The Universe was geocentric (earth-centered) and based on uniform circular motion. To create the proper motion of the planets (changing speed, retrograde motion), he put the planets on smaller epicycles. Note that the position of Mercury and Venus on the Deferent was restricted to the Earth - Sun line of sight. The distant stars were fixed upon the outer most sphere of the heavens.
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to see how such a model can explain retrograde motion..
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The Copernican Model
The Universe was heliocentric (Sun-centered).
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to see how such a model can explain retrograde motion..
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