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Hello. My name is Katherine Brading and I'd like to share with you our recreation of Johannes
Kepler's platonic solids model of the cosmos, which he published in 1596 in his book Mysterium
Cosmographicum. He used this model to explain the spacing of the orbits of the planets in
Copernicus's system.
Here's the Sun, at the center of Copernicus's system, and here is how Kepler describes his
model, in his own words:
"The earth's circle is the measure of all things. Circumscribe a dodecahedron around
it. The circle surrounding it will be Mars."
There it is: the shell that has Mars' orbit inside it.
"Circumscribe a tetrahedron around Mars.
The circle surrounding it will be Jupiter.
Circumscribe a cube around Jupiter.
The surrounding circle will be Saturn.
Now, inscribe an icosahedron inside the earth. The circle inscribed in it will be Venus.
Inscribe an octahedron inside Venus.
The circle inscribed in it will be Mercury." OK, so that's Kepler's model. The spacing
of these shells gives the spacing of Copernicus's orbits In other words, hidden in Copernicus's
orbits is a deep structure, an inner harmony.
This is what Kepler has uncovered and laid before our eyes.
At the time Kepler was writing, most people believed that the Earth is at the center of
the cosmos. Copernicus had published his Sun-centered
system in 1543, and Kepler was living and working at a time when very few people believed
that Copernicus was right. The two astronomical systems -- one geocentric
and the other heliocentric -- were equally good when it came to the match between predictions
and observations, so how do you decide between them?
Kepler offered an answer: We know the heliocentric system is right because this system -- and
not the geocentric system -- has an underlying geometrical harmony.
And because we have found this harmony, we know that we've hit on the right structure
for the cosmos. This recreation of Kepler's model was built
by Matt Meixner at the University of Notre Dame Visualization Theater, which is directed
by Keith Davis.