Nicolaus Copernicus, Polish Mikołaj Kopernik, born 1473. Between 1491 and about 1494 Copernicus studied liberal arts including astronomy and astrology at the University of Cracow. Polish astronomer who proposed that the planets have the Sun as the fixed point to which their motions are to be referred; that Earth is a planet which, besides orbiting the Sun annually, also turns once daily on its own axis; and that very slow, long-term changes in the direction of this axis account for the precession of the equinoxes. Copernicus’s theory had important consequences for later thinkers of the scientific revolution, including such major figures as Galileo, Kepler, Descartes, and Newton. Copernicus probably hit upon his main idea sometime between 1508 and 1514. Only 27 recorded observations are known for Copernicus’s entire life thoug he undoubtedly made more than that, most of them concerning eclipses, alignments, and conjunctions of planets and stars. In May of 1543, mathematician and scholar Georg Joachim Rheticus presented Copernicus with a copy of a newly published De revolutionibus orbium coelestium. Suffering the aftermath of a recent stroke, Copernicus was said to have been clutching the book when he died in his bed on May 24, 1543 in Frombork, Poland.