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SR-17-Kepler-laws(1) - A Z Sun planet After trying complex...

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Kepler’s laws of planetary motion 1600 — Kepler joined Tycho’s staff at Prague and set out to ‘solve’ the motion of Mars. He published his revolutionary results in his Astronomia Nova (1609). Kepler found he could not fit Tycho’s data accurately enough using traditional methods of eccentrics, equants, and epicycles. This led him to take a radical step: he dropped the assumption that planets move in perfect circles at uniform speeds. He found that planets speed up and slow down in their orbits in accordance with the ‘equal areas law’ : a line from Sun to the planet sweeps out equal areas in equal times. Kepler's equal areas law a b y z The line from the planet to the Sun sweeps out equal areas in equal times; thus, if the time for the planet to go from a to b is equal to the time for it to go from y to z, area A will equal area Z.
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Unformatted text preview: A Z Sun planet After trying complex egg-shaped curves, Kepler concluded that the orbit of Mars is a relatively simple ellipse. He then formulated his ‘elliptical orbits law’: all of the planets orbit the Sun in ellipses , with the Sun at one focus. With his ‘third law’ (D 3 /T 2 = K), published in Harmonices Mundi (1619), Kepler linked the orbital distances and periods of all planets. 1621 — Kepler brings out Epitome of Copernican Astronomy : most accessible account of his improved version of heliocentric theory. 1627 — Kepler finally published his Rudolphine Tables , based on his system of Sun-centered elliptical orbits. Here for the first time a heliocentric model yielded predictions for the motions of the planets that were far more accurate than those derived from existing geocentric models....
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