Copernicus, Nicolaus

(1473-1543)

   Polish astronomer, best known for his theory of the universe that placed the sun, rather than the earth, at the center of the system. Born in the Polish city of Torún and orphaned at an early age, Copernicus was supported by an uncle who became a bishop. The uncle sent him in 1491 to the University of Cracow. Through his uncle's influence, he secured a lifetime appointment as one of the canons of the cathedral chapter at Frauenburg (Frombork). In 1496 the chapter sent him to the University of Bologna to study canon law, but he was also able to study astronomy there, and his first recorded astronomical observation was made there in 1497. After returning home to Frauenburg in 1501, he received permission to return to Italy in order to study medicine at Padua. He received a doctorate in canon law from the University of Ferrara in 1503 and also was qualified to practice medicine before returning to spend the rest of his life at Frauenburg.

   Copernicus became widely known as an expert astronomer and made a number of important astronomical discoveries, though his major achievement was not in discovering new data but in rethinking the theoretical foundations of astronomy. His Italian education gave him the competence in Greek that allowed him to publish Latin translations of Greek books and to consult the Greek text of Ptolemy's major astronomical work, the Almagest, a work not yet available in Latin.

   Copernicus' later fame rests on his book De revolutionibus orbium coelestium / On the Revolutions of the Celestial Spheres (1543), but he had worked for much of his life seeking to discover a view of the universe that challenged the complicated and self-contradictory system of the Hellenistic astronomer Ptolemy, the universally acknowledged authority in astronomy. As early as 1513 he wrote a short work, Commentariolus / Little Commentary, that put forward many of the ideas elaborated in De revolutionibus. His new system made a rather simple suggestion—that if one reversed the positions that Ptolemy and nearly all subsequent astronomers assigned to the earth and the sun, putting the sun instead of the earth at the center, many of the troublesome complications of astronomy were resolved.

   Yet since his proposal would challenge many philosophical and religious ideas associated with the idea that the earth was the center of the universe, Copernicus hesitated to publish his new system. His pupil Georg Joachim Rheticus, who had published a summary of his ideas under the title Narratio prima / Preliminary Account, finally persuaded Copernicus to publish his major treatise. The work was dedicated to Pope Paul III, and publication was arranged by a Lutheran minister, Andreas Osiander, who added a preface presenting Copernicus' new theory not as literally true but as a hypothesis useful in simplifying astronomical calculations.

   Although his book attracted considerable attention, most astronomers rejected it not just because it flew in the face of traditional learning but also because its theories raised certain objections that Copernicus himself could not explain. In particular, Copernicus' continued adherence to the Ptolemaic belief that the orbits of the planets must be perfectly circular prevented his system from providing the greater accuracy in the calculation of orbits that he anticipated. Though well known to professional astronomers, his ideas were rejected by most of them. In the long run, the importance of De revolutionibus is that it defined the problems that astronomers of the next four or five generations —Tycho Brahe, Johannes Kepler, Galileo Galilei, and Isaac Newton—would resolve as they developed a new science of astronomy based on his heliocentric theory.