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Ptolemy
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:''This article is about the geographer and astronomer Ptolemy. For Alexander the Great's general, later ruler of Egypt, see
Ptolemy I Soter. For others named "Ptolemy" or "Ptolemaeus", see
Ptolemy (name).''
'''Claudius Ptolemaeus''' (
Greek language Greek: {{polytonic|ΚλαÏ?διος Πτολεμαῖος}}; ca.
90 – ca.
168), known in English as '''Ptolemy''', was a
geographer,
astronomer, and
astrologer who lived in the
Hellenistic civilization Hellenistic culture of
History of Greek and Roman Egypt#Roman Egypt Roman Egypt. He may have been a
Hellenized Ancient Egypt Egyptian but no description of his family background or physical appearance exists, though it is likely he was born in Egypt.
Ptolemy was the author of several scientific treatises, three of which have been of continuing importance to later
Islamic and
European science. The first is the astronomical treatise that is now known as the '''
Almagest''' (in Greek ''Η μεγάλη ΣÏ?νταξις'', "The Great Treatise"). The second is the ''
Geographia (Ptolemy) Geography'', which is a thorough discussion of the geographic knowledge of the
Greco-Roman world. The third is the astrological treatise known as the ''Tetrabiblos'' ("Four books") in which he attempted to adapt
horoscopic astrology to the
Aristotelian natural philosophy of his day.
Astronomy
In the ''
Almagest'', one of the most influential books of
classical antiquity, Ptolemy compiled and extended the astronomical knowledge and theories of the ancient Greek and
Babylonian world; he relied mainly on the work of
Hipparchus (astronomer) Hipparchus of three centuries earlier. It was preserved, like most of Classical Greek science, in
Arabic language Arabic manuscripts (hence its familiar name) and only made available in Latin translation (by
Gerard of Cremona) in the
12th century. Ptolemy formulated a
geocentric model that was widely accepted until it was superseded by the
heliocentric solar system of
Copernicus. Likewise his computational methods (supplemented in the 12th century with the Arabic computational ''
Tables of Toledo'') were of sufficient accuracy to satisfy the needs of astronomers, astrologers and
navigators, until the time of the great explorations. They were also adopted in the Arab world and in
India. The ''Almagest'' also contains a
star catalogue, which is probably an updated 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 Ptolemy could see). The ''Almagest'' is also known as the ''Great Syntaxis of Astronomy''.
In the ''Phaseis'' (''Risings of the Fixed Stars'') Ptolemy gave a ''parapegma'', a star
calendar or
almanac based on the appearances and disappearances of stars over the course of the solar year.
Geographia
{{main|Geographia (Ptolemy)}}
Ptolemy's other main work is his ''Geographia''. This too is a compilation of what was known about the world's
geography in the
Roman Empire during his time. He relied mainly on the work of an earlier geographer,
Marinos of Tyre, and on
gazetteers of the Roman and ancient
Persian Empire Persian empire, but most of his sources beyond the perimeter of the Empire were unreliable.
The first part of the ''Geographia'' is a discussion of the data and of the methods he used. Like with the model of the solar system in the ''Almagest'', Ptolemy put all this information into a grand scheme. He assigned
coordinates to all the places and geographic features he knew, in a
grid that spanned the globe.
Latitude was measured from the
equator, as it is today, but Ptolemy preferred to express it as the length of the longest day rather than
degree (angle) degrees of arc (the length of the
midsummer day increases from 12h to 24h as you go from the equator to the
polar circle). He put the
meridian (geography) meridian of 0
longitude at the most western land he knew, the
Canary Islands.
Image:PtolemyWorldMap.jpg thumb|300px|A 15th century depiction of the [[Ptolemy world map, reconstituted from Ptolemy's ''Geographia'' (circa
150), indicating the countries of "
Seres Serica" and "Sinae" (
China) at the extreme right, beyond the island of "Taprobane" (
Sri Lanka, oversized) and the "Aurea Chersonesus" (
Malay Peninsula).]]
Ptolemy also devised and provided instructions on how to create maps both of the whole inhabited world (''oikoumenè'') and of the Roman provinces. In the second part of the ''Geographia'' he provided the necessary
topographic lists, and captions for the maps. His ''oikoumenè'' spanned 180 degrees of longitude from the Canary islands in the
Atlantic Ocean to the middle of
China, and about 80 degrees of latitude from the Arctic to the
East Indies and deep into
Africa; Ptolemy was well aware that he knew about only a quarter of the globe, and he knew that his information did not extend to the Eastern Sea.
The maps in surviving manuscripts of Ptolemy's ''Geographia'', however, date only 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 (Bagrow 1945). This means that information contained in different parts of the Geography is likely to be of different date.
Maps based on scientific principles had been made since the time of
Eratosthenes (
3rd century BC), but Ptolemy improved
map projection projections. It is known that a world map based on the ''Geographia'' was on display in
Autun,
France in late Roman times. In the
15th century Ptolemy's ''Geographia'' began to be printed with engraved maps; the earliest printed edition with engraved maps was produced in Bologna in 1477, followed quickly by a Roman edition in 1478 (Campbell, 1987). An edition printed at
Ulm in 1482, including woodcut maps, was the first one printed north of the
Alps. The maps look distorted as compared to modern maps, because Ptolemy's data were inaccurate. One reason is that Ptolemy estimated the size of the Earth as too small: while
Eratosthenes found 700 ''stadia'' for a degree on the globe, in the ''Geographia'' Ptolemy uses 500 ''stadia''. It is not certain if these geographers used the same ''stadion'', but there is no ''direct'' evidence of more than one value of the ''stadion''. If they both used the traditional Olympic ''stadion'' of about 185 meters, then the older estimate is 1/6 too large, and Ptolemy's value is 1/6 too small. Because Ptolemy derived most of his topographic coordinates by converting measured distances to angles, his maps get distorted. So his values for the latitude were in error by up to 2 degrees. For longitude this was even worse, because there was no reliable method to determine geographic longitude; Ptolemy was well aware of this. It remained a problem in geography until the invention of
chronometers at the end of the 18th century. It must be added that his original topographic list cannot be reconstructed: the long tables with numbers were transmitted to posterity through copies containing many scribal errors, and people have always been adding or improving the topographic data: this is a testimony to the persistent popularity of this influential work.
In his ''Optics'', a work which survives only in a poor Arabic translation, he writes about properties of
light, including
Reflection (physics) reflection,
refraction and
colour. His other works include ''Planetary Hypothesis'', ''Planisphaerium'' and ''Analemma''.
Astrology
Ptolemy's treatise on
astrology, the ''Tetrabiblos'', was the most popular astrological work of antiquity and also enjoyed great influence in the
Islamic world and the
medieval Latin Western world West. The ''Tetrabiblos'' is an extensive and continually reprinted treatise on the ancient principles of
Horoscopic astrology in four books (Greek ''tetra'' means "four", ''biblos'' is "book"). That it did not quite attain the unrivalled status of the ''Syntaxis'' was perhaps because it did not cover some popular areas of the subject, particularly
horary astrology (interpreting astrological charts for a particular moment to determine the outcome of a course of action to be initiated at that time),
electional astrology, and
medical astrology.
The great popularity that the ''Tetrabiblos'' did possess might be attributed to its nature as an exposition of the art of astrology and as a compendium of astrological lore, rather than as a manual. It speaks in general terms, avoiding illustrations and details of practice. Ptolemy was concerned to defend astrology by defining its limits,
Ephemeris compiling astronomical data that he believed was reliable and dismissing practices (such as considering the
Numerology numerological significance of names) that he believed to be without sound basis.
Much of the content of the ''Tetrabiblos'' may well have been collected from earlier sources; Ptolemy's achievement was to order his material in a systematic way, showing how the subject could, in his view, be rationalized. It is, indeed, presented as the second part of the study of astronomy of which the ''Syntaxis'' was the first, concerned with the influences of the celestial bodies in the
Earth sublunar sphere. Thus explanations of a sort are provided for the astrological effects of the
planets, based upon their combined effects of heating, cooling, moistening, and drying.
Ptolemy's astrological outlook was quite practical: he thought that astrology was like
medicine, that is ''conjectural'', because of the many variable factors to be taken into account: the
race,
country, and
nurture upbringing of a person affects an individual's personality as much if not more than the positions of the Sun, Moon, and planets at the precise moment of their birth, so Ptolemy saw astrology as something to be used in life but in no way relied on entirely.
Music
Ptolemy also wrote an influential work, ''Harmonics'' on
music theory. After criticizing the approaches of his predecessors, Ptolemy argued for basing musical intervals on mathematical ratios (in contrast to the followers of
Aristoxenus) backed up by empirical observation (in contrast to the overly-theoretical approach of the
Pythagoreans). He presented his own divisions of the
tetrachord and the
octave, which he derived with the help of a
monochord. Ptolemy's astronomical interests also appeared in a discussion of the
music of the spheres.
Other works
In his ''Optics'', a work which survives only in a poor Arabic translation, he writes about properties of
light, including
Reflection (physics) reflection,
refraction and
colour. His other works include ''Planetary Hypothesis'', ''Planisphaerium'' and ''Analemma''.
Named after Ptolemy
*
Ptolemaeus (lunar crater) Ptolemaeus crater on the
Moon.
*
Ptolemaeus (crater on Mars) Ptolemaeus crater [http://www.google.com/mars/#lat=-9.622414&lon=-113.203125&q=ptolemaeus] on
Mars (planet) Mars.
*The asteroid
4001 Ptolemaeus.
See also
*
Ptolemaic system - astronomical worldview as described by Claudius Ptolemaeus.
*
Ptolemy world map - map of the ancient world as described by Claudius Ptolemaeus.
*
Ptolemy's theorem - mathematical theorem described by Claudius Ptolemaeus.
*
Ptolemy Cluster - star cluster described by Claudius Ptolemaeus.
References
Texts and translations:
*Berggren, J. Lennart and Jones, Alexander. 2000. ''Ptolemy's '''Geography:''' An Annotated Translation of the Theoretical Chapters''. Princeton University Press. Princeton and Oxford. ISBN 0-691-01042-0.
*Nobbe, C. F. A., ed. 1843. Claudii Ptolemaei Geographia. 3 vols. Lipsiae (Leipzig): Carolus Tauchnitus. (The most recent edition of the complete Greek text)
*Stevenson, Edward Luther. Trans. and ed. 1932. ''Claudius Ptolemy: The Geography''. New York Public Library. Reprint: Dover, 1991. (This is the only complete English translation of Ptolemy's most famous work. Unfortunately, it is marred by numerous mistakes and the placenames are given in Latinised forms, rather than in the original Greek).
Other references:
*Bagrow, L. 1945. The Origin of Ptolemy's Geographia. Geografiska Annaler 27:318-387.
*Campbell, T. 1987. The Earliest Printed Maps, British Museum Press.
External links
{{wikiquote}}
{{commons|ΚλαÏ?διος Πτολεμαῖος|Ptolemy}}
Primary sources
-
Ptolemy's Tetrabiblos at LacusCurtius (English translation, with introductory material)
-
Ptolemy's Geography at LacusCurtius (English translation, incomplete)
-
Extracts of Ptolemy on the country of the Seres (China) (English translation)
Secondary material
-
Ptolemy at SkyScript - ''The Life and Work of Ptolemy''
-
Alexander Jones, "Ptolemy and his ''Geography''"
-
Ptolemy biography (Bill Arnett's site)
-
Ptolemy's Geography of Asia - Selected problems of Ptolemy's Geography of Asia (currently in German)
-
Ptolemy's Geography of Northwestern Europe
-
History of Cartography including a discussion of the Geographica
-
Claudius Ptolemaeus (Ptolemy): Representation, Understanding, and Mathematical Labeling of the Spherical Earth
Category:Polymaths Ptolemy
Category:Greek and Roman astronomers Ptolemy
Category:Greek and Roman astrologers Ptolemy
Category:Greek cartographers Ptolemy
Category:Roman era geographers Ptolemy
Category:Geodesists Ptolemy
Category:85 births Ptolemy
Category:165 deaths Ptolemy
Category:Music theorists
Category:History of astronomy
br:Ptolemaios
ca:Claudi Ptolemeu
cs:Klaudios Ptolemaios
da:Ptolemæus
de:Ptolemäus
es:Claudio Ptolomeo
eo:Ptolemeo
eu:Klaudios Ptolemaios
fa:بطلمیوس (ابهام‌زدایی)
fr:Ptolémée
gl:Ptolomeo
ko:í?´ë?¼ìš°ë””오스 í”„í†¨ë ˆë§ˆì?´ì˜¤ìŠ¤
ia:Ptolemeo
it:Claudio Tolomeo
he:תלמי (×?×¡×˜×¨×•× ×•×?)
lt:Klaudijus PtolemÄ—jus
hu:Ptolemaiosz Klaudiosz
nl:Claudius Ptolemaeus
ja:クラウディオス・プトレマイオス
no:Klaudios Ptolemaios
pl:Klaudiusz Ptolemeusz
pt:Ptolemeu
ro:Ptolemeu
ru:Клавдий Птолемей
scn:Tulumeu
simple:Ptolemy
sk:Ptolemaios
sl:Ptolemej
fi:Klaudios Ptolemaios
sv:Klaudios Ptolemaios
th:ทà¸à¹€à¸¥à¸¡à¸µ
vi:Claudius Ptolemaeus
tr:Batlamyus
uk:Птолемей Клавдій
zh:托勒密
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