Ptolomeo

Ptolemy, also known as Claudius Ptolemaeus in Greek and Tolomeo in Italian, was a Greco-Egyptian scholar active in Alexandria during the 2nd century CE. A mathematician, astronomer, geographer, and optician, he produced influential works that synthesized earlier Greek knowledge and shaped later scientific thought. His writings were foundational for both the Islamic and European scientific traditions for many centuries.

In astronomy, his most celebrated work is the Almagest, a comprehensive treatise that presents a geocentric model of the cosmos with the Earth at the center. It explains celestial motions using deferents and epicycles to account for planetary retrograde motion, and it includes a detailed star catalog and procedures for predicting positions. The Almagest remained the standard astronomical reference in the medieval world until the Copernican revolution.

Geography is another central work, the Geographia, which compiles coordinates and descriptions for a vast array of places and introduces a system of latitude and longitude, along with methods for constructing maps. Its cartographic approach influenced mapmaking in the late antique, medieval, and early modern periods.

Ptolemy also wrote on optics and astrology, with the Optics addressing vision and the Tetrabiblos outlining astrological theory. His Handy Tables provided practical astronomical calculations. Collectively, Ptolemy’s works organized and extended classical knowledge, cementing a lasting legacy in the history of astronomy and geography.