Was the Ptolemaic model geo- or heliocentric? Explain. How did Ptolemy and others before him account for retrograde motion (epicycle and deferent)? What is the most basic explanation for why this complicated theory could not possibly be correct?
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The Ptolemaic model was geocentric, with the Earth in the center of the solar system and all other known planetary bodies orbiting around it, including the Sun.
Normally, planets move from west to east against the "fixed" background of stars. Retrograde motion is characteristic of planets. It is a backwards motion against the background of stars, movement from east to west. To account for retrograde motion in his model, Ptolemy created the idea of epicycles. Epicycles were a circular orbit of a planet around a fixed ...
In this solution, I discuss the Ptolemaic Model of the Solar System, how he accounted for retrograde motion, as well as its faults and the reasoning behind them.