Ptolemy

Ptolemy, usually known as Claudius Ptolemy, was a Greco-Roman scholar who lived and worked in Alexandria in the 2nd century CE. Details of his life are uncertain, but reliable reference works agree that he was active in astronomy, mathematics, and geography, and that his writing became some of the most important scientific work of the ancient world.

He is especially famous for the Almagest, a major treatise that organized earlier Greek astronomy into a powerful Earth-centered model of the cosmos. He also wrote the Geography, which gathered place names and mapmaking methods, along with influential works on astrology and optics. Even when later science moved beyond some of his conclusions, his books remained central to learning in the Byzantine, Islamic, and Latin European worlds for centuries.

Because so little is known about him as a person, Ptolemy is remembered mainly through his ideas: careful calculation, wide-ranging curiosity, and an effort to explain the universe in a systematic way. For readers interested in the history of science, he stands as one of antiquity's most enduring and influential authors.