Resumo de Mystery Of The Cosmos - Mysterium Cosmographicum

Like previous astronomers, Kepler initially believed that
celestial objects moved in perfect circles. These models
were consistent with observations and with the Platonic
idea that the sphere was the perfect shape. However, after
spending twenty years doing calculations with data
collected by Tycho Brahe, Kepler concluded that the
circular model of planetary motion was inconsistent with
that data. Using Tycho's data, Kepler was able to formulate
three laws of planetary motion, now known as Kepler's laws,
in which planets move in ellipses, not circles. Using that
knowledge, he was the first astronomer to successfully
predict a transit of Venus (for the year 1631).
Kepler
discovered the laws of planetary motion while trying to
achieve the Pythagorean purpose of finding the harmony of
the celestial spheres. In his cosmovision, it was not a
coincidence that the number of perfect polyhedra was one
less than the number of known planets. Having embraced the
Copernican system, he set out to prove that the distances
from the planets to the sun where given by spheres inside
perfect polyhedra, all of which were nested inside each
other. The smallest orbit, that of Mercury, was the
innermost sphere. He thereby identified the five Platonic
solids with the five intervals between the six known
planets - Mercury, Venus, Earth, Mars, Jupiter, Saturn; and
the five classical elements.
In 1596 Kepler published
Mysterium Cosmographicum, or The Cosmic Mystery. Here is a
selection explaining the relation between the planets and
the Platonic solids:
? Before the universe was created,
there were no numbers except the Trinity, which is God
himself? For, the line and the plane imply no numbers: here
infinitude itself reigns. Let us consider, therefore, the
solids. We must first eliminate the irregular solids,
because we are only concerned with orderly creation. There
remain six bodies, the sphere and the five regular
polyhedra. To the sphere corresponds the heaven. On the
other hand, the dynamic world is represented by the flat-
faces solids. Of these there are five: when viewed as
boundaries, however, these five determine six distinct
things: hence the six planets that revolve about the sun.
This is also the reason why there are but six planets?

? I have further shown that the regular solids fall
into two groups: three in one, and two in the other. To the
larger group belongs, first of all, the Cube, then the
Pyramid, and finally the Dodecahedron. To the second group
belongs, first, the Octahedron, and second, the
Icosahedron. That is why the most important portion of the
universe, the Earth?where God's image is reflected in man?
separates the two groups. For, as I have proved next, the
solids of the first group must lie beyond the earth's
orbit, and those of the second group within? Thus I was led
to assign the Cube to Saturn, the Tetrahedron to Jupiter,
the Dodecahedron to Mars, the Icosahedron to Venus, and the
Octahedron to Mercury?
To emphasize his theory, Kepler
envisaged an impressive model of the universe which shows a
cube, inside a sphere, with a tetrahedron inscribed in it;
another sphere inside it with a dodecahedron inscribed; a
sphere with an icosahedron inscribed inside; and finally a
sphere with an octahedron inscribed. Each of these
celestial spheres had a planet embedded within them, and
thus defined the planet's orbit.
On October 17, 1604,
Kepler observed that an exceptionally bright star had
suddenly appeared in the constellation Ophiuchus. (It had
appeared on October 9 previous.) The appearance of the
star, which Kepler described in his book De Stella nova in
pede Serpentarii ('On the New Star in Ophiuchus's Foot'),
provided further evidence that the cosmos was not
changeless; this was to influence Galileo in his argument.
It has since been determined that the star was a supernova,
the in a generation, later called Kepler's Star or
Supernova 1604. No further supernovae have since been
observed with certainty in the Milky Way, though others
outside our galaxy have been seen.

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