Why did Ptolemy have the planets orbiting Earth on "circles upon circles" in his model of the universe?
A)to explain why more distant planets take longer to make a circuit through the constellations of the zodiac
B)to explain the fact that planets sometimes appear to move westward,rather than eastward,relative to the stars in our sky
C)to explain why the Greeks were unable to detect stellar parallax
D)to properly account for the varying distances of the planets from Earth
E)to explain why Venus goes through phases as seen from Earth

Question

Quizplus · Accepted Answer

Ptolemy's model, with its epicycles (circles upon circles), was designed to account for the apparent retrograde motion of the planets, where they sometimes appear to move westward rather than eastward relative to the stars. This was a key feature his model needed to explain to match observations without abandoning the geocentric worldview.

Why Did Ptolemy Have the Planets Orbiting Earth on "Circles