by Peter Demetz
Tadeáš Hájek came from an old Czech family that resided near the Bethlehem chapel; his father, Simon, a Prague B.A. of 1509, collected rare manuscripts, wrote a treatise on correct Czech usage, and kept his library and the house open to traveling intellectuals, including a few disreputable alchemists. Tadeáš first went to Vienna to study music and astronomy, received his Prague B.A. and M.A. in the 1550s, and immediately went again to Vienna, then Bologna and Milan, to continue his studies. He was not a sedate scholar, at least not in his early years; in 1555 he taught mathematics for a while at the Carolinum and in the 1560s joined the imperial armies, fighting the sultan on the Hungarian front as a military doctor. As personal physician to Maximilian II and Rudolf II, he traveled a good deal between Vienna and Prague before settling in his father’s house, U Hájk. He certainly was not the comic busybody of wrinkled face who appears in Max Brod’s novel Tycho Brahe’s Path to God (Tycho Brahes Weg zu Gott, 1915), which though based on legitimate source materials is all too eager to cook up melodramatic scenes.
Tadeáš Hájek was the most eminent Prague scholar and scientist of the 1570s and 1580s, but since professors were still supposed to be celibate he did not really aim at an academic career and, indeed, married three times. The emperor assigned him to examine all the alchemists wanting to work in Prague, and, as a noted astronomer of European rank, he developed his own theory of the comets. He was also an expert in land surveying, much needed by the Bohemian mining industry (Kafka’s learned land surveyor in The Castle comes from good Bohemian stock), began to work on a topography of the Prague region, and walked through the countryside studying plants and flowers with a botanist’s eye. A true citizen of Prague, he also wrote a scientific treatise De cervecia (On Beer, published in 1564) and developed an early theory of oxidation. When he attended Rudolf’s coronation at Regensburg in 1576, he met there the young Danish aristocrat Tycho Brahe, who had not wanted to miss that chic event either, and gave him a folio of Copernicus’s Little Commentary, copied from a manuscript in his father’s Prague library. It was the beginning of a long friendship that, by 1600, made Rudolf’s Prague the world’s center of scientific astronomy.
Tycho Brahe came to Prague because he had decided to leave his native Denmark in protest against king, church, and society and was happy to accept the emperor’s invitation, ingeniously managed by Hájek through the chancellery. A scion of one of the most prominent families of the Danish kingdom, Tycho, haughty, condescending, and rich, was used to doing whatever he was doing in grand style; he once fought a duel with a fellow student (later Denmark’s royal chancellor) who had doubted his mathematical skills, and when part of his nose was cut off during the fight, in darkness and close to a cemetery, he had the missing part restored in gold and silver and attached to his face with a salve, which he always carried in a little pouch (that valuable part of his nose was missing when a scholarly commission opened his Prague tomb in 1901). He gave a brilliant account of the new star appearing in 1572, and the king of Denmark, who wanted to keep the famous man at home, in a magnificent gesture gave him the island of Hveen and ample subsidies to build a castle there—the Uraniborg Astronomical Institute—in which Tycho housed his growing family, his fool Jepp, his assistants, library, laboratory, a printing press, and his famous instruments, big and small, made by the best craftsmen of Europe. In Hveen, he devoted himself for twenty years to a continuous and surprisingly precise observation of the stellar skies, the last prince of astronomy without a telescope.
Tycho Brahe’s downfall was mostly of his own making; he had provoked the nobility by marrying a poor peasant woman named Kirstine, who bore him eight children and was to die in Prague; he never attended church services and dealt with his parsons as if they were his chattel; when the Hveen peasants, mistreated by him and sometimes put in chains, publicly protested, a court of nobles sided with the peasants and against him. Young King Christian IV, strapped for money and offended by his manners, canceled some of his privileges and substantially reduced his subsidies to Uraniborg; Tycho responded in an arrogant letter and the king never forgave him. In a fit of rage, Tycho packed a cumbersome wagon train with his family, friends, smaller instruments, books, and paraphernalia and, on April 9, 1597, left Hveen forever. He went into exile in Germany and then to Prague.
Tycho arrived in Prague in June 1599 and was lodged in the house of the vice-chancellor near Hradany Castle. Rudolf, not exactly known to be easily accessible, immediately received him and offered him a salary far in excess of what artists and other scientists received, along with a choice of three Bohemian castles to substitute for Uraniborg. Tycho selected Benátky, on the Jizera River northeast of Prague, which was well fitted, at least potentially, to serve as a new astronomical institute. Tycho praised the splendid and comfortable building, but it had to be altered, of course, to his scientific specifications, and he found himself promptly embroiled in a protracted conflict with the imperial administrator, who absolutely refused to spend money on the costly alterations; Tycho had to learn the difficult way that funds promised by the emperor were not automatically disbursed by the bureaucracy. His most important instruments, large and fragile, were still at Hveen, and not all the assistants showed up in time.
On a few occasions, Tycho was happy to accept the help of David Gans, a Prague Jewish scholar (who wrote about his visits at Benátky), yet he grievously underrated Gans’s scientific qualifications and thought he needed the help of a professional astronomer to take over specific tasks, collaborate with a team, and write, on his behalf, a few poisonous pamphlets against his scientific enemies, especially “the Bear,” or Ursus, one Reymers Baer, once a North German swineherd and now a self-taught and eminent scientist who happened to be the emperor’s court mathematician. The only candidate for the position was, in Tycho’s mind, a young Protestant mathematics teacher in Graz in Austria who had impressed the lord of Hveen by sending him an interesting treatise on planetary orbits, written without the use of sophisticated instruments. His name was Johannes Kepler, and when he came to Benátky and met Tycho, he immediately wanted to leave but did not know where to go.
Kepler was ill fitted to deal with tyrannical colleagues of high birth working in the light of the imperial sun. He was born in 1571 in the small Swabian town of Weil der Stadt (it was saved in May 1945 from Allied artillery fire thanks to the intervention of an erudite French officer who did not want to see Kepler’s birthplace destroyed) to a family that, according to his own views, was an odd bunch of misfits: his vicious father was a mercenary who ultimately left his family in the lurch; and his mother, garrulous and nosy, was, when she was seventy-three years old, accused of being a witch and was barely saved from burning by her son. Frail of health and strikingly intelligent, Kepler received a fellowship to train for the Protestant ministry, first at Maulbronn (like a character from a Hermann Hesse novel) and later at the University of Tübingen, where he studied with Martin Mästlin, who privately introduced him to the heliocentric ideas of Copernicus (Lutherans still violently opposed these, on biblical grounds). He never finished his theological studies, though he remained a theologian or rather a Pythagorean at heart, dreaming of God and the harmony of the universe; instead of becoming a minister he accepted a position as a teacher of mathematics at a Protestant school in Graz, in Catholic Styria. There he married Barbara Mühleck, “simple of mind and fat of body,” as he himself wrote, but well-to-do and of a respected family; though he did not have any students of mathematics, he made himself useful teaching rhetoric and Latin and yearly published popular calendars with meteorological advice for the peasants and a few prophecies about war, conveniently fulfilled by the Turks.
Teaching a class on July 9, 1595, he felt suddenly illuminated about the order of the universe and put down his ideas in a rambling treatise entitled Cosmic Mystery, in which he tried to suggest that the arrangement of the five planetary orbits could be explained by inscribing, into the spheres, the three-dimensional shapes of the five regular solids kno
wn to ancient philosophers. He felt so enthusiastic about his discovery that the divine order could be defined in these terms that he sent copies of his book to Galileo Galilei, who did not bother to respond, and to Tycho Brahe, who hastily answered, saying that he hoped to meet the young scientist one day. By 1598, Archduke Ferdinand of Austria decreed that all Protestants in Graz must get out within eight days, and though Kepler won a temporary reprieve, possibly because the Jesuits kept an eye on him as a potential convert of importance, he was happy to be invited to come to Benátky. He joined the retinue of a friendly Bohemian baron, left Graz on January 1, 1600, and, after a few days in Prague, was brought to Benátky by Tycho’s eldest, “not so much as a guest,” as his host wrote, but “as a welcome friend and colleague in the exploration of the skies.”
On February 3, the two exiles met for the first time face to face at Benátky Castle and, both sensitive to the uncertain circumstances in a foreign country, were immediately irritated by each other, the lord by the self-assurance of the poor colleague and the math teacher by Tycho’s overbearing manner. They both played their own games: Tycho expected to employ a scientist who would help him in his observations, mostly of the planet Mars, and support him in the construction of a geocentric system of his own (modified, of course, with the sun turning around Earth and the planets around the sun); Kepler, hungry for reliable data and the precision instruments dangled by Tycho before his myopic eyes, hoped to be able to show the heliocentric motion of the planets, including Earth, all arranged in harmonic concert by God. After a few days at Benátky, Kepler wrote to a friend that “old age was creeping up on Tycho, enfeebling his spirits and his forces”; he had gathered rich observations but needed “an architect” (namely, Kepler) to make appropriate use of all the materials. Life at the castle was chaotic if not “insane,” Kepler observed: builders were all over the place, the imperial administrator protested, and Tycho’s senior Danish assistants and a young Westphalian nobleman (who was to marry Tycho’s daughter Elizabeth to have a quick career at court) joined forces in an obvious intrigue to get rid of the new man as quickly as possible. The most important instruments were still on their way from Hveen via Hamburg and down the Elbe River to Litomice, and Kepler, desperately thinking of returning to Graz or going to Tübingen, wrote himself a little memorandum “on staying in Bohemia” (Tycho ultimately read this document), cataloguing in a rather miserly way what he wanted, paragraph by paragraph—a self-contained apartment, a bath, a kitchen, a chamber for his family, dry wood for the winter, sufficient food including meat, fish, wine, and bread, and permission to go to Prague whenever necessary, among other things. In early April tempers flared; Kepler raged “with the vehemence of a mad dog,” Tycho reported, and, on April 6, after a new outburst, Kepler returned to Prague to lodge with the friendly baron who had brought him there. However, he soon wrote a letter of apology to Benátky and waited for Tycho, who graciously came to Prague and took him back to the castle. All was forgiven. Kepler liked Prague now, “the eager contact of nations” and a neighborly feeling among people speaking German, “important to his wife.” Yet Prague was too expensive, and it was “impossible to live there.”
Kepler wanted to avoid Tycho as much as he could, and he spent many more months away from him than in his company. That summer he went again to Graz to settle his family affairs, but he was expelled in early August without further reprieve. Tycho once more implored him to return, and when he did so, everything had changed, for Emperor Rudolf had expressed the wish that Tycho work closer to the imperial residence. Tycho dutifully moved his entire establishment to Prague, first at a noisy tavern at the Nový Svêt, and by mid-February 1601 to the vice-chancellor’s house, which the emperor bought for him; Kepler was supposed to live there too. In the meantime, the instruments had arrived and were put in the loggias of Queen Anne’s summer castle, now to be an observatory. Kepler, who with his family moved in with Tycho’s clan, promptly had a nervous breakdown and a few psychosomatic complications as well; recuperating, he made another trip to Graz (his wife’s father had converted to Catholicism to save the family real estate), but when he returned to Prague there was not much time left for shared studies and observations. On October 13, 1601, Tycho Brahe was brought home in agony from a banquet at the town house of Petr Vok of Rožmberk. It was rumored that his bladder had burst because he did not want to leave the table before the host, and Kepler confirmed in his notes that the rumors were not far off the mark: Tycho held back his water beyond the demands of courtesy and “put politeness before his death”; when “he got home he was scarcely able to urinate.” Tycho was delirious for five nights with his uremia, and died on October 24, after he had composed his last words in flawless Latin: ne frustra vixisse videar (“let me not seem to have lived in vain”). He was buried, with pomp and circumstance, at the Týn Church, and a few days later Kepler was notified that he was appointed mathematician to his imperial majesty. He could not bear Tycho Brahe while he was alive, but he remained loyal to him and to his research for the rest of his life.
Emperor Rudolf granted his new court mathematician privileged access to all of Tycho’s papers and instruments, but Tycho’s family energetically staked out its own claims, especially the son-in-law, who sensed the financial possibilities. Kepler had to litigate and, often, to compromise. He had hoped that his salary would be equal or close to that of Tycho, but he had to do with less than a third, the exchequer was always in arrears, and the mathematicus was desperate for cash. The Keplers did not live in palatial splendor; after Tycho died, they moved to dwellings close to the New Town cattle market, definitely not a good address, and Kepler rightly complained of having to spend an hour walking to Hradany Castle. He later resided, possibly free of charge, in a university college at Ovocný Trh (Fruit Market) and, ultimately, in the Old Town in the Karlova Ulice close to the entrance to Charles’s stone bridge.
Kepler did not neglect his aristocratic connections, occasionally even condescending to deliver a horoscope, and made friends among Czech scientists and instrument makers who had been attracted to Prague. He probably did not have any opportunity to work with Tadeáš Hájek, who had died in 1600, but Martin Bacháek, rector of the Carolinum, and the physician Jessenius, who were involved in a tardy university reform, both sought his friendship and advice; he also knew Václav Budova of Budovec, political chief of the Czech Brethren in the Estates, who had traveled widely in the Near East and written a number of astronomical essays. Among other members of the Prague scientific community close to Kepler was the Swiss Jost Bürgi, who studied techniques of mathematical computation and early compiled tables of logarithms—unfortunately Lord Napier published his in 1614, six years before Bürgi followed with his own in Prague. Kepler was less happy with Galileo Galilei, whom he deeply admired. He had endorsed his telescopic discoveries enthusiastically and sight unseen, but when he implored him to let him work with one of his telescopes, Galileo did not answer his request; Kepler had to turn to the visiting elector of Cologne, who had received one from Galilei, and was allowed, at least from August 3 to September 9, 1610, to use the elector’s instrument. (Twentieth-century admirers of Galileo who take their information from Bertolt Brecht’s play might do well to read Arthur Koestler, who closely analyzed Galileo and Kepler’s relationship in solid and devastating detail.)
Kepler’s twelve years in Prague may have had their financial problems, but they were the most productive years of his life, and the emperor could well have been satisfied with a court mathematician, driven by an appetite for constant work, who published thirty treatises. It is possible that, in Prague, Kepler, who considered himself Tycho’s heir, put off at least for a time his Pythagorean visions about the harmony of the universe (he was to return to them when he moved to prosaic Linz, in Upper Austria) and followed, more intensely than in his early and later years, the essential necessity to observe and to calculate rather than to dream; his Prague research about physical astronomy and the fundamentals of optics cont
ributed more substantially to the development of modern sciences than to a magical vision of the universe. In Prague, he articulated two of his planetary laws—about the planets traveling in elliptical orbits and about the variations of their speed—and by asking questions about the cause of their movement made astronomy the physicist’s realm, preparing the way for Sir Isaac Newton’s universal laws of gravity.
Tycho Brahe and Galileo Galilei had used their instruments without systematic study of their efficiency, and Kepler, perhaps because he was born with impaired eyesight, was the first to develop a theory about the rays of light, the workings of refraction, and the function of the human eye; informed by his Prague colleague Jessenius about human anatomy, he sensed the structure of optical nerves. In a world in which astronomers sold horoscopes as a matter of course, Kepler declined, as early as 1601, to be an astrologer of the traditional kind who ascribed to planets an unmediated influence on man’s fortune, though he still believed that planetary aspects molded the human condition. Kepler did not want to get involved, and when he was asked by intermediaries to advise the emperor, he distinctly refused and insisted that “astrology should be kept away from the emperor’s mind.” It was the tragedy of Kepler the scientist that he had to accept employment late in life by General Wallenstein, who was not at all interested in scientific observation but eager only to enjoy prophecies of future victories.
The physician Johannes Jessenius de Magna Jessen has a special place among the scientists who, in difficult times, wanted to restore the ancient excellence of Prague’s Carolinum. He was a true Renaissance scholar, whom Czechs as well as Slovaks counted among their own, for more or less legitimate reasons. Jessenius came from a middle-class family originally in central Slovakia (then part of Hungary), but he was born (in 1566) in Silesian Breslau, where his father owned a tavern and married a local Silesian woman. In various university documents, the student was said to belong to the Polish “nation,” being a Silesian by birth, or, in Italy, to the “natio Germanorum”; often, when it was a matter of prestige, he called himself a “Hungarian knight” (so much for Mitteleuropa). Jessenius pursued his early philosophical and medical studies at Wittenberg and Padua, where he received his doctorate in 1591 after defending a thesis on afflictions of the gallbladder; being well trained and highly ambitious, he returned to Wittenberg as professor of anatomy and became rector of the university later. He too felt attracted to imperial Prague (though the nearly dormant university had little to offer); after placing his bets well by entertaining Typotius, the imperial court historiographer, and Tycho Brahe, in mid-June 1600 at the Carolinum he publicly dissected a male corpse delivered to him from the gallows. This was not the first Prague dissection but certainly the most formal and festive one, judging from the serried ranks of dignitaries and fashionable people who attended his performance, in which he proceeded, according to tradition, from the abdomen to the brain, occasionally praising the cool weather which fortunately diminished the stench of the rotting flesh.