Cusa was no practising astronomer, and he built no system; but his teaching shows that long before Copernicus not only the Franciscans at Oxford and the Ockhamists in Paris had broken loose from Aristotle and the walled-in universe, but that in Germany too there were men with a far more modern outlook than the Canon of Frauenburg. Cusanus died seven years before Copernicus was born; they had both been members of the German natio in Bologna, and Copernicus was acquainted with Cusa's teaching.
He was equally familiar with the work of his immediate predecessors: the German astronomer Peurbach and his pupil Regiomontanus, who, between them, had brought about the revival of astronomy as an exact science in Europe, after a millennium of stagnation. George Peurbach (1423-61) came from a small town on the Bavarian border, studied in Austria and Italy, where he knew Nicolas of Cusa, and became subsequently a professor at Vienna University, and Court Astronomer to the King of Bohemia. He wrote an excellent textbook on the Ptolemaic system, which had fifty-six later editions, and was translated into Italian, Spanish, French and Hebrew. 34 During his professorship at Vienna, he presided over a public discussion for and against the motion of the earth; 35 and though Peurbach, in his textbook, took a conservative attitude, he underlined the fact that the motions of all the planets were governed by the sun. He also mentioned that the planet Mercury rides on an epicycle whose centre moves not on a circular, but an egg-shaped or oval orbit. A number of other astronomers from Cusanus down to Copernicus' first teacher, Brudzewski, had also spoken tentatively of oval orbits. 36
Peurbach's work was continued by Johann Mueller from Koenigsberg, called Regiomontanus (1436-76), a Renaissance genius and infant prodigy, who, at the age of twelve, published the best astronomical yearbook for 1448, and at fifteen was asked by the Emperor Frederick III to cast a horoscope for the Imperial bride. He went to the University of Leipzig when he was eleven, and at sixteen became the pupil and associate of Peurbach in Vienna. Later he travelled with Cardinal Bessarion to Italy, to learn Greek and study Ptolemy in the original. After Peurbach's death, he edited the former's book on the planetary motions, then published his own treatise on spherical trigonometry, from which Copernicus is supposed to have heavily borrowed, without acknowledgement, in his own chapters on trigonometry. 36a
Regiomontanus' later years reflect a growing discontent with traditional astronomy. A letter, written in 1464, contains this typical outburst:
"... I cannot get over my amazement at the mental inertia of our astronomers in general who, like credulous women, believe what they read in the books, tablets and commentaries as if it were the divine and unalterable truth; they believe the authors and neglect the truth." 37
In another context, he says:
"It is necessary to keep the stars doggedly before one's eyes, and to rid posterity from ancient tradition." 38
It sounds like a polemic against the programme of Copernicus, who was not yet born, "to follow the methods of the ancients strictly and to hold fast to their observations which have been handed down to us like a Testament"!
In his middle thirties, Regiomontanus held a profitable position in Hungary at the court of King Mathias Corvinus. But he convinced his royal patron that Ptolemy could no longer be relied on, and that it was necessary to put astronomy on new foundations by patient observations, making use of such recent inventions as the corrected sundial and the mechanical clock. Mathias agreed, and in 1471, Regiomontanus went to Nuremberg where, with the help of a rich patrician, Johann Walther, he installed the first European observatory, for which he partly invented the instruments.
The manuscripts and notes of Regiomontanus' last years are lost, and there remain only scant indications of the reform of astronomy that he planned. But we know that he had paid special attention to Aristarchus' heliocentric system, as a note on one of his manuscripts shows. 39 And much earlier he, too, had noted that the sun ruled the motions of the planets. Towards the end of his life, he wrote on a piece of paper enclosed in a letter the words: "It is necessary to alter the motion of the stars a little because of the motion of the earth." The wording, as Zinner has shown, seems to indicate that the "motion of the earth" here refers not to the daily rotation but to its annual revolution round the sun; 40 in other words that Regiomontanus had arrived at the same conclusions as Aristarchus and Copernicus, but was prevented from going further by his untimely death. He died at forty, three years after Copernicus was born.
At the universities where Copernicus studied, the tradition of Cusa and Regiomontanus was very much alive. His principal teachers in astronomy: Brudzewski in Cracow, and Maria Novara in Bologna, both called themselves pupils of Regiomontanus. Finally, in Ferrara Copernicus met young Celio Calcagnini, poet and philosopher, who later published a short book with a significant title: Quomodo coelum stet, terra moveatur, vel de perenni motu terrae Commentario – "A Treatise concerning how the Heavens rest, the Earth moves, or on the perennial motions of the Earth". 41 Calcagnini, who had written a pretty poem to greet the arrival of Lucretia Borgia in Ferrara, was not a profound intellect; his thesis that the heavens are at rest, the earth in eternal movement, was inspired by Cusa and simply echoed an idea that was, as we saw, much in the air. He probably owed his insight to his friend and contemporary in Ferrara, Jacob Ziegler, an astronomer of some merit, who wrote a commentary on Pliny which contains the lapidary statement: "The motions of all planets depend on the sun."
More examples of a similar kind could be quoted, but I have said enough to show that the ideas of a moving earth, and of the sun as the true ruler of the planetary system, belonged both to the antique tradition of cosmology, and were much discussed in Copernicus' own time. Yet Canon Koppernigk was undoubtedly the first to develop the idea into a comprehensive system. This is his lasting merit, regardless of the inconsistencies and shortcomings of his system. He was not an original thinker, but a crystallizer of thought; and the crystallizers often achieve more lasting fame and a greater influence on history than the initiators of new ideas.
There is a well-known process in chemistry which will illustrate what I mean by a crystallizer. If you put kitchen salt into a glass of water until the water is "saturated" and will dissolve no more salt, and suspend a thread with a knot at its end in the solution, then after a while a crystal will form round the knot. The shape and texture of the knot are irrelevant; what matters is that the liquid has reached saturation point, and that a core has been provided round which it can start to crystallize. Cosmology at the end of the Middle Ages was saturated with vague notions of a spinning and moving earth, with echoes of the Pythagoreans, of Aristarchus and Herakleides, of Macrobius and Pliny, with the exciting suggestions thrown out by Cusa and Regiomontanus. Canon Koppernigk was the patient knot, suspended in the solution, who enabled it to crystallize.
I have tried to reconstruct the process from its starting point – Copernicus' discontent with Ptolemy's equants, which he regarded as an imperfection – to his re-shaping of the Ptolemaic system with the aid of an ancient idea which was being revived during his student days. But if it was really as simple as that, then the equally simple question arises: why nobody before him had worked out a heliocentric system? It would be meaningless to ask why nobody before Shakespeare had written Hamlet; but if Copernicus was really as devoid of originality and imagination as I tried to make him out, then it is legitimate to ask why the task of "crystallizing" fell to him – whereas, for instance, the intellectually more flexible, and "modern" Regiomontanus left it at a few hints, but never developed a systematic sun-centred theory.
The key to the answer is perhaps Kepler's already quoted remark that Copernicus was interpreting Ptolemy (and Aristotle) rather than nature. To a fifteenth century "modern" mind such an undertaking must have appeared partly impossible, and partly a waste of time. Only a conservative-minded person such as Copernicus could devote himself to the task of reconciling the irreconcilable doctrines of Aristotelian physics and Ptolemaic wheel-geometry on the one hand, with a sun-centred u
niverse on the other. To arrive at a self-consistent, and physically plausible heliocentric system, it was necessary first to wrench the mind free of the hold of Aristotelian physics, to shake off the obsession with circles and spheres, to smash up the whole jarring machinery of fictitious wheels-on-wheels. The great discoveries of science often consist, as we saw, in the uncovering of a truth buried under the rubble of traditional prejudice, in getting out of the cul-de-sacs into which formal reasoning divorced from reality leads; in liberating the mind trapped between the iron teeth of dogma. The Copernican system is not a discovery in this sense, but a last attempt to patch up an out-dated machinery by reversing the arrangement of its wheels. As a modern historian put it, the fact that the earth moves is "almost an incidental matter in the system of Copernicus which, viewed geometrically, is just the old Ptolemaic pattern of the skies, with one or two wheels interchanged and one or two of them taken out." 42 There is a well-known saying that Marx"turned Hegel upside down". Copernicus did the same to Ptolemy; in both cases, the reversed authority remained the bane of the disciple.
From Roger Bacon in the thirteenth century to Peter Ramus in the sixteenth, there had been outstanding individuals and schools who realized, more or less consciously, more or less articulately, that Aristotelian physics and Ptolemaic astronomy had to be put out of the way before a new departure could be made. That may be the reason why Regiomontanus built himself an observatory instead of building himself a system. When he had completed the commentaries on Ptolemy which Peurbach had begun, he realized the need to put astronomy on a new basis by "ridding posterity of ancient tradition". In Copernicus' eyes, such an attitude amounted to blasphemy. If Aristotle had stated that God created only birds, Canon Koppernigk would have described homo sapiens as a bird without feathers and wings who hatches his eggs before laying them.
The Copernican system is precisely that kind of construction. Apart from the inconsistencies which I have mentioned before, it did not even succeed in remedying the specific faults of Ptolemy which it had set out to remedy. True, the "equants" had been eliminated, but rectilinear motion, which Copernicus called "worse than a disease", had to be imported in their stead. In his Dedication, he had mentioned, beside the equants, as the chief reason for his enterprise, the uncertainty of existent methods to determine the length of the year; but the Revolutions shows no progress in this specific respect. Ptolemy's orbit of Mars disagreed conspicuously with the observed data, but in the Copernican system it was equally faulty – so, much so, that later on Galileo was to speak with admiration of Copernicus' courage in defending his system, although it was so evidently contradicted by the observed motions of Mars!
One last objection against the system, and perhaps the strongest of all, arose through no fault of its author. If the earth moves round the sun in a huge circle, with a diameter of about ten million miles, 43 then the pattern of the fixed stars ought to change continually according to the different positions which the earth occupies on its journey. Thus when we approach a certain group of stars, it ought to "open up", for the distances between the members of that group should appear to grow with our approach, and to shrink as we recede from it on our journey. Such apparent displacements of objects due to a change in the position of the observer are called parallax.
But the stars belied this expectation. They showed no parallax – their pattern remained fixed and immutable. 44 It followed that either the theory of the earth's motion was wrong – or the distance of the fixed stars was so immense that, compared to it, the circle described by the earth shrank to nothingness, and produced no noticeable effect. This was, in fact, Copernicus' answer; 45 but it was difficult to swallow and added to the inherent improbability of the system. As Burtt remarks: "Contemporary empiricists, had they lived in the sixteenth century, would have been the first to scoff out of court the new philosophy of the universe." 46
5. The First Repercussions
No wonder, then, that the publication of the "Revolutions" attracted very little attention. It created less of a stir than Rheticus' First Account of it. Rheticus had promised that the book would be a revelation; it turned out to be a disappointment. For more than fifty years, until the beginning of the seventeenth century, it raised no particular controversy either in public or among professional astronomers. Whatever their philosophical convictions about the structure of the universe, they realized that Copernicus' book did not stand up to scientific scrutiny.
If his name nevertheless enjoyed a certain repute among the generation which immediately succeeded him, this was due not to his theory of the universe, but to the astronomical tables which he had compiled. They were published in 1551 by Erasmus Reinhold, Rheticus' former associate at Wittenberg, and were welcomed by astronomers as a long overdue replacement for the Alfonsine Tables, which dated from the thirteenth century. Reinhold, after revising all figures and eliminating the frequent slips, paid in his preface generous tribute to Copernicus' labours as a practical astronomer, without mentioning at all the Copernican theory of the universe. The next generation of astronomers referred to the Tables as Calculatio Coperniciano, and this helped to keep the Canon's reputation alive, but it had little to do with the Copernican system. Leaving non-astronomers such as Thomas Digges, William Gilbert and Giordano Bruno for the moment aside, the Copernican theory was practically ignored until the opening of the seventeenth century, when Kepler and Galileo enter the scene. Then and only then, did the heliocentric system burst upon the world – like a conflagration caused by a delayed-action bomb.
The reaction of the Churches during the half century following Copernicus' death was equally indifferent. On the Protestant side, Luther gave out a few uncouth growls, while Melanchton elegantly proved that the earth was at rest; but he did not withdraw his patronage from Rheticus. On the Catholic side, the initial reaction, as we have seen, was one of encouragement, and the Revolutions was put on the Index in 1616 only – seventy-three years after its publication. There were occasional discussions as to whether the motion of the earth was compatible with Holy Scripture or not, but until the decree of 1616 the question remained undecided.
The clerical attitude of ironical indifference towards the new system is reflected in John Donne's Ignatius His Conclave. Here Copernicus appears as one of the four pretenders to the principal place next to Lucifer's throne, the other contenders being Ignatius of Loyola, Macchiavelli, and Paracelsus. Copernicus stakes his claim by declaring that he has raised the Devil and his prison, the earth, into the heavens, while relegating the sun, the Devil's enemy, into the lowest part of the universe: "Shall these gates be shut against me who have turned the whole frame of the world, and am thereby almost a new Creator?"
The jealous Ignatius, who wants the place of honour in Hell for himself, debunks Copernicus:
"But for you, what new thing have you invented, by which our Lucifer gets any thing? What cares hee whether the earth travell, or stand still? Hath your raising up of the earth into heaven, brought men to that confidence, that they build new towers or threaten God againe? Or do they out of this motion of the earth conclude, that there is no hell, or deny the punishment of sin? Do not men beleeve? Do they not live just as they did before? Besides, this detracts from the dignity of your learning, and derogates from your right and title of comming to this place, that those opinions of yours may very well be true... But your inventions can scarce bee called yours, since long before you, Heraclides, Ecphantus, and Aristarchus thrust them into the world: who notwithstanding content themselves with lower roomes among the other Philosophers, and aspire not to this place, reserved onely for Antichristian Heroes... Let therefore this little Mathematitian, dread Emperour, withdraw himselfe to his owne company."
Ignatius was published in 1611. It reflects, broadly speaking, the attitude of the two generations between Copernicus and Donne. But those two generations who ignored Copernicus were mistaken; the "little Mathematitian", that pale, sour, insignificant figure, ignored by his contemporaries and those who i
mmediately succeeded them, was to throw a giant shadow on the history of mankind.
How is this last paradox in a paradoxical story to be explained? How was it possible that the faulty, self-contradictory Copernican theory, contained in an unreadable and unread book, rejected in its time, was to give rise, a century later, to a new philosophy which transformed the world? The answer is that the details did not matter, and that it was not necessary to read the book to grasp its essence. Ideas which have the power to alter the habits of human thought do not act on the conscious mind alone; they seep through to those deeper strata which are indifferent to logical contradictions. They influence not some specific concept, but the total outlook of the mind.
The heliocentric idea of the universe, crystallized into a system by Copernicus, and restated in modern form by Kepler, altered the climate of thought not by what it expressly stated, but by what it implied. Its implications were certainly not conscious in Copernicus' mind, and acted on his successors by equally insidious, subterranean channels. They were all negative, all destructive to the solid edifice of medieval philosophy, undermining the foundations on which it rested.
6. The Delayed Effect
The medieval Christian universe had hard, firm limits in space, time, and knowledge. Its extension in time was limited to the relatively short span between the creation of the world, which lay some five thousand years back, and the second coming of Christ which lay ahead, and which many expected to occur in the foreseeable future. Thus the history of the universe was thought to be limited to something of the order of two or three hundred generations from beginning to end. God had modelled his world on the art form of the short story.