100 - 170

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Claudius Ptolemy (; Greek: Πτολεμαῖος, Ptolemaios; Latin: Claudius Ptolemaeus; c. 100 – c. 170 AD) was an Alexandrian mathematician, astronomer, astrologer, geographer, and music theorist 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. Read more on Wikipedia

Since 2007, the English Wikipedia page of Ptolemy has received more than 5,782,815 page views. His biography is available in 117 different languages on Wikipedia (up from 115 in 2019). Ptolemy is the 5th most popular astronomer (down from 4th in 2019), the 6th most popular biography from Egypt (down from 4th in 2019) and the most popular Egyptian Astronomer.

Ptolemy is most famous for his geocentric model of the universe, which he proposed in his book, "Almagest." In this model, the earth is at the center of the universe and all other celestial bodies orbit around it.

Memorability Metrics

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  • 84.92

    Historical Popularity Index (HPI)

  • 117

    Languages Editions (L)

  • 15.35

    Effective Languages (L*)

  • 3.99

    Coefficient of Variation (CV)


Among astronomers, Ptolemy ranks 5 out of 644Before him are Galileo Galilei, Nicolaus Copernicus, Johannes Kepler, and Giordano Bruno. After him are Anders Celsius, Tycho Brahe, William Herschel, Ulugh Beg, Ja'far al-Sadiq, Aristarchus of Samos, and Edwin Hubble.

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Among people born in 100, Ptolemy ranks 1After him are Pope Alexander I, Joseph of Arimathea, Decebalus, Dionysius the Areopagite, Thecla, James the Less, Longinus, Saint Sarah, Pope Victor I, Pope Telesphorus, and Pope Hyginus. Among people deceased in 170, Ptolemy ranks 1After him are Apuleius, Salvius Julianus, Junius Rusticus, and Alexander of Abonoteichus.

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In Egypt

Among people born in Egypt, Ptolemy ranks 6 out of 642Before him are Moses (-1393), Cleopatra (-69), Tutankhamun (-1341), Euclid (-350), and Nefertiti (-1400). After him are Yasser Arafat (1929), Akhenaten (-1400), Hypatia (350), Anthony the Great (251), Origen (185), and Joshua (-1355).


Among astronomers born in Egypt, Ptolemy ranks 1After him are Sosigenes of Alexandria (-80), and Timocharis (-320).