Chapter 2 -- Astronomy - GEO 1013 THE THIRD PLANET E. R....

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GEO 1013 – THE THIRD PLANET E. R. SWANSON – SPRING 2009 OUR PLACE IN SPACE: ASTRONOMY AND THE UNIVERSE The 3rd Planet from the Sun Put in your mind’s eye that classic view of the full Earth taken by the Apollo astronauts. I am talking about the view showing the bright blue, third planet from the sun, blanketed in its protective atmosphere, mostly covered with water and literally teaming with life. Among the many millions of life forms is one of particular distinction, us! (Well, that is our opinion at least) Now let's shift our attention. Imagine miles and miles of warm, sandy beaches stretching to the horizon without a single soul in sight. Now try to imagine how many grains of sand are on that beach. Next try to imagine how many grains of sand exist on all of the beaches of the entire world. There are a lot, but how important then is any single grain? If your answer is that each grain is distinctive, unique, and important you should immediately drop this course, declare your self a geology major and sign up for sandstone geology before the class fills. For most up us, however, it’s "seen one sand grain and you've seen them all". Now make each of those sand grains a planet, like planet Earth for example. The reason for this is that astronomers estimate that there are more stars (and presumably many more planets) in the universe than there are grains of sand on all the beaches of the world. So now is it a case of, "seen one planet and you've seen them all"? The answer, for most folks, is probably still yes because we really don’t get out that much. Except for a couple of folks who spent a few days on our nearest neighbor, the Moon, our entire history and everything that humans have ever known has taken place on that one insignificant grain. It should not be surprising then that in the absence of any comprehensive knowledge of the size of the universe, folks conclude that we are pretty much it. That certainly is the way it was for the ancients. To them, the universe consisted of our big world (Earth) orbited by two lesser, lifeless worlds [one hot (Sun) and one cold (Moon)] and by many small cold dots of light in the sky (stars and planets). The universe seems centered on us and so the reason for it existing must be us, top of the food chain, significant almost beyond measure. Guess who came up with that idea? The history of astronomy parallels one of the great stories of western civilization, a story that included one of the greatest paradigm shifts of all history, a story taking 2,000 years to complete and one with a happy ending. It is an episode in history that gave birth to modern science and which popularized the notion that we live in a rational universe governed by laws of nature. It is a story involving something so simple and yet so fundamental as trying to understand where exactly is “our place in space”. Ancient Astronomy - Greek Geeks
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Chapter 2 -- Astronomy - GEO 1013 THE THIRD PLANET E. R....

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