Tycho and Kepler (50 page)

At last, in 1624, Kepler finished the Rudolfine Tables in the new logarithmic form. Tables like these did not give daily positions of the planets; rather, they were far more generally useful, making it possible to figure out any planet’s position
for any time thousands of years into the future or the past. In the case of the Rudolfine Tables, Kepler’s instructions about their use, with examples, took up about half the volume of the work. Kepler included logarithm tables, Tycho’s catalog of a thousand stars, and latitudes and longitudes of many cities.

Once again, having completed a major work, Kepler’s difficulties with it were far
from over. Financing publication was a serious problem. A trip to Vienna, where the imperial court was now situated, won him promises that payment would be forthcoming via various cities that would turn imperial funds over to Kepler, but after ten months of traveling among these cities, he came back with virtually nothing to show for the effort. He had taken the opportunity to order four bales of
paper from the cities of Memmingen and Kempten and had them sent directly to Ulm, where he expected to print the book. Eventually he would have to pay for the publication himself, with Tycho’s heirs all the while trying to claim a share of the profits and censorship rights. Nevertheless, it was the Rudolfine Tables, more than any of Kepler’s other works, that led to the widest recognition of what
he had achieved.

A manuscript such as this, with 120 pages of text and 119 pages of complicated tables, was a printing challenge beyond anything Planck had attempted so far, and he, in any case, was eager to leave Linz and its religious turmoil. Ulm seemed to Kepler the best place to print the book, where there were other skilled printers and no war going on, but Emperor Ferdinand rebelled
at the notion of having the work done outside Austria.

As this was debated, the Thirty Years War, which had not ended with the quashing of the Bohemian rebellion, came perilously close again. A peasant uprising in the summer of 1626 almost succeeded in driving the Bavarian troops and Ferdinand’s forces out of Linz and Upper Austria. Kepler’s house, situated on the city wall, had to be opened
for soldiers guarding the wall, while peasant bands, burning and looting, threatened the capital. During this two-month siege, Kepler almost lost the Rudolfine Tables. On June 30, a fire started by peasant rebels spread and consumed Planck’s press but somehow spared the handwritten manuscript.

The loss of the press and the near destruction of his manuscript were the last straw for Kepler.
He had lived in Linz for fourteen years, longer than he had in Prague. He was exhausted by the confusion and disorder and wanted nothing so much as to complete the publication of the Rudolfine Tables in relative peace. When the siege was finally lifted in August, he wrote to request again the emperor’s permission to depart, and this time it was granted. In mid-November 1626, the Kepler family took
a boat up the Danube in the direction of Ulm. By this time, there were two more young children, Fridmar, three years old, and Hildebert, one. Their elder sister Cordula was five. Beyond Regensburg the river was completely frozen, so Kepler left his wife and children there and went on alone overland toward Ulm “on a wagon
¹⁰
laden with plates of my figures and Table work.” When he arrived, on December
10, 1626, he found lodgings across the street from the printing shop of Jonas Saur, who finally printed the Tables.

Kepler oversaw every aspect of the printing and worked almost daily with the typesetters. He had brought with him his own set of numerical type (which had not been destroyed when the press burned) and the astronomical type that he had had custom-made for the
Tables
. As the pages
came off the press, he proofread each one. Kepler saw this book as the crowning achievement of two lifetimes, Tycho Brahe’s and his own. Even though he had written it himself, discovered the new laws that made it correct, and done all the calculations, he put Tycho’s name first on the title page as the primary author.

Kepler decided that the
Rudolfine Tables
should have an elegant frontispiece.
He had an idea in mind and asked a friend from Tübingen, Wilhelm Schickard, to prepare a sketch of it. The frontispiece summed up Kepler’s concept of the world of astronomy, including its history, and was at the same time a masterpiece of whimsy. It shows a pavilion with twelve columns. Those at the back are hewn logs, and a Babylonian astronomer stands there using only his fingers to make an
observation. Babylon was where astronomy had its roots. Nearer the front, Hipparchus on the left and Ptolemy on the right stand by columns built of brick. Closer in the foreground sits Copernicus by an Ionic column on whose pedestal he has propped his famous book, and Tycho stands by a Corinthian column with some of his celebrated instruments hung on it. He and Copernicus are deep in discussion,
presumably about the Tychonic and Copernican systems, for Tycho points at the ceiling of the temple, where there is a drawing of his system. Kepler cunningly has him not telling Copernicus that it is correct, but asking, “Quid si sic?” (How about that?)

Ringing the rooftop are six goddesses, each a symbol of something that helped Kepler in his discoveries: Magnetica (on the far right); then
Stathmica, the goddess of law; Geometria; Logarithmica; and finally a goddess holding a telescope and another with a globe that casts a shadow.

The frontispiece of the
Rudolfine Tables
.

At the very top of the pavilion flies the Hapsburg eagle, with coins dropping from its beak, a symbol that needs no explanation.

Kepler did not show Tycho’s heirs the panels in the base of the pavilion before publication, though they would have approved the center panel, a map of Hven. To the left is a panel showing Kepler sitting at a table,
by candlelight, a few numbers scratched on the tablecloth, his major books listed on a banner above his head, and a model of the roof of the temple on the table before him. Tycho stands above beside the most elaborate column, but it is Kepler who has labored in the basement, at night, and brought about this marvelous achievement, this temple of the goddess of astronomy Urania, the
Rudolfine Tables
. Very few of the coins are dropping onto Kepler’s desk.

Detail from the frontispiece of the
Rudolfine Tables
.

The
Rudolfine Tables
lived up admirably to Tycho’s and Kepler’s hopes for them. The planetary positions given by the
Tables
were much more accurate
¹¹
than those given by the Alfonsine or Prutenic Tables or tables that had been composed by Longomontanus and others. Predictions for Mars, for instance, had previously erred up to five degrees.
The
Rudolfine Tables
stayed within plus or minus ten
arcminutes
of the actual positions.
^fn1
In 1629, when Kepler was preparing an ephemeris for the year 1631, he realized that because of the dependability
of
his
Rudolfine Tables
, he could confidently predict two “transits” that would occur during that year—one of Mercury and another of Venus—across the disk of the Sun.
^fn2
He published his predictions
in a short pamphlet,
De Raris Mirisque Anni 1631 Phenomenis
(1629). He would not live to see how superbly accurate he had been.

fn1
This information comes from Owen Gingerich (1973).

fn2
On November 7, 1631, the astronomer Pierre Gassendi observed the Mercury transit from Paris. The result was a triumph for Kepler’s astronomy. The transit of Venus was not visible in Europe, because it
was night there when it occurred.

23

M
EASURING THE
S
HADOWS

1627–1630

ONCE BEGUN, PRINTING
the
Tables
went quickly. In early September 1627 Kepler took copies to the Frankfurt Book Fair and finally rejoined his family in Regensburg in early December, only to leave them again after Christmas to take a presentation copy
¹
of the book to Emperor Ferdinand. The court was in Prague, where Ferdinand was installing his son
as the king of Bohemia, and everyone was in exceptionally good spirits because the Protestant revolt had finally been completely put down. The most immediate cause for celebration was the defeat of invasions in the north by the Protestant King Christian IV of Denmark, none other than Tycho Brahe’s old nemesis. Christian had been driven from German soil and also from the entire formerly Danish peninsula
of Jutland.

Noticeably absent were all Kepler’s old Protestant friends, including poor Jesensky, whose head was a grisly presence on the bridge tower. But many other old friends were in Prague as well as many admirers, and the emperor was so pleased with the
Rudolfine Tables
that he granted Kepler four thousand florins, ten times his yearly salary. That brought to twelve thousand florins the
amount of money owed him from the treasury, or the equivalent of thirty years’
salary
. Kepler knew he would never collect that if he left the emperor’s service. As it was, he was told that all his fears that he had already lost his job because of the emperor’s edicts in Linz were groundless. All he needed to do was convert to Catholicism. Kepler, of course, refused.

Kepler had been offered
a job in England, and he might at this point have made an abrupt decision to forfeit all back salary and go there immediately had it not been for a man with whom Kepler had had a long association by correspondence but not met in person before. Albrecht Wallenstein had commissioned a horoscope from Kepler in 1608 without revealing who he was or anything about himself except the date and time of his
birth. Kepler, always good at horoscopes, had produced one that greatly impressed Wallenstein.

Wallenstein was a favorite of the emperor and was, in fact, the general largely responsible for the defeat of Christian IV of Denmark. He let it be known that he believed the different faiths must coexist peacefully, and he allowed the practice of Protestantism in his Silesian duchy of Sagan. By
moving there, Kepler would be able to maintain his faith while remaining in imperial service. As the agreement finally was worked out the following February 1628, Kepler was promised a house, a printing press, and a generous stipend of a thousand florins a year.

Kepler made a final trip to Linz in the early summer, where the beleaguered city surprised him with a payment of two hundred florins
for their presentation copy of the
Rudolfine Tables
. Kepler moved his family to Sagan in July. He was fifty-six years old.

Kepler was unhappy in Sagan
²
. No one knew him, and he knew no one. There was little intellectual stimulation, and the local dialect was so different from the German Kepler spoke that he had difficulty understanding it or making himself understood. He was suffering, as
usual in his later years, from eczema and abscesses. Most discouraging of all, he had hardly arrived when the Counter-Reformation followed him. Once again he was exempted from enforced conversion and the banishment of those who refused to convert, but it was a bitter experience to see it all happening for a third time.

In the winter and spring of 1630, Kepler’s mood lifted a little. The long-promised
printing press and a printer to work at it finally materialized, saving Kepler the trouble of setting his own type by hand and taking it to a nearby town for printing. In March Susanna, Kepler’s daughter by Barbara, married Jacob Bartsch, a student of mathematics and medicine in Strasbourg who had worked for Kepler as an assistant. Kepler decided that the wedding should take place in Strasbourg,
though that was too far away for him to attend, given his age and the fact that his own wife would be eight months pregnant by the time of the festivities.

Matthias Bernegger, a longtime friend and correspondent living in Strasbourg, had recommended Bartsch as a suitor and brought the young couple together. Bernegger gave Kepler a detailed and glowing account of the celebration in a letter.
On March 12, the bridegroom received his medical degree in the morning, and later in the day the couple were wed. Kepler’s brother Christoph, his sister Margarethe, and his son Ludwig were part of a wedding procession that included
Strasbourg’s
most prominent citizens, and huge crowds lined the streets as they passed. “It was meant
³
, especially, to honor you,” Bernegger told Kepler.