Johannes Kepler and His Scientific Contributions By Katelyn Cooper Apprenticeship • Lived from 1571-1630 • German moved to Prague to become Brahe’s apprentice • Brahe told him to watch the orbit of Mars, so Brahe could continue with his theory on the solar system • He kept him occupied with the orbit of Mars because Brahe didn’t trust Kepler, he thought one day, Kepler would eclipse him as the premier astronomer of his time. Kepler’s Theory • Kepler believed in the Copernican System, which placed the sun directly in the center of the planets orbits. • Kepler realized Aristotle was wrong when he said that the orbits of planets were circular. In the system Copernican assumed they were circular also. • Kepler proved that the theory was not wrong but the shape of the orbit was, the orbits were flattened circles, also known as ellipses. First Law of Planetary Motion • Kepler’s first law stated that the sun was not the center of planet’s orbits but at one focus. • Which means the sun’s distance is constantly changing. Equal Area Law of Planetary Motion • The line joining the planet to the Sun sweeps out equal areas in equal times as the planet travels around the ellipse. • The planet moves faster when it is closer to the sun. • 2 parts: the perihelion and the aphelion Harmonic Law of Planetary Motion • The ratio of the squares of the revolutionary periods for two planets is equal to the ratio of the cubes of their semimajor axes. • Kepler's Third Law implies that the period for a planet to orbit the Sun increases rapidly with the radius of its orbit. • P represents the planet’s period of revolution • R represents the planets axis’ Interactive Sites • Kepler's First Law • Simulation of Orbit Bibliography • "Johannes Kepler: the Laws of Planetary Motion." Johannes Kepler: the Laws of Planetary Motion. 15 May 2006 <http://csep10.phys.utk.edu/astr161/lect/history/ kepler.html>. • Spaulding, Nancy E. Earth Science. Dallas: McDougal Littell, 1999. 405-406. • Porter, Roy, and Marilyn Ogilvie. Dictionary of Scientists. 3rd ed. Vol. 1. Great Brittain: Helican, 2000. 554-557.

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# Johannes Kepler and His Scientific Contributions