Tycho and Kepler (40 page)

The Belvedere, a pavilion in the gardens of the imperial palace in Prague, where Tycho set up his instruments in the autumn of 1600.

The last of Tycho’s instruments reached Prague in October, at about the time Kepler himself returned. The emperor arranged for Tycho to mount them on the balconies of an ornamental summer-house in the palace grounds, now called the Belvedere. Tycho was bitterly
disappointed. He had hoped to use the need to install the instruments in their clifftop bays as an excuse to return to Benatky.
From
the Belvedere’s south-facing balconies, the emperor’s palace complex blocked off a good portion of the southwestern sky.

By New Year 1601, Rudolf’s mental state had improved, and his already high regard for Tycho had increased during the difficult months they
had weathered together. When Tycho petitioned for citizenship and nobility for himself and his family in February, the emperor himself sponsored their petition. At last Kirsten and their children enjoyed a status that would permit them to inherit from Tycho and marry nobles of their new homeland. Tycho’s estate was still large, especially if one included back pay from Rudolph (mounting up again),
the value of instruments, books, and observations, and the loan (made shortly after he left Denmark) that he was finally calling in from the two young dukes of Mecklenburg. The future of Tycho’s family at last seemed secure.

On the other hand, his scholarly future looked increasingly bleak. He had been near to having a new Uraniborg the previous spring. Now it seemed he would have to relinquish
all hope of that, for Rudolph bought him the same palace he had rejected when he first came to Prague from Denmark. It was undeniably a beautiful house and garden, and an astronomer forced to live in the city could hardly have done better than this hillcrest location. Nevertheless, the mansion still had the same disadvantages that had caused him to turn it down eighteen months earlier: The tower
was not large enough, and the location was too accessible to the court, just a few minutes’ walk west of the imperial palace and no time at all in a carriage.

Again, Tycho’s enjoyment of a splendid, nearly royal lifestyle was an antidote to despair. He moved his library into the house, the three thousand books that had been waiting all this time in Magdeburg. He took smug satisfaction, when
spring came, in mentioning in letters inviting former acquaintances and relatives in Denmark to his daughter Elisabeth’s wedding that the summer nuptials would be held in his palace, formerly belonging to the vice chancellor of the empire. The contingent from Denmark was not expected to make an appearance, but it was a triumph to inform them how luxurious and
pampered
his present situation was
and that his daughter was marrying a nobleman.

Nevertheless, the discouragement of having to move family and research establishment again, not back to Benatky but to this unwanted house, was a serious drain on the fifty-four-year-old Tycho’s energies. During that winter, his friends began to notice that he had lost some of his usual spark and seemed to be resigning himself to old age and declining
health. Tycho’s brother Jørgen, who was much younger than he, died in February. Jesensky reported that in the middle of a cheerful conversation Tycho would change the subject to talk about death. Kepler commented in a letter to Mästlin, who was still not answering, that Tycho was acting childish and capricious, though he was “still good-natured,”
¹⁰
and that Tycho seemed burdened with cares: “He
always resembles a lost man, but always somehow extricates himself. His success at this is to be wondered at.” Tycho made some progress reorienting his instruments for their new location, but he did little observing and failed to move ahead at all with the books that he had been working on for many years. Several of these were near completion, and it would not have required a great deal of effort
to finish them, but he lacked the energy and interest.

When Tycho and his family moved to the mansion, the Keplers moved there too. Yet in spite of the difficulty Tycho was having finding good computational help, he wasted Kepler’s talents that winter, partly because Kepler wasn’t at his best—his fever kept returning—but also because Tycho was still paranoid about his observations and not
satisfied that he had completely defeated Ursus, even though the man was dead and all known copies of his offensive book had been destroyed. Kepler complained later in a letter to the astronomer Giovanni Antonio Magini that Tycho would show him his “choicest” observations,
¹¹
but only “inside his four walls,” and say to him, “Get to work.” If Kepler asked to see observations other than those Tycho
set before him, Kepler was told he was being too inquisitive. “If only I could copy
¹²
them quickly enough!” Kepler wrote to Mästlin, and in the same letter mentioned an idea for prising some of the observations
out
of Tycho: “If you would send him some of your observations, he would, I think send some to you, too, if you ask him to do so. For in spite of all the instability of his character, he
is, after all, a man of great benevolence.” Mästlin did not reply.

As for Kepler’s own astronomy, he spent a little time on some theories about Mercury, Venus, and Mars, discussed them with Tycho, and thought about the orbit of the Moon, but this was not a productive winter. “A fever gripped me,”
¹³
Kepler later recalled. “In the meantime I wrote against Ursus on Tycho’s orders.” In a letter
to Mästlin he complained, “Because of this illness
¹⁴
of mine I am doing nothing but write against Ursus.” Kepler found it distasteful to carry on the dispute after Ursus’s death, but Tycho was still obsessed with proving that he, not Ursus, had invented the Tychonic system. Not only did he want to destroy Ursus’s scientific credibility, to keep him from ever getting credit for it, but he also
wanted to discourage others who, he believed, were also guilty of plagiarizing his system. The main current target of Tycho’s fears was a Scotsman named Duncan Liddell, whom Tycho had suspected ever since Liddell visited Hven in 1587 and 1588. Liddell seems to have been completely innocent; over the years he remained a responsible scholar and teacher and one of Tycho’s staunchest supporters, though
he kept his distance because of Tycho’s suspicions and hostility.

Kepler put his feverish head to the task of coming up with something that would satisfy Tycho’s instructions that he “rebut even more clearly
¹⁵
and more fully than you have done previously Ursus’s distorted and dishonest objections to my invention of the new hypothesis . . . and ascribe the new hypothesis to me, as is right,
just as you did before with demonstrable reasoning.” Kepler did not finish his “Defense of Tycho against Ursus”
¹⁶
that winter and spring. He would resume work on it several years later, but the still unfinished manuscript was not published until 1858. Kepler made the most of a poor assignment. It is one of the finest analyses ever written about scientific methodology, pointing out a difference
between the Ptolemaic and Copernican models that was of profound importance
to
Kepler and that remains even today the primary reason for deciding in favor of Copernicus. In principle, Ptolemaic astronomy was not “incorrect.” It could plot and predict the courses of the heavenly bodies just as correctly as Copernican astronomy. So could the Tychonic model. But, wrote Kepler, “If in their geometrical
conclusions
¹⁷
two hypotheses coincide, nevertheless in physics each will have its own peculiar additional consequence.” In other words, when one began asking the “why” questions, seeking the physical causes for the motion, Ptolemaic and Tychonic astronomy could no longer hold their own. To Kepler, the search for physical causes had become paramount.

In April, with his health not improved,
Kepler interrupted work on this treatise to make another trip back to Graz. Barbara’s father had died, and Kepler needed to salvage whatever he could of his wife’s inheritance. Most of that was tied to estates and useless to the Keplers unless it could be converted into cash. Though the Graz authorities did not block Kepler’s return, in a financial sense the four-month trip was an exercise in futility.
Nevertheless, Kepler finally shook off the fever that had afflicted him for nearly a year, and he wrote to Barbara that he was enjoying visiting friends, who everywhere were treating him as a welcome guest.

Barbara wrote
¹⁸
that she was not getting as much money from Tycho as he had promised. She could not buy wood for the fire. An angry exchange of letters ensued. Tycho told Kepler to calculate
what was owed and he would be paid, but to behave in future more considerately toward his “benefactor” and “have more
¹⁹
confidence in him.” Kepler bristled at this insinuation that Tycho was giving him charity instead of fair recompense for his work. The contretemps finally ended agreeably, but it was symptomatic of the dissatisfaction Kepler still felt with his working arrangement.

Kepler
kept up with events in Prague through Barbara’s letters, partly written in the Keplers’ own secret code, which would not have helped Tycho’s paranoia if he had known about it. The most important occasion of the summer was the wedding of Tycho’s daughter Elisabeth
to
Tengnagel in June. Kepler inquired of Barbara in code whether the bride looked pregnant. Perhaps she did, for Tycho’s grandson was
born in late September.

Though Tycho expressed some displeasure with the young couple prior to the wedding, perhaps because of the pregnancy, he was immensely gratified that his daughter, who in Denmark was not even considered his legitimate child and could never have married into the nobility, was marrying Tengnagel. Although Tycho had previously referred to him as his
domesticus
, or servant,
Tengnagel was a nobleman, a man of great political promise whom Tycho had known and trusted for many years. In this marriage Tycho and his family were repaid a little for the grief and disgrace of Magdalene’s ill-fated betrothal to Gellius. Tycho did everything in his power to make the triumph as public as that embarrassment had been, and the invitation list was long and illustrious. Even Rudolph
was invited, though there was no expectation that the reclusive emperor would attend. Tycho’s sister Sophie, who had been intimately involved in Magdalene’s sorrows, hoped to come, but ill health prevented her at the last minute. She had previously begun several journeys to Prague and had to interrupt them midway because of Erik Lange’s recurring disasters. Elisabeth and Tengnagel left after
the wedding for the Netherlands along with another of Tycho’s assistants, Johannes Erikson, so when Kepler returned in late August, a healthier, more optimistic, though poorer man, the house by the wall was less crowded.

By that autumn of 1601 the decision Tycho had been trying to make for nearly a year and a half had taken on greater urgency. His work was not finished and would not be, in
his eyes, until there was complete justification of his belief in the Tychonic system. His astronomy would continue to languish, incomplete, with no hope of accomplishing what he had spent a lifetime working toward, unless he finally put his full trust in Kepler. If Tycho was indeed burdened with premonitions that he had not long to live, he surely anticipated that that decision would mean trusting
Kepler beyond his death. And—though
Tycho
had to have recognized that Kepler would put the observations to better use than any other man available—trusting Kepler could not mean trusting him ultimately to support the Tychonic system. Nevertheless, with Ursus buried for more than a year, Tycho at last made the leap of faith and wagered his earthly immortality on Kepler.

Tycho invited Kepler
to accompany him to the imperial court. There, for the first time, he introduced him to Emperor Rudolph and proceeded to make a dramatic proposal: Tycho and Kepler would take on the prodigious task of compiling a superb new set of astronomical tables based on Tycho’s observations and more accurate than any the world had ever known. With the emperor’s gracious permission, these would be named the
Rudolfine Tables. Great astronomical tables in the past, such as the Alfonsine Tables, bore the names of their royal sponsors. The Rudolfine Tables would, similarly, be a monument to Rudolph and a testament to his generous support of learning. There was nothing further required of the emperor than what he had already granted Tycho . . . except for a salary for Johannes Kepler.

The emperor
was thrilled with the idea. The paperwork for Kepler’s salary was begun posthaste.

Tycho had previously provided for the future of his family. Now he had also provided for Kepler’s future. With this bold decision, Tycho placed all his precious observations in Kepler’s hands. Tycho’s secrets would no longer be secrets from Kepler.

O
N
O
CTOBER
13, 1601, only a few days after meeting with the emperor, Tycho accompanied a friend, Councillor Minckwicz, to dinner at the palace of Peter Vok Ursinus Rozmberk just a few steps from the emperor’s gate. Courtesy forbade one to rise from the table for any reason before one’s host had risen, and it was Tycho’s adherence to this simple point of etiquette, “so trivial an offense,”
²⁰
as he himself
put it, that brought him to his deathbed.