epicycles

(noun)

The geometric model used to explain the variations in speed and direction of the apparent motion of the Moon, Sun, and planets in the Ptolemaic system of astronomy.

Related Terms

Examples of epicycles in the following topics:

  • Astronomy

    • It positioned the Sun near the center of the Universe, motionless, with Earth and the other planets rotating around it in circular paths modified by epicycles and at uniform speeds.
    • The book argued heliocentrism and ellipses for planetary orbits instead of circles modified by epicycles.