Ptolemaic Astronomy is an ancient astronomical system developed by the Greek astronomer Claudius Ptolemy in the 2nd century AD. It is based on the geocentric model, which posits that the Earth is at the center of the universe, and all celestial bodies, including the Sun, Moon, and planets, revolve around it in circular orbits. Ptolemy's work, particularly in his book Almagest, introduced complex mechanisms like epicycles to explain the observed movements of planets. This model dominated Western and Islamic astronomy for over a thousand years until the Copernican Revolution introduced the heliocentric model, placing the Sun at the center of the solar system.