Ancient History, Greek and Roman through Late Antiquity Commons^™

The Cosmos According To Ptolemy, Benjamin Smith

Classics Ancient Science Fair

In the second century AD, Claudius Ptolemaeus, the astronomer from Alexandria, would provide a geometric conception of the cosmos with the ability to predict planetary motion, in what would be known as the Ptolemaic, or Geocentric, Model of the Universe. Prior to Ptolemy, the notion in ancient astronomy was that the cosmos was ”perfect”; the heavenly bodies must move along the perfect curve (a circle) as the perfect shape (a sphere). Yet, irregularities occur in observing the planets in concentric circles alone. Ptolemy’s answer, building upon Hipparchus and Aristotle, would present an eccentric system in which the heavenly bodies move …