Ptolemy's Almagest

Ptolemy's *Almagest* is a key astronomical treatise written in the 2nd century. It systematically presents the geocentric model of the universe, where Earth is at the center, and planets, the Sun, and stars revolve around it. Ptolemy introduced mathematical techniques to predict planetary movements and explained retrograde motion. His work combined observational data with geometry and remained the authoritative astronomical text for over a thousand years, heavily influencing both Islamic and Western science. The *Almagest* showcases the blend of empirical observation and theoretical modeling, pivotal in the history of astronomy.