Tycho Brahe
1546-1601
 

The Danish astronomer Tycho Brahe carried pretelescopic astronomy to its highest perfection and tried to steer a middle course between the Ptolemaic and the Copernican systems.
 

Tycho Brahe, referred to by his first name, was born on Dec. 14, 1546, the son of the governor of Helsingborg Castle. His upbringing and education were entrusted to his uncle, Joergen, a vice admiral. When only 13, Tycho began attending classes of rhetoric and philosophy at the University of Copenhagen, but almost immediately he was seized with a frustration which had to do with astronomy. It was the discrepancy between the predicted and observed time of a partial eclipse of the sun. His whole life was to be spent on perfecting astronomical observations and theories to eliminate discrepancies of this kind.

Tycho studied at the universities of Leipzig, Wittenberg, Rostock, Basel, and Augsburg (1562-1570). On his return to Denmark he went to live with an uncle, Steen Bille, the founder of the first paper mill and glassworks in that country. He was the only one in the family to approve of Tycho's addiction to astronomy. He let Tycho set up his own observatory and received in turn help from him in the alchemy shop. On the evening of Nov. 11, 1572, Tycho spotted a new bright star near Cassiopeia. Other astronomers too soon noticed the nova, but it was Tycho who provided the best evidence with his huge sextant that the new star was as immobile as the other fixed stars.

Tycho's book De stella nova (1573) was a landmark in astronomy and secured for him a lifelong career. First came his appointment at the University of Copenhagen, then the royal patent entrusting him with the construction of the famous observatory called Uraniborg (Castle of Heavens) on the island of Hven. Shortly after this took place (1576), Tycho delivered another blow at the belief codified by Aristotle that no change could occur above the orbit of the moon. In De mundi aetherei recentioribus phenomenis (1577) Tycho proved that the great comet of 1577 had to be at least six times farther than the moon. The book also contained the famous Tychonic system of planets. There a secondary center was occupied by the sun with Mercury and Venus orbiting around it, forming a small system. The sun with its small system turned around the immobile earth fixed slightly off-center to the sphere of the fixed stars. The three other planets, Mars, Jupiter, and Saturn, orbited around both the sun and the earth, and their orbits were centered not on the earth but on the sun. The sphere of the fixed stars made a full revolution each day.

Tycho left Denmark in 1587 and moved to Prague, carrying along the records of his observations and most of his instruments. In 1600 Johannes Kepler joined him as his assistant. It fell to Kepler to prepare for publication, following Tycho's sudden death in 1601, the latter's collection of astronomical studies, Astronomiae instauratae progymnasmata (1602-1603).
 

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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.
 

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Tycho Brahe (1546-1601)

Tyge (Latinized as Tycho) Brahe was born on 14 December 1546 in Skane, then in Denmark, now in Sweden. He was the eldest son of Otto Brahe and Beatte Bille, both from families in the high nobility of Denmark. He was brought up by his paternal uncle Jörgen Brahe and became his heir. He attended the universities of Copenhagen and Leipzig, and then traveled through the German region, studying further at the universities of Wittenberg, Rostock, and Basel. During this period his interest in alchemy and astronomy was aroused, and he bought several astronomical instruments. In a duel with another student, in Wittenberg in 1566, Tycho lost part of his nose. For the rest of his life he wore a metal insert over the missing part. He returned to Denmark in 1570.

In 1572 Tycho observed the new star in Cassiopeia and published a brief tract about it the following year. In 1574 he gave a course of lectures on astronomy at the University of Copenhagen. He was now convinced that the improvement of astronomy hinged on accurate observations. After another tour of Germany, where he visited astronomers, Tycho accepted an offer from the King Frederick II to fund an observatory. He was given the little island of Hven in the Sont near Copenhagen, and there he built his observatory, Uraniburg, which became the finest observatory in Europe.

Tycho designed and built new instruments, calibrated them, and instituted nightly observations. He also ran his own printing press. The observatory was visited by many scholars, and Tycho trained a generation of young astronomers there in the art of observing. After a falling out with King Christian IV, Tycho packed up his instruments and books in 1597 and left Denmark. After traveling several years, he settled in Prague in 1599 as the Imperial Mathematician at the court of Emperor Rudolph II. He died there in 1601. His instruments were stored and eventually lost.

Tycho's major works include De Nova et Nullius Aevi Memoria Prius Visa Stella ("On the New and Never Previously Seen Star) (Copenhagen, 1573); De Mundi Aetherei Recentioribus Phaenomenis ("Concerning Mural Quadrant the New Phenomena in the Ethereal World) (Uraniburg, 1588); Astronomiae Instauratae Mechanica ("Instruments for the Restored Astronomy") (Wandsbeck, 1598; English tr. Copenhagen, 1946); Astronomiae Instauratae Progymnasmata ("Introductory Exercises Toward a Restored Astronomy") (Prague 1602). His observations were not published during his lifetime. Johannes Kepler used them but they remained the property of his heirs. Several copies in manuscript circulated in Europe for many years, and a very faulty version was printed in 1666. At Prague, Tycho hired Johannes Kepler as an assistant to calculate planetary orbits from his observations. Kepler published the Tabulae Rudolphina in 1627. Because of Tycho's accurate observations and Kepler's elliptical astronomy, these tables were much more accurate than any previous tables.

Tycho Brahe's contributions to astronomy were enormous. He not only designed and built instruments, he also calibrated them and checked their accuracy periodically. He thus revolutionized astronomical instrumentation. He also changed observational practice profoundly. Whereas earlier astronomers had been content to observe the positions of planets and the Moon at certain important points of their orbits (e.g., opposition, quadrature, station), Tycho and his cast of assistants observed these bodies throughout their orbits. As a result, a number of orbital anomalies never before noticed were made explicit by Tycho. Without these complete series of observations of unprecedented accuracy, Kepler could not have discovered that planets move in elliptical orbits. Tycho was also the first astronomer to make corrections for atmospheric refraction. In general, whereas previous astronomers made observations accurate to perhaps 15 arc minutes, those of Tycho were accurate to perhaps 2 arc minutes, and it has been shown that his best observations were accurate to about half an arc minute.

Tycho's observations of the new star of 1572 and comet of 1577, and his publications on these phenomena, were instrumental in establishing the fact that these bodies were above the Moon and that therefore the heavens were not immutable as Aristotle
had argued and philosophers still believed. The heavens were changeable and therefore the Aristotelian division between the heavenly and earthly regions came under attack (see, for instance, Galileo's Dialogue) and was eventually dropped. Further, if comets were in the heavens, they moved through the heavens. Up to now it had been believed that planets were carried on material spheres (spherical shells) that fit tightly around each other. Tycho's observations showed that this arrangement was impossible because comets moved through these spheres. Celestial spheres faded out of existence between 1575 and 1625.

Tychonic Universe

If Tycho destroyed the dichotomy between the corrupt and ever changing sublunary world and the perfect and immutable heavens, then the new universe was clearly more hospitable for the heliocentric planetary arrangement proposed by Nicholas Copernicus in 1543. Was Tycho therefore a follower of Copernicus? He was not. Tycho gave various reasons for not accepting the heliocentric theory, but it appears that he could not abandon Aristotelian physics which is predicated on an absolute notion of place. Heavy bodies fall to their natural place, the Earth, which is the center of the universe. If the Earth were not the center of the universe, physics, as it was then known, was utterly undermined. On the other hand, the Copernican system had a number of advantages, some technical (such as a better lunar theory and smaller epicycles), and others more based on harmony (an obvious explanation of retrograde planetary motion, a strict demonstration of the order and heliocentric distances of the planets). Tycho developed a system that combined the best of both worlds. He kept the Earth in the center of the universe, so that he could retain Aristotelian physics (the only physics available). The Moon and Sun revolved about the Earth, and the shell of the fixed stars was centered on the Earth. But Mercury, Venus, Mars, Jupiter, and Saturn revolved about the Sun. He put the (circular) path of the comet of 1577 between Venus and Mars. This Tychonic world system became popular early in the seventeenth century among those who felt forced to reject the Ptolemaic arrangement of the planets (in which the Earth was the center of all motions) but who, for various reasons, could not accept the Copernican alternative.
 

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Tycho Brahe is probably the most famous observational astronomer of the sixteenth-century, although is not always clear whether he is better remembered for the fact that his data provided the basis for the work of Johannes Kepler (1571-1630), or because of the more colourful aspects of his life and death. Born into the high nobility of his native Denmark in 1546, he was groomed by his family for a career at court, but from an early age showed greater interest in astronomy than law, the discipline of choice for aspiring royal councillors and administrators. After three years at the University of Copenhagen, he spent much of the period from 1562 to 1576 travelling in Germany, studying at the Universities of Leipzig, Wittenberg, and Rostock, and working with other scholars in Basle, Augsburg, and Kassel. It was in Rostock in 1566 that he lost part of his
nose in a duel, and subsequently wore a prosthesis.

The appearance in 1572 of a "new star" (in fact a supernova) prompted Tycho's first publication, which was issued by a Copenhagen printer in 1573. In 1574, he gave some lectures on astronomy at the University of Copenhagen. Already he was of the opinion that the world-system of Copernicus was mathematically superior to that of Ptolemy, but physically absurd. In 1576, his permanent relocation to Basle, which he considered the most suitable place for him to continue his astronomical studies, was forestalled by King Frederick II, who offered him in fief the island of Hven in the Danish Sound. With generous royal support, Tycho constructed there a domicile and observatory which he called Uraniborg, and developed a range of instruments of remarkable size and precision which he used, with the aide of numerous assistants and students, to observe comets, stars, and planets.

In 1588, Tycho issued from his press a work on the comet which had appeared, causing a flurry of other publications, in 1577.  The eighth chapter of this book also contained Tycho's system of the world, which retained the earth as the unmoving centre of the universe but rendered the other planets satellites of the Sun. In 1596 he published a volume of his correspondence with another noble-astronomer, Wilhelm IV of Hesse-Kassel, and Wilhelm's mathematician Christoph Rothmann. The latter was a committed Copernican, and Tycho's forceful arguments for the superiority of his own cosmology was one reason for his publication of the letters. Other works begun on Hven were the Astronomiae instauratae mechanica (1598), an illustrated account of his instruments and observatories, and the Astronomiae instauratae progymnasmata (1602), which contained his theory of lunar and solar motions, part of his catalogue of stars, and a more detailed analysis of the supernova of 1572. However, the erosion of Tycho's funding and standing following King Christian IV's attainment of his majority caused the astronomer to leave Denmark in 1597. In 1599 he settled near Prague, having been appointed Imperial Mathematician by Emperor Rudolph II, and was joined by Johannes Kepler the following year. He died of uraemia in 1601.

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