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The Greeks have long been involved with Astronomy. Even such great works as the Illiad refer to different constellations such as Orion and describes navigation by the stars.
During about 450 BC, Aristarchus of Samos theorized that motions in the sky could be explained due to the fact that the earth rotates on its axis once every 24 hours, and, as do other planets, revolves around the sun. Aristarchus's explanation was reject
ed by most philosophers and the geocentric system (the theory held at the time where the earth was a motionless globe around which the light revolves) would remain for another 2,000 years.
During the second century AD, the astronomers Hipparchus and Ptolemy determined the positions of approximately 1000 stars and used these positions to determine planetary
motion. Hipparchus and Ptolemy theorized that there were variations in the speed of
the sun and moon, and this was due to the sun and the moon revolving around a second circle, called an epicircle, the center of which was situated on the first.
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