Tycho and Kepler (19 page)

Kepler was not
the colorless, drab individual that some authors and historians have made him out to be. He had enthusiasms in abundance. By his own report he, as a boy, “devoted [himself] wholeheartedly and energetically to games.” In his teens he “had a high
opinion
of sense of duty, self-control, and industriousness,” but “a man who is really useful has to have not only the power of good judgment but also
ardor and passion.” Perhaps following that last maxim, “I didn’t obey reason until my twenty-sixth year” (the year he wrote these words).

Earnestly but exuberantly religious, Kepler had a vivid and adventurous life of the mind. In his spare time, which was scarce, the teenage Kepler took pleasure in attempting to write original poetry in a variety of meters, imitating the ancient forms. He
reveled in jokes and puzzles, loved allegories and riddles, liked to play with anagrams, was pleased with paradoxes. Purely for enjoyment, he tried to improve his memory by learning the longest psalms by heart and attempting to memorize all the examples in one of his grammar books. The way his mind flew quickly among various subjects was a joy to him, rarely a problem. In fact, all his life his writing
continued to be full of peculiar and interesting leaps from one train of thought to another, leaving readers attempting to follow him puzzled by his mental track.

Though Kepler may not have chosen to “obey reason,” he was a serious student, and he thought and prayed a great deal about the religious controversies and his private reactions to them. At Adelberg some of Kepler’s young teachers,
fresh from Lutheran university at Tübingen and afire with their newly acquired learning, were particularly eager to refute the doctrine of the Holy Communion espoused by the Calvinists. Kepler stubbornly followed his usual practice of accepting little except what he had worked out for himself after listening carefully to the sermons or arguments, praying, and studying his Bible. He was approaching
the awkward conclusion that the correct interpretation of the Bible was exactly the one he was hearing condemned by his instructors and from the pulpit.

Kepler was particularly disturbed about the idea held by some that God damns the heathen who do not believe in Christ. That doctrine he could not accept, nor did he keep quiet about it. He
also
was so bold as to recommend peace between Lutherans
and Calvinists, and claimed also to be “just to the Catholics,” setting a course that would have tragic consequences for him later, and that would, in fact, eventually leave him no choice but to appeal to Tycho Brahe for a job.

In October 1587 Kepler became a registered student at the University of Tübingen, but the “Stift,” where he was to lodge as a scholarship student supported by the duchy
of Württemberg, had no room available for that year. He remained for a third year at Maulbronn, as a “veteran,” and ended up taking his examination and completing his B.A. degree by examination the following September, though he had not yet attended a class at the university.

W
HILE
K
EPLER WAS
a schoolboy, mastering subjects that he and others
thought essential for his future, Tycho, with trial and error and his own superior inventive intellect as his teachers, continued to explore the frontiers of astronomy with a rigor that no one else considered essential. One splendid result of this effort were the great instruments of Hven, unique and unsurpassed among the astronomical instruments that predated the telescope.

The first masterpiece
Tycho produced in his own instrument shop was a giant globe
²
that became the centerpiece of Uraniborg’s library. The instrument maker Schissler in Augsburg had begun to construct it under Tycho’s guidance in 1570, but Tycho had left Augsburg to join his dying father in Denmark before it was completed, and he did not see it until he returned five years later. By that time the wood had warped, and
there were splits between the pieces.

Nevertheless, Tycho had not forgotten the globe languishing in Augsburg, and in August 1576 he had the poor relic brought to Hven, where his artisans filled in the cracks and restored its shape “by inserting
³
many hundred pieces of parchment.” Tycho allowed the globe to sit two years longer while he watched for seasonal changes in
its
wooden structure.
Finally in 1578, satisfied that “it stayed completely spherical at every point,” he had it surfaced with brass sheets “with such great care and accuracy that one might believe the globe to be of solid brass.” After waiting another year to find out whether the globe would still stay completely spherical, he had the equator and the zodiac etched onto the brass “and divided each degree of these circles
accurately into sixty minutes of arc by means of transversal points according to our custom.” By the time he had finished, his remark that he had the globe made “at no small cost” was an understatement.

All this effort and expense were not merely to produce a decorative piece. The globe represented the celestial sphere and allowed one to view that sphere from the “outside.” Transforming trigonometrical
coordinates, which was necessary if an astronomer knew the altitude and azimuth of a celestial object and wanted to calculate from them its declination and right ascension (
see appendix 2
), was a tedious undertaking in Tycho’s day. The globe made this process considerably easier.

Tycho later included a drawing of this remarkable instrument (
see color plate section
) in his book
Astronomiae
Instauratae Mechanica
, which shows the globe girdled by a platformlike ring resembling a ring of Saturn. The ring represented the horizon for an observer at Uraniborg. The circle seen outlining the perimeter of the globe was the meridian (
see appendix 2
). The globe rotated on an axis running from the north celestial pole (I) to the south celestial pole (K). There was another rulerlike strip (somewhat
right of center in the drawing) running from the zenith (B) to the horizon, which was the equivalent of the curved edge of a quadrant. It allowed Tycho to measure altitude on the globe. Fixed at the zenith, it could be moved around the horizon at its other end to measure azimuth. Two other lines on the globe that are visible in the drawing were the equator (farthest to the left as it reaches
near the top of the globe) and the ecliptic. The support for the globe, from the ground to the horizon ring, was about five feet high, and the globe itself measured almost six feet in diameter.

Tycho proudly referred to his great globe as “a huge and splendid
piece
of work” and wrote that “a globe of this size, so solidly and finely worked, and correct in every respect, has never I think been
constructed up to now . . . anywhere in the world. (May I be forgiven if I boast.)” It became the chief conversation piece of Uraniborg and the envy of visitors. He entered on it the positions of all the stars he had observed and cataloged—as they would appear in the year 1600. His goal was a thousand stars, “so that all the stars that are just visible to the eye were entered on the globe.” Defending
the length of time it took him and his artisans to finish the globe and for him to catalog the stars and enter them on it—the task would eventually require about twenty-five years—Tycho used words that many have taken as a motto for all his work: “If it has been done well enough, it has been done quickly enough.”

In the next two and a half years after the completion of the globe in 1580, Tycho
and his artisans on Hven produced more large instruments, most notably two quadrants, inaugurated in 1581 and 1582. Tycho named the first his “large quadrant” and henceforth referred to the old
quadrans mediocris orichalcicus azimuthalis
as his “small quadrant.” The second was his “great mural quadrant,” an artistic as well as scientific masterpiece that more than any of his other instruments
has come to symbolize Tycho Brahe.

Tycho built the great mural quadrant
⁴
into the structure of his house, using a section of wall constructed along an astronomically precise north-south line. The instrument, a solid brass arc six and a half feet in radius, five inches wide, and two inches thick, was mounted on the wall. On this quadrant the curved edge of the pie slice was
nearer
the observer.
Movable sights were clamped onto the arc. The engraving Tycho later included in
Astronomiae Instauratae Mechanica
(
see color plate section
) shows them set near twenty and seventy-five, with one of Tycho’s assistants peering through the one near twenty. There was no physical connection (such as the alidade was in earlier quadrants) between these near sights and the farther sight—the cylinder in
the opening in the wall visible in the upper left of the engraving.

Before 1587, the wall on which the quadrant was mounted probably remained blank. Then Tycho commissioned Steenwinkel, who had helped design and build Uraniborg, to paint scenes symbolizing Tycho’s palace and his work, framed by six arches. Steenwinkel’s painting showed the basement with its alchemical laboratory and furnaces,
the library on the floor above it with the great globe, and the observatory above that. Hans Knieper, the finest landscape artist in Denmark, was working at Elsinore, and Tycho brought him to Hven to paint a distant landscape for the background, visible through the arches of the observatory level and above them. For the life-size portrait of himself, seated in the foreground within the arc with
a dog at his feet, raising his arm to point at the front sight of the quadrant, Tycho commissioned Tobias Gemperle, a painter he had met during his 1575 European sojourn and brought to the attention of King Frederick. Frederick had named him court artist, and Tycho had previously commissioned him to paint the altar of St. Ibb’s Church. Tycho was extremely pleased with the portrait in the mural quadrant.
“The likeness
⁵
could hardly be more striking,” he wrote, “and the height and stature of the body is rendered very realistically.” He regarded the background mural as the artistic masterpiece of Uraniborg.
^fn1

Tycho was also experimenting with
armillaries
, instruments consisting of arrangements of rings showing the relative positions of the various circles on the celestial sphere such as the
meridian, the celestial equator, and the ecliptic. Tycho planned to do extensive work on the planets, and armillaries were particularly useful for calculating the coordinates involved in planetary observations. He had begun work in 1577 on a small model with only three inner rings.

Figure 8.1: Tycho’s first armillary. Drawing from
Astronomiae Instauratae Mechanica
. The outermost ring represented the meridian (see appendix 2). The devices marked
C
and
D
represented the north and south celestial poles and are the points on the meridian ring on which the next smaller ring is attached.
C
and
D
could be raised or lowered along the meridian ring until they corresponded with
the latitude of the place at which the observer was located, with
B
(from which hangs a plumb line) representing the zenith. The next smaller ring served to carry a slightly smaller ring representing the ecliptic, which carried a fourth ring for measuring latitude.