Brahe, Tycho

(b. Skåne, Denmark [now in Sweden], 14 December 1546; d. Prague, Czechoslovakia, 24 October 1601)

astronomy.

The second child and eldest son of Otto Brahe and his wife, Beate Bille, Tycho (Danish, Tyge) was born at the family seat, Knudstrup. He had five sisters and five brothers, including his still–born twin. Otto Brahe was a privy councillor and later became governor of Helsingborg Castle. probably Tycho and Christine, whose last name is unknown and who was not of noble family, were never formally married, but they lived together from about 1573 to the end of his life. They had five daughters and three sons; their daughter Elizabeth married Tycho’s assistant, Franz Gansneb Tengnagel von Camp. Tycho’s best observing was done on the island of Hven from 1576 to 1597. His observations of the nova of 1572 and several comets forced abandonment of the traditional celestial spheres, and his observations of Mars enabled Kepler to discover the laws of planetary motion. Information about his observatory and observational techniques was widely disseminated, and his geoheliocentric system gained numerous supporters.

Tycho was brought up by his paternal uncle, Jörgen Brahe, and from the age of seven was taught Latin and the preparatory subjects by a tutor. From April 1559 to February 1562 he attended the Lutheran University of Copenhagen, where the ologians and faculty were under the influence of Melanchthon as well as Aristotle and the Scholastics. Tycho must have begun his studies in the Faculty of Philosophy by applying himself first to the trivium; his study of the arts probably began under the lecturers in pedagogy, who emphasized the writing and speaking of Latin. No doubt he received instruction in the articles of faith from the Lutheran catechism on Sunday mornings. He must have studied Greek grammar and Greek and Latin literature, and probably also dialectic, attending lectures in Greek on Aristotle’s Dialectics and lectures on the Latin rhetorical works and on Roman epistolary authors.

Since his family was a noble one, Tycho did not need a university degree to establish himself in a profession. Therefore, he must have entered on the study of the quadrivium as soon as he was able, without waiting to earn a degree. Ethics and singing were included in the university quadrivium; and at the chapter house of the cathedral, students practiced and heard lectures on singing. Also available lectures on hermonic theory, a mathematical discipline since the time of Pythagoras. From the lectures on the natural sciences and philosophy that Tycho may also have heard, he would have emerged as a convinced Aristotelian. By 1560 he was, no doubt, studying arithmetic, then Sacrobosco’s Sphaera and Peter Apian’s Cosmographia. His copies of the Sphaera, a medical handbook, an herbal, Gemma Frisius’ edition of Apian’s Cosmographia, and Regiomontanus’ Tabulae directionum are preserved.

In 1561 and 1562 Tycho was probably attending lectures on Aristotle’s Physics, Euclid’s Elements, ptolemy’s theory of the planets, and on astrology, which united astronomy with medicine. Tycho made friends with, and later wrote an epitaph for, Hans Fransden, from Ribe in Jutland (Johannes Franciscus Ripensis), who lectured on Hippocrates and Galen as well as on mathematics, acted as physician to the King, and prepared an annual astrological almanac. Tycho also made friends with Johannes Pratensis, who later became professor of medicine and whose copy of Ptolemy’s Almagest Tycho probably inherited in 1576. On 21 August 1560 the occurrence at the predicted time of a solar eclipse, although only partial in Copenhagen, turned Tycho toward observational astronomy, which was not part of the university curriculum. He immediately obtained a copy of Stadius’ Ephemerides, which is based on the prutenic Tables and, consequently, on the Copernican system.

So that he would be parted from friends interested in science and would study law, a necessary part of the education of a member of the nobility, Tycho’s uncle sent him to the University of Leipzig, where he arrived in March 1562. With him, as tutor, went Anders Sörensen Vedel, only four years his senior. Vedel had spent less than a year attending lectures on divinity and studying history at the university, but he was later to distinguish himself as a historian. Except for two short visits, Tycho remained away from his homeland until 1570.

At Leipzig, although Vedel tried to keep his charge busy with the study of law, Tycho’s interest in astronomy was not to be thwarted; and as late as May 1564 he was pursuing it secretly, while Vedel slept. During the daytime he attended to the studies prescribed by his uncle. He used what money he could save for the purchase of astronomical books, tables, and instruments. Not content with Stadius’ Ephemerides, he also obtained the Alphonsine Tables and Prutenic Tables, and used the Ephemerides of Giovanni Battista Carellus(1557). To learn the constellations, he secretly used a globe no bigger than a fist.

A conjunction of Saturn and Jupiter in August 1563 was later regarded by Tycho as the turning point in his career. Although equipped with only a pair of compasses, he recorded his observations relative to it. The discrepancy between the time of the observed closest approach of the two planets and that computed from the tables, about a month using the Alphonsine Tablesand a few days by the Prutenic Tables, greatly impressed Tycho. On 1 May 1564 he began observing with a radius, or cross staff, consisting of a three–foot arm along which could slide the center of an arm of half that length. Both arms were graduated. Bartholomaeus Scultetus subdivided the instrument for him by means of transversals. There was a fixed sight at the end of the longer arm that he held near his eye. To measure the angular distance between two objects, Tycho set the shorter arm at any graduation of the longer arm and moved a sight along the shorter arm until he saw the two objects through it and a sight at the center of the transversal arm. The required angle was then obtained from the graduations and a table of tangents. This instrument was not very accurate, but, since he could not get money from Vedel for a new one, he made a table of corrections to apply to it.

Tycho left Leipzig 17 May 1565 and traveled to Copenhagen via Wittenberg and Rostock. Of his family, only his mother’s brother, Steen Bille, showed any sympathy for his scientific interests. When his Uncle Jörgen died, 21 June 1565, there was no longer any reason for him to remain at home. He reached Wittenberg 15 April 1566 and began studies under Caspar Peucer. He left after five months, however, arriving in Rostock 24 September and matriculating at the university soon thereafter.

On 29 December 1566, in an unfortunate duel with another Danish nobleman, part of Tycho’s nose was cut off. This he replaced by what was long thought to be a composition of gold and silver, but probably had considerable copper content. When his tomb was opened 24 June 1901, a bright green stain was found on the skull at the upper end of the nasal opening.

At Rostock, Tycho met several men devoted to astrology and alchemy as well as to medicine and mathematics. He observed a lunar eclipse 28 October 1566 and a partial solar eclipse 9 April 1567. That summer he visited home, but was back in Rostock by 1 January 1568. He immediately began observations. although without an instrument until he used the cross staff 19 January. His last recorded observation in Rostock was 9 February. On 14 May 1568, King Frederick II of Denmark formally promised Tycho the first vacant canonry in the cathedral chapter at Roskilde, Zealand. He matriculated at the University of Basel in 1568 and, probably early in 1569, went to Augsburg via Lauingen in Swabia, where he met the astronomer Cyprian Leowitz. He entered into the intellectual life of Augsburg, where he made his first observation 14 April.

Among Tycho’s friends in Augsburg were Johann Baptist Hainzel, an alderman, and his brother, Paul, the burgomaster,¹ who helped Tycho arrange for the manufacture of a wooden quadrant, suspended at the center, with a radius of about nineteen feet. The divisions marked on the arc and a plumb line gave altitude measures. Tycho does not seem to have used it himself, and it was destroyed in a storm in December 1574. Tycho also designed a portable sextant, which he used and gave to Paul Hainzel, and ordered a five–foot globe. His last recorded observation in Augsburg was made in Hainzel’s presence 16 May 1570. At Augsburg he argued with Ramus, who advocated constructing a new astronomy based entirely on logic and mathematics, without recourse to any hypothesis. They agreed on the need for new and accurate observations before attempting to explain the celestial motions, and it is obvious that Tycho was aware of the need for good instruments to obtain those observations. He returned home in 1570, probably because of his father’s poor health. On the way, in Ingolstadt, he met Philip Apian, son of Peter.

Although at his father’s death, 9 May 1571, he and his brother Steen inherited Knudstrup, Tycho soon moved to Heridsvad Abbey, the home of his uncle, Steen Bille, where he devoted himself to chemical experiments until 11 November 1572. After sunset on that day, almost directly overhead, in the constellation Cassiopeia he noticed a star shining more brightly than all the others and immediately realized it had not been there before.

To measure the star’s angular distances from the neighboring stars in Cassiopeia, Tycho used a sextant similar to the one he had left with Hainzel. The two arms of seasoned walnut, less influenced by climate than other woods and lighter than metal, were joined by a bronze hinge. A 30° arc, graduated by individual minutes, without transversals, was fixed to one arm; the other arm could slide along the arc. Square metal sights with holes through the centers were attached at the ends of the arms. Tycho later described this instrument in the Mechanica and in the Progymnasmata, by itself and, as used for the nova observations, in the plane of the meridian, pointing out a window with the end of the arm where the arc was fixed (this time a 60° arc) resting on the sill while the end of that arm, near the joining of the two arms, rested on a post some five feet inside the window. To make sure that this arm was horizontal, it was moved until a plumb line, hanging from the end of the arc, touched a mark in the middle of the arm. The plumb line would show any change in position of the instrument, thus indicating the correction to be made to the observation.

To make sure that observations made the same night were made under the same conditions, Tycho left the instrument clamped in position between such observations. He measured the angular distance of the new star, at both upper and lower culmination, from the star Schedar (α Cassiopeia), which crossed the meridian at nearly the same time, and found no parallax. He measured the distance of the nova from nine stars in Cassiopeia and found no variation between observations. Had the new star been as close to the earth as the moon, a parallax of 58´30´´ would have been found. Tycho observed the star until the end of March 1574, when it ceased to be visible. His records of its variations in color and magnitude identify it as a supernova. At first clear white, with the magnitude of Venus at its brightest, it grew yellowish and diminished in brightness to that of Jupiter. By February and March it was of the first magnitude and reddish, in April and May of the second magnitude and lead–colored. Thereafter its color did not change. By August it was a third–magnitude star, fourth–magnitude by October, hardly more than fifth–magnitude at the turn of the year, and sixth–magnitude or less in February 1574.

Tycho concluded that the phenomenon was not an atmospheric exhalation and was not attached to the sphere of a planet, since it did not move contrary to the direction of the diurnal rotation, but that it was situated in the region of the fixed stars. He called it a star, not a comet, because, as the ancients asserted, comets are generated in the upper regions of the air, not in the heavens. He noted that it twinkled like a star and did not have a tail like a comet. It could not be a comet with its tail turned away from the earth because Peter Apian and Gemma Frisius had shown that the tail of a comet is turned away from the sun. Tycho thought it not impossible that the star would again cease to be visible, as he wrote in a brief tract published in 1573, while the star was still visible. This tract, dedicated to Johannes Pratensis, at whose urging it had been printed, included an exchange of letters between the latter and Tycho, a section on the astrological significations of the star, the introduction to an astrological calendar, and that part of the calendar dealing with the lunar eclipse of December 1573.

All over Europe scholars observed the star. Some, using crude observational procedures, such as holding a thread before their eyes, assured themselves that the newcomer did not move relative to certain known fixed stars. Such observations, showing the star to be supralunar, were widely appreciated as necessitating an alteration in cosmological theories.

Tycho’s scholarly treatise concerning the star, the Progymnasmata (1602), was the first volume of a proposed trilogy. The second chapter on planets having been printed and paged first, there was space in chapter 1 to describe the lunar theory, the complexity of which delayed publication of the volume. The work reprinted most of Tycho’s 1573 tract and gave his carefully compiled observations of the nova, discussing its position in space and its expected annual parallax if the Copernican system were true. Tycho attempted to calculate the real diameters of the sun, moon, planets, and the nova from his measurements of their apparent diameters. He estimated the maximum distance of Saturn as 12,300 semidiameters of the earth, the distance of the fixed stars as 14,000—not all at the same distance—and that of the new star as 13,000. His estimate of the real diameter of the new star at its first appearance was 7–1/8 times that of the earth. He assigned the diminution in light to actual decrease in size. Galileo pointed out ² the impossibly enormous sizes of the stars if Tycho’s estimates of their diameters were correct. The progymnasmata also reprinted, summarized, or criticized the works on the nova by others. Tycho deplored Hagecius’ use of clocks because of their inaccuracy. Because he was unable to observe the star with his sextant at upper culmination, Tycho used Hainzel’s observations made at Augsburg with the big quadrant.

Tycho’s observations of the nova were separately recorded. His journal of observations skips from one made at Helsingborg 30 December 1570 to his entries of three distance measurements between the nova and known fixed stars made with a parallax instrument 10 May 1573. There are entries for 14 August and for a lunar eclipse observed at Knudstrup 8 December, for observations at Heridsvad in March and April 1574, and at Copenhagen at the end of April and May. None appear for 1575.

In September 1574, in the first lecture of his course for young noblemen at the University of Copenhagen, Tycho spoke of the skill of Copernicus, whose system, although not in accord with physical principles, was mathematically admirable and did not make the absurd assumptions of the ancients, who let certain bodies move irregularly in respect to the centers of the epicycles and eccentrics. Doubtless, Tycho had Copernicus’ rejection of Ptolemy’s equant in mind. The influence of the stars on nature—seasons, tides, weather—seemed obvious. If forewarned, thanks to astrology, men could conquer the influence of the stars on themselves, but Tycho had reservations concerning public calamities.

Soon after completing these lectures, early in 1575, and wondering where to settle permanently, Tycho went first to Kassel, where he visited Landgrave William IV. The two men, convinced of the need for systematic observations, observed together for more than a week, Tycho with some of his own portable instruments and the landgrave with his quadrants and torqueta. They made an accurate determination of the position of Spica. Their discussion of the retardation of the sun near sunset spurred Tycho later to study refraction at low altitudes. The landgrave was so impressed by Tycho’s ability that he suggested to the Danish monarch that something be done to enable Tycho to pursue his astronomical studies in his native land.

Tycho’s next stop was Frankfurt am Main. There, at the book fair, he purchased many pamphlets on the recent nova. He next journeyed to Venice via Basel, where he contemplated settling, and then returned to Augsburg, inquiring about instruments he had ordered during his previous visit. Wherever he went, he met the leading astronomers and, whenever possible, inspected their astronomical instruments.

At Regensburg, where the future emperor, Rudolph II, was crowned King of the Romans, 1 November 1575, Tycho met Rudolph’s physician, Hagecius, who had written an excellent book on the nova of 1572. From him Tycho obtained a copy of Copernicus’ Commentariolus and a copy of a letter from Hieronymo Mugnoz to Hagecius about the new star. It is probable that at the same time Tycho presented Hagecius with a copy of his tract on that star. At Saalfeld, on the return journey, Tycho saw the manuscripts of Erasmus Rheinhold, who had prepared the Prutenic Tables. In Wittenberg, Tycho examined the wooden parallactic instrument, or triquetrum, with which Wolfgang Schuler had observed the nova after his earlier observations with Johannes Praetorius, made with an old wooden quadrant, had resulted in the finding of a large parallax that was inconsonant with the results obtained by the landgrave.

Tycho reached home near the end of 1575. In February 1576, possibly because of the landgrave’s recommendation, King Frederick II offered him the island of Hven in the Danish Sound and asked him to erect suitable buildings and construct instruments there. Tycho accepted, feeling that he could thus obtain in his native land the desired quiet and convenience. He immediately visited the island, and on 23 May a document was signed by the king conferring and granting in fee the island and its tenants and servants, with the rent therefrom; there was also the obligation to govern it in accordance with the law and to attend to the welfare of the inhabitants. Tycho was also given sufficient funds to augment his own, in order to erect a suitable residence and other buildings necessary to his work, and certain landholdings, the income from which, together with his own fortune, made it possible for him to lead an almost regal existence. From time to time additional sources of income were made available.

The island is roughly 2,000 acres in area. The inhabitants lived in a village near the northern coast and tilled about forty farms in common. Near the center of the island, at the highest point, about 160 feet above sea level, Tycho began construction of Uraniborg (heavenly castle), the edifice that was to be his home and observatory for more than twenty years. He made one observation of Mars in October 1576 and began observations of the sun 14 December. Although he probably moved into the building that winter, it was not completed until 1580, and even thereafter additions and alterations were made. On the island were the workshops of the artisans who constructed his instruments, a windmill, a paper mill begun in 1590 and completed in 1592, which could also be used to grind corn and prepare hides, and nearly sixty fishponds, one of which, for the use of the mill, was secured by a large dam.

The main building was erected exactly in the center of a square enclosure the walls of which were about 255 feet long, eighteen and one–half feet high, and seventeen feet wide at the base. At the center of each wall was a semicircular bend about seventy–six feet in diameter that enclosed a pavilion. There were gates at the eastern and western corners, and above the gates were kennels in which two English watchdogs were kept to warn of arrivals. At the northern corner was a small house for servants in the same Gothic–Renaissance style as the main house. A similar house at the southern corner housed a printing office. The press was installed in 1584. Four roads directed exactly to the cardinal points led from the main house to the gates and houses. Within the enclosure were herbaries and flower gardens and about 300 trees of various species.

The main house, too, was exactly square, its four walls, about fifty–one feet long and thirty–eight feet high, facing the four points of the sky. The rounded towers added on the south and north were eighteen and one–half feet in diameter, with eight and one–half–foot galleries encircling them. From the ground to the Pegasus weathervane, the house measured about sixty–four feet. Beneath the entire house was a cellar more than ten feet deep, divided into many rooms, and beneath the towers were the well and arrangements for storing food. The original four corridors on the ground floor, which met at right angles, were later reduced to three so as to make possible the establishment, behind the furnace, of a small chemical laboratory, thereby lessening the need to go down to the large subterranean one. There were a fountain that could turn, sending water in all directions, and pipes and pumping apparatus to distribute water to rooms on both floors. On the ground floor there were also a library, a kitchen, a table for collaborators in each corner of the building, and spare bedrooms. The observatories were on the upper level, the larger southern and northern ones containing several of the important, large instruments—such as the azimuthal semicircle, Ptolemaic rulers, brass sextant and azimuthal quadrant, and parallactic rulers that also showed azimuths. An octagonal gallery contained one of the globes on which an instrument could be placed and turned in all directions. At the very top of the house were eight bedrooms for assistants.

About a hundred feet south and slightly east of Uraniborg a separate observatory, Stjerneborg (castle of the stars), constructed about 1584, housed additional instruments in five subterranean rooms. Stone columns outside could be used to support Ptolemaic rulers or the portable armillae. There were also places for globes on which instruments could be placed and turned. In this building was a study with only the vaulted roof and the top of the walls above ground. On the ceiling was depicted the Tychonic system, and on the walls were the portraits of Timocharis, Hipparchus, Ptolemy, al–Battānī, King Alfonso X of Castile, Copernicus, Tycho, and the still unborn but hoped–for descendant, Tychonides, each with a legend beneath it—that for Tychonides expressing the wish that he would be worthy of his great ancestor.

The accuracy of the observations depended on the instruments and the care with which they were used. Although Tycho’s were without magnification, error was minimized by their huge size and by the graduations carefully marked on them to facilitate angular measurements on the celestial sphere, altitudes, and azimuths. Tycho checked instruments against each other and corrected for instrumental errors. Unfortunately, he considered refraction negligible at altitudes above 70°. He observed regularly and achieved an accuracy within a fraction of a minute of arc, an accuracy unsurpassed from the time of Hipparchus to the invention of the telescope.

In the library was the globe, almost five feet in diameter, ordered from Augsburg. Tycho filled the cracks, restored the spherical shape with pieces of parchment, tested it for two years to see whether it would retain its shape and whether it would withstand the seasonal temperature changes, then covered it with brass sheets and again had it smoothed. On it he engraved the zodiac and the equator with their poles and, using transversal points, divided each degree of these circles into sixty minutes. The globe could be turned on an axis through its poles inside the meridian and horizon circles that were mounted on it and that were divided into degrees and minutes. A vertical brass quadrant marked in degrees and minutes indicated altitudes as well as azimuths along the horizon. On this globe, over the years, Tycho marked the exact positions, referred to the year 1600, of the fixed stars that he observed. He also investigated the planet motions with reference to this globe.

In the southwest room on the ground floor at Uraniborg, affixed to a wall in the plane of the meridian, was Tycho’s most famous instrument, the mural quadrant with a radius of about six feet. The degrees marked off on its arc were so far apart that each minute was divided by transversal points into six subdivisions of ten seconds each, making it possible to read off measurements of five seconds. In a wall pointing exactly east and west, and over the center of the quadrant, was a square hole that could be opened and closed and that contained a brass cylinder along both sides of which the observer could sight, using one of two pinnules on the quadrant. Each pinnule had a square plane the width of which was exactly equal to the diameter of the cylinder. Each side of the plane had a slit for use in determining a star’s altitude and meridian transit at the same time. To determine the altitude alone, which was done to the sixth of a minute, an observer looked through the upper and lower slits and the corresponding sides

of the cylinder, and an assistant entered the reading on the record. A third person watched two clocks when the observer at the pinnule signaled, and the time was noted in the ledger. Two clocks that gave seconds as accurately as possible and could be checked against each other were necessary. Tycho had four. Elsewhere he expressed his distrust of clocks, preferring to check the time by observation. Despite his faith in this quadrant, he also consulted other large instruments.

Inside the quadrant’s arc, for ornamental purposes, was painted a life–size portrait of Tycho seated at a table, with arm outstretched as though pointing to the cylinder. In a niche in the wall, above and near the head, was a brass globe fitted with interior wheels. It could turn to imitate diurnal rotation and to show the paths of the sun and moon and the lunar phases.

The smaller southern observatory housed a brass armillary instrument with four armillae, or rings; the smaller northern observatory, another with three armillae. In the northern tower were the sextant with which one observer could measure distances, the bipartite arc for measuring small angular distances, and the sextant with which Tycho had observed the nova. Among his other instruments were several smaller quadrants and sextants of various designs for various purposes, an astronomical radius, an astronomical ring, a small astrolabe, an azimuth semicircle, and some parallactic or ruler instruments, one of which had belonged to Copernicus.

In these fantastically ornate but exceedingly useful observatories, Tycho watched the skies and trained his assistants. Some of the larger instruments could not have been used without their aid. Among these assistants were Peter Jacobsøn Flemløs, Longomontanus, Elias Olsen, Gellius Sascerides (who stayed six years), Otto Islandus (Oddur Einarsson, who was bishop in Iceland), and Willem Blaeu (who later made excellent maps and globes). Paul Wittich, who was an assistant at Uraniborg in 1580 and who, at Kassel in 1584, described Tycho’s instruments, including the transversal divisions, so impressed the landgrave that he had his instrument maker, Joost Bürgi, alter his instruments to conform to the description. Wittich was probably largely responsible for the development of the prosthaphaeretic method (from πρóσθεσις [addition] and ἀøαἰρεσις [subtraction] for simplifying trigonometrical computations by replacing multiplications and divisions with additions and subtractions. This is the basis of the set of rules for solving plane and spherical triangles, Triangulorum planorum et sphaericorum praxis arithmetica, drawn up, without proof, by Tycho and made available in numerous manuscript copies for the use of his assistants. Wittich also revealed this method at Kassel, to the annoyance of Tycho; he was even more annoyed, however, by the inclusion of the first two rules in a book by Nicolai Reymers Bār (Ursus), printed at Strasbourg in 1588. Afterward the method was further developed by other mathematicians. Ursus had visited Hven in 1584. Tycho was also visited by members of the nobility, possibly including Frederick II and certainly Frederick’s son, the future Christian IV (1592), as well as James VI of Scotland, the future James I of England (1590). Christoph Rothmann, Landgrave William IV’s mathematician, was there from 1 August to 1 September 1590.

Although Tycho saw no objection to the adoption of the Gregorian calendar by the Protestant world, since questions of theology were not involved, he does not seem to have used it until early 1599, when, on the Continent, he began to date his letters in the new style. His first observation so dated was made 22 July of that year.

From Hven, Tycho carried on a vast correspondence that kept alive the personal contacts made in his student days, apprised the scholarly world of his work, and provided him with the observations of others for comparison with his own. Although Tycho and William IV never met again after Tycho’s 1575 visit to Kassel, in later years they exchanged letters, sending each other records of their observations. The correspondence, including letters between Tycho and Rothmann, was printed at Uraniborg in 1596. It begins with data concerning the comet of 1585 and largely concerns the techniques of observation, the instruments used, and their divisions. Appended is a description of Hven, with its observatories and instruments. The majority of Tycho’s other letters, written between 14 January 1568 and 30 April 1601, first appeared in print in the Opera omnia. They provide a survey of observational astronomy in the last three decades of the sixteenth century, having achieved that dissemination of ideas which is now the province of learned journals.

Shortly after sunset on 13 November 1577, Tycho noticed, for the first time, a large comet with a very long tail. Although he later heard that the comet had been seen in the Northwendic Sea on 9 November, in his opinion it had begun with the new moon that had occurred shortly before, on 10 November at one hour after midnight.³ He observed from 13 November to 26 January, by which time it was barely distinguishable. He used a radius and a sextant, and occasionally a quadrant with an azimuth circle—the larger instruments were not yet all installed. He fixed the quadrant in the meridian. Shortly after the comet ceased to be visible, he described it in a short German tract, first published in 1922.⁴

Five hours after noon on 13 November, Tycho found the comet 26°50´ from the bright star in Aquila and 21°40´ from the lowest star in the horn of Capricorn, toward which the tail was stretched. Using trigonometry, he computed the comet’s position as 7°15´ in Capricorn, with a declination of 8°20´ north of the ecliptic. In the next twenty–four hours it moved 3°30´ in its circle. Having found it moved more rapidly in the beginning, Tycho decided it had moved 4° in its circle each of the days before he saw it, at new moon having been near the ecliptic beneath the twenty–fifth degree of Sagittarius in the line of the Milky Way, which he considered the place whence comets usually come. He traced the comet’s path from west to east. It had described a quarter of a great circle from the twenty–fifth degree of Sagittarius in the ecliptic, intersecting the equator at an angle of 34° at a point 300°40´ from the vernal equinox. Its rate of motion gradually decreased, so that in the end it moved only 20´ in a day, or 4°20´ from 13 January to 26 January. Its tail, 22° long in the beginning, gradually became smaller and shorter, and could scarcely be seen in January. Tycho used the direction of comets’ tails as evidence that the tails are merely solar rays transmitted through the head of the comet, an argument against Aristotle’s theory of the formation of the tail out of “dry fatness.”

In the first chapter of the untitled German tract, Tycho described Aristotle’s theory of comets and objected to it on the grounds that the star in Casiopeia four years before had been supralunar, having had no parallax and having remained stationary like the fixed stars, for which reasons many had abandoned the Aristotelian theory in favor of the belief that something new can be born in the heavens. Tycho suggested that other comets could be born there, and are not composed of dryness and fatness pulled up from the earth. He said that Aristotle’s proof had been based on meditation, not mathematical observation or demonstration, whereas comets are generated in the heavens.

Tycho referred frequently to his still incomplete Latin work on the same phenomenon, considering the two works as serving different purposes. The German one was intended for a wider audience than could be reached by a work in Danish, but it was meant for a less skilled audience than the one for whom the Latin work was written. Because it could reach only the literate, the German work would have an intelligent audience, but not one expected to be trained in mathematics. Repeatedly Tycho referred to the mathematical explanations in the Latin work, which the “masters” could read and understand. Indeed, the numerical values, such an important part of the Latin work, are almost entirely absent from the German. Tycho’s main objective was to determine the comet’s distance from the earth as a means of refuting Aristotle. He was also concerned with the comet’s physical appearance—color, magnitude, and the direction of the tail.

As clearly as anything he wrote, this tract shows Tycho as a product of his times. Breaking with established tradition, he knew exactly where he stood in the historical development of astronomy. Moreover, the tract demonstrates how early and how fully he understood the implications of his break and stresses his insistence on putting observation above deduction by reasoning. Emphasis is placed on the comet’s lack of parallax and the resultant untenability of the so–called Aristotelian doctrine of solid spheres in an unchanging heaven. It hints at Tycho’s own system of the universe, on which he was already working. It deals at length with the astrological implications of this fiery sign, but secondarily to the observational revelations.

De mundi aetherei recentioribus phaenomenis (1588), on the comet of 1577, the second volume of Tycho’s proposed trilogy, was printed on his own press and is profusely illustrated with useful diagrams. Chapter 1 records in detail, day by day, each of Tycho’s observations of the comet. The next chapter gives his positional data, computed from his observations, for the comparison stars used in observing the comet. In chapter 3 the comet’s latitude and longitude for each day are derived by means of spherical trigonometry, using observed angular distances of the comet from certain fixed stars. The diagrams, but not the mathematical steps, are reproduced. Chapter 4 treats the comet’s right ascension and declination with respect to the equator, and chapter 5 deals with the portion of a circle described by the comet, ending with a table of its daily motion, latitude, longitude, right ascension, and declination (first southern, then northern) for 9 November 1577 to 26 January 1578. Chapter 6 treats the comet’s parallax as a measure of its distance from the earth and states that the comet was in the etherial rather than the elementary region and moved in a great circle. Tycho’s observations of the comet’s angular distance from certain fixed stars are compared with those of other observers in other localities. Chapter 7 deals with past writings about the direction of comet tails and with the 1577 comet’s tail, which was directed away from Venus. In chapter 9, however, Tycho states his opinion that this was an illusion, since it would seem more likely that the tail be directed away from the sun. Chapter 8 discusses the comet’s position in regard to the planetary spheres.

Since his observations of the nova of 1572 and the comet of 1577 had made him discard the reality of the spheres, Tycho included a description of his own geoheliocentric system of the universe. The comet, whose greatest elongation from the sun was 60°, moved about that body in a circle outside that of Venus, that part of the circle where Tycho observed the comet being closer to the earth than Venus was. Moreover, the comet’s orbit, inclined to the ecliptic at an angle of 29°15´, was not a true circle, but an oval. Chapter 9 is concerned with the actual size of the comet and its tail, the diameter of the head being 3/14 of the diameter of the earth, and the length of the tail in November being ninety–six semidiameters if turned from Venus. The tenth and last chapter summarizes in detail the observations of others, both of those who found the comet supralunar and those who thought they found it sublunar.

At least six later comets were visible to the naked eye before Tycho left his island. The comets of 1580, 1582, 1585, and 1590 were supposed to be treated in the third volume of the trilogy, but that volume was never written. Tycho observed the comet of 1580

from 10 October to 25 November and again on 13 December, after it had passed perihelion. On 12, 17, and 18 May 1582 he observed another comet. By 1585 his major astronomical instruments, including a large armillary instrument at Stjerneborg, had been installed. His excellent observations of the tailless comet visible in October and November of that year appeared in 1586 in the first book printed on the island, the Diarium astrologicum et metheorologicum of his assistant Elias Olsen. They were more fully preserved in manuscript and studied in detail in the nineteenth century. The comet of 1590 was observed at Hven the end of February and the beginning of March, whereas that of 1593 was not observed at Hven but at Zerbst in Anhalt (Seruesta Anhaldinorum) by one of Tycho’s former students, Christiernus Johannis Ripensis. Tycho saw the comet of 1596 in Copenhagen on 14, 15, and 16 July. More complete observations were made at Uraniborg on 18, 21, 24, and 27 July.

Hinted at in the German tract on the comet of 1577, probably first worked out by 1583, and first described in print in the 1588 Latin work on the comet of 1577, the Tychonic system was never presented in detail. In it the earth is at rest in the center of the universe, and there is still need for a sphere of fixed stars revolving in twenty–four hours. The planets circle the sun while the sun circles the earth. The orbits of Mercury and Venus intersect the orbit of the sun in two places but do not encompass the earth. The orbit of Mars also twice intersects that of the sun, but encloses the earth and its orbiting moon. The orbits of Jupiter and Saturn enclose the entire path of the sun.

Tycho prized parts of the Copernican doctrine or

at least acknowledged the abilities of its originator, but could not bring himself to accept a sun–centered universe. His reluctance to do so can be ascribed partly to his respect for Scripture and partly to his feeling of common sense, but largely to his inability to conceive of a universe so immense that an observer as accurate as he knew himself to be could not detect any stellar parallax, the necessary consequence of the earth’s motion around the sun. The Tychonic system was timely and gained acceptance in many quarters. It did not bring its author into conflict with the ologians, yet it cared for observed phenomena, including the motion of comets through space, which had necessitated Tycho’s rejection of the Aristotelian spheres. It could account for the phases of Venus, first observed by Galileo and not explicable by the Aristotelian and Ptolemaic schemes.

Just as Tycho was only one of a number of observers who stressed the supralunar position of comets and novae, so his compromise theory of the universe was only one of a number that accentuated the abandonment of Aristotelian tradition and helped prepare men to accept the Copernican doctrine. It is only natural, especially in the light of Tycho’s arrogant ways, that there was some feeling of rivalry, especially toward Ursus, who described a similar system.

In Aristotelian theory the planets were attached to spheres and rotated with them. The destruction of these solid orbs made it necessary to find a cause for the motion of the planets, and this cause was provided by the next generations of astronomers and physicists, the sun assuming an importance not accorded to it by either Copernicus or Tycho. Undoubtedly the traditional crystalline spheres would eventually have been discarded without the aid of Tycho’s work, but he speeded up the change.

Tycho presented his cosmologic views in his introduction to a pamphlet ⁵ on weather forecasting by his assistant Flemløs. To explain how the heavens influenced matters on earth and so could be used for prognostication, Tycho described his cosmology, but focused not so much on the system as on the way the heavens affect the earth. He maintained the concept of “free will” while conceding celestial influence. Accepting three elements—earth, water, and air—he theorized that air is the instrument by which the celestial region influences the terrestrial, with the animals and plants therein and, to a lesser extent, men (some more than others). Thus he voiced disagreement with traditional concepts while maintaining the validity of astrology and distinguishing it from astronomy.

Elsewhere Tycho criticized astrologers who drew improper conclusions based on superstition and error rather than astrology itself, which he considered a science for which both accurate knowledge of the course of the stars and experience gained from signs seen in the elementary world were needed. From the lunar eclipse observed during his stay in Leipzig, he predicted the wet weather that followed. Also while in Leipzig, he calculated Caspar Peucer’s horoscope, predicting the misfortunes that befell him, as well as his reestablishment. In Rostock, from the lunar eclipse of 28 October 1566, Tycho predicted the death of the aged Sultan Suleiman the Magnificent, but later learned that Suleiman had died before the eclipse. Tycho calculated horoscopes for the three sons of Frederick II; but, although he continued to prepare annual prognostications for his ruler, by 1588, if not earlier, he held them of little importance, preferring to devote himself to the restoration of astronomy.

The German tract on the comet of 1577 stressed the comet’s astrological significance, whereas the Latin work did not. In the Progymnasmata, the main part of the 1573 nova tract was reprinted, but not the section on the star’s signification. These differences can, no doubt, be explained by the differences in the intended audience and a change in Tycho’s point of view. Yet as late as 1598, in the autobiography included in the Mechanica, he said that both natural and judicial astrology are more reliable than one would think, provided the times are correctly determined and the paths of the celestial bodies and their entrances into the separate divisions of the sky are used in accordance with the observed sky, and their directions of motion and revolution are properly computed. He indicated that he had developed a method for this that he did not care to divulge.

In the Astrologia, Flemløs gave 399 short rules for weather prediction from the appearance of the sky, sun, moon, and stars, or animal behavior. However, the daily weather record kept at Hven from 1 October 1582 to 22 April 1597 was not published until the nineteenth century. It recorded the arrivals and departures of Tycho, his visitors, and students or assistants; and, although no instruments were used and precise times were not entered, it provided useful meteorological information for the area—frequency of wind, rain, snow, fog, hail, thunder, halos, and aurorae, and whether the sky was clear, semiclear, or covered. Some estimates were made of the force of winds.

Tycho’s main occupation on Hven was the redetermination of the positions of the fixed stars and the observation of the planets, the sun, and the moon for the purpose of improving the ory of their motions. For six years, beginning in 1582, the distance between Venus and the sun was measured with the triangular sextant, which required two observers. Simultaneously the altitudes, and occasionally the azimuths, of Venus and the sun were measured. The distance of Venus from selected bright stars near the zodiac was measured with the same sextant after sunset, altitudes and declinations also being noted. The motions of Venus and the sun between daytime and nighttime observations were considered in calculating the positions of the observed stars. A star’s declination was measured directly, but the difference in right ascension between the sun and a star was obtained by trigonometry. Using the right ascension of the sun as given in the tables, the right ascension of the star could be found. The stars were connected with α Arietis by distance measures. By suitable selection of observations, minimizing the effects of parallax and refraction, he determined the right ascension of α Arietis, and with this as reference, he determined the right ascensions of eight standard stars. Later he added three stars near the zodiac.

In determining the position of another star, a meridian quadrant or armillary was used to measure the declination, and a sextant was used to measure the distance from a known star. For the complete determination, two or three standard stars were used as reference. Included in the Progymnasmata (1602), before the section on the nova, are revisions of the solar and lunar theories and a catalog giving the positions of 777 fixed stars. Having indicated familiarity with the work of his predecessors, Tycho, using diagrams, described his observational methods and depicted the instruments used. In his later years he brought the list of stars to 1,000 by the less careful determination of the positions of 223 additional ones. The Tabulae Rudolphinae, prepared by Kepler in accordance with his modification of the Copernican system but on the basis of Tycho’s observations, did not appear until 1627. Included were logarithm and other tables, the most significant of which were those of the positions of the sun and moon and five planets, and of 1,000 fixed stars calculated for the year 1600.

When he had more instruments, Tycho used several quadrants simultaneously for repeated observations of the sun’s meridian altitude, begun 14 December 1576. From March 1582 he mostly used the great mural quadrant. He determined the equinoxes for the years 1584–1588, using the time when the sun was 45° from the equinoxes to determine the position of the apogee and the eccentricity of the orbit instead of using the solstice, the exact moment of which was difficult to find. He believed that the sun moved uniformly in an eccentric circle, but by 1591 he might have noted, from the motion of Mars, another inequality due to that eccentricity. He considered his tables of the sun’s motion to be accurate within 10´´ or at most 20´´. His values were 95°30´ for the longitude of the apogee with an annual motion of 45´´ and .03584 for the eccentricity of the orbit, the greatest equation of center being 2°3´15´´.

The difference in the colatitude as determined from his solar observations and his observations of the polestar led Tycho to investigate the effects of refraction, using the armillae at Stjerneborg, and to compose a refraction table. Unfortunately, he assumed the value of 3´ for the sun’s horizontal parallax. He also composed a refraction table for the stars. He erred in believing refraction negligible at 45° and over, but made a step forward in determining the refraction for an observation and in correcting the instruments.

Tycho’s handling of the lunar theory illustrates not only the accuracy of his observations and his awareness of the need to observe over long periods of time and over the whole course of the moon’s orbit, but also his computational prowess and talent for theory construction. His discoveries of new inequalities in both longitude and latitude stem from his efforts at accurate determination of eclipses and his interest in parallax. Making approximately 300 observations of the moon in different parts of its orbit from 1582 to 1595, he noted its position relative to known fixed stars, observing in such a way as to minimize the effects of parallax. In the Progymnasmata he recorded twenty–one lunar and nine solar eclipses ⁶. At his death all the important lunar perturbations, with the exception of the secular variation of the mean motion, were known.

Tycho made his first discovery regarding the moon’s motion in 1587, when preparing his observations of the comet of 1577 for publication. The comet’s position obtained from observations of its stellar distances differed by 21´ from the position computed from the lunar distance, suggesting some error in his theoretical position of the moon. Four lunar observations in August 1587 confirmed his suspicion that the inclination of the lunar orbit was 5°15´ instead of the previously accepted 5° of Ptolemy. When Tycho announced this finding in his book on the comet of 1577,⁷ he expressly interpreted it as due to a long–term change rather than as a correction of Ptolemy. But in 1595 he discovered that the inclination varied in the short term—that he had, by chance, observed the moon’s latitude in quadrature, whereas previous interest in the moon’s latitude had been focused on syzygy, where eclipses occur. To account for the semimonthly fluctuations of the inclination, Tycho let the pole of the lunar orbit describe a circle twice a month to bring the pole 5° from the ecliptic when the moon was in syzygy and 5°15´ from it in quadrature, and also to provide a smooth variation in between. Since this device implied an oscillation of the nodes along the ecliptic, Tycho sought and found empirical evidence that such an oscillation did occur, thus making what has been described as “a true deductive discovery.” From his determinations of the extreme values for the inclination of the orbit (4°58´30´´ to 5°17´30´´), Tycho deduced a value of 1°46´ for this nodal oscillation.

Tycho’s discovery of the third inequality in longitude began with his observation of the lunar eclipse of 1590, in which the moon reached opposition about an hour before the time he had computed. By 1595 he had isolated the cause of his difficulty and had determined the approximate value of the “variation,” the discovery of which he announced in his Mechanica.⁸ During the winter of 1598–1599 another refractory eclipse led him to a fourth inequality—the so–called annual equation with a period of a solar year.

Tycho’s theory was put into its finished form by Longomontanus in 1601 and was published in the Progymnasmata. In it the first inequality (4°58´27´´) was represented by a double epicycle, while the second appeared in the form of a hypocycle by means of which the center of the deferent was made to pass through the earth twice a month at syzygies and to reach its greatest distance from the earth at quadratures. The third inequality (40´30´´) was accounted for by letting the center of the large epicycle librate on the deferent in the period of half a synodic revolution. Since these mechanisms left no room for the fourth inequality, Longomontanus introduced it—only partially, and to Tycho’s expressed displeasure—by dispensing with the anomalistic component of the equation of time.

After the death of Frederick II, 4 April 1588, Tycho gradually lost the favor he had enjoyed at court. His own personality had much to do with this. He was arrogant, haughty with members of the royal family, neglectful of the welfare of the tenants on Hven, and careless in the maintenance of the public buildings on his fiefs. Although Hven had been conferred on him for life and he had some inherited wealth, the maintenance of his buildings and instruments required additional funds. Young King Christian IV, after gaining majority, did not seem to find that the astronomical work warranted the large expenditures. A quarrel with his former pupil Gellius Sascerides, who was engaged to his daughter Magdalene, put Tycho in an unpleasant light and may have contributed to his desire to leave Denmark. Besides, he may have wanted more opportunity for intellectual intercourse than he had on his island; and he may have hoped for patronage from Emperor Rudolph II, of whose interest in alchemy and astronomy he must have been aware through his correspondence with Hagecius and with Vice–Chancellor Curtius, who had written describing Clavius’ method of dividing instruments, which was similar to Vernier’s later, more practical one.

After 15 March 1597, the date of the last observation at Hven, Tycho’s instruments, printing press, chemical apparatus, and portable possessions were transported to his house in Copenhagen; the mural quadrant and three other large instruments were left behind. Little is known of Tycho’s activities in Copenhagen. Early in June he sailed for Rostock with his instruments, press, and other belongings, as well as his family an entourage, including Tengnagel, who had come to Hven in 1595.

On 10 June 1597 the Roskilde prebend was conferred on another. Tycho made an unsuccessful attempt at reconciliation with Christian IV and in October, at the invitation of Heinrich Rantzov, took up residence in the castle at Wandsbeck, near Hamburg. There he continued his efforts to have the king permanently endow Uraniborg. Tycho began observing again 21 October, using only a radius until February 1598, when he got some of his better instruments together. He observed the solar eclipse of 25 February 1598, and later he received records of observations by others and information that it had been observed from beginning to end at Hven. He observed two lunar eclipses and some meridian altitudes but concentrated on the planets. He was assisted by the mathematician Johannes Müller, from Brandenburg, who had visited Hven in 1596 and whom the electress of Brandenburg had asked Tycho to train in chemistry and the preparation of medicines. Among visitors at Wandsbeck was the astronomer David Fabricius.

Tycho now completed the Mechanica and dedicated it to Emperor Rudolph II. Excellent woodcuts accompany Tycho’s descriptions of his globe and of each of his instruments and its use. Also included are descriptions of Hven and its buildings, the instrument sights and the method of dividing by transversals, and a brief autobiography. From Wandsbeck he distributed a large number of manuscript copies of his star catalog, also dedicated to Rudolph.

Tycho’s eldest son brought the emperor the catalog, the Mechanica, and a letter expressing the hope that the astronomer could complete his work under the emperor. At the same time Tycho sent bound copies of the catalog to scholars and influential people, including Christian IV, to whom he also addressed a respectful letter. On 24 March 1598 Tycho wrote to Longomontanus, inquiring about Wittich’s books and manuscripts, and asked if Longomontanus had seen a recent publication by Ursus that Tycho did not consider deserving of refutation. He requested Longomontanus to join him at Wandsbeck, perhaps to continue work on the lunar theory.

Rantzov asked the elector of Cologne to use influence with the emperor and to try to interest Barwitz, the Austrian privy councillor, in Tycho’s cause. Tycho himself wrote to Hagecius, hoping he would influence the emperor and the vice–chancellor. He also investigated the possibilities for settling in the Netherlands. Shortly after the middle of September 1598, having been assured that he would be welcome in Prague, Tycho left Wandsbeck with his sons, his students, and a few instruments. Longomontanus reached Wandsbeck after Tycho’s departure but accompanied Tycho’s ladies as far as Magdeburg. He returned to Denmark, however, and did not rejoin Tycho until January 1600. An epidemic of pestilence and dysentery in Prague caused Tycho to remain in Dresden. The first week in December, he moved to Wittenberg.

On Tycho’s arrival in Prague in June 1599, he was escorted to the home of the late Vice–Chancellor Curtius and was soon granted an audience by the emperor, who arranged for him to receive financial support. Tycho had only a few instruments with him, but tried to display them in the same splendid setting they had had at Uraniborg. He never again got his instruments properly set up, nor did he make any important observations. He observed the end of a partial solar eclipse 22 July. He did not want to remain in the city of Prague and soon took up residence in the castle of Benatky, one of those offered him by the emperor. On a hill above the Iser about twenty–two miles northeast of Prague, Benatky had unobstructed views of the skies. It was small, but he altered it to fit his needs, building a laboratory and an observatory and planning to set up the instruments in separate rooms. He had difficulty, however, in obtaining the necessary funds. His family arrived, and he sent his eldest son for the four large instruments left at Hven. These, as well as the instruments and books that Tycho had brought with him as far as magdeburg, were delayed in transit, the latter not arriving in Prague until November 1600.

Tycho’s assistants in Bohomia included Longomontanus (January 1600–4 August 1601), David Fabricius (June 1601), Johannes Müller (March 1600–Spring 1601), and Melchior Joestelius, a mathematician from Wittenberg, who returned there before June 1600 but who was probably responsible for completing the solution of triangles by the prosthaphaeretic method that Tycho said he and Joestelius had done together. The assistant most important for the future of astronomy, Johannes Kepler, a firm believer in the heliocentric system, arrived at Benatky 3 February 1600. Longomontanus was working on Mars, but that planet was eventually turned over to Kepler. The relations between Tycho and Kepler were frequently strained.

In the summer of 1600 Tycho moved to Prague and set up his instruments in the Belvedere, a villa belonging to the emperor and close to the castle. Kepler, who had returned to Graz to settle his affairs and call for his family, arrived in Prague in October. Until April 1601 he was mostly engaged, at Tycho’s behest, in a refutation of Ursus, although the latter had died in August 1600. Because of Tycho’s death, the refutation remained unpublished until the nineteenth century. The emperor bought Curtius’ house, and Tycho took possession of it in February 1601. The Kepler family moved there, too, although Kepler returned to Graz on business from April to August 1601. Kepler worked on the ories of Mercury, Venus, and Mars, and tried to persuade Tycho of the impossibility of describing the motion of the sun (or of the earth) as uniform in an eccentric circle.

Tycho died after an illness of eleven days, probably caused by prostate difficulties. He was buried with pomp on 4 November in the Tyn Church in the city’s main square, his tomb marked by an upright slab bearing a life–size raised image of him with an inscription. On his deathbed, Tycho begged Kepler to complete the Rudolphine Tables as quickly as possible and expressed the wish that their theory be demonstrated in accordance with the Tychonic system.

Kepler did not obtain Tycho’s instruments. They were stored beneath the Curtius house, and their subsequent fate is uncertain. The great globe was placed in the Round Tower in Copenhagen in the middle of the seventeenth century, having first been in Silesia, at Rosenborg Castle in Denmark, and at the University of Denmark. Some instruments must have been carried off during the Thirty Years’ War, for they were discovered in a castle in Sweden in the twentieth century. Kepler had difficulties with Tengnagel and Tycho’s other heirs over the records and publications. Giving him due credit, Kepler used the records of Tycho’s observations, especially of Mars, to derive the laws of planetary motion, announcing the first two in his Astronomia nova (1609) and the third in the Harmonices mundi libri V (1619). He published Tycho’s progymnasmata (1602), already partly printed at Uraniborg, and the Tabulae Rudolphinae (1627), in conformity with a heliocentric system.

Thus Tycho’s accurate observations of the positions of the sun, moon, stars, and planets provided the basis for refinements of the Copernican doctrine. Had the observations been as accurate as Tycho considered them, or less accurate than they actually were, the history of astronomy would have been different. But they provided the suitable degree of accuracy at the critical time. A discrepancy of 8´ of arc between theory and observation led Kepler to his reformation of astronomy.

NOTES

1.Opera omina, II, 342–343; V, 81, Dreyer (1890), p. 30, erred in describing the Hainzels.

2.Dialogue Concerning the Two Chief World Systems, Stillman Drake, trans. (Los Angeles, 1962), pp. 358 ff.

3. Pingré Cométographie, I (1783), 511, says the comet was seen in Peru as early as 1 November.

4.Opera omnia, IV ².

5.En Elementisch oc JordischASTROLOGIA , 1591.

6.Opera omnia, II, 98

7.Ibid., IV, 42.

8.Ibid., V, 111.

9. A broadside, item 3026 in Zinner, Geschichte und Bioliographie (Leipzig, 1941), is not included.

BIBLIOGRAPHY

There is no complete bibliography of the vast literature dealing with Tycho Brahe’s life or work. Neither is there a printed list of his writings. Also lacking is a bibliography of works with references to him. Nevertheless, the following bibliography is selective.

The impact of Tycho’s work must be studied in the writings, both printed and MS, of his contemporaries and immediate followers. Works by and about Kepler, including the recent ones, are of particular importance, but the writings of less important seventeenth–century men also give evidence of the influence of Tycho in Europe and the East. In honor of the 300th anniversary of Tycho’s death (1901) and the 400th anniversary of his birth (1946) much was written, both scholarly and popular.

I. Original Works. Tycho’s writings were collected as Tychonis Brahe Dani Opera omnia, J. L.E. Dreyer, ed., 15 vols. (Copenhagen, 1913–1929), which includes charts, diagrams, facsimiles, maps, portraits, and tables, and is copiously annotated.⁹

His books on the nova of 1572 are De nova et nullius aevi memoria prius visa stella… (Copenhagen, 1573; facs. ed., 1901), trans. into Danish by Otto Gelsted as Tyge Brahe: Den ny Stjerne (1572)… (Lemvig, 1923), and partially trans. into English by John H. Walden in Harlow Shapley and Helen E. Howarth, eds., A Source Book in Astronomy (New York–London, 1929), pp. 13–19; and Astronomiae instauratae progymnasmata… (Prague, 1602; Frankfurt, 1610). A number of seventeenth–century tracts summarized or translated excerpts from the Progymnasmata, the most important work on the 1572 nova.

Tycho’s book on the comet of 1577 is De mundi aethereirecentioribus phaenomenis… (Uraniborg, 1588; Prague, 1603; Frankfurt, 1610). Part of ch. 8 is trans. in Marie Boas and A. Rupert Hall, “Tycho Brahe’s System of the World,” in Occasional Notes of the Royal Astronomical Society, 3 , no. 21 (1959), 252–263 (trans. on pp. 257–263).

His letters have been brought together by Dreyer in the Opera omnia and in Tychonis Brahe Dani Epistolarum astronomicarum… (Uraniborg, 1596; Nuremberg, 1601; Frankfurt, 1610); Tychonis Brahei et ad eum doctorum virorum epistolae…, F.R. Friis, ed., 2 vols. (Copenhagen, 1876–1909); and Wilhelm Norlind, Ur Tycho Brahes brevväxling, från Latinet (Lund, 1926), 23 letters trans. into Swedish, with notes, and “Några Anteckningar till Tycho Brahes brevväxling,” in Nordisk astronomisk tidsskrift (1956), no. 2, 51–55.

Tycho’s book on his instruments is Astronomiae instauratae mechanica (Wandsbeck, 1598; Nuremberg, 1602), also in facsimile of 1598 ed., B. Hasselberg, ed. (Stockholm, 1901); the 1598 ed. was printed in Rantzov’s castle near Hamburg on Tycho’s press by Philip de Ohr. For trans., see Hans Raeder, Elis Strömgren, and Bengt Strömgren, eds. and trans., Tycho Brahe’s Description of His Instruments and Scientific Work… (Copenhagen, 1946).

His tables are in Historia coelestis…, Lucius Barrettus (pseud. of Albert Curtz), ed. (Augsburg, 1666). Kepler’s Tabulae Rudolphinae… (Ulm, 1627) are based on Tycho’s observations and the Copernican–Keplerian system of the universe.

The MS material has been thoroughly used by Dreyer in his biography and in the Opera omnia, and MSS for which he gives bibliographical details will not be described here. For his biography Norlind has examined MS sources; see also his “On Some Manuscripts Concerning Tycho Brahe,” in The Observatory, 78 , no. 903 (1958), 73–75. It is impossible to list here MSS in which Tycho is discussed, e.g., Gregoriana (Rome) 530, ff. 208–211, a letter dated 26 January 1601 from Magini in Mantua to Clavius in Rome, which speaks of Tycho’s book on the star of 1572; or Ambrosiana (Milan) D 246 inf. 83r, the fragment of a letter from Padua in 1592 that speaks of Tycho and Galileo, who had just begun his lectures there. Nor need the location and description of the presentation copies of the Mechanica and the MS copies of the catalog of stars be listed.

Letter no. 102 (Opera omnia, XIV, 68) is at The Historical Society of Pennsylvania, Philadelphia, as are an undated autograph and an autograph dated 10 August 1594. Presumably the letter from Tycho to T. Saville (1 December 1590) cited in the British Museum’s Sloane Collection catalog of 1782 is the same as the museum’s Harleian 6995, 40 used by Dreyer (Opera omnia, VII, 283–285). The same catalog of the Sloane Collection lists an MS of the Demundi aetherei…, Two letters in the hand of a sixteenth century scribe are in the possession of the author: Tycho to Caspar Peucer, 13 September 1588, 23 leaves (Opera omnia, VII, 127–141), and Caspar Peucer to Tycho, 10 May 1589, 9 leaves (Opera omnia, VII, 184–191).

An interesting summary (from Padua) of Tycho’s work, Epitome de restitutione motuum solis ac lunae, et de novastella anni 1572, is preserved in Venice (Marciana lat. Cl. VIII, Cod. XXXVII, 3493). In Milan (Ambrosiana D 246 inf. 84r–87v) there are part of the Mechanica and epigrams to Scaliger.

II. Secondary Literature. The best single treatment of Tycho’s life and work is J. L.E. Dreyer, Tycho Brahe, a Picture of Scientific Life and Work in the Sixteenth Century (Edinburgh, 1890; repr. New York, 1963). This is based on and cites the sources available in 1890, and forms the basis for this article. Except for Tycho’s major publications, works cited by Dreyer are not in this bibliography, although they include much material to which the reader may want to refer, such as Gassendi’s biography of Tycho (1654) and Tycho’s Opera omnia, (1648), which presents the Progymnasmata and De mundi aetherei rather than the complete works. More recent biographies are John Allyne Gade, The Life and Times of Tycho Brahe (Princeton, 1947), with a bibliography that, while not selective, includes some useful items that appeared after Dreyer’s work; and Wilhelm Norlind, Tycho Brahe. Mannen och verket. Efter Gassendi overs. med kommentar (Lund, 1951); Tycho Brahe (Stockholm, 1963); and Tycho Brahe. En biografi. Med nya bidrag belysande hans liv och verk (Lund, in press), with a summary in German.

The island of Hven is discussed in the anonymous “Stjerneborg”, in Nordisk astronomisk tidsskrift, n.s. 20 , no. 3 (1939), 79–99; Francis Beckett and Charles Christensen, Uraniborg og Stjaerneborg (Copenhagen–London, 1921), text in Danish, summary and explanation of plates in English, title also given in English: Tycho Brahe’s Uraniborg and Stjerneborg on the Island of Hveen; C. L.V. Charlier, Utgräfningarna af Tycho Brahes observatorier påön Hven sommaren 1901, which is Acta universitatis Lundensis. Lunds universitets årsskrift, 37 , afdeln. 2, no. 8 (Lund, 1901); John Christianson, “The Celestial Palace of Tycho Brahe”, in Scientific American, 204 , no. 2 (1961), 118–128; Charles D. Humberd, “Tycho Brahe’s Island”, in popular Astronomy, 45 (1937), 118–125, which reproduces the Cologne map of 1586 and translates the Latin explanations inserted on the map and its back; William Lengert, Tycho Brahe–tryck (Malmö, 1940); N.A. Moøller Nicolaisen, “Et Tycho Brahe–minde paa Hven,”, in Nordisk astronomisk tidsskrift, n.s. 11 , no. 3 (1930), 122–128; “Tycho Brahes mølledaemning paa Hven”, ibid., no.4, 173–175; “Tycho Brahes papirmoølle”, ibid., n.s. 14 , no. 3 (1933), 85–95; and Tycho Brahes papirmølle paa Hven. Udgravningen 1933–34 og forsøg til rekonstruktion… (Copenhagen, 1946); Harald Mortensen, “Johnnes Mejers kort over øen Hven”, in Skäne årsbok (1925), pp. 9–16; and “Et Tycho Brahe–minde paa Hven”, in Nordisk astronomisk tidsskrift, n.s. 11 , no. 4 (1930), 172–173; and Lauritz Nielsen, Tycho Brahes bogtrykeri. En bibliografisk–boghistorisk undersøgelse (Copenhagen, 1946).

Works treating other subjects are Joseph Ashbrook, “Tycho Brahe’s Nose”, in the column “Astronomical Scrapbook”, in Sky and Telescope, 29 , no. 6 (1965), 353, 358; F. Burckhardt, Zur Erinnerung an Tycho Brahe 1546–1601…. (Basel, 1901); John Christianson, “Tycho Brahe at the University of Copenhagen, 1559–1562”, in Isis, 58 (1967), 198–203; and “Tycho Brahe’s Cosmology From the ‘Astrologia’ of 1591”, ibid., 59 (1968), 312–318; J. L.E. Dreyer, “Note on Tycho Brahe’s Opinion About the Solar Parallax,” in Monthly Notices of the Royal Astronomical Society, 71 , no. 1 (1910), 74–76; “The Place of Tycho Brahe in the History of Astronomy”, in Scientia, 25 , no. 83–3 (Mar. 1919), 177–185; and “On Tycho Brahe’s Manual of Trigonometry,” in The Observatory, no. 498 (Mar. 1916), 127–131; Antonio Favaro, “Ticone Brahe e la corte di Toscana,” in Archivio storico italiano, 5th series, 3 (1889); Edvard Gotfredsen, “Tycho Brahes sidste sygdom og død” (“Tycho Brahe’s Last Disease and Death”), in Københavens Universitets medicinsk-historiske museum; Arsbereining 1955–1956; Poul Hauberg, “Tycho Brahes opskrifter paa Laegemidler,” in Dansk tidsskrift for farmaci, 1 , no. 7, 205–212; C. Doris Hellman, “Was Tycho Brahe as Influential as He Thought?,”, in British Journal for the History of Science, 1 , pt. 4 , no. 4 (Dec. 1963), 295–324; Flora Kleinschnitzová, “Ex Bibliotheca Tychoniana Collegii Soc. Jesu Pragae ad S. Clementem,” in Nordisk tidskrift för bok–och biblioteksväsen, 20 (1933), 73–97; Wilhelm Krebs, “Facsimile einer eigenhändigen Zeichnung Tycho’s de Brahe von dem grossen Kometen 1577,” in Das Weltall. Illustrierte Zeitschrift för Astronomie und verwandte Gebiete12 (1911), 52–53; Martha List, Des handschriftliche Nachlass der Astronomen Johannes Kepler und Tycho Brahe (Munich, 1961); Knud Lundmark, “Tycho Brahe och astrofysiken,” in Nordisk astronomisk tidsskrift, n.s. 11 , no.3 (1930), 89–112; and “Om Tycho Brahes liv och gärning,” in Cassiopeia (1945), 14–47; N. A. Møller Nicolaisen, “Nicholai Raimarus Ursus contra Tycho Brahe,” ibid. (1942), 81–91; Harald Mortensen, “Portraeter af Tycho Brahe,” ibid. (1946), 52–77; “Tycho Brahe i Wandsbek,” in Astronomiska sällskapet Tycho Brahe ärsbok (1945), pp. 94–98; and “Tychoniana,” in Cassiopeia (1948), 21–27; Wilhelm Norlind, “Tycho Brahe och Thaddaeus Hagecius: Ur en brevväxling,” ibid (1939), 122–130; “A Hitherto Unpublished Letter From Tycho Brahe to Christopher Clavius,” in Observatory, 74 (1954), 20–23; and “Tycho–Brahé et ses rapports avec I’Italie,” C. Cardot, trans., in Scientia, 49 (1955), 47–61; Eiler Nystrøm, “Tyge Brahes Brud med Faedrelandet,” in Festskrift til Kristian Erslev, dem 28. Decbr. 1927…. pp. 291–320; and Epistolae et acta ad vitam Tychonis Brahe pertinentia (Copenhagen, 1928); Wilhelm Prandtl, “Die Bibliothek des Tycho Brahe,” in Philobiblon; eine Zeitschrift för Böcherliebhaber5 , no. 8 (1932), 291–300, no. 9, 321–330; Hans Raeder, “Tycho Brahe og hans korrespondenter,” in Edda, 27 (1927), 250–264; Edward Rosen, “Kepler’s Defense of Tycho Brahe Against Ursus,” in Popular Astronomy, 54 , no. 8 (1946), 1–8; Henrik Sandblad, “En Tycho Brahenotis,” in Lychnos (1937), 366–368, concerning the duel in which Tycho lost part of his nose; Aydin Sayili, “Islam and the Rise of Seventeenth Century Science,” in Belleten (Ankara), 22 , no. 87 (July 1958), 353–368; and “Tycho Brahe Sistemi Hakkinda XVII. Asir başlarina ait Farça Bir yazma. An Early Seventeenth Century Persian Manuscript on the Tychonic System,” in Anatolia revue annuelle de I’Institut d’Archélogie de I’Université d’Ankara, 3 (1958), 79–87; Ottomar Schiller. “Tycho Brahe à Prague,” in Archeion, 22 , no. 4 (12 Feb. 1941), 372–375; H. C. F. G. Schjellerup, “Tycho Brahes Original–Observationer, benyttede til Banebestemmelse af Cometen 1580,” in Det Kongelige Danske Videnskabernes selskab. Skrifter. 5 Raekke, Naturvidenskabelig og Mathematisk Afdeling. IV (1856–1859), pp. 1–39; Christine Schofield, “The Geoheliocentric Mathematical Hypothesis in Sixteenth Century Planetary Theory,” in British Journal for the History of Science, 2 (1965), 291–296; Harold Spencer Jones, “Tycho Brahe (1546–1601),” in Nature, 158 (1946), 856–861; E.S., “Tycho Brahes Immatrikulation ved Universitetet i Leipzig vinterhalvaaret 1561–62,” in Nordisk astronomisk tidsskrift, n.s. 9 , no. 2 (1928), 41–42; Elis Strömgren, “Tycho Brahes sekstanter,” ibid., n.s. 14 , no. 2 (1933), 69–75; F.J. Studnička. ed., Prager Tychoniana (Prague, 1901); and, as author, Bericht öber die astrologischen Studien des Reformators der beobachtenden Astronomie Tycho Brahe…. (Prague, 1901); Sevim Tekeli, “Nasirüddin, Takiyüddin ve Sesi” (“The Comparison Instruments of Taqi at Din and Tycho Brahe”), in Ankara Üniversitesi, Coğrafya Fakültesi dergisi, 16 (1958), 301–393; and “Solar Parmeters and Certain Observational Methods of Taqī at Dīn and Tycho Brahe,” in Proceedings of the 10th International Congress of the History of Science, I (Paris, 1964), 623–626; and Victor E. Thoren. “Tycho Brahe on the Lunar Theory,” doctoral dissertation (Indiana Univ., 1965); “Tycho and Kepler on the Lunar Theory,” in Publications of the Astronomical Society of the pacific, 79 , no. 470 (Oct. 1967), 482–489; “An Early Instance of Deductive Discovery; Tycho Brahe’s Lunar Theory,” in Isis, 58 (1967), 19–36; and “Tycho Brahe’s Discovery of the Variation,” in Centaurus, 12 , no. 3 (1967), 151–166.

Dr. Thoren kindly advised on the description of Tycho’s lunar theory and helped in the final draft of that section.

C. Doris Hellman

BRAHE, TYCHO

(b. Skåne, Denmark [later in Sweden], 14 December 1546; d. Prague, Czech Republic, 24 October 1601), astronomy. For the original article on Brahe see DSB, vol. 2.

Brahe’s contribution to the history of European science and culture appears far richer in the early 2000s than it did in 1970. Victor E. Thoren’s 1990 biography established a new starting point for understanding Tycho’s astronomy, whereas Peter Zeeberg showed how deeply Tycho was embedded in the humanist culture of the late Renaissance, and J. R. Christianson examined his patronage of scientists, technicians, artists, and natural philosophers who participated in his large-scale research and cultural projects. Many other scholars have presented new understandings of Tycho’s astronomy, cosmology, and natural philosophy. Tycho Brahe was a generous, courtly, but demanding aristocrat who was a theoretical astronomer of the first rank and founder of the first modern research institute, as well as the inventor of fundamental methods of observational science.

Humanist Influence. During the decade 1559 to 1570 that Tycho spent as a university student, studies that bore the imprint of the humanist reformer, Philipp Melanchthon shaped his outlook. In the Philippist curriculum of the Lutheran universities Tycho attended, students acquired an awareness of divine law by studying the laws placed by God in nature, because the”manifest footprints of God in nature” led onward to religious faith. Arithmetic, geometry, astronomy, astrology, geography (including cartography and chorography), anatomy, and botany were parts of this plan of study. The Philippist curriculum channeled Tycho Brahe’s strong personal interests in astronomy and astrology, and it resonated with his attraction to Paracelsian medicine. The urge to return ad fontes—to the sources of wisdom that lay within the natural world itself—energized these approaches. Lutheran theology, Hermetic philosophy, and millenial astrology all taught Tycho to strive for the instauration of a lost golden age, and he came to believe that active natural philosophy could help to achieve it. By the age of sixteen, he was convinced that the sources of wisdom in astronomy and astrology lay not in books but in the heavens themselves and that only precise observation could recover them. At the same time, he believed that knowledge of God’s laws discovered in nature must harmonize with the divine wisdom of the Bible.

Tycho Brahe had grown up in the circle of the Danish court. He returned to his native Denmark from studies abroad in 1570 and became a courtier in 1572. Around the same time, he fell in love with Kirsten Jørgensdatter (sometimes erroneously called Kristine Barbara). She was probably the daughter of a Lutheran pastor, but because she did not share his noble birth she was not acceptable at court. A wedding between an aristocrat and a commoner was illegal in sixteenth-century Denmark, but a common-law marriage was not. Tycho and Kirsten began living together in 1572, and the first of their eight children was born in September of 1573. They enjoyed a warm, harmonious marriage that lasted a lifetime.

Tycho was still a courtier when he observed the supernova of 1572. He discussed it with others at court, including the royal physician, Petrus Severinus; the French ambassador, Charles de Danzay, and his powerful uncle, Steward of the Realm Peder Oxe. They urged him to publish it, and he did so in 1573. Aristotelian physics denied that change could occur in the celestial spheres, but Severinus had just published a book on Paracelsus’s theory of semina, spiritual principles throughout the universe that give birth in their appointed times. This could explain how the birth of a new star might take place far beyond the Moon in the region of the stars. Tycho reported on the star’s astrological implications to King Frederik II. That winter, he lectured on astronomy in Copenhagen University, using Copernicus as his text-book—one of the first at any university to do so.

King Frederik was building “Hamlet’s Castle” at Kronborg in Elsinore to proclaim the power and splendor of the Danish realm at the very entrance to the Baltic Sea. Tycho traveled throughout Germany, Switzerland, and northern Italy in 1575. When he returned, he recommended various artists and artisans in Augsburg, Nürnberg, Hesse, and the Veneto for the Kronborg project. Landgrave William IV of Hesse-Cassel, whom Tycho had visited during his travels, sent a message to King Frederik, urging him to promote Tycho Brahe’s astronomy and natural philosophy for the benefit of humanity and the glory of the kingdom of Denmark. With this in mind, King Frederik on 11 February 1576 proposed to Tycho that he establish a royal Danish research center within sight of Elsinore on the island of Hven. The king intended it to be a place that would complement Kronborg Castle in contributing to the prestige of the kingdom. Tycho was astonished by the offer and accepted.

For the next twenty-one years, Tycho was given a free hand and extraordinary financial support to carry out research in astronomy, Paracelsian chemistry, and related subjects. The same artists and artisans who embellished Kronborg were also employed to make Uraniborg into a place of splendor. At Uraniborg, Tycho Brahe found innovative ways to integrate into an aristocratic lifestyle his far-ranging interests in astronomy, astrology, meteorology, mathematics, cosmology, cartography, chemistry, medicine, geodetic triangular surveying, hydraulic engineering, and a host of other fields including architecture, poetry, music, history, theology, and philosophy. Tycho’s collections of naturalia, scientific instruments, books, manuscripts, paintings, animated”Vitruvian” statues and other sculpture, his printing press and paper mill, botanical gardens and aviaries, the music and spirited conversation that filled his house, and his open-handed hospitality in entertaining kings, queens, princes, ambassadors, nobles, scholars, and artists from many lands became legendary. Tycho was a fine stylist of Latin poetry and prose who admired Ovid and Augustan classicism. His learned sister, Sophie Brahe, a genealogist, astrologer, and Paracelsian chemist, was a frequent guest.

Zeeberg has compared Tycho’s Uraniborg with Castiglione’s Urbino, the Platonic Academy of Medici Florence, and the circle of Erasmus and Thomas More in England as one of the most brilliant expressions of Renaissance culture. In short, Uraniborg fully achieved the aims of King Frederik when he commissioned Tycho Brahe to establish it.

Astronomical Instruments. Tycho’s instrumentation had been rather rudimentary when the supernova of 1572 appeared. By the time he saw his first comet in 1577, however, he could observe its altitude and azimuth with a quadrant that was a landmark because of its innovative features. Tycho fitted a large steel sextant with the same innovations and used it, as well as a cross-staff, to observe distances between the comet and nearby stars, frequently repeating the same observation with two instruments in order to compare results. In his persistent search for observational precision, Tycho Brahe gradually invented the modern rules of empirical evidence. As Thoren put it, nobody before Tycho

even catered to the ordinary rules of evidence, whereby several determinations of result would be deemed to provide more credibility than one or (rarely) two did. The problem with such redundancy, no doubt, was that it required concomitantly modern attitudes toward empirical data. The willingness to acknowledge error and the capacity to analyze its origins were the crux of Tycho’s concern for and success in the construction of instruments, so it is not surprising to see these attributes manifested in his handling of data. (Thoren, 1990, p. 137)

Tycho’s observations located both the supernova of 1572 and the comet of 1577 in celestial space above the Moon. This was contrary to Aristotelian physics, so Tycho and many of his contemporaries were compelled to reconsider the shape of the cosmos as a whole. In 1578, Tycho wrote a manuscript in German on the comet, not for publication but as a secret report to King Frederik II in his capacity as royal astrologer. He laid out the political effects that the comet foretold on Earth and included his astronomical and cosmological analysis as background. Tycho determined that the comet was located somewhere between the Moon and Venus and concluded that a separate cometary sphere occupied that space. He theorized that Mercury, Venus, and the comet revolved around the Sun, which in turn revolved around the Earth. When another comet appeared in 1580, Tycho assigned it to the same cometary sphere. That year, Paul Wittich visited Uraniborg and inspired Tycho to rethink his cosmology. In 1582, Tycho set out to observe Mars in opposition as a way to judge between the Copernican and Ptolemaic systems, repeating these observations in 1585 and 1587 with superior instruments in Uraniborg and his new Stjerneborg observatory. He located the comet of 1585 very close to the Sun. This finally led Tycho to reject the

theory of solid celestial spheres, although he continued to believe that the celestial medium, aether, was a different element than terrestrial air. Once the spheres were out of the way, however, Tycho felt able to propound a new planetary theory in which orbits intersected, with all comets, planets, and the Moon revolving around the Sun, which in turn revolved around a stationary earth. Scholars still debate the role played in the development of Tycho’s theory by his competition with Nicolas Reimers Ursus and his exchanges with Paul Wittich and Christopher Roth-mann.

Tycho Brahe’s innovative skill as a theoretical astronomer was clearly demonstrated by Thoren’s analysis of his three major contributions to lunar theory. Thoren noted that Tycho’s discovery of the variation was “the first new astronomical phenomenon to be discovered since Ptolemy’s time.” Tycho went on to discover nutation, and finally, he deduced the existence of nodal oscillation. The “theoretical prediction of the existence of a previously unnoticed phenomenon,” Thoren noted, was “completely unprecedented” (Thoren, 1990, pp. 327, 333). He showed that Tycho’s solar theory was equally innovative, whereas Owen Gingerich and James Voelkel emphasized the importance of Mars in Tycho’s mature program of observation. These Mars observations later played an indispensible part in Kepler’s discovery of his laws of planetary motion.

Tycho Brahe’s organization of research on a large scale, involving centrally directed teams of scientists and technicians, scientific expeditions to gather data from distant locations, and collaboration with numerous other researchers across the face of Europe, was largely unprecedented. He used his aristocratic wealth, leadership ability, and social panache to solve classic problems in unprecedented ways with whole teams of scholars and technicians. As part of this process, Tycho personally taught his methods of observation and data reduction to numerous younger astronomers, including Johannes Kepler, Willebrord Snel, Paul Wittich, Simon Marius (Mayr), Duncan Liddel, David Fabricius of Resterhave (father of Johannes Fabricius), Johannes Müller of Berlin, Christian Sørensen Longomontanus, Adriaan Metius, and Christopher Roth-mann. Leading seventeenth-century cartographers, Willem Janszoon Blaeu and Arnold Floris van Langren, also worked as his assistants, and Tycho prepared the first Scandinavian map based on geodetic triangular surveying. Tycho corresponded with astronomers and princes across Europe and sent them copies of his published works.

Tycho was a lifelong proponent of aristocratic constitutional government, and this put him at odds with the absolutist ambitions of King Christian IV, who was crowned in 1596. Moreover, a powerful clique at Copenhagen University resented Tycho’s attracting their best students, and orthodox theologians opposed his Lutheran Philippism. These forces combined to drive Tycho into the voluntary exile from Denmark that eventually led to the court of Emperor Rudolf II and to his contact with Johannes Kepler.

Analysis of hairs preserved from Tycho’s beard revealed high levels of mercury, which probably stemmed from plague medicine that he administered to himself and may have contributed to his death. Unsubstantiated speculation that he was poisoned proved to be without credibility.

SUPPLEMENTARY BIBLIOGRAPHY

WORKS BY BRAHE

Christianson, John Robert. “Tycho Brahe’s Facts of Life.” Fund og Forskning i det kongelige biblioteks samlinger 17 (1970): 21–28.

———. “Addenda to Tycho Brahe Opera Omnia tomus XIV.” Centaurus 16 (1972): 231–247.

Zeeberg, Peter. Tycho Brahes “Urania Titani:” Et digt om Sophie Brahe. Copenhagen: Museum Tusculanum, 1994. Tycho Brahe’s major Latin poem and the Renaissance culture of Uraniborg.

Hadravová, Alena, Petr Hadrava, and Jole R. Shackelford, trans. and eds. Tycho Brahe: Instruments of the Renewed Astronomy. Prague: Konaisch Latin Press, 1996.

Zeeberg, Peter. “The Inscriptions of Tycho Brahe’s Uraniborg.” In A History of Nordic Neo-Latin Literature. Edited by Minna Skafte Jensen. Odense, Denmark: Odense Universitetsforlag, 1996.

OTHER SOURCES

Blair, Ann. “Tycho Brahe’s Critique of Copernicus and the Copernican System.” Isis 51 (1990): 355–377.

Brosseder, Claudia. “The Writing in the Wittenberg Sky: Astrology in Sixteenth-Century Germany.” Journal of the History of Ideas 66 (2005): 557–576.

Christianson, John R. “Tycho Brahe’s German Treatise on the Comet of 1577: A Study in Science and Politics.” Isis 70 (1979): 110–140.

———. “Tycho Brahe in Scandinavian Scholarship.” History ofScience 36 (1998): 467–484.

———.On Tycho’s Island: Tycho Brahe and His Assistants, 1570–1601. Cambridge, U.K.: Cambridge, 2000. The abridged paperback edition (2003) has the subtitle, Tycho Brahe, Science, and Culture in the Sixteenth Century.

———. “The Legacy of Tycho Brahe.” Centaurus 44 (2002): 228–247.

Christianson, John Robert, Alena Hadravová, Petr Hadrava, et al., eds. Tycho Brahe and Prague: Crossroads of European Science, vol. 16, Acta Historica Astronomiae. Frankfurt am Main: Harri Deutsch, 2002. Twenty-six articles on Tycho.

Danneskiold-Samsøe, J. F. C. Muses and Patrons: Cultures ofNatural Philosophy in Seventeenth-Century Scandinavia, vol. 10,Ugglan Minervaserien. Lund, Sweden: Lunds Universitet, 2004.

Daussy, Hugues. “Un diplomat protestant au service d’un roi catholique: Charles de Danzay, ambassadeur de France au Danemark (1515–1589).” In Élites et notables de l’Ouest, XVIe-XXe siècle: Entre conservatisme et modernité, edited by Frédérique Pitou. Rennes, France: Presses Universitaires, 2004.

Frank, Günther, and Stefan Rhein, eds. Melanchthon und dieNaturwissenschaften seiner Zeit. Sigmaringen, Germany: Jan Thorbecke Verlag, 1998.

Gingerich, Owen. “Tycho Brahe and the Great Comet of 1577.” Sky and Telescope 54 (1977): 452–458.

———, and Robert S. Westman. The Wittich Connection:Conflict and Priority in Late Sixteenth-Century Cosmology. Philadelphia: The American Philosophical Society, 1988. Tycho’s relationship with Paul Wittich.

———, and James R. Voelkel. “Tycho Brahe’s Copernican Campaign.”Journal for the History of Astronomy 29 (1998): 1–34.

Granada, Miguel A. “Did Tycho Eliminate the Celestial Spheres Before 1586?” Journal for the History of Astronomy 37 (2006): 125–145. Includes references to other literature on celestial spheres.

Grant, Edward. Planets, Stars, and Orbs: The Medieval Cosmos, 1200–1687. Cambridge, U.K.: Cambridge, 1994.

Håkansson, Håkan. “Tycho the Apocalyptic: History, Prophecy and the Meaning of Natural Phenomena.” In Science in Contact at the Beginning of the Scientific Revolution, edited by Jitka Zamrzlová. Prague: National Technical Museum, 2004

———, ed. Tycho Brahe och Renässansen: Att låta själen flyga mellan himlens tinnar. Stockholm: Atlantis, 2006.

Haasbroek, N. D. Gemma Frisius, Tycho Brahe and Snellius andTheir Triangulations. Delft, The Netherlands: Rijkscommissie voor Geodesie, 1968.

Hannaway, Owen. “Laboratory Design and the Aim of Science: Andreas Libavius versus Tycho Brahe.” Isis77 (1986): 585–610.

———. “Johan Gregor van der Schardt: Sculptor—and Architect.” Hafnia: Copenhagen Papers in the History of Art10 (1985): 147–164.

Honnens de Lichtenberg, Hanne. Johan Gregor van der Schardt:Bildhauer bei Kaiser Maximillian II, am dänischen Hof und bei Tycho Brahe. Translated from Danish by Georg Albrecht Mai. Copenhagen: Museum Tusculanum, 1991.

———. “Tycho Brahe als Mäzen.” In Europa in Scandinavia:Kulturelle und soziale Dialoge in der frühen Neuzeit, vol. 2, Studia septemtrionalia, edited by Robert Bohn, 91–97. Frankfurt am Main: Peter Lang 1994.

Howell, Kenneth J. God’s Two Books: Copernican Cosmology andBiblical Interpretation in Early Modern Science. South Bend, IN: University of Notre Dame, 2002.

Jacobsen, Aase R., and Lars Petersen. “How Tycho Brahe Really Died.” Planetarium 30 (2001): 9–10.

Jardine, Nicholas. The Birth of History and Philosophy of Science:Kepler's A Defense of Tycho Against Ursus with Essays on Its Provenance and Significance. New York: Cambridge University Press, 1984.

Jardine, Nicholas, Dieter Launert, Alain Segonds, et al. “Tycho v. Ursus: The Build-Up to a Trial, Part 1.” Journal for the History of Astronomy 36 (2005): 81–106.

Jarrell, Richard A. “The Contemporaries of Tycho Brahe.” In The General History of Astronomy, vol. 2, Planetary Astronomy from the Renaissance to the Rise of Astrophysics, Part A: Tycho Brahe to Newton, edited by René Taton and Curtis Wilson. New York: Cambridge University Press, 1989.

Jones, Michael. “Tycho Brahe, Cartography and Landscape in 16^th Century Scandinavia.” In European Rural Landscapes: Persistence and Change in a Globalising Environment, edited by Hannes Palang, Helen Sooväli, Marc Antorp, et al. Boston: Kluwer Academic Publishers, 2004.

Kæmpe, Bent, Claus Thykier, and N. A. Pedersen. “The Cause of Death of Tycho Brahe in 1601.” Proceedings of the XXXI Congress of the The International Association of Forensic Toxicologists (TIAFT), 15–20 August 1993 in Leipzig (1993), 1–7.

Kongsted, Ole. Kronborg-Brunnen und Kronborg-Mottetten, vol. 43, Schriften des Gesellschaft für Flensburger Stadtgeschichte. Copenhagen: Det kongelige Bibliotek, 1991.

Kusukawa, Sachiko. The Transformation of Natural Philosophy:The Case of Philip Melanchthon. Cambridge, U.K.: Cambridge University Press, 1995.

Lundquist, Kjell. “The plant material in the Renaissance garden of Tycho Brahe at Uraniborg (1581-1597) on the island of Ven—A restoration project in progress.” Museologica scientifica 14 (1998), suppl.: 223–235.

———. “Reconstruction of the Planting in Uraniborg, Tycho Brahe’s (1546–1601) Renaissance Garden on the Island of Ven.” Garden History: Journal of the Garden History Society 32 (2004): 152–166.

Methuen, Charlotte. “The Role of the Heavens in the Thought of Philip Melanchthon.” Journal of the History of Ideas 57 (1996): 385–403.

Moesgaard, Kristian Peder. “Copernican Influence on Tycho Brahe.” In The Reception of Copernicus’ Heliocentric Theory, vol. 1, Colloquia Copernicana, edited by Jerzy Dobrzycki. Dortrecht, Netherlands: D. Reidel, 1972.

———. “How Copernicanism Took Root in Denmark and Norway.” In The Reception of Copernicus’ Heliocentric Theory, vol. 1, Colloquia Copernicana, edited by Jerzy Dobrzycki. Dortrecht, Netherlands: D. Reidel, 1972.

———. “Tychonian Observations, Perfect Numbers, and the Date of Creation: Longomontanus’s Solar and Precessional Theories.”Journal for the History of Astronomy 6 (1975): 84–99.

———. “Cosmology in the Wake of Tycho Brahe’s Astronomy.” In Cosmology, History, and Theory, edited by Wolfgang Yourgrau and Allen D. Breck. New York: Plenum Press, 1977.

Moran, Bruce T. “Christoph Rothmann, the Copernican Theory, and Institutional and Technical Influence on the Criticism of Aristotelean Cosmology.” Sixteenth Century Journal 13 (1982): 85–108.

———.Distilling Knowledge: Alchemy, Chemistry, and theScientific Revolution. Cambridge, MA: Harvard University Press, 2005.

———, ed. Patronage and Institutions: Science, Technology andMedicine at the European Court 1500–1750. Rochester, NY: Boydell Press, 1991.

Mosley, Adam, Nicholas Jardine, and Karin Tybjerg. “Epistolary Culture, Editorial Practices, and the Propriety of Tycho’s Astronomical Letters.”Journal for the History of Astronomy 34 (2003): 421–451.

———.Bearing the Heavens: Tycho Brahe and the AstronomicalCommunity of the Late Sixteenth Century. Cambridge, U.K.: Cambridge University Press, 2007.

Norlind, Wilhelm. Tycho Brahe: En levnadsteckning. Lund, Sweden: C. W. K. Gleerup, 1970. Tycho’s life, works, and library, with a German summary.

Rosen, Edward. Three Imperial Mathematicians: Kepler TrappedBetween Tycho Brahe and Ursus. New York: Abaris Books, 1986.

Schofield, Christine Jones. Tychonic and Semi-Tychonic WorldSystems. New York: Arno Press, 1981.

Schofield, Christine. “The Tychonic and Semi-Tychonic World Systems.” In The General History of Astronomy, vol. 2, Planetary Astronomy from the Renaissance to the Rise of Astrophysics, Part A: Tycho Brahe to Newton, edited by René Taton and Curtis Wilson. New York: Cambridge University Press, 1989.

Shackelford, Jole. “Paracelsianism and Patronage in Early Modern Denmark.” In Patronage and Institutions: Science,

Technology, and Medicine at the European Court 1500–1750, edited by Bruce Moran. Rochester, NY: Boydell Press, 1991.

———. “Tycho Brahe, Laboratory Design, and the Aim of Science: Reading Plans in Context.” Isis 84 (1993): 211–230.

———. “Early Reception of Paracelsian Theory: Severinus and Erastus,” Sixteenth Century Journal 26 (1995): 123–135.

———. “Rosicrucianism, Lutheran Orthodoxy, and the Rejection of Paracelsianism in Early Seventeenth-Century Denmark,” Bulletin of the History of Medicine 70 (1996): 181–204.

———. “Seeds with a Mechanical Purpose: Severinus’ Semina and Seventeenth-Century Matter Theory.” Sixteenth Century Essays and Studies 41 (1998): 15–44. ———. “Unification and the Chemistry of the Reformation.” Sixteenth Century Essays and Studies 40 (1998): 291–312. Tycho’s assistant, Cort Aslakssøn.

———.A Philosophical Path for Paracelsian Medicine: The Ideas, Intellectual Context, and Influence of Petrus Severinus (1540/2–1602). Copenhagen: Museum Tusculanum Press University of Copenhagen, 2004.

Skovgaard-Petersen, Karen, and Peter Zeeberg. “Recent Work on Nordic Neo-Latin Literature (1992–1996). Symbolae Osloenses, 72 (1997): 172–184. ———. “Recent Work on Nordic Neo-Latin Literature (1997–2000).Symbolae Osloenses, 76 (2001): 201–210.

———. “Recent Work on Nordic Neo-Latin Literature (2001–2004).” S ymbolae Osloenses, 79 (2004): 179–189. Thoren, Victor E. “An Early Instance of Deductive Discovery: Tycho Brahe’s Lunar Theory.” Isis 58 (1967): 19–36.

———. “Tycho Brahe’s Discovery of the Variation.” Centaurus 12 (1967): 151–166.

———. “An ‘Unpublished’ Version of Tycho Brahe’s Lunar Theory.” Centaurus 16 (1972): 203–230.

———. “New Light on Tycho’s Instruments,” Journal for theHistory of Astronomy 4 (1973): 25–45.

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———, with contributions by John Robert Christianson. TheLord of Uraniborg: A Biography of Tycho Brahe. Cambridge, U.K.: Cambridge University Press, 1990. The standard biography.

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———. “Tycho Brahe’s Solar Observations.” Journal for theHistory of Astronomy 10 (1979): 96–101.

———. “The Melanchthon Circle, Rheticus, and the Wittenberg Interpretation of the Copernican Theory.” Isis 66 (1975): 165–193.

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———, ed. The Copernican Achievement. Berkeley: University of California, 1975.

Zamrzlová, Jitka, ed. Science in Contact at the Beginning of theScientific Revolution, new ser. vol. 8, Prague Studies in the History of Science and Technology. Prague: National Technical Museum, 2004. Six articles on Tycho Brahe, including Håkansson above.

———. “Science versus Secular Life: A Central Theme in the Latin Poems of Tycho Brahe.” In Acta Conventus Neo-Latini Torontonensis, edited by Alexander Dalzell, Charles Fantazzi, and Richard J. Schoeck. Binghamton, NY: Center for Medieval and Early Renaissance Studies, 1991.

Zeeberg, Peter. “Alchemy, Astrology, and Ovid—A Love Poem by Tycho Brahe.” In Acta Conventus Neo-Latini Hafniensis, edited by Ann Moss et al. Binghamton, NY : Center for Medieval and Early Renaissance Studies, 1994.

———. “Neo-Latin Poetry in Its Social Context: Some Statistics and Some Examples from Sixteenth-Century Denmark.” In Mari Balticum—Mari Nostrum: Latin in the Countries of the Baltic Sea (1500-1800), series B, no. 274, Annales Academiæ Scientiarum Fennicæ, edited by Outi Merisalo and Raija Sarasti-Wilenius. Helsinki: Academia Scientiarum Fennica, 1994.

John Robert Christianson

BRAHE, TYCHO (1546–1601)

BRAHE, TYCHO (1546–1601), Danish astronomer and alchemist. Scion of the network of noble families that ruled Denmark in the sixteenth century, Tycho Brahe was heir to the lordship of the family seat, Knudstrup (in modern south Sweden). He entered the University of Copenhagen in 1559, but when it came time for him to travel and learn the ways and manners that would shape him into a noble warrior and statesman, he was sent abroad to Germany, where he studied at the universities of Leipzig, Wittenberg, Rostock, Basel (in Switzerland), and Augsburg. Mastering the fundamentals of mathematics and natural sciences, he was struck by the lack of precision in astronomy. While abroad he was also exposed to alchemy and the medical ideas of Paracelsus, the German religious enthusiast and physician whose ideas challenged the reigning academic medical establishment and were winning converts among members of Tycho's generation.

Tycho was recalled to Denmark when his father became mortally ill, in order to come into his inheritance and take his place among the feudal elite. Repelled by the life for which he had been bred, he sold his share of the family manor to his younger brother and moved in with his uncle at Herrevad manor, where he observed the stars and explored the nature of terrestrial matter in a small alchemical laboratory. He was walking to the main building from the laboratory in 1572 when he first spied a "new star" (nova stella) shining brightly in the constellation Cassiopeia, observation and consideration of which was to captivate his attention and change the course of his life. (It is now known as Tycho's star.)

According to the prevailing theory of the cosmos, drawn largely from Christian interpretations of the geocentric cosmology of Aristotle (384–322 b.c.e.), bodies in the heavens were permanent and incorruptible; whatever transitory objects appeared in the sky, such as comets, lightning, and hail, were regarded as terrestrial phenomena, occurring in the air or in the zone of fire imagined to surround it. Tycho, however, showed that the nova did not exhibit any parallax, the daily change of angular measurement that characterizes objects near the Earth, and must therefore be celestial, creating a problem for traditional cosmology. As a result of the treatise he published on the nova, he was asked to undertake a series of lectures on astrology and astronomy at the University of Copenhagen in 1574, and eventually King Frederick II (ruled 1559–1588) offered him lordship over the island of Hven, where, in the summer of 1576, he laid the foundation stone for his new manor house, which he named Uraniborg—castle of the heavens.

Uraniborg was modest in size, but elaborately designed and expensively crafted. In the basement Tycho created what at the time was one of Europe's most lavish alchemical laboratories, equipped with sixteen kinds of ovens for heating and distilling various plant, animal, and mineral substances in order to concentrate their virtues and obtain their spiritual essences. On the main floor were rooms for his family and guests, a kitchen, and a combination library and study. Each end of the second floor of the building housed an array of instruments located under removable roof sections. Tycho had ordered the first of his permanent instruments for measuring angles between celestial objects while in Augsburg and he added to his collection at Uraniborg, continuing to expand the sizes, designs, and materials of these instruments, building a special workshop nearby and employing trained craftsmen for this purpose. Finding that subtle movements of the instruments caused by the wind or by unsteady supports limited the accuracy of observations, Tycho built Stjærneborg ('castle of the stars'), an observatory comprising a central room surrounded by five pits dug into the ground, each of which was covered by a removable lid and housed a particular instrument that was set upon a stone foundation to reduce vibration. With large instruments of such quality, he attained unprecedented accuracy. Christian IV, however, succeeded Frederick II, assuming the throne in 1596, and began to cut Tycho's funding. In response, Tycho packed up his instruments and left Denmark in 1597, securing a position as imperial astronomer to the Holy Roman emperor Rudolf II, who provided him a castle near Prague in which to reestablish his research facilities, both astronomical and alchemical. At this point Tycho hired Johannes Kepler to assist him with the calculations necessary to establish a new astronomical theory on the basis of his accurate data—a theory that Tycho assumed would take a new form, with the Earth at the center of the movements of the Moon and Sun, but with the movements of the rest of the planets centered on the Sun. When Tycho died suddenly in the fall of 1601, Kepler was free to use the valuable data to create his own system, which laid the foundations for Newton's gravitational astronomy.

See also Alchemy ; Astronomy ; Cosmology ; Denmark ; Kepler, Johannes ; Paracelsus ; Scientific Instruments.

BIBLIOGRAPHY

Primary Source

Brahe, Tycho. Tycho Brahe's Description of his Instruments and Scientific Work as given in Astronomiæ Instauratæ Mechanica. Translated and edited by Hans Raeder, Elis Strømgren, and Bengt Strømgren. Copenhagen, 1946.

Secondary Sources

Christianson, John Robert. On Tycho's Island: Tycho Brahe and His Assistants, 1570–1601. Cambridge, U.K., 2000.

Shackelford, Jole. "Tycho Brahe, Laboratory Design, and the Aim of Science: Reading Plans in Context." Isis 84 (1993): 211–230.

Thoren, Victor E. The Lord of Uraniborg: A Biography of Tycho Brahe. Cambridge, U.K., 1990.

Jole Shackelford

Tycho Brahe

1546-1601

Astronomer

Sources

Beginnings. Born into Denmark’s high nobility, Tycho Brahe opted to become a prince of scientific researchers instead of pursuing a military or diplomatic career, as befit his aristocratic heritage. Like many of his noble peers, he was tutored in Latin at home and traveled widely in his youth, visiting various European universities—enrolling at Copenhagen, Leipzig, and Rostock—and making the acquaintance of natural philosophers and noblemen wherever he went. Astronomy captured his interest early, and he bought books and instruments for private study of the subject. When he realized that his observations in Leipzig of the conjunction of Jupiter and Saturn did not agree with the date predicted by the astronomical tables then in use, he determined to reform astronomy and bring it up to date with new observations. Such tables were of great importance in Renaissance Europe because the accuracy of astrological prediction depended on them, and such predictions affected medical diagnostics and therapy as well as providing the widely popular horoscopes that guided kings and commoners alike. The needs of state, in particular, made astrology a suitable science for an aristocrat to dabble in, as was alchemy, which Brahe also studied in Germany. When his father’s death forced him to return to Denmark and settle his inheritance, Brahe sold his share of the family estate to his brother and moved into the former Herrevad Abbey, which was in the possession of his aunt and uncle. There he built a laboratory and set about what would become his lifelong pursuit of both alchemy and astronomy.

Birth of a Star. In fact, Brahe viewed alchemy and astrology as two aspects of a single science. He believed that there was a sympathetic correspondence between the stars and planets, metals, minerals, stones, and plants, and also the organs of the human body. The operations of the cosmos could therefore be studied in the observatory, by means of what he called “celestial astronomy,” or in the laboratory, by “terrestrial astronomy,” which referred to alchemy. Brahe recalled that he was returning to the main house from his laboratory at Herrevad in 1572 when he first noticed a new star in the sky, a phenomenon that is still called a nova (new). Such a thing was unknown to Europeans and was presumed not to be possible in the celestial realm, since the region of the stars and planets was generally thought to be perfect and incapable of any novelty or decay. Accordingly, astronomers throughout Europe were eager to observe the new star and publish their interpretations of what it might be and what its appearance portended. Brahe carefully observed the new star and determined it to be a long distance from the Earth, and therefore not simply an atmospheric phenomenon of some sort, as Aristotle had taught.

Uraniborg. Brahe published his findings and interpretations in De nova stella (The New Star) in 1573. The small volume demonstrated that he was a competent and well-educated astronomer, bringing him to the attention of Europe’s scholars and encouraging the king of Denmark to offer him a feudal endowment if he would build a research facility on royal land and reside in Denmark as an aristocrat in service to the crown. This position was the kind that suited a member of one of Denmark’s most powerful families. The result was Uraniborg, a Renaissance villa that Brahe erected on the island of Hven, within sight of Copenhagen and the royal fortresses of Kronborg and Landskrona, between which every ship entering the Baltic Sea from the Atlantic must pass. The location was in many respects ideal: it was central to the kingdom, within easy reach of the capital and the court, and yet isolated by water, providing a measure of privacy and undisturbed study. The island rises abruptly out of the Danish sound that today separates Sweden from Denmark, and often enjoys clear weather when the nearby shores are clouded over, making it a suitable location for an observatory.

Laboratory. Uraniborg was not expansive by Danish aristocratic standards, but expensive to build and maintain. It featured the latest Dutch and Italianate architectural styles, statuary, Dutch paintings, and a stone-faced earthen perimeter wall with gate houses, surrounded by an elaborate garden with gazebos and walkways. Uraniborg was more than an aristocrat’s house, though. Its clever design also accommodated a library, where the research staff could gather, sleeping rooms for his assistants, and observation decks with removable roof sections on the north and south ends of the second story. On these decks Brahe placed various devices for measuring the angles between stars and planets, which enabled him to record their positions. In the basement he built a well-equipped alchemical laboratory, which in complexity rivaled those owned by kings and princes elsewhere in Europe. Although he claimed to have spent an equal amount of time and money on alchemical research, no records of his work in that area have survived, except for a couple of recipes for medical elixirs. Nevertheless, reports from visitors to the island support Brahe’s description of an elaborate facility with many kinds of furnaces and condensers.

Accurate Data. As his need for greater astronomical precision developed, he constructed another observatory nearby, one that was dug into the ground in order to provide a protected place to mount even larger instruments out of the wind, which vibrated them and introduced errors. Several large observation pits, with stable stone foundations on which to set various enormous quadrants and armillary astrolabes, had removable covers to shield them from the rain and permit sighting of the major celestial phenomena. With the best of these instruments, Brahe was able to double the accuracy of previous astronomical data. He commemorated the irony of observing the heavens from underground in a Latin poem, one of many that revealed his training as a Renaissance scholar.

Quest for Perfection. Construction of Uraniborg commenced in 1576 and was largely completed by 1580, but Brahe was an incessant builder and tireless researcher, always trying to improve his research methods and tinkering with the design of his villa and his instruments. Besides the underground observatory, which he intended to connect to Uraniborg by tunnel, he built a printing house and a paper mill, so that he could publish his work on location. The mill was water powered, but since there was no sufficient stream of water on Hven, Brahe created a system of fish ponds that acted as reservoirs to collect rainwater to drive the water wheel. He also built a workshop and a glassworks to supply his instruments, alchemical glassware, and household needs.

Published Work. Brahe accumulated an immense amount of observational data while resident on Hven, which was eventually published as the Rudolphine astronomical tables in the next century. Besides positional data, from which he hoped to construct a new theory of planetary motion, he made an important observation on a comet in 1577, which proved that it was a celestial and not an atmospheric phenomenon, as the Aristotelians believed. Tycho’s realization that comets crossed through the orbs that were supposed to carry the Sun, Moon, and planets around Earth suggested to him that the celestial spheres were not substantial enough to hinder penetration. On this basis, he created his own planetary model, in which the Sun and Moon revolved around Earth, as was the case in ancient astronomy, but the other planets revolved around the Sun, as in the Copernican system. Brahe published the details of this new model in 1588 and it became quite influential in the seventeenth century.

Rudolf II. That same year King Frederik of Denmark, Brahe’s patron and friend, died and was succeeded by his son Christian IV. For various reasons, he fell out of favor with the new king and his advisers, who began to revoke his royal endowments. The result was that Brahe abandoned Uraniborg in 1597 and eventually secured an appointment at the court of Rudolf II, the Holy Roman Emperor, where he hoped to reproduce the research facilities he had developed in Denmark. To that end, he moved his household into Benatky Castle outside Prague, the imperial capital, shipped his instruments from Denmark, build a new observatory and laboratory, and continued his work. To help him with the tedious mathematical work of correlating observations with theory, Brahe recruited a German mathematician named Johannes Kepler. When Brahe died in 1601, Kepler took possession of the tomes of data that Brahe and his students had produced over the course of three decades and used them to establish a brand new theory: that all planets—including the Earth—traversed elliptical orbital paths around the Sun.

Legacy. Brahe’s many-sided research effort reflected a complex Renaissance view of the cosmos and a commitment to understanding it through systematic study. Besides astronomy and alchemy, he also kept a meteorological record, with which he hoped to grasp the relationship between astrology and weather conditions, he wrote Latin poetry, and began to make accurate maps of Hven and its surroundings. All of these activities were woven together into life at Uraniborg, which is regarded as Europe’s first dedicated research institute. Uraniborg itself fell into ruin in the decades after Brahe left it, cannibalized for building material for local projects. Brahe’s program, however, lived on in Copenhagen, where the king established a royal observatory where his student Christian Sørensen (Longomontanus) was installed as royal astronomer, and a royal laboratory, where a Paracelsian physician was hired to distill elixirs and make other chemical medicines.

Sources

John Robert Christiansen, On Tycho’s Island: Tycho Brahe and His Assistants, 1570-1601 (Cambridge & New York: Cambridge University Press, 2000).

Christine Jones Schofield, Tychonic and Semi-Tychonic World Systems (New York: Arno, 1981).

Victor Thoren, The Lord of Uraniborg: A Biography of Tycho Brahe (Cambridge & New York: Cambridge University Press, 1990).

Brahe, Tycho (1546-1601)

Danish astronomer

Tycho Brahe was one of the most colorful astronomers in history. Born in Denmark, Brahe was "adopted" (some say kidnapped) by his childless uncle at the age of one. Either way, his father, a Swedish nobleman, did not pursue the matter

(Brahe's given name was "Tyge," but the Latinized version is more common.)

Brahe received an excellent education. At the age of 13 he entered the University of Copenhagen, where he studied rhetoric and philosophy. He was well on his way toward a career in politics when he witnessed an eclipse of the Sun on August 21, 1560. Brahe spent the next two years studying mathematics and astronomy . He moved on to the University of Leipzig in 1562 where a tutor tried to influence him to study law, but Brahe refused to be diverted.

In August 1563, he made his first recorded observation, a close grouping between Jupiter and Saturn. (It was not until many years that Galileo first used a telescope to make astronomical observations; Brahe's precise work was done with the naked eye.) This was the turning point of his career. He was perturbed to note that this event occurred a month before its predicted date, and he began to buy astronomical instruments that would allow him to make very precise measurements so he could produce more accurate tables of data. He also developed interests in alchemy and astrology (which he considered a science) and began to cast horoscopes that, if nothing else, generated some income.

In November 1572, a supernova burst into view in the constellation of Cassiopeia, and Brahe was enthralled. The new star became brighter than Venus and was visible for eighteen months. He described it (along with its astrological "significance") with such detail in a book, the new star became known as "Tycho's star."

The book did three things: the title De Nova Stella (Concerning the new star) linked the name nova to all exploding stars. In addition, Brahe had been unable to make a parallax measurement for the nova. That indicated that it was much more distant than the Moon , which was a crushing blow to Aristotle's teachings that the heavens were perfect and unchanging. The third accomplishment was in establishing Brahe's reputation as an astronomer. The book was almost not produced. Initially, Brahe felt it was beneath his dignity as a nobleman to publish, but he was soon convinced otherwise.

Brahe's arrogance was legendary. At the age of nineteen, he was involved in a duel over a mathematical point, during which he lost his nose. He spent the rest of his life wearing a prosthesis. Fortunately, one of the few individuals not alienated by Brahe was Frederick II, the king of Denmark. In 1576, this patron of science gave Brahe a small island called Hveen, subsidized the building of an observatory there, and endowed Brahe with an annual payment. This became the first real astronomical observatory in history, and Brahe, always mindful of his noble background, saw to it that no expense was spared. The principal building, Uraniborg (Castle of the heavens), was the main residence; next to it was built the main observatory, Stjerneborg (Castle of the stars).

In 1577, a bright comet was visible, and Brahe observed it with great care. Measurements showed that it, too, was further than the moon and could not be atmospheric phenomena as Aristotle taught. Worse, Brahe reluctantly came to the conclusion that the path of the comet was not circular but elongated. This meant it would have to pass through the "spheres" that carried the planets around the sky, which would be impossible unless the spheres did not exist.

This concept troubled Brahe, who rejected the Sun-centered theory of Nicholas Copernicus because it not only violated scripture, it contradicted the teachings of Ptolemy . Brahe also reasoned that if Copernican theory was correct, he should have been able to detect stellar parallax as the year passed, but he could not.

Brahe tried to reconcile his beliefs with his observations by proposing a solar system in which all the planets orbited around the Sun, but the Sun orbited around the earth (to account for a year), and the celestial sphere made a single rotation each day. This would follow Copernicus's theory, do away with the Greeks' planetary spheres, and still keep the earth at its preeminent position. The Tychonic Theory was almost entirely ignored.

Brahe spent 20 years at Hveen, making exceptionally accurate observations. He used devices such as a huge quadrant with a radius of 6 feet (1.83 m), sextants, a bipartite arc, astrolabes, and various armillae. His measurements were the most precise that could be made without the aid of a telescope. He made corrections for nearly every known astronomical measurement and made Pope Gregory's calendar reform in 1582 possible. (Brahe himself did not adopt the new calendar until 1599.)

Frederick II died in 1588. His son, Christian IV, was only 11, so the country was ruled by regents, who left Brahe to his own devices. When Christian came of age in 1596, he quickly lost patience with the expensive, haughty astronomer, and Brahe was relieved of his royal duties the following year.

Brahe moved to Prague, where he resumed observing. As an assistant he employed a young German named Johannes Kepler , to whom he gave all his observations on Mars and the task of preparing tables of planetary motion. This would turn out to be the most significant decision of his life, as Kepler used the data to determine the elliptical nature of planetary motion.