Tycho Brahe
Tycho Brahe 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 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. 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. 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 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's major works include De Nova et Nullius
Aevi
Memoria Prius Visa Stella ("On the New and Never Previously Seen
Star)
(Copenhagen, 1573); De Mundi Aetherei Recentioribus
Phaenomenis
("Concerning the New Phenomena in the Ethereal World) (Uraniburg,
1588);
Astronomiae Instauratae Mechanica ("Instruments for the
Restored
Astronomy") (Wandsbeck, 1598; English tr. Copenhagen, 1946);
Astronomiae
Instauratae Progymnasmata ("Introductory Exercises Toward a
Restored
Astronomy") (Prague 1602). His observations were not published
during his
lifetime.