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SPACE EXPLORATION
Lesson 1 - Page 3

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Nicholas Copernicus (1473-1543) disposed of the Earth as the Universe's center, by placing the Sun in the central position, with the planets (including Earth) revolving around the Sun. Although Copernicus tried to maintain some of the Ptolemaic epicycles, his work marks a new era of the "Heliocentric" theory. Tycho Brahe (1546-1601), financed by the King of Denmark, used a wall quadrant and sextant that measured star and planet locations accurately. This was modern equipment for this time. He noticed that the stars were farther than previously imagined.

Johannes Kepler (1571-1630) using Tycho's records, developed 3 laws of planetary motion. Kepler's laws outline that the orbit of planets are elliptical with the Sun as the focus point; that planets revolve around the Sun over equal areas; and there is a mathematical relationship of how far the planets are from the Sun. Eyesight was still the most important tool that humans had to explore the sky.

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