The Ptolemaic Model

The Ptolemaic model was an ancient way of explaining how the planets and stars move in the sky. It proposed that Earth was stationary at the center of the universe, and planets, including the Sun, moved around it in complex paths. To account for complicated observations, it used ideas like planets moving in small circles called epicycles, which themselves moved along larger circles called deferents. While this model accurately predicted planetary motions for centuries, it was eventually replaced by the heliocentric model, which places the Sun at the center.