He became an astronomer, who developed a heliocentric (Sun-centered) theory of the solar system. He was also Domherr of Frauenburg , and he administered medicine to the people of Prussia. His major theory was published in the book De revolutionibus orbium coelestium ("On the Revolutions of the Heavenly Spheres") in the year of his death 1543, even though he had arrived at it several decades earlier. This book marks the beginning of the shift from a geocentric? (and anthropocentric?) universe. Copernicus held that the Earth is another planet revolving around the fixed sun once a year, and turning on its axis once a day. The theory, unfortunately, still had some serious defects, like circular as opposed to elliptical orbits and epicycle?s, that made it no more precise in predicting ephemerides than the then current tables based on Ptolemy's model. But it had a large influence on scientists such as Galileo and Kepler, who adopted, championed and, in Kepler's case, improved the model. The book was put on the [Index of Forbidden Books]? in 1616 by the Roman Catholic Church. Galileo's observation of the phases of Venus produced the first observational evidence for Copernicus' theory.
Legend says that a printed copy of De revolutionibus was put in Copernicus's hands shortly before his death so that he could say goodbye to his opus vitae. He awoke from his stroke induced coma, looked at his book, and died peacefully.
Erasmus Reinhold helped spread the Copernican Theory throughout the empire.
Outside link to a map of Prussia, where Copernicus was born and died . The city of Thorn is on the bottom left of the Prussia map at the Vistula River[[1]]
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