How can planet retrograde motion be explained by the Earth-center hypothesis By the Sun-center hypothesis?
In the Heliocentric Hypothesis (Sun-centered), retrograde motion is described as changes in relative motion as the Earth overtakes a slower-moving planet in an outer orbit, or is overtaken by a faster-moving planet in an inner orbit. In the Heliocentric Hypothesis, all planets move in more-or-less circular orbits at more-or-less constant speeds, but planets closer to the Sun move faster. Thus, the Earth can overtake and pass each of the outer planets, making them appear to move “backward” (retrograde) for a time.
