Nicolaus Copernicus

Polish name: Mikołaj Kopernik. Polish astronomer and mathematician who, as a student, studied canon law, mathematics, and medicine at Cracow, Bologna, Rome, Padua, and Ferrara. Copernicus became interested in astronomy and published an early description of his "heliocentric" model of the solar system in Commentariolus (1512). In this model, the sun Eric Weisstein's World of Astronomy was actually not exactly the center of the solar system, but was slightly offset from the center using a device invented by Ptolemy known as the equant point. The idea that the Sun Eric Weisstein's World of Astronomy was the center of the solar system was not new (similar theories had been proposed by Aristarchus and Nicholas of Cusa), but Copernicus also worked out his system in full mathematical detail. Even though the mathematics in his description was not any simpler than Ptolemy's, it required fewer basic assumptions. By postulating only the rotation of the Earth, Eric Weisstein's World of Astronomy revolution about the sun, Eric Weisstein's World of Astronomy and tilt of Earth's Eric Weisstein's World of Astronomy rotational axis, Copernicus could explain the observed motion of the heavens. However, because Copernicus retained circular orbits, his system required the inclusion of epicycles. Unfortunately, out of fear that his ideas might get him into trouble with the church, Copernicus delayed publication of them.

In 1539, Copernicus took on Rheticus as a student and handed over his manuscript to him to write a popularization of the heliocentric theory, published as Narratio Prima in 1540. Shortly before his death, Rheticus convinced Copernicus to allow publication of his original manuscript, and De Revolutionibus Orbium Coelestium was published in 1543. Copernicus proposed his theory as a true description, not just a theory to save appearances. Unlike Buridan and Oresme, he did not think that any theory which saved appearances was valid, instead believing that there could only be a single true theory. When the work was published, however, Andreas Osiander added an unauthorized preface stating that the contents was merely a device to simplify calculations.

Copernicus adapted physics to the demands of astronomy, believing that the principles of Ptolemy's system were incorrect, not the math or observations. He was the first person in history to create a complete and general system, combining mathematics, physics, and cosmology. (Ptolemy, for instance, had treated each planet separately.) Copernicus's system was taught in some universities in the 1500s but had not permeated the academic world until approximately 1600. Some people, among whom John Donne and William Shakespeare were the most influential, feared Copernicus's theory, feeling that it destroyed hierarchal natural order which would in turn destroy social order and bring about chaos. Indeed, some people (such as Bruno), used Copernicus's theory to justify radical theological views.

Before Copernicus formulated his theory of the solar system, astronomy in Europe had stagnated. After the Almagest had been translated into Latin, European astronomers such as the Austrian mathematician Georg von Peurbach and the German astronomer Regiomontanus proposed no new theories, attempting instead to refine the flawed system already laid out by Ptolemy. The astronomy textbook used for teaching was still The Sphere, the same book that had been in use since the 1200s. Rather than formulating new theories, astronomers had busied themselves in "saving appearances," which consisted of trying to patch it up Ptolemy's cumbersome and inaccurate model. Copernicus, however, wiped the slate clean in a single broad stroke, and proposed a fundamentally different model in which the planets all circled the Sun Eric Weisstein's World of Astronomy in De Revolutionibus Orbium Coelestium. While radically different from Ptolemy's model, Copernicus's heliocentric theory was hardly an original idea.