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  Life for the exiles at Benatky was chaotic, noisy, crowded and yet isolated, 'a reigning loneliness of people,' in Kepler's mournfully poetic description - the Brahes, after all, were farther away from home than he was. Mealtimes on the upper floor of the castle were a torment for Kepler, a ceaseless din of raucous Danish talk and the clatter of crockery and wine mugs. Lord Brahe presided gloomily at the head of the table, his dwarf jester Jeppe squatting cross-legged at his feet, while his wife and their daughters squabbled and shrieked, and the numerous attendants and scientific assistants gossiped endlessly while jostling for placement above the salt. Hogsheads of wine were swilled down, so that the normally abstemious Kepler must have spent the first weeks of his stay in a more or less permanent semi-stupor. The access to astronomical treasures that Tycho had promised him was not forthcoming. Tycho himself was not forthcoming. In the course of dinner Kepler would wheedle his way up the table to where the great man sat, ignoring him except on the rare occasions when he deigned to let fall, like a scrap from his plate, a bit of information on the orbit of Mars, or lunar occlusions, or coming conjunctions between this or that of the planets. Where was that 'companionship in our observations' that Tycho had so enticingly offered? Instead of the equal in scientific knowledge that Tycho had seemed to consider him, he was, he realised, no more to the Dane than a domesticus, a hired man. What he did not realise was the extent of Tycho's wariness and sense of foreboding. Although Kepler was not yet the scientist that he would be in later years, he was, Tycho knew, a formidable rival in the race for immortality. One of the strong reasons for Tycho's unwillingness to give up his precious astronomical data to this young man half his age was the fear that Kepler the Copernican would use them to prove that Copernicus's sun-centred system was correct. For Tycho had his own system, a not inelegant one but, as Kepler would indeed prove, no more than a hopelessly mistaken compromise between Ptolemy's ancient geocentric model and the heliocentric version proposed by Copernicus.

  In the weeks and months that followed, the little dog which Kepler had once compared himself to turned snappish, and on occasion even vicious.34 Grudgingly, Tycho had opened the coffers of his accumulated observations and given him the orbit of Mars to work on. Careful as always, however, he placed Kepler under the supervision of another Tychonic assistant, Christian Sorensen, called Longomontanus after the Danish village of Longberg where he was born how they did love those Latinate puns! - a mild, well-meaning man whose authority over him Kepler deeply though silently resented. Yet the two men worked well together, thanks mainly to Longomontanus's tolerance and unmistakable brilliance as an astronomer. In time, Tycho relaxed enough to reassign Longomontanus to lunar theory - the moon was an important player in the drama of the Tychonic system - and allow Kepler to continue to work on Mars alone, but not before he had compelled Kepler to sign a pledge not to reveal any of the secrets of the new Uraniborg to the outside world. The assignment of the Mars project to Kepler was one of history's luckier chances, since the eccentricities of that planet's orbit could only be accounted for in relation to the position of the sun, a fact which supported Kepler's long-held theory that the sun is the source of planetary motion. Those weeks of work on Mars marked the maturing of Kepler's genius as a theoretical scientist.

  Growing into his greatness, Kepler began to clamour for his rights. He demanded a contract from Tycho, one that would recognise him as an equal partner in the great cosmological project under way at Benatky, and guarantee him fitting recompense for his labours. Throughout that spring, negotiations between the two men dragged on. Kepler demanded that he be paid two separate salaries, one from Tycho and one from the Emperor, that he should have all afternoons free to work on his own theories, and that he and his family - Barbara and her daughter were still in Graz, anxiously awaiting the summons to Benatky should be given a house to themselves, away from the castle and the disorderly life there. Not the least remarkable aspect of these discussions was the fact that while Kepler's hysteria and paranoia grew, Tycho displayed wholly uncharacteristic patience and forbearance. He was still suspicious of Kepler's Copernican leanings, but recognised, however unwillingly and with whatever foreboding, the young man's genius. It is possible too that beneath the aristocratic hauteur, Tycho simply liked his excitable, energetic and unintentionally comic collaborator. Certainly he indulged Kepler in ways that the other workers at Benatky would not have dared to dream of.

  At the beginning of April, Tycho and Kepler sat down to thrash out an agreement, with the Emperor's chief physician, Jan Jesensky, acting as referee. Kepler had written to Tycho setting out his demands, and now Tycho produced a document in response, the main element of which was the secrecy pledge. If Kepler signed, Tycho would press the Emperor to grant Kepler a decent salary, would try to find a house for him and his family, and would pay travelling expenses for Barbara and her daughter to come from Graz. Kepler's demand for Sundays and holidays free Tycho regarded as an impertinence, insisting that he had never asked his assistants to work on those days. There was that word again: assistant. Kepler was adamant: either his demands must be met in full, or there would be no agreement. Despite Dr Jesensky's best emollient efforts the meeting broke up in rancour. At dinner that evening, in the presence of the Brahe household, Kepler got drunk on wine and launched a shrill attack on Tycho, who responded with equal energy. One imagines the scene, little Kepler, red with rage and too much alcohol, waving his fists and shrieking, while the Dane grips the edge of the table as if preparatory to upending it, the rumblings of his anger sounding like a ground bass under Kepler's frantic pipings. The following day, Kepler walked out, and returned to Prague in the company of Je­sensky. Once again, Tycho displayed extraordinary restraint, although he did inform Jesensky before the two left that a written apology from Kepler would be required before he could return to Benatky and resume his work. It might be thought that this demand would send Kepler into greater heights of indignation and rage, but once back in Prague, staying probably at Baron Hoffmann's house, and no doubt urged to caution by Jesensky and the good Baron, he bethought himself and the perils of his position, and wrote a letter of apology to Tycho notable for its florid abjectness. The little dog had come to heel. Relieved, Tycho took the unprecedented step of summoning his carriage at once and riding into Prague in person to fetch the prodigal home to Benatky. Spring sunshine outside the Hoffmann house, and a humbled Kepler steps forth, blinking; alighting from his carriage the Dane sweeps forward, his metal nose agleam; a brocaded arm is thrown around drooping shoulders, gruff words are exchanged; the Baron and Dr Jesensky beam at each other over Ke­pler's head; the bells of St Vitus's begin to bang out a general rejoicing.

  Back at Benatky, Tycho and Kepler quickly came to agreement on the latter's terms of employment. The Emperor would appoint Kepler as Tycho's assistant for a term of two years, during which time Kepler would continue to receive his salary as Styria's District Mathematician, along with a grant of half that amount again from the imperial purse. Arrangements were also put in place to fetch Kepler's wife and stepdaughter from Graz. In May Kepler travelled south to Styria, accompanied, at Tycho's direction, by the scapegrace Frederick Rosenkrantz, who was on his way to Vienna to join the Austrian army to fight against the Turks.35 At last all seemed set fair for Kepler's life and work; as usual, everything went wrong. On June 10th, Rudolf returned to Prague from where he had gone nine months before to escape the plague. There was a backlog in the affairs of state, many decisions were called for, and the advice of the Imperial Mathematician - read: imperial astrologer - would be required on a daily, nay, an hourly basis. Tycho must come at once to Prague. Accommodation was arranged for him, his family and assistants at The Golden Griffin. Tycho, of course, was appalled. Work on Benatky was nearing completion, the northern shipping lanes had thawed sufficiently to allow the rest of his instruments to be sent down from Hven, and now, suddenly, he must abandon the New Uraniborg and be subject once more to the whims of an Emperor whose extreme eccentric
ities seemed to be tumbling over into plain madness. It was small comfort to the Dane when Rudolf expelled the Capuchins and their unbearable bells from their monastery behind The Golden Griffin; the good monks insisted Tycho was behind the expulsion, since the odour of sanctity which their prayers diffused about the would surely be a hindrance to the dark and devilish works in which Brahe the well-known alchemist was no doubt engaged.36 Tycho indeed had complained of the inadequacies of The Golden Griffin, so loudly that the Emperor quickly agreed to resettle him and his people in a house 'near Baron Hoffman's' on present-day Tycho-nova Street.37Rudolf further directed that Tycho might set up his astronomical instruments on the superb arcade of the very beautiful imperial summer palace, the so-called Belvedere.38 These facilities were not ideal, certainly not when compared with those at Benatky; when he had installed his instruments in the new premises - and his library of three thousand books - Tycho discovered to his dismay that a large part of the sky in the southwest was obscured by the buildings of the royal place. Still, he would have to make do.

  Meanwhile, in Graz, Kepler was floundering in water that got hotter and hotter as the summer advanced. First of all the Styrian authorities had refused to grant him leave to work in Prague, then said they would not continue to pay his salary as District Mathematician, despite the Emperor's instructions - Protestant Styria gave scant heed to the wishes of Rudolf the Catholic. Kepler's hopes of working with Tycho were waning, and in desperation he sought the sponsorship of the Austrian Archduke, Ferdi­nand II. Ferdinand did not reply to Kepler's beseechings; worse, at the end of July he issued a decree expelling from the province all Protestants unwilling to convert to Catholicism. Ke­pler, whose increasingly radical scientific theories served only to strengthen his Lutheran faith, would not contemplate conversion. Faced by an inquisition panel headed by Ferdinand himself, he stuck to his faith, and along with sixty others of his stubborn co-religionists was given six weeks and three days to quit Graz. He realised at once that Prague, formerly the site of all his hopes, was now the only hope remaining to him, and that he must once more throw himself on Tycho's mercy. By mid-October, accompanied by Barbara and his stepdaughter, he was back in the city, exhausted, burning with fever, but knowing he was lucky to have this refuge; as he later wrote, 'God let me be bound with Tycho through an unalterable fate and did not let me be separated from him by the most oppressive hardships.' It is a mark of Rudolf's extraordinary religious tolerance that a man who had been banished from Styria on confessional grounds should be allowed to return to Prague by a Catholic Emperor who, in theory at least, was ruler of the Styrian province that had expelled him as a Lutheran. Kepler and his little family were taken in first by the long-suffering Baron Hoffmann - what, one wonders, was the Baroness's opinion of her husband's unfaltering hospitality? - and later moved in with Tycho and the gang.

  It was a hard time all round. Rudolf was still in the throes of dementia, more secretive and paranoid than ever. Tycho was summoned regularly to the palace, sometimes twice or three times a day, to offer astrological advice and, inevitably, to fight for favour among the machinations of an increasingly chaotic court. By now he must have despaired of returning to Benatky. Indeed, in that autumn and winter of 1600 the worm of a general despair seems to have begun to gnaw at him. He was in his middle fifties, a considerable age in those times, and must have been exhausted after more than thirty years of struggling with princes and potentates for the means whereby to fulfil his dream of vindicating the Tychonic system of planetary motion. Although his hated rival Ursus was dead by now, the Ursine legacy lingered, and Kepler was hardly back in Prague before he found himself forced by Tycho to take up again the task of rebutting 'even more clearly and more fully than you have [done] previously Ursus's distorted and dishonest objections to my invention of the new hypothesis,' that is, the Tychonic system. Kepler got to work without enthusiasm on the Apologia Tychonis contra Ursum. He was never to finish the book, although the fragment of manuscript he did complete was published in the nineteenth century. Throughout that winter, plagued by a fever he could not shake off, Kepler laboured on the Apologia, with little time for his own astronomical concerns, although he did manage to do a little work on the orbits of Mercury, Mars and the moon. The following spring he was back in Graz, trying vainly to secure his wife's confiscated holdings. By the autumn he had returned to Prague. There, Tycho escorted him to the royal palace for a first and, as it would prove, momentous meeting with the Emperor.

  Rudolf by now had regained his sanity, such as it was, and Tycho had a proposition to put to him. He would publish, with the help of his assistant Johannes Kepler, a great set of astronomical tables, based on decades of celestial observations and, not incidentally, founded on the Tychonic system, to be called the Tabulae Rudolphinae. The Emperor, delighted at the thought of being thus immortalised, readily agreed. In another perhaps uncharacteristic but admirable display of generosity, Tycho stipulated that for the venture to go ahead, Kepler would have to be granted an imperial salary. Again Rudolf nodded assent. Kepler, one surmises, found it hard to know which was the more welcome outcome of this royal meeting, the fact that he was to have a guaranteed wage, or that Tycho had talked himself into a position in which he would find it necessary at last to surrender the observational treasures he had guarded so jealously for so long.

  Kepler now suddenly found himself in a favoured position in Tycho's laboratory and in the Brahe household, no longer an assistant but, whether it was acknowledged or not, the Dane's peer, and partner in science. This stellar partnership, however, was not to last for long. On October 13th, a few days after the meeting with the Emperor, Tycho went with a friend, one Councillor Minckwicz, to dine at the Schwarz-enberg Palace, the home of Peter Vok Ursinus39 Rozmberk, where he drank too much wine and rapidly found himself in urgent need of emptying his bladder. Good manners forbade a guest to rise from the table before his host had done so, and Tycho, ever a stickler for the social niceties, 'felt,' in Kepler's account, 'less concerned for the state of his health than for etiquette.' Grimly he waited, but was either very abstemious or had a prodigious capacity for liquids, and by the time Tycho managed to get to the jakes he found he could not urinate. He returned home, but was still blocked. Kepler again: 'Uninterrupted insomnia followed; intestinal fever; and little by little, delirium. His poor condition was made worse by his way of eating, from which he could not be deterred.' As he lay on what by now he must have known was his deathbed, he begged Ke­pler, despite his Copernican convictions, to 'present all [Kepler's] demonstration in conformity with [Tycho's] hypothesis,' and repeated over and over, 'like,' according to Kepler, 'a composer creating a song,' the heartbreaking impreca­tion: 'Let me not seem to have lived in vain!' On October 24th, Kepler continued, 'when his delirium had subsided for a few hours, amid the prayers, tears and efforts of his family to console him, his strength failed and he passed away very peacefully.'40 He was buried in the Tyn church on Old Town Square, with grand ceremonial, his coffin draped in black cloth decorated in gold with the Brahe coat of arms - to this day, probably coincidentally, black and gold are the predominant colours in the interior of this rather forbidding church - his wife following, 'escorted,' according to Kepler's account 'by two distinguished old royal judges, and finally his three daughters, one after the other, each escorted by two noblemen.' Tycho had been ennobled by the Emperor, which meant that Kirsten had at last been 'made an honest woman of, and their children were now fully legitimate, in Bohemia, at least. The Dane would have been gratified by the send-off accorded him by his adopted city. 'The streets were so full of people,' Kepler wrote, 'that those in the procession walked as if between two walls, and the church was so crowded with both nobles and commoners that one could scarcely find room in it.'41

  Tycho Brahe's tomb still survives in the Tyn church, surmounted by a life-sized effigy carved in relief in pinkish-grey marble, and bearing a splendid if slightly obscure epitaph: 'To be rather than to be perceived.'

  T
he end of Tycho's mortal life marked the beginning in earnest of Kepler's professional career. Two days later, with the Dane hardly cold in his grave, imperial secretary Barwitz came with the news that the Emperor had appointed Kepler to succeed Tycho as Imperial Mathematician; even death would not be allowed to delay work on the Rudolphine Tables. Kepler's salary, he was shocked to hear, would be six times less than that which had been paid, or at least promised, to Tycho. On the other hand, Kepler now had unrestricted access to Tycho's observations and the use of his instruments, the Emperor having purchased Brahe's astronomical effects from the Brahes for a promised 20,000 florins, although use of the instruments would hardly benefit the bespectacled, double-visioned Kepler. He and Barbara moved from the Hradcany to a house on Vysehradska Street in the Old Town, not far from the Faust House and opposite the Emmaus Monastery.42 Despite domestic woes his marriage was unhappy, his children died and unseemly squabbles with the Brahes,43 the years he spent in Prague as Imperial Mathematician were the perigee of Kepler's life, the time when he came nearest to the things he desired, gilt rooms if not gold, and, if not spontaneous applause, at least the odd royal clap on the back. He did some of his greatest work in Prague, on many and diverse subjects, from the orbit of Mars through the functioning of the human eye to the structure of snowflakes, and completed the first of his masterpieces of theoretical science, the justifiably titled Astronomia nova. He kept Ty­cho's dying plea in mind, and gave the Dane his due recognition, but he could not vindicate Ty­cho's misconceived system. As one biographer neatly puts it, '[h]istory celebrates the Copernican Revolution, not the Tychonic Revolution.'