According to Aristotle’s teaching, the planets revolve around the earth, which is the center of the universe, on immutable, material but invisible, nested concentric spheres. If the distances to Earth were always the same, there should actually be no fluctuations in the apparent brightness of the planets – except for the moon – which is the case. Claudius Ptolemy apparently solved this problem in the second century with his epicycle theory, a system of circles that move in a circle: the planets move on a small circular path (epicycle), which in turn on a large circular path (deferent) around a planet fixed center moves.
Around 1510 Copernicus wrote a manuscript of just a few pages, »De hypothesibus motuum coelestium a se constitutis commentariolus«, which he sent confidentially to some of his acquaintances, who in turn forwarded them. Working out the details of this theory, including the determination of radii and orbital periods, was to occupy him for the next few decades. Here are his key insights:
- The planets revolve around the sun – as if it were in the middle; hence the center of the universe is near the sun. So the center of the earth is not the center of the universe.
- The earth performs three circular motions: it revolves around the sun once a year, it rotates once a day on its own axis (“creating the heavenly fireworks of sunrise and sunset and all the starry dances”), and the earth’s axis also rotates during of a year in such a way that the position of the axis remains almost unchanged (precession).
- The order of the planets is: Mercury, Venus, Earth with Moon, Mars, Jupiter, Saturn. The apparent alternation of forward and backward motions of the planets is a geometric effect resulting from the Earth’s position during Earth’s orbit.
- The distance of the earth from the sun is insignificant compared with the distance to the immobile sphere of the fixed stars; therefore one will not notice any differences (parallax) in the position of the stars during the course of the year.
- God and his angels soar beyond the sphere of the fixed stars.
Even if the title page of the »Commentariolus« contained no information about who wrote the paper, it finally became known even in Rome that there lived a distinguished astronomer in distant Warmia. In 1514 he received an invitation to the Church’s Fifth Lateran Council, at which the problem of calendar reform was finally to be tackled. Copernicus did not attend the council, but gave a written opinion; however, his letter never seemed to have reached Rome.
Unrest in Warmia
The successors of his uncle Lucas Watzenrode, who died in 1512, also relied on Copernicus’ administrative skills. When the 21-year-old Albrecht von Hohenzollern was elected Grand Master of the Teutonic Knights in 1511, a particularly troubled time began for Warmia. In 1520 Frauenburg was even completely destroyed. After constant military conflicts, peace finally came in 1525 when Albrecht dissolved the religious order and took the oath of fealty to the Catholic Polish King Sigismund. But as soon as Albrecht von Sigismund was installed as Duke of Prussia, he switched to Protestantism.
Part of the peace treaty was also a reorganization of the coin system. Copernicus had already pointed out the danger of imminent inflation in 1517: for years he had observed how the religious order and individual cities began to issue new coins with the same face value but constantly decreasing material value, which led goldsmiths to melt down old coins and what they contained Silver to be used elsewhere. He demanded that in future there should only be one issuing office for coins with a specified silver-copper alloy.
After the conclusion of peace, Copernicus was finally able to devote himself to working out the theses of his »Commentariolus«. Despite being asked to finally do so by various parties, including the Roman Curia Cardinal Nikolaus von Schönberg, who even offered to bear the printing costs, Copernicus hesitated – possibly for fear of making a fool of himself with his revolutionary theory. This only changed when in May 1539 Georg Joachim Rheticus, a 25-year-old mathematician and astronomer from the University of Wittenberg and confidant of Philipp Melanchthon, came to Frauenburg to ask the Nuremberg publisher Johann Schöner and the printer Johannes Petreius to to publish the work.