Nicolaus Copernicus 1473–1543
(Also Kopernik) Polish astronomer and mathematician.
Copernicus is one of the extraordinary thinkers credited with inaugurating the Scientific Revolution in the sixteenth century with the publication of his De revolutionibus orbitum coelestium (On the Revolutions of the Heavenly Bodies, 1543). The revolution in science represents one of the greatest developments in the Western intellectual tradition. Thinkers such as Copernicus, the French philosopher Rene Descartes (1596-1650) and the British mathematician Sir Isaac Newton (1642-1727) departed radically from classical thought and from the ecclesiastical institutions of the Middle Ages. These thinkers brought about a change in the way people think and perceive both themselves and their place in the universe.
Copernicus was born into a well-to-do family in 1473. Copernicus's father, a copper merchant, died when Copernicus was ten, and Copernicus was taken in by an uncle. In 1491, Copernicus entered the University of Krakow where he studied mathematics and painting. In 1496, he went to Italy for ten years where he studied medicine at Padua and obtained a doctor's degree in canon law at Ferrara. In 1500, in the midst of his studies, Copernicus experienced two events that helped to shape the rest of his life: he attended a conference in Rome dealing with calendar reform and in November of that year witnessed a lunar eclipse. Copernicus continued his medical and legal studies, but also pursued his interest in astronomy, being exposed to the Pythagorean doctrines of cosmology taught in Italy. He developed a dissatisfaction with the Ptolemaic system and conceived the idea of a solar system with the sun at the center. In 1505, Copernicus returned to his native Poland, where he worked as physician to his uncle in his uncle's palace in Heilsberg. In 1512, when Copernicus's uncle died, Copernicus moved to Frauenberg where he belonged to the chapter or regular staff of the cathedral of Frauenberg. While serving in this capacity, Copernicus also developed a system of reform for the currency of the Prussian provinces of Poland (presented as De monetae cudendae ratione, 1526, and published in 1816) and began to make astronomical observations to test his belief in a heliocentric world system.
Copernicus was reluctant to make his ideas public because of their controversial nature. He did allow a summary of the Commentariolus (1530) to circulate among scholars. Johann Albrecht Widmanstadt presented Copernicus' views in lectures at Rome with the current pope, Pope Clement VII, expressing no disapproval. Cardinal Schönberg made a formal request for publication of Copernicus's views. Copernicus published the treatise On the Revolutions of the Heavenly Bodies in 1540. That same year, George Joachim Rheticus, a follower of Copernicus, published another brief account of Copernicus' views in his Narratio prima. The task of overseeing the publication of Copernicus's book was undertaken by a Lutheran minister named Andreas Osiander. Osiander seems to have felt obliged to present Copernicus's material in a way that would not offend Church officials (Martin Luther, the founder of Lutheranism, firmly opposed Copernicus's new theory). Osiander wrote and appended a preface to On the Revolutions of the Heavenly Bodies stating that the heliocentric theory was being presented as a concept to allow for better calculations of planetary positions. The unsigned preface gave the impression that Copernicus himself was undercutting his own theory. In 1542, Copernicus suffered a stroke and paralysis, and continued to decline until his death on May 24, 1543. Tradition relates that the first copy of Copernicus's book On the Revolutions of the Heavenly Bodies reached him on his death-bed, but in face he may never have seen his most important work published. In 1609 German astronomer Johannes Kepler (1571-1630) discovered that Osiander was the author of the preface to the first edition of Copernicus's On the Revolutions of the Heavenly Bodies.
On the Revolution of the Heavenly Bodies sets forth Copernicus's heliocentric theory of the solar system, with the sun as the center of a number of plaentary orbits including that of the Earth. Long before Copernicus, Aristarchus of Samos, a Greek astronomer living around 270 BC, had proposed that the sun was the center of things, but his theory was displaced by the teachings of Claudius Ptolemy (c.90-168 AD). Ptolemy proposed that the Earth was the center of the universe. In this system, all the planets, including the Sun and Moon (which were classified as planets) were attached to concentric spheres surrounding and rotating around the Earth. Their motion was governed by the Prime Mover or Just Cause, God. Motions of the planets that presented problems for this geocentric and spherical model were accounted for by means of epicycles (or cycles within cycles). Ptolemy's model of the universe remained dominant for over a thousand years. By Copernicus's time, the tables of planetary positions had become very complex but still did not offer accurate predictions of the positions of the planets over long periods of time. Copernicus realized that tables of planetary positions could be calculated more accurately by working from the assumption that the Sun, not the Earth, was the center of the world system and that the planets, including the Earth, moved around the sun. Copernicus was not an especially good astronomical observer. It is said that he never saw the planet Mercury, and he made an incorrect assumption about planetary orbits, believing that they were perfectly circular. Because of this, he found it necessary to use Ptolemy's cumbersome concept of epicycles (smaller orbits centered on the larger ones) to reduce the discrepancy between his predicted orbits and those he observed. It wasn't until Johannes Kepler that the elliptical nature of planetary orbits was understood. According to critic Harold P. Nebelsick, Copernicus's system was able to describe the "main movements of the planets with greater simplicity and harmony" than the Ptolemaic system could, and it was able to provide "a more accurate measurement of the distance of planetary orbits" from one orbit to another. The heliocentric model developed by Copernicus could explain the astronomical phenomenon known as retrograde ("backwards") motion better than Ptolemy's geocentric model. The fact that most of the planets appear to change direction periodically is more readily explained by the fact that their orbits are outside that of the Earth. The heliocentric model also explained the absence of such "backward" motion in the planet Venus, whose orbit is inside that of the Earth and therefore smaller.
The earliest reaction to On the Revolution of the Heavenly Bodies was subdued. Only a limited number of books were printed. Books—and in particular scientific texts with numerous illustrations—were expensive and consequently had limited circulation. The book did achieve a number of converts, but only a few highly advanced mathematicians and astronomers could fully understand it. Copernicus himself dedicated the book to mathematicians and did not seem to think that his findings would appeal to a general readership. A later generation of astronomers building on Copernican theories, including Tycho Brahe (1546-1601) and Johannes Kepler, continued to demonstrate that humankind was still learning about what had previously been thought to be a "fixed firmamant" of stars and planets, and Copernicus has grown in regard as a significant and revolutionary thinker for his times.