The purpose of describing planetary orbits in terms of epicycles and deferents was to account for the
A) fact that a planet's speed in its orbit is fastest when it is closest to the Sun.
B) pattern of alternating conjunctions and oppositions.
C) pattern of alternating direct and retrograde motion.
D) general motion of all objects toward the west in the sky each day.

Question

Quizplus · Accepted Answer

The concept of epicycles and deferents was primarily used in the Ptolemaic system to explain the apparent retrograde motion of the planets. This system posited that planets move in small circles called epicycles, which in turn move along larger circles called deferents. This model was able to account for the observed backward, or retrograde, motion of planets as seen from Earth.

The Purpose of Describing Planetary Orbits in Terms of Epicycles