Who is Johannes Kepler from Ideas and Opinions and what is their importance?

Johannes Kepler was a German mathematician and astronomer. He was the first to calculate the laws of planetary motion. He was also responsible for determining how the distance from the earth to the sun alters in the course of a year, using Mars' orbit for fixed triangulation. He then calculated the orbits and motions of the remaining planets, an immense task given the state of mathematics at the time. He next guesses at the laws governing these by trial and error, showing in the end both the mysterious harmony of nature and the need to compare the inventions of the intellect with observed fact.