A fatal flaw with Ptolemy's model is its inability to predict the observed phases of:
A)the Sun during an eclipse.
B)the Moon in its monthly cycle.
C)Mercury and Venus.
D)Mars and Jupiter.
E)Jupiter and Saturn.

Question

Quizplus · Accepted Answer

Ptolemy's model assumed that Mercury and Venus revolved around the Earth in perfect circles, always appearing close to the Sun in the sky. However, both Mercury and Venus exhibit phases similar to the Moon's phases, which cannot be explained by a model in which they orbit the Earth. Ptolemy's model was able to predict the phases of the Moon, but it failed to accurately predict the phases of the inner planets, Mercury and Venus. This was because Ptolemy believed that these planets orbited around the Earth, but also had their own small orbit around a point on the line connecting the Earth to the Sun (known as the epicycle). This resulted in their phases appearing differently than predicted by the model.

A Fatal Flaw with Ptolemy's Model Is Its Inability to Predict