# Ptolemy

## 2nd-century Roman mathematician, astronomer, geographer / From Wikipedia, the free encyclopedia

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**Claudius Ptolemy** (/ˈtɒləmi/; Greek: Πτολεμαῖος, *Ptolemaios*; Latin: *Claudius Ptolemaeus*; c. 100 – c. 170 AD)[2] was a Roman mathematician, astronomer, astrologer, geographer, and music theorist,[3] 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*.

**Quick facts: Ptolemy, Born, Died, Citizenship, Known ...**▼

Ptolemy | |
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Κλαύδιος Πτολεμαῖος | |

Born | c. 100 AD[2] Egypt, Roman Empire |

Died | c. 170 (aged 69–70) AD[2] Alexandria, Egypt, Roman Empire |

Citizenship | Roman; ethnicity: Greco-Egyptian |

Known for | Ptolemaic 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 | |

Fields | Astronomy, Geography, Astrology, Optics |

Influences | Aristotle Hipparchus |

Influenced | Theon of Alexandria Abu Ma'shar Nicolaus Copernicus |

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.[4] 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.[5][6]