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|Tycho Ottesen Brahe|
Brahe wearing the Order of the Elephant
|Born||14 December 1546|
Knutstorp Castle, Scania, Denmark, Denmark–Norway
|Died||24 October 1601 (aged 54)|
Prague, Holy Roman Empire
|Spouse(s)||Kirsten Barbara Jørgensdatter|
|Parents||Otte Brahe and Beate Bille|
|Tycho Ottesen Brahe|
Brahe wearing the Order of the Elephant
|Born||14 December 1546|
Knutstorp Castle, Scania, Denmark, Denmark–Norway
|Died||24 October 1601 (aged 54)|
Prague, Holy Roman Empire
|Spouse(s)||Kirsten Barbara Jørgensdatter|
|Parents||Otte Brahe and Beate Bille|
Tycho Brahe listen (help·info) (14 December 1546 – 24 October 1601), born Tyge Ottesen Brahe, was a Danish nobleman known for his accurate and comprehensive astronomical and planetary observations. He was born in Scania, then part of Denmark, now part of modern-day Sweden. Tycho was well known in his lifetime as an astronomer and alchemist and has been described more recently as "the first competent mind in modern astronomy to feel ardently the passion for exact empirical facts."
In his De nova stella (On the new star) of 1573, he refuted the Aristotelian belief in an unchanging celestial realm. His precise measurements indicated that "new stars," (stellae novae, now known as supernovae) in particular that of 1572, lacked the parallax expected in sub-lunar phenomena, and were therefore not "atmospheric" tailless comets as previously believed, but were above the atmosphere and moon. Using similar measurements he showed that comets were also not atmospheric phenomena, as previously thought, and must pass through the supposedly "immutable" celestial spheres.
As an astronomer, Tycho worked to combine what he saw as the geometrical benefits of the Copernican system with the philosophical benefits of the Ptolemaic system into his own model of the universe, the Tychonic system. Furthermore, he was the last of the major naked eye astronomers, working without telescopes for his observations.
Tycho Brahe was granted an estate on the island of Hven and the funding to build the Uraniborg, an early research institute, where he built large astronomical instruments and took many careful measurements, and later Stjerneborg, underground, when he discovered that his instruments in the former were not sufficiently steady. On the island (on which he demonstrated autocratic character and behavior toward the residents) he founded manufactories such as paper-making to provide material for printing his results.
After disagreements with the new Danish king Christian IV in 1597, he was invited by the Bohemian king and Holy Roman emperor Rudolph II to Prague, where he became the official imperial astronomer. He built the new observatory at Benátky nad Jizerou. There, from 1600 until his death in 1601, he was assisted by Johannes Kepler who later used Tycho's astronomical data to develop his three laws of planetary motion.
Tycho was born at his family's ancestral seat of Knutstorp Castle (Danish: Knudstrup borg; Swedish: Knutstorps borg), about eight kilometres north of Svalöv in then Danish Scania, now Swedish, to Otte Brahe (of the Brahe family) and Beate Bille (of the Bille family). His twin brother died before being baptized. Tycho wrote a Latin ode to his dead twin, which was printed in 1572 as his first published work. He also had two sisters, one older (Kirstine Brahe) and one younger (Sophia Brahe).
Otte Brahe, Tycho's father, was a nobleman and an important figure at the court of the Danish king. His mother, Beate Bille, came from an important family that had produced leading churchmen and politicians. Both parents are buried under the floor of Kågeröd Church, four kilometres east of Knutstorp. An epitaph, originally from Knutstorp, but now on a plaque near the church door, shows the whole family, including Tycho as a boy.
Tycho later wrote that when he was around age two, his uncle, Danish nobleman Jørgen Thygesen Brahe, "without the knowledge of my parents took me away with him while I was in my earliest youth to become a scholar". Apparently, this did not lead to dispute, nor did his parents attempt to get him back. According to one source, Tycho's parents had promised to hand over a boy child to Jørgen and his wife, who were childless, but had not honoured this promise. Jørgen seems to have taken matters into his own hands and took the child away to his own residence, Tosterup Castle.
Tycho attended Latin school from ages 6 to 12, but the name of the school is not known. It is also thought he may have been taught by a private tutor between these ages. At age 12, on 19 April 1559, Tycho began studies at the University of Copenhagen. There, following his uncle's wishes, he studied law, but also studied a variety of other subjects and became interested in astronomy. The solar eclipse of 21 August 1560, especially the fact that it had been predicted, so impressed him that he began to make his own studies of astronomy, helped by some of the professors. He purchased an ephemeris and books on astronomy, including Johannes de Sacrobosco's De sphaera mundi, Petrus Apianus's Cosmographia seu descriptio totius orbis and Regiomontanus's De triangulis omnimodis. Jørgen Thygesen Brahe, however, wanted Tycho to educate himself in order to become a civil servant, and sent him on a study tour of Europe in early 1562. Tycho was given the 19-year-old Anders Sørensen Vedel as mentor, whom he eventually talked into allowing the pursuit of astronomy during the tour.
Tycho realized that progress in astronomy required systematic, rigorous observation, night after night, using the most accurate instruments obtainable. This program became his life's work. Tycho improved and enlarged existing instruments, and built entirely new ones. His sister Sophia assisted Tycho in many of his measurements. Tycho was the last major astronomer to work without the aid of a telescope, soon to be turned skyward by Galileo and others.
Tycho jealously guarded his large body of celestial measurements, which Kepler took under his care following Tycho's death.
While studying at the University of Rostock in Germany, on 29 December 1566 Tycho lost part of his nose in a sword duel against fellow Danish nobleman (and his third cousin), Manderup Parsberg. Tycho had earlier quarrelled with Parsbjerg over the legitimacy of a mathematical formula, at a wedding dance at professor Lucas Bachmeister's house on the 10th, and again on the 27th. Since neither had the resources to prove the other wrong, they ended up resolving the issue with a duel. Though the two later reconciled, the duel two days later (in the dark) resulted in Tycho losing the bridge of his nose. From this event Tycho became interested in medicine and alchemy. For the rest of his life, he was said to have worn a replacement made of silver and gold, using a paste or glue to keep it attached. Some people, such as Fredric Ihren and Cecil Adams, have suggested that the false nose also had copper. Ihren wrote that when Tycho's tomb was opened on June 24, 1901, green marks were found on his skull, suggesting copper. Cecil Adams also mentions a green coloring and that medical experts examined the remains. Some historians have speculated that he wore different prosthetics for different occasions, noting that a copper nose would have been more comfortable and less heavy than a precious metal one. Nonetheless, in November 2012, Danish and Czech researchers, after chemically analyzing "a small bone sample from the nose" from the body exhumed in 2010, reported the prosthetic was "made out of brass".
His uncle and foster father, Jørgen Brahe, died in 1565 of pneumonia after rescuing Frederick II of Denmark from drowning. In April 1567, Tycho returned home from his travels and his father wanted him to take up law, but Tycho was allowed to make trips to Rostock, then on to Augsburg (where he built a great quadrant), Basel, and Freiburg. At the end of 1570 he was informed about his father's ill health, so he returned to Knutstorp Castle, where his father died on 9 May 1571. Soon after, his other uncle, Steen Bille, helped him build an observatory and alchemical laboratory at Herrevad Abbey.
Towards the end of 1571, Tycho fell in love with Kirsten, daughter of Jørgen Hansen, the Lutheran minister in Knudstrup. She was a commoner, and Tycho never formally married her. However, under Danish law, when a nobleman and a common woman lived together openly as husband and wife, and she wore the keys to the household at her belt like any true wife, their alliance became a binding morganatic marriage after three years. The husband retained his noble status and privileges; the wife remained a commoner. Their children were legitimate in the eyes of the law, but they were commoners like their mother and could not inherit their father's name, coat of arms, or landholdings. However, Kirsten and Tycho's children were later testified as legitimate by Tycho's younger sister, Sophie.
Kirsten Jørgensdatter gave birth to their first daughter, Kirstine (named after Tycho's late sister, who died at 13) on October 12, 1573. Together they had eight children, six of whom lived to adulthood. In 1574, they moved to Copenhagen where their daughter Magdalene was born. Kirsten and Tycho lived together for almost thirty years until Tycho's death.
Tycho was said[by whom?] to own one percent of the entire wealth of Denmark at one point in the 1580s.[better source needed] Tycho often held large social gatherings in his castle. Pierre Gassendi wrote that Tycho also had a tame elk (moose) and that his mentor the Landgrave Wilhelm of Hesse-Kassel (Hesse-Cassel) asked whether there was an animal faster than a deer. Tycho replied, writing that there was none, but he could send his tame elk. When Wilhelm replied he would accept one in exchange for a horse, Tycho replied with the sad news that the elk had just died on a visit to entertain a nobleman at Landskrona. Apparently during dinner the elk had drunk a lot of beer, fallen down the stairs, and died.
Tycho suddenly contracted a bladder or kidney ailment after attending a banquet in Prague, and died eleven days later, on 24 October 1601. According to Kepler's first hand account, Tycho had refused to leave the banquet to relieve himself because it would have been a breach of etiquette. After he had returned home he was no longer able to urinate, except eventually in very small quantities and with excruciating pain. The night before he died he suffered from a delirium during which he was frequently heard to exclaim that he hoped he would not seem to have lived in vain. Before dying, he urged Kepler to finish the Rudolphine Tables and expressed the hope that he would do so by adopting Tycho's own planetary system, rather than that of Copernicus. It was reported that Brahe himself had written his own epitaph, stating "He lived like a sage and died like a fool". A contemporary physician attributed his death to a kidney stone, but no kidney stones were found during an autopsy performed after his body was exhumed in 1901, and the 20th century medical assessment is that it is more likely to have resulted from uremia.
Recent investigations have suggested that Tycho did not die from urinary problems but instead from mercury poisoning—extremely toxic levels of it have been found in hairs from his moustache. This may have even been due to the various metals used to create his prosthetic noses. The results were, however, not conclusive.
Some modern theories suggest that due to the discovery of the mercury in his body, it is possible he was intentionally or unintentionally poisoned. The two main suspects are his assistant, Johannes Kepler, whose motives would be to gain access to Brahe's laboratory and chemicals, and his cousin, Erik Brahe, at the order of friend-turned-enemy Christian IV due to rumors at the time that Tycho had had an affair with Christian's mother.
Prague City Hall approved a request by Danish scientists to exhume the remains in February 2010, and a team of Czech and Danish scientists from Aarhus University arrived in November 2010, to take bone, hair and clothing samples for analysis. The scientists, led by Dr Jens Vellev, analyzed Tycho's beard hair once again. The team reported in November 2012 that not only was there not enough mercury present to substantiate murder, but that there were no lethal levels of any poisons present. The team's conclusions was that "it is impossible that Tycho Brahe could have been murdered"  and that he "most likely died of a burst bladder". The findings were confirmed by scientists from the University of Rostock who examined a sample of Brahe's beard hairs that had been taken in 1901. Although traces of mercury were found, these were present only in the outer scales. Therefore a mercury poisoning as the cause of death was ruled out while the study suggests that the accumulation of mercury may have come from the "precipitation of mercury dust from the air during [Brahe's] long-term alchemistic activities."
On 11 November 1572, Tycho observed (from Herrevad Abbey) a very bright star, now named SN 1572, which had unexpectedly appeared in the constellation Cassiopeia. Because it had been maintained since antiquity that the world beyond the Moon's orbit was eternally unchangeable (celestial immutability was a fundamental axiom of the Aristotelian world-view), other observers held that the phenomenon was something in the terrestrial sphere below the Moon. However, in the first instance Tycho observed that the object showed no daily parallax against the background of the fixed stars. This implied it was at least farther away than the Moon and those planets that do show such parallax. He also found the object did not change its position relative to the fixed stars over several months as all planets did in their periodic orbital motions, even the outer planets for which no daily parallax was detectable. This suggested it was not even a planet, but a fixed star in the stellar sphere beyond all the planets. In 1573 he published a small book, De nova stella thereby coining the term nova for a "new" star (we now classify this star as a supernova and we know that it is 7500 light-years from Earth). This discovery was decisive for his choice of astronomy as a profession. Tycho was strongly critical of those who dismissed the implications of the astronomical appearance, writing in the preface to De nova stella: "O crassa ingenia. O caecos coeli spectatores" ("Oh thick wits. Oh blind watchers of the sky").
Tycho's discovery was the inspiration for Edgar Allan Poe's poem "Al Aaraaf". In 1998, Sky & Telescope magazine published an article by Donald W. Olson, Marilynn S. Olson and Russell L. Doescher arguing, in part, that Tycho's supernova was also the same "star that's westward from the pole" in Shakespeare's Hamlet.
In 1574, Tycho published the observations made in 1572 from his first observatory at Herrevad Abbey. He then started lecturing on astronomy, but gave it up and left Denmark in spring 1575 to tour abroad. He first visited William IV, Landgrave of Hesse-Kassel's observatory at Kassel, then went on to Frankfurt, Basel and Venice. Upon his return he intended to relocate to Basel, but King Frederick II of Denmark, desiring to keep the distinguished scientist, offered Tycho the island of Hven in Oresund and funding to set up an observatory. Tycho built the observatory Uraniborg on Hven in 1576 (with a laboratory for his alchemical experiments in its cellar) and then Stjerneborg nearby in 1581. Unusual for the time, Tycho established Uraniborg as a research centre, where almost 100 students and artisans worked from 1576 to 1597.
After Frederick died in 1588 and his 11-year-old son, Christian IV, succeeded him, Tycho's influence steadily declined. After several unpleasant disagreements, Tycho left Hven in 1597. The instruments he had used in Uraniborg and Stjerneborg were depicted and described in detail in his book Astronomiae instauratae mechanica, first published in 1598.
He moved to Prague in 1599. Sponsored by Rudolf II, Holy Roman Emperor, Tycho built a new observatory in a castle in Benátky nad Jizerou, 50 km from Prague, and worked there for one year. The emperor then brought him back to Prague, where he stayed until his death. Tycho received financial support from several nobles in addition to the emperor, including Oldrich Desiderius Pruskowsky von Pruskow, to whom he dedicated his famous "Mechanica". In return for their support, Tycho's duties included preparing astrological charts and predictions for his patrons on events such as births, weather forecasting, and astrological interpretations of significant astronomical events, such as the supernova of 1572 (sometimes called Tycho's supernova) and the Great Comet of 1577.
The year 1588, which saw the death of his royal benefactor, saw also the publication of a volume of Tycho's great work Astronomiæ Instauratæ Progymnasmata or "Introduction to the New Astronomy". The first volume, devoted to the new star of 1572, was not ready, because the reduction of the observations of 1572-3 involved so much research to correct the star places for refraction, precession, the motion of the sun etc., and was not completed in Tycho's lifetime, but the second volume, devoted to the comet of 1577, was printed at Uraniborg and some copies were issued in 1588. Besides the comet observations it included an account of Tycho's system of the world. The third volume was to treat the comets of 1580 and following years in a similar manner, but it was never published, nor even written, though a great deal of material about the comet of 1585 was put together and first published in 1845 with the observations of this comet.
Tycho's observations of stellar and planetary positions were noteworthy both for their accuracy and quantity. His celestial positions were much more accurate than those of any predecessor or contemporary. Rawlins (1993, §B2) asserts of Tycho's Star Catalog D, "In it, Tycho achieved, on a mass scale, a precision far beyond that of earlier catalogers. Cat D represents an unprecedented confluence of skills: instrumental, observational, & computational—all of which combined to enable Tycho to place most of his hundreds of recorded stars to an accuracy of ordermag 1'!"
He aspired to a level of accuracy in his estimated positions of celestial bodies of being consistently within 1 arcminute of their real celestial locations, and also claimed to have achieved this level. But in fact many of the stellar positions in his star catalogues were less accurate than that. The median errors for the stellar positions in his final published catalog were about 1'.5, indicating that only half of the entries were more accurate than that, with an overall mean error in each coordinate of around 2'. Although the stellar observations as recorded in his observational logs were more accurate, varying from 32.3" to 48.8" for different instruments, systematic errors of as much as 3' were introduced into some of the stellar positions Tycho published in his star catalog - due for instance, to his application of an erroneous ancient value of parallax and his neglect of polestar refraction. Incorrect transcription in the final published star catalogue, by scribes in Brahe's employ, was the source of even larger errors, sometimes by many degrees.
After Tycho's death, Kepler used his records of the motion of Mars to deduce his own laws of planetary motion. Kepler's application of these two laws to obtain astronomical tables of unprecedented accuracy (the Rudolphine Tables) provided powerful support for his heliocentric model of the solar system.
Celestial objects observed near the horizon and above appear with a greater altitude than the real one, due to atmospheric refraction, and one of Tycho's most important innovations was that he worked out and published the very first tables for the systematic correction of this possible source of error. But as advanced as they were, they attributed no refraction whatever above 45 degrees altitude for solar refraction, and none for starlight above 20 degrees altitude.
To perform the huge number of multiplications needed to produce much of his astronomical data, Tycho relied heavily on the then-new technique of prosthaphaeresis, an algorithm for approximating products based on trigonometric identities that predated logarithms.
Tycho was not a Copernican, but proposed a "geo-heliocentric" system in which the Sun and Moon orbited the Earth, while the other planets orbited the Sun. His system provided a safe position for astronomers who were dissatisfied with older models but were reluctant to accept the Earth's motion. It gained a considerable following after 1616 when Rome decided officially that the heliocentric model was contrary to both philosophy and Scripture, and could be discussed only as a computational convenience that had no connection to fact. His system also offered a major innovation: while both the purely geocentric model and the heliocentric model as set forth by Copernicus relied on the idea of transparent rotating crystalline spheres to carry the planets in their orbits, Tycho eliminated the spheres entirely. Kepler tried, but was unable, to persuade Tycho to adopt the heliocentric model of the solar system. Tycho advocated for a system with an unmoving Earth for reasons of physics, astronomical observations of stars, and religion.
In regards to physics, Tycho held that the Earth was just too sluggish and heavy to be continuously in motion. According to the accepted Aristotelian physics of the time, the heavens (whose motions and cycles were continuous and unending) were made of "Aether" or "Quintessence"; this substance, not found on Earth, was light, strong, unchanging, and its natural state was circular motion. By contrast, the Earth (where objects seem to have motion only when moved) and things on it were composed of substances that were heavy and whose natural state was rest. Accordingly, Tycho said the Earth was a "lazy" body that was not readily moved. Thus while Tycho acknowledged that the daily rising and setting of the sun and stars could be explained by the Earth's rotation, as Copernicus had said, still
such a fast motion could not belong to the earth, a body very heavy and dense and opaque, but rather belongs to the sky itself whose form and subtle and constant matter are better suited to a perpetual motion, however fast.
In regards to the stars, Tycho also believed that if the Earth orbited the Sun annually there should be an observable stellar parallax over any period of six months, during which the angular orientation of a given star would change thanks to Earth's changing position. (This parallax does exist, but is so small it was not detected until 1838, when Friedrich Bessel discovered a parallax of 0.314 arcseconds of the star 61 Cygni.) The Copernican explanation for this lack of parallax was that the stars were such a great distance from Earth that Earth's orbit was almost insignificant by comparison. However, Tycho noted that this explanation introduced another problem: Stars as seen by the naked eye appear small, but of some size, with more prominent stars such as Vega appearing larger than lesser stars such as Polaris, which in turn appear larger than many others. Tycho had determined that a typical star measured approximately a minute of arc in size, with more prominent ones being two or three times as large. In writing to Christoph Rothmann, a Copernican astronomer, Tycho used basic geometry to show that, assuming a small parallax that just escaped detection, the distance to the stars in the Copernican system would have to be 700 times greater than the distance from the sun to Saturn. Moreover, the only way the stars could be so distant and still appear the sizes they do in the sky would be if even average stars were gigantic — at least as big as the orbit of the Earth, and of course vastly larger than the sun. And, Tycho said, the more prominent stars would have to be even larger still. And what if the parallax was even smaller than anyone thought, so the stars were yet more distant? Then they would all have to be even larger still. Tycho said
Deduce these things geometrically if you like, and you will see how many absurdities (not to mention others) accompany this assumption [of the motion of the earth] by inference.
Copernicans offered a religious response to Tycho's geometry: titanic, distant stars might seem unreasonable, but they were not, for the Creator could make his creations that large if He wanted. In fact, Rothmann responded to this argument of Tycho's by saying
[W]hat is so absurd about [an average star] having size equal to the whole [orbit of the Earth]? What of this is contrary to divine will, or is impossible by divine Nature, or is inadmissible by infinite Nature? These things must be entirely demonstrated by you, if you will wish to infer from here anything of the absurd. These things that vulgar sorts see as absurd at first glance are not easily charged with absurdity, for in fact divine Sapience and Majesty is far greater than they understand. Grant the vastness of the Universe and the sizes of the stars to be as great as you like — these will still bear no proportion to the infinite Creator. It reckons that the greater the king, so much greater and larger the palace befitting his majesty. So how great a palace do you reckon is fitting to GOD?.
Religion played a role in Tycho's geocentrism also – he cited the authority of scripture in portraying the Earth as being at rest. He rarely used Biblical arguments alone (to him they were a secondary objection to the idea of Earth's motion) and over time he came to focus on scientific arguments, but he did take Biblical arguments seriously.
Tycho advocated an alternative to the Ptolemaic geocentric system: A "geo-heliocentric" system now known as the Tychonic system, which he developed in the late 1570s. In such a system, the sun, moon, and stars circle a central Earth, while the five planets orbit the Sun. The essential difference between the heavens (including the planets) and the Earth remained: Motion stayed in the aethereal heavens; immobility stayed with the heavy sluggish Earth. It was a system that Tycho said violated neither the laws of physics nor sacred scripture — with stars located just beyond Saturn and of reasonable size.
Tycho was not the first to propose a geoheliocentric system. It used to be thought that Heraclides in the 4th century BC had suggested that Mercury and Venus revolve around the Sun, which in turn (along with the other planets) revolves around the Earth. Macrobius Ambrosius Theodosius (395–423 AD) later described this as the "Egyptian System," stating that "it did not escape the skill of the Egyptians," though there is no other evidence it was known in ancient Egypt. The difference was that Tycho's system had all the planets (with the exception of Earth) revolving around the Sun, instead of just the interior planets of Mercury and Venus. In this regard, he was anticipated in the 15th century by the Kerala school astronomer Nilakantha Somayaji, whose geoheliocentric system also had all the planets revolving around the Sun. The difference to both these systems was that Tycho's model of the Earth does not rotate daily, as Heraclides and Nilakantha claimed, but is static.
Another crucial difference between Tycho's 1587 geo-heliocentric model and those of other geo-heliocentric astronomers, such as Paul Wittich, Reimarus Ursus, Helisaeus Roeslin and David Origanus, was that the orbits of Mars and the Sun intersected. This was because Tycho had come to believe the distance of Mars from the Earth at opposition (that is, when Mars is on the opposite side of the sky from the Sun) was less than that of the Sun from the Earth. Tycho believed this because he came to believe Mars had a greater daily parallax than the Sun. But in 1584 in a letter to a fellow astronomer, Brucaeus, he had claimed that Mars had been further than the Sun at the opposition of 1582, because he had observed that Mars had little or no daily parallax. He said he had therefore rejected Copernicus's model because it predicted Mars would be at only two-thirds the distance of the Sun. But he apparently later changed his mind to the opinion that Mars at opposition was indeed nearer the Earth than the Sun was, but apparently without any valid observational evidence in any discernible Martian parallax. Such intersecting Martian and solar orbits meant that there could be no solid rotating celestial spheres, because they could not possibly interpenetrate. Arguably this conclusion was independently supported by the conclusion that the comet of 1577 was superlunary, because it showed less daily parallax than the Moon and thus must pass through any celestial spheres in its transit.
Galileo's 1610 telescopic discovery that Venus shows a full set of phases refuted the pure geocentric Ptolemaic model. After that it seems 17th century astronomy mostly converted to geo-heliocentric planetary models that could explain these phases just as well as the heliocentric model could, but without the latter's disadvantage of the failure to detect any annual stellar parallax that Tycho and others regarded as refuting it. The three main geo-heliocentric models were the Tychonic, the Capellan with just Mercury and Venus orbiting the Sun such as favoured by Francis Bacon, for example, and the extended Capellan model of Riccioli with Mars also orbiting the Sun whilst Saturn and Jupiter orbit the fixed Earth. But the Tychonic model was probably the most popular, albeit probably in what was known as 'the semi-Tychonic' version with a daily rotating Earth. This model was advocated by Tycho's ex-assistant and disciple Longomontanus in his 1622 Astronomia Danica that was the intended completion of Tycho's planetary model with his observational data, and which was regarded as the canonical statement of the complete Tychonic planetary system.
A conversion of astronomers to geo-rotational geo-heliocentric models with a daily rotating Earth such as that of Longomontanus may have been precipitated by Francesco Sizzi's 1613 discovery of annually periodic seasonal variations of sunspot trajectories across the sun's disc. They appear to oscillate above and below its apparent equator over the course of the four seasons. This seasonal variation is explained much better by the hypothesis of a daily rotating Earth together with that of the sun's axis being tilted throughout its supposed annual orbit than by that of a daily orbiting sun, if not even refuting the latter hypothesis because it predicts a daily vertical oscillation of a sunspot's position, contrary to observation. This discovery and its import for heliocentrism, but not for geo-heliocentrism, is discussed in the Third Day of Galileo's 1632 Dialogo. However, prior to that discovery, in the late 16th century the geo-heliocentric models of Ursus and Roslin had featured a daily rotating Earth, unlike Tycho's geo-static model, as indeed had that of Heraclides in antiquity, for whatever reason.
The fact that Longomontanus's book was republished in two later editions in 1640 and 1663 no doubt reflected the popularity of Tychonic astronomy in the 17th century. Its adherents included John Donne and the atomist and astronomer Pierre Gassendi.
The ardent anti-heliocentric French astronomer Jean-Baptiste Morin devised a Tychonic planetary model with elliptical orbits published in 1650 in a simplified, Tychonic version of the Rudolphine Tables. Some acceptance of the Tychonic system persisted through the 17th century and in places until the early 18th century; it was supported (after a 1633 decree about the Copernican controversy) by "a flood of pro-Tycho literature" of Jesuit origin. Among pro-Tycho Jesuits, Ignace Pardies declared in 1691 that it was still the commonly accepted system, and Francesco Blanchinus reiterated that as late as 1728. Persistence of the Tychonic system, especially in Catholic countries, has been attributed to its satisfaction of a need (relative to Catholic doctrine) for "a safe synthesis of ancient and modern". After 1670, even many Jesuit writers only thinly disguised their Copernicanism. But in Germany, Holland, and England, the Tychonic system "vanished from the literature much earlier".
James Bradley's discovery of stellar aberration, published in 1729, eventually gave direct evidence excluding the possibility of all forms of geocentrism including Tycho's. Stellar aberration could only be satisfactorily explained on the basis that the Earth is in annual orbit around the Sun, with an orbital velocity that combines with the finite speed of the light coming from an observed star or planet, to affect the apparent direction of the body observed.
Tycho's distinctive contributions to lunar theory include his discovery of the variation of the Moon's longitude. This represents the largest inequality of longitude after the equation of the center and the evection. He also discovered librations in the inclination of the plane of the lunar orbit, relative to the ecliptic (which is not a constant of about 5° as had been believed before him, but fluctuates through a range of over a quarter of a degree), and accompanying oscillations in the longitude of the lunar node. These represent perturbations in the Moon's ecliptic latitude. Tycho's lunar theory doubled the number of distinct lunar inequalities, relative to those anciently known, and reduced the discrepancies of lunar theory to about 1/5 of their previous amounts. It was published posthumously by Kepler in 1602, and Kepler's own derivative form appears in Kepler's Rudolphine Tables of 1627.
Although Tycho's planetary model was soon discredited, his astronomical observations were an essential contribution to the scientific revolution. The traditional view of Tycho is that he was primarily an empiricist who set new standards for precise and objective measurements. This appraisal originated in Pierre Gassendi's 1654 biography, Tychonis Brahe, equitis Dani, astronomorum coryphaei, vita. It was furthered by Johann Dreyer's biography in 1890, which was long the most influential work on Tycho. According to historian of science Helge Kragh, this assessment grew out of Gassendi's opposition to Aristotelianism and Cartesianism, and fails to account for the diversity of Tycho's activities.
Tycho considered astrology to be a subject of great importance. In addition to his contributions to astronomy, he was famous in his own time also for his contributions to medicine; his herbal medicines were in use as late as the 1900s.
Although the research community Tycho created in Uraniborg did not survive him, while it existed it was both a research center and an institution of education, functioning as a graduate school for Danish and foreign students in both astronomy and medicine. Tycho's success as a scientist also depended on his adroit political skills, to obtain patronage and funding for his work.
HEAT1X-TYCHO BRAHE is the name of a manned private spacecraft to be launched by Copenhagen Suborbitals. Other things named after him include a bar in Zagreb and a ferry operating between Sweden and Denmark.
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