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mathematician, geographer, astronomer, astrologer


Ptolemy (Claudius Ptolemaeus), fl. 2d cent. A.D., celebrated Greco-Egyptian mathematician, astronomer, and geographer. He made his observations in Alexandria and was the last great astronomer of ancient times. Although he discovered the irregularity in the moon's motion, known as evection, and made original observations regarding the motions of the planets, his place in the history of science is that of collator and expounder. He systematized and recorded the data and doctrines that were known to Alexandrian men of science. His works on astronomy and geography were the standard textbooks until the teachings of Copernicus came to be accepted. The mathematical and astronomical systems developed by the Greeks are contained in his 13-volume work, Almagest. With credit to Hipparchus as his chief authority, he presented in his famous book problems and explanations dealing with the known heavenly bodies and their relations to the earth. The Ptolemaic system thus evolved represented the earth (a globe in form) as stationary in the center of the universe, with sun, moon, and stars revolving about it in circular orbits and at a uniform rate. From the center outward the elements were earth, water, air, fire, and ether. Beyond lay zones, or heavens, each an immense sphere. The planets were assumed to revolve in small circles, called epicycles, whose centers revolved around the earth in the vast circles, or deferents, of the spheres. (To account for the precession of the equinoxes and other phenomena, later astronomers found it necessary to add more epicycles and to make both epicycles and deferents eccentric.) The Almagest also contains other astronomical information, including a catalog of more than 1020 stars (giving their latitudes, longitudes, and magnitudes), as well as mathematical information, including a table of chords. Ptolemy's system of geography is founded upon the works of Marinus of Tyre; many errors stem from his underestimation of the earth's circumference. However, his system was in use until the 16th cent. His mathematical theories, most valuable in the field of trigonometry, are preserved in his Analemma and Planisphaerium. His writings, circulated in the original Greek and in Arabic and Latin translations, include also the Tetrabiblos, a study of astrology.


See tr. of his Geography by E. L. Stevenson (1932) and of his Almagest by R. C. Taliaferro (1952).

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The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.



(also Lagid), a royal dynasty that reigned in Hellenistic Egypt from 305 B.C. to 30 B.C.

Ptolemy I Soter (”Savior”), founder of the dynasty, was one of Alexander the Great’s military commanders. In 323 B.C, he was given Egypt to govern when Alexander’s empire was divided among the Diadochoi. In 305 he proclaimed himself king and ruled until 283 B.C. In the course of the fierce wars among the Diadochoi, he expanded the boundaries of his kingdom by annexing Cyrenaica, southern Syria, and Cyprus. Under his reign, the reconstruction of the irrigation network was begun and the practice of apportioning land plots (kleroi) to mercenaries (Macedonians, Greeks, Thracians) was introduced. There was extensive construction in Alexandria and the new polis of Ptolemais was founded near Thebes. A cult of the god Serapis, uniting local and Greek beliefs, was instituted, and a cult of the king emerged.

Ptolemy II Philadelphus (”Brother-loving”) ruled from 285 to 246 B.C. (from 285 to 283 as co-ruler). Under his rule, Egypt’s influence in the eastern Mediterranean region grew. A powerful navy was built and a number of regions in Asia Minor and the Aegean basin were annexed. The tax codes and other legislative documents of this period indicate that a system of socioeconomic relations developed that was characterized by the dominance of a state economy based on the exploitation of two groups: the “royal farmers,” who worked the royal lands as tenant farmers, and the hypoteleis, artisans of the workshops for state-monopolized crafts. Although slave labor did not play a significant role in production, slaveholding relations and various forms of noneconomic coercion permeated the entire social life of the Ptolemaic state as well. The royal lands and workshops, the extensive system of taxes and liturgies, the sale of concessions in various trades, and the commercial monopolies brought the royal treasury large revenues in kind and in money, which were used to maintain the sumptuous royal court, the army and navy, and the huge apparatus of government officials, as well as to subsidize the priesthood and temples. Alexandria, the Ptolemaic capital, became a major trade, artisan, and cultural center for the Mediterranean region. Trade routes linked the Ptolemaic state to central Africa, Arabia, India, the Black Sea coastal region, and the eastern and western Mediterranean states.

Ptolemy III Euergetes (”Benefactor”) ruled from 246 to 221 B.C. The Ptolemaic state reached its greatest political power during his reign. Cyrenaica, which had broken away in 282, was re-annexed, part of northern Syria was conquered during a war with the Seleucids, and new territorial possessions in Asia Minor were acquired.

Ptolemy IV Philopator (”Father-loving”) ruled from 221 to 204 B.C. In a war with the Seleucid king Antiochus III in 219, Ptolemy IV lost almost all the Syrian territories. Soon after, disturbances broke out among the machimoi (Egyptian soldiers, who received the smallest kleroi). These disturbances grew into mass uprisings throughout the country, with local dynasts appearing in Thebes and its surrounding region. The struggle among the elite intensified. Ptolemy IV was killed and Ptolemy V, a young boy, was elevated to the throne.

Ptolemy V Epiphanes (”Manifest God”) ruled from 204 to 180 B.C. The political importance of the Egyptian priesthood increased under his reign. Exploiting the internal disturbances in Egypt, Macedonia and the Seleucids seized between 202 and 198 B.C. the Ptolemaic lands in Asia Minor and the Aegean basin. The loss of revenues from outside possessions led to an increase in the tax burden. The incursion of the Seleucid king Antiochus IV into Egypt in 170–168 B.C further aggravated the country’s economic situation, leading to the mass flight (anachoresis) of farmers from the villages.

Ptolemy VI Philometor (”Mother-loving”) ruled from 180 to 145 B.C. His attempt to introduce compulsory farm rents provoked a new wave of popular uprisings. Protracted dynastic wars ensued between Ptolemy VI and his brother and co-ruler Ptolemy VIII Euergetes, nicknamed Physcon (”Potbellied”; ruled 170–116 B.C), between Ptolemy VIII and his sister and wife Cleopatra II, and between Cleopatra III, Physcon’s widow, and her sons Ptolemy IX Soter (ruled 116 B.C–80 B.C.) and his co-ruler Ptolemy X Alexander I (ruled 101–88 B.C). Underlying these wars was a political struggle between two groupings within the ruling class: the traders’ and artisans’ circles of Alexandria and the landowning elite of soldiers, government officials, and priests in the country’s interior. The issue of relations with Rome, which from the first century B.C. had been continuously interfering in Egypt’s internal affairs, played an important role in this struggle.

Ptolemy XI Alexander II was placed on the throne by Rome in 80 B.C. but was killed by insurgent Alexandrians.

Ptolemy XII Philopator Neos Dionysus ruled from 80 to 51 B.C. He was driven out by the Alexandrians in 58 B.C. but returned to the throne with the aid of Roman legions.

As a result of the Alexandrine War of 48–47 B.C., Cleopatra VII was placed on the throne. In 30 B.C., Octavian (Augustus) annexed the Ptolemaic state to the Roman Empire as the imperial province of Egypt.


Ranovich, A. B. Ellinizm i ego istoricheskaia rol’. Moscow-Leningrad, 1950. Chapter 5.
Zel’in, K. K. lssledovaniia po istorii zemel’nykh otnoshenii v ellinisticheskom Egipte II-I vv. do n. e. Moscow, 1960.
Pavlovskaia, A. I. “Rabstvo v ellinisticheskom Egipte.” In T. V. Blavatskaia, E. S. Golubtsova, and A. I. Pavlovskaia, Rabstvo v ellinisticheskikh gosudarstvakh v III-I vv. do n. e. Moscow, 1969. Pages 200–309.
Pikus, N. N. Tsarskie zemledel’tsy (neposredstvennye proizvoditeli) i remeslenniki v Egipte III v. do n. e. Moscow, 1972.
Bevan, E. A History of Egypt Under the Ptolemaic Dynasty. London, 1927.
Préaux, C. L’Economie royale des Lagides. Brussels, 1939.
Otto, W., and H. Bengtson. Zur Geschichte des Niederganges des Plolemäerreiches. Munich, 1938.
Volkmann, H. “Ptolemaios.” In Paulys Realencyclopädie der classischen Alterlumswissenschaft, 1959, vol. 23, part 2. Stuttgart, 1959.




(Claudius Ptolemaeus). Lived in the second century. Ancient Greek scientist.

Ptolemy elaborated the geocentric system of the universe, according to which the apparent motions of the heavenly bodies can be explained in terms of the bodies’ often very complex motion about a stationary earth. Biographical information on Ptolemy is scanty. It is known that he spent a large part of his life in Alexandria, where he conducted astronomical observations from 127 to 151. According to some sources, he died about 168.

Ptolemy’s principal work on astronomy is The Great Mathematical Compilation of Astronomy, in 13 books; it is usually referred to by its Arabicized title, Almagest. Until the appearance of Copernicus’ De revolutionibus orbium coelestium (On the Revolutions of Heavenly Spheres), the Almagest remained the unsurpassed model exposition of the whole of astronomical knowledge. It was of exceptional practical importance for navigation and the determination of geographic coordinates. The laws of the apparent motions of the heavenly bodies were established with such precision in the Almagest that it became possible for the first time to predict the bodies’ positions. Attitudes toward Ptolemy’s work sharply changed in the early 17th century during the struggle for acceptance of the heliocentric system: the Almagest came to be viewed chiefly as a defense of the geocentric system. It was in this period, after the publication of the tables of Copernicus and, especially, of J. Kepler, that the work lost its practical importance.

Ptolemy’s Geography, in eight books, was also very well known. Between 1475 and 1600, 42 editions of it were published. It provided a complete and well systematized summary of the geographical knowledge of the ancient world. Ptolemy made a particularly great contribution to the development and application of the theory of cartographic projections. He gave the coordinates of 8,000 places, ranging in latitude from Scandinavia to the upper reaches of the Nile and in longitude from the Atlantic Ocean to Indochina. The coordinates were determined, however, almost exclusively by dead reckoning from reports of merchants and other travelers rather than by astronomical observation. One general map of the world and 26 regional maps are appended to the work.

In antiquity, astronomical observations were dated by the reigns of kings. Ptolemy compiled a chronological list called the Canon of Kings, which is an important source of chronological information. His five-volume treatise on optics had been believed lost until 1801, when a nearly complete Latin translation of it from the Arabic was found. The most interesting features of the work are Ptolemy’s theory of mirrors, tables of the angles of refraction of a light ray passing from the air into water and glass, and his theory and table for the refraction undergone in the earth’s atmosphere by light from heavenly bodies. Ptolemy’s other works are of less interest.


[Opera quae exstant omnia], vols. 1–2. Edited by J. L. Heiberg. Leipzig, 1898–1907.
[Geographia], vols. 1–2. Edited by C. Müller. Paris, 1883–1901.


Idel’son, N. I. “Etiudy po istorii planetnykh teorii.” In Nikolai Kopernik. Moscow-Leningrad, 1947. Pages 84–179.
The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.


(85–165) eminent Greek astronomer. [Gk. Hist.: Hall, 255]


captain of Jericho invites Simon Maccabeus and his sons to a banquet and then slays them. [O.T.: I Maccabees, 16:16]
Allusions—Cultural, Literary, Biblical, and Historical: A Thematic Dictionary. Copyright 2008 The Gale Group, Inc. All rights reserved.


Latin name Claudius Ptolemaeus. 2nd century ad, Greek astronomer, mathematician, and geographer. His Geography was the standard geographical textbook until the discoveries of the 15th century. His system of astronomy (see Ptolemaic system), as expounded in the Almagest, remained undisputed until the Copernican system was evolved
Collins Discovery Encyclopedia, 1st edition © HarperCollins Publishers 2005


A flexible foundation for the specification, simulation, and rapid prototyping of systems. It is an object-oriented framework within which diverse models of computation can co-exist and interact. For example, using Ptolemy a data-flow system can be easily connected to a hardware simulator which in turn may be connected to a discrete-event system. Because of this, Ptolemy can be used to model entire systems. In addition, Ptolemy now has code generation capabilities. From a flow graph description, Ptolemy can generate both C code and DSP assembly code for rapid prototyping. Note that code generation is not yet complete, and is included in the current release for demonstration purposes only.

Version 0.4.1 includes a graphical algorithm layout, code generator and simulator. It requires C++, C and has been ported to Sun-4, MIPS/Ultrix; DSP56001, DSP96002. Ptolemy is an active research project. Mailing list: E-mail: <>.
This article is provided by FOLDOC - Free Online Dictionary of Computing (
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He said that Ptolemy did not really draw maps, but used descriptive writings to bring them to life.
A compelling work of scholarship, Ptolemy's Philosophy demonstrates how Ptolemy situated mathematics at the very foundation of all philosophy-- theoretical and practical-- and advanced the mathematical way of life as the true path to human perfection.
This paper offers a close reading of Ptolemy's philosophical defense of the equant in Almagest 9.2.
Many of Ptolemy's Greek constellations are still in use today.
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His first articles on the eastern place-names of Ptolemy appeared more than fifty years ago (e.g., "Ptolemaios-Studien," WZKS 5 [1961]: 68-74), and he has regularly returned to the subject since.
Roberts considers first the fifteenth century's fascination with Ptolemy's text, which had been lost to the Christian West throughout the Middle Ages.
ON THIS DAY 721 BC: The first recorded eclipse was observed by the Babylonians, according to the Greek astronomer Ptolemy.
Ptolemy II leverages Coverity Scan to highlight the importance of software quality
Allen wrote that for Ptolemy the group was [tau][epsilon][tau][rho][alpha][pi][lambda][epsilon][upsilon][rho]ov (tetrapleuron), which translates to "quadrilateral." Subsequently, in his 1603 Uranometria, Johann Bayer converted Ptolemy's Greek into the low Latin terebellum, which appears in a few, later star atlases.