Teach Astronomy - Problems With Greek Cosmology

http://www.teachastronomy.com/ The Greek geocentric cosmology of Aristotle, as propagated by Ptolemy, was highly complex in trying to explain the motions within the solar system. Because the planets do not have uniform motion, the model needed the centers of their motion to be displaced from the Earth. Because Mars, Jupiter, and Saturn display retrograde motion, or occasional backward motion on the sky, they had to have epicycles inserted on their orbits. All in all, the Ptolemaic model was extremely complex and not very efficient. In the thirteenth century King Alfonso of Spain said he would have consulted the creator to come up with a better arrangement. One of the fundamental principles of science called Ockham's razor after William of Ockham in the fourteenth century is the idea that the best explanation for a natural phenomenon is the simplest explanation. By the thirteenth century it was clear that the Ptolemaic model was not very simple and not very elegant, so people were seeking new solutions.