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Following the death of his father, a merchant of Torun, Poland, in 1484, Copernicus was brought up by his maternal uncle Lucas, the bishop of Ermeland. In 1491 he entered the University of Cracow where he became interested in astronomy. He went to Italy in 1496, studying law and medicine at the universities of Bologna and Padua and finally taking a doctorate in canon law at the University of Ferrara in 1503. By this time he had become, through a literal case of nepotism, a canon of Frauenburg, a post he was to hold until his death. In 1506 Copernicus returned home to serve his uncle as his doctor and secretary at Heinsberg castle. When his uncle died in 1512 Copernicus moved to Frauenburg to take up his modest duties as a canon.

Copernicus's pursuit of his interest in astronomy both brought him a distinguished reputation and led to a dissatisfaction with the prevailing system of astronomy. However his first statement of his revolutionary views, the Commentariolus (written between about 1510 and 1514) was circulated privately in manuscript form. The system Copernicus was rebelling against goes back to the Greece of Plato and received its fullest development in theAlmagest of Ptolemy in the second century ad. It assumed that the Earth, unmoving, was at the center of the universe around which not only the Moon but the Sun and the other known planets revolved with perfect uniform circular motion. However, in order to fit the complicated movements of the planets into such a simple scheme, all kinds of compromises had to be made and complications brought in. Hence the introduction of such concepts as epicycles, eccentrics, and equants into the basically simple system. The second weakness was its failure to predict at all accurately the movement of the planets. Thus a conjunction of the major planets in 1503 predicted by the almanacs of the day was as much as ten days out. Copernicus, unlike Tycho Brahe, seemed unworried about the second point and, in all his writings, emphasized the urgency of a return to uniform circular motion. How, he asked himself in the Commentariolus, could this be achieved? It is at this point that he came up with his revolutionary hypothesis, “All the spheres revolve about the Sun as their midpoint and therefore the Sun is the center of the universe.”

Copernicus then worked his system out in detail. His great workDe revolutionibus orbium coelestium (On the Revolution of the Celestial Spheres), although finished by the early 1530s, was to be published only in the month of his death in 1543. Why Copernicus withheld his masterpiece from the world is a matter for speculation. News of his system seems to have spread quite widely. The popes Leo X and Clement VII refer to it without any obvious hostility although Luther makes an abusive reference to it. The publication of De revolutionibus was due to a young professor of mathematics from Wittenberg, Rheticus. Having heard of Copernicus's system and wishing to study it at first hand he turned up in Frauenburg bearing the typical gifts of the humanist scholar, the first printed editions of Euclid and Ptolemy. But Copernicus was still reluctant to publish and would only agree to Rheticus writing a description of the new system, which appeared as Narratio prima (1539; First Narrative). Copernicus finally agreed, under strong pressure from Rheticus and his friends, to Rheticus's copying and publishing his manuscript. Rheticus went to Nuremberg intending to see the work through the press, but before its completion he had to leave to take up a new appointment at Leipzig. The task of seeing the work through the press was left with Andreas Osiander, a Nuremburg theologian who added to the work a famous and unauthorized preface asserting that the heliocentric hypothesis was not intended to be a true description of the universe but was merely a useful supposition. He was presumably trying to avoid any church opposition. It was finally published in March, 1543. It is recorded by a friend of Copernicus's that “he only saw his completed book at the last moment, on the day of his death.” The book did meet opposition from theologians who found that it conflicted with the Bible. The Aristotelians were opposed to it and to many it seemed simply absurd that the Earth could be flying through space. Even professional astronomers like Tycho found it unacceptable. A moving Earth ought to imply apparent movement in the fixed stars, but none could be observed. Acceptance of Copernicus's explanation – that the stars were too far away for parallax to be observed – would involve a radical change in the accepted size of the universe. Moreover, although the heliocentric theory explained the movements of the Moon and the planets in a much more elegant way than the Ptolemaic system, Copernicus's insistence on perfect circular orbits involved nearly as much complexity as was found in Ptolemy.

However, there was no real official opposition to De revolutionibus and the system outlined in it until it was placed on the index of those books banned by the Catholic Church in 1616 (from which it was not removed until 1835). But it did find acceptance with many humanist mathematicians and astronomers, so that by the end of the century the issue had switched from whether to accept Ptolemy or Copernicus, to how one should accept Copernicus – as a true description or a useful mathematical trick.