Tycho and Kepler (26 page)

The matter had by now become more than a private concern and threatened the Brahe family with public disgrace. Professors at the
university
mediated a new marriage contract in January in which Gellius would not reenter the service of Tycho at all. To enable him to afford the obligations of married life, he was to be appointed provincial physician of
Skåne, on petition of the nobility of that province, many of whom were Tycho’s kinsmen. Gellius reneged once again, and this time he judged it prudent to shift the blame by openly spreading malicious rumors about Magdalene and her family and attempting to sow dissension among Tycho’s relatives. The final breakdown of all negotiations occurred before the next autumn, 1595.

The gossip surrounding
this affair was catastrophic for Tycho. He watched helplessly as the high esteem in which he had thought Danish society held him evaporated like a mirage and he became a laughingstock. Gellius had found that preemptive slander was a very effective way to defend his own reputation, and he used that weapon on every possible occasion. From the court in Copenhagen and all parts of the kingdom, Tycho
heard reports of people sniggering at him, exchanging ribald jokes about the daughter he loved, sneering at Kirsten’s common origins, blaming Tycho and Sophie for failing to negotiate in good faith, dragging all their names through the mud. Ill will in the university, kept under wraps while Tycho appeared impregnable, emerged to add new voices to the din of calumny.

By October 1595, when Mars
was once again in opposition at a more favorable time of year to attempt the parallax observation, Tycho barely noticed, leaving the work to Longomontanus and others on his staff. They obtained both morning and evening observations only once, on October 27, and none of the observations are written down in Tycho’s hand.

In January 1596 Tycho took the only step that could restore his family’s
reputation. Though he had decided repeatedly not to do so for fear of adding to their grief, he at last brought suit against Gellius for breach of contract. Hearings took place in Lund and then in Copenhagen. From there the case was referred to the diet of the Danish nobility and then reassigned by the crown a year later to a special
court
of nobles. The specific outcome of the trial is unknown,
except that Gellius seems not to have suffered by it. He was soon granted a living of one canonry and two vicariates in Lund Cathedral and later became a professor of medicine at the University of Copenhagen.

Tycho was fearful that the loss of esteem caused by the failed betrothal would trigger similar humiliation for him in scholarly circles even beyond the borders of Denmark. He decided
it would be a wise move to enhance his reputation as an astronomer and deter his rivals by publishing an anthology of his correspondence having to do with astronomy.
Epistolae Astronomicae
⁶
(Astronomic Letters), which he printed in his new paper mill, clearly revealed his belief that Bär had plagiarized his planetary system. He included the letter he had written to Rothmann about the success of
the observations of 1582. Whether or not those observations showed a parallax for Mars, they proved that he had worked on the problem of Mars and on developing his planetary system long before Bär came to Hven.

In the dedication carved on the cornerstone of the paper mill, Tycho’s words indicate how stubbornly independent he was feeling:

This dam and paper-mill
⁷
with all their accessories
and the fish ponds above them have been built on the order of Tycho Brahe on a site where nothing of the kind existed previously, by his own design, under his own supervision, and at his own expense for the benefit of his country, himself and his heirs. Let us do good while we have the time.

Even while he thus reminded Denmark that his work had been for his country as well as for himself,
Tycho was becoming increasingly resigned to leaving. Early in May 1596 he ordered that his pilot-boat be refitted so that it could serve as a cargo boat. Clearly, he was thinking of transporting unusually heavy items either to or from Hven.

fn1
Gingerich and Voelkel point out the mysterious contradictory sequence of letters and explain how they have arrived at this explanation in “Tycho Brahe’s
Copernican Campaign.”

fn2
The description of these customs comes from social historian Troels Frederik Troels-Lund, as redescribed in English by John Christianson.

12

G
EOMETRY’S
U
NIVERSE

1594–1597

IN GRAZ, WHERE
Kepler reluctantly began his teaching job in 1594, he found a much less stable religious climate than in solidly Lutheran Tübingen. Here and in the rest of Styria, Protestants and Catholics lived side by side in nominal peace, but only thinly disguised their hostility. The rulers of Styria were members of the royal Hapsburg family and
staunch Catholics. Under the Peace of Augsburg they had the right to declare that everyone in Styria must be Catholic. However, nearly all the most powerful landholders were Lutheran, and the Hapsburgs had found it advisable to allow Protestant nobles in the countryside and Protestant citizens in Graz and other cities to practice their faith openly.

The school where Kepler taught was thick
in the middle of this uneasy truce and by no means neutral. It had been established in 1574 as a deliberate countermove to the founding of a Catholic Jesuit college the previous year. Its four preachers and twelve teachers were influential members of the Protestant community, and the school was, to all intents and purposes, the rallying center for Protestants in Graz.

At first none of this
controversy touched Kepler. His concerns were almost entirely academic. His teaching duties were in the upper school, where he taught advanced mathematics, including astronomy. Either he was not a particularly exciting teacher or the subjects were not popular, because few students attended his classes in the first year and none in the second. School officials looked for other classes Kepler could
teach and assigned him rhetoric, Virgil, less advanced arithmetic, ethics, and history.

Graz, in an early seventeenth-century engraving attributed to Matthäus Merian Sr.

Kepler’s duties extended beyond the classroom. He was also district mathematician, a public office that had considerable responsibilities connected with it. One of them was the compilation of an annual calendar with astrological predictions for the coming year. Kepler could approach this task with confidence.
Already at Tübingen he had been known for his astrological skills. The district mathematician’s calendar told what to expect about weather, harvests, war, disease, the most auspicious periods during which a physician might bleed a patient or perform surgery, when farmers should sow seed, when the weather would be most benign or most inclement or dangerous, when the Turks would attack, and when
one should anticipate religious or political troubles. What Tycho had to produce for the princes of Denmark, Kepler had to
produce
for the entire citizenry of Graz and the surrounding countryside—albeit for only a year at a time instead of a lifetime.

Kepler’s attitude toward astrology fell far short of the confidence most of his contemporaries had in it. He was already calling it the “foolish
little daughter”
¹
of respectable astronomy. Later he would write that he abhorred “nourishing the superstition
²
of fatheads” and that “if astrologers do sometimes tell the truth, it ought to be attributed to luck.” However, he did not fully reject the idea that there were links between the cosmos and human beings. He, like Tycho, thought that the movements of the planets must in some way influence
what happened on Earth, but probably far more subtly and far less deterministically than was commonly supposed.

Whatever his reservations, Kepler produced the calendars; they were, after all, a part of his job description. Before long, Graz found it had a very able district mathematician indeed, though he was not exactly a bearer of good news. For 1595, he had predicted an exceptionally cold
winter, an attack by the Turks from the south, and a peasant uprising. All of those prophecies came true.

Michael Mästlin, Kepler’s mentor at Tübingen, was particularly scornful of Kepler’s astrological activities. Kepler took exception with him in a letter: “If God gave each animal
³
tools for sustaining life, what harm is there if for the same purpose he joined astrology and astronomy?”

However, Kepler, the astrologer, failed to predict the most momentous event in his own life that year, a discovery he made in his classroom. Until then, Kepler had been an obscure teacher with some mathematical skills and little to set him apart from hundreds like him in Europe. Now emerged the Kepler who would transform astronomy, and also the Kepler whom some would think quite mad, for the
discovery he made that day sounds to the twenty-first century almost as outlandish as the astrology for which he was admired.

On July 19, 1595—he kept careful record of the date, so significant did it seem to him—Kepler drew a diagram for his students on
the
chalkboard. The drawing demonstrated the progression of the Great Conjunctions of the planets Jupiter and Saturn; that is, when Jupiter
passes Saturn in the zodiac. Jupiter and Saturn are the slowest moving of the planets that were known in Kepler’s time, and since Tycho Brahe had recorded the Great Conjunction of 1563 as the second entry in his logbook, there had been only one other.

To understand what Kepler drew, picture the celestial sphere with Earth at the center. The two planets, Jupiter and Saturn, travel in enormous
circles around Earth. Every twenty years Jupiter catches up with Saturn, the more distant of the two planets, and passes it. Kepler’s drawing showed that these passings, or conjunctions, do not happen every time at the same points in the zodiac. For example, the fourth conjunction in the drawing (1643) occurred at
almost
the same point as the first (1583), but not quite; the fifth at almost the
same point as the second, but again not quite, and so on. As Kepler drew the lines, each went just beyond joining a former line to make a closed triangle. Instead, the quasi-triangle “rotated,” creating the pattern on the chalkboard. In Kepler’s words, “I inscribed
⁴
within a circle many triangles, or quasi-triangles, such that the end of one was the beginning of the next. In this manner a smaller
circle was outlined by the points where the lines of the triangles crossed each other.”

That second circle was visible in his drawing, half the size of the outer circle. While the
points
of the triangle “drew” the outer circle as the triangle rotated, the
middles of the sides
of the triangle “drew” the inner circle. The triangle’s lines never trespassed into the inner circle, and its points
never went outside the outer circle. The triangle dictated how far apart the two circles had to be.

Figure 12.1:
⁷
The pattern of Jupiter-Saturn conjunctions, showing where they happened in the zodiac. The conjunction in 1583 (right side of drawing) occurred when the two planets were in Aries/Pisces. The conjunction in 1603 (lower left) was in Sagittarius, in 1623 in Leo, in 1643 in Aries, in 1663 in Sagittarius, and so on. The drawing is from Kepler’s
Mysterium
, with the zodiac names and
the dates added around the rim. The reason for the names of the elements—earth, air, fire, water—will be explained later in the discussion of the appearance of “Kepler’s Star.”

If the conjunctions occurred repeatedly in the same positions in the zodiac, Kepler’s drawing would have looked like the insert, upper right. Instead, they “progress,” as represented in the central figure.

Looking
at what he had drawn, Kepler was struck by an insight that made him feel as though he had suddenly and unexpectedly opened a book and found inscribed there the secret of creation. As he wrote later: “The delight that I took
⁵
in my discovery, I shall never be able to describe in words.”