The purpose of using epicycles and deferents to explain the motion of the planets in the night sky was to account for
A) prograde motion.
B) Mercury and Venus' limited angular distance from the Sun.
C) retrograde motion.
D) non-uniform speed of the planets in their orbits.
E) precession of the equinoxes.

Question

Quizplus · Accepted Answer

Epicycles and deferents were used in the Ptolemaic system to explain the apparent retrograde motion of planets, where they appear to move backward in the sky.

The Purpose of Using Epicycles and Deferents to Explain the Motion