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Ptolemy, Astronomer / Geographer > 
Claudius Ptolemy lived in Alexandria (in Egypt) from approx. 87 -150 AD. He was an astronomer, mathematician and geographer. He codified the Greek geocentric view of the universe, and rationalized the apparent motions of the planets as they were known in his time.
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. He believed the planets and sun to orbit the Earth in the order Mercury, Venus, Sun, Mars, Jupiter, Saturn . This system became known as the Ptolemaic system. It predicts the positions of the planets accurately enough for naked-eye observations This is described in the book Mathematical Syntaxis (widely called the Almagest), a thirteen book mathematical treatment of the phenomena of astronomy. It contains a myriad of information ranging from earth conceptions to sun, moon, and star movement as well as eclipses and a breakdown on the length of months. The Almagest also included a star catalog containing 48 constellations, using the names we still use today.
In addition to his well known works in astronomy, Ptolemy was very important in the history of geography and cartography. Ptolemy of course knew that the Earth is a sphere. Ptolemy's is the first known projection of the sphere onto a plane. His Geography remained the principal work on the subject until thetime of Columbus. But he had Asia extending much too far east, which may have been a factor in Columbus's decision to sail west for the Indies.
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More on this Website >
• http://nineplanets.org/psc/theman.html
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Ptolemy I, Founder Ptolemaic Dynasty
Ptolemy I Soter: friend and biographer of the Macedonian conqueror Alexander the Great, after his death king of Egypt, founder of the the Ptolemaic dynasty, one of the Di... |
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The Ptolemies, Last Indept. Dynasty Egypt
Ptolemies: name of the last dynasty of independent Egypt. In 332, the Macedonian king Alexander the Great conquered Egypt and gave a new capital to the old kingdom along... |
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Hipparchus, Astronomer
Hipparchus was the most important Greek astronomers of his time. He very accurately cataloged over 1,000 stars and invented the mathematical science of trigonometry. Ptol... |
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Heron of Alexandria, Inventor Steam Engine
Heron of Alexandria was an ancient Greek mathematician who was a resident of a Roman province (Ptolemaic Egypt); he was also an engineer who was active in his hometown of... |
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Almagest, Ptolemy
The main desire of Ptolemy in writing his Almagest is to explain and account for the motions of the apparently erratic celestial beings in terms of perfect and circular m... |
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Regiomontanus, Astronomer / Mathematician
Regiomontanus, real name Johannes Müller, a mathematician and astronomer, was a priest who studied in Vienna and in Rome, acquiring in addition to mathematical skills a k... |
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Gerardus Mercator, Cartographer
Gerardus Mercator, Flemish cartographer. He received a master's degree in 1532 from the University of Louvain (Belgium), where he settled. By 24 he was a skilled engraver... |
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