Nicolaus Copernicus
He was born in Torun, Poland, and studied in the Jagiellonian University in Cracow. Then he went to Italy and studied law, astronomy, and medicine. He was appointed a canon of the Cathedral of Frauenburg (Frombork) in 1497 (while he was in Italy), thanks to his uncle and patron Watzenrode (bishop), and Copernicus later served as physician to this uncle.
Among Copernicus's writings, Commentariolus and De Revolutionibus Orbium Coelestium are the most important; the former was not published but circulated as handwritten copies, and the latter was posthumously published in 1543. The basic idea of heliocentricism was put forward in Commentariolus, and Copernicus's elaborated presentation of heliocentricism was made in De Revolutionibus.
Usually the phrase "Copernican Revolution" means a radical change of a theory or a world view; but ironically, this does not apply to Copernicus's own theory. Copernicus's heliocentricism shared many elements with older geocentric theories such as Ptolemy's, and Copernicus wished to convert the roles of the Sun and the Earth in order to save the Aristotelian ideal of uniform circular motion. Copernicus did not like Ptolemy's use of equant (imaginary center of a planetary motion which is not uniform).