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Early Space Exploration
 
Nicolaus Copernicus (1473-1543)
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placed Sun at center of solar system
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showed Earth rotates on its axis once a day
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thought planets orbit in uniform circles (wrong!)
Johannes Kepler (1571-1630)
- discovered orbit of Mars was not circular
- concluded that planets move around the Sun in elliptical orbits with Sun not at the
center but at a focus
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