Download Revolutionary Times: Copernicus and Tycho Brahe

Theme 3 Part 2 – Revolutionary
Times: Copernicus and Tycho Brahe
ASTR 101
Prof. Dave Hanes
Revolutionary Times
A Few Aspects to Note
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The invention of the printing press provided the ability
to promulgate new ideas freely
These were times of great artistic and literary creativity
The Protestant Reformation (Martin Luther) questioned
the ultimate authority of the then-dominant religious
order in Europe
The European discovery of the New World marked the
dawn of an age of adventurous exploration
The Principal Astronomical Players
Copernicus – the idea (early 1500s)
Tycho Brahe – the observations (late 1500s)
Kepler – the analysis and empirical laws (1620s)
Galileo – the proof (early 1600s)
Newton- the physics (late 1600s)
Copernicus: Proposed a
Heliocentric Solar System
Not himself a keen observer
of the heavens!
Motivated mainly by a wish
for simplification; he disliked
the contrived Ptolemaic model.
He hesitated to publish for fear of persecution.
De Revolutionibus Orbium Coelestium
(On the Revolutions of the Heavenly Spheres)
Tycho Brahe
An unusual life, from youth to death:
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Lost his nose in a duel, had a fake one
made
Apparently a very cantankerous man.
Died of a burst bladder after a banquet
He was inspired by and wrote about
a‘nova’ – a ‘new’ star – appearing where
none had been seen before. (It is now
recognized to have been a ‘supernova,’ an
exploding star at its death.)
Mapping the Pattern of Stars
First, a definition:
the meridian runs across
the sky from North to South,
through the zenith (your
overhead point). It divides
the Eastern half of the sky
from the Western half.
Think of the meaning of AM and PM: ‘ante’ (before) and
‘post’ (after) meridiem
The Behaviour of Stars
Measuring the Stars:
a Meridian Transit
Build a big instrument
like that shown, oriented
exactly North-South.
No need for a telescope!
A straight stick or narrow
hollow tube will do. It has
to be free to swing up and
down.
Measure Two Coordinates
1. Raise or lower the movable stick to point it at each star
in turn as it passes through the meridian. Differences in
this ‘up-down’ sense tells you which stars are farther North
or South in the sky.
2. Use a clock. If Star A passes through the meridian
before Star B, then Star A is to the West of Star B (by a
measurable amount, given by the difference in time).
(The third coordinate, the star’s distance from us, is
unknown!)
Now Accumulate Some Data!
1. Repeat this exercise many, many times to get a
precise, detailed map of the sky as defined by the
fixed stars. (The stellar patterns don’t change
perceptibly over human lifetimes.)
2. Make similar measurements, night after night,
to see how the moving dots of light (the planets)
change position over time.
Tycho at
work
A Model of his Home at
Uraniborg, in Denmark
(he was very generously
supported by the ruler)
One Particular Contribution
Tycho observed a comet, and invited others in various farflung locations to describe what they had seen.
From the lack of measurable parallax, he proved that the
comet was farther away than the moon – not an
atmospheric effect, as some had maintained.
The comet had to be moving through the realm of the
planets, metaphorically shattering Ptolemy’s ‘crystalline
spheres.’
Tycho’s Most Important Contributions
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He accumulated lots and lots of data (really a first in
any scientific endeavour) arising from
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precise repeated measurements, using
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the very best instruments possible, built to exacting
standards [but still no telescopes]; and
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he hired Kepler to analyze the data!
Tycho’s Legacy
Tycho believed in a hybrid model, with a static
Earth, with the moon and sun orbiting us, but all
the other planets orbiting the sun
(This would explain why we see
no stellar parallax.)
His dying wish (to Kepler)
was that he might be
proven right.
http://www.youtube.com/watch?v=3cutaPj7qMY&feature=related
The Shakespearean Connection
Tycho’s coat of arms bears
the names of two important
ancestors: Rosenkrantz and
Guildenstern (left side)
Characters with these names
appear in Hamlet, and indeed
Shakespeare’s plays have
various subtle allusions to the
questions raised by the
“Copernican revolution”