Johannes 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 ("Johan Kepler" 1). During this 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 Moon is closest to Earth, and beyond it, extending 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 the precise data he had developed from Tycho Brahe, a Danish astronomer, which helped Copernicus's theory of the solar system achieve universal reception (“Johan Kepler” 1). . Nevertheless, he made other effective contributions in the field of astronomy, which are valuable to society and were used to change the way the universe was perceived. Johannes Kepler settled in Prague in 1600 where he worked as an assistant to Tycho Brahe, and eventually as the imperial mathematician to Rudolf II. Brahe only allowed Kepler to see part of his many files. Brahe gave Kepler the task of understanding the orbit of the planet Mars, which was mostly difficult. Ironically, it was precisely the Martian data that allowed Kepler to devise 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 assumed to be indirect...... middle of paper ......inventors.about.com/library/inventors/bl_Johannes_Kepler . htm "Johannes Kepler: The laws of planetary motion." Astronomy 161: The solar system. Internet. 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.html Mulder, Henry. “Tycho Brahe and Johannes Kepler.” Science and you - Home - a site to make sense of how the world works and why. Science and you, © 2000 - 2008 All rights reserved. Internet. December 17, 2011. http://www.scienceandyou.org/articles/ess_21.shtml “Previous Posts – Mormonsandscience.” Mormonsandscience - Religion and science blog. April 19, 2011. The web. December 17, 2011. http://www.mormonsandscience.com/1/previous/2.html