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Due to their uncle the Bishop’s influence, Copernicus and his brother had received appointments as canons of Warmia, positions involving both Church and civil authority. Nevertheless, the Chapter there was pleased to extend Copernicus’s leave of absence for educational purposes when he announced his intention to study medicine. Doctors were in short supply. So Copernicus set off again in 1501, this time for the University of Padua with its famed faculty of medicine. There he did indeed expend much effort studying medicine, though, mysteriously, the degree he eventually received was a Doctorate of Canon Law from the University of Ferrara. The explanation for the change of venue may be that he didn’t know anyone at Ferrara and hence could avoid the expense of the expected celebration party.
Copernicus returned to Poland in 1503 and – surprisingly, after such a cosmopolitan start – never left again. He began to build a distinguished reputation as a doctor, reportedly saving many lives later during a severe epidemic in 1519. Reading his notes, some of which arguably represent the best of medical practice at the time, leads one to wonder how this happened.
From 1503 until 1512, Copernicus, now in his thirties, lived at Lidzbark Castle, the seat of his uncle the Bishop of Warmia. He served as his uncle’s secretary and personal physician and became a force in the politics of Warmia, putting to use the legal education he had received at Bologna. He also found time for astronomical observations and kept painstaking records of them. About 1507, while still a member of the court at Lidzbark, he wrote a book in which he claimed that the Ptolemaic model was wrong. The book was short, about 20 handwritten pages. In that form (it was not printed) it circulated at first anonymously and with an unrecorded title among Copernicus’s scientific acquaintances. The later title was Nicolai Copernici de Hypothesibus Motuum Caelestium a se Constituis Commentariolus, usually shortened to Commentariolus (Commentary).
Sun-centred astronomy as Copernicus first proposed it in Commentariolus didn’t by any means solve all the problems still nagging Ptolemaic astronomy. Trying to eliminate the equant, which he found particularly offensive, and keeping the orbits circular, he was forced to use epicycles to account for the movement of the planets. There is little mathematical reasoning in Commentariolus. It is hardly more than a sketch. Nevertheless, the leap that Copernicus made was extraordinary. He claimed that by putting the Sun in the centre it would be possible to explain the heavens more simply and logically than Ptolemaic astronomy had done.
In Commentariolus Copernicus still visualized the universe in terms of spheres. The Sun rather than the Earth is at the centre of his arrangement, and there is a sphere representing the level (from the Sun) at which the Earth moves, encasing the Sun and the spheres of Mercury and Venus. The small sphere in which the Moon moves is the only sphere that has the Earth as its centre.
Copernicus proposed seven ‘assumptions’:
All celestial spheres do not have only one common centre.
The centre of the Earth is not the centre of the universe, but the centre of the Earth is the centre of gravity and of the Moon’s sphere.
All spheres (except that of the Moon) revolve around the Sun, as though the centre were the Sun, so the centre of the universe is near the Sun.
The firmament of stars is extremely far away. The distance from the Earth to the Sun is insignificant when compared with the distance from the Earth to the firmament.
What we see as motions in the firmament of stars are not its motions, but those of the Earth. The Earth with its adjacent elements, air and water, rotates daily around its poles while the firmament remains motionless.
What we see as motions of the Sun are not its motions, but the motion of the Earth and of the sphere with which we revolve around the Sun in the same manner the other planets revolve in their spheres.
What appears to us as retrograde and forward movement of the planets (the backward and forward motion) is not their motion, but that of the Earth. The Earth’s motion alone is sufficient to explain many different phenomena in the heavens.
Copernicus went on to write: ‘The highest is the sphere of the fixed stars, containing and fixing location for everything. Below it is Saturn, followed by Jupiter, then Mars; below it the sphere in which we move, then Venus and finally Mercury. The lunar sphere revolves around the centre of the Earth.’
It would seem that Copernicus had delivered a bombshell, but there was no explosion. Few people outside Poland heard about his book. His suggestions went largely undiscussed and unchallenged. The Catholic Church became aware of him but evidently didn’t regard his ideas as a threat. The Church had for at least two centuries been adopting a tolerant, hands-off attitude towards ideas that challenged traditional astronomy – even suggestions such as that from Nicholas of Cusa, one of its own cardinals. If any dyed-in-the-wool Ptolemaic astronomers recognized Copernicus as a potential challenge, they may have sagely decided that the best defence against the new model would be not to respond to it at all. Let it die in oblivion.
In 1512, Copernicus’s life story took a new turn with the death of his uncle. He left the castle at Lidzbark and went to live at Frombork, for he was still a canon of Warmia and Frombork was the seat of the Chapter. There, in a tower adjoining the cathedral, he would do his most important work. He described his residence there as ‘the remotest corner of the Earth’, which seemed not to bother him unduly or deflect him from his scholarship. Copernicus was a modest, quiet, man who saw little objection to having himself, and the Earth, removed from the centre of things.
During his years at Frombork, Copernicus made a number of astronomical observations – less accurately than the Greeks had done, for Copernicus was not particularly skilled at observational astronomy. He also began or continued work on a second book. However, although the death of his uncle seemed likely to leave Copernicus with more time to devote to his astronomy, there were serious distractions. He became involved in negotiations with the Teutonic Knights, one of the forces that periodically threatened to tear Poland apart. When diplomacy failed and fighting broke out, Copernicus moved to Olsztyn, though he was too stiff-necked to retreat to Gdansk with the rest of the canons and remained at Olsztyn, now under siege, to organize resistance. When the siege was finally lifted and the fighting stopped, he headed up relief operations. Copernicus became involved with problems of economics during the recovery after this conflict, and he wrote a short, insightful tract proposing currency reforms. It’s surprising to learn that had Copernicus not introduced Sun-centred astronomy, he might still be remembered as a minor historical figure in the field of economics.
Copernicus eventually got back to Frombork, where his duties as an administrator and doctor must still have consumed the greater part of his time. Nevertheless, he resumed work on his book. By now that may have been substantially completed, but he was a meticulous man, worrying over details, trying to confront and solve every problem presented in the astronomical data he had. He was frustrated for example by the discovery that the Earth’s whole orbit seemed to oscillate. He called these oscillations ‘trepidations’ and tried to account for them. Later astronomers found that these trepidations were an illusion. Copernicus had been worrying himself over nothing but the result of bad data. One of our own century’s great astronomers, Fred Hoyle, writes of his predecessors in his book Nicolaus Copernicus: An Essay on His Life and Work:
The early astronomers could not know which problems they could hope to solve. Perforce they had to take a shot at everything. And because insoluble problems were mixed up with soluble ones their task in dealing with the soluble ones was made all the harder. This must always be remembered in attempting to understand the difficulties which beset Ptolemy and Copernicus. Both expended much effort in attempting to understand the Moon, whereas they would probably have gone further with less effort if they had ignored this problem.
Copernicus’s friends urged him to publish his book while he was still fretting about its not being quite ready. We are reminded of Johannes Brahms carrying the completed manuscript of his first symphony around with him in his coat pocket, unable to bring himself to relinquish it to the public and wanting to be dead certain none of his friends did it for him. Copernicus was about to insist on a vision that disagreed with what nearly every intelligent, educated person had been thinking for millennia. He had become a well-known and well-respected astronomer and had no desire to appear an eccentric lunatic. His conflict with the astronomers of the past was a battle we think of as being fought over the big picture, but for Copernicus it was a battle fought in terms of technical and mathematical minutiae. Until he could work out these details to his own satisfaction, he could not feel he had succeeded. Even with all this concern, there were loose ends. Copernicus was convinced that his rearrangement of the universe could yield a far more harmonious and effective astronomy, but he failed to demonstrate this improvement as effectively as he hoped to do.
Copernicus had other worries dogging him besides his book. He was in his sixties now, no longer in the prime of health. Gnapheus, a minor playwright, produced a comedy, The Wise Fool, that mocked Copernicus. There were rumours of some ill-considered, scoffing dinner table remarks about moving the Earth coming from Martin Luther. Closer to home, Copernicus became embroiled in a demeaning squabble with the new Bishop of Warmia. Reports differ as to whether Copernicus had opposed or supported this man’s election, and whether it was a vindictive move when the Bishop undertook to remove Copernicus’s housekeeper Anna Szylling, a widow and distant relation on Copernicus’s mother’s side. She was a handsome, cultured woman whose presence in Copernicus’s house the Bishop (reportedly no paragon of morality himself) deemed suspect and unsuitable. Copernicus resisted for over a year but finally agreed to her departure.
Despite these griefs and distractions, in the late 1530s, 1,700 years after Aristarchus, Copernicus was at last drawing to a finish the book that ultimately would lead to the vindication of that ancient astronomer and be one of the most significant watersheds in human intellectual history – De revolutionibus orbium coelestium (Concerning the revolutions of the heavenly orbs). Copernicus wrote out the manuscript himself in longhand, as he had done with Commentariolus. This time there were more than two hundred pages. The book would elaborate on the sketch he had given in Commentariolus, his primary assertion again being that the Sun, not the Earth, must be considered the centre of the system.
While Copernicus was still labouring on De revolutionibus, rumour got out that something radical was in the making at Frombork. The circulation of Commentariolus was small, but it was significant, and Copernicus’s friends, particularly Bishop Tiedemann Giese, were spreading the word enthusiastically. Already in 1533, Pope Clement VII requested that his secretary explain these new Sun-centred theories to him. In 1536, Nicolaus Schönberg, Cardinal of Capua, wrote to Copernicus asking about his theories, and Copernicus sent him some explanations and tables. Cardinal Schönberg moved firmly into the Copernican camp. He urged Copernicus to allow his book to see the light of day and offered to pay for its publication and printing. Unfortunately, the Cardinal died before he could make good on his offer, but Copernicus mentioned this strong encouragement as well as that of Bishop Giese in the dedication of the book. However, it was not a Catholic churchman but a young mathematician named Rhaeticus, from Protestant Wittenberg, who at last persuaded Copernicus to publish his work.
Rhaeticus hadn’t had an enviable adolescence. When he was a teenager, his father was beheaded as a sorcerer, and Rhaeticus, who had previously been Georg Joachin von Lauchen, changed his name. Rhaetia was the province where he was born. Now he was a junior professor at the University of Wittenberg, and he was deeply impressed with what he heard about Copernicus’s ideas. In 1539 he travelled to Frombork to meet Copernicus in person. Rhaeticus evidently didn’t lack for courage, because Wittenberg, his university, was the centre of Lutheranism, while Warmia, where Copernicus was a canon of the cathedral, was Catholic and profoundly anti-Lutheran. But the two men, one 66, the other 22, seem to have hit it off splendidly, and Rhaeticus’s visit stretched on for two years. He paved the way for De revolutionibus by publishing a short volume of his own summarizing Copernican theory. His book was favourably received. Finally Copernicus agreed to publish.
The tale, as it continues, is a convoluted one. The favoured version is that Rhaeticus had to return to Wittenberg before Copernicus was quite prepared to part with the manuscript of his book. Rhaeticus took with him only some early mathematical chapters. A little later, with Copernicus’s consent, Bishop Giese sent the completed manuscript on to Rhaeticus. Rhaeticus took it to a Nuremberg publisher, intending to keep close watch over its printing. However, he was then appointed to a new position with a higher salary in Leipzig and delegated what remained of the proofreading to Andreas Osiander, a Lutheran clergyman who was more nervous about possible religious reactions than Rhaeticus was. The Catholic Church had had nothing to say one way or another, except for the support of Cardinal Schönberg and Bishop Giese, but there had been those adverse remarks from Luther. Osiander urged Copernicus to protect himself by writing a preface saying that his theory was intended to be taken hypothetically, not as a truth claim. Copernicus refused. He dedicated his book to Pope Paul III, a scholar interested in science. Osiander decided to write, himself, the preface Copernicus wouldn’t write. He left it unsigned, probably because he feared that his own anti-papal reputation would cast suspicions on Copernicus.
On 24 May 1543, about a month after the printing of De revolutionibus was completed, Copernicus died. Tradition has it that he saw the printed book. He had had a stroke and was bedridden, perhaps unconscious, so there is some doubt whether that story is true. Was he aware enough to learn that Osiander had written, anonymously, the preface he himself had refused to write, saying his new scheme was only hypothetical and containing the warning: ‘Beware if you expect truth from astronomy lest you leave this field a greater fool than when you entered’? If Copernicus knew of this, there is no record of his reaction.
Even after Copernicus’s prodigious effort and foot-dragging about publication, De revolutionibus did not make the case for Sun-centred astronomy as effectively as he had hoped. There were many loose ends. Though he had been able to eliminate the use of the equant, he’d still had to use epicycles and eccentrics to explain the movements of the planets. The result was hardly less complicated and cumbersome than Ptolemaic astronomy.
However, the new system definitely had some things going for it. The new arrangement of the heavens allowed Copernicus to come at the problem of the mysterious ‘reversing’ or ‘retrograde’ movement of the planets in an entirely fresh way. Retrograde movement occurs when a planet is in ‘opposition’, meaning that it is on the opposite side of the Earth from the Sun. (Only Mars, Jupiter, Saturn and the other outer planets discovered since Copernicus’s time can be in opposition. Venus and Mercury, whose orbits are closer to the Sun than Earth’s, can never be in opposition.) Most of the time, the planets move from west to east against the background of stars. However, around opposition a planet appears for a while to move east to west. Ptolemy had used epicycles to solve this problem. In the Copernican model, with all planets including the Earth orbiting the Sun, when one of the planets is in opposition, the Earth catches up and runs ahead of the other planet. For an analogy, imagine two racing cars, one on an inner track and the other on an outer track. We are riding in the one on the inner track. The stadium is completely dark except for a light on top of the car on the outer track and some distant streetlights way beyond that. When our car catches up with that car and moves on ahead, the light will appear to us (against the background of streetlights) to backtrack. If the motion of our car is so constant and smooth that we believe we are standing still, we’ll conclude that the other car has stopped for a moment, reversed, stopped again, and continued its forward motion. See Figure 2.5.
Figure 2.5 Copernicus’s explanation for the retrogression of a planet
The Sun is in the centre. The inner ring is the Earth’s orbit. The outer ring is the orbit of the planet. Place yourself at 1 on the Earth’s orbit, then at 2, and so forth, as the Earth moves in its orbit. The line drawn through the corresponding number on the planet’s orbit shows where the planet is in your line of sight in each instance. The squiggle at the top of the drawing shows the pattern these changes of position (of both Earth and planet) will produce against the background of distant stars, and why the planet will seem to ‘reverse’.
De revolutionibus also made sense of the fact that Mercury and Venus never stray far from the Sun. Ptolemaic astronomy had used deferents and epicycles to unravel this mystery. In Copernicus’s model, with the orbits of Mercury and Venus lying within the Earth’s orbit (they are both closer to the Sun than the Earth is), there is no mystery. Observers on Earth couldn’t possibly see these planets anywhere else but near the Sun. This explanation of the orbits of Mercury and Venus was one success of Copernicus’s model that many of his contemporaries could immediately appreciate.
Copernicus also addressed the ancient objections to the idea that the Earth rotates on its axis and moves in orbit. Judging from modern knowledge about the availability of certain books during his lifetime, most scholars conclude that when he wrote Commentariolus he probably didn’t know about Aristarchus’s suggestion that the Sun rather than the Earth is at the centre of the universe. However, it’s clear from statements in De revolutionibus that by the time he wrote that book he had heard about it. Copernicus explained that the Earth carries its atmosphere with it as it spins, and insisted, as Aristarchus had done, that the fact that we observe no stellar parallax proves the stars are extremely far away. Al Fargani had estimated the distance to the sphere of stars to be more than 75 million miles. Copernican astronomy required that the distance be 75 times as great as that. The vast amount of empty space this leaves between the sphere of Saturn and the sphere of the stars was, however, not reflected in an illustration from De revolutionibus (see illustration section), showing Sol, the Sun, at the centre of the universe, with seven planets in their spheres around it. Beyond those spheres is another named ‘Stellarum Fixarum Sphaera Immobilus’, the ‘immobile sphere of the fixed stars’. Copernicus, unlike Ptolemy and Ptolemaic astronomers, thought that the stars were stationary.
