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Mysterium cosmographicum. View of an illustration of Johannes Kepler's Mysterium cosmographicum (Cosmographic mysteries, 1609). The illustration shows Kepler's idea of the relationship between the orbits of the planets known to him and the five regular polyhedrons. Kepler (1751-1630) worked as assistant to the Danish astronomer Tycho Brahe, whose 20-year archive of detailed observations he inherited when Brahe died in 1601. Failing to fit Brahe's data with the perfectly circular planetary orbits of Copernican theory, he deduced that the planets follow elliptical orbits around the Sun and move faster when close to the Sun.
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