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Aristarchus (310-230 BC) was a Greek astronomer and mathematician. He presented the first known heliocentric model of the solar system, placing the Sun, at the center of the known universe, and put the other planets in their correct order of distance around the Sun. His astronomical ideas were rejected in favor of the geocentric theories of Aristotle and Ptolemy. The heliocentric theory was successfully revived 1800 years later by Copernicus, after which Johannes Kepler and Isaac Newton gave the theoretical explanation based on laws of physics. No artist credited, undated.