Planetary Orbits #2: Tycho Brahe
Refer to my blog
on the planetary models of the old days. This blog, again based on Kitty
Ferguson’s Tycho
and Kepler, focuses on the first half of the Tycho-Kepler pair, a
Danish nobleman cum astronomer par excellence:
“Tycho Brahe was renowned throughout Europe
as a prince among astronomers and an astronomer among princes.”
Tycho believed
that “the future of astronomy lay in numerous and exact observations”. To that
purpose, he designed sophisticated instruments, many of which required “highly
skilled, specialist instrument makers”.
In 1572, he saw a
new object in the sky, brighter than any other star or planet:
-
He
determined that it wasn’t a comet.
-
He
figured it lay beyond the Moon, a
contradiction to Aristotle’s point that nothing changed in the regions beyond
the Moon.
He published all
this in a book, De Stella Nova,
meaning The New Star. An ironic title given that what he’d observed was the death of a star, not its birth: he’d seen a Type I supernova.
(This was confirmed in the late 20th century by detecting the radio
emission from the location identified by Tycho, providing yet another instance
of the meticulous details Tycho had maintained).
King Frederick of
Denmark agreed to pay for a suitable residence for Tycho, the astronomer. Thus
he came to the isle of Hven, where he designed his castle cum observatory cum
boarding house for his assistants!
“The triangular panels of the cone-shaped
observatory could be removed individually to allow Tycho and his assistants to
study one part of the sky or the other.”
Yet another
demonstration of Tycho’s analytical powers were with a comet:
-
He
proved that it lay beyond the Moon.
-
He
proved that it orbited the Sun.
-
He
found that the comet’s speed varied as it went around the Sun, defying yet
another ancient assumption that celestial motion must be uniform.
For all his
observations, Tycho kept meticulous records to show “which instrument he used
for each observation”. He would even have two sets of assistants procure data
from different parts of his observatory, making sure they couldn’t see each
others’ readings, thereby reducing errors in his data! Such meticulousness was
why his data was such a treasure for future analysts.
When it came to
Ptolemy v/s Copernicus, Tycho couldn’t decide:
“The only way to prove that Earth was not
standing still was to find stellar parallax, and that Tycho could not do. There
was simply no physical evidence to show that Copernicus was right.”
It just seemed
like a matter of preference to Tycho. But as can be seen, his conclusion wasn’t
based on dogma: it was based on the (lack of) evidence. Instead, Tycho proposed
a 3rd option for the planetary system, calling it the Tychonic
system:
-
All
the planets orbit the Sun.
-
The
Sun and the Moon orbit the Earth.
He was now looking
for someone who could analyze the data and confirm that his system was right.
That analyst would eventually be Johann Kepler.
But the
Brahe-Kepler partnership was clouded by what one of Brahe’s earlier assistants
had done. That assistant, one Nicolaus Reimers Bär, stole Tycho’s readings and
published them under a different identity, Ursus. Not knowing any of this,
Kepler, who had published his own book, used hyperbole to praise Ursus’ work.
Ursus then used Kepler’s praise to consolidate his claim, something that
brought Kepler to Tycho’s attention. But Tycho wasn’t sure if Kepler might be
genuinely ignorant of the whole Bär/Ursus plagiarism…
Impressed by
Kepler’s book, Tycho wanted him as an assistant. He also tried to get Kepler to
retract against Ursus, but Kepler resented being used as a pawn. Even when
Kepler worked for Brahe, the latter had a nagging fear that Kepler was Ursus’
spy. So he wouldn’t share all his data with Kepler, much to Kepler’s annoyance.
And Kepler wanted all the data to get the big picture; his inquisitiveness
would only raise Brahe’s suspicions. All this led to what the author called a
“dysfunctional collaboration” between the two men.
This
need-you-but-don’t-trust-you setup led to periodic flare-ups, and multiple
instances when Kepler almost left. Finally, when he felt his end was near:
“Tycho at last made the leap of faith and
wagered his earthly immortality on Kepler.”
Thus, upon Tycho’s
death, “the legacy was Kepler’s” to analyze. What conclusions would Kepler draw
from all that data?
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