On January 6, 1497, Copernicus enrolled at the German College for the sum of nine grossetos: "...Dominus Nicolaus Kopperlingk de Thorn grossetos novem", we read in the Annales Clarissimae Nationis Germanorum.
The Italian and Bolognese astronomical environment at the end of the XVth century does therefore assume particular importance for the long sojourn of Copernicus. Naturally enough this has always been considered an important event and has attracted the attention of scholars who on the whole agree that, after the works of Marsilio Ficino, Pico della Mirandola and others of their humanist contemporaries, some sort of heliocentrism, even if more philosophical and theological than geometrical, was fairly widespread in Italian scholarly circles. They do not agree however in their assessments of the possible effects of this on Copernicus, mainly because he might well have come across similar ideas during his stay in Cracow as a result of the spread of Nicholas of Cusaís thought throughout central Europe (42).
It would of course be very helpful to have more news about Ferrara-born Domenico Maria Novara (1454-1504), who read Astronomy in Bologna from 1483 to 1504 and with whom Copernicus forged close ties during his stay in Bologna from 1496 to 1500 (43), but the records we have of him are so scanty his scientific personality remains largely unknown (44).
According to Kuhn (45) strong ties existed between Domenico Maria Novara and the Florentine neoplatonists who translated Proclus and other authors from his school. Novaraís criticism of the Ptolemaic system was grounded therefore in neoplatonic argumentation and, in particular, in the belief that a mechanism that was so cumbersome and complex could not effectively account for the order that was visible in nature.
Even if cosmological questions had not interested Copernicus, the criticisms nonetheless added to more technical difficulties that had accumulated in the system and that had been pointed up by studies on the reform of the calendar: the effective order of the planets, the existence of "trepidation", the variation in luminosity of the planets and especially of the Moon. Copernicus was not the only one aware of these problems; nor was he the only one searching for a solution. Others included the Ferrarese Celio Calcagnini (1479-1541) - author in 1541 of Quod Coelum stet et Terra moveatur, upholding the rotational movement of the Earth - Girolamo Fracastoro from Verona (c.1478-1553) - whose 1538 Homocentricorum sive de stellis liber unus tried to revive the homocentric spheres system of Eudoxus - and Giovan Battista Amico from Cosenza (1512-1538), an author who though brought up in the cultural climate of Padua must have had some influence on Copernicusís thought (46).
To understand the evolution of the astronomer from Torunís thought would be of great value for the history of human ideas but unfortunately there is practically no direct data on the genesis of the Copernican revolution. Accordingly, the possible significance of the various elements must remain a matter of conjecture. Different authors have emphasized the unresolved problems of the previous model, the traces of heliocentrism already present in the classics, and the contrast between the "philosophi" astronomers, tied to an Aristotelian universe, and the "mathematici" astronomers, who used the Ptolemaic model for calculating tables and ephemerides.
The spread of Copernicanism is a story as interesting as it is badly documented, in Bologna as in the rest of Europe. Copernicusís book is an extremely technical text that could only be used by specialists - though without necessarily agreeing with the basic idea, so that the use of Copernican calculation techniques or their teaching did not necessarily imply heliocentric convictions.
The whole question however went beyond just professional astronomical circles and Copernicusís ideas were supported or opposed by scholars with a variety of interests. Giordano Bruno (1548-1600) is a case in point. There was, moreover, no shortage of serious objections to the Copernican system, even from a modern point of view, which were only overcome when Aristotelian physics was replaced by Galilean.
Returning to Copernicusís stay in Bologna, the astronomer lived as a paying guest in the house of Novara - located probably in via San Giuseppe, halfway down via Galliera - rising rapidly from a position as student to one of assistant and "helper" in the observations. Besides the observation techniques Novara was especially expert in, Copernicus almost certainly absorbed some of his teacher-friendís ideas which led him to question authority, even that of the great Ptolemy. The Alexandrian astronomer was heavily criticized by Novara over a presumed shift in the axis of terrestial rotation which Novara himself had put forward to explain the differences in latitude of certain mediterranean cities measured at the time, compared to those reported by Ptolemy.
This attack of Novara on the absolute immobility of the Earth must have left a mark on Copernicus, spurring him on to study in more detail the Ptolemaic doctrines and the scientific studies of the ancient greeks, a large part of which had not yet been translated; he thus devoted himself to the study of the classics under the guidance of the local greek teacher, Antonio Urceo Codro (1446-1500), on whose account he translated some letters, later published in Cracow. It may well be that during these greek studies Copernicus translated the Arenarius of Archimedes , a work in which the idea of a heliocentric system of the world put forward by Aristarchus of Samos in the third century BC, is described.
In the meantime he carried on his astronomical studies with Novara whose fame as a good observer (47) is substantiated by Copernicus himself when, speaking in De revolutionibus orbium coelestium about the problem of the lunar parallax, he records the observations made in Bologna with Novara of a lunar occultation of Aldebaran on March 9, 1497 and of a conjunction of Saturn with the Moon on March 4, 1500 (48).
The problem of the lunar parallax can be seen as being of fundamental importance in Copernicusís rewriting of the ancientsí astronomy.
It is well known that the artifices used by Ptolemy to describe the irregularities of the movement of the Moon implied a huge variation in its distance from the Earth. At the quadratures (i.e. during the quarters of the Moon) this distance ought in fact to have been half that when the Moon was new or full. This fact would have implied a corresponding variation in the apparent diameter of the Earthís satellite, something which does not occur, as was well known to antiquity and which had been underlined by Regiomontanus (Johann Müller, 1436-1475) in a paper of his that came out in 1496 (49). It cannot be excluded then that both Copernicus and Novara were looking for pointers to resolve the problem, trying to obtain a direct measurement of the lunar parallax.
Evidence of Novaraís interest in the problem of lunar motion can be gleaned from his epigraph, which said of him "he who investigated the moving Moon and the motion of Febo [Sun]." (50)
These are strangely similar words to those used in 1509 by Lorenz Korvin, professor in Cracow and municipal chancellor at Torun, in his eulogy prefacing a translation from the Greek of lyric poetry by Teofilatto Simocatta, a byzantine historian of the VIIth century, which was Copernicusís first printed work and which ran "He who investigates the swift course of the Moon and the alternate motion of its brother [Sun] and the stars with the fugitives earths knows admirably how to discover the wonderful work of God and the hidden causes of things." (51)
It is well known that Copernicus solved the problem by reorganizing in a different manner the system Ptolemy had invented, in a sense anticipating in his method what he would later do for the planetary system.
It would perhaps be going too far to suggest that the Bolognese observations of 1497 were specifically designed to verify the Copernican theory of the Moon as laid out in De Revolutionibus or Commentariolus (a short manuscript bearing the first written report of Copernican ideas), where the theory is assigned its correct importance; the Bolognese observations do however show that the problem of the Moonís motion already preoccupied Copernicus at that time.
Copernicus stayed in Bologna for only four years; when his studies finished on September 6, 1500, he went to Rome on occasion of the jubilee year proclaimed by Pope Alexander VI . He spent three more years in Italy, studying Medicine in Padua and finally getting his doctorate in Canon Law at Ferrara in 1503. Then he went back to his uncle the bishop in Poland to attend to his canonry in Varnia, obtained on 20th October 1497, and his astronomical studies, taking with him the rich scientific and humanistic experience he had acquired in Italy.