views updated Jun 08 2018


PTOLEMY (c. 100170), Alexandrian astronomer, geographer, and mathematician. The last of the great astronomers of antiquity, Claudius Ptolemaeus (Ptolemy) compiled works that remained the standard astronomical textbooks until the Copernican revolution in astronomy in the sixteenth century. Almost nothing is known of the details of Ptolemy's life. His Hē mathēmatikē syntaxis (Mathematical Compilation) was written about 150 ce; the title by which this work is better known, the Almagest, is a medieval Latin derivation from an Arabic corruption of the Greek title under which the work came to be known in later antiquity, Ho megale syntaxis (The Great Compilation). The Almagest sums up the mathematical astronomy of the ancient world; it became the basis of Latin and Arabic astronomy.

Ptolemy's work follows in the Greek philosophical tradition, in which the sacred nature of the heavens is expressed by the incorruptibility of the celestial realm, the divinity of the heavenly bodies, and the perfection of their motions (uniformly circular, because the circle was considered the most perfect of figures and motion around a circle was eternal). The fact that the motions of the sun, moon, and planets are evidently not circular provided a formidable challenge to thinkers within this tradition; especially challenging were the planets' periodic reverses, or retrograde motions. Drawing upon the work of his Greek predecessors, Ptolemy was able to "save the appearances" of celestial motion by using circles in his geometry of the heavens. By employing Greek and Babylonian observational data, he was able to adjust his theoretical solutions to observed celestial positions and to predict them with a precision unmatched until the work of Johannes Kepler in the seventeenth century. The geometrical devices that Ptolemy usedthe eccentric, the epicycle, and the equantwere never thought to possess a physical reality, as he makes clear in the preface to the Almagest. But it was just for this reason that astronomy had a religious value. Astronomy developed the correspondence between the order of divine celestial things and the order of mathematical propositions.

Its science Aristotelian and its format Euclidean, the Almagest describes a stationary, spherical earth surrounded by concentric spheres carrying the sun, moon, planets, and stars. Motion is described geometrically by arrangements of several kinds of circles: (1) eccentrics, which are not centered on the earth; (2) epicycles, which orbit other circles that are centered on the earth; and (3) equants, in which the motion of the body on the circle is variable in relation to the center of the circle but uniform in relation to some noncentral point within the circle. The Almagest includes a star catalog and a table of observations later revised and expanded in Ptolemy's Prokheiroi kanones (Handy Tables).

Ptolemy's work on geometry, the Planisphaerium, of which only a distorted Greek title survives, Exaplōsis epiphaneias sphairas (Unfolding of a Spherical Surface), details the theory of the astrolabe, the chief astronomical instrument of antiquity and the Middle Ages. Ptolemy's Hypotheseis tōn planōmenon (Planetary Hypotheses) suggests that the spheres of the planets nestle within one another. The astrological complement to Ptolemy's astronomy is his Tetrabiblios. Ptolemy also wrote works on optics and music, as well as a Geography (Gr., Geographikē hyphēgēsis ), which gives directions on how to map the spherical earth on a flat surface and provides tables of longitude and latitude for generating maps. Because of a lack of precise longitude, Ptolemy's map of the known world was severely distorted, even where descriptive information abounded.

Ptolemy's works present an interrelated whole dominated by the successful application of mathematics to complex technical problems. For example, the determination of terrestrial latitude in the Geography is achieved through calculations based on astronomy. This in turn specifies the astrological character of the inhabitants of various parts of the earth. His cartography employs the mathematics of his optics and of the Planisphaerium. Ptolemy's authority in applied mathematics was undisputed for more than a millennium.

Ptolemy went to great lengths in his texts to provide procedures whereby his technical achievements could be reproduced. He thus laid the foundation for other civilizations to assimilate his work, become expert at it, and progress beyond it. Such cultural innovation is invariably associated with religious creativity, though not in a predictable fashion. For example, though Ptolemy's astronomy was used to corroborate the religious view that the earth was at the center of the universe, no one was ever convinced of this view because of the astronomy of eccentrics, epicycles, and equants. However, becoming technically expert in these devices did allow the accurate prediction of religious feasts. Although the Jewish philosopher Maimonides (Mosheh ben Maimon, 1135/81204) criticized Ptolemy, he did incorporate some of the astronomer's techniques for determining the date of Passover.

The translation of Ptolemy's work into Arabic in the ninth century was a catalyst for the flowering of Islamic culture. Refined astronomical tables were created, such as the Toledan Tables of al-Zarālla (c. 1080). This served as the basis for the Alfonsine Tables, which was compiled circa 1252 by some fifty astronomers assembled for that purpose by Alfonso X of Castile, and which predicted the dates of the Easter moon. New theories of optics were proposed by the Arab heritors of Ptolemy; new geographical values were established. The Islamic appropriation of Hellenistic natural philosophy inspired the Christian Middle Ages. A desire for the Almagest brought the greatest of medieval translators of Arabic, Gerard of Cremona (11141187), to Toledo. The merits of a true physical astronomy and of "saving the appearances" by geometry were argued in medieval universities, where Ptolemaic astronomy became part of the curriculum. Although the celestial bodies were no longer thought of as gods by medieval Europeans, their movement was believed to exhibit God's will (and their order his wisdom), and hence Ptolemy's astronomy continued to provide for the intellectual contemplation of the divine celestial order. Dante drew upon Ptolemy for the cosmology of his Commedia (1321).

When the Geography, with its techniques of projection, was first translated into Latin in fifteenth-century Florence, it contributed to the rediscovery of linear perspective and to the development of cartography during the voyages of exploration. Because the distortions of Ptolemy's map of the globe bore the prestige of his mathematics, Columbus and others were convinced that it would be quite easy to reach Asia by sailing west. When Renaissance astronomers finally became truly competent in Ptolemy's astronomy, their dissatisfaction with his accuracy and methods culminated in the Copernican revolution that established modern cosmology. The Jesuit mission to China in the seventeenth century used the predictive precision of Ptolemaic astronomy to enhance the value of their religious teaching at the emperor's court. Thus it was ironic that Ptolemy's science and technology were helping to introduce Christianity to the Far East at the same time that Copernican astronomy was making Ptolemaic astronomy obsolete in the West. And well after Ptolemy's cosmos was superseded by the physical universe as defined by Copernicus, Newton, and others, the Tetrabiblios remained an astrological standard. It was translated into English and published in 1701, the second edition in 1786.


A translation of Ptolemy's Almagest was done by R. Catesby Taliaferro in Ptolemy, Copernicus, Kepler, vol. 16 of the "Great Books of the Western World," edited by Robert Maynard Hutchins (Chicago, 1952). The inclusion of the De revolutionibus by Copernicus in the same text facilitates the comparison of these two all-important works in the history of astronomy. A scrupulous new translation of the Almagest is provided in G. J. Toomer's Ptolemy's Almagest (London, 1984). Frank E. Robbins translated the Tetrabiblios for the "Loeb Classical Library" (Cambridge, Mass., 1940). An English translation of the Latin Geographia is found in Edward Luther Stevenson's Geography of Claudius Ptolemy (New York, 1933). An exhaustive technical account of the Almagest and its historical antecedents is provided in Otto Neugebauer's A History of Ancient Mathematical Astronomy, vol. 1 (New York, 1975). G. J. Toomer, in his article "Ptolemy, Claudius," in the Dictionary of Scientific Biography (New York, 19701980), gives a concise description of Ptolemy's science with an up-to-date bibliography. A very readable discussion of the problems posed by observational astronomy and the Greek solutions to them, as well as of their cultural context, is provided in Thomas Kuhn's The Copernican Revolution: Planetary Astronomy in the Development of Western Thought, rev. ed. (New York, 1959).

Michael A. Kerze (1987)


views updated May 21 2018


PTOLEMY , the common name of monarchs of the Macedonian (or Thirty-First) Dynasty who ruled in Egypt from 323 to 30 b.c.e. It is unclear precisely how many such sovereigns there actually were; some scholars give a total of 14 and some 16. Most important for Jewish history were: ptolemy i (called Soter), reputed son of Lagus, founder of the dynasty. Ruler of Egypt as satrap from 323 b.c.e., he assumed the title of king in 305 and remained in power until his death in 283. Josephus states (Apion, 1:209ff., and cf. Ant. 12:2ff.) on the authority of Agatharchides of Cnidus that Ptolemy, after gaining admittance to Jerusalem on the pretext of wishing to make a sacrifice, captured the city on the Sabbath day when the Jews did not fight (320 b.c.e.). Agatharchides comments derisively that the Jews "persevering in their folly" of not defending their city on this day, were given over to a "harsh master." The second part of his statement is of especial interest, for scholars differ over whether Ptolemy was indeed a "harsh" master or whether his attitude toward the Jews was essentially benevolent. Whether the Jews in Egypt during his reign were indeed granted equal rights with Macedonian clerouchoi ("settlers") must remain an open question.

ptolemy ii (called Philadelphus) reigned from 283 to 245 b.c.e. According to the Letter of *Aristeas he was responsible for two important actions, the one of immediate and the other of lasting consequence: he freed numerous Jewish slaves (themselves evidence of his father's military actions in Palestine) and initiated the Greek translation of the Bible – the *Septuagint. Both the foregoing statements may well have a historical basis. Philadelphus' literary interests are attested from other sources, and the Bible project may conceivably have been begun during his reign. The construction of several cities in Ereẓ Israel must also be attributed to his reign, including Philoteria (near Lake Kinneret) and Ptolemais, near present-day Acre (Arist. 115) as well as Philadelphia in Transjordan. He gained important victories in the first Syrian war against the Seleucid sovereign, *Antiochusi, and gave his daughter Berenice's hand in marriage to Antiochus ii upon completion of the second Syrian campaign (c. 253 b.c.e.).

ptolemy iii (called Euergetes) reigned from 246 to 221 b.c.e. Some scholars identify this Ptolemy with the king of that name mentioned by Josephus with regard to Joseph the Tobiad (Ant. 12: 154ff.), while others are of the opinion that it was Ptolemy v (Epiphanes). If the king was Euergetes, then he must be credited with a favorable attitude toward his Jewish subjects. Josephus goes so far as to claim that after Euergetes' great victory over the Seleucids during the third Syrian war (246–241 b.c.e.) he offered incense at the Temple in Jerusalem. A possible reference to some of the king's actions during and after his campaigns in the Seleucid realm may be found in Daniel 11:7–9 where it is related that the Egyptian king removed idols from the conquered territories and restored them in his own country.

ptolemy iv (called Philopator) reigned from 221–203 b.c.e. A "wretched debauchee" according to E. Bevan, this monarch has fared less well than his predecessors in Jewish annals. Philopator is often associated with the following events described in iii Maccabees: On the conclusion of the (fourth Syrian) war and his victory over Antiochus at Raphia (present-day Rafa) in 217 b.c.e., Philopator paid a visit to Jerusalem with the intention of entering the Temple. God intervened and he was felled to the ground. As revenge, when he returned to Egypt he ordered the Jews to be massacred in the Alexandrian arena by a horde of elephants, but the beasts turned on the royal troops instead. The day of deliverance was commemorated by the Jews as an annual feast day, which seems to be the only historically verifiable aspect of the story, though Josephus places it in a later context.

ptolemy v (called Epiphanes) reigned from 203 to 181 B.C.E. This monarch irretrievably lost the whole of Palestine to Antiochus iii at the battle of Paneas (present-day Banias) c. 200 b.c.e.

ptolemy vi (or vii; called Philometor) reigned from 181 to 145 b.c.e. (from then on until the death of the last of the Ptolemies in 30 b.c.e., dates of birth and regnal years become increasingly uncertain). Philometor appears to have been generally well disposed toward the Jews, though he invaded Palestine to intervene in the disputes over the succession to the Syrian throne. His relations with *Jonathan the Hasmonean were cordial. ii Maccabees 1–10 states that Philometor's mentor was a Jewish philosopher and biblical exegete, Aristobulus by name. Under this same ruler the high priest *Oniasiv, having fled from Jerusalem, built a temple at Leontopolis (c. 161 b.c.e.), while Philometor's military garrisons were commanded by two Jews, Onias and Dositheus.

ptolemy vii (or ix; called Euergetes ii) reigned from 145 to 116 b.c.e. According to Josephus the Jews were persecuted during his rule, yet a synagogue was dedicated to him by the Egyptian Jewish community. It was in the 38th year of Euergetes' reign that the grandson of *Ben Sira went to Egypt where he translated his grandfather's work into Greek.

ptolemy viii (or x; called Lathyrus and Soter ii) reigned intermittently from 116 to 80 b.c.e. He launched an attack on the Hasmonean Alexander *Yannai shortly after the latter had come to the throne, only to be driven back by his mother, *Cleopatraiii, who, with his brother Ptolemy ix (or xi; called Alexander i), later planned their own assault on Yannai.


A. Bouché-Leclercq, Histoire des Lagides, 4 vols. (1903–07), passim; Schuerer, Gesch, 3 (19094), 24–52; E.R. Bevan, A History of Egypt… (1927), passim; Schalit, in: Scripta Hierosolymitana, 1 (1954), 64–77; J. Gutman, Ha-Sifrut ha-Yehudit-ha-Hellenistit, 1 (1958), 115ff.; V. Tcherikover, Hellenistic Civilization and the Jews (1959), index; M. Stern, Ha-Te'udot le-Mered ha-Ḥashmona'im (1965), 11–27; W.W. Tarn and G.T. Griffith, Hellenistic Civilization (19663), passim.

[David Solomon]

Ptolemy (CA. 100-170)

views updated May 11 2018

Ptolemy (ca. 100-170)

Greek astronomer

Very little is known about Ptolemy's early life. Born in Alexandria, Egypt, as Ptolemais Hermii, his name was later latinized as Claudius Ptolemaeus, and later Ptolemy.

Ptolemy's chief contribution to science is a series of books in which he compiled the knowledge of the ancient Greeks, his primary source being Hipparchus (fl. second centuryb.c.). Because most of Hipparchus' writings have not survived from antiquity, many of the ideas he espoused about the universe have become known as the Ptolemaic system.

Ptolemy's system placed Earth directly at the center of the universe. The Sun, Moon and planets all orbited Earth. However, since such a scheme did not match the observed motions of the planets, Ptolemy added small orbits to the planets called epicycles, and introduced other mathematical devices to make a better fit.

Despite its errors and complications, the Ptolemaic system was adequate enough to make predictions of planetary positions, and it influenced thinking for 1,400 years. It was not until 1543 that Polish astronomer Nicolaus Copernicus (14731543) published his book refuting the Ptolemaic system. After Danish astronomer Tycho Brahe's (15461601) exceptionally accurate measurements of the positions of the planets showed Ptolemy's system was inaccurate, it fell upon German astronomer and mathematician Johannes Kepler (15711630) to devise a better explanation of planetary orbits.

Hipparchus had made a catalogue of stars, which were grouped into 48 constellations. Ptolemy placed them in his book and gave these patterns the names that are still in use today. He also included Hipparchus'work on trigonometry, his estimate of the distance between Earth and the Moon, which was fairly accurate, as well as Aristarchus' (third centuryb.c.) incorrect estimate of Earth's distance from the Sun.

Ptolemy's book was entitled Mega (mathematike) syntaxis ("Great [mathematical] compilation") although Mega was sometimes replaced by Megiste ("Greatest"). When the Arabs adopted the work, they called it Al-majisti ("The Greatest"), which it is known as today. It was translated into Latin in 1175 (as "Almagesti" or "Almagestum") and dominated European thinking for four centuries.

In the field of optics, Ptolemy wrote about the reflection and refraction of light. He lists tables for the refraction of light as it passes into water at different angles. Another book, Tetrabiblos, is a serious treatment of astrology.

Ptolemy also wrote a treatise that dealt with geography and included maps as well as tables of latitude and longitude . It explained how those lines could be mathematically determined, but only a few latitudes were calculated. He had accepted Poseidonius' (ca. 13551 b.c.) erroneously small estimate of the size of Earth, instead of Eratosthenes' (ca. 276194 b.c.) more accurate figure, and Ptolemy unwittingly may have altered the history of the world. After his geography had been translated into Latin, it eventually came to the attention of Christopher Columbus (14511506), who accepted the incorrect size and concluded that his search for a short-cut to Asia was possible.

See also History of exploration I (Ancient and classical); History of exploration II (Age of exploration)


views updated Jun 11 2018


c. 100-c. 170

Greek Astronomer and Geographer

Ptolemy is known historically through his written works. His earliest and most noted treatise is the 13-volume set commonly known as the Almagest, which he probably wrote around 150. In these books, he pinpointed the location of more than 1,000 stars, identified the so-called "classical 48" constellations, explained how to calculate latitude and longitude, and predicted solar and lunar eclipses. He also used often complicated mathematical models to help explain the movements of the various celestial bodies. The complexity, in part, derived from his belief that Earth was at the center of the universe, and all stars and planets revolved around Earth.

For example, Ptolemy developed an interesting system to explain why the planets usually, but not always, appear to move forward in their paths across the night sky. Under the erroneous assumption that the planets revolve around Earth, Ptolemy resorted to planetary movements known as epicycles to explain the path abnormalities.

Ptolemy's epicycle hypothesis persisted for well more than 1,000 years. Eventually, however, astronomers understood that the planets only appear to backtrack when viewed from Earth. This illusion results because the planets revolve around the Sun in different orbits and at different speeds. Earth passes a planet in an outer orbit much like a race car passes another in an outer lane. To bystanders in the stands surrounding the race track, it is clear that both cars are moving forward in their paths around the track. The view from the inner car is different. If a video camera were mounted on the car's fender, it would record the outer car apparently slowing as the inner car approached. As the inner car reached and passed the outer car, the video would show the outer car momentarily stopping before beginning to go backward. As the distance between the two cars increased, the camera would eventually see the outer car apparently cease its reversal and begin again to gain forward speed. Likewise, when viewed from Earth, other planets move across the sky at a relatively constant speeds most of the time, but occasionally appear to slow down, remain still, and then backtrack before regaining a forward trajectory.

While the underlying notion of Earth as the middle of the universe was incorrect, Ptolemy's intricate mathematical models were very precise in predicting celestial movements as viewed from this planet.

Ptolemy was also very interested in astrology and the impact of planetary position on human society. His four-volume Apotelesmatica became a primary reference for horoscope readers.

More notable from a scientific perspective, however, were Ptolemy's contributions to geography. His Geography, an eight-volume set, listed the latitude and longitude for many major localities, included a wealth of regional cultural information, and also presented mathematical models describing how to depict the spherical Earth on a two-dimensional map.

Ptolemy also used mathematics in music theory and optics, but the most influential by far were his contributions to astronomy and geography. Ptolemy's work left an imprint on these fields for hundreds of years. His conclusions prevailed well into the sixteenth and seventeenth centuries, when—largely through the studies of Nicolaus Copernicus—the scientific community finally stripped Earth of its central placement in the universe and modern astronomy began.



views updated May 09 2018


PTOLEMY (c. 135 b.c.e.), son of Ḥabub (Abubus) and son-in-law of *Simeon b. Mattathias (the Hasmonean). Ptolemy was strategos (i.e., military and local commander) at Jericho. Plotting to overthrow the Hasmonean House in 135 b.c.e., he invited Simeon and his entourage to a banquet while they were on a visit to the Jericho area, and treacherously murdered him and later two of his sons. He then sent messengers to Gazara (Gezer) to kill Simeon's other son John *Hyrcanus. At the same time, he set out to capture Jerusalem, dispatching a message to the Syrian king, Antiochus Sidetes, to inform him of the developments and to enlist his aid. Hyrcanus succeeded, however, in killing his assailants and hastened to Jerusalem where he won the trust of the people, who remained loyal to the Hasmonean dynasty. Having ensured his succession, Hyrcanus pursued Ptolemy and besieged him in a fortress in the vicinity of Jericho to which he had retreated. Ptolemy was able to defy Hyrcanus by holding his mother as a hostage. Eventually Hyrcanus had to lift the siege as a result of the onset of the Sabbatical year which led to a food shortage. Ptolemy fled to Philadelphia (Rabbath Ammon), after putting Hyrcanus' mother to death, and he is not heard of again.


i Macc. 16; Jos., Ant., 13:228–35; Jos., Wars, 1:54–60; Schuerer, Hist, 66–68.

[Lea Roth]


views updated May 14 2018

Ptolemy (ad 90–168) ( Claudius Ptolemaeus) Greek astronomer and geographer. He worked at the library of Alexandria, Egypt. Ptolemy's chief astronomical work, the Almagest, drew heavily on the work of Hipparchus. The Ptolemaic system is based on the geocentric world system of the ancient Greeks. His Geography, which provided the basis for a world map, was a definitive text until the Renaissance.


views updated Jun 27 2018

Ptolemy2 (2nd century), Greek astronomer and geographer. His teachings had enormous influence on medieval thought, the geocentric view of the cosmos (the Ptolemaic system outlined in his major work Almagest) being adopted as Christian doctrine until the late Renaissance. Ptolemy's Geography, giving lists of places with their longitudes and latitudes, was also a standard work for centuries, despite its inaccuracies.


views updated May 18 2018

Ptolemy1 the name of all the Macedonian rulers of Egypt, a dynasty founded by Ptolemy, the close friend and general of Alexander the Great, who took charge of Egypt after the latter's death and declared himself king ( Ptolemy I) in 304 bc. The dynasty ended with the death of Cleopatra in 30 bc.