In the Ptolemaic model, retrograde motion is due to
A) relative motion between the Earth and another planet in its orbit
B) the Earth reversing the direction of its orbit about the Sun
C) a planet moving backwards in its smaller circular circle, the center of which moves in a larger circular orbit around the Earth
D) a planet reversing the direction of its orbit about the Sun

Question

Quizplus · Accepted Answer

In the Ptolemaic model, retrograde motion is explained by the planet moving backwards in its smaller circular circle, the center of which moves in a larger circular orbit around the Earth. This is known as the deferent and epicycle model.

In the Ptolemaic Model, Retrograde Motion Is Due to