Kepler's Witch Read online

  That summer of 1599, in the midst of all his astronomical work, was when his little daughter Susanna suddenly died and Kepler nearly fell into despair. Oddly enough, in the midst of his sadness, perhaps because of his sadness, he began researching a new book, a book that would eventually lead to his great work on world harmony, the Harmonice Mundi. This was perhaps more revealing of his personality than anything else. His world was collapsing about him. He was about to be chased out of his home and lose his career. His little son had died and now his daughter, of the same illness. His wife’s family gnawed at him over everything, and there he was in his study thinking about a book on the harmony of the universe.

  His faith told him that God does nothing without a plan and that God’s wisdom and goodness made the whole world beautiful. Buried in the heart of the world is the image of the Creator, a copy of the divine mind. God gave human beings the power to reason, the most godlike characteristic of all, and out of that rational power would come the ability to see God’s own plan in action. Copernicus had seen it, that marvelous harmony, that order to things, like the order of music that heals the soul and harrows sin from the world. The sensation of joy that different tones played in orderly succession or played together in chords brings to the human soul speaks of a perfect world, higher than this earth where, like little Susanna, things are born doomed to die. But harmony speaks to the soul of the transcendent world where God sits enthroned above the stars and listens to the music they make. The pleasure people feel in music partakes in this and encompasses each whole person in the place where the intellect joins with the senses, just as mathematics joins with sound. Major thirds, minor thirds, major fourths, major fifths, each with its own unique feel. So what is it about these proportions that stirs the human soul so? Where does the joy come from?

  Kepler, following Plato, believed that music, and the simple mathematical relations that music embodies, reveals a cosmic harmony. This was not a rough Pythagorean number mysticism, by any means, but an icon of the mind of God embedded in the human soul. “God wanted to make us recognize him, when He created us after His image, so that we should share in His own thoughts. For what is implanted in the mind of man other than numbers and magnitudes?”19 As he later wrote in his defense of Galileo, his Dissertatio cum Nuncio Sidereo: “Geometry is one and eternal,” a reflection out of the mind of God. That humankind shares in it is one of the reasons to call the human being an image of God.20

  For Kepler, these world-forming harmonies are ubiquitous, for they make up the first pattern of the universe. He found them equally in the sound of music and in the velocities of the planets, in the pleasure of the human senses and the movements of the heavens—the “music of the spheres” in a new package. “Give air to the heavens, and truly and really there will be music,” he wrote to Herwart von Hohenberg.21 And he was certain of it. The harmonies, like the Platonic solids, were the key to the planetary orbits. They had to be. The idea was too beautiful for them not to be. Still, he needed more accurate data to prove it, and for that he needed Tycho Brahe.

  In Kepler’s study, the candle burned long into the night while he scribbled out calculation after calculation, looking for the harmony, the perfection of the universe. Outside his study, however, the world was growing more dangerous by the day. The Counter-Reformation was heating up in little Graz. The archduke was unsatisfied with merely banishing the preachers and teachers of the Lutheran community, for he had sworn to bring his part of Austria back to the true faith, under obedience to Rome, and that meant everybody. He announced a new set of regulations, one after the other, this time aimed at the people themselves. Many continued to attend services and to receive the sacraments at the castles of the nearby Protestant estates, and for a time the archduke did not pursue them. Only the minister was liable to banishment if caught. But then, suddenly, the rules changed, and the archduke promised to punish anyone caught attending Protestant services. Moreover, Ferdinand demanded that all children in the region be baptized in the Catholic faith and that all engaged couples be married before a Catholic priest. Soon the archduke ordered all Protestant clergymen—Lutherans, Calvinists, and Anabaptists—out of Styria. No exceptions. No excuses. He made it a crime, punishable by confiscation of property and even prison, to offer them asylum in any way. Jesuit schools alone remained open, and anyone who wanted an education went there.

  Anyone who sang Protestant hymns or read Protestant homilies, read Luther’s Bible or recited Luther’s prayers could be fined or banished, for these were now works of heresy. The archduke set guards around the city to check wagons and mules and bags of personal belongings and to watch for forbidden books. Lutherans complained to him, but he pointed out how Protestants had forced Catholics to convert in other parts of Germany, in Saxony, in Württemberg, and in the Palatinate, and that he was merely exercising his rights under the Peace of Augsburg. Little Graz buzzed and hummed with rebellion. Riots popped up in parts of the city, and there were finger-pointing arguments on every street corner. Rumors flowed from street to street; soon, they said, no Lutheran could live in the city, and those who tried to emigrate would no longer be able to sell their possessions and would have to leave penniless. And they were right, or nearly so.

  Kepler felt this oppression as much as anyone, as his position at the school became increasingly tenuous. The school councilors were growing impatient with him. What was the point of a speculator like Kepler when the Lutherans were at war? Kepler wrote to Mästlin in distress to ask for advice and for some “little professorship,” but his old teacher had nothing for him. Tübingen would not have him, even then, even with his growing fame, even in his great distress. The faculty was all too chummy, all too connected by blood or marriage. Their world was too insular, too narrow, too orthodox for them to accept someone like Kepler. Their little ship was at war, and Kepler was a loose cannon.

  Kepler, however, had one last card to play—Tycho Brahe. The Danish astronomer had come to Prague in June 1599. After Tycho had lost favor with his own king in Denmark, the emperor Rudolf replaced Reimarus Ursus with Tycho, at a salary of 3,000 gulden a year, bringing him first to Prague and then later, because the city had become too noisy, to Benatky Castle, about twenty-two miles northeast of the city. He and Kepler had patched up their differences over Ursus, more or less, and Tycho had in a friendly letter invited Kepler to visit him, so Kepler decided to make the journey, even though he had no money and no way to get there.

  Then, in Kepler’s mind, God opened the way. Right after the first of the year in 1600, a friend of Kepler’s, Johann Friedrich Hoffmann, Baron of Grünbüchel and Strechau, was returning to Prague after meeting with the Styrian Stände. As wealthy men do, he had his own coach and four and the best of everything. He understood Kepler’s situation in Graz and, though the two men were in vastly different stations in life, he respected Kepler’s talent. The two men shared a love of astronomy, and the baron had taken Kepler’s case to heart, offering him advice and help along with a personal introduction to Tycho Brahe and a ride to Prague. That December, Tycho had repeated his invitation to Kepler, saying that he hoped Kepler would come to Prague to pursue joint astronomical study and not just because he had nowhere else to go. Tycho stood ready, as he said in his letter, to aid and advise Kepler in whatever way he could. Oddly enough, the letter did not arrive in Graz before Kepler had already left for Prague, traveling with the baron. He had left trusting in the baron’s assistance and in the generosity of Tycho’s earlier invitation. The journey was not an easy one in the middle of winter, even in the best of times, even with the best of equipment. By modern standards, and even by ancient Roman standards, the roads were rough and unpaved, sometimes narrowing to a few ruts.

  Eventually, they arrived in Prague, and Kepler stayed with Baron Hoffmann for a few days until Kepler could send word to Tycho out at Benatky Castle, who was thrilled at Kepler’s arrival. He sent a return note, calling him not so much a guest, but a friend and companion in the observation of t
he heavens. A few days later, on January 4, Kepler rode out to the castle with one of Tycho’s sons and one of his assistants. The weather was often cold around Prague in January, with mists rising from the river and a cold drizzling rain falling from a low, gray sky.

  No two men could have been more different. Tycho was noble, used to wealth and privilege, often suspicious of others, and fearful that someone would steal his discoveries from him, cadge his fame in the night. Also a Lutheran, he had not received Communion for eighteen years, though he believed in the “new way” and often let theology guide his mind. Kepler on the other hand was open, sometimes to the point of naïveté. He could be suspicious, stingy, and irascible, but he could not imagine brooding over his ideas and discoveries as Tycho had done. His Lutheranism was his heart; his belief in God guided his every action. Moreover, Tycho was the consummate extrovert, constantly surrounded by family, friends, and servants. He lived in a great Danish-style hall full of noise and enjoyed endless meals spiced with conversations on science, philosophy, religion, and the news of the day. Kepler, on the other hand, preferred his own company and the quiet of his study, where he recalculated his figures and worked out his ideas.

  Of the assistants who worked and lived in Tycho’s household, two would affect Kepler’s later life. The first was Christen Sörensen Longberg, who had latinized his name to Longomontanus. Another suspicious man, he had been with Tycho for eight years and had worked with him in Denmark, at Uraniborg on the island of Hveen, and he jealously guarded his own position with the master. The other was Franz Gansneb Tengnagel von Camp, a Westphalian nobleman who was far more interested in Tycho’s daughter than in Tycho’s astronomy. Because he was an aristocrat and because he was about to join Tycho’s family, he was arrogant and treated the other assistants as if they were servants. Years later, he would give Kepler no end of trouble over control of the Rudolphine Tables. Kepler, for his own part, must have seemed threatening to the other assistants because he had brought to Prague a reputation of his own, separate from Tycho’s, and although his fortunes had fallen because of the Counter-Reformation, he had more independent standing as an astronomer than anyone else in the household except Tycho.

  What started as a visit soon became a collaboration. Most of all, Kepler wanted to examine Tycho’s observational data so he could prove his theory in the Mysterium Cosmographicum, but Tycho wasn’t about to hand over his observations to a relative stranger, especially anyone with Kepler’s talent, talent enough to misuse them for his own purposes. Kepler, therefore, was kept far from Tycho’s observations. Unfortunately, observing was something Kepler had a hard time doing for himself, because, like Beethoven two centuries later, whose deafness kept him from hearing his own music, Kepler’s childhood smallpox had clouded his eyesight.

  But his mind was active, and he could easily see the richness of the scientific meal available at Tycho’s house from the crumbs that Tycho let fall at the dinner table. At one meal, Tycho happened to mention the apogee of one of the planets, the next day he mentioned the nodes of another, and Kepler began putting things together. Within a short time, Kepler had already fashioned a bold new theory of the orbit of Mars. Seeing this, Tycho was impressed, and he opened some more of his data to Kepler, who saw at once that Tycho had the best data around. He also had the best setup, with the most assistants and the best equipment. All he lacked was someone with the ability to take that data and construct a general theory out of the parts. “Now old age steals upon him, weakening his intellect and other faculties or, after a few years will so weaken them that it will be difficult for him to accomplish everything alone.”22

  After a short time, Kepler took on a new project. Longomontanus had been working on the orbit of Mars, and though he had been able to represent the orbit in terms of latitude, he was unable to do so in terms of longitude. Kepler asked if he could try, and Tycho agreed, assigning Longomontanus the problem of the moon. Longomontanus was not happy, and said so, but he admitted that he could go no further and surrendered. Quickly the new work absorbed Kepler, and he lost himself in it for a time, making one calculation after another, eating up the days and nights, until he suddenly noticed that he was staying in Prague longer than he had intended. He knew that if he wanted to make use of Tycho’s observations, he would have to stay on as long as one or two years. But to do this he would have to resign his position in Graz, and though things were shaky there, he still had a job and a family to attend to. To keep his position, he would have to receive the school councilors’ permission to stay in Prague for a while, and under the circumstances this would be unlikely, because they wanted to get rid of him anyway. He wondered if he should get Tycho’s support, or if Tycho could ask the emperor for his intervention.

  Whatever happened, Kepler did not want to be seen as driven out of Graz by poverty and misfortune—the shame of that would have been too great to bear. Besides, even if he immigrated to Prague, how could he survive there? How could he support his family there? Everything was far more expensive in the imperial capital than it was in little Graz, and Barbara’s lifestyle would be seriously curtailed. Moreover, what would be the nature of his new position with Tycho Brahe? Would he be an assistant like all the others? But surely he was more than that, for he brought to the enterprise a reputation and a work of his own. He brought the ability to build a general theory and support it by mathematics. Not even Tycho could do that as well. In many ways, Tycho needed him as much as he needed Tycho. Tycho was nearly fifty-seven, and his time was passing quickly. He did not possess Kepler’s theoretical talent, and he could not make use of his own data to the degree that Kepler could. Tycho must have seen this himself, at least in some unconscious way, or he would not have welcomed Kepler with such eagerness. On the other hand, Tycho was still very suspicious of strangers, and, after all, this young man had given praise to that pig herder, Ursus.

  Meanwhile, Kepler sat down with a few of his friends and wrote out a long memorandum detailing all of the things he would need if he were to stay and collaborate with Tycho. This habit was a byproduct of his tidy mathematical mind, and whenever he had a serious question to ponder, he would write it all out, pros and cons, so he could see it in front of him. This habit got him into an awful bit of trouble, and more than once. Kepler wrote that he would need a place to stay, one that fit not only his needs, but his wife’s needs. He would need 50 gulden four times a year if he were to survive and raise his family. Moreover, he would need Tycho’s help in obtaining a salary from the emperor. But most important, he would need independence, a chance to work without Tycho looking over his shoulder, as if Tycho were the master and Kepler were the apprentice. Undoubtedly, for a young man with only one book and a career that was just beginning, as talented as he was, this memorandum would have seemed cheeky, though it was never meant for anyone to see. Kepler wrote these things down to clear his mind and as an aid for discussion.

  At Longomontanus’s suggestion, however, Kepler showed the memorandum to Johannes Jessenius, a doctor of medicine teaching at Wittenberg University and a longtime friend of Tycho’s. Jessenius was friendly with Kepler as well and agreed to act as a go-between, further agreeing to keep Kepler’s draft memorandum a secret and not to show it to Tycho. Somehow, however, whether by betrayal or by accident, the draft ended up in Tycho’s hands. One can only imagine how hurt the old Dane must have been. Here was this young man coming to him on the bare edge of poverty, about to be thrown out of Graz by the Counter-Reformation, and he was dictating terms. Tycho was a proud man, and though he was generally fair with others, he expected them to be fair with him, that and the deference owed to the nobility.

  On April 5, Wednesday of Easter week, Tycho and Kepler’s relationship began to fall apart. Jessenius was quietly presiding over a negotiation between them about the nature of Kepler’s position within Tycho’s organization, when somehow the conversation took a nasty turn. Hurt feelings bubbled up like hot mud, and Kepler, always quick to anger, at some point stopped listeni
ng. Tycho tried to take some time so that he could write down his own remarks and then have Jessenius certify them, but Kepler brusquely announced that he wanted to return to Prague the next day. Tycho tried to calm him and asked him to stay a few more days at Benatky Castle, explaining that he had hopes for Kepler’s employment by the emperor and that he wanted them to wait for word from the imperial court. But Kepler, his nose now thoroughly out of joint, wouldn’t have it and decided to leave the next day, April 6, with Jessenius. From there, things just went from bad to worse, as two oversized egos batted against one another like mythical frost giants throwing stones.

  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.