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 Sextant
astronomers there in the art of observing. After a falling
out with King Christian IV, Tycho packed up his instruments
and books in 1597 and left Denmark. After traveling several
years, he settled in Prague in 1599 as the Imperial
Mathematician at the court of Emperor Rudolph II. He died
there in 1601. His instruments were stored and eventually
lost.
Tycho's major works include De Nova et Nullius Aevi Memoria
Prius Visa Stella ("On the New and Never Previously Seen
Star) (Copenhagen, 1573); De Mundi Aetherei Recentioribus
Phaenomenis ("Concerning
Mural Quadrant
the New Phenomena in the Ethereal World) (Uraniburg, 1588);
Astronomiae Instauratae Mechanica ("Instruments for the
Restored Astronomy") (Wandsbeck, 1598; English tr.
Copenhagen, 1946); Astronomiae Instauratae Progymnasmata
("Introductory Exercises Toward a Restored Astronomy")
(Prague 1602). His observations were not published during
his lifetime. Johannes Kepler used them but they remained
the property of his heirs. Several copies in manuscript
circulated in Europe for many years, and a very faulty
version was printed in 1666. At Prague, Tycho hired Johannes
Kepler as an assistant to calculate planetary orbits from
his observations. Kepler published the Tabulae Rudolphina in
1627. Because of Tycho's
accurate observations and Kepler's
elliptical astronomy, these tables were much more accurate
than any previous tables.
Tycho Brahe
Tycho Brahe's contributions to astronomy were enormous. He
not only designed and built instruments, he also calibrated
them and checked their accuracy periodically. He thus
revolutionized astronomical instrumentation. He also changed
observational practice profoundly. Whereas earlier
astronomers had been content to observe the positions of
planets and the Moon at certain important points of their
orbits (e.g., opposition, quadrature, station), Tycho and
his cast of assistants observed these bodies throughout
their orbits. As a result, a number of orbital anomalies
never before noticed were made explicit by Tycho. Without
these complete series of observations of unprecedented
accuracy, Kepler could not have discovered that planets move
in elliptical orbits. Tycho was also the first astronomer to
make corrections for atmospheric refraction. In general,
whereas previous astronomers made observations accurate to
perhaps 15 arc minutes, those of Tycho were accurate to
perhaps 2 arc minutes, and it has been shown that his best
observations were accurate to about half an arc minute.
Tycho's observations of the new star of 1572 and comet of
1577, and his publications on these phenomena, were
instrumental in establishing the fact that these bodies were
above the Moon and that therefore the
heavens were not
immutable as Aristotle had argued and philosophers still
believed. The heavens were changeable and therefore the
Aristotelian division between the heavenly and earthly
regions came under attack (see, for instance, Galileo's
Dialogue) and was eventually dropped. Further, if comets
were in the heavens, they moved through the heavens. Up to
now it had been believed that planets were carried on
material spheres (spherical shells) that fit tightly around
each other. Tycho's observations showed that this
arrangement was impossible because comets moved through
these spheres. Celestial spheres faded out of existence
between 1575 and 1625.
Tychonic
Universe If Tycho destroyed the dichotomy between the corrupt and
ever changing sublunary world and the perfect and immutable
heavens, then the new universe was clearly more hospitable
for the heliocentric planetary arrangement propoNicholas 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
More abstracts about the De mundi aetherei recentioribus phaenomenis