In astronomy, the geocentric model (also known as geocentrism, or the Ptolemaic system) is a superseded description of the universe, where the Earth is at the center of all the celestial bodies. This model served as the predominant cosmological system in many ancient civilizations such as ancient Greece including the noteworthy systems of Aristotle (see Aristotelian physics) and Ptolemy. As such, they believed that the Sun, Moon, stars, and naked eye planets circled Earth.[1]

Two commonly made observations supported the idea that Earth was the center of the Universe. The stars, the sun, and planets appear to revolve around Earth each day, making Earth the center of that system. The stars were thought to be on a celestial sphere, with the earth at its center, that rotated each day, using a line through the north and south pole as an axis. The stars closest to the equator appeared to rise and fall the greatest distance, but each star circled back to its rising point each day.[2] The second observation supporting the geocentric model was that the Earth does not seem to move from the perspective of an Earth-bound observer, and that it is solid, stable, and unmoving.

Ancient Greek, ancient Roman and medieval philosophers usually combined the geocentric model with a spherical Earth. It is not the same as the older flat Earth model implied in some mythology.[n 1][n 2][5] The ancient Jewish Babylonian uranography pictured a flat Earth with a dome-shaped rigid canopy named firmament placed over it. (רקיע- rāqîa').[n 3][n 4][n 5][n 6][n 7][n 8]

However, the ancient Greeks believed that the motions of the planets were circular and not elliptical, a view that was not challenged in Western culture until the 17th century through the synthesis of theories by Copernicus and