The nature of Copernicus discoveries

It was not astronomical observations, even the most accurate ones, that were the basis of Copernicus astronomy, but contemplation of the harmony of the universe.

While analysing geocentric astronomy, Copernicus found that it describes the construction of the world with a fairly random set of hypotheses.

He showed great respect for the craft of the finest representatives of ancient astronomy, but at the same time he wrote about them in his dedicatory letter in De revolutionibus in a following way: ...their experience was just like some one taking from various places hands, feet, a head, and other pieces, very well depicted, it may be, but not for the representation of a single person; since these fragments would not belong to one another at all, a monster rather than a man would be put together from them (translated by Edward Rosen). Copernicus searched for the simplest solutions, which in an irresistibly logical and harmonious way would explain all the observed motions of planets.

Heliocentric system. Manuscript of 'De revolutionibus'

Eventually, he reached the conclusion that this condition is met by the system the centre of which is the Sun, whereas the planets revolve around it in the order, which is determined by the speed of their motions: from the fastest, Mercury, through Venus, Earth, Mars, Jupiter, to the slowest one, Saturn. In Copernicuss universe beyond the Solar System only stars could be found, which, because of Copernicuss assumption of Earths daily rotation around its own axis, could remain still. Thus, the most important discovery of Copernicus consisted in understanding that the world order was devised in the form of the heliocentric system, in which Earth is one of the planets, that is one of the centres of gravity, and the distant stars do not have to rotate around it at the dizzying speed of one rotation per 24 hours.

The rest was boiled down to such use of mathematics and observations as would grasp this order as precisely as possible, in order to determine the construction of planetary orbits, their size and position in space - a matter requiring a perfect knowledge of geometry and many hours spent under the open sky, as well as time consuming calculations, but still of secondary importance.

Further reading:

1. Dobrzycki, The Role of Observations in the Work of Copernicus, "Vistas in Astronomy", Vol. 17 (1975), 27–30.
2. Dobrzycki, Notes on Copernicuss Early Heliocentrism, "Journal for the History of Astronomy", Vol. 32 (2001), 223–5.
3. Gingerich, The Astronomy and Cosmology of Copernicus, "Highlights in Astronomy of the International Astronomical Union", ed. by G. Contopoulos, Vol. 3 (1974), 67–85.
4. Gingerich, Crisis versus Aesthetic in the Copernican Revolution, "Vistas in Astronomy", ed. by A. Beer and K. Strand, Vol. 17 (1975), 85–95.
5. Goddu, Reflections on the Origin of Copernicuss Cosmology, "Journal for the History of Astronomy", Vol. 37 (2006), 37–53.