Prof. Fred L. Wilson
Rochester Institute of Technology
Science and Human Values
Copernicus
Chapter 15
Overview of Copernicus
To the Greek natural philosophy, the Renaissance thinkers brought a fresh outlook, for the old views no longer entirely satisfied. In 1543, the Polish astronomer Nicolaus Copernicus published a book that went so far as to reject a basic axiom of astronomy: he proposed that the sun, not the earth, be considered the center of the universe. (He retained the notion of circular orbits for the earth and other planets, however.) This new axiom allowed a much simpler explanation of the observed motions of heavenly bodies. Yet the Copernican axiom of a moving earth was far less "self-evident" than the Greek axiom of a motionless earth, and so it is not surprising that it took more than half a century for the Copernican theory to be accepted.
In a sense, the Copernican system itself was not a crucial change. Copernicus had merely switched axioms; and Aristarchus of Samos had already anticipated this switch to the sun as the center 2,000 years earlier. I do not mean to say that the changing of an axiom is a minor matter. When mathematicians of the nineteenth century challenged Euclid's axioms and developed "non-Euclidean geometries" based on other assumptions, they influenced thought on many matters in a most profound way: today the very history and form of the universe are thought to conform to a non-Euclidean geometry rather than the "commonsense" geometry of Euclid. But the revolution initiated by Copernicus entailed not just a shift in axioms but eventually involved a whole new approach to nature. This revolution was carried through in the person of the Italian Galileo Galilei toward the end of the sixteenth century.
Organism did not disappear with Copernicus. With the thinking of an age so permeated by the concept of organism, science could hardly be expected to strike out on a new path overnight. Late medieval science was characterized by trends of thought existing side by side - one affirming without reservation the concept of organism, the other trying to find new ways, while continually falling back unawares on the heritage of organismic concepts. The most colorful representative of the former trend was Paracelsus, who always went beyond generalities and carried his organismic tenets into the field of practical applications. A firm believer in the dependence of anatomy on astronomy, Paracelsus never stopped urging his fellow physicians to keep astronomy in mind when diagnosing a sickness.
Copernicus' Life
Copernicus was the son of a well-to-do merchant, and, after his father's early death in 1483, was brought up by his uncle, a prince-bishop, so he had the advantage of being able to get a first-class education. He studied mathematics and painting at Cracow, then and for many years afterward the intellectual center of Poland. In 1496 he traveled to Italy for a decade's stay, during which time he studied medicine and canon law, and after reading the works of Regiomontanus, interested himself in astronomy.
In 1500 this interest was intensified when he attended a conference in Rome that dealt with calendar reform, understood to be necessary since the time of Roger Bacon two centuries before, but not to come for another seventy years.
The intellectual ferment in Italy was not above questioning established ways. The system of the universe as propounded by Hipparchus and Ptolemy, in which all heavenly bodies were considered rotating about the earth, was almost indecently complex and despite all the careful mathematics involved was not very useful for predicting the positions of the planets over long periods. The Alfonsine Tables, of Alfonso X, the best the previous centuries had produced, were already far off the mark, and the corrections of Regiomontanus were only of temporary value.
It occurred to Copernicus as early as 1507, that tables of planetary positions could be calculated more easily if it were assumed that the sun, rather than the earth, were the center of the universe. This would mean that the earth itself, along with the other planets, would have to be considered as moving through space and revolving about the sun. This was not a new idea. Among the ancients, Aristarchus had suggested the notion, and not many years before the time of Copernicus, Nicholas of Cusa had made a similar suggestion.
Copernicus was to do more than suggest, however. Beginning in 1512, he set about working out the system in full mathematical detail in order to demonstrate how planetary positions could be calculated on this new basis. In doing this, he made little use of his own observations, for astronomical; observation was not his forte, apparently. He is supposed never to have seen the planet Mercury (which is, however, the most difficult of the planets to observe because of its proximity to the Sun.) Still, his observations were good enough to enable him to determine the length of the year to within twenty-eight seconds.
As it turned out, the Copernican system explained some of the puzzling motions of the planets rather neatly. The orbits of Mercury and Venus, according to the new system, would naturally never take those planets farther than a certain distance from the sun, as viewed from the earth, because the orbits of those two planets lay closer to the sun than did the orbits of the earth. On the other hand, since the earth would have to be considered as traveling in a smaller orbit than those of Mars, Jupiter, and Saturn, it would periodically overtake those planets and cause them to appear to be moving backward in the sky.
Both the limited motion of Mercury and Venus and the backward ("retrograde") motions of Mars, Jupiter, and Saturn had been thorns in the side of the Ptolemaic theory and vast complications had been introduced to account for them. Now they were easily and simply explained. Furthermore, the phenomenon of the precession of the equinoxes, discovered by Hipparcus, could be explained not by a twisting of the entire celestial sphere, but by a wobbling of the earth as it rotated on its axis. As for the celestial sphere of the stars, Copernicus held it to be a vast distance from the earth, at least a thousand times as distant as the sun, so that the positions of the stars did not reflect the motion of the earth. The fact that they did not was used as an argument against Copernicus, an argument that was not fully laid to rest until the time of Bessel, three centuries later.
So much was explained so well by the new Copernican system that it grew tempting to consider that system as more than a mere device to calculate planetary positions. Perhaps it described the actual situation, moving earth and all. Copernicus, however, still kept the notion of perfectly circular orbits and had to retain thirty-four of the epicycles and eccentrics associated with the older theory. This was not corrected until the time of Kepler a half century later.
Copernicus described his system in a book, but for years he hesitated to publish it, believing that any suggestion that the earth moved would be considered heretical and might get him into trouble. This view was a natural and perhaps a prudent one in the light of the later troubles of Galileo and Bruno.
In 1505 Copernicus returned to Poland where he served as canon, under his uncle, at the cathedral at Frombork (Frauenberg, in German), although he never became a priest. He never married, just the same. He also served as his uncle's doctor and fulfilled a variety of administrative duties, especially after his uncle's death. He was involved in diplomatic negotiations between the Poles and the Teutonic Knights of Prussia, for instance. Then, too, in working on currency reform, he came up with the notion that the appearance of debased currency drives good coins into hiding -- something later called "Greshams' law" after an economist who was a younger contemporary of Copernicus.
Meanwhile, by 1530, he had prepared a summary of his notions in manuscript and this circulated among Europe's scholars, creating considerable interest and enthusiasm. Finally, at the urging of the mathematician Rheticus, Copernicus permitted publication of his entire book, carefully dedicating it to Pope Paul III. Rheticus volunteered to oversee its publication.
Unfortunately, Rheticus had to leave town since he was involved in some rather uncomfortable doctrinal disputes and since he had a chance to accept a better position at Leipzig. He left a Lutheran minister, Andreas Osiander, in charge. Luther had expressed himself firmly against the Copernican theory, and Osiander played it safe by adding an unauthorized preface to the effect that the Copernican theory was not advanced as a description of the actual facts but openly as a device to facilitate computation of planetary tables. This weakened the book and for many years compromised Copernicus' reputation, for it was long thought that he was responsible for the preface. It wasn't until 1609 that Kepler discovered and published the truth.
The book was published in 1543 and the story has long persisted that the first copy reached Copernicus as he lay on his deathbed, suffering from a stroke. A copy of the book, dated four weeks before his death has recently come to light and it may be that Copernicus had a chance to see it. The book began to win converts at once, Reinhold using it within a few years to publish new tables of planetary motion.
Nevertheless it was not a financial success. It was overpriced and was allowed to go out of print. A second edition was not printed until 1566 in Basel, Switzerland and a third not until 1617 in Amsterdam.
With Copernicus began the Scientific Revolution, which was to dethrone Greek science and set man on a new and far more fruitful path. It reached a climax and fulfillment with Newton a century and a half later. Yet it was not until 1835 that Copernicus' book was removed from the list of those banned by the Catholic Church.
In 1807 Napoleon's conquering career had brought him to Poland. He visited the house in which Copernicus was born and expressed his surprise that no statue had been raised in his honor. In 1839 this omission was rectified, but when the statue to Copernicus was unveiled in Warsaw, no Catholic priest would officiate on the occasion.
The Scientific Revolution
Copernicus did open the door to the scientific revolution. This we will develop in further sessions. The following graphic summarizes the enormous changes made in science as related to astronomy. Other changes occurred as well and much is owed to Copernicus for showing that what was always believed to be true was a shabby imitation of a much better view.
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Last modified April 9, 1999. This site maintained by Physics Teacher.Org