   It is impossible to date when Copernicus first began to espouse the heliocentric theory. Had he done so during his lecture in Rome, such a radical theory would have occasioned comment, but there was none, so it is likely that he adopted this theory after 1500. Further, Corvinus, who helped him print his Latin translation in 1508–09, expressed admiration for his knowledge of astronomy, so that Copernicus’s concept may have still been traditional at this point. His first heliocentric writing was his Commentariolus. It was a small manuscript that was circulated but never printed. We do not know when he wrote this, but a professor in Cracow cataloged his books in 1514 and made reference to a “manuscript of six leaves expounding the theory of an author who asserts that the earth moves while the sun stands still” (Rosen, 1971, 343; MW 75). Thus, Copernicus probably adopted the heliocentric theory sometime between 1508 and 1514. Rosen (1971, 345) suggested that Copernicus’s “interest in determining planetary positions in 1512–1514 may reasonably be linked with his decisions to leave his uncle’s episcopal palace in 1510 and to build his own outdoor observatory in 1513.” In other words, it was the result of a period of intense concentration on cosmology that was facilitated by his leaving his uncle and the attendant focus on church politics and medicine.