Question

The geocentric model could not explain which of the following observations made by earlier astronomers select the two correct answers the planets had epicycles the Stars appeared to move Mercury and Venus changed in appearance throughout the year Mars and Jupiter appeared to move backwards for some period of time

Answer 1

The geocentric model struggled to explain the following two observations made by earlier astronomers:

1. **The planets had epicycles** - While the geocentric model included epicycles to explain the retrograde motion of planets, the complexity and arbitrary nature of these additions were problematic and did not provide a satisfactory explanation.

2. **Mars and Jupiter appeared to move backwards for some period of time** - This retrograde motion of planets was difficult to reconcile with a strictly geocentric view, leading to the need for complicated explanations involving epicycles.

The other two options, regarding the stars moving and Mercury and Venus changing appearance, were somewhat accommodated within the geocentric framework but did not challenge the model in the same fundamental way as the other two points.