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Copernicus was wrong and that
Earth did not move. This was
Tycho’s conclusion.
The Tychonic model
In reaching this conclusion, Tycho
trusted his own direct experience.
He did not feel Earth moving. In
fact, nothing that he observed
convinced him that the planet
was moving. Earth appeared to
be stationary and the external
universe was the only thing that
appeared to be in motion. This led
Tycho to discard the Copernican
cosmos and introduce his own. In
his model of the cosmos, all the
planets except Earth orbited the
sun, but the sun and the moon
orbited a stationary Earth.
For many decades after his death
in 1601, Tycho’s model was popular
among astronomers who were
dissatisfied with Ptolemy’s Earth-
centric system but who did not wish
to anger the Catholic Church by
adopting the proscribed Copernican
model. However, Tycho’s own
insistence on observational accuracy
provided the data that would lead
to his idea being discredited
shortly after his death. His accurate
observations helped Johannes Kepler
THE TELESCOPE REVOLUTION
Tycho Brahe Born a nobleman in 1546 in^
Scania (then Denmark, but now
Sweden), Tyge Ottesen Brahe
(Tycho is the Latinized version
of his first name) became an
astronomer after sighting a
predicted solar eclipse in 1560.
In 1575, King Frederick II
gave Tycho the island of Hven
in the Øresund Strait, where he
built an observatory. Tycho later
fell out with Frederick’s successor,
Christian IV, over the potential
transfer of the island to his children
and closed the observatory. In
1599, he was appointed Imperial
Mathematician to EmperorRudolph II in Prague. There,
Tycho appointed Johannes
Kepler as his assistant.
Tycho was famed for his
distinctive metal nose, the
legacy of a duel he fought as
a student. He died in 1601,
allegedly of a burst bladder,
having refused out of politeness
to take a toilet break during
a long royal banquet.Key work1588 Astronomiæ Instauratæ
Progymnasmata (Introduction
to the New Astronomy)to demonstrate that the planets’
orbits are ellipses and to create a
model that would displace both the
Tychonic and Copernican models.
Tycho’s improved measurements
would also allow English astronomer
Edmond Halley to discover the
proper motion of stars (the change
in position due to the stars’ motion
through space) in 1718. Halleyrealized that the bright stars Sirius,
Arcturus, and Aldebaran had, by
Tycho’s time, moved over half a
degree away from the positions
recorded by Hipparchus 1,850 years
earlier. Not only were the stars not
fixed in the sky, but the changing
positions of the closer stars could
also be measured. Stellar parallax
was not detected until 1838. ■The Tychonic model
kept Earth at the center
of the cosmos as in the
Ptolemaic model, but
the five known planets
were now orbiting the
sun. Although he was
impressed by the
Copernican model,
Tycho believed
that Earth did
not move.Outer ring
of starsSunVenus
MercuryMoonEarthJupiterSaturnMars