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For other uses, see Ptolemy (name).
PSM V78 D326 Ptolemy.png
Early Baroque artist's rendition
Born c. AD 100[1]
Egypt, Roman Empire
Died c. AD 170 (aged 69–70)[1]
Alexandria, Egypt, Roman Empire

Claudius Ptolemy (/ˈtɒləmi/; Greek: Κλαύδιος Πτολεμαῖος, Klaúdios Ptolemaîos, [kláwdios ptolɛmɛ́ːos]; Latin: Claudius Ptolemaeus; c. AD 100 – c. 170)[2] was a Greco-Egyptian writer, known as a mathematician, astronomer, geographer, astrologer, and poet of a single epigram in the Greek Anthology.[3][4] He lived in the city of Alexandria in the Roman province of Egypt, wrote in Koine Greek, and held Roman citizenship.[5] Beyond that, few reliable details of his life are known. His birthplace has been given as Ptolemais Hermiou in the Thebaid in an uncorroborated statement by the 14th-century astronomer Theodore Meliteniotes.[6] This is a very late attestation, however, and there is no other reason to suppose that he ever lived anywhere else than Alexandria,[6] where he died around AD 168.[7]

Ptolemy wrote several scientific treatises, three of which were of importance to later Byzantine, Islamic and European science. The first is the astronomical treatise now known as the Almagest, although it was originally entitled the "Mathematical Treatise" (Μαθηματικὴ Σύνταξις, Mathēmatikē Syntaxis) and then known as the "Great Treatise" (Ἡ Μεγάλη Σύνταξις, Ē Megálē Syntaxis). The second is the Geography, which is a thorough discussion of the geographic knowledge of the Greco-Roman world. This manuscript was used by Christopher Columbus as the map for his westward-bound path to Asia, in which he discovered the hitherto unknown lands of the Americas. 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 (Ἀποτελεσματικά) but more commonly known as the Tetrabiblos from the Greek (Τετράβιβλος) meaning "Four Books" or by the Latin Quadripartitum.






Ptolemy wrote in Greek and can be shown to have utilized Babylonian astronomical data.[12][13] He was a Roman citizen, but most scholars conclude that Ptolemy was ethnically Greek,[14][15][16] although some suggest he was a Hellenized Egyptian.[15][17][18] He was often known in later Arabic sources as "the Upper Egyptian",[19] suggesting he may have had origins in southern Egypt.[20] Later Arabic astronomers, geographers and physicists referred to him by his name in Arabic: بَطْلُمْيوس‎‎ Batlamyus.[21]


Further information: Almagest
Ptolemy with an armillary sphere model, by Joos van Ghent and Pedro Berruguete, 1476, Louvre, Paris

The Almagest is the only surviving comprehensive ancient treatise on astronomy. Babylonian astronomers had developed arithmetical techniques for calculating astronomical phenomena; Greek astronomers such as Hipparchus had produced geometric models for calculating celestial motions. Ptolemy, however, claimed to have derived his geometrical models from selected astronomical observations by his predecessors spanning more than 800 years, though astronomers have for centuries suspected that his models' parameters were adopted independently of observations.[22] Ptolemy presented his astronomical models in convenient tables, which could be used to compute the future or past position of the planets.[23] The Almagest also contains a star catalogue, which is a version of a catalogue created by Hipparchus. Its list of forty-eight constellations is ancestral to the modern system of constellations, but unlike the modern system they did not cover the whole sky (only the sky Hipparchus could see). Across Europe, the Middle East and North Africa in the Medieval period, it was the authoritative text on astronomy, with its author becoming an almost mythical figure, called Ptolemy, King of Alexandria.[24] The Almagest was preserved, like most of Classical Greek science, in Arabic manuscripts (hence its familiar name). Because of its reputation, it was widely sought and was translated twice into Latin in the 12th century, once in Sicily and again in Spain.[25] Ptolemy's model, like those of his predecessors, was geocentric and was almost universally accepted until the appearance of simpler heliocentric models during the scientific revolution.

His Planetary Hypotheses went beyond the mathematical model of the Almagest to present a physical realization of the universe as a set of nested spheres,[26] in which he used the epicycles of his planetary model to compute the dimensions of the universe. He estimated the Sun was at an average distance of 1,210 Earth radii, while the radius of the sphere of the fixed stars was 20,000 times the radius of the Earth.[27]


The Geography[edit]

Main article: Geography (Ptolemy)
Geography by Ptolemy, Latin manuscript of the early 15th century

Ptolemy's other main work is his Geography (also called the Geographia), a compilation of geographical coordinates of the part of the world known to the Roman Empire during his time. He relied somewhat on the work of an earlier geographer, Marinos of Tyre, and on gazetteers of the Roman and ancient Persian Empire.[citation needed] He also acknowledged ancient astronomer Hipparchus for having provided the elevation of the north pole for a few cities.[28]


A 15th-century manuscript copy of the Ptolemy world map, reconstituted from Ptolemy's Geography (circa 150), indicating the countries of "Serica" and "Sinae" (China) at the extreme east, beyond the island of "Taprobane" (Sri Lanka, oversized) and the "Aurea Chersonesus" (Malay Peninsula).
Prima Europe tabula. A C15th copy of Ptolemy's map of Britain


The maps in surviving manuscripts of Ptolemy's Geography, however, only date from about 1300, after the text was rediscovered by Maximus Planudes. It seems likely that the topographical tables in books 2–7 are cumulative texts – texts which were altered and added to as new knowledge became available in the centuries after Ptolemy.[30] This means that information contained in different parts of the Geography is likely to be of different dates.





Main article: Tetrabiblos

Ptolemy has been referred to as “a pro-astrological authority of the highest magnitude”.[32] His astrological treatise, a work in four parts, is known by the Greek term Tetrabiblos, or the Latin equivalent Quadripartitum: ‘Four Books’. Ptolemy's own title is unknown, but may have been the term found in some Greek manuscripts: Apotelesmatika, roughly meaning 'Astrological Outcomes,' 'Effects' or ‘Prognostics’.[33][34]







Ptolemy also wrote an influential work, Harmonics, on music theory and the mathematics of music. After criticizing the approaches of his predecessors, Ptolemy argued for basing musical intervals on mathematical ratios (in contrast to the followers of Aristoxenus and in agreement with the followers of Pythagoras), backed up by empirical observation (in contrast to the overly theoretical approach of the Pythagoreans). Ptolemy wrote about how musical notes could be translated into mathematical equations and vice versa in Harmonics. This is called Pythagorean tuning because it was first discovered by Pythagoras. However, Pythagoras believed that the mathematics of music should be based on the specific ratio of 3:2, whereas Ptolemy merely believed that it should just generally involve tetrachords and octaves. He presented his own divisions of the tetrachord and the octave, which he derived with the help of a monochord. His Harmonics never had the influence of his Almagest or Planetary Hypotheses, but a part of it (Book III) did encourage Kepler in his own musings on the harmony of the world (Kepler, Harmonice Mundi, Appendix to Book V).[37] Ptolemy's astronomical interests also appeared in a discussion of the "music of the spheres". See: Ptolemy's intense diatonic scale.


His Optics is a work that survives only in a poor Arabic translation and in about twenty manuscripts of a Latin version of the Arabic, which was translated by Eugene of Palermo (c. 1154). In it Ptolemy writes about properties of light, including reflection, refraction, and colour. The work is a significant part of the early history of optics[38] and influenced the more famous 11th-century Book of Optics by Alhazen (Ibn al-Haytham). It contains the earliest surviving table of refraction from air to water, for which the values (with the exception of the 60° angle of incidence), although historically praised as experimentally derived, appear to have been obtained from an arithmetic progression.[39]


Named after Ptolemy[edit]

There are several characters or items named after Ptolemy, including:

See also[edit]


  1. ^ a b
  4. ^ Mortal am I, the creature of a day..
  5. ^ See 'Background' section on his status as a Roman citizen
  8. ^ Πτολεμαῖος, Georg Autenrieth, A Homeric Dictionary, on Perseus
  11. ^ Robbins, Ptolemy Tetrabiblos ‘Introduction’; p. x.
  14. ^ Encyclopaedia Britannica 2007, "Claudius Ptolemaeus"
  21. ^ Shahid Rahman; Tony Street; Hassan Tahiri, eds. (2008). "The Birth of Scientific Controversies, The Dynamics of the Arabic Tradition and Its Impact on the Development of Science: Ibn al-Haytham's Challenge of Ptolemy's Almagest". The Unity of Science in the Arabic Tradition. 11. Springer Netherlandsdoi=10.1007/978-1-4020-8405-8. pp. 183–225 [183]. doi:10.1007/978-1-4020-8405-8. ISBN 978-1-4020-8404-1. 
  26. ^ Dennis Duke, Ptolemy's Cosmology
  28. ^ Shcheglov D.A. (2002–2007): "Hipparchus’ Table of Climata and Ptolemy’s Geography", Orbis Terrarum 9 (2003–2007), 177–180.
  29. ^ Book 8
  30. ^ Bagrow 1945.
  31. ^ Richard J.A. Talbert, "Urbs Roma to Orbis Romanus", in Talbert, Ancient Perspectives: Maps and Their Places in Mesopotamia, Egypt, Greece and Rome (Chicago) 2012, pp 170–72.
  33. ^ Robbins, Ptolemy Tetrabiblos, 'Introduction' p. x.
  34. ^ Jones (2010) p. xii.
  35. ^ Robbins, Ptolemy Tetrabiblos, 'Introduction' p. xii.
  36. ^ FA Robbins, 1940; Thorndike 1923
  37. ^ Hetherington, Norriss S. Encyclopedia of Cosmology (Routledge Revivals): Historical, Philosophical, and Scientific Foundations of Modern Cosmology Routledge, 8 apr. 2014 ISBN 978-1317677666 p 527
  39. ^ Carl Benjamin Boyer, The Rainbow: From Myth to Mathematics (1959)
  43. ^ Mars Labs. Google Maps.


Texts and translations[edit]

  • Bagrow, L. (January 1, 1945). "The Origin of Ptolemy's Geographia". Geografiska Annaler. Geografiska Annaler, Vol. 27. 27: 318–387. doi:10.2307/520071. ISSN 1651-3215. JSTOR 520071. 

External links[edit]

Primary sources[edit]

Secondary material[edit]

Animated illustrations[edit]