# 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)^{[1]} was an Alexandrian mathematician, astronomer, astrologer, geographer, and music theorist^{[2]} who wrote about a dozen scientific treatises, three of which were important to later Byzantine, Islamic, and Western European science. The first was his astronomical treatise now known as the *Almagest*, originally entitled *Mathematical Treatise* (Greek: Μαθηματικὴ Σύνταξις, * Mathēmatikḗ Syntaxis*). 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*(Greek: Αποτελεσματικά, 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**Born, Died ...

Ptolemy | |
---|---|

Κλαύδιος Πτολεμαῖος | |

Born | c. 100 AD^{[1]}Unknown |

Died | c. 170 (aged 69–70) AD^{[1]}Alexandria, Egypt, Roman Empire |

Citizenship | possibly Roman; ethnicity:Greco-Egyptian or Hellenized 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 |

Because the Catholic Church promoted his work, which included the only mathematically sound geocentric model of the Solar System, and unlike most 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.^{[3]}
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.^{[4]}^{[5]}
His work on epicycles has come to symbolize a very complex theoretical model built in order to explain a false assumption.