from the King of Prussia, Frederick II, to build an observatory and make as many accurate observations as possible to be recorded. This constituted the greatest portion of Tychos life. He also proposed a slightly modified version of the Copernican system, where all the planets revolved around the sun, except for earth, in which the sun revolved around. Tycho Brahes accomplishments with such a limited source of tools and knowledge is considered one of the greatest achievements of the Renaissance. He died in 1610, and is still considered to be the greatest astronomer before telescopes. Luckily, he left all of his work to Kepler. The German scientist Kepler, born in Weil, Germany in 1571, was the founder of three laws of planetary orbit in the solar system. After graduating from the University of Tubingen, which is where he learned the Copernican theory, began as a teacher at a Lutheran school in Graz, Austia, but soon left for religious persecutions. He soon becomes the assistant of Tycho Brahe in the Prague. Even after the death of his mentor Brahe, Kepler still firmly believed in the Copernican model. To honor his lost mentor, Kepler attempted to find the orbit of Mars to fit the calculations of Brahe. The belief at this time was that the planets moved in perfect circular order, but Kepler could not find proof of this. So Kepler used an ellipse instead, and to his benefit, discovered that it worked. Following the work of Brahe, Kepler stated his three laws of planetary motion. The first law stated that each planetary orbit is an ellipse with the sun as the focus point and the other focuses an empty point in space. His second law stated that each of the planets revolve around the sun in a line so that the sun will affect equal areas of the planet at equal times. These two laws were published in Keplers Astronomia Nova. The final of Keplers laws states that the square of the sidereal period of any planet is directly proportional to the cu...
