What was ptolemy trying to explain in his model by having the planets move on smaller circles that move onbigger circles?

Ptolemy's model, known as the geocentric system, aimed to explain the complex movements of planets, particularly their retrograde motion, using a series of circles. By proposing that planets moved on smaller circles called epicycles, which in turn moved along larger circles (deferents), he sought to account for the observed irregularities in their paths while maintaining the Earth at the center of the universe. This intricate system allowed for more accurate predictions of planetary positions, reflecting the astronomical knowledge of his time.