... also noted eclipses. The ancient Greeks carried forward ideas from the Babylonians and invented some of their own. Aristotle's system of physics and astronomy, developed in the 300's BC, survived for almost 2,000 years. In Aristotle's system of astronomy, earth was the center of the universe. During the AD 100's Ptolemy modified Aristotle's system to account for the retrograde motion of the planets. Ptolemy also ... AD Vega in the constellation of Lyra will mark the Pole. The composition by weight of the average star is about 70% hydrogen, 28% helium, 1.5% carbon, nitrogen, oxygen, and ...

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• Approx Pages: 22
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• Grade Level: High School