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ASTR 1101 The Solar System Gravitation Waltz Of Plan.doc

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ASTR 1101
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Gravitation and the Waltz of the Planets1Models of the UniverseaThe Geocentric model was the Greek model in which they thought the earth was the center of everythingiEverything would revolve around the earthiiIt could tell you where the planets would be when the sun would rise et cetera The problem was that Mars goes into retrograde where it appears to move backwards The way they fixed this was that they made a model where the earth was still in the center and they made a perfect circle called an epicycle You would see the planet moving in its circular orbit This would show where the planets were in retrogradebCopernicus came along and said the universe is not that complicatediHe came up with a heliocentric model where the sun was in the center and the planets orbited the sun If one planet was closer to the sun and moved faster then the perception would change appearing in retrogradeiiThe problem was that hey was going along the line that everything was perfect and circular We now know that this is wrongiiiHe ended up having to fall back on epicyclesivWith this heliocentric model he figured out mathematically how far from the sun the planets were They were incredibly close to what we now know are truecTycho BraheiHe was one of the best observers during his period He had unlimited funds from the Dutch government so he got whatever he wanted He observed Parallax1Think of having two eyes and covering one up You see something at a different place relative to the background This is the brains parallax which helps with depth perception2He used this to determine where the planets were This is only good for our solar system3There are baselines which can be observed at different time intervalsiiHe insisted that Earth was the center of the solar system geocentricdJoannis KepleriHe was Tychos assistant and when Tycho died Kepler got everything Kepler was a mathematician and did things in terms of geometryiiHe used Tychos data1First Law all planets orbit in ellipses not circles The sun is at one of the foci represented by letter e The axis
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