But everything seemed to go wrong from the beginning. The salary of three thousand florins which the Emperor had granted Tycho beat all previous records; "there was nobody at Court, not even among counts and barons of long service, who enjoyed so large an income". 1 Both the mind of Rudolph II, and his finances, were in a highly disordered state; and his court officials effectively sabotaged the carrying out of his extravagant royal promises. Tycho had to fight for his salary and to be content if he could squeeze half of it out of the Exchequer; when Kepler succeeded him, he would get only a dribble of what was due to him.
By the time Kepler arrived at Benatek, Tycho had already quarrelled with the Director of the Crown Estates who held the purse-strings, complained to the Emperor, threatened to leave Bohemia, and to tell the world the reasons. Also, several of Tycho's assistants, who had promised to join him at the new Uraniburg, had failed to turn up; and the largest instruments were still delayed on the long trek from Hveen. Towards the end of the year the plague had broken out, obliging Tycho to sit it out with Rudolph at the imperial residence in Girsitz, and supply him with a secret elixir against epidemics. To add to Tycho's worries, Ursus, who had disappeared from Prague on Tycho's arrival, now returned again, trying to create trouble; and Tycho's second daughter, Elisabeth, was having an illicit love affair with one of his assistants, the Junker Tengnagel. Young Kepler, in the provincial backwoods of Gratz, had dreamed of Benatek as a serene temple of Urania; he arrived at a mad-house. The castle was teeming with workmen, surveyors, visitors, and the formidable de Brahe clan including the sinister dwarf Jepp – huddled under the table during the interminable, tumultuous meals, and finding an easy butt for his sarcasms in that timid scarecrow of a provincial mathematicus.
Kepler had arrived in Prague in the middle of January. He had at once written to Benatek, and a few days later received an answer from Tycho, regretting that he could not welcome Kepler in person because of a forthcoming opposition of Mars and Jupiter, to be followed by a lunar eclipse; and inviting him to Benatek "not so much as a guest, than as a very welcome friend and colleague in the contemplation of the skies". The bearers of the letter were Tycho's eldest son and the Junker Tengnagel, both of whom were jealous of Kepler from the start, and remained hostile to the end. It was in their company that Kepler completed the last lap of his journey to Tycho – but only after a further delay of nine days. Tengnagel and Tycho Junior were probably having a good time in Prague, and were in no hurry to get back.
At last, then, on 4 February, 1600, Tycho de Brahe and Johannes Keplerus, co-founders of a new universe, met face to face, silver nose to scabby cheek. Tycho was fifty-three, Kepler twenty-nine. Tycho was an aristocrat, Kepler a plebeian; Tycho a Croesus, Kepler a church-mouse; Tycho a Great Dane, Kepler a mangy mongrel. They were opposites in every respect but one: the irritable, choleric disposition which they shared. The result was constant friction, flaring into heated quarrels, followed by half-hearted reconciliations.
But all this was on the surface. In appearance, it was a meeting of two crafty scholars, each determined to make use of the other for his own purposes. But under the surface, they both knew, with the certainty of sleepwalkers, that they were born to complete each other; that it was the gravity of fate which had drawn them together. Their relationship was to alternate all the time between these two levels: qua sleepwalkers, they strolled arm in arm through uncharted spaces; in their waking contacts they brought each out the worst in the other's character, as if by mutual induction.
Kepler's arrival led to a reorganization of work at Benatek. Previously, Tycho's younger son, Joergen, had been in charge of the laboratory, the senior assistant, Longomontanus, was assigned the study of the orbit of Mars, and Tycho had intended to put Kepler in charge of the next planet to be taken up for systematic observation. But his eagerness, and the fact that Longomontanus got stuck with Mars, led to a re-distribution of the planetary realm among the Tychonites: Kepler was given Mars, the notoriously most difficult planet, while Longomontanus was switched to the moon. This decision proved of momentous importance. Kepler, proud to be entrusted with Mars, boasted that he would solve the problem of its orbit in eight days, and even made a bet with this deadline. The eight days grew into nearly eight years; but out of the struggle of these years with the recalcitrant planet emerged Kepler's New Astronomy or Physics of the Skies.
He knew, of course, nothing of what lay ahead of him. He had come to Tycho to wrench from him the exact figures of the eccentricities and mean distances, in order to improve his model of the universe built around the five solids and the musical harmonies. But though he never discarded his idée fixe, it was now relegated into the background. The new problems which arose out of Tycho's data "took such a hold of me that I nearly went out of my mind". 2 Himself no more than an amateur observer with the coarsest of instruments, an armchair astronomer with the intuition of genius but still lacking in intellectual discipline, he was overwhelmed by the wealth and precision of Tycho's observations, and only now began to realize what astronomy really meant. The hard facts embodied in Tycho's data, the scrupulousness of Tycho's method, acted like a grindstone on Kepler's fantasy-prone intellect. But although Tycho did the grinding, and the process seemed to be more painful for Kepler than for him, in the end it was the grindstone which was worn down, while the blade emerged sharp and shining from it.
Soon after his arrival in Benatek, Kepler wrote:
"Tycho possesses the best observations, and thus, so-to-speak, the material for the building of the new edifice; he also has collaborators and everything he could wish for. He only lacks the architect who would put all this to use according to his own design. For although he has a happy disposition and real architectural skill, he is nevertheless obstructed in his progress by the multitude of the phenomena and by the fact that the truth is deeply hidden in them. Now old age is creeping upon him, enfeebling his spirit and his forces." 3
There could be no doubt regarding the identity of the architect in Kepler's mind. Nor was it difficult for Tycho to guess Kepler's true opinion of him. He had amassed a treasure of data as nobody before him; but he was old, and lacking the boldness of imagination to build, out of this wealth of raw material, the new model of the universe. Its laws were there, in his columns of figures, but "too deeply hidden" in them for him to decipher. He must also have felt that only Kepler was capable of succeeding in this task – and that nothing could prevent him from succeeding; that it would be this grotesque upstart, and not Tycho himself, nor the hoped-for Tychonides of the Uraniburg mural, who would reap the fruit of his lifelong labours. Half resigned to, half appalled by his own fate, he wanted at least to make it as difficult for Kepler as possible. He had always been most reluctant to disclose his treasured observations; if Kepler had thought he could simply grab them, he was woefully mistaken – as the indignant complaints in his letters show:
" Tycho gave me no opportunity to share in his experiences. He would only, in the course of a meal, and in between conversing about other matters mention, as if in passing, today the figure for the apogee of one planet, tomorrow the nodes of another." 4
One might add: as if he were handing bones to Jepp under the table. Nor would he allow Kepler to copy out his figures. In exasperation, Kepler even asked Tycho's Italian rival, Magini, to offer his own data in exchange for some of Tycho's. Only gradually, step by step, did Tycho yield; and when he put Kepler in charge of Mars, he was forced to disgorge his Mars data.
Kepler had spent barely a month at Benatek when Tycho, in a letter, first hinted at difficulties that had arisen between them; another month later, on 5 April, the tension blew up in an explosion which might have shattered the future of cosmology.
The immediate cause of the row was a document which Kepler had drafted, and in which the conditions of his future collaboration with Tycho were laid down in unpleasant detail. If he and his family were to live permanently at Benatek, Tycho must provide them with a detached apartment because the noise an
d disorder of the household were having a terrible effect on Kepler's gall, and provoked him to violent outbursts of temper. Next, Tycho must obtain a salary for Kepler from the Emperor, and in the meantime pay him fifty florins a quarter. He must also provide the Keplers with specified quantities of firewood, meat, fish, beer, bread and wine. As for their collaboration, Tycho must leave Kepler his freedom to choose the time and subject of his work, and only ask him to undertake such researches which were directly connected with it; and since Kepler was "not in need of a spur but rather of a brake to prevent the threat of galloping consumption due to overwork", 5 he must be allowed to rest in the day-time if he had worked deep into the night. And so on, for several pages.
This document was not meant for Tycho's perusal. Kepler handed it to a guest, a certain Jessenius, professor of medicine in Wittenberg, who was to serve as an intermediary in the negotiations between Tycho and himself. But whether by chance or intrigue, Tycho got hold of the document, which he could hardly regard as flattering to himself. Nevertheless he took it with that good-humoured magnanimity which lived side by side in the Danish grand seigneur with jealousy and bullying. He remained a benevolent despot, so long as nobody challenged his rule; and socially, Kepler was so much his inferior that his carping and bickering demands did not affect Tycho as a challenge. One of the reasons for Kepler's bitterness was, incidentally, that he had been assigned an inferior position at the dinner table.
But above all, Tycho needed Kepler, who alone could put his life-work into proper shape. Hence he sat down to negotiate with Kepler in the presence of Jessenius, patiently rubbing ointment on his nose, a paragon of paternal moderation. This attitude grated even more on Kepler's inferiority complex, and he attacked Tycho, in the latter's words "with the vehemence of a mad dog, to which creature he, Kepler himself, so much likes to compare himself in irritability." 6
Immediately after the stormy session Tycho, who always had an eye on posterity, wrote down the minutes of it, and requested Jessenius to endorse them. However, when his temper had cooled down, he entreated Kepler to stay on, at least for another few days, until an answer arrived from the Emperor, whom Tycho had approached concerning Kepler's employment. But Kepler refused to listen, and on the next day departed in the company of Jessenius to Prague, where he took quarters with Baron Hoffman. Just before his departure, Kepler had another choleric outburst; at the moment of farewell, he was overcome with remorse and apologized; while Brahe whispered into Jessenius' ear that he should try to bring the enfant terrible back to reason. But as soon as they arrived in Prague, Kepler wrote another abusive letter to Tycho.
He must have been in a dreadful state of hysteria. He was suffering from one of his recurrent obscure fevers; his family was in faraway Gratz; the persecution of the Protestants in Styria, and the debacle at Benatek had made a shambles of his future; and the data on Mars remained inaccessibly in Tycho's hands. Within a week, the pendulum swung to the other extreme: Kepler wrote a letter of apologies to Tycho which sounds like the ravings of a masochist against his own guilty ego:
"The criminal hand which, the other day, was quicker than the wind in inflicting injury, hardly knows how to set about it to make amends. What shall I mention first? My lack of self-control, which I can only remember with the greatest pain, or your benefactions, noblest Tycho, which can neither be enumerated nor valued according to merit? For two months you have most generously provided for my needs ... you have extended to me every friendliness, you have allowed me to share in your most cherished possession... Taken all in all, neither to your children, nor to your wife, nor to yourself did you devote yourself more than to me... Therefore I think with the deepest dismay that God and the Holy Ghost delivered me to such an extent to my impetuous attacks and to my sick mind that instead of displaying moderation, I indulged during three weeks with closed eyes in sullen stubbornness against you and your family; that instead of thanking you, I displayed blind rage; that instead of showing you respect I displayed the greatest insolence against your person which by noble descent, prominent learning and great fame deserves all respect; that instead of sending you a friendly greeting I let myself be carried away by suspicion and insinuation when I was itching with bitterness... I never considered how cruelly I must have hurt you by this despicable behaviour... I come to you as a postulant to ask, in the name of Divine pity, for your forgiveness of my terrible offences. What I have said or written against your person, your fame, your honour and your scientific rank... I retract in all parts, and declare it voluntarily and freely as invalid, false and unsound... I also promise sincerely that henceforth at whatever place I shall be I shall not only refrain from such foolish acts, words, deeds and writings, but I shall also never and in no way unjustly and deliberately offend you... But since the ways of men are slippery, I ask you that whenever you notice in me any tendency towards such unwise manner of behaviour, to remind me of myself; you will find me willing. I also promise ... to oblige you by all kinds of services and ... thus to prove by my acts that my attitude towards your person is different, and always was different, from what one may conclude from the reckless condition of my heart and body during these last three weeks. I pray that God may help me to fulfil this promise." 7
I have quoted this letter at some length, because it reveals the tragic core of Kepler's personality. These turns of phrase do not seem to come from a scholar of repute, but from a tortured adolescent, begging to be forgiven by a father whom he hates and loves. Tycho had replaced Maestlin. At the base of his iridescent, complex character, Kepler always remained a waif and stray.
But Tycho was no less dependent on Kepler than Kepler on Tycho. In their worldly contacts, Tycho was the old man of the tribe, Kepler the nagging, ill-mannered adolescent. But on that other level, the rules were reversed: Kepler was the magician from whom, Tycho hoped, would come the solution of his problems, the answer to his frustrations, the salvation from ultimate defeat; and however foolishly they both behaved, qua sleepwalkers, they both knew all this.
Therefore, three weeks after the row, Tycho turned up in Prague and drove Kepler back to Benatek in his coach – one can almost see Tyge's great fat arm in the leg-of-mutton sleeve, crushing in an affectionate embrace Kepler's skimpy bones.
2. The Inheritor
Altogether the association between Kepler and Tycho lasted for eighteen months, until Tycho's death. Fortunately for both, and for posterity, they were only part of this time in personal contact, for Kepler twice returned to Gratz and spent a total of eight months there to settle his affairs and get his wife's property out.
He left for Gratz the first time shortly after his reconciliation with Tycho, in June 1600. Though peace had been re-established, nothing definite had been settled regarding their future collaboration, 7a and Kepler was in two minds whether he would return to Tycho or not. He still hoped either to save his position and salary in Gratz by being granted a long leave of absence, or to obtain a chair in his native Wuerttemberg – his lifelong ambition. He wrote to Maestlin and Herwart, his adoptive fathers Nos. One and Two, hinting that No. Three was rather a disappointment; but nothing came of it. He sent to the Archduke Ferdinand a treatise on a solar eclipse, also to no avail; but in that treatise he hit on something for which he had not looked: that there was "a force in the earth" which influenced the moon's motion, a force which diminished in proportion to distance. As he had already attributed a physical force to the sun as an explanation of the motions of the planets, the dependence of the moon on a similar force in the earth was the next important step towards the concept of universal gravity.
But such trifles could not deter the Archduke from his plan to stamp out heresy in his lands. On 31 July and the following days, all Lutheran citizens of Gratz, a little over a thousand in number, had to appear, one by one, before an ecclesiastical commission, and either to declare their willingness to return to the Roman faith, or to suffer expulsion. This time no exemption was made, not even for Kepler – though he was let off pay
ing half of the exit levy and granted other financial privileges. The day after he appeared before the commission, a rumour was rife in Gratz that he had changed his mind and declared his readiness to become a Catholic. Whether he had really wavered or not, is impossible to know; but in any case, he overcame the temptation and accepted exile with all its consequences.
He sent a last S.O.S. to Maestlin. 8 It starts with a dissertation on the eclipse of the sun on 10 July, which he had observed through a camera obscura of his own construction, erected in the middle of the market place in Gratz – with the twofold result that a thief stole his purse containing thirty florins, while Kepler himself discovered an important new optical law. The letter continues with the threat that Kepler plus his family would travel down the Danube into Maestlin's arms and a professorship (even if only a small one) which Maestlin would no doubt provide; and ends with the request that Maestlin should pray for him. Maestlin answered that he would gladly pray, but could do nothing else for Kepler, "the steadfast and valiant martyr of God"; 9 and after that, answered none of Kepler's letters for four years. He probably thought that he had done his share, and that it was now Tycho's turn to look after the infant prodigy.
Tycho himself was delighted with the sad news. He had doubted whether Kepler would return to him, and welcomed the prospect all the more as his senior assistant, Longomontanus, had in the meantime left. When Kepler informed him of his impending expulsion, he wrote back that Kepler should come at once; "do not hesitate, make haste, and have confidence". 10 He added that during a recent audience with the Emperor he had requested that Kepler should be officially attached to his observatory, and that the Emperor had nodded his consent. But in a postscript to the long and affectionate letter, Tycho could not refrain from alluding to a subject which had been one of the main reasons for Kepler's unhappiness at Benatek. On his arrival there, Tycho had imposed on him the irksome chore of writing a pamphlet refuting the claims of Ursus; and though Ursus had in the meantime died, Tycho still insisted on persecuting him beyond the grave. Moreover, Kepler was also to write a refutation of a pamphlet by John Craig, physician to James of Scotland, in which Craig had dared to doubt Tycho's theories about comets. It was not a joyous prospect for Kepler to waste his time on these futile labours to serve Tycho's vanity; but now he had no other choice.