Sun, Mars, Jupiter and Saturn - moved around the Earth. Their positions to the stars were being calculated by combining circular motions. This system was what worked with the current physics of the time, although there were certain difficulties. However, these astronomers, who also saw themselves as mathematicians, were content to carry on calculating positions of planets. They figured they would leave it to natural philosophers to worry about whether the mathematical figures added up to the physical ones. Kepler, however, did not take like this attitude. His earliest published work in 1956 says that people should consider the actual paths of the planets, and not just the circles used to construct them. At Tubingen, Kepler studied Greek and Hebrew as well as mathematics. Ironically, at the end of his first year Kepler got A's in every subject except mathematics. It is supposed that Maestlin was trying to tell him he could do better, because Kepler was one of the select pupils that Maestlin chose to teach more advanced astronomy to. He was teaching them the new, heliocentric cosmological system that was formed by Copernicus. Kepler almost instantly accepted that the Copernican system was physically true. It seems that even in Kepler's student days there were signs that his religious beliefs were not entirely in tune with the orthodox Lutheranism religion that was prominent in Tubingen. This ties up with Kepler's astronomy because he apparently found difficulties in explaining how force from the Sun could affect the planets. In his writings, Kepler usually is known for laying his opinions on the line. This led officials at his university to doubt his religious beliefs. These might be why Maestlin persuaded Kepler to abandon plans for ordination and instead take up a post teaching mathematics in Graz. Religious intolerance began to become much more strict in the years to come. Kepler was asked to leave his church and his religion in 161...
