Joseph Spradley writes:
Schooled not only in mathematics and astronomy but also in theology, [Johannes] Kepler initially intended to serve as a minister. However, in 1594 Lutheran authorities assigned him a job as a mathematics teacher in Graz, Austria. There his duties included compiling an annual calendar of astrological predictions, which he did with reluctance and cautious generality.
In 1596, Kepler published his Cosmographic Mystery, on the spacing of the planetary orbits. On the eve of its publication, he wrote to his astronomy teacher at the university of Tubingen, Michael Maestlin, "I am devoting my effort … for the glory of God, who wants to be recognized from the Book of Nature."
Kepler's efforts produced their most famous fruit in his first two laws of planetary motion, published in his 1609 masterpiece, The New Astronomy, and his third law of planetary motion, discovered in 1618. These laws set the stage for the emerging scientific revolution. Fifty years later, Isaac Newton's search for an underlying explanation for Kepler's laws led him to formulate his own law of universal gravitation.