100?-170?

Greek mathematician, astronomer, and geographer whose major work, the Almagest, is a large mathematical text that describes the movement of the heavens. A Roman citizen of Greek descent living in Alexandria, Egypt, he was the most influential ancient astronomer. The mathematics used in the Algamest is the geometry of Euclid, applied to explain astronomical observations. Ptolemy's ideas dominated astronomy for 14 centuries. He also wrote on other mathematical topics, astrology, and geography.