COPERNICUS, NICOLAUS (1473–1543), Polish cleric and astronomer, was born Mikołaj Kopernik in Torún, Poland, on February 19, 1473. He was raised in the comfortable circumstances of a wealthy burgher family and was educated at the cathedral school. Upon the death of his father in 1583, Copernicus and his younger brother Andreas were taken under the guardianship of their maternal uncle, Canon Lucas Watzenrode, who had been trained in the cosmopolitan humanist atmosphere of Bologna and later was made prince bishop of the Diocese of Warmia. Copernicus matriculated in the Collegium Maius of the renowned Jagiellonian University of Kraków, which at that time was strong in mathematics and had an endowed chair of astronomy dating from 1410. Copernicus's study of the theories of such luminaries as Ptolemy, Euclid, Sacrobosco, and Regiomontanus was complemented by his own observation in Kraków of the comets of 1491 and 1492 and of four lunar...