What problem with the geocentric model led Ptolemy to invent epicycles?
A)prograde motion
B)retrograde motion
C)ecliptic motion
D)eclipse motion

Question

Quizplus · Accepted Answer

Retrograde motion refers to the apparent backwards motion of planets in the sky. This was a problem for the geocentric model (which had all celestial bodies orbiting the Earth) because it didn't fit with the idea that all motion in the universe should be uniform and circular. Ptolemy invented epicycles to try and explain this phenomenon.

What Problem with the Geocentric Model Led Ptolemy to Invent