Final answer:
Ptolemy's model of the universe was distinct from Aristotle's due to the introduction of epicycles and the equant point to better match celestial observations while still maintaining Earth at the center.
Step-by-step explanation:
The Ptolemaic model and Aristotle's model of the universe both placed Earth at the center, a view known as geocentric. However, Ptolemy's version differed because it introduced the concept of epicycles, smaller circles in which the planets moved while simultaneously being attached to larger spheres or deferent circles revolving around Earth. This was an attempt to account for the irregularities observed in the celestial motions. In contrast, Aristotle's model was less complex, featuring uniform circular motions centered directly on Earth without the additional complexity of epicycles.
To precisely match the observed movements of the planets, Ptolemy also introduced the concept of an equant point, a point away from Earth around which planets would exhibit uniform circular motion, complicating the model even further. Ptolemy's geocentric model was descriptive and, though complex, was considered an achievement at the time, encapsulating the motions of celestial bodies without explaining their causation. In essence, Ptolemy was attempting to preserve the Greek belief in perfect circular celestial motions while accounting for observational discrepancies.