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Tycho's observations of [[star|stellar]] and [[planet]]ary positions were noteworthy both for their accuracy and quantity.<ref>Noel Swerdlow, ''Astronomy in the Renaissance'', pp. 187-230 in Christopher Walker, ed., ''Astronomy before the Telescope'', (London: British Museum Press, 1996), pp. 207-10.</ref> He aspired to a level of accuracy in his estimated positions of celestial bodies of being consistently within 1 [[minute of arc|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 far less accurate than that. Only for the brighter stars in his final catalog did Tycho achieve a mean error of less than 1'. For dimmer stars, the mean error was closer to 3'.<ref>[[#Reference-Rawlins-1993|Rawlins 1993]]</ref> Maximum errors in the star charts were plagued by difficulties such as errors in transcription due to the scribes in Brahe's employ. His planetary positions had a maximum error at least in excess of 3', and even the mean error of his 1577 comet orbital positions was as much as 4', suggesting a possibly much greater maximum error.<ref>There is considerable conflict and confusion in the history of science literature about what level of accuracy Tycho consistently achieved in his celestial positions, but the following 10 references, including Kepler, all testify to it being less than within 1 arcminute as Tycho reportedly claimed to have actually achieved.
Tycho's observations of [[star|stellar]] and [[planet]]ary positions were noteworthy both for their accuracy and quantity.<ref>Noel Swerdlow, ''Astronomy in the Renaissance'', pp. 187-230 in Christopher Walker, ed., ''Astronomy before the Telescope'', (London: British Museum Press, 1996), pp. 207-10.</ref> He aspired to a level of accuracy in his estimated positions of celestial bodies of being consistently within 1 [[minute of arc|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 far less accurate than that. Only for the brighter stars in his final catalog did Tycho achieve a mean error of less than 1'. For dimmer stars, the mean error was closer to 3'.<ref>[[#Reference-Rawlins-1993|Rawlins 1993]]</ref> Maximum errors in the star charts were plagued by difficulties such as errors in transcription due to the scribes in Brahe's employ. His planetary positions had a maximum error at least in excess of 3', and even the mean error of his 1577 comet orbital positions was as much as 4', suggesting a possibly much greater maximum error.<ref>There is considerable conflict and confusion in the history of science literature about what level of accuracy Tycho consistently achieved in his celestial positions, but the following 10 references, including Kepler, all testify to it being less than within 1 arcminute as Tycho reportedly claimed to have actually achieved.
(i) Dreyer’s 1890 ''Tycho Brahe'' p387 found a max error of 2' 2" in the positions of 9 'standard' stars (in the declination of Alpha Virginis) compared with Bradley’s positions retrodicted from his 1755 positions, and two of those 9 stars in excess of 1' error. (ii)Thoren’s 1989 ''Tycho Brahe'' p16 found many errors greater than 1’. Thoren says: "[the accuracy of the 777 star catalogue C] falls below the standards Tycho maintained for his other activities....the catalogue left the best qualified appraiser of it (Tycho's eminent biographer J.L.E. Dreyer) manifestly disappointed. Some 6% of its final 777 positions have errors in one or both co-ordinates that can only have arisen from 'handling' problems of one kind or another. And while the brightest stars were generally placed with the minute-of-arc accuracy Tycho expected to achieve in every aspect of his work, the fainter stars (for which the slits on his sights had to be widened, and the sharpness of their alignment reduced) were considerably less well located." (iii) Hoskin's 1999 p101 concurs with Thoren's finding "Yet although the places of the brightest of the non-reference stars [in the 777 star catalogue] are mostly correct to around the minute of arc that was his standard, the fainter stars are less accurately located, and there are many errors.".(iv) Wesley’s 1978 found max errors in at least the order of some 2' in individual instrument measurements for 8 of 9 fundamental stars, with a 123" error in declination by the Northern Equatorial Armillary for only 5 of 9 fundamental stars in Table 3 p47, and 115.5" declination error for Arietis by the Mural Quadrant in Table 1 p44. He comments: "For the majority of stars that appear in Tycho's final star catalogue the overall accuracy might be much less [than that of the 8 fundamental stars Wesley considers]; for there were fewer measurements taken for them, and in many cases the final positions were reduced from sextant readings of distances from some of the fundamental stars or other common ones. In these cases errors might be compounded through the calculations." [p45]. (v) Swerdlow's 1996 p210 reports Kepler considered Tycho's reduced observations of planets to be accurate only within 2'.(vi) Swerdlow 1996 p209 himself claimed "Various statistical evaluations of his [Tycho's] observations have been made with different results, but it is safe to say that fundamental stars and solar altitudes were measured to considerably less than 1'...". But this summary conclusion of the literature is apparently blatantly contradicted as unsafe and unreliable by Dreyer's 1890 evaluation, Wesley's 1978 evaluation and Rawlins' 1993 evaluation of the errors in Tycho's 9 'fundamental' reference star positions, which all found errors exceeding 1' in at least a third of them, and a maximum error exceeding 2'. And of course Tycho's solar altitudes had a maximum error of almost 3', as even Swerdlow himself, amongst many others, points out, and Pannekoek's 1961 p213 reported an error of 1.5' in his solar altitude at summer solstice.
(i) Dreyer’s 1890 ''Tycho Brahe'' p387 found a max error of 2' 2" in the positions of 9 'standard' stars (in the declination of Alpha Virginis) compared with Bradley’s positions retrodicted from his 1755 positions, and two of those 9 stars in excess of 1' error. (ii)Thoren’s 1989 ''Tycho Brahe'' p16 found many errors greater than 1’. Thoren says: "[the accuracy of the 777 star catalogue C] falls below the standards Tycho maintained for his other activities....the catalogue left the best qualified appraiser of it (Tycho's eminent biographer J.L.E. Dreyer) manifestly disappointed. Some 6% of its final 777 positions have errors in one or both co-ordinates that can only have arisen from 'handling' problems of one kind or another. And while the brightest stars were generally placed with the minute-of-arc accuracy Tycho expected to achieve in every aspect of his work, the fainter stars (for which the slits on his sights had to be widened, and the sharpness of their alignment reduced) were considerably less well located." (iii) Hoskin's 1999 p101 concurs with Thoren's finding "Yet although the places of the brightest of the non-reference stars [in the 777 star catalogue] are mostly correct to around the minute of arc that was his standard, the fainter stars are less accurately located, and there are many errors.".(iv) Wesley’s 1978 found max errors in at least the order of some 2' in individual instrument measurements for 8 of 9 fundamental stars, with a 123" error in declination by the Northern Equatorial Armillary for only 5 of 9 fundamental stars in Table 3 p47, and 115.5" declination error for Arietis by the Mural Quadrant in Table 1 p44. He comments: "For the majority of stars that appear in Tycho's final star catalogue the overall accuracy might be much less [than that of the 8 fundamental stars Wesley considers]; for there were fewer measurements taken for them, and in many cases the final positions were reduced from sextant readings of distances from some of the fundamental stars or other common ones. In these cases errors might be compounded through the calculations." [p45]. (v) Swerdlow's 1996 p210 reports Kepler considered Tycho's reduced observations of planets to be accurate only within 2'.(vi) Swerdlow 1996 p209 himself claimed "Various statistical evaluations of his [Tycho's] observations have been made with different results, but it is safe to say that fundamental stars and solar altitudes were measured to considerably less than 1'...". But this summary conclusion of the literature is apparently contradicted by Dreyer's 1890 evaluation, Wesley's 1978 evaluation and Rawlins' 1993 evaluation of the errors in Tycho's 9 'fundamental' reference star positions, which all found errors exceeding 1' in at least a third of them, and a maximum error exceeding 2'. And of course Tycho's solar altitudes had a maximum error of almost 3', as even Swerdlow himself, amongst many others, points out, and Pannekoek's 1961 p213 reported an error of 1.5' in his solar altitude at summer solstice.
(vii) Pannekoek's 1961 p212 reports an error of +2' in the Earth's obliquity; p213 says there is an error in the solar altitude at summer solstice of 1.5'; and p215 reports a mean error of 4' in positions of the 1577 comet. (viii) But the greatest max errors are given in Rawlins' 1993. They are in descending order a 238 degrees scribal error in the right ascension of star D723; a 36 degrees scribal error in the right ascension of D811 (p42); a 23 degrees latitude error in all 188 southern stars by virtue of a scribal error (p42 M5), which would alone increase the whole catalogue's mean error by more than 4 degrees; a 20 degrees scribal error in longitude of D429; and a 13.5 degrees error in the latitude of D811. He also reported that (ix) Pledge 1939 "repeats the widely believed contention that Tycho's mean error was 4'.", and that (x) Rybka 1984 found a mean error of some 3' for nonbright stars on the basis of comparing only barely half the stars in star Catalogue D with "the modern FK4 star catalogue" values.</ref> Nevertheless historians of science typically assert his celestial positions were much more accurate than those of any predecessor or contemporary. For example, [[#Reference-Swerdlow-2004|Swerdlow (1996, p. 209)]] claims "The increase in precision Tycho achieved was extraordinary." [[#Reference-Rawlins-1993|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, &amp; computational&mdash;all of which combined to enable Tycho to place most of his hundreds of recorded stars to an accuracy of ordermag 1'!"
(vii) Pannekoek's 1961 p212 reports an error of +2' in the Earth's obliquity; p213 says there is an error in the solar altitude at summer solstice of 1.5'; and p215 reports a mean error of 4' in positions of the 1577 comet. (viii) But the greatest max errors are given in Rawlins' 1993. They are in descending order a 238 degrees scribal error in the right ascension of star D723; a 36 degrees scribal error in the right ascension of D811 (p42); a 23 degrees latitude error in all 188 southern stars by virtue of a scribal error (p42 M5), which would alone increase the whole catalogue's mean error by more than 4 degrees; a 20 degrees scribal error in longitude of D429; and a 13.5 degrees error in the latitude of D811. He also reported that (ix) Pledge 1939 "repeats the widely believed contention that Tycho's mean error was 4'.", and that (x) Rybka 1984 found a mean error of some 3' for nonbright stars on the basis of comparing only barely half the stars in star Catalogue D with "the modern FK4 star catalogue" values.</ref> Nevertheless historians of science typically assert his celestial positions were much more accurate than those of any predecessor or contemporary. For example, [[#Reference-Swerdlow-2004|Swerdlow (1996, p. 209)]] claims "The increase in precision Tycho achieved was extraordinary." [[#Reference-Rawlins-1993|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, &amp; computational&mdash;all of which combined to enable Tycho to place most of his hundreds of recorded stars to an accuracy of ordermag 1'!"


Revision as of 18:45, 6 November 2009

This article is about the astronomer. For the Penny Arcade character, see List of Penny Arcade characters.
Tycho Ottesen Brahe
Born14 December 1546
Knutstorp Castle, Scania, then Denmark, today Sweden
Died24 October 1601 (aged 54)
Prague
NationalityDanish
EducationPrivate
Occupation(s)Nobleman, Astronomer
SpouseKirstine Barbara Jørgensdatter
Children8
Parent(s)Otte Brahe and Beate Bille
Signature
Monument of Tycho Brahe and Johannes Kepler in Prague

Tycho Brahe, born Tyge Ottesen Brahe (de Knudstrup) (14 December 1546 – 24 October 1601), was a Danish nobleman known for his accurate and comprehensive astronomical and planetary observations. Coming from Scania, then part of Denmark, now part of modern-day Sweden, Tycho was well known in his lifetime as an astronomer and alchemist.

His Danish name "Tyge Ottesen Brahe" is pronounced in Modern Standard Danish as [ˈtˢyːə ˈʌd̥əsn̩ ˈb̥ʁɑː]. He adopted the Latinized name "Tycho Brahe" (usually Template:PronEng or /ˈbrɑːhiː/ in English) from Tycho (sometimes written Tÿcho) at around age fifteen, and he is now generally referred to as "Tycho" rather than by his surname "Brahe", as was common in Scandinavia in the 17th century.[1] (The incorrect form of his name, Tycho de Brahe, appeared only much later.[2])

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. After disagreements with the new king 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. Here, from 1600 until his death in 1601, he was assisted by Johannes Kepler. Kepler would later use Tycho's astronomical information to develop his own theories of astronomy.

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.

Tycho is credited with the most accurate astronomical observations of his time, and the data was used by his assistant Kepler to derive the laws of planetary motion. No one before Tycho had attempted to make so many planetary observations.

Life

Early years

Tycho was born at his family's ancestral seat of Knutstorp Castle (Danish: Knudstrup borg; Swedish: Knutstorps borg),[3] about eight kilometres north of Svalöv in then Danish Scania, now Swedish, to Otte Brahe and Beate Bille. His twin brother died before being baptized. Tycho wrote a Latin ode (Wittendorf 1994, p. 68) 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 2, his uncle, Danish nobleman Jørgen 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,[4] 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. Jørgen Brahe inherited considerable wealth from his parents, which in terms of the social structure of the time made him eligible for a royal appointment as county sheriff. He was successively sheriff to Tranekjær (1542-49), Odensegaard (1549-52), Vordingborg Castle(1552-57), and finally (1555 until his death in 1565) to Queen Dorothea[clarification needed] at Nykøbing Castle on Falster.[5]

Tycho attended Latin school from ages 6 to 12, but the name of the school is not known. 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. An eclipse on 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, including Sacrobosco's De sphaera mundi, Petrus Apianus's Cosmographia seu descriptio totius orbis[clarification needed] and Regiomontanus's De triangulis omnimodis. At age 17, Tycho wrote:

I've studied all available charts of the planets and stars and none of them match the others. There are just as many measurements and methods as there are astronomers and all of them disagree. What's needed is a long term project with the aim of mapping the heavens conducted from a single location over a period of several years.[citation needed]

Tycho realized that progress in the science of astronomy could only be achieved by systematic, and 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 "usurped" following Tycho's death.[6]

Brahe's nose

While a student, Tycho lost part of his nose in a duel[7] with Manderup Parsbjerg, a fellow Danish nobleman.[8] This occurred in the Christmas season of 1566, after a fair amount of drinking, while Tycho, just turned 20 years old, was studying at the University of Rostock in Rostock, Germany.[8] Attending a dance at a professor's house, he quarrelled with Parsbjerg. A subsequent duel (in the dark) resulted in Tycho losing the bridge of his nose. From this event Tycho became interested in medicine and alchemy.[7] For the rest of his life, he was said to have worn a realistic replacement made of silver and gold[7], using a paste to keep it attached.[8] 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 in 24 June 1901 green marks were found on his skull, suggesting copper.[8] Cecil Adams also mentions a green colouring and that medical experts examined the remains.[9] Some historians have speculated that he wore a number of different prosthetics for different occasions, noting that a copper nose would have been more comfortable and less heavy than a precious metal one.[10]

Death of his uncle

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 Knudstrup, where his father died on 9 May 1571.[7] Soon after, his other uncle, Steen Bille, helped him build an observatory and alchemical laboratory at Herrevad Abbey.[7]

Family life

In 1572, in Knudstrup, Tycho fell in love with Kirsten, daughter of Jørgen Hansen, the Lutheran priest 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. (Skautrup 1941, pp. 24-5)

Kirsten Jørgensdatter gave birth to their first daughter, Kirstine (named after Tycho's late sister, who died at 13) on 12 October 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's Moose (Elk)

Tycho was said to own one percent of the entire wealth of Denmark at one point in the 1580s and he often held large social gatherings in his castle. He kept a dwarf named Jepp (whom Tycho believed to be clairvoyant) as a court jester who sat under the table during dinner. Pierre Gassendi wrote[8] that Tycho also had a tame moose (called an Elk in Europe) 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 moose. When Wilhelm replied he would accept one in exchange for a horse, Tycho replied with the sad news that the moose had just died on a visit to entertain a nobleman at Landskrona. Apparently during dinner[11] the moose had drunk a lot of beer, fallen down the stairs, and died.[8][12]

Death

Tycho Brahe's grave in Prague, new tomb stone from 1901

Tycho suddenly contracted a bladder 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.[13] 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.[14] 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 Copernicus's. 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 modern medical assessment is that it is more likely to have resulted from uremia.[15]

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.[16][citation needed]

Tycho's body is currently interred in a tomb in the Church of Our Lady in front of Týn, in Old Town Square near the Prague Astronomical Clock.

Career: observing the heavens

The 1572 supernova

File:Main tycho remnant full.jpg
The Calar Alto Observatory imaged Tycho's Supernova Remnant more than four centuries after its discovery

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.[clarification needed] Moreover he also found the object did not even 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[17] 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."[18] 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.

Tycho's observatories

Watercolor plan of Uraniborg

Tycho published the 1572 observations made from his first observatory at Herrevad Abbey in 1574. He then started lecturing on astronomy, but gave 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 had decided to relocate to Basel, but King Frederick II, King of Denmark and Norway, fearful of losing such a scientist, offered Tycho the island of Hven in Oresund with funding to set up an observatory. Tycho first built Uraniborg in 1576 (with a laboratory for his alchemical experiments in its cellar) and then Stjerneborg in 1581.[7] Unusual for the time, Tycho established the Uraniborg as a research centre where almost 100 students and artisans had worked from 1576 to 1597.[19][20]

When King Frederick II died in 1588 he was buried at Roskilde Cathedral, like other Danish monarchs, and his 11 year old son Christian IV, became the new king. Tycho's influence steadily declined and after several unpleasant disagreements, including neglecting to maintain the chapel where Christian's father was buried,[7] he left Hven in 1597 and moved to Prague in 1599. Sponsored by Rudolf II, the Holy Roman Emperor, he built a new observatory in a castle in Benátky nad Jizerou, 50 km from Prague, and he worked there for one year. The emperor then had him move back to Prague, where he stayed until his death. Besides the emperor himself, he was also financially supported by several nobles, including Oldrich Desiderius Pruskowsky von Pruskow, to whom he dedicated his famous volume, the "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 providing astrological interpretations of significant astronomical events such as the comet of 1577 and the supernova of 1572.[21]

Tycho's observational astronomy

Mural quadrant (Tycho Brahe 1598)

Tycho's observations of stellar and planetary positions were noteworthy both for their accuracy and quantity.[22] 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 far less accurate than that. Only for the brighter stars in his final catalog did Tycho achieve a mean error of less than 1'. For dimmer stars, the mean error was closer to 3'.[23] Maximum errors in the star charts were plagued by difficulties such as errors in transcription due to the scribes in Brahe's employ. His planetary positions had a maximum error at least in excess of 3', and even the mean error of his 1577 comet orbital positions was as much as 4', suggesting a possibly much greater maximum error.[24] Nevertheless historians of science typically assert his celestial positions were much more accurate than those of any predecessor or contemporary. For example, Swerdlow (1996, p. 209) claims "The increase in precision Tycho achieved was extraordinary." 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'!"

After his death, his records of the motion of the planet Mars provided evidence to support Kepler's discovery of the ellipse and area laws of planetary motion.[25] Kepler's application of these two laws to obtain astronomical tables of unprecedented accuracy (the Rudolphine Tables)[26] provided powerful support for his heliocentric model of the solar system.[27]

Tycho himself was not a Copernican, but proposed a 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 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.

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.[28]

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's geo-heliocentric astronomy

In this depiction of the Tychonic system, the objects on blue orbits (the moon and the sun) revolve around the earth. The objects on orange orbits (Mercury, Venus, Mars, Jupiter, and Saturn) revolve around the sun. Around all is sphere of fixed stars.

Kepler tried, but was unable, to persuade Tycho to adopt the heliocentric model of the solar system. Tycho believed in geocentrism because he held the Earth was just too sluggish to be continually in motion and 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. This parallax does exist, but is so small it was not detected until the 1830s, when Friedrich Bessel discovered a stellar parallax of 0.314 arcseconds of the star 61 Cygni in 1838.[29] Tycho advocated an alternative to the Ptolemaic geocentric system, a geo-heliocentric system now known as the Tychonic system. In such a system, originally proposed by Heraclides in the 4th century BC, the Sun annually circles a central Earth (regarded as essentially different from the planets), while the five planets orbit the Sun.[30][clarification needed] In Tycho's model the Earth does not rotate daily, as Heraclides 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, Roslin[clarification needed] and Origanus,[clarification needed] was that the orbits of Mars and the Sun intersected.[31] 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.[32] 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.[33] 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.

Tychonic astronomy after Tycho

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 then 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.[34] 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.[35] 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.

Johannes Kepler published the Rudolphine Tables containing a star catalog and planetary tables using Tycho's measurements. Hven island appears west uppermost on the base.

The ardent anti-heliocentric French astronomer Jean-Baptiste Morin devised a Tychonic planetary model with elliptical orbits published in 1650 in a Tychonic simplified version of the Rudolphine Tables.[36] The tenacious longevity of the Tychonic model into the late 17th century and even the early 18th century was attested by Ignace Pardies who declared in 1691 that it was still the commonly accepted system and by Francesco Blanchinus who said it was still such in 1728.[37]

Indeed in possible support of this latter claim, it is especially notable that even the 1726 third edition of Newton's Principia was studiously no more than Tychonic geo-heliocentric in its declared six established astronomical phenomena in the preliminary 'Phenomena' section of Book 3, from which it sought to demonstrate its theory of universal mutual gravitational attraction. For example, Phenomenon 3 stated "The orbits of the five primary planets – Mercury, Venus, Mars, Jupiter and Saturn – encircle the sun.", thus notably excluding the Earth from primary planethood in agreement with Tycho's model.[38] But in fact even Newton's empirical reasoning for going beyond the extent of the partial degree of heliocentrism of the Capellan model to the Tychonic with Mars, Jupiter and Saturn also orbiting the Sun was strikingly invalid:

"Because Mars also shows a full face when near conjunction with the sun, and appears gibbous in the quadratures, it is certain that Mars goes around the sun. The same is proved also with respect to Jupiter and Saturn from their phases being always full;..."[39]

But of course these phenomena of these three outer planets are equally well explained by the Ptolemaic geocentric model.

It seems it was James Bradley's 1729 publication of his discovery of stellar aberration, three years after the Principia's third edition and two after Newton's death, that finally put paid to all forms of geocentrism. For this annual oscillation of stars was only satisfactorily explicable by the conjunction of the heliocentric hypothesis that the Earth annually orbited the Sun with that of the finite speed of light. The discovery of this novel phenomenon thus completed the heliocentric revolution with the complete conversion from all geo-heliocentrism to pure heliocentrism thereafter as now empirically established fact.

Tycho's lunar theory

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.[40]

Legacy

Although Tycho's planetary model became discredited, his astronomical observations are considered an essential contribution to the Scientific Revolution. A traditional view of Tycho, originating in the 1654 biography Tychonis Brahe, equitis Dani, astronomorum coryphaei, vita by Pierre Gassendi and furthered by the 1890 biography by Johann Dreyer, which for a long time was considered the most essential work on Tycho, is that Tycho was primarily an empiricist, who set new standards for precise and objective measurements.[41] According to historian of science Helge Kragh, the origin of this view is Gassendi's opposition to Aristotelianism and Cartesianism and it fails to account for the diversity of Tycho's activities.[41]

Tycho considered astrology a subject of great importance,[42] and he was in his own time also famous for his contributions to medicine and his herbal medicines were in use as late as the 1900s.[43] Although the research community Tycho created in Uraniborg did not survive him, while it existed it fulfilled the roles of being both a research center and an important center of education, functioning as a graduate school for Danish as well as foreign students of both astronomy and medicine.[43] Tycho manoeuvred confidently within the political world and his success as a scientist relied on his political skills to ensure funding for his work.

The crater Tycho on the Moon is named after him, as is the crater Tycho Brahe on Mars.

He was mentioned also on Warehouse 13 on SyFy, showing what was supposed to be one of his prosthetic noses.

See also

Template:Wikipedia-Books

Notes

  1. ^ E. Atlee Jackson (2001). Exploring Nature's Dynamics. Wiley-IEEE. ISBN 9780471191469.
  2. ^ Alena Šolcová: From Tycho Brahe to incorrect Tycho de Brahe..., Acta Universitatis Carolinae, Mathematica et Physica 46, Supplementum, Carolinum, Prague 2005, p. 29–36.
  3. ^ Dansk biografisk Lexikon / II. Bind. Beccau - Brandis (Danish)
  4. ^ Godfred Hartmann (1989), Urania. Om mennesket Tyge Brahe (Urania. About Tyge Brahe, the Man)., Copenhagen: Gyldendal, ISBN 87-00-62763-1
  5. ^ Dansk Biografisk Lexikon (Danish Biographical Lexicon). Copenhagen. Gyldendalske Boghandels Forlag, 1887–1905.
  6. ^ Stephen Hawking (2004). The Illustrated On the Shoulders of Giants: The Great Works of Physics and Astronomy. Running Press. p. 108. ISBN 0762418982. 'I confess that when Tycho died,' Kepler wrote later, 'I quickly took advantage of the absence, or lack of circumspection, of the heirs, by taking the observations under my care, or perhaps usurping them.' {{cite book}}: Unknown parameter |loction= ignored (help)
  7. ^ a b c d e f g J J O'Connor and E F Robertson. Tycho Brahe biography. April 2003. Retrieved 2008-09-28
  8. ^ a b c d e f Fredric Ihren. "Tycho Brahe's Nose And The Story Of His Pet moose". www.nada.kth.se. Retrieved 2008-10-13. from a translation from Gassendi
  9. ^ Cecil Adams. Did astronomer Tycho Brahe really have a silver nose?. 1998-07-17. Retrieved 2008-10-06
  10. ^ Henderson, Mark (2008-12-04). "Tycho Brahe's beloved pet was a drunken moose". Times of London. Archived from the original on 2009-05-29. Retrieved 2009-05-29.
  11. ^ Ihren, from a translation
  12. ^ J. L. E. Dreyer (1890). Tycho Brahe: A Picture of Scientific Life and Work in the Sixteenth Century. Adam and Charles Black, Edinburgh. unknown ISBN.. Page 210 of online version published 2004 covers the moose.
  13. ^ Thoren (1989, p.468–69)
  14. ^ "Ne frustra vixisse videar!" (Dreyer, 2004, p.309).
  15. ^ Thoren (1989, p.469–70)
  16. ^ "Exhumation in the Church of Our Lady before Týn, ". Praha.eu Portal of Prague, . January 21, 2009. Retrieved October 31, 2009. {{cite web}}: Cite has empty unknown parameters: |trans_title=, |month=, |separator=, and |coauthors= (help)CS1 maint: extra punctuation (link)
  17. ^ De stella Nova Photocopy of the Latin print with a partial translation into Danish: "Om den nye og aldrig siden Verdens begyndelse i nogen tidsalders erindring før observerede stjerne..."
  18. ^ Hallqvist, Christoffer (7 February 2006), Al Aaraaf and West Point, Qrisse's Edgar Allan Poe Pages{{citation}}: CS1 maint: date and year (link)
  19. ^ Christianson 2000, page 247
  20. ^ Mary Lou West. "Physics Today August 2001". Archived from the original on 2005-02-15.
  21. ^ Adam Mosley and the Department of History and Philosophy of Science of the University of Cambridge. Tycho Brahe and Astrology. 1999. Retrieved 2008-10-02
  22. ^ Noel Swerdlow, Astronomy in the Renaissance, pp. 187-230 in Christopher Walker, ed., Astronomy before the Telescope, (London: British Museum Press, 1996), pp. 207-10.
  23. ^ Rawlins 1993
  24. ^ There is considerable conflict and confusion in the history of science literature about what level of accuracy Tycho consistently achieved in his celestial positions, but the following 10 references, including Kepler, all testify to it being less than within 1 arcminute as Tycho reportedly claimed to have actually achieved. (i) Dreyer’s 1890 Tycho Brahe p387 found a max error of 2' 2" in the positions of 9 'standard' stars (in the declination of Alpha Virginis) compared with Bradley’s positions retrodicted from his 1755 positions, and two of those 9 stars in excess of 1' error. (ii)Thoren’s 1989 Tycho Brahe p16 found many errors greater than 1’. Thoren says: "[the accuracy of the 777 star catalogue C] falls below the standards Tycho maintained for his other activities....the catalogue left the best qualified appraiser of it (Tycho's eminent biographer J.L.E. Dreyer) manifestly disappointed. Some 6% of its final 777 positions have errors in one or both co-ordinates that can only have arisen from 'handling' problems of one kind or another. And while the brightest stars were generally placed with the minute-of-arc accuracy Tycho expected to achieve in every aspect of his work, the fainter stars (for which the slits on his sights had to be widened, and the sharpness of their alignment reduced) were considerably less well located." (iii) Hoskin's 1999 p101 concurs with Thoren's finding "Yet although the places of the brightest of the non-reference stars [in the 777 star catalogue] are mostly correct to around the minute of arc that was his standard, the fainter stars are less accurately located, and there are many errors.".(iv) Wesley’s 1978 found max errors in at least the order of some 2' in individual instrument measurements for 8 of 9 fundamental stars, with a 123" error in declination by the Northern Equatorial Armillary for only 5 of 9 fundamental stars in Table 3 p47, and 115.5" declination error for Arietis by the Mural Quadrant in Table 1 p44. He comments: "For the majority of stars that appear in Tycho's final star catalogue the overall accuracy might be much less [than that of the 8 fundamental stars Wesley considers]; for there were fewer measurements taken for them, and in many cases the final positions were reduced from sextant readings of distances from some of the fundamental stars or other common ones. In these cases errors might be compounded through the calculations." [p45]. (v) Swerdlow's 1996 p210 reports Kepler considered Tycho's reduced observations of planets to be accurate only within 2'.(vi) Swerdlow 1996 p209 himself claimed "Various statistical evaluations of his [Tycho's] observations have been made with different results, but it is safe to say that fundamental stars and solar altitudes were measured to considerably less than 1'...". But this summary conclusion of the literature is apparently contradicted by Dreyer's 1890 evaluation, Wesley's 1978 evaluation and Rawlins' 1993 evaluation of the errors in Tycho's 9 'fundamental' reference star positions, which all found errors exceeding 1' in at least a third of them, and a maximum error exceeding 2'. And of course Tycho's solar altitudes had a maximum error of almost 3', as even Swerdlow himself, amongst many others, points out, and Pannekoek's 1961 p213 reported an error of 1.5' in his solar altitude at summer solstice. (vii) Pannekoek's 1961 p212 reports an error of +2' in the Earth's obliquity; p213 says there is an error in the solar altitude at summer solstice of 1.5'; and p215 reports a mean error of 4' in positions of the 1577 comet. (viii) But the greatest max errors are given in Rawlins' 1993. They are in descending order a 238 degrees scribal error in the right ascension of star D723; a 36 degrees scribal error in the right ascension of D811 (p42); a 23 degrees latitude error in all 188 southern stars by virtue of a scribal error (p42 M5), which would alone increase the whole catalogue's mean error by more than 4 degrees; a 20 degrees scribal error in longitude of D429; and a 13.5 degrees error in the latitude of D811. He also reported that (ix) Pledge 1939 "repeats the widely believed contention that Tycho's mean error was 4'.", and that (x) Rybka 1984 found a mean error of some 3' for nonbright stars on the basis of comparing only barely half the stars in star Catalogue D with "the modern FK4 star catalogue" values.
  25. ^ Stephenson (1987, pp. 22, 39, 51, 22, 204).
  26. ^ According to Gingerich (1989, p.77) and Linton 92004, p.224) these tables were some 30 times more accurate than other astronomical tables then available.
  27. ^ Swerdlow (2004, p.96), Stephenson (1987, 67–68)
  28. ^ Thoren 1989 Tycho Brahe p14-15 T & W 1989
  29. ^ J J O'Connor and E F Robertson. Bessel biography. University of St Andrews. Retrieved 2008-09-28
  30. ^ See the three articles by Thoren, Jarell and Schofield in Wilson & Taton 'Planetary astronomy from the Renaissance to the rise of astrophysics' 1989 CUP for details
  31. ^ Ibid
  32. ^ See p178-80 of Dreyer's 1890 'Tycho Brahe'
  33. ^ See p171 The Wittich Connection Gingerich and Westman 1988
  34. ^ Taton & Wilson 1989
  35. ^ See p345-56 of Stillman Drake's 1967 Dialogue concerning the two chief world systems. But see Drake's Sunspots, Sizzi and Scheiner' in his 1970 Galileo Studies for its critical discussion of Galileo's misleading presentation of this phenomenon.
  36. ^ See pp.42, 50 & 166 of Taton & Wilson's 1989 The General History of Astronomy 2A.
  37. ^ See p41 of Christine Schofield's article The Tychonic and Semi-Tychonic World Systems in Taton & Wilson (eds) 1989 'The General History of Astronomy Volume 2A'
  38. ^ This interesting fact was apparently first pointed out in the 20th century by the philosopher of science Imre Lakatos in his Newton's effect on scientific standards posthumously published in his 1978 Philosophical Papers Volume 1. In addition to the many logical reasons that have been adduced by such as Duhem, Popper, Feyerabend, Lakatos and others, such as Leibniz and Roger Cotes, to show that Newton did not validly deduce his law of gravity from Kepler's three laws of planetary orbits, this fact also further scuppers the inductivist-positivist claim that he did, since Kepler's laws were heliocentric. Of course in the General Scholium added to its 1713 second edition Newton did endorse heliocentrism in stating "The six primary planets revolve about the sun in circles concentric with the sun..." (p940 Cohen & Whitman Principia) But the Principia never gave any proof that the Earth orbited the sun, not even an invalid one such as were his Phenomenon 3 proofs that Mars, Jupiter and Saturn did.
  39. ^ p799 Principia Cohen & Whitman 1999
  40. ^ V E Thoren, "Tycho and Kepler on the Lunar theory", Publications of the Astronomical Society of the Pacific, vol.79 (1967), pp. 482-489.
  41. ^ a b Kragh, pp. 220–22
  42. ^ See e.g. Kragh, pp. 234–41.
  43. ^ a b Kragh, p. 243.

References

Opera omnia

Further reading

  • John Robert Christianson (2000). On Tycho's Island: Tycho Brahe and his assistants, 1570–1601. Cambridge University Press. ISBN 0-521-65081-X.
  • John Robert Christianson (2002). On Tycho's Island: Tycho Brahe, science, and culture in the sixteenth century. Cambridge University Press. ISBN 0-521-00884-0.
  • Kitty Ferguson: The nobleman and his housedog: Tycho Brahe and Johannes Kepler: the strange partnership that revolutionised science. London: Review, 2002 ISBN 0-7472-7022-8 (published in the US as: Tycho & Kepler: the unlikely partnership that forever changed our understanding of the heavens. New York: Walker, 2002 ISBN 0-8027-1390-4)
  • Joshua Gilder and Anne-Lee Gilder Heavenly intrigue. New York: Doubleday, 2004 ISBN 0-385-50844-1
  • Arthur Koestler: The Sleepwalkers: A History of Man's Changing Vision of the Universe. Hutchinson, 1959; reprinted in Arkana, 1989
  • Godfred Hartmann: Urania. Om mennesket Tyge Brahe. Copenhagen: Gyldendal, 1989 ISBN 87-00-62763-1
  • Wilson & Taton Planetary astronomy from the Renaissance to the rise of astrophysics 1989 CUP (articles by Thoren, Jarell and Schofield on the nature and history of the Tychonic astronomical model)
  • Wesley, Walter G. (1978). "The Accuracy of Tycho Brahe's Instruments" (PDF). Journal for the History of Astronomy. 9: 42–53. Bibcode:1978JHA.....9...42W. Retrieved 2009-09-24. (analysis of individual instrument accuracies)
  • Rawlins, Dennis (1993). "Tycho's 1004-­Star Catalog / The First Critical Edition" (PDF). 3. The International Journal of Scientific History. ISSN 1041-5440. Retrieved 2009-09-24. {{cite journal}}: Cite journal requires |journal= (help); Unknown parameter |month= ignored (help); soft hyphen character in |title= at position 14 (help) (critical analysis of Tycho's 1004 star catalogue D. Printing date: 2009\1\12)
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