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Ptolemy
Κλαύδιος Πτολεμαῖος
Ptolemy 16century.jpg
Ptolemy "the Alexandrian", as depicted in a 16th-century engraving.
Bornc. 100 AD
Egypt, Roman Empire
Diedc. 170 (aged 69–70) AD
Alexandria, Egypt, Roman Empire
CitizenshipRoman; ethnicity: Greco-Egyptian
Known forPtolemaic universe
Ptolemy's world map
Ptolemy's intense diatonic scale
Ptolemy's table of chords
Ptolemy's inequality
Ptolemy's theorem
Equant
Evection
Quadrant
Scientific career
FieldsAstronomy, Geography, Astrology, Optics
InfluencesAristotle
Hipparchus
InfluencedTheon of Alexandria
Abu Ma'shar
Nicolaus Copernicus

Claudius Ptolemy (/ˈtɒləmi/; Greek: Πτολεμαῖος, Ptolemaios; Latin: Claudius Ptolemaeus; c. 100 – c. 170 AD) was a mathematician, astronomer, astrologer, geographer, and music theorist, who wrote about a dozen scientific treatises, three of which were of importance to later Byzantine, Islamic, and Western European science. The first is the astronomical treatise now known as the Almagest, although it was originally entitled the Mathēmatikē Syntaxis or Mathematical Treatise, and later known as The Greatest Treatise. The second is the Geography, which is a thorough discussion on maps and the geographic knowledge of the Greco-Roman world. The third is the astrological treatise in which he attempted to adapt horoscopic astrology to the Aristotelian natural philosophy of his day. This is sometimes known as the Apotelesmatika (lit. "On the Effects") but more commonly known as the Tetrábiblos, from the Koine Greek meaning "Four Books", or by its Latin equivalent Quadripartite.

Unlike most ancient Greek mathematicians, Ptolemy's writings (foremost the Almagest) never ceased to be copied or commented upon, both in Late Antiquity and in the Middle Ages. However, it is likely that only a few truly mastered the mathematics necessary to understand his works, as evidenced particularly by the many abridged and watered-down introductions to Ptolemy's astronomy that were popular among the Arabs and Byzantines alike.

Biography