Nicolaus Copernicus

Copernicus was born in 1473 in Toruń, in Royal Prussia, a region that had come under the Polish crown after the Thirteen Years' War. His father was a copper merchant from Kraków; his mother, Barbara Watzenrode, came from a wealthy merchant family in Toruń. His parents were German-speaking; he used Latin as his written language.

After his father's death around 1483, his uncle Lucas Watzenrode, bishop of Warmia from 1489, took charge of his upbringing and career. Copernicus studied in Kraków, Bologna, Padua and Ferrara, where he obtained a doctorate in canon law in 1503. From 1497 he was a canon of the Warmia cathedral chapter, which gave him a steady income.

In the Commentariolus (before 1514) and in De revolutionibus orbium coelestium (1543) Copernicus worked out a model in which the Sun stands roughly at the centre, the Earth rotates daily on its axis and, as one of the planets, orbits the Sun once a year. Only the Moon continues to orbit the Earth. The model still used circular orbits and epicycles.

The idea of a moving Earth was not new: the Greek astronomer Aristarchus of Samos had proposed a heliocentric model in the third century BCE. Copernicus also used mathematical techniques developed earlier by astronomers of the Islamic world, such as Nasir al-Din al-Tusi and Ibn al-Shatir. Whether he knew their work is a subject of research.

Besides astronomy, Copernicus worked as a canon, physician and administrator for the Warmia chapter. Around 1519–1521 he stayed in Olsztyn, which he helped defend against the Teutonic Order. He also wrote on monetary matters and formulated the principle that bad money drives out good, later known as Gresham's law.

Around 1500 astronomy was shaped by Ptolemy's Almagest and by Aristotle's cosmology, with a stationary Earth at the centre. Humanism stimulated new interest in ancient sources, and printing made texts more widely available. Astronomical calculations served calendars, navigation and astrology.

Royal Prussia was a multilingual region with self-confident cities, the Polish crown and the nearby Teutonic Order. The Reformation spread from 1517; Protestant and Catholic theologians alike had objections to a moving Earth, partly on the basis of biblical passages. According to the preface of his main work, Copernicus hesitated for a long time to publish for fear of criticism.

De revolutionibus appeared in 1543 from the printer Johannes Petreius in Nuremberg. Rheticus had made the model accessible in 1540 with the Narratio prima. The book contained an anonymous preface, not written by Copernicus, by the Lutheran theologian Andreas Osiander, which presented the hypotheses as a calculating aid that need not be true or even probable.

The model explained the apparent loops in planetary paths as a consequence of the Earth's motion and gave the planets a fixed order. In accuracy it was not clearly better than Ptolemy's system. According to historians' estimates, sixty years after publication only about fifteen astronomers in Europe openly supported the model.

Copernicus died on 24 May 1543 in Frombork, after a stroke and paralysis at the end of 1542. He was buried in the cathedral. In 2005 bones were found beneath the cathedral floor which, according to DNA analysis, including hairs from a book he owned, belonged to him; a second funeral in the same cathedral followed in 2010.

The heliocentric model was generally accepted only in the seventeenth century, after the work of Kepler and Galileo and Newton's mechanics (1687). The Congregation of the Index suspended De revolutionibus in 1616 pending correction; the restrictions disappeared in the nineteenth century. His nationality has been a matter of debate; according to many historians, modern national categories fit Royal Prussia around 1500 poorly.