Question

Which is a correct statement about Aristotle's and Ptolemy's models of the solar system?
Responses

Ptolemy's model involved epicycles moving along perfect circles.
Ptolemy's model involved epicycles moving along perfect circles. - no response given

Aristotle's model involved epicycles moving within crystalline spheres.
Aristotle's model involved epicycles moving within crystalline spheres. - no response given

Ptolemy's model was never useful because it was incorrect.
Ptolemy's model was never useful because it was incorrect. - no response given

Aristotle's model put the Sun at the center.

Answer 1

"Ptolemy's model involved epicycles moving along perfect circles." — Correct.

Briefly:
- Ptolemy used deferents and epicycles (circles-on-circles) — with the additional device of the equant to match observations.
- Aristotle posited nested crystalline (solid) spheres carrying the planets, not epicycles.
- Ptolemy's model was very useful for predicting planetary positions for many centuries despite being physically incorrect.
- Aristotle's model was geocentric, with Earth at the center, not the Sun.