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Topic: Ptolemy


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  Claudius Ptolemy
Ptolemy used geometric models to predict the positions of the sun, moon, and planets, using combinations of circular motion known as epicycles.
This must be Ptolemy's greatest achievement in terms of an original contribution, since there does not appear to have been any satisfactory theoretical model to explain the rather complicated motions of the five planets before the Almagest.
Ptolemy combined the epicycle and eccentric methods to give his model for the motions of the planets.
www.stetson.edu /~efriedma/periodictable/html/Pm.html   (740 words)

  
  World Almanac for Kids
Ptolemy was probably born in Greece, but his actual name, Claudius Ptolemaeus, reflects all that is really known of him: “Ptolemaeus”; indicates that he was a resident of Egypt, and “Claudius”; signifies Roman citizenship.
Ptolemy also had to introduce, however, another mathematical device known as the equant: an imaginary point halfway between the center of the deferent and the eccentric point representing the earth’s position.
Ptolemy also contributed substantially to mathematics by advancing the study of trigonometry, and he applied his theories to the construction of astrolabes and sundials.
www.worldalmanacforkids.com /explore/space/ptolemy.html   (593 words)

  
 Ptolemy - Wikipedia, the free encyclopedia
Ptolemy was the author of several scientific treatises, three of which have been of continuing importance to later Islamic and European science.
Ptolemy formulated a geocentric model that was widely accepted until it was superseded by the heliocentric solar system of Copernicus.
Ptolemy was concerned to defend astrology by defining its limits, compiling astronomical data that he believed was reliable and dismissing practices (such as considering the numerological significance of names) that he believed to be without sound basis.
en.wikipedia.org /wiki/Ptolemy   (1879 words)

  
 Ptolemy I Soter - Wikipedia, the free encyclopedia
Ptolemy the Savior, 367 BC—283 BC) was a Macedonian general who became the ruler of Egypt (323 BC—283 BC) and founder of the Ptolemaic dynasty.
In 312, Ptolemy and Seleucus, the fugitive satrap of Babylonia, both invaded Syria, and defeated Demetrius Poliorcetes ("sieger of cities"), the son of Antigonus, in the Battle of Gaza.
Ptolemy I Soter died in 283 at the age of 84.
en.wikipedia.org /wiki/Ptolemy_I_of_Egypt   (1382 words)

  
 Ptolemy - Simple English Wikipedia
Ptolemy's system involved at least 80 epicycles to explain the motions of the Sun, the Moon, and the five planets known in his time.
Ptolemy of course knew that the Earth is a sphere.
Ptolemy's is the first known projection of the sphere onto a plane.
simple.wikipedia.org /wiki/Ptolemy   (531 words)

  
 Ptolemy - MSN Encarta
Ptolemy began by accepting the generally held theory that the earth did not move but was at the center of the universe.
Ptolemy proposed that the planets, sun, and moon moved in small circles around much larger circles, in which the earth was centered.
Ptolemy also contributed substantially to mathematics by advancing the study of trigonometry, and he applied his theories to the construction of astrolabes and sundials.
encarta.msn.com /encnet/refpages/RefArticle.aspx?refid=761562047   (551 words)

  
 Malaspina Great Books - Claudius Ptolemy (c. 85 CE)
Ptolemy in the next chapter indicates two means of determining this angle by observation, describes the instruments he employed for that purpose, and finds the same value which had already been found by Eratosthenes and used by Hipparchus.
Ptolemy, however, was the first writer of Antiquity who showed some conception of the relations between the Tanais or Don (usually considered by the ancients as the boundary between Europe and Asia) and the Rha or Volga,; which he correctly described as flowing into the Caspian.
Ptolemy especially devoted himself to the mathematical branch of his subject, and the arrangement of his work, in which his rcsults are presented in a tabular form, instead of being at once embodied in a map,; was undoubtedly designed to enable the student to construct his maps for himself.
www.malaspina.org /home.asp?topic=./search/details&lastpage=./search/results&ID=80   (8341 words)

  
 CATHOLIC ENCYCLOPEDIA: Ptolemy the Gnostic
Ptolemy states, cannot be attributed to the Supreme God, nor to the devil; nor does it proceed from one law-giver.
He is the creator of the universe, is neither perfect, nor the author of evil, but ought to be called just.
Ptolemy resorted to a fantastic system of eons.
www.newadvent.org /cathen/12553c.htm   (338 words)

  
 Ptolemy I Soter
Ptolemy was born in 367 as the son of a Macedonian nobleman named Lagus and a woman named Arsinoe, who may or may not have belonged to a minor branch of the Macedonian dynasty.
One of the anecdotes about Alexander's youth presents Ptolemy in exactly this function: after the battle of Chaeronea (338), in which Alexander's father Philip defeated the Greeks, Ptolemy advised Alexander to intervene in a marriage alliance concluded by Philip between his son Arridaeus and the daughter of the satrap of Caria, Pixodarus.
Ptolemy's whereabouts in the initial phase of the Sogdian war are not known, but in 328, he commanded one of five armies that forced the Sogdian population to give up their ancient way of life and settle in cities.
www.livius.org /ps-pz/ptolemies/ptolemy_i_soter.htm   (1067 words)

  
 Ptolemy's Table of Chords
Ptolemy began his discourse by calculating the chord lengths for the central angles corresponding to the sides of a regular inscribed decagon, hexagon, pentagon, square, and triangle.
Given the well-known impossibility of this trisection, Ptolemy decided instead to approximate the value of crd 1° by means of "a little lemma which, even if it may not suffice for determining chords in general, can yet in the case of very small ones, keep them indistinguishable from chords rigorously determined" (Ptolemy 28).
In the sexagesimal notation used by Ptolemy, the degrees symbol (°) refers to a unit of measure, the minutes symbol (') to one-sixtieth of the unit, and the seconds symbol (") to 1/3600th of the unit.
www.hypertextbook.com /eworld/chords.shtml   (1804 words)

  
 Ptolemy   (Site not responding. Last check: )
In Ptolemy's models, the motion of the outer planets was related to the motion of the Sun, because the radius of each planetary epicycle was set parallel to the line from the Earth to the Sun.
In Ptolemy's models, the motion of the inner planets (Venus and Mercury) was related to the motion of the Sun, because the center of each planetary epicycle was set on the same line (collinear) as the line from the Earth to the Sun.
Ptolemy argued that the Earth lies at the center of the universe because the celestial equator, the plane of the horizon, and other great circles bisect the heavens into equal hemispheres.
homepage.mac.com /kvmagruder/hsci/06-Roman/ptolemy.html   (996 words)

  
 pothos.org - All about Alexander the Great   (Site not responding. Last check: )
Ptolemy, however, had to wait until 330 BC when, in the aftermath of the Philotas affair, he was promoted to be one of the seven ‘somatophylakes’, the king’s closest bodyguard.
Ptolemy is credited with being in the town of the Malli, as one of those who defended Alexander’s wounded body until the rest of the army gained entry to the town — but this story appears in the Vulgate, while Ptolemy’s own history denies it (through Arrian).
Ptolemy’s probably most outrageous ‘lie’, that on the way to the oracle of Ammon Alexander’s party was saved by talking snakes, is so obviously propaganda designed to bolster his control of Egypt that it should be easy to forgive, or at least to accept without casting harsh aspersions on the rest of his account.
www.pothos.org /alexander.asp?ParaID=15   (1106 words)

  
 [No title]   (Site not responding. Last check: )
Ptolemy formulated a geocentric model (see: Ptolemaic system) of the solar system which remained the generally accepted model in the Western and Arab worlds until it was superseded by the heliocentric solar system of Copernicus.
Because Ptolemy derived most of his topographic coordinates by converting measured distances to angles, his maps get distorted.
Ptolemy was a disciple of the Gnostic Valentinus, known to us for writing a letter to a wealthy Christian lady named Flora, trying to convert her to the Valentinian faith.
wikiwhat.com /encyclopedia/p/pt/ptolemy.html   (823 words)

  
 Ptolemy's Table of Chords
Ptolemy began his discourse by calculating the chord lengths for the central angles corresponding to the sides of a regular inscribed decagon, hexagon, pentagon, square, and triangle.
With this theorem, Ptolemy produced three corollaries from which more chord lengths could be calculated: the chord of the difference of two arcs, the chord of half of an arc, and the chord of the sum of two arcs.
Given the well-known impossibility of this trisection, Ptolemy decided instead to approximate the value of crd 1° by means of "a little lemma which, even if it may not suffice for determining chords in general, can yet in the case of very small ones, keep them indistinguishable from chords rigorously determined" (Ptolemy 28).
hypertextbook.com /eworld/chords.shtml   (1804 words)

  
 Ptolemy - Facts, Information, and Encyclopedia Reference article
Ptolemy was the author of several scientific treatises, two of which have been of continuing importance to later Islamic and European science.
In the 15th century Ptolemy's Geographia began to be printed with engraved maps; an edition printed at Ulm in 1482 was the first one printed north of the Alps.
Ptolemy's treatise on astrology, the Tetrabiblos, was the most popular astrological work of antiquity and also enjoyed great influence in the bodies in the sublunar sphere.
www.startsurfing.com /encyclopedia/p/t/o/Ptolemy.html   (1249 words)

  
 Ptolemy's Trig Class
Ptolemy went further in his discussion, attempting to describe the locations of the stars in relevance to other stars.
Ptolemy's mathematics is based on a sexagesimal system or a base 60 system (as opposed to our base 10 system).
Ptolemy would write 1;12,30 to represent a group of 3600, 12 groups of 60, and 30 units.
www.bsu.edu /web/cvjones/AlgBridge/ptolemy.htm   (745 words)

  
 Ptolemy
At the time of Ptolemy's life, Alexandria was nearing a half millennium in age, and was already beginning to undergo the strife that later characterized the populace: the decimation of the Jewish population took place there during his lifetime.
At root, Ptolemy assumed that the presumption of an immobile earth was supported by the lack of evidence to the contrary (a negative proof is inherently invalid).
Ptolemy represented his own philosophical synthesis regarding astrology, which means that Ptolemy's astrological works cannot be assumed to be valid as a principal statement of the main development of Greek astrological thought.
www.olypen.com /wtallman/astrology/ptolemy.html   (2697 words)

  
 Ptolemy
Ptolemy (c.100-168) the Greek astronomer and the author of works on physics, mathematics, optics and geography, produced the data for creating a world map in about 150 AD.
Scholars in the 15th century recreated Ptolemy's map using the instructions in his work Geography, which explain how to project a sphere onto a flat piece of paper using a system of gridlines - longitude and latitude.
Ptolemy's map consists of the world known to him; he does not speculate on the unknown, and as he worked in Alexandria the map is most detailed round the Mediterranean.
www.empereur.com /ptolemy.html   (148 words)

  
 Ptolemy - Crystalinks
In the Almagest, one of the most influential books of classical antiquity, Ptolemy compiled the astronomical knowledge of the ancient Greek and Babylonian world; he relied mainly on the work of Hipparchus of three centuries earlier.
Ptolemy set up a public inscription at Canopus in Egypt in 147/148 C.E. The late N. Hamilton found that the version of Ptolemy's models set out in the Canopic Inscription was earlier than the version in Almagest.
Ptolemy was concerned to defend astrology by defining its limits, compiling astrological data that he believed was reliable and dismissing practices (such as considering the numerological significance of names) that he believed to be without sound basis.
www.crystalinks.com /ptolemy.html   (1568 words)

  
 The Galileo Project | Science | Ptolemaic System
Ptolemy used three basic constructions, the eccentric, the epicycle, and the equant.
With such combinations of constructions, Ptolemy was able to account for the motions of heavenly bodies within the standards of observational accuracy of his day.
Ptolemy's astronomy was taught as part of the undergraduate mathematical curriculum only and impinged only on technical questions of calendrics, positional predictions, and astrology.
galileo.rice.edu /sci/theories/ptolemaic_system.html   (1629 words)

  
 Skyscript: The Life & Work of Ptolemy by Deborah Houlding
Ptolemy described a spherical world, suspended freely in the centre of the universe, around which revolved the Moon, Mercury, Venus, Sun, Mars, Jupiter and Saturn respectively.
With the detailed information that Ptolemy had to work from, he was able to use the scheme as a basis for monitoring and predicting the positions of the planets with great accuracy.
To Ptolemy, therefore, astrology is a scientific study because it operates according to natural law.
www.skyscript.co.uk /ptolemy.html   (1468 words)

  
 Ptolemy, the Man
Ptolemy synthesized and extended Hipparchus's system of epicycles and eccentric circles to explain his geocentric theory of the solar system.
Ptolemy's system involved at least 80 epicycles to explain the motions of the Sun, the Moon, and the five planets known in his time.
Ptolemy of course knew that the Earth is a sphere.
obs.nineplanets.org /psc/theman.html   (486 words)

  
 PTOLEMY
Ptolemy was one of the greatest astronomer and geographer of ancient times.
Ptolemy placed the earth at the center of the universe, around it went the moon, sun, and planets at various speeds.
In addition Ptolemy wrote on geometry, a five-book treatise on optical phenomena, a three-book treatise on music, and eight books of geographical text and maps.
www.hyperhistory.com /online_n2/people_n2/persons3_n2/ptolemy.html   (112 words)

  
 Ptolemy I - Alexander The Great - General of Alexander - Founder of the Great Library of Alexandria - Ptolemy
Ptolemy was one of Alexander the Great's boyhood friends and became one of his most trusted generals.
Ptolemy had Alexander's body brought for burial to Egypt, where it was permanently interred at the city Alexander had founded and named after himself.
Ptolemy established his capital at Alexandria where he founded a museum and started collecting books for a great library, which was to become the centre for scientific research and the best collection of Greek and Roman papyri in the world.
www.alexander-the-great.co.uk /ptolemy.htm   (255 words)

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