John Kepler was a German astronomer and mathematician who lived between 1671 and 1630. Kepler was a Copernican and initially believed that the planets should follow perfectly circular orbits (“John Kepler” 1). During this time period Ptolemy's geocentric theory of the solar system was accepted. Ptolemy's theory stated that the Earth is at the center of the universe and stationary; the closest to the Earth is the Moon, and beyond it, expanding outward, are Mercury, Venus and the Sun in a straight line, followed by Mars, Jupiter, Saturn and the “fixed stars”. The Ptolemaic system explained the many observed movements of the planets as having small spherical orbits called epicycles (“Astronomy” 2). Kepler is best known for introducing three effective, applicable, and valid laws of planetary motion using precise data he had developed from Tycho Brahe, a Danish astronomer, which helped Copernicus' theory of the solar system gain universal reception (“Johan Kepler ” 1). . However, he had made further effective contributions to the field of astronomy that were valuable to society and used to change the way the universe was perceived. John Kepler moved to Prague in 1600 where he worked as an assistant to Tycho Brahe, and eventually as the imperial mathematician to Rudolf II. Brahe allowed Kepler to see nothing more than a division of his capacious archives. Brahe entrusted Kepler with the task of understanding the orbit of the planet Mars, a predominantly difficult task. Ironically, it was the Martian data that allowed Kepler to develop the correct laws of planetary motion. Kepler was eventually forced to realize that the orbits of the planets were not the circles claimed by Aristotle and indirect assumptions...... middle of paper......inventors.about.com/library/inventors/bl_Johannes_Kepler. htm"John Kepler: The laws of planetary motion." Astronomy 161: The Solar System. Network. December 17, 2011. Johnson, Michele. "NASA - NASA's Kepler mission confirms its first planet in the habitable zone of a Sun-like star." NASA – Home. NASA, December 5, 2011. Web. December 17, 2011. http://www.nasa.gov/mission_pages/kepler/news/kepscicon-briefing.htmlMulder, Henry. "Tycho Brahe and Johannes Kepler." You and Science - Home - a site for making sense of how the world works and why. You and science, © 2000 - 2008 All rights reserved. Network. December 17, 2011. http://www.scienceandyou.org/articles/ess_21.shtml"Previous Posts - Mormonsandscience." Mormonsandscience - Blog about religion and science. April 19, 2011. Web. December 17, 2011. http://www.mormonsandscience.com/1/previous/2.html