Ptolemy (Claudius Ptolemy)

Claudius Ptolemy was an ancient Greek astronomer and mathematician living around 150 AD. He developed a model of the cosmos called the Ptolemaic system, which placed Earth at the center of the universe. In this model, planets and stars moved in complex paths involving circles called epicycles to explain their observed motions. His work, especially the "Almagest," was the dominant astronomical authority for over a thousand years, guiding navigation and understanding of the heavens until the heliocentric model proposed later by Copernicus. Ptolemy's system reflects the scientific understanding of his time and remains important historically.