The Ptolemaic explanation derives from a model that captures little of the physical reality of the solar system. Unlike the Ptolemaic model, Copernican model represents the solar system as a proper system. The Ptolemaic model held that everything (including the sun) revolves around the Earth, a special object in the model
Because Copernicus imposed uniform circular motion on his model, it could not accurately predict the motions of the planets as compared to Ptolemy’s model. However, Copernicus model was more elegant in idea than the Ptolemy’s model. Placing the sun at the center of the universe produced a symmetry among the motions of the planets that was pleasing to the eye and to the intellect. All of the planets moved in the same direction at speeds that were simply related to their distance from the sun. In the Ptolemaic model, the planets were not treated equally like in Copernican model, for instance the epicycles of Venus and Mercury remained at the center on the Earth-sun line (Anon. “Copernicus vs. Ptolemy†2).
