Geostatic and geocentric cosmos.
Celestial bodies possess uniform, circular motion around a central point.
Celestial bodies are composed of a fifth element, the quintessence. The cosmos is finite. Difficulty developed concerning the Ptolemaic use of the equant, which violated the aesthetic concept of uniform motion, and the use of epicycles, which put the center of motion on a geometric point other than a center of a deferent. B. The Copernican System. Introduced three celestial motions.