Kepler's Witch (17 page)

As he was leaving for Prague, however, Kepler calmed himself and showed some remorse for his earlier comments. He apologized to Tycho. He had always had difficulty controlling his feelings in the middle of an argument, as he well knew, and at times he behaved just like a mad dog. This temper of his had plagued him all his life, in Maulbronn and in Tübingen, and now even with Tycho. But Kepler's apology wasn't quite enough for the old Dane. His noble vanity had been pricked, and he whispered into Jessenius's ear that he wanted Kepler to give him an apology in writing. He asked Jessenius to speak to Kepler on the way back to Prague and set the young man straight about his temper. Jessenius must have thought that Kepler was largely at fault, for he agreed, and on the way back to the city he remonstrated with the young man about his bad behavior, telling him that a learned man should not be so quick to anger and that a gentleman should always control his feelings. This didn't help—Kepler took it all the wrong way. Perhaps he saw more deeply into Jessenius's words than Jessenius wanted him to. Perhaps he saw behind those words their true meaning—that a servant, no matter how brilliant, should always be docile before his master.

The dam of Kepler's emotions finally burst, and after his return to Prague he wrote Tycho a letter, unloading every spoonful of his anger. Ego upon ego upon ego—Tycho responded in kind, and on April 8 he wrote a
letter to Jessenius complaining about Kepler's further bad behavior. He told Jessenius that he no longer wanted to deal with a man such as Kepler, who talked so impudently and with such little balance. In the future, he wanted nothing to do with Kepler and wished he had never met him. He said that Kepler could not use the excuse that he was drunk on Tycho's wine, for Kepler rarely drank to excess; nor could he use the excuse that he had been ignored by Tycho, for he had not been, so he must have been angered by something that was said at the dinner table.

Then suddenly, like a passing thunderstorm, the argument ended. Kepler, who could always see the other side of every argument in time, suddenly saw Tycho's. One minute he was the victim, and the next he was the victimizer. He beat his breast and was thoroughly ashamed of himself. Like a deflating balloon, his anger collapsed inward, and all he could see were the blessings that had come his way since he met Tycho Brahe, and as he counted them, with each new blessing he reproached himself once more. Kepler fell into a depression knowing full well that his anger had gotten the best of him. He felt as if God had abandoned him and prayed fervently for forgiveness and reconciliation. When Tycho came to Prague sometime later, Kepler wrote him a letter begging his forgiveness and accusing himself of gross impropriety. In his sudden burst of humility, he offered his service to Tycho in whatever manner would satisfy him, and he promised to prove to Tycho that he had become a new man. Suddenly Tycho was satisfied, because he could see that at least to some degree Kepler had been right in his complaints. Moreover, he needed Kepler to finish the work. Not that he would have admitted it, for his pride was too massive a thing, but he was secretly glad that Kepler had apologized because it gave him an opportunity to be generous.

Finally, Tycho and Kepler settled the terms of their relationship. Tycho promised to ask the emperor to summon Kepler to Bohemia for two years to help him with the publication of his work. They would have to get permission from the representatives in Graz for this, for they needed the school councilors' agreement that they would pay Kepler his salary during this time. Tycho, or the emperor, would add 100 gulden to Kepler's salary.
On his part, Kepler promised that he would focus on the glory of God first, and then on the glory of Tycho Brahe, and lastly on his own.

Soon after, Tycho spoke with Corraducius, the emperor's vice counselor and asked him to request that the emperor intercede with his cousin Archduke Ferdinand and the representatives in Styria. Corraducius agreed. Moreover, whatever moving expenses Kepler incurred bringing his family from Graz Tycho promised to pay. Suddenly, everything was moving along swimmingly. Kepler was happy with Tycho, and Tycho with Kepler. Only one dark cloud remained in their relationship, though Kepler likely knew nothing about it. If all worked out as planned and Kepler returned with his family to Prague, Tycho decided to keep Kepler close by, either at Benatky Castle or in one of the surrounding towns. He didn't want him living in Prague close to the imperial court, where he could make other contacts and build a political base for himself. Most specifically, he wanted to keep Kepler away from Ursus, for Tycho was even then bringing a lawsuit against him. That summer, however, the problem evaporated. At the request of the emperor, Tycho moved from Benatky Castle into Prague, for the emperor too liked to keep his mathematician close by. Then in August of that year, Ursus died.

Kepler set out for Graz on June 1 with a solid letter of recommendation from Tycho in his pocket, accompanied by a relative of Tycho Brahe's, Friedrich Rosenkrantz, whom Shakespeare had memorialized in
Hamlet.
The letter of recommendation, filled with golden praise, was meant to sway the school councilors, to impress them with Tycho's fame and daunt them with his imperial connections. It had little effect, though. The entire city of Graz was in turmoil over the measures of the Counter-Reformation, and the councilors at the Lutheran school had no time for a famous mathematician.

Instead of granting their permission for him to return to Prague, they ordered him to abandon theoretical astronomy altogether and to take up the study of medicine. Who cared about the heavens, when events on earth were so dire? Kepler, they said, needed to compose his mind and to dedicate himself to the common good. They ordered him to leave for Italy
in the fall and to prepare himself for a new profession as a physician. His family could do without him for a time—he proved that by his long stay in Prague. Better for them and for everyone if Kepler made better use of his skills.

What was Kepler to do? His entire deal with Tycho depended upon the agreement of the school councilors. He needed them to continue to pay his salary, but now that seemed impossible. Should he go to Italy as the councilors wanted? He could not do without his salary from the Lutheran school, for money promised by the emperor was more speculative than astronomy. Even Tycho had a hard time getting money out of the emperor. For a time Kepler considered taking their advice, or rather following their order, because as a practiced astrologer, his study was not that far away from medicine. Most good astrologers compounded their own cures, which required a good deal of understanding of the language of the heavens. A person's health depended upon the good favor of the stars, and the compounding of medicines was done under the aspects of specific planets. Both Copernicus and Tycho were physicians as well as astrologers and often prepared their own cures, a practice that finally killed Tycho from an overdose of mercury.

But Kepler was a purist, and although the healing of the sick was a good thing, stalking the mind of God was far better. To give up his speculations on the nature of the universe would be to deny his very self. Everything seemed to be in his grasp—Tycho's observations were available to him and a position was waiting for him, a position that included the approval and protection of the emperor. How could he give up the study he had spent his life working for? He contacted his friend Herwart von Hohenberg, the Bavarian chancellor, to inquire about the possibility of working for Archduke Ferdinand as his ducal mathematician, but the chancellor could see the complications in his proposal, given Ferdinand's character, and advised Kepler to trust in Tycho, regardless of their previous agreement.

Undaunted, Kepler did his best to curry favor of the archduke. Shortly after his return to Graz, he wrote an astronomical essay on the unexpected lunar eclipse that would occur on July 10 of that year. He calculated the
eclipse and included some especially detailed arguments about the theory of the motion of the moon. Along the way, he developed some new ideas and insights that would serve him well in the writing of his
Astronomia Nova
. Up until Kepler's day, astronomers held to the Aristotelian notion that all the orbits of the planets had to be perfectly circular. This had to be so, according to Aristotle, because the heavens were perfect and all movements in it had likewise to be perfect. The circle was the perfect shape, and therefore the planets had to move in perfect circles.

Everyone accepted this, even Kepler, for it seemed as if it ought to be true. The problem was that the theory did not explain the data and, instead, spawned theories that were ever more complex. All of them were built out of perfect circles, but offered little or no explanation about why the planets moved in this way. To make sense of his own data, Tycho had to create ever newer and more complicated levels of circles in order to explain the motion of the moon and still keep Aristotle's assumptions about the heavens. Kepler had opposed Tycho in this regard, feeling that he was on the wrong track, that the system had to be simpler than Tycho envisioned it and that Tycho's systems were too complicated to defend. He believed this, because he believed that “simplicity is more in agreement with nature.” To solve the problem, he at first sided with those who believed that the motion of the moon was nonuniform, that the secret of this nonuniform motion could be found in the earth itself, and that whatever it was that caused the motion faded with distance. This little insight was a second glimmer of the theory that would eventually become Newton's law of gravitation. Kepler believed that there was a force in the earth that caused the moon to move; as the moon grew farther from the earth, the force grew weaker, and as the moon grew closer to the earth, the force grew stronger. Although it lacked Newton's mathematical schema and his subtlety, it was a groundbreaking idea, one that Newton could build on to fashion the inverse-square law of gravitation.

The archduke received Kepler's essay kindly and in return presented him with a small gift, but he offered no permanent employment. He had other things on his mind. Meanwhile, Kepler happily went back to his observations and developed a new instrument to observe the lunar eclipse of
July 10. Standing in the marketplace in Graz with his new instrument, he watched the eclipse, making careful observations at each stage. By July 22, while in the midst of his calculations, he realized the solution to one of Tycho's nagging problems. He realized that the reason that the lunar disk shrank at the time of solar eclipses was optical rather than astronomical. Then a short time later, he formulated the laws that govern light as it goes into a pinhole camera, a camera obscura.

In the midst of this happy moment, however, the hammer fell once again. Everything that Kepler had feared, the final gathering of the Counter-Reformation, occurred on July 27, 1600. The archduke's final decree on the Protestant problem was proclaimed in the marketplace and on the street corners, then published on church doors throughout the city. All citizens, burghers, and all inhabitants of the city of Graz, including all doctors, preachers, and nobles—except those members of the old nobility—were commanded to gather in the church on July 31 at six o'clock in the morning to be examined about their faith. This was the day that Kepler had long feared, for there was no more hiding, no more dissembling, and no more escape. The archduke presented Kepler with a simple choice—either his home and his career or his faith. There was no doubt in Kepler's mind about which way he would choose—he was a Lutheran and no prince of this earth could take that from him. Jobst Müller had determined early that he had too much to lose in his investments and that his lands were too precious to him, so if the archduke demanded it, he would turn Catholic. So did many of the men and women of his family. His granddaughter, the oldest daughter of Jobst's son Michael, eventually became a Dominican nun.

Kepler gathered with all the others early in the morning on a hot summer day, knowing full well that his fate had already been decided. The archduke himself, with a full company of guards, nobles, and other retainers gathered around him, sat in state in the cathedral. Bishop Martin Brenner of Seckau preached a sermon, and then the Counter-Reformation commissioners took their places at a long table set up in the middle of the church. They pulled up a long list of the city rolls and called the names one by one. As each man stood, the commissioners questioned him about
his faith. Was he a Catholic? If not, would he ever become a Catholic? Would he swear allegiance to Rome and to the pope? If so, he could remain in Graz. If not, if he stubbornly held to the Lutheran heresy, then he would have to leave and take with him the displeasure of his liege lord, Archduke Ferdinand. Those who would not go to confession and take Communion in the Catholic church would be banished and would have to leave the city almost immediately, after paying 10 percent of all their assets to the archduke.

On August 2, they called Kepler's name, and he stood, ready, in front of a thousand witnesses, and moved to his place in front of the long table with the archduke looking at him from his throne on the dais, while the commissioners posed the questions to him one by one. Are you Catholic? He was not. Are you willing to become a Catholic, to go to confession and to take Communion? He was not. He was the fifteenth name called that day; the register listed him as Hans Kepler with a terse note beside his name saying that he should quit the land inside of six weeks and three days. Ten days later, on August 12, the archduke discharged him from his position as the district mathematician for Upper Austria. Still, the archduke respected him in spite of his Lutheran ways. Kepler petitioned to Ferdinand and the
Stände
to give him a written letter of reference and to allow him a half-year's salary as severance pay. The
Stände
agreed and paid him on August 30. Then, on September 4, the councilors at the Lutheran school gave him a second letter of recommendation, stating that he was a highly praised professor, that they were sorry to see him go, and that they gave him their full recommendation most heartily.