Although heliocentric models of planetary motion had been proposed before Ptolemy, his geocentric model was so accurate in predicting the positions of the planets that it became the standard model until challenged by Copernicus. A heliocentric system was not generally accepted until the German astronomer Johannes Kepler (1571–1630) developed his laws of planetary motion, and the Ptolemaic system was only finally disproved following Galileo's observations of the phases of the planet Venus.
Ptol·e·ma·ic sys·tem (also Ptolemaic theory) • n. hist. Astron. the theory that the earth is the stationary center of the universe, with the planets moving in epicyclic orbits within surrounding concentric spheres. Compare with Copernican system.