The Copernican Revolution and Its Philosophical Consequences

Nicolaus Copernicus (1473–1543), a Polish canon, astronomer, and physician educated at the universities of Kraków, Bologna, and Padua, presented a fully developed mathematical model of a heliocentric cosmos in his De Revolutionibus Orbium Coelestium ("On the Revolutions of the Heavenly Spheres"), published in Nuremberg in 1543, reportedly reaching Copernicus on his deathbed. The work proposed that the Sun, not the Earth, occupies the center of the cosmos, with the Earth reduced to one planet among several, orbiting the Sun annually while also rotating daily on its own axis to account for the observed rising and setting of stars and the Sun. Copernicus retained several features of the older Ptolemaic and Aristotelian cosmology, including the assumption of perfectly circular planetary orbits (requiring him, like Ptolemy, still to employ auxiliary epicycles to fit observed planetary motion precisely) and a bounded, if considerably enlarged, sphere of fixed stars — his revolution was thus more radical in its rearrangement of the cosmos's center than in its abandonment of ancient geometric assumptions about celestial motion.