Born in Wurttemburg, Germany, Johannes Kepler was the son of a soldier of fortune who eventually deserted his family. Kepler is widely known for his three laws of planetary motion. Kepler began to think about astronomy and planetary motion as a schoolteacher in Graz, Austria and published his first work, Mysterium Cosmographicum, in 1596. He became an apprentice to Tcho Brahe, whose collection of astronomical observations was the best of its kind. Kepler's work on Mars, in which he tried to fit a theory to the observations, led to his discovery that planetary motion is elliptical rather than circular. Kepler's life was somewhat chaotic as a result of the repeated harassment of Protestant teachers in predominantly Catholic Austria. Some of his ideas about cosmic harmonies, such as the theory that the spacing of planetary orbits is related to the five regular polyhedrons, were incorrect. Yet his basic approach of seeking a broad sense of order and harmony in the world led to the discovery of mathematical regularities involved in planetary motion, and ultimately, to the elegance of Sir Isaac Newton's laws of motion. Kepler's Somnium, a fictional account of a voyage to the moon, is cited by historians of rocketry as an early work of science fiction that might have stimulated interest in space travel.