Born in Weil, Wurttemberg, he studied theology and the classics at the University of Tubingen. He then moved to the University of Graz where he held the chair of astronomy and mathematics from 1594 to 1600. During this period, the Danish astronomer Tycho Brahe amassed detailed data on the movement of objects in the solar system. Kepler joined Brahe as an assistant at his observatory near Prague until the death of Brahe in 1601. Kepler was then promoted to the position Brahe had held as imperial mathematician and court astronomer to Rudolf II, Holy Roman Emperor.
While Pope Paul V was admonishing Galileo for pursuing the Copernican view that the earth was not at the center of the universe, Kepler was also becoming attracted to the Copernican system. Placing the sun at the center of the solar system provided a simpler mathematical explanation for the movement of the planets, and removed the perturbations and retrograde that was inadequately explained under the Ptolemaic system. The Copernican system was also the first to describe the precession of the equinoxes.
For a theologian to adopt a belief that was contrary to the position of the church required a new belief structure. Kepler became convinced that the work of God could be seen in mathematical harmony which explained the physical structure of the universe, rather than the other way around. His search for harmony brought him to also contradict Copernicus (and move farther away from the Ptolemaic system accepted by the church since the second century A.D.) by abandoning the belief that the planets moved in perfect circular orbits.
Ultimately, with the assistance of the detailed data collected by Tycho Brahe, Kepler formulated and verified three laws of planetary motion: 1) The planets orbit the sun in elliptical paths with the sun at one focus of the ellipse. 2) The area described in a planetary orbit by the sweep of a radius from the center of the planet to the center of the sun, is equal for equal time intervals of travel for the planet. Thus, the closer a planet comes to the sun, the more rapidly it moves. 3) The squares of the periods required for different planets to describe a complete orbit are proportional to the cubes of their mean distance from the sun.
Although the heavens had been observed since the start of mankind, Kepler was the first to increase the accuracy of prediction by providing a correct mathematical framework to describe the nature of the motion of orbiting objects. It should be noted, however, that Kepler did not attempt to explain why orbiting objects were held in an ellipse. He simply verified that this fact was true.
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