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's and Venus's 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 to account for the retrograde motion of planets, which appeared to move backwards in the night sky at certain times.

The Purpose of Using Epicycles and Deferents to Explain the Motion