Johannes Kepler (1571–1630) composed a mathematically precise theory of the Copernican system, and Tycho Brahe (1546–1601) furnished the measurements that constituted the factual data for the Copernican theory. Kepler’s theoretical work was what completed the Copernican system. Kepler offered a religious explanation for the spacing of the planets and postulated a driving force centered in the Sun, which diminished with distance, as the cause of planetary movement.