principia Mathematica”\(^{[6]}\)</image:caption>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5c2e93d9032be47ea48ca0fc/1553287768076/Life-expectancy-GDP-capita.png</image:loc>
      <image:title>gregschool-lessons - Technological Revolutions</image:title>
      <image:caption>This graph illustrates the increase in standards of living and life expectancy that occurred during the time of the first two industrial revolutions.\(^{[3]}\)</image:caption>
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    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/5c2fbb690e2e72f08ab2aba3/5c2fbb6c2b6a28c2e447c3a4/1553287768109/Bane-Boon-1280x640%5B1%5D.jpg</image:loc>
      <image:title>gregschool-lessons - Technological Revolutions</image:title>
      <image:caption>Image retrieved from: https://iconshots.com/concept/the-future-of-technology-should-we-be-worried/</image:caption>
    </image:image>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5c2e963d21c67c6b2564ed53/1553287768079/Ending_Aging%5B1%5D.jpg</image:loc>
      <image:title>gregschool-lessons - Technological Revolutions</image:title>
      <image:caption>Credit: https://en.wikipedia.org/wiki/File:Ending_Aging.jpg</image:caption>
    </image:image>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5c2e8a740ebbe8aa628a113f/1553287768125/stock-photo-the-train-moving-on-the-overpass-and-the-city-on-the-water-concept-of-modern-transport-futuristic-769589683%5B1%5D.jpg</image:loc>
      <image:title>gregschool-lessons - Technological Revolutions</image:title>
      <image:caption>Arcologies on the surface of the sea could be connected by maglev transportation systems. As we discuss in the article, How to Colonize the Earth?, these sea-steading towers would extend within the depths of the oceans; the cities underneath the sea surface could also be connected by maglev monorail systems. Image Credit: https://www.shutterstock.com/image-illustration/train-moving-on-overpass-city-water-769589683?src=l4eCjvmchovnXUJuJH_WrQ-1-29</image:caption>
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      <image:title>gregschool-lessons - Technological Revolutions</image:title>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/5c2fa5480e2e728e6b090183/5c2fa549cd8366903646c7f0/1553287768082/Artificial-Intelligence-2%5B1%5D.jpg</image:loc>
      <image:title>gregschool-lessons - Technological Revolutions</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5c2fa63b0ebbe85c974e933b/1553287768085/Moore%27s_Law_Transistor_Count_1971-2016%5B1%5D.png</image:loc>
      <image:title>gregschool-lessons - Technological Revolutions</image:title>
      <image:caption>A plot of CPU transistor counts against dates of introduction. Source URL: https://commons.wikimedia.org/wiki/File:Moore%27s_Law_Transistor_Count_1971-2016.png</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5c2e92944ae23708582cc0a0/1553287768074/Maler_der_Grabkammer_des_Sennudem_001.jpg</image:loc>
      <image:title>gregschool-lessons - Technological Revolutions</image:title>
      <image:caption>“Ploughing with a yoke of horned cattle in Ancient Egypt. Painting from the burial chamber of Sennedjem, c. 1200 BC.”\(^{[2]}\)</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5c2fc6fe032be405050dfba3/1553287768113/superconductors.png</image:loc>
      <image:title>gregschool-lessons - Technological Revolutions</image:title>
      <image:caption>The following graph reflects the empirical fact that as time has progressed, we have achieved superconductivity at higher and higher temperatures. Credit: Pia Jensen Ray</image:caption>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/gregschoollessons/spaceship-comets-and-highways-through-space</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2019-02-28</lastmod>
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      <image:title>gregschool-lessons - Spaceship Comets and Highways Through Space</image:title>
      <image:caption>“Each of the hexagons in this figure represents one of the mirror farms shown in [previous image]. The dots are schematic representations of the habitats occupied by each twent-five-member “band.” in reality the habitats would probably be much too small to be seen on this scale.”\(^{[37]}\)</image:caption>
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      <image:title>gregschool-lessons - Spaceship Comets and Highways Through Space - Trip to Alpha Centauri using a Starshot Probe</image:title>
      <image:caption>SCMP Graphic: Dennis Wong, Dang Elland Sources: Universe Today, SIMBAD Dacabase, SCMP research</image:caption>
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      <image:title>gregschool-lessons - Spaceship Comets and Highways Through Space</image:title>
      <image:caption>“This artist's concept puts solar system distances in perspective. The scale bar is in astronomical units, with each set distance beyond 1 AU representing 10 times the previous distance. One AU is the distance from the Sun to the Earth, which is about 93 million miles or 150 million kilometers. Neptune, the most distant planet from the Sun, is about 30 AU.”\(^{[4]}\) Image Credit: NASA/JPL-Caltech</image:caption>
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      <image:title>gregschool-lessons - Spaceship Comets and Highways Through Space</image:title>
      <image:caption>Robert Zubrin’s book, Entering Space, covers topics ranging from colonizing Mars and the solar system and explores the feasibility of interstellar travel with known physics.\(^{[1]}\)</image:caption>
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      <image:title>gregschool-lessons - Spaceship Comets and Highways Through Space - Asteroid Mining Station</image:title>
      <image:caption>Artist’s depicion of a colonized asteroid. Artwork by Bas Ruhe from Artstation.</image:caption>
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      <image:title>gregschool-lessons - Spaceship Comets and Highways Through Space</image:title>
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      <image:title>gregschool-lessons - Spaceship Comets and Highways Through Space</image:title>
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      <image:title>gregschool-lessons - Spaceship Comets and Highways Through Space</image:title>
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      <image:title>gregschool-lessons - Spaceship Comets and Highways Through Space</image:title>
      <image:caption>The power requirements of buried human habitats and propellant production plants could be met by the widely spaced solar power panels shown above. Image: anna.j.nesterova@gmail.com</image:caption>
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      <image:title>gregschool-lessons - Spaceship Comets and Highways Through Space - Death Star</image:title>
      <image:caption>Artist’s depiction of a death star. By building a shell world of the kind described by the scientist Paul Birch around a faint dead star (i.e. a brown dwarf), the faint radiation which that star gives off could be collected and used to power a gigantic laser mounted on the surface of a shell world. Thus, as far fetched as the idea might seem, it isn’t totally implausable. Image retrieved from: Artist’s depiction of a comet being used as a spaceship. Image retrieved from: http://earth-chronicles.ru/news/2014-04-21-63940</image:caption>
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      <image:title>gregschool-lessons - Spaceship Comets and Highways Through Space</image:title>
      <image:caption>“Conceptual model of a growing and evolving asteroid starship. The image of comet 67P by ESA is used as a placeholder for a large asteroid.”\(^{[6]}\) Composite image by Francisco Muñoz and Anton Dobrevski</image:caption>
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      <image:title>gregschool-lessons - Spaceship Comets and Highways Through Space - Spaceship Asteroid</image:title>
      <image:caption>“The concept of turning an asteroid into a spacecraft is not entirely new: conceptual designer Bryan Versteeg has been working with the Mars One Team to imagine how we could use large asteroids for mining, transportation and habitat.”\(^{[2]}\) Credit: http://www.spacehabs.com/</image:caption>
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      <image:title>gregschool-lessons - Spaceship Comets and Highways Through Space</image:title>
      <image:caption>Image Source: https://i4is.org/wp-content/uploads/2018/05/Principium21.pdf</image:caption>
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      <image:title>gregschool-lessons - Spaceship Comets and Highways Through Space</image:title>
      <image:caption>In Carl Sagan’s book, Pale Blue Dot, he talked about the possibility of interstellar human communities living in comets in the Kuiper belt, the Oort cloud, and beyond.</image:caption>
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      <image:title>gregschool-lessons - Spaceship Comets and Highways Through Space</image:title>
      <image:caption>Credit: Nils Faber &amp; Angelo Vermeulen</image:caption>
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      <image:title>gregschool-lessons - Spaceship Comets and Highways Through Space</image:title>
      <image:caption>The map above shows the migration patterns and timeline of the Polynesians who traveled from Asia to America by hopping from one tiny archipelago to another. Our descendants who travel from the Earth to the exoplanet Proxima B might adopt an analogous strategy by hopping from one comet to another until they reach their final destination. Image retrieved from: https://teara.govt.nz/en/map/1449/map-of-pacific-migrations</image:caption>
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      <image:title>gregschool-lessons - Spaceship Comets and Highways Through Space</image:title>
      <image:caption>Using a nuclear reactor to fuse together deuterium and helium-3 would generate a lot of energy; that energy would be transferred to a shock absorber on the rear of a spaceship which would give the spaceship thrust thereby causing it to accelerate. Image retrieved from: https://science.howstuffworks.com/environmental/green-science/energy-from-space.htm</image:caption>
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      <image:title>gregschool-lessons - Spaceship Comets and Highways Through Space</image:title>
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      <image:title>gregschool-lessons - Spaceship Comets and Highways Through Space</image:title>
      <image:caption>Infographics represent a visual explanation of the so-called terrariums discussed in Kim Stanley Robinsons, 2312. Also, there is a slight error in the last infographic: the asteroid does not spin, rather a cylinder inside of the hollowed out asteroid is the thing which is actually spinning. Infographics created by Pablo Defendini. Infographics retrieved from: http://www.defendini.com/2312.html</image:caption>
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      <image:title>gregschool-lessons - Spaceship Comets and Highways Through Space</image:title>
      <image:caption>Concept art for DSI's "Harvestor" craft. Credit and Copyright: Bryan Versteeg / DSI.</image:caption>
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      <image:title>gregschool-lessons - Spaceship Comets and Highways Through Space</image:title>
      <image:caption>Asteroid settlement concept. Credit and Copyright: Bryan Versteeg / DSI.</image:caption>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/5b9994110e2e7257287e7241/5b9994110e2e7257287e7242/1537229057732/maxresdefault.jpg</image:loc>
      <image:title>gregschool-lessons - Spaceship Comets and Highways Through Space - Starshot Probe</image:title>
      <image:caption>Depiction of a Starshot probe being accellerated by Earth-based lasers. Credit: Breakthrough Starshot</image:caption>
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      <image:title>gregschool-lessons - Spaceship Comets and Highways Through Space</image:title>
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      <image:title>gregschool-lessons - Spaceship Comets and Highways Through Space</image:title>
      <image:caption>“Here is a new montage showing the base of the space elevator on the tented town called "Sheffield", built on the summit of Pavonis Mons volcano (see Red Mars). The cable is supposed to be 10m thick, which means here that Sheffield city is very big here, at a large level of development. On the foreground, you can see colored urban lights. I imagine the main entry to the planet's surface would be like a rich and welcoming show for new settlers. I also imagine the tent' skin would be blue, to balance the red and grey landscape.”\(^{[59]}\)</image:caption>
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      <image:title>gregschool-lessons - Spaceship Comets and Highways Through Space</image:title>
      <image:caption>Artist’s impression of a space elevator connecting to the domed over city, Sheifeild, located on Pvonic Mons in Kim Robinson’s Mars trilogy. Images retrieved from: http://davinci-marsdesign.blogspot.com/2012/04/sheffield-and-space-elevator.html</image:caption>
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      <image:title>gregschool-lessons - Spaceship Comets and Highways Through Space</image:title>
      <image:caption>“This hexagonal array of starlight mirrors might support a co-living group of twenty-five adults and children. Each of the mirrors is about the size of the continental United States, and the entire mirror “farm” is about 30,000 kilometers across.”\(^{[37]}\)</image:caption>
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      <image:title>gregschool-lessons - Spaceship Comets and Highways Through Space</image:title>
      <image:caption>Image of the Saturn V rocket launching to space. Image courtesy of NASA.</image:caption>
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      <image:title>gregschool-lessons - Spaceship Comets and Highways Through Space - Interstellar Spaceship</image:title>
      <image:caption>Artist’s depiction of an interstellar spaceship accellerated by laser beams. Artwork by Jakub Grygier from Artstation.</image:caption>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5bb65e1b9140b778c67d3963/1551045244895/photosynthesis-process-2.jpg</image:loc>
      <image:title>gregschool-lessons - Spaceship Comets and Highways Through Space</image:title>
      <image:caption>The infographic above shows how plants, via the process of photosynethesis, use light (sunlight or artificial light), carbon dioxide and water to produce breathable oxygen.</image:caption>
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  </url>
  <url>
    <loc>https://www.gregschool.org/gregschoollessons/2018/5/23/preliminary-interstellar-missions-prelude-to-the-stars</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2019-02-24</lastmod>
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      <image:title>gregschool-lessons - Preliminary Interstellar Missions: Prelude to the Stars</image:title>
      <image:caption>“This Hubble Space Telescope image of Mars shows details 20 to 30 miles across. A solar gravitational lens telescope would get even sharper views of exoplanets up to 100 light years away.”\(^{[4]}\) (STScI/AURA), J. Bell (ASU), and M. Wolff) Source URL: https://www.airspacemag.com/daily-planet/ultimate-space-telescope-would-use-sun-lens-180962499/</image:caption>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5c2c135a40ec9ab2ea4478e5/1549254809129/NASA-WhatBiosignaturesDoesLifeProduce-20180625%5B1%5D.jpg</image:loc>
      <image:title>gregschool-lessons - Preliminary Interstellar Missions: Prelude to the Stars</image:title>
      <image:caption>The combination of certain molecules and the absence of certain molecules in an exoplanet’s atmosphere is only likely if life is inhabited on that world: such combinations are called disequilibrium mixtures. As the light emitted from a star passes through an exoplanet’s atmosphere, the molecules in that exoplanet’s atmosphere absorb only certain wavelengths. Given which wavelengths were absorbed, we can determine whether or not disequilibrium mixtures are present in that exoplanet’s atmosphere and, consequently, assess the likelihood that extraterrestrial life inhabits that world. NASA/Aaron Gronsta</image:caption>
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      <image:title>gregschool-lessons - Preliminary Interstellar Missions: Prelude to the Stars</image:title>
      <image:caption>Diagram of the evolution of atmospheric oxygen concentration during the history of the planet. © Ido, Pierre Sans-Jofre</image:caption>
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    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5c2aabb270a6adae0b34a7d6/1549254809137/Welcome_to_the_Universe_by_Neil_deGrasse_Tyson%3B_book_cover.jpg</image:loc>
      <image:title>gregschool-lessons - Preliminary Interstellar Missions: Prelude to the Stars</image:title>
      <image:caption>Welcome to the Universe: An Astrophysical Tour is a popular science book by Neil deGrasse Tyson, Michael A. Strauss, and J. Richard Gott, based on an introductory astrophysics course they co-taught at Princeton University. The book was published by the Princeton University Press on September 20, 2016.\(^{[6]}\)</image:caption>
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      <image:title>gregschool-lessons - Preliminary Interstellar Missions: Prelude to the Stars</image:title>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/5ba46a530d9297e050b0b8cc/5ba46a53f4e1fcbe9171f5b1/1549254809127/1280px-Artist%27s_impression_of_the_planet_Ross_128_b%5B1%5D.jpg</image:loc>
      <image:title>gregschool-lessons - Preliminary Interstellar Missions: Prelude to the Stars</image:title>
      <image:caption>Artist's impression of the planet Ross 128 b, with the star Ross 128 visible in the background\(^{[1]}\) Credit: European Southern Observatory</image:caption>
    </image:image>
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      <image:title>gregschool-lessons - Preliminary Interstellar Missions: Prelude to the Stars</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5ba2df660ebbe8e7950982fd/1549254809135/50lys%5B1%5D.gif</image:loc>
      <image:title>gregschool-lessons - Preliminary Interstellar Missions: Prelude to the Stars</image:title>
      <image:caption>The image above is a map of a small fraction of nearby stars in our stellar neighborhood. It is a map of 130 stars located within 50 lightyears of us which are visible with the naked eye. This map shows only a tiny percent of that stars within 50 lightyears away from the Sun. There are in fact 1,800 known stars within this volume of space. To eliminate the threat of nearby supernovae, our descendants will one day visit all of these stars, either directly in which case their species actually arrives at the star, or indirectly by sending spacecraft and robots to those stars.</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5c2ab1408a922d1c5eac7c06/1549254809139/013532_med%5B1%5D.jpg</image:loc>
      <image:title>gregschool-lessons - Preliminary Interstellar Missions: Prelude to the Stars</image:title>
      <image:caption>Illustration of the James Webb Space Telescope, current as of September 2009. Top side. Image Source: https://web.archive.org/web/20100527230418/http://www.jwst.nasa.gov/images_artist13532.html</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5ba3e12d4785d325a53ca4b9/1549254809131/Stromatolites_in_Sharkbay%5B1%5D.jpg</image:loc>
      <image:title>gregschool-lessons - Preliminary Interstellar Missions: Prelude to the Stars</image:title>
      <image:caption>The stromatolites shown in the photograph above are fossils which were produced by cyanobacteria 3.5 billion years in Shark Bay, Australia. Cyanobacteria - a simple, single-celled lifeform - produced large amounts of oxygen via photosynthesis causing the first major oxygenation even in Earth’s history. Photograph taken by Paul Harrison.</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/5b9999c38985830bc3e13e12/5b9999c38985830bc3e13e13/1537289631769/grav_lens_telescope%5B1%5D.jpg</image:loc>
      <image:title>gregschool-lessons - Preliminary Interstellar Missions: Prelude to the Stars</image:title>
      <image:caption>A gravitational lens telescope, as envisioned by Claudio Maccone in his 2009 book Deep Space Flight and Communications. (Claudio Maccone)</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/5ba2fcd48985837c2df40ed1/5ba2ff790e2e7299a6f5ccdf/1549254809141/dvv.jpg</image:loc>
      <image:title>gregschool-lessons - Preliminary Interstellar Missions: Prelude to the Stars</image:title>
      <image:caption>Infographic above is from Time Magazine April 10, 2000.</image:caption>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/gregschoollessons/2018/5/23/star-lifting-colonizing-the-stars-and-the-galaxies</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2019-03-19</lastmod>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/5b999c2e4ae23743aeeb3b66/5b999c2e4ae23743aeeb3b67/1536890841527/jeremy-jozwik-ia-kuiperbeltterrain-comp2-0084.jpg</image:loc>
      <image:title>gregschool-lessons - Star Lifting: Colonizing the Stars and the Galaxies - Kuiper Belt Laser Array</image:title>
      <image:caption>Artist’s impression of an array of lasers built on a comet in the Kuiper Belt. These laser stations would also be built on comets within Oort clouds (not jude our own) and interstellar space to create an interstellar highway. Artwork by Jeremy Jozwik from Artstation who is also a member of the SFIA production team.</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5c8ea63ce4966b4eaee53ab5/1552945894119/Local_Group_and_nearest_galaxies%5B1%5D.jpg</image:loc>
      <image:title>gregschool-lessons - Star Lifting: Colonizing the Stars and the Galaxies</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5b999c2e4ae23743aeeb3b72/1528412559259/star+lifter.jpg</image:loc>
      <image:title>gregschool-lessons - Star Lifting: Colonizing the Stars and the Galaxies</image:title>
      <image:caption>Figure 2</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5c8eca1341920294c29e2339/1552960357080/neil-blevins-megastructures-9-gas-giant-refinery-5.jpg</image:loc>
      <image:title>gregschool-lessons - Star Lifting: Colonizing the Stars and the Galaxies</image:title>
      <image:caption>Artist’s depiction of gas giant refineries used to extract materials such as helium-3 and deuterium from the atmosphere of one of the Jovian planets. Artwork by Neil Blevins at Artstation.</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/5b999c2e4ae23743aeeb3b74/5b999c2e4ae23743aeeb3b75/1536791569975/neil-blevins-megastructures-1-ringworld-color-sketch%5B1%5D.jpg</image:loc>
      <image:title>gregschool-lessons - Star Lifting: Colonizing the Stars and the Galaxies</image:title>
      <image:caption>Artist’s depiction of a ring world. Artwork by Neil Blevins.</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/5b999c2e4ae23743aeeb3b74/5b999c2e4ae23743aeeb3b77/1536791569979/neil-blevins-megastructures-1-ringworld-design-packet%5B1%5D.jpg</image:loc>
      <image:title>gregschool-lessons - Star Lifting: Colonizing the Stars and the Galaxies</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5c8ecef271c10b4ed9c9920f/1552945894113/lzlsart9qi311%5B1%5D.jpg</image:loc>
      <image:title>gregschool-lessons - Star Lifting: Colonizing the Stars and the Galaxies</image:title>
      <image:caption>Nicoll-Dyson Beam “Unleashing The Nicoll-Dyson Beam from Gigastructural Engineering &amp; More. Inward Perfection has never been so easy when you can delete your enemies Capital systems with the press of a button. Edit: It also has multiple settings. Ranging from reducing all infrastructure to rubble to Solar System Deleter.” Image retrieved from: https://www.reddit.com/r/Stellaris/comments/8qgwe9/fear_me_for_i_am_your_apocalypse/</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/5b99cb580ebbe8e9409c31c5/5b99cb59b8a045cb6c9ee62c/1552945894093/neil-blevins-megastructures-7-star-lifter-3d-sketch.jpg</image:loc>
      <image:title>gregschool-lessons - Star Lifting: Colonizing the Stars and the Galaxies - Star Lifting</image:title>
      <image:caption>“A star lifter removes mass from a star for either raw materials or to change the nature of the star itself. For example, you may remove mass from the star to collect hydrogen or other elements. Or you could remove mass in order to extend the life of the star, to make the star dimmer, or reduce the chances of a super nova.” Artwork by Neil Blevins from Artstation.</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5c8ed502f9619a653708c330/1552945894116/Von-Neumann-Probe.jpg</image:loc>
      <image:title>gregschool-lessons - Star Lifting: Colonizing the Stars and the Galaxies</image:title>
      <image:caption>Concept art by Mark Molnar</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/5b999c2e4ae23743aeeb3b62/5b999c2e4ae23743aeeb3b63/1536791569963/Oneilcylinder1.jpg</image:loc>
      <image:title>gregschool-lessons - Star Lifting: Colonizing the Stars and the Galaxies</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/5c90091aee6eb0728acc7659/5c90091a0d929794c36ecafe/1552970568823/1080p-Space-Desktop-Background-hd-desktop-wallpapers-cool-images-hd-apple-background-wallpapers-colourfull-free-display-lovely-wallpapers.jpg</image:loc>
      <image:title>gregschool-lessons - Star Lifting: Colonizing the Stars and the Galaxies</image:title>
      <image:caption>Image retrieved from: https://thewallpaper.co/preview/?wallpaper=1080p-space-desktop-background-hd-desktop-wallpapers-cool-images-hd-apple-background-wallpapers-colourfull-free-display-lovely-wallpapers-1920x1080</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5b999c2e4ae23743aeeb3b6e/1528407608550/Star_lifting_1.svg%5B1%5D.png</image:loc>
      <image:title>gregschool-lessons - Star Lifting: Colonizing the Stars and the Galaxies</image:title>
      <image:caption>Figure 1: A star lifter would consist of a ring of solar power stations and ion accelerators distributed around a star in the shape of a ring.</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/5c8ecc64ec212d73478cc97a/5c8ecc6541920294c29e3aa2/1552945894108/neil-blevins-megastructures-12-nicoll-dyson-laser-design-packet.jpg</image:loc>
      <image:title>gregschool-lessons - Star Lifting: Colonizing the Stars and the Galaxies</image:title>
      <image:caption>Artist’s depiction of a Nicoll-Dyson Laser. Artwork by Neil Blevins at ArtStation.</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5b999c2e4ae23743aeeb3b70/1536791569973/Physics_of_the_future_Kaku_2011%5B1%5D.jpg</image:loc>
      <image:title>gregschool-lessons - Star Lifting: Colonizing the Stars and the Galaxies</image:title>
      <image:caption>"Physics of the Future: How Science Will Shape Human Destiny and Our Daily Lives by the Year 2100 is a 2011 book by theoretical physicist Michio Kaku, author of Hyperspace and Physics of the Impossible. In it Kaku speculates about possible future technological development over the next 100 years. He interviews notable scientists about their fields of research and lays out his vision of coming developments in medicine, computing, artificial intelligence, nanotechnology, and energy production. The book was on the New York Times Bestseller List for five weeks."</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/5b999c2e4ae23743aeeb3b6a/5b999c2e4ae23743aeeb3b6b/1536791569970/megastructures_7_star_lifter_3%5B1%5D.jpg</image:loc>
      <image:title>gregschool-lessons - Star Lifting: Colonizing the Stars and the Galaxies</image:title>
      <image:caption>Artist’s depiction of a star lifter. Artwork by Neil Blevins.</image:caption>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/gregschoollessons/string-theory-and-colonizing-the-multiverse</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2019-03-21</lastmod>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5c90816453450a5d43f2c56c/1553136306229/universeismath.jpg</image:loc>
      <image:title>gregschool-lessons - String Theory and Colonizing the Multiverse</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5be8c89403ce64619f88957f/1553136306240/shutterstock_84250684.jpg</image:loc>
      <image:title>gregschool-lessons - String Theory and Colonizing the Multiverse</image:title>
      <image:caption>Our universe may be one of many, physicists say. Credit: Shutterstock/Victor Habbick</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5c91d122e4966b53e036d921/1553136306245/CERN_LHC%5B1%5D.jpg</image:loc>
      <image:title>gregschool-lessons - String Theory and Colonizing the Multiverse</image:title>
      <image:caption>The image above shows a section of the LHC (Large Hadron Collider).</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5c91c81753450a802a19682f/1553136306234/calabi-yau7%5B1%5D.gif</image:loc>
      <image:title>gregschool-lessons - String Theory and Colonizing the Multiverse</image:title>
      <image:caption>“String Theory predicts the existence of more than the 3 space dimensions and 1 time dimension we are all familiar with. According to string theory, there are additional dimensions that we are unfamiliar with because they are curled up into tiny complicated shapes that can only be seen on tiny scales. If we could shrink to this tiny, Planck-sized scale we could see that at every 3D point in space, we can also explore 6 additional dimensions. This animation shows an array of Calabi-Yau spaces which are projections of these higher dimensions into the more familiar dimensions we are aware of.”\(^{[2]}\)</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5c931b0c4e17b65e89803aa0/1553144603597/T8F5x4MeyrzMFMXieSkmmL-970-80%5B1%5D.jpg</image:loc>
      <image:title>gregschool-lessons - String Theory and Colonizing the Multiverse</image:title>
      <image:caption>“An artist's interpretation of utilizing a wormhole to travel through space, Thorne kick-started a serious discussion among scientists about whether or wormhole travel is possible.”\(^{[1]}\) (Image: © NASA)</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5c91c69224a694ccc84b4b6f/1553136306232/four_forces%5B1%5D.jpg</image:loc>
      <image:title>gregschool-lessons - String Theory and Colonizing the Multiverse</image:title>
      <image:caption>Image Credit: https://physicswithsampurkis.files.wordpress.com/2014/01/four_forces.jpg</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5c91c9678165f5b9be0f4a49/1553136306237/crystal_to_string%5B1%5D.jpg</image:loc>
      <image:title>gregschool-lessons - String Theory and Colonizing the Multiverse</image:title>
      <image:caption>The image above shows how various different small objects compare to each other in terms of size. Image retrieved from: http://www.particlecentral.com/strings_page.html</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/5b99c907758d4663942abb33/5b99c9074d7a9ce10e1433c9/1553136306225/gateway_hub_04_by_lorddoomhammer-d9u3226.png</image:loc>
      <image:title>gregschool-lessons - String Theory and Colonizing the Multiverse</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5c91d09d7817f72e2c2ce7f4/1553136306242/LeonardSusskindStanford2009_cropped%5B1%5D.jpg</image:loc>
      <image:title>gregschool-lessons - String Theory and Colonizing the Multiverse</image:title>
      <image:caption>Leonard Susskind</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5c91d2624e17b673ce265308/1553136306249/matrioshka+brainnnn.png</image:loc>
      <image:title>gregschool-lessons - String Theory and Colonizing the Multiverse</image:title>
      <image:caption>“A matrioshka brain is a hypothetical megastructure proposed by Robert Bradbury, based on the Dyson sphere, of immense computational capacity. It is an example of a Class B stellar engine, employing the entire energy output of a star to drive computer systems.”\(^{[3]}\) Image from Steve Bowers</image:caption>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/gregschoollessons/2018/7/20/space-based-solar-power-6fp9c</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2019-04-07</lastmod>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5b71efdb70a6ad96d8884229/1534192981034/archh.png</image:loc>
      <image:title>gregschool-lessons - Inward Bound: How Should We Colonize the Earth?</image:title>
      <image:caption>Depiction of arcologies located on the surface of the sea. (Click image to enlarge.) Image credit: https://www.shimz.co.jp/en/topics/dream/content03/</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5b71efdb70a6ad96d888422f/1534192981042/untitledddddss.png</image:loc>
      <image:title>gregschool-lessons - Inward Bound: How Should We Colonize the Earth?</image:title>
      <image:caption>Illustrations of a floating city concept. Images Credit: https://www.shimz.co.jp/en/topics/dream/content03/</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5ca936b17817f75f41e83c78/1554593461999/ccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccc.png</image:loc>
      <image:title>gregschool-lessons - Inward Bound: How Should We Colonize the Earth?</image:title>
      <image:caption>Illustration of the Casimir effect Image Credit: https://commons.wikimedia.org/wiki/File:Casimir_plates.svg</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5b71efdb70a6ad96d888422d/1534192981040/archepelago.png</image:loc>
      <image:title>gregschool-lessons - Inward Bound: How Should We Colonize the Earth?</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/5b71efdb70a6ad96d8884221/5b71efdb70a6ad96d8884226/1534192981030/180714_Analemma_Earth-from-space_1600_c.jpg</image:loc>
      <image:title>gregschool-lessons - Inward Bound: How Should We Colonize the Earth?</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/5b71efdb70a6ad96d8884221/5b71efdb70a6ad96d8884224/1534192981027/161130_PU_Comet_on_20_November_NavCam_1600_c.jpg</image:loc>
      <image:title>gregschool-lessons - Inward Bound: How Should We Colonize the Earth?</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/5b71efdb70a6ad96d8884221/5b71efdb70a6ad96d8884222/1534192981023/180714_Analemma_hot-air-balloon_1600_c.jpg</image:loc>
      <image:title>gregschool-lessons - Inward Bound: How Should We Colonize the Earth?</image:title>
      <image:caption>Depiction of a skyscraper attached to an asteroid. Such a skyscraper could be an Atlas tower supported by active support; that is, projectiles which run through a closed-loop chamber which imparted momentum on the structure in order to keep the structure suspended in the air.</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5b71efdb70a6ad96d888422b/1534192981037/ddd.png</image:loc>
      <image:title>gregschool-lessons - Inward Bound: How Should We Colonize the Earth?</image:title>
      <image:caption>This infographic depicts the Ocean Spiral: a vast helical-shaped structure which would extend from the surface of the sea to the sea floor. (Click image to enlarge.) Image Credit: https://www.shimz.co.jp/en/topics/dream/content01/</image:caption>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/gregschoollessons/rotational-inertia</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2019-03-23</lastmod>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59d816fc4c326d0fa4a490fc/1553304546553/rotational+inertiaimg.jpg</image:loc>
      <image:title>gregschool-lessons - Rotational Inertia</image:title>
      <image:caption>Figure 1: The rotational inertia of a hollow sphere is given by \(I=\frac{2}{3}MR^2\) and the rotational inertia of a solid ball is given by \(\frac{2}{5}MR^2\). Since the lever arms \(r\) (perpendicular distance from the axis of rotation) of each mass element in the solid sphere is smaller (because each mass is closer to the axis of rotation) than the lever arms in the hollow sphere (since each mass is farther away from the axis of rotation), the solid sphere must have a smaller rotational inertia. According to Equation (2), if \(r\) is smaller, then the function \(r^2\) that we are taking the area under is smaller.</image:caption>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/gregschoollessons/super-intelligence-rise-of-the-machines</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2019-03-21</lastmod>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5c03389d2b6a28df2b7d173b/1553140043479/1541094535342-shutterstock_680929729%5B1%5D.jpg</image:loc>
      <image:title>gregschool-lessons - Super Intelligence: Rise of the Machines</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5c0303c3575d1f6d6b3d995b/1553140043463/lg-airport-robot-9.jpg</image:loc>
      <image:title>gregschool-lessons - Super Intelligence: Rise of the Machines</image:title>
      <image:caption>The two robots above help clean the floor and give directions to passengers at the Seoul-Incheon International Airport.</image:caption>
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      <image:title>gregschool-lessons - Super Intelligence: Rise of the Machines</image:title>
      <image:caption>Infographic source: https://www.huawei.com/en/about-huawei/publications/winwin-magazine/ai/how-intelligent-will-ai-get</image:caption>
    </image:image>
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      <image:title>gregschool-lessons - Super Intelligence: Rise of the Machines</image:title>
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      <image:title>gregschool-lessons - Super Intelligence: Rise of the Machines</image:title>
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      <image:title>gregschool-lessons - Super Intelligence: Rise of the Machines</image:title>
      <image:caption>Cover art from the Sci-Fi Masterworks edition of Do Androids Dream of Electric Sheep?</image:caption>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5c0323e46d2a738dea691847/1553140043470/Knowledge%252520Timeline%5B1%5D.gif</image:loc>
      <image:title>gregschool-lessons - Super Intelligence: Rise of the Machines</image:title>
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      <image:title>gregschool-lessons - Super Intelligence: Rise of the Machines</image:title>
      <image:caption>An example environment fed to the AI physicist. Here, the field of view is divided into four quadrants, each of which is governed by a different physical effect, such as gravity or an electromagnetic field. The dots and lines represent the ball’s trajectory through the environment. Based on how a ball moves through the environment, the AI must use the strategies it was given to describe the physical laws that are governing the ball’s motion. Image: Tegmark and Wu/arXiv</image:caption>
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      <image:title>gregschool-lessons - Super Intelligence: Rise of the Machines</image:title>
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      <image:title>gregschool-lessons - Super Intelligence: Rise of the Machines</image:title>
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      <image:title>gregschool-lessons - Super Intelligence: Rise of the Machines</image:title>
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      <image:title>gregschool-lessons - Super Intelligence: Rise of the Machines</image:title>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/gregschoollessons/robots-and-their-uses</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2019-03-22</lastmod>
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      <image:title>gregschool-lessons - Robots and their Uses</image:title>
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      <image:title>gregschool-lessons - Robots and their Uses</image:title>
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      <image:title>gregschool-lessons - Robots and their Uses</image:title>
      <image:caption>https://www.artstation.com/artwork/YxRbq</image:caption>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5c08b7f9f950b7c33192da63/1545767693608/if-you-could-visualize-grahams-curiosity-number-your-head-would-6200771.png</image:loc>
      <image:title>gregschool-lessons - Robots and their Uses</image:title>
      <image:caption>https://me.me/i/if-you-could-visualize-grahams-curiosity-number-your-head-would-3896085</image:caption>
    </image:image>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/5c0896b3032be44dcbeffda7/5c0896b340ec9a67bf39403c/1545767693571/neil-blevins-inc-the-robot-14-textured-poses1%5B1%5D.jpg</image:loc>
      <image:title>gregschool-lessons - Robots and their Uses</image:title>
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      <image:title>gregschool-lessons - Robots and their Uses</image:title>
      <image:caption>Image retrieved from: https://wall.alphacoders.com/big.php?i=524246</image:caption>
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      <image:title>gregschool-lessons - Robots and their Uses</image:title>
      <image:caption>Atlas from Boston Dynamics</image:caption>
    </image:image>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5c0f0050758d46ceef973400/1545767693610/any-sufficiently-advanced-technology-is-indistinguishable-from-magic-arthur-c-14468433.png</image:loc>
      <image:title>gregschool-lessons - Robots and their Uses</image:title>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/articles-page-11</loc>
    <changefreq>daily</changefreq>
    <priority>0.75</priority>
    <lastmod>2019-03-21</lastmod>
  </url>
  <url>
    <loc>https://www.gregschool.org/articles-page-11/2017/5/23/pauli-matrices-wf87n</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2018-04-09</lastmod>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59dc4fa57131a52388a462c6/1510177253510/electromagnetism+thumbnaillllll+imageeee.jpg</image:loc>
      <image:title>Articles page 11 - Pauli Matrices</image:title>
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  </url>
  <url>
    <loc>https://www.gregschool.org/articles-page-11/2017/5/23/the-eigenvalues-of-any-observable-hatl-must-be-real-3jrk4</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-11</lastmod>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59dc4f61ccc5c55311706d9c/1510177245093/electromagnetism+thumbnaillllll+imageeee.jpg</image:loc>
      <image:title>Articles page 11 - The Eigenvalues of any Observable \(\hat{L}\) must be Real</image:title>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/articles-page-11/2017/5/14/introduction-to-special-relativity-d23j8</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-09</lastmod>
  </url>
  <url>
    <loc>https://www.gregschool.org/articles-page-11/2017/6/28/8fldcv2rgvjvjwb42w67qh0ude4ii0-3yepp</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-09</lastmod>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59dd39f480bd5e3fd04102cd/1510177013572/space+travela+nd+colonization+thumbnail.jpg</image:loc>
      <image:title>Articles page 11 - Alcubierre Warp Drive</image:title>
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  </url>
  <url>
    <loc>https://www.gregschool.org/articles-page-11/2017/6/19/introduction-to-limits-wyfhl</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-07</lastmod>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a01d50fec212dc9f58d2911/1510076742404/limitss.jpg</image:loc>
      <image:title>Articles page 11 - Introduction to Limits and Derivatives</image:title>
      <image:caption>Figure 1: Above, I have graphed some arbitrary function \(g(x)\). At the point \(g(x_0)\), the slope or steepness of the curve is very small (indeed, it is zero) whereas at the point \(g(x_1)\) the slope of the curve is comparitevely large.</image:caption>
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      <image:title>Articles page 11 - Introduction to Limits and Derivatives</image:title>
      <image:caption>Table 1: Values of \(f(x)\) as \(x→2\) and as \(Δx→0\).</image:caption>
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      <image:title>Articles page 11 - Introduction to Limits and Derivatives</image:title>
      <image:caption>Figure 3 (click to enlarge): Graph of arbitrary function \(f(x)\). If we let \(h(x)=\frac{f(x+ Δx)-f(x)}{(x+Δx)-x}\), then the function \(h(x)\) gives us the slope of the line obtained by drawing a straight line through the two points \((x,f(x))\) and \((x+Δx,f(x+Δx))\). For example if \(Δx=Δx_1\), then \(h(x)=\frac{f(x+ Δx_1)-f(x)}{(x+Δx_1)-x}\) gives the slope of the line \(AB_1\) (dark green line) in the graph above. As the value of \(Δx\) gets closer and closer to equaling zero, the value of \(h(x)\) gets closer and closer to equaling the slope of the grey line in the graph above.</image:caption>
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    <image:image>
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      <image:title>Articles page 11 - Introduction to Limits and Derivatives</image:title>
      <image:caption>Figure 2: Graph of the function \(f(x)=x^2\). As the values of \(x\) get closer and closer to equaling \(2\), the values of \(x^2\) get closer and closer to equaling \(4\).</image:caption>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/articles-page-11/2017/8/10/einstein-equivalence-principle-8j2w9</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-09</lastmod>
  </url>
  <url>
    <loc>https://www.gregschool.org/articles-page-11/2017/9/10/how-to-produce-water-and-oxygen-on-mars-njmkh</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2018-04-07</lastmod>
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      <image:title>Articles page 11 - How to Produce Water and Oxygen on Mars</image:title>
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      <image:title>Articles page 11 - How to Produce Water and Oxygen on Mars</image:title>
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      <image:title>Articles page 11 - How to Produce Water and Oxygen on Mars</image:title>
      <image:caption>The rover above is capable of releasing frozen water from regolith by heating it using microwaves. Credit: SUTD/Gilmour Space Corporation</image:caption>
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      <image:title>Articles page 11 - How to Produce Water and Oxygen on Mars</image:title>
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      <image:title>Articles page 11 - How to Produce Water and Oxygen on Mars</image:title>
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      <image:title>Articles page 11 - How to Produce Water and Oxygen on Mars</image:title>
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      <image:title>Articles page 11 - How to Produce Water and Oxygen on Mars</image:title>
      <image:caption>"Truck, oven, and slag pile system for extracting water from Martian soil."\(^{[2]}\) Artwork by Michael Carroll.</image:caption>
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    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5ac95ad503ce649b2a22599f/1523147007558/share+b.jpg</image:loc>
      <image:title>Articles page 11 - How to Produce Water and Oxygen on Mars</image:title>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/articles-page-11/2017/5/23/math-interlude-cddln</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-11</lastmod>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59dc4f34f9a61e6c50c00f76/1510177213821/electromagnetism+thumbnaillllll+imageeee.jpg</image:loc>
      <image:title>Articles page 11 - Quantum Mechanics: Math Interlude</image:title>
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  </url>
  <url>
    <loc>https://www.gregschool.org/articles-page-11/2017/8/30/capacitance-32sgr</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-09</lastmod>
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      <image:title>Articles page 11 - Capacitance</image:title>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/articles-page-11/2017/8/30/finding-the-electric-field-produced-by-a-parallel-plate-capacitor-kpyfb</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-10-10</lastmod>
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      <image:title>Articles page 11 - Finding the Electric Field produced by a Parallel-Plate Capacitor</image:title>
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      <image:title>Articles page 11 - Finding the Electric Field produced by a Parallel-Plate Capacitor</image:title>
      <image:caption>Figure 2</image:caption>
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    <image:image>
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      <image:title>Articles page 11 - Finding the Electric Field produced by a Parallel-Plate Capacitor</image:title>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59dc399fa8b2b02864cc4160/1504719611725/ddd.png</image:loc>
      <image:title>Articles page 11 - Finding the Electric Field produced by a Parallel-Plate Capacitor</image:title>
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      <image:title>Articles page 11 - Finding the Electric Field produced by a Parallel-Plate Capacitor</image:title>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/new-blog-47</loc>
    <changefreq>daily</changefreq>
    <priority>0.75</priority>
    <lastmod>2018-07-20</lastmod>
  </url>
  <url>
    <loc>https://www.gregschool.org/new-blog-47/2018/7/5/proof-of-the-theorem-fracsinxx1-t6c3x-kz4ll</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2018-07-19</lastmod>
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      <image:title>Limits - Proof of the Theorem: \(\lim_{ϴ→0}\frac{sinϴ}{ϴ}=1\)</image:title>
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      <image:title>Limits - Proof of the Theorem: \(\lim_{ϴ→0}\frac{sinϴ}{ϴ}=1\)</image:title>
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    <image:image>
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      <image:title>Limits - Proof of the Theorem: \(\lim_{ϴ→0}\frac{sinϴ}{ϴ}=1\)</image:title>
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      <image:title>Limits - Proof of the Theorem: \(\lim_{ϴ→0}\frac{sinϴ}{ϴ}=1\)</image:title>
      <image:caption>Figure 2: As you can see graphically, for values of \(ϴ\) in the range \(\frac{-π}{2}&lt;ϴ&lt;\frac{π}{2}\), the following inequalities are true \(1≥\frac{sinϴ}{ϴ}≥cosϴ\). Notice that as \(ϴ\) approaches zero from both the negative and positive directions, the function \(\frac{sinϴ}{ϴ}\) gets "squeezed" into the same point on the graph.</image:caption>
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      <image:title>Limits - Proof of the Theorem: \(\lim_{ϴ→0}\frac{sinϴ}{ϴ}=1\)</image:title>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5b5121cb88251bcb129f1968/1531244510817/Limit_of_Sine_of_X_over_X-Proof_3.png</image:loc>
      <image:title>Limits - Proof of the Theorem: \(\lim_{ϴ→0}\frac{sinϴ}{ϴ}=1\)</image:title>
      <image:caption>Figure 1: The wedge \(⪦OBA\) (colored blue) comprises a portion of the unit circle. The lengths \(AB\) and \(AC\) are the radius of the unit circle and are therefore equal to one. The heights of the triangles \(△OBA\) and \(△OCA\) can be found using basic trigonometry.</image:caption>
    </image:image>
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      <image:title>Limits - Proof of the Theorem: \(\lim_{ϴ→0}\frac{sinϴ}{ϴ}=1\)</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5b5121cb88251bcb129f195c/1531965731847/share+calculus+img.png</image:loc>
      <image:title>Limits - Proof of the Theorem: \(\lim_{ϴ→0}\frac{sinϴ}{ϴ}=1\)</image:title>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/new-blog-47/2017/6/19/introduction-to-limits-wyfhl-ppzfc-e3np3</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2018-07-20</lastmod>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5b5125d970a6ade9ec7a0759/1510075871512/limits1.jpg</image:loc>
      <image:title>Limits - Introduction to Limits and Derivatives</image:title>
      <image:caption>Figure 2: Graph of the function \(f(x)=x^2\). As the values of \(x\) get closer and closer to equaling \(2\), the values of \(x^2\) get closer and closer to equaling \(4\).</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5b5125d970a6ade9ec7a075b/1510074097073/limits2.jpg</image:loc>
      <image:title>Limits - Introduction to Limits and Derivatives</image:title>
      <image:caption>Figure 3 (click to enlarge): Graph of arbitrary function \(f(x)\). If we let \(h(x)=\frac{f(x+ Δx)-f(x)}{(x+Δx)-x}\), then the function \(h(x)\) gives us the slope of the line obtained by drawing a straight line through the two points \((x,f(x))\) and \((x+Δx,f(x+Δx))\). For example if \(Δx=Δx_1\), then \(h(x)=\frac{f(x+ Δx_1)-f(x)}{(x+Δx_1)-x}\) gives the slope of the line \(AB_1\) (dark green line) in the graph above. As the value of \(Δx\) gets closer and closer to equaling zero, the value of \(h(x)\) gets closer and closer to equaling the slope of the grey line in the graph above.</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5b5125d970a6ade9ec7a0755/1510069531644/limitss.jpg</image:loc>
      <image:title>Limits - Introduction to Limits and Derivatives</image:title>
      <image:caption>Figure 1: Above, I have graphed some arbitrary function \(g(x)\). At the point \(g(x_0)\), the slope or steepness of the curve is very small (indeed, it is zero) whereas at the point \(g(x_1)\) the slope of the curve is comparitevely large.</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5b5125d970a6ade9ec7a0757/1510075248757/limit3.jpg</image:loc>
      <image:title>Limits - Introduction to Limits and Derivatives</image:title>
      <image:caption>Table 1: Values of \(f(x)\) as \(x→2\) and as \(Δx→0\).</image:caption>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/new-blog-45</loc>
    <changefreq>daily</changefreq>
    <priority>0.75</priority>
    <lastmod>2018-07-20</lastmod>
  </url>
  <url>
    <loc>https://www.gregschool.org/new-blog-45/2017/10/22/partial-derivatives</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-09</lastmod>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59fe26fe8e7b0f1f9f7e5323/1509828728481/twiiter+img+thumbnail.jpg</image:loc>
      <image:title>Derivatives - Introduction to Partial Derivatives</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59f677c427ef2d09a24002fa/1509828728490/partial+derivatives.jpg</image:loc>
      <image:title>Derivatives - Introduction to Partial Derivatives</image:title>
      <image:caption>Figure 2: The entire blue surface is given by the function \(f(x,y)=x^2+y^2\). By letting \(y=1\), we that \(y^2=1\) and \(f(x,1)=x^2+1\) giving us a parabola shifted up one unit along the \(z\)-axis. That is how we can analytically obtain the parabola \(f(x,y)\). We can also obtain \(f(x,1)\) by passing the plane \(y=1\) (illustrated as the black plane above) through the surface \(f(x,y)\). The points at which the two surfaces (the surface \(f(x,y)\) and the plane \(y=1\)) intersect form the red parabola drawn in the image above. Image credit: By IkamusumeFan (Own work) [CC BY-SA 4.0 (https://creativecommons.org/licenses/by-sa/4.0)], via Wikimedia Commons.</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59fe27cbec212d4734986096/1509828728477/share+calculus+img.png</image:loc>
      <image:title>Derivatives - Introduction to Partial Derivatives</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59fe26e00d929758eafe1ed0/1509828728479/facebook+img+thumbnail.jpg</image:loc>
      <image:title>Derivatives - Introduction to Partial Derivatives</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59fe26a224a6943fd0cc16bc/1509828728487/Calculus+thumbnail.png</image:loc>
      <image:title>Derivatives - Introduction to Partial Derivatives</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59fe26ba24a6943fd0cc1a0d/1509828728485/email+img+thumbnail.jpg</image:loc>
      <image:title>Derivatives - Introduction to Partial Derivatives</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59fe26f353450a448c72dc7a/1509828728483/google+img+thumbnail.jpg</image:loc>
      <image:title>Derivatives - Introduction to Partial Derivatives</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59ed4b5ab7411cd96fcdb29b/1509828728488/MSP5083101ccb77dc1c84hg00003d8bb0b0083b496c.gif</image:loc>
      <image:title>Derivatives - Introduction to Partial Derivatives</image:title>
      <image:caption>Figure 1: Graph of the surface \(f(x,y)=x^2+y^2\). Image courtesy of Wolfram Alpha.</image:caption>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/new-blog-45/2017/6/19/introduction-to-limits-wyfhl-ppzfc</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-07</lastmod>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a01f14671c10b9fdcfa2d12/1510074097073/limits2.jpg</image:loc>
      <image:title>Derivatives - Introduction to Limits and Derivatives</image:title>
      <image:caption>Figure 3 (click to enlarge): Graph of arbitrary function \(f(x)\). If we let \(h(x)=\frac{f(x+ Δx)-f(x)}{(x+Δx)-x}\), then the function \(h(x)\) gives us the slope of the line obtained by drawing a straight line through the two points \((x,f(x))\) and \((x+Δx,f(x+Δx))\). For example if \(Δx=Δx_1\), then \(h(x)=\frac{f(x+ Δx_1)-f(x)}{(x+Δx_1)-x}\) gives the slope of the line \(AB_1\) (dark green line) in the graph above. As the value of \(Δx\) gets closer and closer to equaling zero, the value of \(h(x)\) gets closer and closer to equaling the slope of the grey line in the graph above.</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a01f14671c10b9fdcfa2d0c/1510069531644/limitss.jpg</image:loc>
      <image:title>Derivatives - Introduction to Limits and Derivatives</image:title>
      <image:caption>Figure 1: Above, I have graphed some arbitrary function \(g(x)\). At the point \(g(x_0)\), the slope or steepness of the curve is very small (indeed, it is zero) whereas at the point \(g(x_1)\) the slope of the curve is comparitevely large.</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a01f14671c10b9fdcfa2d10/1510075871512/limits1.jpg</image:loc>
      <image:title>Derivatives - Introduction to Limits and Derivatives</image:title>
      <image:caption>Figure 2: Graph of the function \(f(x)=x^2\). As the values of \(x\) get closer and closer to equaling \(2\), the values of \(x^2\) get closer and closer to equaling \(4\).</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5a01f14671c10b9fdcfa2d0e/1510075248757/limit3.jpg</image:loc>
      <image:title>Derivatives - Introduction to Limits and Derivatives</image:title>
      <image:caption>Table 1: Values of \(f(x)\) as \(x→2\) and as \(Δx→0\).</image:caption>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/new-blog-32</loc>
    <changefreq>daily</changefreq>
    <priority>0.75</priority>
    <lastmod>2018-09-15</lastmod>
  </url>
  <url>
    <loc>https://www.gregschool.org/new-blog-32/2018/9/15/nuclear-fusion-engines</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2018-09-15</lastmod>
  </url>
  <url>
    <loc>https://www.gregschool.org/month-1</loc>
    <changefreq>daily</changefreq>
    <priority>0.75</priority>
    <lastmod>2019-01-02</lastmod>
  </url>
  <url>
    <loc>https://www.gregschool.org/month-2</loc>
    <changefreq>daily</changefreq>
    <priority>0.75</priority>
    <lastmod>2019-01-20</lastmod>
  </url>
  <url>
    <loc>https://www.gregschool.org/month-3</loc>
    <changefreq>daily</changefreq>
    <priority>0.75</priority>
    <lastmod>2019-01-21</lastmod>
  </url>
  <url>
    <loc>https://www.gregschool.org/new-blog-75</loc>
    <changefreq>daily</changefreq>
    <priority>0.75</priority>
    <lastmod>2019-01-02</lastmod>
  </url>
  <url>
    <loc>https://www.gregschool.org/new-blog-72</loc>
    <changefreq>daily</changefreq>
    <priority>0.75</priority>
    <lastmod>2019-01-21</lastmod>
  </url>
  <url>
    <loc>https://www.gregschool.org/new-blog-52</loc>
    <changefreq>daily</changefreq>
    <priority>0.75</priority>
    <lastmod>2018-11-25</lastmod>
  </url>
  <url>
    <loc>https://www.gregschool.org/new-blog-6</loc>
    <changefreq>daily</changefreq>
    <priority>0.75</priority>
    <lastmod>2018-12-04</lastmod>
  </url>
  <url>
    <loc>https://www.gregschool.org/superconducters-post-in-article</loc>
    <changefreq>daily</changefreq>
    <priority>0.75</priority>
    <lastmod>2019-01-02</lastmod>
  </url>
  <url>
    <loc>https://www.gregschool.org/superconducters-post-in-article/2017/1/23/superconductors-the-future-of-transportation-and-electric-transmission-d5e6r-7zcs4</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2019-01-02</lastmod>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5c2d286a562fa78fef791cfc/1509744831827/facebook+img+thumbnail.jpg</image:loc>
      <image:title>Superconducterrss - posst in article - Superconductors: the Future of Transportation and Electric Transmission</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5c2d286a562fa78fef791d00/1509744847045/</image:loc>
      <image:title>Superconducterrss - posst in article - Superconductors: the Future of Transportation and Electric Transmission</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5c2d286a562fa78fef791d02/1509744550746/email+img+thumbnail.jpg</image:loc>
      <image:title>Superconducterrss - posst in article - Superconductors: the Future of Transportation and Electric Transmission</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5c2d286a562fa78fef791cfa/1509744676939/</image:loc>
      <image:title>Superconducterrss - posst in article - Superconductors: the Future of Transportation and Electric Transmission</image:title>
    </image:image>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5c2d286a562fa78fef791d04/1509744531017/technology+thumbnail.png</image:loc>
      <image:title>Superconducterrss - posst in article - Superconductors: the Future of Transportation and Electric Transmission</image:title>
    </image:image>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5c2d286a562fa78fef791cfe/1509744812574/twiiter+img+thumbnail.jpg</image:loc>
      <image:title>Superconducterrss - posst in article - Superconductors: the Future of Transportation and Electric Transmission</image:title>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/new-blog-62</loc>
    <changefreq>daily</changefreq>
    <priority>0.75</priority>
    <lastmod>2019-01-04</lastmod>
  </url>
  <url>
    <loc>https://www.gregschool.org/new-blog-62/2019/1/4/paralyzed-monkeys-regain-control-of-their-legs-after-brain-implants</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2019-01-04</lastmod>
  </url>
  <url>
    <loc>https://www.gregschool.org/new-blog-62/tag/CNN</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
  </url>
  <url>
    <loc>https://www.gregschool.org/new-blog-62/tag/Meera+Senthilingam</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
  </url>
  <url>
    <loc>https://www.gregschool.org/outward-bound-2</loc>
    <changefreq>daily</changefreq>
    <priority>0.75</priority>
    <lastmod>2019-03-21</lastmod>
  </url>
  <url>
    <loc>https://www.gregschool.org/outward-bound-2/2018/5/23/preliminary-interstellar-missions-prelude-to-the-stars-tlm8g</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2019-02-24</lastmod>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5c722c4cb208fc188c75330d/1549254809125/mars_hs-2016-15-a-full_tif%5B1%5D.jpg</image:loc>
      <image:title>New Blog - Preliminary Interstellar Missions: Prelude to the Stars</image:title>
      <image:caption>“This Hubble Space Telescope image of Mars shows details 20 to 30 miles across. A solar gravitational lens telescope would get even sharper views of exoplanets up to 100 light years away.”\(^{[4]}\) (STScI/AURA), J. Bell (ASU), and M. Wolff) Source URL: https://www.airspacemag.com/daily-planet/ultimate-space-telescope-would-use-sun-lens-180962499/</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5c722c4cb208fc188c753315/1549254809131/Stromatolites_in_Sharkbay%5B1%5D.jpg</image:loc>
      <image:title>New Blog - Preliminary Interstellar Missions: Prelude to the Stars</image:title>
      <image:caption>The stromatolites shown in the photograph above are fossils which were produced by cyanobacteria 3.5 billion years in Shark Bay, Australia. Cyanobacteria - a simple, single-celled lifeform - produced large amounts of oxygen via photosynthesis causing the first major oxygenation even in Earth’s history. Photograph taken by Paul Harrison.</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/5c722c4cb208fc188c75331f/5c722c4cb208fc188c753320/1549254809141/dvv.jpg</image:loc>
      <image:title>New Blog - Preliminary Interstellar Missions: Prelude to the Stars</image:title>
      <image:caption>Infographic above is from Time Magazine April 10, 2000.</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5c722c4cb208fc188c753313/1549254809129/NASA-WhatBiosignaturesDoesLifeProduce-20180625%5B1%5D.jpg</image:loc>
      <image:title>New Blog - Preliminary Interstellar Missions: Prelude to the Stars</image:title>
      <image:caption>The combination of certain molecules and the absence of certain molecules in an exoplanet’s atmosphere is only likely if life is inhabited on that world: such combinations are called disequilibrium mixtures. As the light emitted from a star passes through an exoplanet’s atmosphere, the molecules in that exoplanet’s atmosphere absorb only certain wavelengths. Given which wavelengths were absorbed, we can determine whether or not disequilibrium mixtures are present in that exoplanet’s atmosphere and, consequently, assess the likelihood that extraterrestrial life inhabits that world. NASA/Aaron Gronsta</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5c722c4cb208fc188c753317/1549254809133/Great+Oxidization+Event.jpg</image:loc>
      <image:title>New Blog - Preliminary Interstellar Missions: Prelude to the Stars</image:title>
      <image:caption>Diagram of the evolution of atmospheric oxygen concentration during the history of the planet. © Ido, Pierre Sans-Jofre</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5c722c4cb208fc188c753319/1549254809135/50lys%5B1%5D.gif</image:loc>
      <image:title>New Blog - Preliminary Interstellar Missions: Prelude to the Stars</image:title>
      <image:caption>The image above is a map of a small fraction of nearby stars in our stellar neighborhood. It is a map of 130 stars located within 50 lightyears of us which are visible with the naked eye. This map shows only a tiny percent of that stars within 50 lightyears away from the Sun. There are in fact 1,800 known stars within this volume of space. To eliminate the threat of nearby supernovae, our descendants will one day visit all of these stars, either directly in which case their species actually arrives at the star, or indirectly by sending spacecraft and robots to those stars.</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5c722c4cb208fc188c75331d/1549254809139/013532_med%5B1%5D.jpg</image:loc>
      <image:title>New Blog - Preliminary Interstellar Missions: Prelude to the Stars</image:title>
      <image:caption>Illustration of the James Webb Space Telescope, current as of September 2009. Top side. Image Source: https://web.archive.org/web/20100527230418/http://www.jwst.nasa.gov/images_artist13532.html</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5c722c4cb208fc188c753323/1549254809143/microwave-sail-starwisp-n.jpg</image:loc>
      <image:title>New Blog - Preliminary Interstellar Missions: Prelude to the Stars</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/5c722c4cb208fc188c75330f/5c722c4cb208fc188c753310/1549254809127/1280px-Artist%27s_impression_of_the_planet_Ross_128_b%5B1%5D.jpg</image:loc>
      <image:title>New Blog - Preliminary Interstellar Missions: Prelude to the Stars</image:title>
      <image:caption>Artist's impression of the planet Ross 128 b, with the star Ross 128 visible in the background\(^{[1]}\) Credit: European Southern Observatory</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5c722c4cb208fc188c75331b/1549254809137/Welcome_to_the_Universe_by_Neil_deGrasse_Tyson%3B_book_cover.jpg</image:loc>
      <image:title>New Blog - Preliminary Interstellar Missions: Prelude to the Stars</image:title>
      <image:caption>Welcome to the Universe: An Astrophysical Tour is a popular science book by Neil deGrasse Tyson, Michael A. Strauss, and J. Richard Gott, based on an introductory astrophysics course they co-taught at Princeton University. The book was published by the Princeton University Press on September 20, 2016.\(^{[6]}\)</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5c722c4cb208fc188c75330b/1536791569946/3E58320900000578-0-image-a-2_1489702334064%5B1%5D.jpg</image:loc>
      <image:title>New Blog - Preliminary Interstellar Missions: Prelude to the Stars</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/5c722c4cb208fc188c753307/5c722c4cb208fc188c753308/1537289631769/grav_lens_telescope%5B1%5D.jpg</image:loc>
      <image:title>New Blog - Preliminary Interstellar Missions: Prelude to the Stars</image:title>
      <image:caption>A gravitational lens telescope, as envisioned by Claudio Maccone in his 2009 book Deep Space Flight and Communications. (Claudio Maccone)</image:caption>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/outward-bound-2/2019/2/7/leaving-the-solar-system-f2tx3</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2019-02-24</lastmod>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/5c722d9b9140b72b900de5e0/5c722d9b9140b72b900de5e1/1550429768539/This-is-How-Earth-Moves-1.jpg</image:loc>
      <image:title>New Blog - Leaving the Solar System: Introduction to the Outward Bound Series</image:title>
      <image:caption>This image illustrates the fact that the Sun is actually moving through space relative to the Milky Way galaxy; from this frame of reference, the Earth is moving in a spiral-shaped path. Of course, we can actually alter this path as well as the Sun’s speed using a type of megastructure known as a Shkadov thruster; you could, in fact, give the Sun (and the Earth which goes around it) a radically different path which heads off-course away from the galaxy. Image retrieved from: https://wordlesstech.com/this-is-how-earth-moves/</image:caption>
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    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5c722d9b9140b72b900de5de/1550429768537/wright_brothers%5B1%5D.jpg</image:loc>
      <image:title>New Blog - Leaving the Solar System: Introduction to the Outward Bound Series</image:title>
      <image:caption>The Wright brothers on the steps of their boyhood home at 7 Hawthorn St. in Dayton.\(^{[1]}\) Carillon Historical Park</image:caption>
    </image:image>
    <image:image>
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      <image:title>New Blog - Leaving the Solar System: Introduction to the Outward Bound Series</image:title>
      <image:caption>Infographic retrieved from: https://www.spaceanswers.com/issue-previews/5025/5025/</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5c722d9b9140b72b900de5d0/1550429768522/WH-Phoebe-1024x599%5B1%5D.jpg</image:loc>
      <image:title>New Blog - Leaving the Solar System: Introduction to the Outward Bound Series</image:title>
      <image:caption>Image retrieved from: https://crossingzebras.com/wormhole-space-after-phoebe/</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5c722d9b9140b72b900de5d2/1550429768524/quote-the-moral-landscape-is-the-framework-i-use-for-thinking-about-questions-of-morality-sam-harris-12-51-41%5B1%5D.jpg</image:loc>
      <image:title>New Blog - Leaving the Solar System: Introduction to the Outward Bound Series</image:title>
      <image:caption>Quote by Sam Harris, author of the book, The Moral Landscape.</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5c722d9b9140b72b900de5d4/1550429768526/maxresdefault.jpg</image:loc>
      <image:title>New Blog - Leaving the Solar System: Introduction to the Outward Bound Series</image:title>
    </image:image>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5c722d9b9140b72b900de5e4/1550429768542/grav_lens_telescope%5B1%5D%5B1%5D.jpg</image:loc>
      <image:title>New Blog - Leaving the Solar System: Introduction to the Outward Bound Series</image:title>
      <image:caption>A gravitational lens telescope, as envisioned by Claudio Maccone in his 2009 book Deep Space Flight and Communications. (Claudio Maccone)</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/5c722d9b9140b72b900de5da/5c722d9b9140b72b900de5db/1550429768532/every_thing_that_comes_to_end.jpg</image:loc>
      <image:title>New Blog - Leaving the Solar System: Introduction to the Outward Bound Series</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/5c722d9b9140b72b900de5cc/5c722d9b9140b72b900de5cd/1550429768519/84v8X%5B1%5D.jpg</image:loc>
      <image:title>New Blog - Leaving the Solar System: Introduction to the Outward Bound Series</image:title>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/outward-bound-2/spaceship-comets-and-highways-through-space-5ec48-mpl83</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2019-02-24</lastmod>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5c7312bf0d9297df0c46ebac/1546401363659/swe12_10836_coverbackgroundshadowport_mattbradbury%5B1%5D.jpg</image:loc>
      <image:title>New Blog - Spaceship Comets and Highways Through Space</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/5c7312bf0d9297df0c46ebba/5c7312bf0d9297df0c46ebbd/1536987150213/MarsAndTheSpaceElevator%5B1%5D.jpg</image:loc>
      <image:title>New Blog - Spaceship Comets and Highways Through Space</image:title>
      <image:caption>“Here is a new montage showing the base of the space elevator on the tented town called "Sheffield", built on the summit of Pavonis Mons volcano (see Red Mars). The cable is supposed to be 10m thick, which means here that Sheffield city is very big here, at a large level of development. On the foreground, you can see colored urban lights. I imagine the main entry to the planet's surface would be like a rich and welcoming show for new settlers. I also imagine the tent' skin would be blue, to balance the red and grey landscape.”\(^{[59]}\)</image:caption>
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    <image:image>
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      <image:title>New Blog - Spaceship Comets and Highways Through Space</image:title>
      <image:caption>Artist’s impression of a space elevator connecting to the domed over city, Sheifeild, located on Pvonic Mons in Kim Robinson’s Mars trilogy. Images retrieved from: http://davinci-marsdesign.blogspot.com/2012/04/sheffield-and-space-elevator.html</image:caption>
    </image:image>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/5c7312bf0d9297df0c46eb90/5c7312bf0d9297df0c46eb91/1536889609120/jakub-grygier-026-interstellar-travel-ad.jpg</image:loc>
      <image:title>New Blog - Spaceship Comets and Highways Through Space - Copy of Copy of Interstellar Spaceship</image:title>
      <image:caption>Artist’s depiction of an interstellar spaceship accellerated by laser beams. Artwork by Jakub Grygier from Artstation.</image:caption>
    </image:image>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/5c7312bf0d9297df0c46eb72/5c7312bf0d9297df0c46eb73/1551042796892/space-travel-1200x675%5B1%5D.jpg</image:loc>
      <image:title>New Blog - Spaceship Comets and Highways Through Space</image:title>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/5c7312bf0d9297df0c46eb9c/5c7312bf0d9297df0c46eb9d/1536896112581/Superlaser2.jpg</image:loc>
      <image:title>New Blog - Spaceship Comets and Highways Through Space - Copy of Copy of Death Star</image:title>
      <image:caption>Artist’s depiction of a death star. By building a shell world of the kind described by the scientist Paul Birch around a faint dead star (i.e. a brown dwarf), the faint radiation which that star gives off could be collected and used to power a gigantic laser mounted on the surface of a shell world. Thus, as far fetched as the idea might seem, it isn’t totally implausable. Image retrieved from: Artist’s depiction of a comet being used as a spaceship. Image retrieved from: http://earth-chronicles.ru/news/2014-04-21-63940</image:caption>
    </image:image>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/5c7312bf0d9297df0c46ebae/5c7312bf0d9297df0c46ebaf/1536717071163/jeremy-jozwik-ia-kuiperbeltterrain-comp2-0084.jpg</image:loc>
      <image:title>New Blog - Spaceship Comets and Highways Through Space</image:title>
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    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5c7312bf0d9297df0c46eb7c/1536985604633/41WSCf9QqtL._SX333_BO1%2C204%2C203%2C200_.jpg</image:loc>
      <image:title>New Blog - Spaceship Comets and Highways Through Space</image:title>
      <image:caption>Robert Zubrin’s book, Entering Space, covers topics ranging from colonizing Mars and the solar system and explores the feasibility of interstellar travel with known physics.\(^{[1]}\)</image:caption>
    </image:image>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5c7312bf0d9297df0c46ebb8/1537145174696/9780553373356-uk%5B1%5D.jpg</image:loc>
      <image:title>New Blog - Spaceship Comets and Highways Through Space</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/5c7312bf0d9297df0c46ebda/5c7312bf0d9297df0c46ebdb/1538604155467/1_hHjG69bPm3VrMyUG2idPKg.jpeg</image:loc>
      <image:title>New Blog - Spaceship Comets and Highways Through Space</image:title>
      <image:caption>“Conceptual model of a growing and evolving asteroid starship. The image of comet 67P by ESA is used as a placeholder for a large asteroid.”\(^{[6]}\) Composite image by Francisco Muñoz and Anton Dobrevski</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/5c7312bf0d9297df0c46eb7e/5c7312bf0d9297df0c46eb7f/1536986254211/lunar-mining-base.jpg</image:loc>
      <image:title>New Blog - Spaceship Comets and Highways Through Space</image:title>
      <image:caption>The power requirements of buried human habitats and propellant production plants could be met by the widely spaced solar power panels shown above. Image: anna.j.nesterova@gmail.com</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/5c7312bf0d9297df0c46ebce/5c7312bf0d9297df0c46ebcf/1536898850377/jhm27etrwqj7fgpuxvuj%5B1%5D.jpg</image:loc>
      <image:title>New Blog - Spaceship Comets and Highways Through Space</image:title>
      <image:caption>Asteroid settlement concept. Credit and Copyright: Bryan Versteeg / DSI.</image:caption>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/5c7312bf0d9297df0c46ebce/5c7312bf0d9297df0c46ebd1/1536898837446/liian1htqo3l6hvx4kkj%5B1%5D.jpg</image:loc>
      <image:title>New Blog - Spaceship Comets and Highways Through Space</image:title>
      <image:caption>Concept art for DSI's "Harvestor" craft. Credit and Copyright: Bryan Versteeg / DSI.</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5c7312bf0d9297df0c46eb76/1536288589788/Skylab-73-HC-440HR%5B1%5D.jpg</image:loc>
      <image:title>New Blog - Spaceship Comets and Highways Through Space</image:title>
      <image:caption>Image of the Saturn V rocket launching to space. Image courtesy of NASA.</image:caption>
    </image:image>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/5c7312bf0d9297df0c46eba0/5c7312bf0d9297df0c46eba1/1536861860343/d00fccc571b621e809cb4ef1b9b98ee7_full.jpg</image:loc>
      <image:title>New Blog - Spaceship Comets and Highways Through Space</image:title>
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      <image:title>New Blog - Spaceship Comets and Highways Through Space</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5c7312bf0d9297df0c46ebde/1538678002285/1449-enz.jpg</image:loc>
      <image:title>New Blog - Spaceship Comets and Highways Through Space</image:title>
      <image:caption>The map above shows the migration patterns and timeline of the Polynesians who traveled from Asia to America by hopping from one tiny archipelago to another. Our descendants who travel from the Earth to the exoplanet Proxima B might adopt an analogous strategy by hopping from one comet to another until they reach their final destination. Image retrieved from: https://teara.govt.nz/en/map/1449/map-of-pacific-migrations</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5c7312bf0d9297df0c46eb9a/1536857488613/alphacentfix2%5B1%5Dkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkk.jpg</image:loc>
      <image:title>New Blog - Spaceship Comets and Highways Through Space</image:title>
      <image:caption>Image Source: https://i4is.org/wp-content/uploads/2018/05/Principium21.pdf</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5c7312bf0d9297df0c46ebca/1536896886414/jhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhh.jpg</image:loc>
      <image:title>New Blog - Spaceship Comets and Highways Through Space</image:title>
      <image:caption>“This artist's concept puts solar system distances in perspective. The scale bar is in astronomical units, with each set distance beyond 1 AU representing 10 times the previous distance. One AU is the distance from the Sun to the Earth, which is about 93 million miles or 150 million kilometers. Neptune, the most distant planet from the Sun, is about 30 AU.”\(^{[4]}\) Image Credit: NASA/JPL-Caltech</image:caption>
    </image:image>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/5c7312bf0d9297df0c46eb96/5c7312bf0d9297df0c46eb97/1536856111055/alphacentfix2%5B1%5Dkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkk.jpg</image:loc>
      <image:title>New Blog - Spaceship Comets and Highways Through Space - Copy of Copy of Trip to Alpha Centauri using a Starshot Probe</image:title>
      <image:caption>SCMP Graphic: Dennis Wong, Dang Elland Sources: Universe Today, SIMBAD Dacabase, SCMP research</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/5c7312bf0d9297df0c46eba4/5c7312bf0d9297df0c46eba5/1536859913266/evolvingaste%5B1%5D.jpg</image:loc>
      <image:title>New Blog - Spaceship Comets and Highways Through Space</image:title>
      <image:caption>Credit: Nils Faber &amp; Angelo Vermeulen</image:caption>
    </image:image>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/5c7312bf0d9297df0c46ebb2/5c7312bf0d9297df0c46ebb3/1536896535625/colony19%5B1%5D.jpg</image:loc>
      <image:title>New Blog - Spaceship Comets and Highways Through Space</image:title>
      <image:caption />
    </image:image>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5c7312bf0d9297df0c46eb8a/1536853434848/ephemeralizationnnnnn.jpg</image:loc>
      <image:title>New Blog - Spaceship Comets and Highways Through Space</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5c7312bf0d9297df0c46ebd6/1536900915403/hexagonal+array.png</image:loc>
      <image:title>New Blog - Spaceship Comets and Highways Through Space</image:title>
      <image:caption>“This hexagonal array of starlight mirrors might support a co-living group of twenty-five adults and children. Each of the mirrors is about the size of the continental United States, and the entire mirror “farm” is about 30,000 kilometers across.”\(^{[37]}\)</image:caption>
    </image:image>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/5c7312bf0d9297df0c46ebc0/5c7312bf0d9297df0c46ebc1/1541980302277/ksr-04.png</image:loc>
      <image:title>New Blog - Spaceship Comets and Highways Through Space</image:title>
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      <image:title>New Blog - Spaceship Comets and Highways Through Space</image:title>
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      <image:title>New Blog - Spaceship Comets and Highways Through Space</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/5c7312bf0d9297df0c46ebc0/5c7312bf0d9297df0c46ebc7/1537243316507/kkkk.png</image:loc>
      <image:title>New Blog - Spaceship Comets and Highways Through Space</image:title>
      <image:caption>Infographics represent a visual explanation of the so-called terrariums discussed in Kim Stanley Robinsons, 2312. Also, there is a slight error in the last infographic: the asteroid does not spin, rather a cylinder inside of the hollowed out asteroid is the thing which is actually spinning. Infographics created by Pablo Defendini. Infographics retrieved from: http://www.defendini.com/2312.html</image:caption>
    </image:image>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/5c7312bf0d9297df0c46eba8/5c7312bf0d9297df0c46eba9/1536859707540/Asteroid+Mining+Station+by+Bas+Ruhe%5B1%5D.jpg</image:loc>
      <image:title>New Blog - Spaceship Comets and Highways Through Space - Copy of Copy of Asteroid Mining Station</image:title>
      <image:caption>Artist’s depicion of a colonized asteroid. Artwork by Bas Ruhe from Artstation.</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5c7312bf0d9297df0c46ebcc/1537041005162/energy-from-space-1.jpg</image:loc>
      <image:title>New Blog - Spaceship Comets and Highways Through Space</image:title>
      <image:caption>Using a nuclear reactor to fuse together deuterium and helium-3 would generate a lot of energy; that energy would be transferred to a shock absorber on the rear of a spaceship which would give the spaceship thrust thereby causing it to accelerate. Image retrieved from: https://science.howstuffworks.com/environmental/green-science/energy-from-space.htm</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/5c7312bf0d9297df0c46eb8c/5c7312bf0d9297df0c46eb8d/1537229707309/790097132176630087%5B2%5D.jpg</image:loc>
      <image:title>New Blog - Spaceship Comets and Highways Through Space - Copy of Copy of Spaceship Asteroid</image:title>
      <image:caption>“The concept of turning an asteroid into a spacecraft is not entirely new: conceptual designer Bryan Versteeg has been working with the Mars One Team to imagine how we could use large asteroids for mining, transportation and habitat.”\(^{[2]}\) Credit: http://www.spacehabs.com/</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5c7312bf0d9297df0c46ebd8/1536901738138/yyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyy.png</image:loc>
      <image:title>New Blog - Spaceship Comets and Highways Through Space</image:title>
      <image:caption>“Each of the hexagons in this figure represents one of the mirror farms shown in [previous image]. The dots are schematic representations of the habitats occupied by each twent-five-member “band.” in reality the habitats would probably be much too small to be seen on this scale.”\(^{[37]}\)</image:caption>
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      <image:title>New Blog - Spaceship Comets and Highways Through Space - Copy of Copy of Starshot Probe</image:title>
      <image:caption>Depiction of a Starshot probe being accellerated by Earth-based lasers. Credit: Breakthrough Starshot</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5c7312bf0d9297df0c46ebd4/1536978228964/pale+blue+dottttttttttttttttttttttttttttttttttttttttttttttttttt.jpg</image:loc>
      <image:title>New Blog - Spaceship Comets and Highways Through Space</image:title>
      <image:caption>In Carl Sagan’s book, Pale Blue Dot, he talked about the possibility of interstellar human communities living in comets in the Kuiper belt, the Oort cloud, and beyond.</image:caption>
    </image:image>
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      <image:title>New Blog - Spaceship Comets and Highways Through Space</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5c7312bf0d9297df0c46ebe0/1538678306195/photosynthesis-process-2.jpg</image:loc>
      <image:title>New Blog - Spaceship Comets and Highways Through Space</image:title>
      <image:caption>The infographic above shows how plants, via the process of photosynethesis, use light (sunlight or artificial light), carbon dioxide and water to produce breathable oxygen.</image:caption>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/outward-bound-2/2018/5/23/star-lifting-colonizing-the-stars-and-the-galaxies-5mjpt</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2019-03-19</lastmod>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/5c9012e5c83025591f884fae/5c9012e5c83025591f884faf/1536791569975/neil-blevins-megastructures-1-ringworld-color-sketch%5B1%5D.jpg</image:loc>
      <image:title>New Blog - Star Lifting: Colonizing the Stars and the Galaxies</image:title>
      <image:caption>Artist’s depiction of a ring world. Artwork by Neil Blevins.</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/5c9012e5c83025591f884fae/5c9012e5c83025591f884fb1/1536791569979/neil-blevins-megastructures-1-ringworld-design-packet%5B1%5D.jpg</image:loc>
      <image:title>New Blog - Star Lifting: Colonizing the Stars and the Galaxies</image:title>
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    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/5c9012e5c83025591f884f8c/5c9012e5c83025591f884f8d/1552959889824/jeremy-jozwik-ia-kuiperbeltterrain-comp2-0084.jpg</image:loc>
      <image:title>New Blog - Star Lifting: Colonizing the Stars and the Galaxies - Kuiper Belt Laser Array</image:title>
      <image:caption>Artist’s impression of an array of lasers built on a comet in the Kuiper Belt. These laser stations would also be built on comets within Oort clouds (not jude our own) and interstellar space to create an interstellar highway. Artwork by Jeremy Jozwik from Artstation who is also a member of the SFIA production team.</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5c9012e5c83025591f884faa/1536791569973/Physics_of_the_future_Kaku_2011%5B1%5D.jpg</image:loc>
      <image:title>New Blog - Star Lifting: Colonizing the Stars and the Galaxies</image:title>
      <image:caption>"Physics of the Future: How Science Will Shape Human Destiny and Our Daily Lives by the Year 2100 is a 2011 book by theoretical physicist Michio Kaku, author of Hyperspace and Physics of the Impossible. In it Kaku speculates about possible future technological development over the next 100 years. He interviews notable scientists about their fields of research and lays out his vision of coming developments in medicine, computing, artificial intelligence, nanotechnology, and energy production. The book was on the New York Times Bestseller List for five weeks."</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5c9012e5c83025591f884fac/1528412559259/star+lifter.jpg</image:loc>
      <image:title>New Blog - Star Lifting: Colonizing the Stars and the Galaxies</image:title>
      <image:caption>Figure 2</image:caption>
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    <image:image>
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      <image:title>New Blog - Star Lifting: Colonizing the Stars and the Galaxies</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5c9012e5c83025591f884fb4/1552852554589/Local_Group_and_nearest_galaxies%5B1%5D.jpg</image:loc>
      <image:title>New Blog - Star Lifting: Colonizing the Stars and the Galaxies</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5c9012e5c83025591f884fa2/1552864521733/Von-Neumann-Probe.jpg</image:loc>
      <image:title>New Blog - Star Lifting: Colonizing the Stars and the Galaxies</image:title>
      <image:caption>Concept art by Mark Molnar</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5c9012e5c83025591f884f94/1552861724343/neil-blevins-megastructures-9-gas-giant-refinery-5.jpg</image:loc>
      <image:title>New Blog - Star Lifting: Colonizing the Stars and the Galaxies</image:title>
      <image:caption>Artist’s depiction of gas giant refineries used to extract materials such as helium-3 and deuterium from the atmosphere of one of the Jovian planets. Artwork by Neil Blevins at Artstation.</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/5c9012e5c83025591f884f96/5c9012e5c83025591f884f97/1552943531025/1080p-Space-Desktop-Background-hd-desktop-wallpapers-cool-images-hd-apple-background-wallpapers-colourfull-free-display-lovely-wallpapers.jpg</image:loc>
      <image:title>New Blog - Star Lifting: Colonizing the Stars and the Galaxies</image:title>
      <image:caption>Image retrieved from: https://thewallpaper.co/preview/?wallpaper=1080p-space-desktop-background-hd-desktop-wallpapers-cool-images-hd-apple-background-wallpapers-colourfull-free-display-lovely-wallpapers-1920x1080</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/5c9012e5c83025591f884f87/5c9012e5c83025591f884f88/1552959875428/neil-blevins-megastructures-7-star-lifter-3d-sketch.jpg</image:loc>
      <image:title>New Blog - Star Lifting: Colonizing the Stars and the Galaxies - Star Lifting</image:title>
      <image:caption>“A star lifter removes mass from a star for either raw materials or to change the nature of the star itself. For example, you may remove mass from the star to collect hydrogen or other elements. Or you could remove mass in order to extend the life of the star, to make the star dimmer, or reduce the chances of a super nova.” Artwork by Neil Blevins from Artstation.</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/5c9012e5c83025591f884fa4/5c9012e5c83025591f884fa5/1536791569970/megastructures_7_star_lifter_3%5B1%5D.jpg</image:loc>
      <image:title>New Blog - Star Lifting: Colonizing the Stars and the Galaxies</image:title>
      <image:caption>Artist’s depiction of a star lifter. Artwork by Neil Blevins.</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5c9012e5c83025591f884f9e/1552862976200/lzlsart9qi311%5B1%5D.jpg</image:loc>
      <image:title>New Blog - Star Lifting: Colonizing the Stars and the Galaxies</image:title>
      <image:caption>Nicoll-Dyson Beam “Unleashing The Nicoll-Dyson Beam from Gigastructural Engineering &amp; More. Inward Perfection has never been so easy when you can delete your enemies Capital systems with the press of a button. Edit: It also has multiple settings. Ranging from reducing all infrastructure to rubble to Solar System Deleter.” Image retrieved from: https://www.reddit.com/r/Stellaris/comments/8qgwe9/fear_me_for_i_am_your_apocalypse/</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/5c9012e5c83025591f884f9a/5c9012e5c83025591f884f9b/1552862368589/neil-blevins-megastructures-12-nicoll-dyson-laser-design-packet.jpg</image:loc>
      <image:title>New Blog - Star Lifting: Colonizing the Stars and the Galaxies</image:title>
      <image:caption>Artist’s depiction of a Nicoll-Dyson Laser. Artwork by Neil Blevins at ArtStation.</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5c9012e5c83025591f884fa8/1528407608550/Star_lifting_1.svg%5B1%5D.png</image:loc>
      <image:title>New Blog - Star Lifting: Colonizing the Stars and the Galaxies</image:title>
      <image:caption>Figure 1: A star lifter would consist of a ring of solar power stations and ion accelerators distributed around a star in the shape of a ring.</image:caption>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/outward-bound-2/string-theory-and-colonizing-the-multiverse-mbzy6</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2019-03-21</lastmod>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5c92fab2e2c48315988ac4a4/1553060486672/matrioshka+brainnnn.png</image:loc>
      <image:title>New Blog - String Theory and Colonizing the Multiverse</image:title>
      <image:caption>“A matrioshka brain is a hypothetical megastructure proposed by Robert Bradbury, based on the Dyson sphere, of immense computational capacity. It is an example of a Class B stellar engine, employing the entire energy output of a star to drive computer systems.”\(^{[2]}\) Image from Steve Bowers</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5c92fab2e2c48315988ac4a2/1553060137245/CERN_LHC%5B1%5D.jpg</image:loc>
      <image:title>New Blog - String Theory and Colonizing the Multiverse</image:title>
      <image:caption>The image above shows a section of the LHC (Large Hadron Collider).</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5c92fab2e2c48315988ac498/1553057433719/four_forces%5B1%5D.jpg</image:loc>
      <image:title>New Blog - String Theory and Colonizing the Multiverse</image:title>
      <image:caption>Image Credit: https://physicswithsampurkis.files.wordpress.com/2014/01/four_forces.jpg</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5c92fab2e2c48315988ac49c/1553058165874/crystal_to_string%5B1%5D.jpg</image:loc>
      <image:title>New Blog - String Theory and Colonizing the Multiverse</image:title>
      <image:caption>The image above shows how various different small objects compare to each other in terms of size. Image retrieved from: http://www.particlecentral.com/strings_page.html</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5c92fab2e2c48315988ac49e/1541982430321/shutterstock_84250684.jpg</image:loc>
      <image:title>New Blog - String Theory and Colonizing the Multiverse</image:title>
      <image:caption>Our universe may be one of many, physicists say. Credit: Shutterstock/Victor Habbick</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/5c92fab2e2c48315988ac492/5c92fab2e2c48315988ac493/1536805148903/gateway_hub_04_by_lorddoomhammer-d9u3226.png</image:loc>
      <image:title>New Blog - String Theory and Colonizing the Multiverse</image:title>
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    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5c92fab2e2c48315988ac496/1552974215990/universeismath.jpg</image:loc>
      <image:title>New Blog - String Theory and Colonizing the Multiverse</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5c92fab2e2c48315988ac49a/1553057859737/calabi-yau7%5B1%5D.gif</image:loc>
      <image:title>New Blog - String Theory and Colonizing the Multiverse</image:title>
      <image:caption>“String Theory predicts the existence of more than the 3 space dimensions and 1 time dimension we are all familiar with. According to string theory, there are additional dimensions that we are unfamiliar with because they are curled up into tiny complicated shapes that can only be seen on tiny scales. If we could shrink to this tiny, Planck-sized scale we could see that at every 3D point in space, we can also explore 6 additional dimensions. This animation shows an array of Calabi-Yau spaces which are projections of these higher dimensions into the more familiar dimensions we are aware of.”\(^{[1]}\)</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5c92fab2e2c48315988ac4a0/1553060002632/LeonardSusskindStanford2009_cropped%5B1%5D.jpg</image:loc>
      <image:title>New Blog - String Theory and Colonizing the Multiverse</image:title>
      <image:caption>Leonard Susskind</image:caption>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/articles-page-12</loc>
    <changefreq>daily</changefreq>
    <priority>0.75</priority>
    <lastmod>2019-03-23</lastmod>
  </url>
  <url>
    <loc>https://www.gregschool.org/articles-page-12/2017/5/23/fundamental-principles-and-postulates-of-quantum-mechanics-5hrka</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-11</lastmod>
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      <image:title>articles page 12 - Fundamental Principles and Postulates of Quantum Mechanics</image:title>
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  </url>
  <url>
    <loc>https://www.gregschool.org/articles-page-12/2017/5/23/measuring-the-spin-of-an-electron-e5rzd</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-11</lastmod>
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      <image:title>articles page 12 - Measuring the Spin of an Electron</image:title>
      <image:caption>Figure 1</image:caption>
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      <image:title>articles page 12 - Measuring the Spin of an Electron</image:title>
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  </url>
  <url>
    <loc>https://www.gregschool.org/articles-page-12/2017/8/29/finding-the-integral-of-kxm-lbzkf</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-09</lastmod>
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      <image:title>articles page 12 - Finding the integral of \(kx^m\)</image:title>
      <image:caption>Figure 1: The area underneath the function \(f(x)=2x\) is simply just the area of a triangle. The base of the triangle is \(x\) and its height is \(f(x)=2x\). Using the formula for the area of a triangle, we find that the area underneath \(f(x)=2x\) is \(x^2\).</image:caption>
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      <image:title>articles page 12 - Finding the integral of \(kx^m\)</image:title>
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  </url>
  <url>
    <loc>https://www.gregschool.org/articles-page-12/2017/3/22/p-series-convergence-and-divergence</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-09</lastmod>
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      <image:title>articles page 12 - P-Series Convergence and Divergence</image:title>
      <image:caption>Figure 1 (click to enlarge)</image:caption>
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      <image:title>articles page 12 - P-Series Convergence and Divergence</image:title>
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      <image:title>articles page 12 - P-Series Convergence and Divergence</image:title>
      <image:caption>Figure 2 (click to enlarge)</image:caption>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/articles-page-12/2017/3/14/exponential-growth-of-information-technology-1</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-09</lastmod>
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      <image:title>articles page 12 - Exponential Growth of Information Technology</image:title>
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      <image:title>articles page 12 - Exponential Growth of Information Technology</image:title>
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      <image:title>articles page 12 - Exponential Growth of Information Technology</image:title>
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      <image:title>articles page 12 - Exponential Growth of Information Technology</image:title>
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      <image:title>articles page 12 - Exponential Growth of Information Technology</image:title>
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  </url>
  <url>
    <loc>https://www.gregschool.org/articles-page-12/2017/2/17/thermodynamics-and-the-arrow-of-time</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-09</lastmod>
  </url>
  <url>
    <loc>https://www.gregschool.org/articles-page-12/2017/3/27/light-fidelity-li-fi-ultra-fast-wireless-communications-system</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-09</lastmod>
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      <image:title>articles page 12 - Light Fidelity (Li-Fi): Ultra-Fast, Wireless Communications System</image:title>
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      <image:title>articles page 12 - Light Fidelity (Li-Fi): Ultra-Fast, Wireless Communications System</image:title>
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      <image:title>articles page 12 - Light Fidelity (Li-Fi): Ultra-Fast, Wireless Communications System</image:title>
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      <image:title>articles page 12 - Light Fidelity (Li-Fi): Ultra-Fast, Wireless Communications System</image:title>
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      <image:title>articles page 12 - Light Fidelity (Li-Fi): Ultra-Fast, Wireless Communications System</image:title>
      <image:caption>Figure 1</image:caption>
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      <image:title>articles page 12 - Light Fidelity (Li-Fi): Ultra-Fast, Wireless Communications System</image:title>
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  </url>
  <url>
    <loc>https://www.gregschool.org/articles-page-12/2017/5/14/spectroscopy-9cnt6</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-11</lastmod>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59af7af446c3c4202e76ee78/1494827814784/</image:loc>
      <image:title>articles page 12 - Spectroscopy</image:title>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/articles-page-12/2017/5/14/surface-of-last-scattering-blnaz</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-11</lastmod>
  </url>
  <url>
    <loc>https://www.gregschool.org/articles-page-12/2017/6/16/formation-of-planets-and-stars-xa5hw</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2017-11-09</lastmod>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/598cd26c46c3c4cee1b81766/1498195845727/</image:loc>
      <image:title>articles page 12 - A Brief Tour of our Milky Way Galaxy</image:title>
      <image:caption>Artist's depiction of the Milky Way Galaxy.</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/598cd26c46c3c4cee1b8176a/1498193304895/</image:loc>
      <image:title>articles page 12 - A Brief Tour of our Milky Way Galaxy</image:title>
      <image:caption>Inferred image of the center of the Milky Way Galaxy. (Source)</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/598cd26c46c3c4cee1b81768/1498157418533/mwpan_aitoff_s.jpg</image:loc>
      <image:title>articles page 12 - A Brief Tour of our Milky Way Galaxy</image:title>
      <image:caption>Picture of the Milky Way Galaxy as seen edge on.</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/598cd26c46c3c4cee1b8176c/1498195183058/430453main_crabmosaic_hst_big_full.jpg</image:loc>
      <image:title>articles page 12 - A Brief Tour of our Milky Way Galaxy</image:title>
      <image:caption>Image of Crab Nebula. (Image credit: NASA)</image:caption>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/clarketech</loc>
    <changefreq>daily</changefreq>
    <priority>0.75</priority>
    <lastmod>2019-03-23</lastmod>
  </url>
  <url>
    <loc>https://www.gregschool.org/clarketech/technological-revolutions-98ybg-esscz</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2019-03-22</lastmod>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5c954eed4192028641aca1bc/1546630127945/</image:loc>
      <image:title>Clarketech - Technological Revolutions</image:title>
      <image:caption>“The Principia states Newton's laws of motion, forming the foundation of classical mechanics; Newton's law of universal gravitation; and a derivation of Kepler's laws of planetary motion (which Kepler first obtained empirically). The Principia is considered one of the most important works in the history of science.”\(^{[5]}\)</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5c954eed4192028641aca1d0/1546553988948/stock-photo-the-train-moving-on-the-overpass-and-the-city-on-the-water-concept-of-modern-transport-futuristic-769589683%5B1%5D.jpg</image:loc>
      <image:title>Clarketech - Technological Revolutions</image:title>
      <image:caption>Arcologies on the surface of the sea could be connected by maglev transportation systems. As we discuss in the article, How to Colonize the Earth?, these sea-steading towers would extend within the depths of the oceans; the cities underneath the sea surface could also be connected by maglev monorail systems. Image Credit: https://www.shutterstock.com/image-illustration/train-moving-on-overpass-city-water-769589683?src=l4eCjvmchovnXUJuJH_WrQ-1-29</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5c954eed4192028641aca1cc/1546462732450/stock-photo-concept-of-magnetic-levitation-train-moving-on-the-sky-way-in-vacuum-tunnel-across-the-city-modern-755107045%5B1%5D.jpg</image:loc>
      <image:title>Clarketech - Technological Revolutions</image:title>
      <image:caption>The image above portrays how large buildings (which could be arcologies that people live in) could be connected by maglev trains operating within evacuated tunnels. Image Credit: https://www.shutterstock.com/image-illustration/concept-magnetic-levitation-train-moving-on-755107045</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5c954eed4192028641aca1c0/1546631010156/Joule%27s_Apparatus_%28Harper%27s_Scan%29%5B1%5D.png</image:loc>
      <image:title>Clarketech - Technological Revolutions</image:title>
      <image:caption>“Engraving of James Joule's apparatus for measuring the mechanical equivalent of heat, in which altitude potential energy from the weight on the right is converted into heat at the left, through stirring of water.”\(^{[7]}\)</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5c954eed4192028641aca1ce/1546462673761/furureofcities1%5B1%5D.jpg</image:loc>
      <image:title>Clarketech - Technological Revolutions</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5c954eed4192028641aca1ac/1546556387544/Life-expectancy-GDP-capita.png</image:loc>
      <image:title>Clarketech - Technological Revolutions</image:title>
      <image:caption>This graph illustrates the increase in standards of living and life expectancy that occurred during the time of the first two industrial revolutions.\(^{[3]}\)</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5c954eed4192028641aca1ba/1546628848879/shopping%5B2%5D.jpg</image:loc>
      <image:title>Clarketech - Technological Revolutions</image:title>
      <image:caption>In the book, Life 3.0, the cosmologist and AI researcher Max Tegmark explores the implications of AI and robotics.</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5c954eed4192028641aca1ca/1546635697448/Meissner_effect_p1390048%5B1%5D.jpg</image:loc>
      <image:title>Clarketech - Technological Revolutions</image:title>
      <image:caption>“A magnet levitating above a high-temperature superconductor, cooled with liquid nitrogen. Persistent electric current flows on the surface of the superconductor, acting to exclude the magnetic field of the magnet (Faraday's law of induction). This current effectively forms an electromagnet that repels the magnet.” Image source: https://en.wikipedia.org/wiki/Superconductivity#/media/File:Meissner_effect_p1390048.jpg</image:caption>
    </image:image>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5c954eed4192028641aca1c8/1546635037806/superconductors.png</image:loc>
      <image:title>Clarketech - Technological Revolutions</image:title>
      <image:caption>The following graph reflects the empirical fact that as time has progressed, we have achieved superconductivity at higher and higher temperatures. Credit: Pia Jensen Ray</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/5c954eed4192028641aca1b0/5c954eed4192028641aca1b1/1546626382657/Artificial-Intelligence-2%5B1%5D.jpg</image:loc>
      <image:title>Clarketech - Technological Revolutions</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5c954eed4192028641aca1be/1546630451461/Newtons_laws_in_latin%5B1%5D.jpg</image:loc>
      <image:title>Clarketech - Technological Revolutions</image:title>
      <image:caption>“Newton's First and Second laws, in Latin, from the original 1687 Principia Mathematica”\(^{[6]}\)</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/5c954eed4192028641aca1b6/5c954eed4192028641aca1b7/1546627071014/392448062_orig%5B1%5D.jpg</image:loc>
      <image:title>Clarketech - Technological Revolutions</image:title>
      <image:caption>Artist’s depiction of nanobots patroling the human bloodstream. Image retrieved from: https://www.cnet.com/news/nanobots-can-now-swarm-like-fish-to-perform-complex-medical-tasks/</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5c954eed4192028641aca1aa/1546556065103/Maler_der_Grabkammer_des_Sennudem_001.jpg</image:loc>
      <image:title>Clarketech - Technological Revolutions</image:title>
      <image:caption>“Ploughing with a yoke of horned cattle in Ancient Egypt. Painting from the burial chamber of Sennedjem, c. 1200 BC.”\(^{[2]}\)</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5c954eed4192028641aca1c2/1546631734569/Newcomens_Dampfmaschine_aus_Meyers_1890%5B1%5D.png</image:loc>
      <image:title>Clarketech - Technological Revolutions</image:title>
      <image:caption>“Newcomen's steam-powered atmospheric engine was the first practical piston steam engine. Subsequent steam engines were to power the Industrial Revolution.”\(^{[7]}\)</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5c954eed4192028641aca1ae/1546556994722/Ending_Aging%5B1%5D.jpg</image:loc>
      <image:title>Clarketech - Technological Revolutions</image:title>
      <image:caption>Credit: https://en.wikipedia.org/wiki/File:Ending_Aging.jpg</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5c954eed4192028641aca1b4/1546626649805/Moore%27s_Law_Transistor_Count_1971-2016%5B1%5D.png</image:loc>
      <image:title>Clarketech - Technological Revolutions</image:title>
      <image:caption>A plot of CPU transistor counts against dates of introduction. Source URL: https://commons.wikimedia.org/wiki/File:Moore%27s_Law_Transistor_Count_1971-2016.png</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5c954eed4192028641aca1a8/1546555589793/</image:loc>
      <image:title>Clarketech - Technological Revolutions</image:title>
      <image:caption>“Smithsonian scientists and their Chinese colleagues found this and other handaxes in the same sediment layer with tektites, small rocks that formed during a meteor impact 803,000 years ago. Since the handaxes and tektites were in the same layer, both are the same age. Early humans must have moved into the area right after the impact. They may have made the handaxes from rocks that were exposed when forests burned.”\(^{[1]}\) Image Credit: James Di Loreto, &amp; Donald H. Hurlbert, Smithsonian Institution</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/5c954eed4192028641aca1c4/5c954eed4192028641aca1c5/1546632086035/Bane-Boon-1280x640%5B1%5D.jpg</image:loc>
      <image:title>Clarketech - Technological Revolutions</image:title>
      <image:caption>Image retrieved from: https://iconshots.com/concept/the-future-of-technology-should-we-be-worried/</image:caption>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/clarketech/robots-and-their-uses-br26w-dpmrl</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2019-03-23</lastmod>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5c954f03ec212d705142e85f/1545767693610/any-sufficiently-advanced-technology-is-indistinguishable-from-magic-arthur-c-14468433.png</image:loc>
      <image:title>Clarketech - Robots and their Uses</image:title>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/5c954f03ec212d705142e857/5c954f03ec212d705142e858/1545767693602/iStock-660606914-804x1024%5B1%5D.jpg</image:loc>
      <image:title>Clarketech - Robots and their Uses</image:title>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/5c954f03ec212d705142e84f/5c954f03ec212d705142e850/1545767693595/luis-dourado-670d7641531557-57a9f2970415e.jpg</image:loc>
      <image:title>Clarketech - Robots and their Uses</image:title>
      <image:caption>https://www.artstation.com/artwork/YxRbq</image:caption>
    </image:image>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/5c954f03ec212d705142e84b/5c954f03ec212d705142e84c/1545767693571/neil-blevins-inc-the-robot-14-textured-poses1%5B1%5D.jpg</image:loc>
      <image:title>Clarketech - Robots and their Uses</image:title>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5c954f03ec212d705142e85d/1545767693608/if-you-could-visualize-grahams-curiosity-number-your-head-would-6200771.png</image:loc>
      <image:title>Clarketech - Robots and their Uses</image:title>
      <image:caption>https://me.me/i/if-you-could-visualize-grahams-curiosity-number-your-head-would-3896085</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/5c954f03ec212d705142e847/5c954f03ec212d705142e848/1545767693565/524246%5B1%5D.jpg</image:loc>
      <image:title>Clarketech - Robots and their Uses</image:title>
      <image:caption>Image retrieved from: https://wall.alphacoders.com/big.php?i=524246</image:caption>
    </image:image>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/5c954f03ec212d705142e853/5c954f03ec212d705142e854/1545767693598/arcologies.jpg</image:loc>
      <image:title>Clarketech - Robots and their Uses</image:title>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5c954f03ec212d705142e85b/1545767693606/Atlas_from_boston_dynamics%5B1%5D.jpg</image:loc>
      <image:title>Clarketech - Robots and their Uses</image:title>
      <image:caption>Atlas from Boston Dynamics</image:caption>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/clarketech/utopia-life-in-the-year-2100-4e9ga-y24xn</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2019-03-23</lastmod>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5c954f160852293821458b93/1553277163807/Neolithic-revolution-ancient-farmers.jpg</image:loc>
      <image:title>Clarketech - Utopia: Life in the Year 2100</image:title>
      <image:caption>The Neolithic Revolution (which began, independently, in multiple different civilization 10 to 12 thousand years ago) occurred when, for the first time, we humans began to domesticate plants and animals.</image:caption>
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    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/5c954f160852293821458b97/5c954f160852293821458b98/1544066498793/524246%5B1%5D.jpg</image:loc>
      <image:title>Clarketech - Utopia: Life in the Year 2100</image:title>
      <image:caption>Image retrieved from: https://wall.alphacoders.com/big.php?i=524246</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/5c954f160852293821458b9f/5c954f160852293821458ba2/1546461550632/The-Venus-Project-Restaurant-889x544%5B1%5D.jpg</image:loc>
      <image:title>Clarketech - Utopia: Life in the Year 2100</image:title>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/5c954f160852293821458b9f/5c954f160852293821458ba0/1546461550188/The-Venus-Project-Design-889x500%5B1%5D.jpg</image:loc>
      <image:title>Clarketech - Utopia: Life in the Year 2100</image:title>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/5c954f160852293821458b9f/5c954f160852293821458ba6/1546461554396/The-Venus-Project-Buildings-889x493%5B1%5D.jpg</image:loc>
      <image:title>Clarketech - Utopia: Life in the Year 2100</image:title>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/5c954f160852293821458b9f/5c954f160852293821458ba4/1546461550216/The-Venus-Project-Architecture-1-889x500%5B1%5D.jpg</image:loc>
      <image:title>Clarketech - Utopia: Life in the Year 2100</image:title>
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    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5c954f160852293821458bad/1546234016988/large_-085MyVwIWu7CejYdKdZJ_6R-zaYCURcCPnuQyPhrbA.jpg</image:loc>
      <image:title>Clarketech - Utopia: Life in the Year 2100</image:title>
      <image:caption>”Flipping good ... the Japanese cuisine machine hasn't dropped a pancake yet.”\(^{[3]}\) Image: Huis Ten Bosch/Facebook</image:caption>
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    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5c954f160852293821458b8f/1553148030627/Diorama%2C_cavemen_-_National_Museum_of_Mongolian_History%5B1%5D.jpg</image:loc>
      <image:title>Clarketech - Utopia: Life in the Year 2100</image:title>
      <image:caption>“A diorama showing Homo erectus, the earliest human species that is known to have controlled fire, from inside the National Museum of Mongolian History in Ulaanbaatar, Mongolia.”\(^{[1]}\)</image:caption>
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    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5c954f160852293821458bab/1546233660364/11908915_472363736276164_3837059669263559235_o%5B1%5D.jpg</image:loc>
      <image:title>Clarketech - Utopia: Life in the Year 2100</image:title>
      <image:caption>Image (click to enlarge) of lab-grown meat.</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/5c954f160852293821458baf/5c954f160852293821458bb0/1544408785580/benjamin-parker-fleetovermiranda-render-wip.jpg</image:loc>
      <image:title>Clarketech - Utopia: Life in the Year 2100</image:title>
      <image:caption>“Civilians watch a small fleet orbit around Uranus' moon Miranda.” Credit: https://www.artstation.com/artwork/mqZVx9</image:caption>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/5c954f160852293821458baf/5c954f160852293821458bb2/1544408724395/benjamin-parker-fleetovermiranda-render-k.jpg</image:loc>
      <image:title>Clarketech - Utopia: Life in the Year 2100</image:title>
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    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/5c954f160852293821458bb5/5c954f160852293821458bba/1553278214216/WANDERERS_verona_rupes_01%5B1%5D.jpg</image:loc>
      <image:title>Clarketech - Utopia: Life in the Year 2100</image:title>
      <image:caption>“Base jumping off the tallest cliff in the Solar System, located on Uranus' moon Miranda. Uranus itself, along with a few other moons (from the top left to bottom right: Ariel (here on the far side of Uranus), Belinda, Puck and Portia) are seen in the background of the last shot. On Uranus´small moon Miranda lies a monumental cliff wall believed to be the tallest in the Solar System. It is called Verona Rupes. Observations are limited but it is certain that the cliffs rise at least 5 kilometers above the ground below. Maybe even twice as much. This extreme height combined with Miranda´s low gravity (0,018g) would make for a spectacular base-jump. After taking the leap from the top edge you could fall for at least 12 minutes and, with the help of a small rocket to brake your fall toward the bottom, end up landing safely on your feet. Miranda´s close orbit around giant Uranus also makes a magnificent huge cyan ball in the sky. The scene is built mostly in CG, except for the people who are shot live action and composited into the environment, and the foreground cliffs in the first shot which are made from several photos of a place in Norway known as "The Pulpit Rock". For building the landscape I used (amongst others) this satellite photo of Verona Rupes, taken by NASAs Voyager 2 during the flyby of Uranus in 1986. For the color and texture of Uranus I used this photo as reference. Also by Voyager 2, NASA.”\({[4]}\) Source: http://www.erikwernquist.com/wanderers/gallery_verona_rupes.html</image:caption>
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      <image:title>Clarketech - Utopia: Life in the Year 2100</image:title>
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      <image:title>Clarketech - Utopia: Life in the Year 2100</image:title>
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      <image:title>Clarketech - Utopia: Life in the Year 2100</image:title>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5c954f160852293821458b91/1553148746362/goddardtsiolkovsky%5B1%5D.jpg</image:loc>
      <image:title>Clarketech - Utopia: Life in the Year 2100</image:title>
      <image:caption>Photographs of the two pioneers of rocketry science, Konstantin Tsiolkovsky (left) and Robert Goddard (right).</image:caption>
    </image:image>
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      <image:title>Clarketech - Utopia: Life in the Year 2100</image:title>
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      <image:title>Clarketech - Utopia: Life in the Year 2100</image:title>
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      <image:title>Clarketech - Utopia: Life in the Year 2100</image:title>
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      <image:title>Clarketech - Utopia: Life in the Year 2100</image:title>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5c954f160852293821458b95/1544143467767/8a6f20acd6bb4d346443d8872dec9649.jpg</image:loc>
      <image:title>Clarketech - Utopia: Life in the Year 2100</image:title>
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    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/5c954f160852293821458b89/5c954f160852293821458b8a/1546230084517/1*ekxLnZoSewL3p7pVUrMEhQ.jpeg</image:loc>
      <image:title>Clarketech - Utopia: Life in the Year 2100</image:title>
      <image:caption>Robert McCall, “The Prologue and the Promise”</image:caption>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/clarketech/super-intelligence-rise-of-the-machines-btkn7-kghy3</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2019-03-23</lastmod>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5c954f2c8165f590a8d04f22/1543768690328/1541094406003-Untitled%5B1%5D.jpg</image:loc>
      <image:title>Clarketech - Super Intelligence: Rise of the Machines</image:title>
      <image:caption>An example environment fed to the AI physicist. Here, the field of view is divided into four quadrants, each of which is governed by a different physical effect, such as gravity or an electromagnetic field. The dots and lines represent the ball’s trajectory through the environment. Based on how a ball moves through the environment, the AI must use the strategies it was given to describe the physical laws that are governing the ball’s motion. Image: Tegmark and Wu/arXiv</image:caption>
    </image:image>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5c954f2c8165f590a8d04f18/1543709737491/Knowledge%252520Timeline%5B1%5D.gif</image:loc>
      <image:title>Clarketech - Super Intelligence: Rise of the Machines</image:title>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5c954f2c8165f590a8d04f1e/1543713651396/staircase2%5B1%5D.png</image:loc>
      <image:title>Clarketech - Super Intelligence: Rise of the Machines</image:title>
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      <image:title>Clarketech - Super Intelligence: Rise of the Machines</image:title>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5c954f2c8165f590a8d04f24/1543769327376/central+dome+super+computer.jpg</image:loc>
      <image:title>Clarketech - Super Intelligence: Rise of the Machines</image:title>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5c954f2c8165f590a8d04f20/1543714992397/1541094535342-shutterstock_680929729%5B1%5D.jpg</image:loc>
      <image:title>Clarketech - Super Intelligence: Rise of the Machines</image:title>
    </image:image>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5c954f2c8165f590a8d04f12/1543701465710/lg-airport-robot-9.jpg</image:loc>
      <image:title>Clarketech - Super Intelligence: Rise of the Machines</image:title>
      <image:caption>The two robots above help clean the floor and give directions to passengers at the Seoul-Incheon International Airport.</image:caption>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5c954f2c8165f590a8d04f16/1543709544581/TrainingTime-Graph-171019-r01%5B1%5D.gif</image:loc>
      <image:title>Clarketech - Super Intelligence: Rise of the Machines</image:title>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5c954f2c8165f590a8d04f1c/1543713631011/staircase1%5B1%5D.png</image:loc>
      <image:title>Clarketech - Super Intelligence: Rise of the Machines</image:title>
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    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5c954f2c8165f590a8d04f1a/1543711783089/tumblr_inline_p95ps0lvcV1scxxly_500%5B1%5D.png</image:loc>
      <image:title>Clarketech - Super Intelligence: Rise of the Machines</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/5c954f2c8165f590a8d04f0e/5c954f2c8165f590a8d04f0f/1543700155460/androids%5B1%5D.jpg</image:loc>
      <image:title>Clarketech - Super Intelligence: Rise of the Machines</image:title>
      <image:caption>Cover art from the Sci-Fi Masterworks edition of Do Androids Dream of Electric Sheep?</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5c954f2c8165f590a8d04f14/1543712186611/how-intelligent-will-aI-get-3%5B1%5D.jpg</image:loc>
      <image:title>Clarketech - Super Intelligence: Rise of the Machines</image:title>
      <image:caption>Infographic source: https://www.huawei.com/en/about-huawei/publications/winwin-magazine/ai/how-intelligent-will-ai-get</image:caption>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/clarketech/2017/1/23/superconductors-the-future-of-transportation-and-electric-transmission-d5e6r-ancwd</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2019-03-23</lastmod>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5c9587eb5bfa3f0001d2cd19/1509744676939/</image:loc>
      <image:title>Clarketech - Superconductors: the Future of Transportation and Electric Transmission</image:title>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5c9587eb5bfa3f0001d2cd2b/1509744812574/twiiter+img+thumbnail.jpg</image:loc>
      <image:title>Clarketech - Superconductors: the Future of Transportation and Electric Transmission</image:title>
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    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5c9587eb5bfa3f0001d2cd31/1509744531017/technology+thumbnail.png</image:loc>
      <image:title>Clarketech - Superconductors: the Future of Transportation and Electric Transmission</image:title>
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    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5c9587eb5bfa3f0001d2cd2d/1509744847045/</image:loc>
      <image:title>Clarketech - Superconductors: the Future of Transportation and Electric Transmission</image:title>
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      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5c9587eb5bfa3f0001d2cd29/1509744831827/facebook+img+thumbnail.jpg</image:loc>
      <image:title>Clarketech - Superconductors: the Future of Transportation and Electric Transmission</image:title>
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    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5c9587eb5bfa3f0001d2cd2f/1509744550746/email+img+thumbnail.jpg</image:loc>
      <image:title>Clarketech - Superconductors: the Future of Transportation and Electric Transmission</image:title>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/clarketech/2017/8/21/our-future-as-cyborgs-lfz6p-2rlfh</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2019-03-23</lastmod>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5c95882a53450a28e41da975/1510175161926/technology+thumbnail.png</image:loc>
      <image:title>Clarketech - Our Future as Cyborgs</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5c95882a53450a28e41da979/1510175161930/04-17-Asimo-Grand-Marshall-HIGPA%5B1%5D.jpg</image:loc>
      <image:title>Clarketech - Our Future as Cyborgs</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5c95882a53450a28e41da96d/1510250950786/facebook+img+thumbnail.jpg</image:loc>
      <image:title>Clarketech - Our Future as Cyborgs</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5c95882a53450a28e41da977/1510175161928/bionic_v2.png</image:loc>
      <image:title>Clarketech - Our Future as Cyborgs</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5c95882a53450a28e41da973/1510249455185/email+img+thumbnail.jpg</image:loc>
      <image:title>Clarketech - Our Future as Cyborgs</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5c95882a53450a28e41da96f/1510250935466/twiiter+img+thumbnail.jpg</image:loc>
      <image:title>Clarketech - Our Future as Cyborgs</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5c95882a53450a28e41da96b/1510175161916/share+technology++img.jpg</image:loc>
      <image:title>Clarketech - Our Future as Cyborgs</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5c95882a53450a28e41da971/1510250972172/google+img+thumbnail.jpg</image:loc>
      <image:title>Clarketech - Our Future as Cyborgs</image:title>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/clarketech/2017/3/27/light-fidelity-li-fi-ultra-fast-wireless-communications-system-49mxf-lleef</loc>
    <changefreq>monthly</changefreq>
    <priority>0.5</priority>
    <lastmod>2019-03-23</lastmod>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5c95886ef9619a337b767765/1509744407032/twiiter+img+thumbnail.jpg</image:loc>
      <image:title>Clarketech - Light Fidelity (Li-Fi): Ultra-Fast, Wireless Communications System</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5c95886ef9619a337b76776d/1490641020901/</image:loc>
      <image:title>Clarketech - Light Fidelity (Li-Fi): Ultra-Fast, Wireless Communications System</image:title>
      <image:caption>Figure 1</image:caption>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5c95886ef9619a337b767762/1509744439536/facebook+img+thumbnail.jpg</image:loc>
      <image:title>Clarketech - Light Fidelity (Li-Fi): Ultra-Fast, Wireless Communications System</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5c95886ef9619a337b767769/1509744154145/email+img+thumbnail.jpg</image:loc>
      <image:title>Clarketech - Light Fidelity (Li-Fi): Ultra-Fast, Wireless Communications System</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5c95886ef9619a337b767760/1509744247982/share+technology++img.jpg</image:loc>
      <image:title>Clarketech - Light Fidelity (Li-Fi): Ultra-Fast, Wireless Communications System</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5c95886ef9619a337b767767/1509744456561/google+img+thumbnail.jpg</image:loc>
      <image:title>Clarketech - Light Fidelity (Li-Fi): Ultra-Fast, Wireless Communications System</image:title>
    </image:image>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/5c95886ef9619a337b76776b/1509744129041/technology+thumbnail.png</image:loc>
      <image:title>Clarketech - Light Fidelity (Li-Fi): Ultra-Fast, Wireless Communications System</image:title>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/about</loc>
    <changefreq>daily</changefreq>
    <priority>0.75</priority>
    <lastmod>2019-03-20</lastmod>
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      <image:title>About</image:title>
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  </url>
  <url>
    <loc>https://www.gregschool.org/courses</loc>
    <changefreq>daily</changefreq>
    <priority>1.0</priority>
    <lastmod>2018-09-05</lastmod>
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      <image:title>Home - Classical Mechanics</image:title>
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      <image:title>Home - Electromagnetism</image:title>
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      <image:title>Home - Calculus</image:title>
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      <image:title>Home - Quantum Mechanics</image:title>
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      <image:title>Home - Special &amp; General Relativity</image:title>
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      <image:title>Home</image:title>
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  </url>
  <url>
    <loc>https://www.gregschool.org/cosmology-lecture</loc>
    <changefreq>daily</changefreq>
    <priority>0.75</priority>
    <lastmod>2017-08-10</lastmod>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59ffad99c83025d8b0071344/1509928346518/qFGguzj%5B1%5D.jpg</image:loc>
      <image:title>Astronomy &amp; Cosmology Lecture</image:title>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/quantum-mechanics-lecture</loc>
    <changefreq>daily</changefreq>
    <priority>0.75</priority>
    <lastmod>2017-05-23</lastmod>
  </url>
  <url>
    <loc>https://www.gregschool.org/special-relativity-lecture</loc>
    <changefreq>daily</changefreq>
    <priority>0.75</priority>
    <lastmod>2017-08-10</lastmod>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59ffad1e64265f6a4036062f/1509928226360/grmontage%5B1%5D.jpg</image:loc>
      <image:title>Special &amp; General Relativity Lecture</image:title>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/classical-mechanics-lecture</loc>
    <changefreq>daily</changefreq>
    <priority>0.75</priority>
    <lastmod>2017-11-02</lastmod>
    <image:image>
      <image:loc>https://static1.squarespace.com/static/58757ed7f5e231cc32494a1b/t/59ffabd69140b72e250fb334/1509927897026/sackler%2520physics%2520cropped%5B1%5D.jpg</image:loc>
      <image:title>Classical Mechanics Lecture</image:title>
    </image:image>
  </url>
  <url>
    <loc>https://www.gregschool.org/electromagnetism-lecture</loc>
    <changefreq>daily</changefreq>
    <priority>0.75</priority>
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