Epicycle

Epicycle is an expression used in the Ptolemaic system of astronomy. The old belief that the celestial bodies moved in perfect circles round the earth was found to be inadequate to explain the varying position of the planets, a difficulty which led Ptolemy to invent his theory of epicycles, which was to the effect that each planet revolved round a centre of its own, greater or less, but that all these centres themselves moved in procession round the earth, a theory which fell to pieces before the investigations of Kepler and Newton.

Nearby pages
Epidaurus, Epidemic, Epidemiology, Epigoni, Epigram