Nicolaus Copernicus combined astronomical research with duties as a cathedral canon in Warmia. His ecclesiastical position provided income while requiring administrative work, medical service, and involvement in local politics. He served his uncle, Bishop Lucas Watzenrode, as secretary and physician before settling at Frombork. Management of chapter estates and disputes occupied much of his time; during war with the Teutonic Knights, he helped organize the defense of Olsztyn. He also wrote proposals for monetary reform, arguing against debasement of currency.

Around 1510–1514 he circulated the Commentariolus, a short manuscript proposing that Earth rotated daily and traveled annually around the Sun. The arrangement offered a connected explanation of planetary order and apparent backward motion. Copernicus was concerned with the mathematical consistency of earlier astronomy, particularly devices that did not preserve uniform circular movement. His model retained circles and subsidiary circles; it was not the later system of elliptical orbits developed by Kepler.

Over decades he refined calculations, compared astronomical traditions, and prepared On the Revolutions of the Heavenly Spheres. In 1539 the mathematician Georg Joachim Rheticus came to study with him. Rheticus published an introductory account and helped persuade him to print the larger work. Published at Nuremberg in 1543 and dedicated to Pope Paul III, the book presented a detailed mathematical astronomy organized around Earth's motion. Andreas Osiander added an unsigned introductory statement treating the system as a calculating hypothesis; that statement did not accurately express Copernicus's own claim about the world's arrangement.

Copernicus died in 1543, traditionally said to have received the printed book shortly before death. Reception was gradual: some readers used his calculations without accepting a moving Earth, while others developed the physical implications of his theory. His work later became central to controversies involving Galileo and was placed under restrictions by the Catholic Church in 1616, long after his death. The astronomical transformation also drew on earlier Greek and Islamic mathematical work, and historians debate particular lines of transmission. His achievement was to offer a coherent alternative to geocentric planetary organization, initiating changes that later observations and theories substantially revised.