Kepler's Witch (27 page)

On his return to Prague, Kepler fell into another depression. The city that had been his intellectual sanctuary for ten years was falling into chaos. His reception at his home university was less than warm, and he felt as if a long winter had settled on his soul. For a time, he stopped sending out feelers for a new position, though he knew that some of his important friends in the Estates of Upper Austria were trying to make room for him there as district mathematician and a teacher in the Protestant
school. Instead, his depression dragged him down and froze his brain. He stopped working.

Then a wonderful thing happened, setting fire to Kepler once again. Galileo Galilei down in Padua had taken the newly invented
perspicullum,
or telescope, and during the winter of 1609–10 had applied it to the heavens. By itself, this was no great thing, since several other astronomers around Europe had been thinking along the same lines. And his telescope was not spectacular; it had little more power than a modern pair of binoculars. However, somehow Galileo knew where to look and what to look for. One discovery led to another. He found strange bodies near the planet Jupiter, bodies that no one had ever seen before! Not knowing what these were precisely, he named them the Medician Stars, after his patron the Grand Duke of Tuscany. Then, he turned his telescope to the seven-starred constellation of Pleiades and counted at least forty stars there, thirty-three more than anyone else had yet seen. He found that the planet Venus passed through phases, like the moon. He also found that the Milky Way, that fuzzy band of light stretching across the sky, was actually made of tiny individual stars. Galileo, as careful an observer as Tycho Brahe had ever been, marked all of these discoveries down in his notebook. He invited famous and important men to peek through his telescope to confirm his great discoveries by their own authority.

Kepler first heard about this when, on a cool day in March 1610, his friend and relative Johannes Mathäus Wackher von Wackenfels, the imperial adviser, stopped by Kepler's house and called him out to his carriage. There Kepler stood on the street while the two men discussed the news. Wackher told Kepler that he had received a report that Galileo had used the new telescope and had found four new bodies near the planet Jupiter, bodies no one had ever seen before. Wackher agreed with Giordano Bruno that, if the report were true, the stars could all be suns like our own sun and that the number of the stars would be infinite, existing in an infinite space. He thought that these bodies of Galileo's must be stars not yet discovered. Kepler, however, disagreed with Bruno, for he could not believe in an infinite space and told Wackher that these new bodies may be moons orbiting Jupiter, just as our own moon orbits earth.

Needless to say, Galileo's discoveries created quite a stir all over Europe. Galileo visited the great astronomer and mathematician Giovanni Antonio Magini in Bologna and set up his telescope in the garden so that Magini and his followers could peek through, but no one saw much of anything. Astronomers from both Catholic and Protestant camps shouted objections, some based on preconceived Aristotelian beliefs and some based on Scripture. Martin Horky, an acquaintance of Kepler's and the son of a Bohemian Protestant pastor, was a partisan of Magini, who kept a low profile himself, but encouraged men such as Horky, who had also been there to look through the glass, to write against Galileo. Horky published a short tract called
Peregrinatio Contra Nuncium Sídereum,
or
The Sojourn Against the Starry Messenger
. In his tract, Horky claimed that Galileo's reported discoveries were mere fables, mere fairy tales, that the bodies Galileo had seen around the planet Jupiter were only reflections in the glass, and that talk of the Milky Way being resolved into individual stars was a story as old as civilization. Father Scheiner, a Jesuit who would debate Galileo over the question of sunspots and would come off the worse for it, also raised objections.

Suddenly Galileo was at the center of a firestorm. Unlike Kepler, Galileo had many enemies. While Kepler was a peacemaker, Galileo was a controversialist. Like Tycho Brahe, he protected his reputation by maintaining constant vigilance against those who might wish to diminish his glory, even if it meant making enemies. Galileo was an arrogant man who not only knew he was right, even when he wasn't, as in the controversy over his explanation of the tides, but who made sure you knew it as well. This was a trait that would eventually get him into a sea of trouble with Pope Urban VIII Barberini, who had been told by Galileo's enemies that Simplicio, the fool in his
Dialogue on Two World Systems,
was spouting the philosophy of the pope himself. This did not make the pope happy, and when the pope isn't happy, no one at the Vatican is happy either. Including the Inquisition. Especially the Inquisition.

Kepler waited anxiously for Galileo's full report, which came to him on May 8, barely a month after he had first heard the news. Galileo's short work the
Siderius Nuncius,
or
The Starry Messenger,
detailed his discoveries
about the Medician Stars, which he had sent to Kepler by way of the Tuscan ambassador, Julian de' Medici, along with a request for Kepler's reaction. This was a one-way bargain, however, because Kepler had been waiting to hear from Galileo about his own
Astronomia Nova
for some time, and Galileo, forever haughty, had kept silent. Over the next few months and even years, Galileo did not show much heart in his relationship with Kepler, probably because the imperial mathematician was his only real competition. Perhaps the difference may also have been between a theoretician and a practitioner. Galileo believed that one had to go out and look for oneself, a true empiricist, and yet astronomy has always had need of its theoreticians who grab raw data and make universes out of it. Moreover, Kepler never quite managed to keep his metaphysical and aesthetic speculations out of his astronomical work. And the fact that he was also a Lutheran might have been a factor as well, a source of prejudice for Galileo, the pious Catholic. Still, the temper of the times affects even men of science.

No doubt with all the voices rising up against him Galileo needed the imperial mathematician's support, and he was not disappointed. Kepler was alive again; his imagination, his sharp reason, his love of learning had quickly thawed. He would have written to Galileo no matter what, for the love of God and for his own wonder about the universe. “Who could be silent before the knowledge of such great things?” asked Kepler in his response, titled
Dissertatio cum Nuncio Sidereo,
or
Conversation with the Starry Messenger.
²
“Who would not be overflowing with the riches of God's everlasting love?” It took Kepler only eleven days to write his response, just in time to send it back to Italy with the courier from the Tuscan ambassador.

Kepler's little book was a voice of quiet reason in a room full of shouting. Too many of Galileo's contemporaries had been stung by his wit or been treated to his hauteur, as if he were the only one with any brains on the entire continent of Europe. The Aristotelians branded him a charlatan, a flimflam artist with a couple of glass lenses. The Jesuits fretted about the appearances. Wasn't astronomy about accounting for the appearances? And yet Galileo claims to have found something new, to have found that
the moon was a rough body just like the earth! He claims that it has mountains on it, and valleys as well! Ridiculous, when everyone knows that the moon is a perfectly smooth body composed of the fifth element,
quinta essentia,
or quintessence. People have known this from the time of the Stagirite, Aristotle himself. And what about that time when—April 24 or perhaps 25—Galileo visited Magini and tried to show him and his important guests the Medician Stars he had discovered. Did they see anything? Of course not! Is this surprising, when this Galileo, this Italian, doesn't even know how the telescope works? These images—aren't they somehow unnatural? Somehow ghostly? Everyone knows that you can shape pieces of glass into lenses to see more clearly, but using lenses to make things appear that weren't there before? Spooky. Perhaps even—heretical? Galileo promises to write something about the optics of his
perspicullum
sometime in the future, but until then, who can trust him?

Kepler too had been a victim of Galileo's silent scorn, but that did not stop him from praising the truth where he saw it. He called Galileo's discoveries “highly significant” and said that anyone who was a true philosopher would want to study and reflect on them so as to know God's universe better. Then he went after Galileo's enemies, those “sour opponents of new things, who reject anything they don't know, and call wicked anything that goes beyond the traditional boundaries of Aristotle's philosophy.” After that, he put Galileo's discoveries into historical perspective, laying out what Galileo owed to others, placing his discoveries into a wider history of astronomy, and softening some of Galileo's more extreme claims. Finally, Kepler looked to the future, letting his imagination out for a run. Certainly, he said, the telescope was in its infancy, and new refinements in the instrument would lead to further discoveries. If Jupiter had moons, could there be moons around Saturn as well? Someday, he speculated, “Ships of the air, with sails designed for the atmosphere of heaven, could be made, and then people would arise who would not fear the vastness of space.”

But if there are other planets like our earth, then how are human beings special? How can we claim that divine providence is watching over us if we are only a part of the universe, if the stars and the planets were not
created for our sake, if we are not masters of creation? Wasn't that promised us in the Garden of Eden? Kepler feared this thought as much as anyone. Here is the committed Lutheran staring the modern age in the eye. Actually, his answer was not that different from Einstein's or Chandrasekar's. It was a Platonic answer—geometry rules everything in the universe, regulating the motions of the stars and the planets, fixing the order of the universe on immutable laws, for geometry flows out of God's mind, is an outpouring of divine reason. It is eternal. “That we human beings participate in it makes us an image of God.” It is human reason and human consciousness that makes us special. It is the human ability to find the superstructure of the cosmos that makes us part of the divine.

Of course, everyone read Kepler's tract as they wanted to. Galileo's enemies thought that Kepler had put Galileo in his place. George Fugger, the emperor's ambassador to Venice, said that Galileo's mask had been torn. Mästlin misread the pamphlet entirely and congratulated his old student on pulling out Galileo's feathers.

Galileo, for the most part, read Kepler rightly. On August 19, four months after he received a copy of the
Dissertatio,
he wrote a letter thanking Kepler for being the one man to have the intellectual ability to see the truth when he had not himself seen the Medician Stars. Later he wrote to the Tuscan minister and told him that Kepler had agreed with everything he had written in
The Starry Messenger,
without a single doubt.

It was not enough for Kepler, however, to simply read Galileo's report. As much as he supported the Italian's discoveries, he wanted to confirm those discoveries and to see what he could find out for himself. To do this, he needed a decent telescope, something he could not get in Prague. He asked the Tuscan ambassador, Julian de' Medici, to request a telescope for him from Galileo, which the ambassador did, but Galileo ignored the request. Not that Galileo had run out of telescopes. By that time, in order to curry favor with the great and powerful lords around Europe, he presented telescopes to anyone who was important enough to help his cause.

For some reason Galileo did not want Kepler to have a telescope of his own, however. It is likely that he was afraid that Kepler, who was unused to the instrument, might have the same problems that Magini had. Per
haps he was afraid that Kepler might join the voices of his critics, having, in an inexpert way, peered through the eyepiece to see nothing but a blur. On the other hand, Galileo's personality was such that he may have refused to send Kepler a telescope out of bald fear of competition. If Galileo could find wondrous things, could not the imperial mathematician, the author of the
Astronomia Nova,
also find other, even more significant things? So Kepler was caught. Without a telescope of his own, he could not confirm Galileo's reports, and yet scholars from all over Europe were complaining to him about his support of Galileo, hinting that because no one of any consequence had been able to confirm Galileo's story, then who could believe him? That Italian fellow might have been making up the entire thing.

Kepler wrote to Galileo requesting the names of those who could confirm his discoveries. Armed with such a list, Kepler felt that he could safely confront Galileo's enemies without fear of being accused of naïveté. Galileo wrote back, but he did not supply the requested list. Instead, he wrote that Cosimo II, the Grand Duke of Tuscany, and Julius de' Medici, the brother of the Tuscan ambassador, were his witnesses. But neither of these men was expert in astronomy, so that although they could say what they saw through the telescope, they could not tell what it meant. Then Galileo told Kepler about how much money he had made on his discoveries. The grand duke had given him over 1,000 ducats, with 1,000 more ducats per year added on as his regular salary. Kepler, who had trouble getting any money at all out of Rudolf II, must have felt as if Galileo were bragging about his wealth rather than supporting his own achievements.

That August, however, Kepler was finally able to observe the newly discovered moons of Jupiter. The most recent war between the Habsburg brothers had just ended, and the elector Ernst of Cologne, the Duke of Bavaria, had come to Prague from Vienna, where he had been negotiating with Matthias. He had been one of the important lords whom Galileo had graced with a telescope and, knowing that Kepler was in Prague, he brought it along to lend to the imperial mathematician so he could make his observations. While in the capital, the elector was kept busy meeting with the other princes to help them settle the war, so Kepler got a chance
to use the telescope while the meetings continued. Gathering his friends around him, Kepler spent from August 30 to September 9 observing Jupiter and recording the results. To ensure accuracy, the group set up a protocol, a kind of controlled experiment, with each man taking his turn observing through the eyepiece and then drawing what he saw on a tablet without showing his drawing to any of the others until all had taken their turn. Then they met and compared their drawings. There was enough agreement among them that Kepler published the results in a pamphlet he called
Narratio de Jovis Satellitibus, The Story of the Satellites of Jupiter.
Thus Galileo, for all his silence, had his discoveries confirmed by a man whose support he treated with such unkindness.