Tycho and Kepler (8 page)

Tycho was not the only person who noticed the nova, and not all agreed
that it was further away than the Moon’s orbit. Some actually made observations and were convinced that the new star was below the Moon, even though they could discover no parallax. Some insisted it
was
a comet. Others conceded that it was farther away than the Moon but argued that it was not really new, or that it was not a real change in brightness that caused it gradually to dim after its first
appearance.

Evidently, Tycho was the only scholar capable of seeing beyond Aristotelian assumptions. He measured the angular distance between the nova and another star, and repeated the measurement several hours later. Though the sky as a whole had moved, the distance between the two stars had not changed. Tycho performed this test more than once, measuring the angular distance between the
nova and not one but several other stars. Again and again he found no change, no parallax shift. Because this result ran so counter to current science and philosophy, Tycho decided to come at the problem from another direction. He had already calculated, indirectly—by comparison with other stars—how far the nova was above the celestial equator in terms of angular distance (its declination). Now,
as a double check, he measured the declination directly, which required finding the maximum height the star went above the horizon at Herrevad. If the nova had never gone higher in the sky than sixty degrees above the horizon at Herrevad, he could have used his sextant, which measured sixty degrees. However, the star went much higher. It reached its highest point at Herrevad only six degrees from
the zenith (the point of sky directly above Tycho’s head).

Tycho’s way of solving this problem, obvious as it seems in retrospect, was a true innovation. He turned the sextant around,
⁹
set it in a north window, recorded the star’s lower culmination—that is, how far above the horizon it was at its
lowest
point—and calculated the star’s declination from that. He was so pleased with this simple
ingenuity that he included a drawing of the sextant in that position much later in his book celebrating his instruments (
figure 3.1
).

Before a month had passed, Tycho had completed these tests to his own satisfaction and was confident enough to send his findings and his conclusions—that the star was not a comet and not in the sublunar region—to a few friends. He was not so sure of himself
as to send them to scholars in the more learned circles at the University of Copenhagen.

Figure 3.1: One of the first instruments Tycho designed was the sextant, used for measuring altitudes of bodies above the horizon, their azimuth (distance from the meridian), or their distances from one another. Two legs were joined with a hinge (right) so that the end of one moved along the arc (left) by means of a screw (
E
). There were sights at
C
and
K
. This drawing from
Astronomiae Instauratae
Mechanica
(probably of Tycho’s second sextant) shows it set in the north-facing window to observe the nova at its lower culmination. He put the hinge end (
I
) close to his eye and found the star through the two sights.

As his twenty-sixth birthday approached, rather than spend more time and effort reporting his study of the star, Tycho assigned himself an entirely different project that had
to be completed before the end of the year or not at all: putting together an astrological meteorological almanac for 1573. If the predictions in it were to have any impact, it was necessary to complete it before that year began.

Tycho’s introduction to his almanac was in the form of an “oration”
¹⁰
that provides a window into the mind of this eloquent, thoughtful, and well-educated young man.
He began it in traditional fashion by invoking Urania, astronomy’s muse in classical mythology, and proceeded to describe the universe as being Earth, seas, Sun, Moon, stars, animals, vegetables, and minerals, and the Creator as incorporeal, immense, eternal, incomprehensible, and omnipresent but not located in any single place. It was a good Lutheran beginning.

Tycho voiced the conviction
that humans were created in the image of God, by God, who put them on Earth at the center of the universe with a good view of the rest of it, so that through contemplation of the visible Creation they might learn something of the majesty and wisdom of the Creator. There was, Tycho declared, no better teacher of theology than the universe itself, and this was so even on Earth, where, with the exception
of the human soul, dissolution and change held sway. It was especially true in the celestial realms—immense, unchanging—so redolent of God’s power and intellect. In view of all this potential, Tycho lamented the ignorance of most people—even those who fancied themselves as authorities—about the heavens.

He continued by discussing his theory of meteorology, the theory that would underlie his
almanac: celestial events, especially of the Moon—because it is immediately next to Earth’s atmosphere—had, he thought, a strong influence on the weather. However, one should not put too much reliance on weather prediction based on celestial events because there were also local conditions on Earth, this realm of chance and change, and these conditions varied from place to place. Therefore, his hope
was not so much to predict the weather as
to
study the
discrepancies
between predicted and actual weather and find out more about how Earth and heaven were linked. Thus Tycho neatly sidestepped the danger that his predictions might not be correct. Discrepancies weren’t a problem; they were the leading edge.

Tycho also managed, in passing, to sneer at some of his contemporary astronomers and
to pay homage to Danish royalty. He said he was not one to sit snug by the fire and learn his astronomy from books and papers, and so he had decided to use his own observations rather than the Alfonsine (Ptolemaic) or Prutenic (Copernican) tables. Furthermore, because all people owe a great debt to their native land, he would use Copenhagen as his place of reference in establishing the meridian
and the horizon. In other words, for purposes of this almanac, King Frederick should think of himself as the center of the universe.

At the end of his introduction, Tycho listed the other manuscripts he had written on subjects related to the topic at hand. He had been busy. There were tables of the risings and settings of the Sun, Moon, and planets, their configurations for each day and each
lunar octad, and the predicted weather for each day of the year. He urged the need for systematic meteorological observations, and then he moved on with a flourish to quote Ovid on the joys of astronomy. Finally there was a verse he had written himself, lamenting that the demands of the world, of courtly life, and the intense cold of the north disturbed the serenity that a man required for contemplating
the stars.

As work on the almanac progressed, Tycho ran into a hitch. The almanac predicted an eclipse of the Moon on December 8, 1573. Investigating the astrological significance of this event, he found that it seemed to predict the death of King Frederick. Such a prediction was a matter of national security and certainly could not be announced straightforwardly in an almanac. On the other
hand, if the king died, it would be a feather in an astrologer’s cap to have predicted it. Tycho chose to clothe the announcement in rather garbled allegorical writing, which if necessary could later be interpreted, with
hindsight
and a little help from its author, to predict this catastrophe. (It did not occur.)

Soon after the new year began, Tycho carried the almanac manuscript to Copenhagen
along with several other manuscripts, including the one about the new star. To his astonishment, he learned that no one in Copenhagen had yet spotted the nova. He spoke of it while dining among friends at the home of Charles de Dançey, the French ambassador. Dançey thought Tycho was chiding them all for not watching the sky as closely as he was. Johannes Pratensis, who was on the faculty of medicine,
sniffed that other professors at the university could not have missed anything so dramatic. Tycho held his peace and allowed the conversation to move to other matters. When a clear night came, there was the star, and it was, as Tycho had told them, not at all like a comet. Amid the excitement, Tycho brought out the manuscript he had written about the star. Pratensis urged him to publish it.

Tycho had never published any of his manuscripts, nor was he thinking of publishing this one. Scholarly endeavors were beneath a man of his rank. A nobleman might read a book and acquire some learning thereby, but surely not write one. And if he did happen to write one, it was surely for the sport of it, not for public consumption. Tycho brushed off Pratensis’s suggestion on the grounds that his
manuscript was not polished enough, that he had never intended it to be widely read.

Pratensis did not give up. After Tycho had gone home to Herrevad, Pratensis sent him some reports written about the new star that had only recently reached Copenhagen from abroad with the spring thawing of the sea-lanes. When Tycho read them, claiming he did so only because he lacked anything to do while he
was ill, he was distressed by the incompetence of those who had studied the star, and particularly with claims that it was a comet only about as far away as twelve to fifteen times Earth’s radius.

Back in Copenhagen to check on work being done for him in an
instrument
shop, Tycho again encountered Pratensis. Only now did he admit to Pratensis (who was not a nobleman) what the real obstacle
was. Pratensis didn’t take offense, and suggested Tycho consult his powerful relative Peder Oxe. Oxe raised the possibility that Tycho might publish his manuscript anonymously, but Tycho returned home again with it still under his arm. In the end, Pratensis prevailed, and a letter from him became the preface to the published book.

Tycho’s decision to publish
De Stella Nova
¹¹
was a major turning
point. To his mind and the minds of his contemporaries, a life of serious scholarly pursuit and the life of a nobleman were incompatible. If he had got by so far, it was because he still seemed a young man who had not yet settled down seriously to either sort of life. However, it had in fact become far too late to follow the traditional path into knighthood, and government service—which was
still not out of the question—was simply not what he wanted. Hence he was already some distance beyond the pale even before he decided to publish this book. Nevertheless its publication was, for him, another significant and overt step away from orthodoxy.

De Stella Nova
began as a quiet, short treatise, not passionate or provocative. Tycho reported his studies and his findings and reasoned
about the location and the nature of the star. He also dealt with the purpose of it, a matter that greatly interested him—not merely its philosophical meaning but also its practical significance—for surely such a celestial event could not be completely irrevelant to humans. The astrological predictions turned out to be both difficult and dire, but more telling when it came to Tycho’s own future was
a last addition to the manuscript before it went to press in the spring of 1573, when the star was still visible but greatly dimmed.

Though the front of the book included a poem by one Professor Johannes Franciscus praising Tycho’s noble lineage, Tycho chose in his epilogue to cast scorn on the supposed glories of his class: feats of arms, association with kings, and the pursuit of frivolity,
wine, woman, and song. He declared himself unwilling to be held back by fear of what
people
would think of him, for his would be the greater and immortal glory of having improved astronomy beyond anything it had been before. His lineage was among the noblest, but he himself would take pride only in what he would accomplish himself.

Tycho concluded with an allegorical flourish. He portrayed
the goddess Urania commissioning him to find the position, distance, and meaning of the new star, but that was only the beginning. He also was charged to do the same for all the other stars, plot the paths of the Sun, Moon, and planets, and discover their influences on meteorological phenomena. Who, he asked, having such a vision, could ever lower his eyes to mundane interests? Tycho sent copies
of the book to friends, patrons, and scholars, but none to his family. Many years later, Johannes Kepler wrote
¹²
that if it signified nothing else, the nova of 1572 heralded the birth of an astronomer, the great Tycho Brahe.