Nicolai Copernici Torinensis De revolutionibus orbium coelestium, Libri VI (
On the Revolutions of the Heavenly Spheres by Nicolaus Copernicus of Torin 6 Books), first printed in 1543 in
Nuremberg, is the seminal work on
heliocentric theory and the masterpiece of astronomer
Nicolaus Copernicus (1473–1543). The book offered an alternative model of the universe to the
Ptolemy's
geocentric system that had been widely accepted since ancient times.
Copernicus initially outlined his system in a short, untitled, anonymous manuscript that he distributed to several friends, referred to as the Commentariolus. A physician's library list dating to 1514 includes a manuscript whose description matches the Commentariolus, so Copernicus must have begun work on his new system by that time. However, most historians believe that he wrote the Commentariolus after his return from Italy, and possibly only after 1510. At this time, Copernicus anticipated that he could reconcile the motion of the Earth to the perceived motions of the planets quite easily, with fewer motions than were necessary for the Alfonsine Tables, the version of Ptolemaic astronomy popular at the time.
Observations of Mercury by Bernhard Walther (1430–1504) of Nuremberg, a pupil of Regiomontanus, were made available to Nicolaus Copernicus by Johannes Schöner, 45 observations in total, 14 of them with longitude and latitude. Copernicus used three of them in De revolutionibus, giving only longitudes, and erroneously attributing them to Schöner. Copernicus' values differed slightly from the ones published by Schöner in 1544 in Observationes XXX annorum a I. Regiomontano et B. Walthero Norimbergae habitae, [4°, Norimb. 1544].
Remarkably, a manuscript of De revolutionibus in Copernicus' own hand has survived. After Copernicus' death, it was given to Rheticus, who for the publication had only been given a copy without annotations. Via Heidelberg, it ended up in Prague, where it was rediscovered and studied in the 19th century. Close examination of the manuscript, including the different types of paper used, helped scholars to construct an approximate timetable for its composition. Apparently, Copernicus began by making a few astronomical observations to provide new data to perfect his models. He may have begun writing the book while still engaged in observations. By the 1530s a substantial part of the book was completed, but Copernicus hesitated to publish.
