Tycho and Kepler

by Kitty Ferguson

  The contract discussion with Hoffmann never took place. Instead, on April 5 Kepler and Tycho met formally to discuss the matter of Kepler’s employment, and Jan Jesensky, the emperor’s physician, came from Prague to negotiate on Kepler’s behalf. The three men sat down together, and Tycho brought out his response, in writing, to Kepler’s demands. In return for the freedom to go to Prague, Tycho required a guarantee of silence about those aspects of the work at Benatky that Tycho preferred to keep secret. As for the request for Sundays and holidays off, that offended him, for he never asked his assistants to work on those days. He agreed to try to arrange separate housing for Kepler and his family, and he offered to pay the moving expenses, but he could not yet guarantee a salary. He had applied to the emperor and was waiting for a reply.

  It appears that Tycho came to the bargaining table in good faith, ready to try to find ways of meeting Kepler’s terms. He was fairly confident that there would eventually be some arrangement with the emperor, though he knew from prior experience the difficulty of actually collecting on such promises. Kepler, on the other hand, came to the bargaining table predisposed to be distrustful and argumentative. The meeting ended with angry words and no agreement. Later that day, at dinner, in the presence of the entire household, a frenzied Kepler, who had drunk too much wine, staged another outburst. This time, Tycho replied in kind. Kepler left Benatky the next day with Jesensky.

  Tycho’s equanimity following this episode was astounding, almost out of character, and perhaps stemmed only from the fact that Kepler had become so necessary for the realization of Tycho’s ambitions. However, Tycho’s response to others had always been more instinctive than reasoned, and in this instance both instinct and judgment must have told him that Kepler was not, either in respect to his talents or his character, an Ursus. Tycho refused to allow Kepler to destroy himself. He treated Kepler with patience such as he had never displayed except in matters involving those he most dearly loved in his own family. Moving ahead in the assurance that all would be well and that Kepler would come back, he informed Jesensky, before the carriage departed for Prague, that he would need a written apology from Kepler, and he sent a letter with Jesensky to Hoffmann, asking for his intercession and help in smoothing things out.

  The fact that Tycho did not react more strongly to his anger sent Kepler into an even worse rage. The next day he penned such a blistering, insulting letter18 to Tycho that Tycho did not even have anyone copy it for preservation, but sent it to Jesensky with a note saying he regretted ever having anything to do with Kepler. This time he had indeed been pushed too far. No one less than a king had ever gotten away with treating him this badly. The note may have mentioned Ursus, for Tycho requested that Jesensky “find out by a third or fourth19 hand whether Kepler is quietly endeavoring to provide Ursus too with some reproaches against me (for how shall I have confidence in him any more?).”

  Somehow—perhaps Hoffmann did help in the end—Kepler came to his senses, calmed down, and realized the enormity of what he had done, and he wrote an apology to Tycho20 that was as effusively abject as his former note had been vitriolic. Astonishingly, Tycho not only immediately forgave him but climbed into his carriage and drove into Prague (which he hated to do and avoided whenever possible) to bring Kepler back himself. Shortly after that, they came to agreement about Kepler’s terms of employment.

  Tycho’s attempts to get an imperial stipend for Kepler soon met with some success. The plan was that the emperor would summon Kepler officially to assist Tycho for two years. During that time, Kepler would continue to receive his salary as district mathematician in Graz and in addition would receive a salary half that large directly from the emperor. Though it seemed dubious whether Catholic Styria would allow its Protestant mathematician that much leeway, the hope was that since the assignment would come from the Catholic emperor of the Holy Roman Empire, of which Styria was a part, the Estates of Styria would feel sufficiently pressured to approve.

  Kepler, his prospects looking much brighter, settled down to work and began making plans to move his family to Benatky. In May, Tycho arranged for him to travel the first leg of the journey to Graz with the Danish nobleman Frederick Rosenkrantz,fn2 Tycho’s third cousin who had fled Denmark when it was discovered he had got a lady-in-waiting pregnant. Rosenkrantz had been captured and sentenced to be stripped of his nobility and have two fingers cut off. Fortunately for him, that sentence had been commuted to service in the campaign against the Turks, the enemy whose earlier threat Kepler had successfully predicted in his first official yearly horoscope as district mathematician in Graz, and Rosenkrantz was on his way to join the army.

  Tycho’s arrangement for Kepler to ride as far as Vienna in Rosenkrantz’s carriage may not have been entirely out of kindness: It was a good way to make sure Kepler got well beyond Prague without an opportunity to connect with Ursus.

  fn1 Gingerich and Voelkel have pointed out that Tycho, had he kept his observations strictly to himself, could have claimed whatever he pleased about his findings, whether true or not, and no other scholar had data to gainsay him.

  fn2 Kepler’s traveling companion was immortalized in Hamlet, and would four hundred years later come even more into the spotlight in Tom Stoppard’s Rosencrantz and Guildenstern Are Dead. William Shakespeare’s “Guildenstern” was in real life Knud Gyldenstierne, another cousin of Tycho’s. When the two kinsmen were in England on a diplomatic mission in 1592, they had made an impression on Shakespeare, although it must not have been a highly favorable one, judging by the way he portrayed them.

  18

  “LET ME NOT SEEM TO HAVE LIVED IN VAIN”

  1600–1601

  WITH THE THAWING of the shipping lanes, in that same eventful spring of 1600, Tycho decided that the time had come to bring all his instruments to Benatky. The castle and the new bays along the bluff were almost ready for them. Tycho had left the four largest on Hven, and more recently, in order not to arrive so weighted down in Prague, he had stored most of the others in Magdeburg. During a year and a half their release had become entangled in bureaucratic red tape that not even a letter from the emperor had cut. Tycho hit on the strategy of suggesting to the Magdeburg authorities that they could make a tidy profit for themselves by transporting the instruments to Prague and using the return journey to import Bohemian wine. The instruments were almost immediately on their way.

  Tycho had initially been much more worried about the four great instruments still on Hven, for he feared they would never be permitted to leave Denmark. The previous autumn, before Kepler arrived at Benatky, Tycho had sent his son for them and appealed for help to his brother Axel, now commander at Helsingborg. Longomontanus had left Rostock and traveled with young Tycho. The instruments did get out of Denmark and as far as Lübeck before winter weather made further transport impossible. With the spring thaw, they were on their way again through the mud and swollen rivers to Hamburg. Unaware that a bureaucratic delay there, similar to the one in Magdeburg, would halt them again, Tycho believed that before the summer was over he would have his new Uraniborg.

  The Golden Griffin (far left) as it appears today.

  It was not to be. The plague had retreated. The court returned to Prague, and on June 10 Rudolph summoned Tycho to begin astrological consultations on state decisions. Because that would often require going to the palace twice a day, Rudolph arranged for accommodations for Tycho, his family, and his assistants in a hostelry known as the Sign of the Golden Griffin, in the section of the city where the palace stood. Tycho was now in precisely the situation he had hoped to avoid by choosing a castle away from the city.

  Kepler’s high hopes that late spring also came to a dead end. Not long after his arrival back in Graz, the Styrian councillors refused the request that they release him to work in Prague while continuing to pay his salary. There was, they argued, no useful purpose to which astronomical work could be put, and they suggested he go instead to Italy, study medicine, and return to practice as a phy
sician. Since there could be no arrangement with Rudolph without the Graz salary, this decision ended Kepler’s plans to return to Benatky. A despondent Kepler had no choice but to search for other possibilities. He even approached Archduke Ferdinand, suggesting that Ferdinand might, like his cousin the emperor, wish to have his own personal mathematician.

  Ferdinand’s reply, though not specifically targeting Kepler, was worse than a rejection. On July 27 a notice appeared, and the news spread rapidly: At 6:00 A.M. on July 31, all citizens of Graz had to present themselves for examination of their faith. Anyone who was not Catholic could pledge to convert. Those refusing so to pledge would be required to leave Graz.

  Archduke Ferdinand himself was present with the commissioners as they sat at a large table in the middle of the church. It took three days for more than a thousand citizens to come to the table and be examined. Most were either already Catholic or agreed to conversion. When Kepler reached the table on August 2, he said he was a Lutheran, and he would not convert. His name was written down on the list of sixty-one banished citizens. He was given six weeks and three days to leave Graz for good.

  The Kepler who had so completely lost his equanimity the previous spring at Benatky accepted this disaster with a serenity that even he found astonishing. “I would not have thought that it is so sweet,”1 he wrote, “in companionship with some brothers, to suffer injury and indignity for the sake of religion, to abandon house, fields, friends and homeland. If it is this way with real martyrdom and with the surrender of life, and if the exultation is so much the greater, the greater the loss, then it is an easy matter also to die for faith.” Kepler sensed that he was being forced to go, albeit not willingly, along a path he was meant to follow.

  During this horrendous summer, when his family’s whole world was falling apart, Kepler nevertheless found it much easier to work than he had at Benatky. Barbara seems to have found the strength to leave her husband and his calculations undisturbed in spite of the frightening and heartrending upheaval in their lives.

  Kepler was trying to solve a problem having to do with optics that puzzled both Tycho and Mästlin. Tycho had recently observed a partial eclipse of the Sun by allowing the Sun’s light to pass through a pinhole onto a white screen, where it made an image of the eclipsed Sun. Measuring this image, Tycho had concluded that the Moon was not large enough to cover the Sun completely, and that therefore a total eclipse of the Sun was impossible. Yet all astronomers knew that there were many total eclipses on record.

  It seems that in spite of the lack of opportunities at Benatky for discussions, Tycho had spoken to Kepler about this problem and given him instructions on how to build a projection device for viewing an eclipse. Kepler constructed the device according to Tycho’s pattern and observed a partial eclipse from Graz on July 10. Tycho had been right; the Moon’s apparent diameter was smaller than the Sun’s. Kepler proceeded to give serious mathematical consideration to pinhole images and whether this method of observing an eclipse distorted the image of the Sun. He concluded that the accuracy of the observation depended on the size of the pinhole, and that no pinhole could ever be small enough for complete accuracy. Hence Tycho’s image of the Sun, distorted by the size of the pinhole he used, was slightly too large, and seemed incapable of ever being covered by the Moon. Before the summer was over, Kepler had defined the concept of “light rays” that still lies at the heart of geometrical optics. He wrote an essay about pinholes and light rays, and about his conclusions, and then set it aside when his personal difficulties became too pressing.

  As soon as Kepler had learned there was no possibility of drawing a salary from Graz while he worked at Benatky or in Prague, he had written to inform Tycho that the hoped-for arrangement with the emperor would not be possible. Tycho’s return letter came quickly: The failure of that arrangement must not matter, and he urged Kepler to come back, either with or without his family, “with confidence2 as rapidly as possible.”

  Though it was impossible to remain in Graz, Kepler had profound misgivings about putting his and his family’s future at Tycho’s mercy. Without a regular salary, living from day to day on handouts, even if Tycho were the most well-meaning and generous patron, was too precarious and demeaning an existence. Kepler wrote to Mästlin, asking whether some “little professorship”3 might not be found for him at Tübingen. Kepler knew Mästlin’s reply could not reach him before he left Graz, so he told Mästlin to address it to him in Linz. Linz was on the way to Prague, and Kepler’s plan was for Barbara and his stepdaughter Regina to travel that far with him and wait there while he went on alone to talk to Tycho.

  It was two weeks beyond the deadline when, on September 30, Kepler, Barbara, and ten-year-old Regina left the city. They loaded two wagons with as many household goods and possessions as they could fit in and drove away from the comfortable home in the Stempfergasse where they had lived for three years. They had no real destination, and for Barbara the wrench was horrendous. All she had ever known or cared about, all her friends and extended family, all her quite considerable property, were here in Styria. Because of her husband’s and her own religious convictions, they were leaving all that behind for an uncertain future among strangers. Barbara had an almost irrational fear of poverty, and there was no promise of a paying job ahead for her husband. It was unlikely they would ever be able to recover the value of her property.

  On the journey north to Linz, they kept the hope alive that a letter from Mästlin would be waiting for them, but when they arrived in Linz, there was no letter. Kepler changed his mind about leaving Barbara and Regina alone, feeling it was better they all stay together, in case one of them became ill. They left the household goods behind in Linz to follow them later either to Prague or Tübingen—for there might yet be a letter from Mästlin—and continued toward Prague.

  Kepler knew that now he was absolutely at Tycho’s mercy—and not he alone but Barbara and Regina as well. He made one last attempt to bluff4 his way to a better job arrangement with Tycho, writing him in advance of their arrival, saying that because he had at one time received a scholarship from the duke of Württemberg, it was necessary that he pay his respects to the duke before settling elsewhere. While in Württemberg, he wrote, he would find out whether the duke would recommend him to another university, perhaps Wittenberg, Jena, or Leipzig, for his teachers at Tübingen had given him hope that the duke’s connection with the university would be a great advantage—an extreme exaggeration on Kepler’s part, if not an outright lie. His letter continued with the promise that if Tycho were to offer him an attractive position, he would give that offer first consideration. He named a deadline for the offer, four weeks at the latest. It was a feeble try, but it was the best Kepler could do.

  Kepler’s serenity had evaporated. To make matters worse, he developed a high fever on the journey from Linz to Prague. When the exhausted, depressed family arrived in the city, on October 19, 1600, it was the good Hoffmann who took them in, not Tycho. Although Kepler’s fever was stubborn and would recur intermittently throughout the winter and spring of 1601, he was healthy enough to return to work for Tycho in late October. There had been no word from Mästlin, and no other possibilities had arisen. As Kepler would write, “God let me be bound with Tycho5 through an unalterable fate and did not let me be separated from him by the most oppressive hardships.”

  Kepler’s fever was accompanied by a cough, and he thought he had contracted tuberculosis. Barbara also was ill and desperately unhappy, lonely in a foreign city, watching the little money they had disappear. She was not accustomed to enormous wealth, but she had always enjoyed a comfortable upper-middle-class standard of living. In Prague she would be reduced to maintaining their little family in a state of penury with nothing better in sight. The move had cost 120 gulden. Kepler’s annual salary in Graz had been only 200 gulden. Even if his income had remained the same, everything was much more expensive in Prague, and now Kepler had no income.

  Tycho made no “attractive
offer” for Kepler to give “first consideration,” and the four-week deadline passed. However, Tycho was trying to secure a salary for Kepler from the emperor. Rudolph, Tycho had reported, had given “a gracious nod,” but both he and Kepler knew by now that even if that nod actually set the mechanism in motion by which a salary might eventually appear, a man and his family could starve waiting. For the time being, the Keplers had no choice but to depend on Tycho for everything. Tycho, who was already paying the Müller family’s expenses out of his own pocket, because money for them from the emperor was overdue, now dug deeper and paid for the Keplers as well.

  By the time the ailing Kepler was well enough to rejoin Tycho, Tycho had complained about cramped quarters at the Sign of the Golden Griffin, and the emperor had provided a private residence, not much larger. Into this house Tycho nevertheless managed to squeeze Kepler, Barbara, and Regina.

  Eventually there must have been a salary agreement between Tycho and Kepler. The only record of it appeared when Tycho’s daughter Elisabeth and Tengnagel were making plans to wed in the summer of 1601, and Tycho braced himself to pay for a lavish wedding. He told Kepler he would have to dole out Kepler’s twenty-daler stipend in ten- and six-daler installments, because he did not have enough ready cash to do otherwise.