Ptolemy’s model of the solar system explained the apparent changes in speed and direction of the planets primarily through the use of C. The planets spun on epicycles.
In Ptolemy's geocentric model, each planet was thought to move in a small circle (an epicycle) while simultaneously moving along a larger circle (the deferent) around the Earth. This complex system of circular motions was designed to account for the observed retrograde motion of planets, as well as their varying speeds as seen from Earth.
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