III.

Return to Poland

From 1503 to 1510, Copernicus lived in his uncle's bishopric palace in Lidzbark Warminski, assisting in the administration of the diocese and in the conflict against the Teutonic Knights. There he published his first book, a Latin translation of letters on morals by a 7th-century Byzantine writer, Theophylactus of Simocatta. Sometime between 1507 and 1515, he completed a short astronomical treatise, De Hypothesibus Motuum Coelestium a se Constitutis Commentariolus (known as the Commentariolus), which was not published until the 19th century. In this work he laid down the principles of his new heliocentric astronomy.

After moving to Frauenberg in 1512, Copernicus took part in the Fifth Lateran Council's commission on calendar reform in 1515; wrote a treatise on money in 1517; and began his major work, De Revolutionibus Orbium Coelestium (On the Revolutions of the Celestial Spheres), which was finished by 1530 but was first published by a Lutheran printer in Nürnberg, Germany, just before Copernicus's death in 1543.