Geocentric Model

The geocentric model is the ancient and medieval astronomical framework holding that Earth sits stationary at the center of the universe, with the Sun, Moon, planets and stars orbiting around it, most fully developed in the second century by the Alexandrian astronomer Ptolemy in his work the Almagest. To account for the observed irregular motion of the planets, the model relied on an elaborate system of epicycles, circles riding on circles, that could reproduce planetary positions with reasonable accuracy despite the underlying premise being incorrect. It remained the dominant cosmological framework in Europe and the Islamic world for roughly fourteen centuries until it was gradually displaced by the heliocentric model advanced by Nicolaus Copernicus and later confirmed by Galileo Galilei's telescopic observations and Johannes Kepler's laws of planetary motion.