Tycho
Brahe
(1546-1601)
The first
great optical observer. His primary contributions to astrophysics were
the design and development of observing instruments and the precise
data he collected on the motions of the celestial bodies. His data were
accurate to within roughly 1 to 2 arc minutes. Before his time, the
accuracy was on the order of 15 arc minutes. (Comment--A simple thing
which Tycho did which greatly improved his accuracy was to make several
measurments of quantities and to then average his results in order to
arrive at his final answer. This is standard practice today, but was
highly unusual during Tycho's time.) Further, in contrast to earlier
observers, Tycho observed objects throughout their cycles rather only
at particular times, such as opposition and quadrature.
The data were
complete and accurate enough to allow people to rule out theories of
the motions of the celestial bodies. The result of his (and other people's)
studies was to show that neither the Ptolemaic nor the Copernican models
were acceptable. Both models were not consistent with the data!!!
This was the
first step toward the development of an understanding of the Solar System.
Tycho Brahe
(December 14, 1546 Knudstrup, Denmark – October 24, 1601 Prague,
Bohemia (now Czech Republic)) was a Danish nobleman, well known as an
astronomer/astrologer (the two were not yet distinct) and alchemist.
He had Uraniborg built, which became an early "research institute".
For purposes of publication, he owned a printing press and paper mill.
His best known assistant was Johannes Kepler.
He is universally
referred to as "Tycho" rather than by his surname "Brahe".
Apparently his contemporaries did so and the usage has persisted.
Tycho Brahe
was born Tyge Brahe, adopting the Latinised form Tycho at around age
fifteen (sometimes written Tÿcho). He was born at his family's
ancestral seat of Knudstrup Castle, Denmark to Otte Brahe and Beate
Bille. His twin brother was stillborn (Tycho wrote a Latin ode (Wittendorf
1994, p. 68) to his dead twin which was printed as his first publication
in 1572). He also had two sisters, one older (Kirstine Brahe) and one
younger (Sophie Brahe). Otte Brahe, Tycho's father, a nobleman, was
an important figure in the Danish King's court. Beate Bille, Tycho's
mother, also came from an important family which had produced leading
churchmen and politicians.
Tycho later
wrote that when he was around two, his uncle, Danish nobleman Jørgen
Brahe, ... without the knowledge of my parents took me away with him
while I was in my earliest youth. Apparently this did not lead to any
disputes nor did his parents attempt to get him back. Tycho lived with
his childless uncle and aunt, Jørgen Brahe and Inger Oxe, in
the Tostrup Castle until he was six years old. Around 1552 his uncle
was given the command of Vordingborg Castle to which they moved, and
where Tycho began a Latin education until he was 12 years old.
On April
19, 1559 Tycho began his studies at the University of Copenhagen. There,
following the wishes of his uncle, he studied law but also studied a
variety of other subjects and became interested in astronomy. It was,
however, the eclipse which occurred on August 21, 1560, particularly
the fact that it had been predicted, that 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 such as Sacrobosco's Tractatus de
Sphaera, Apianus' Cosmographia seu descriptio totius orbis and Regiomontanus'
De triangulis omnimodis.
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. -Tycho Brahe, 1563 (age 17).
Tycho realized
that progress in the science of astronomy could be achieved not by occasional
haphazard observations, but only by systematic and rigorous observation,
night after night, and by using instruments of the highest accuracy
obtainable. He was able to improve and enlarge the existing instruments,
and construct entirely new ones. Tycho's naked eye measurements of planetary
parallax were accurate to the arcminute. (These measurements became
the possessions of Kepler following Tycho's death.)
While a student,
Tycho lost part of his nose in a duel with broadswords with Manderup
Parsbjerg, a fellow Danish nobleman. This occurred in the Christmas
season of 1566, after a fair amount of drinking, while the just turned
20-year-old Tycho was studying at the University of Rostock in Germany.
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. A consequence of this was that Tycho developed an interest
in medicine and alchemy. For the rest of his life, he was said to have
worn a replacement made of silver and gold. Tycho's tomb was reopened
in 1901 and his remains were examined by medical experts. The nasal
opening of the skull was rimmed with green, a sign of exposure to copper,
not silver or gold.
His foster
father, uncle Jorgen Brahe, had already died in 1565 of pneumonia after
rescuing Frederick II of Denmark from drowning. In April 1567 Tycho
returned home from his travels, where his father wanted him to take
up law, but was allowed to make trips to Rostock, then on to Augsburg,
where he built a great quadrant, Basel, and Freiburg. He was informed
about his father's illness at the end of 1570, so he returned to Knudstrup,
where his father died in May 1571. Soon after, his other uncle Steen
Bille helped him build an observatory and alchemical laboratory at Herrevad
Abbey.
In 1572 in
Knudstrup Tycho fell in love with Kirsten Jørgensdatter who was
a commoner, her father, Pastor Jorgen Hansen, being the Lutheran clergyman
of Knudstrup's village church. Under Danish law, when a nobleman and
a commoner 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 landed property. (Skautrup 1941, pp. 24-5)
Kirsten Jørgensdatter
gave birth to their daughter, Kirstine (named after Tycho's late sister
who died at 13) on October 12, 1573.
On November
11, 1572, Tycho observed (from Herrevad Abbey) a very bright star which
unexpectedly appeared in the constellation Cassiopeia. Since it had
been maintained since antiquity that the world of the fixed stars was
eternal and unchangeable (a fundamental axiom of the Aristotelian world
view, celestial immutability), other observers held that the phenomenon
was something in the Earth's atmosphere. Tycho, however, observed that
the parallax of the object did not change from night to night, suggesting
that the object was far away. Tycho argued that a nearby object should
appear to shift its position with respect to the background. He published
a small book, De Stella Nova (1573), thereby coining the term nova for
a "new" star. (We now know that Tycho's star was a supernova.)
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 Stella
Nova: "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".
Kepler tried,
but was unable, to persuade Brahe to adopt the heliocentric model of
the solar system. Tycho believed in a modified geocentric model known
as the Tychonian system, for the same reasons that he argued that the
supernova of 1572 was not near the Earth. He argued that if the Earth
were in motion, then nearby stars should appear to shift their positions
with respect to background stars. In fact, this effect of parallax does
exist; it could not be observed with the naked eye, or even with the
telescopes of the next two hundred years, because even the nearest stars
are much more distant than most astronomers of the time believed possible.
King Frederick
II of Denmark and Norway, impressed with Tycho's 1572 observations,
financed the construction of two observatories for Tycho on the island
of Hven in Copenhagen Sound. These were Uraniborg and Stjerneborg. Uraniborg
also had a laboratory for Brahe's alchemical experiments.
Because Tycho
disagreed with Christian IV, the new king of his country, he 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 away
from Prague) and worked there until his death.
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 comet of 1577 and the supernova of 1572.
Tycho was
the preeminent observational astronomer of the pre-telescopic period,
and his observations of stellar and planetary positions achieved unparalleled
accuracy for their time. For example Brahe measured Earth's axial tilt
as 23 degrees and 31.5 minutes, which he claimed to be more acurate
than Copernicus by 3.5 minutes. After his death, his records of the
motion of the planet Mars enabled Kepler to discover the laws of planetary
motion, which provided powerful support for the Copernican heliocentric
theory of the solar system.
Tycho himself
was not a Copernican, but proposed a system in which the planets other
than Earth orbited the Sun while the Sun orbited the Earth. 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.
He was aware
that a star observed near the horizon appears with a greater altitude
than the real one, due to atmospheric refraction, and he worked out
tables for the correction of this source of error.
To perform
the huge number of products needed to produce much of his astronomical
data, Brahe relied heavily on the then-new technique of prosthaphaeresis,
an algorithm for approximating products based on trigonometric identities
that predated logarithms.
Like the
fifteenth century astronomer Regiomontanus, Tycho Brahe appears to have
accepted astrological prognostications on the principle that the heavenly
bodies undoubtedly influenced (yet did not determine) terrestrial events,
but expressed skepticism about the multiplicity of interpretative schemes,
and increasingly preferred to work on establishing a sound mathematical
astronomy. Two early tracts, one entitled Against Astrologers for Astrology,
and one on a new method of dividing the sky into astrological houses,
were never published and are unfortunately now lost.
Tycho also
worked in the area of weather prediction, produced astrological interpretations
of the supernova of 1572 and the comet of 1577, and furnished his patrons
Frederick II and Rudolph II with nativities and other predictions (thereby
strengthening the ties between patron and client by demonstrating value.)
An astrological worldview was fundamental to Tycho's entire philosophy
of nature. His interest in alchemy, particularly the medical alchemy
associated with Paracelsus, was almost as long-standing as his study
of astrology and astronomy simultaneously, and Uraniborg was constructed
as both observatory and laboratory.
In an introductory
oration to the course of lectures he gave in Copenhagen in 1574, Tycho
defended astrology on the grounds of correspondences between the heavenly
bodies, terrestrial substances (metals, stones etc.), and bodily organs.
He was later to emphasise the importance of studying alchemy and astrology
together with a pair of emblems bearing the mottoes: Despiciendo suspicio
- "By looking down I see upward" and Suspiciendo despicio
- "By looking up I see downward." As several scholars have
now argued, Tycho's commitment to a relationship between macrocosm and
microcosm even played a role in his rejection of Copernicanism and his
construction of a third world-system.
Tycho often
held large social gatherings in his castle, as he was a member of the
nobility. He was said to own 1% of the entire wealth of Denmark at one
point in the 1580s. Pierre Gassendi wrote that Tycho also had a tame
elk, and that his mentor the Landgraf Wilhelm of Hesse-Kassel asked
about an animal faster than a deer. Tycho replied writing there were
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/moose just died on a visit to entertain a nobleman at Landskrona.
Apparently during dinner the elk had drunk a lot of beer and fell down
the stairs, and died.
Brahe died
in 1601, several days after straining his bladder during a banquet.
It has been said that to leave the banquet before it concluded, would
be the height of bad manners and so he remained. His weakened state
allowed an infection to invade his body and lead ultimately to his death.
However,
recent investigations have suggested that Tycho did not die from urinary
problems but most likely from mercury poisoning: toxic levels of it
have been found in his hair and hair-roots. Tycho may have poisoned
himself unintentionally by imbibing some mercury-containing medicine.3
Some have even speculated that Tycho may have been murdered, though
there is no solid evidence for this.
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 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.
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.
Tycho Brahe
was given the name Tyge by his parents Beate Bille and Otte Brahe. He
is now known as "Tycho" since that is the Latinised version
of his name that he adopted when he was about fifteen years old. For
simplicity we shall use the name Tycho throughout this biography. Otte
Brahe, Tycho's father, was from the Danish nobility and was an important
man among the Danish King's closest group of supporters. Beate Bille,
Tycho's mother, also came from an important family which had produced
leading churchmen and politicians. Tycho was one of twin sons, but his
twin died shortly after birth. His parents had one older daughter but
Tycho was their eldest son.
A strange
episode occurred when Tycho was two years old. His uncle, Jorgen Brahe
(in Tycho's own words, see for example [5]):- ... without the knowledge
of my parents took me away with him while I was in my earliest youth.
It was a strange
episode since it did not appear to cause any family disputes nor did
his parents try to take him back. Jorgen Brahe and his wife Inger Oxe
had no children of their own, and they acted as foster parents to Tycho
until Jorgen's death. Jorgen Brahe, like his brother Otte Brahe, was
a leading Danish noble while Inger Oxe was the sister of Peder Oxe who
was a member of the Rigsraads, the governing council consisting of 20
advisors to the King. In fact Tycho benefited most on the educational
side from his foster mother Inger Oxe who had scholarly interests as
did other members of her family, while the Brahes and the Billes had
little time for scholarly pursuits.
Jorgen Brahe
commanded Tostrup Castle, and it was in that castle that Tycho lived
from the time he was taken by Jorgen until he was six years old. We
should not give the impression that he did not travel during this time,
for his parents had many administrative duties which took them away
and it is likely that Tycho sometimes went with one of them. In 1552
Jorgen was given the command of Vordingborg Castle, which was a promotion
to a more important role. About a year after Tycho moved to Vordingborg
with his foster parents he began to attend school, almost certainly
attending that attached to the local cathedral. Although Tycho's father
Otte considered learning Latin a waste of time, his foster parents were
much keener that he should receive this type of education. Tycho attended
this school until he was twelve years old, then began his university
studies.
On 19 April
1559 Tycho began his studies at the University of Copenhagen. There,
following the wishes of his uncle, he studied law but also studied a
variety of other subjects and became interested in astronomy. It was,
however, the eclipse which occurred on 21 August 1560, particularly
the fact that it had been predicted, that 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 such as Sacrobosco's Tractatus de
Sphaera, Apianus' Cosmographia seu descriptio totius orbis and Regiomontanus'
De triangulis omnimodis.
His foster
parents decided that he should gain experience abroad and in February
1562 he set off with a travelling companion to go to the University
of Leipzig. Astronomy was not officially part of his studies, these
were classical languages and culture, but he had bought his astronomy
books with him together with Dürer's constellation maps. He began
making observations and by August 1563, while still at the University
of Leipzig, he began to keep a record of these observations. The second
observation he recorded was a conjunction of Jupiter and Saturn which
proved significant for Tycho's subsequent career. Neither tables based
on Copernicus nor on Ptolemy gave the correct date for the conjunction,
Ptolemy's being out by nearly a month and even Copernicus' being out
by days. Tycho, with the confidence of someone not yet seventeen, thought
he could do better - and he later proved himself to be right!
Tycho now
studied astronomy with Bartholomew Schultz at Leipzig who taught him
some tricks to obtain more accurate observations. He knew that accurate
observations required good instruments and he began to acquire them.
Tycho returned home in May 1565 and in the following month his uncle
Jorgen gave his life in rescuing the King. His father, who now commanded
Helsingborg Castle, and mother assumed responsibility for the young
man who was still under eighteen. In 1566 he was off on his travels
again, visiting first the university in Wittenberg and then that in
Rostock. While in Rostock he was involved in an argument with another
Danish student and in the resulting duel Tycho had part of his nose
cut off. A consequence of this was that Tycho developed an interest
in medicine and alchemy.
After his
return home in April 1567 he had an artificial nose made from silver
and gold. He was, however, disfigured for life and his portraits show
the disfigurement which was almost certainly worse than what the artists
portrayed. Tycho's father was keen that he should quickly take up a
political career but somehow Tycho persuaded his father to let him make
another trip abroad. He first revisited Rostock, then went to Basel,
Freiburg, and Augsburg. Tycho had been working on improved instruments
for observing for a while, but when in Augsburg he designed some of
his own and managed to obtain a patron to underwrite the cost of a major
new instrument. In about a month he had a huge quadrant constructed
and erected in the estate of his patron outside the city. It was very
accurate but was so massive that it required many servants to align
it so only one observation could be made each night. Peter Ramus was
also on a visit to Germany and while in Augsburg he learnt of Tycho's
great quadrant leading to meetings at which the two engaged in deep
astronomical discussions. Tycho began constructing another instrument,
this time a large celestial globe made from wood.
Receiving
word that his father was ill, Tycho returned home during the last few
days of 1570. His father died in May 1571 and soon after, with the help
of his uncle Steen Bille, Tycho began constructing an observatory in
Herrevad Abbey. They also built an alchemy laboratory there since alchemy
was becoming a major interest for Tycho. In 1572 he met Kirsten Jorgensdatter,
a girl from his home town of Knudstrup, but since she was a commoner
and he was a noble, they could not marry legally. Kirsten lived with
him, however, as his common law wife. The year 1572 was significant
for Tycho in another way as described by Field [15]:-
On 11 November
1572, he emerged into the dark of the early evening, after a long stint
of alchemical experimentation, and his first glance at the sky showed
him an extra star in the constellation of Cassiopeia, almost directly
overhead. He instantly summoned his chemical assistant to confirm that
the star really was there. He was not the first to see the new star
(a supernova) but his observations of it (published in 1574) did much
to prove beyond reasonable doubt that the star really belonged to the
firmament and was not merely a local phenomenon in the sublunary world
(as comets were generally believed to be). The star is now usually known
as 'Tycho's supernova'. It turned Tycho's interest back to astronomy.
Beginning
in September 1574 Tycho lectured on astronomy at the University of Copenhagen
but gave up in the following spring when he received an annual income
from his father's estate. He set off on another trip abroad, first visiting
Kassel. The Landgraf Wilhelm IV of Hessen-Kassel had founded an observatory
at Kassel about 15 years earlier and Tycho was very impressed by the
methods used there. The design of his own observatory would be influenced
by that at Kassel and Tycho corresponded frequently with the Landgraf;
see [21] for more details of their relationship and correspondence.
Leaving Kassel,
Tycho visited Frankfurt, Basel and finally Venice before returning to
Denmark by the end of 1575. By this time he had made a decision to leave
Denmark and to settle in Basel, but King Frederick of Denmark was not
going to lose his most eminent scientist easily so he made offers to
Tycho to entice him to set up an observatory in Denmark. After some
offers which Tycho did not find attractive, the King offered Tycho the
island of Hven (called today Ven) [15]:-
With financial
help from the King of Denmark, he went on to set up a purpose-built
observatory, on the island of Hven in Copenhagen Sound. The observatory,
called Uraniborg, was equipped with exceptionally large and accurate
instruments (and with an alchemical laboratory in its basement). At
Uraniborg Tycho made twenty years' worth of astronomical observations.
Here is Tycho's
drawing of the main building at Uraniborg, taken from his Astronomiae
instauratae mechanica (1598). Here is his plan of the gardens, from
the same work, with the main building in the centre and servants' quarters,
a printing studio, and other buildings just inside the outer walls.
We should note that Tycho's design was influenced by buildings he had
seen in Venice, and was also constructed in a highly geometrical form.
One of the
most exciting astronomical events which Tycho observed from Uraniborg
was a comet which he first spotted on 13 November 1577. He published
his account in De mundi aetherei recentioribus phaenomenis (1588) where
he draws cosmological conclusions from the fact that his measurements
show that the comet is not closer to Earth than the Moon, contradicting
Aristotle's model of the cosmos. From his observations Tycho was able
to show that the comet was certainly further away than Venus.
In 1584, with
the observatory of Uraniborg now too small to house all his instruments,
Tycho built a second one named Stjerneborg adjacent to Uraniborg. This
was the time when Tycho was most active in producing major new instruments.
Thoren writes [32]:-
Because of
the number and variety of instruments made and described by Tycho, previous
commentators have assumed that he made instruments for the sheer sake
of keeping his instrument-makers busy. In fact, however, their construction
can be traced in his logs and rationalized as several series of experiments
which only produced his major instruments in the mid-1580's. The ten-year
process had considerable consequences for progress of Tycho's theoretical
work during his life. It has also obscured historical understanding
of the accuracy of his instruments.
Tycho's marvellous
agreement between the description and practice of observations.
Wesley, in
[38] and [39], makes a careful study of the accuracy of Tycho's observations.
Swerdlow, reviewing 38] writes:-
The results of the study are interesting, and speak well for the accuracy
of Tycho's instruments. Those tested are the mural quadrant, revolving
wooden quadrant, revolving steel quadrant, astronomical sextant, and
equatorial armillary, the last measuring declinations directly. Aside
from occasional periods when one or another instrument was distinctly
out of adjustment - as, by the way, only a study of this kind can show
- the observations have errors falling mostly between about 0.5' and
1.0', that is, about the accuracy of the standard used for comparison.
Thus, as was also the case in the earlier study of fixed stars, Kepler's
belief that Tycho's observations could be trusted to better than two
minutes is amply confirmed.
Among his
many discoveries Tycho found that the obliquity of the ecliptic had
decreased since the time of Ptolemy but, as explained in [24], he obtained
an incorrect value due to errors by Ptolemy.
Tycho is perhaps
best known today for his theory of the solar system which is based on
a stationary Earth round which the Moon and Sun revolve. The other planets,
according to Tycho's theory, revolve round the Sun. In fact in his younger
days Tycho had been convinced by Copernicus' Sun centred model but his
firm belief that theory must be supported by experimental evidence led
him away. The problem was, of course, that in the Sun centred model
of Copernicus a parallax shift should be observed but despite his attempts
to measure such a shift, Tycho could detect none. There were two possibilities
to explain this: either the Earth was fixed, or the scale of the universe
was unbelievably large. We know today that it is the second of these
which is true, and that the scale is such that Tycho would have had
no hope in measuring parallax with his instruments. The first measurement
of the parallax of a star was in 1838 by Bessel who found 0.3"
for the parallax of 61 Cygni. Despite the quality of Tycho's measurements,
this value in about 100 times smaller that Tycho's observational errors.
In fact Tycho was not the first to propose the Earth centred model with
the planets rotating round the Sun for Erasmus Reinhold had done so
a few years earlier. However Rosen in [26] argues convincingly that
Tycho did not know of Reinhold's theory.
King Frederick
died in April 1588 and, his son Christian (who became King Christian
IV) still being a child, a regent was appointed. Support for Tycho continued
however, and he presented a scheme to the Rigsraads to allow his children
to inherit Uraniborg. Six of his eight children had lived. He had two
sons; Tycho, born in 1581, and Georg in 1583. He also had four daughters;
Kirsten born in 1573, Magdalene in 1574, Elizabeth in 1579, and Cecilie
in 1582. Because Kirsten was Tycho's common law wife, their children
could not inherit. Tycho, however, presented a patent which gave Uraniborg
something like university status, and the director something like the
status of the head of a university. It also stated that succession to
the headship would give preference to "Tycho Brahe's own".
Perhaps surprisingly, since the state was attempting to stop the acceptance
of common law wives, Tycho's patent was accepted, a sure sign of the
high esteem in which he was held (and perhaps also due to many family
and friends being on the Rigsraads).
In his younger
days Tycho had been a fair man in his dealings with others. Although
he had treated the inhabitants of Hven badly by modern standards, and
also in their eyes, it was usual for a lord at this time to treat his
subjects harshly. However in the 1590s Tycho's nature seemed to change
and his treatment both of the inhabitants of Hven and of his student
helpers at Uraniborg became unreasonable. He always thought a lot of
himself and perhaps by this stage his view of his own importance (he
saw himself as the natural successor to Hipparchus and Ptolemy, a far
more important person than a King) had rather turned his head. Negotiations
over the marriage of his daughter Magdalene to Gellius, who had been
an assistant at Uraniborg for five years, fell apart and caused Tycho
extreme grief and family upset. He fell out with the young King Christian
by not repairing the Chapel of the Magi at Roskilde, where Christian's
father Frederick was buried, despite it being on an estate which provided
Tycho with a substantial income. Christian made it clear that the promise
Tycho had been given that Uraniborg would continue under the direction
of his children no longer held.
Tycho closed
down his observatory on Hven in 1597 (the last recorded observation
is on 15 March that year), and moved to Copenhagen. However, things
did not go well for him there and he left Denmark with his family and
his instruments to seek support and find somewhere to continue his work
[15]:-
In 1599 he
was appointed Imperial Mathematician to the Holy Roman Emperor, Rudolph
II, in Prague (then the capital of the Holy Roman Empire). Johannes
Kepler joined him as an assistant, to help with mathematical calculations.
Tycho intended that this work should prove the truth of his cosmological
model, in which the Earth (with the Moon in orbit around it) was at
rest in the centre of the Universe and the Sun went round the Earth
(all other planets being in orbit about the Sun and thus carried round
with it).
Tycho began
observing again in Prague. He received support from Rudolph for Kepler
and himself to compile a new set of astronomical tables based on Tycho's
recorded observations over 38 years. These would be called the Rudolphine
Tables as a tribute to their sponsor. However, Tycho died eleven days
after dining at the palace of Peter Vok Ursinus Rozmberk as a result
of adhering to the etiquette of the day and refusing to leave the dinner
table before his host. Kepler describes his death (see for example [5]):-
Holding his
urine longer than was his habit, Brahe remained seated. Although he
drank a little overgenerously and experienced pressure on his bladder,
he felt less concerned for his state of health than for etiquette. By
the time he returned home he could not urinate any more. Finally, with
the most excruciating pain, he barely passed some urine, but yet it
was blocked. Uninterrupted insomnia followed; intestinal fever; and
little by little delirium. ... During his last night, through the delirium
in which everything was very pleasant, like a composer creating a song,
Brahe these words over and over again: "Let me not seem to have
lived in vain."
Field writes
[15]:-
When Tycho died, Kepler succeeded him as Imperial Mathematician. Tycho's
observations of planetary positions, which were made using instruments
with open sights (a telescope was not used for astronomy until about
1609), were much more accurate than any made by his predecessors. They
allowed Kepler, who (unlike Tycho) was a convinced follower of Copernicus,
to deduce his three laws of planetary motion (1609, 1619) and to construct
astronomical tables, the Rudolphine Tables (Ulm, 1627), whose enduring
accuracy did much to persuade astronomers of the correctness of the
Copernican theory. However, until at least the mid-seventeenth century,
Tycho's model of the planetary system was that favoured by most astronomers.
It had the advantage of avoiding the problems introduced by ascribing
motion to the Earth.