Biography
Johannes Kepler was a professor of mathematics at the University of Graz, court mathematician to Emperor Rudolf II, and court astrologer to General Wallenstein. Early in his career, Kepler was an assistant of Brahe's. Kepler's career coincided with that of Galilei.
Some events of Kepler's life
Like previous
astronomers, Johannes
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. After
spending twenty years
doing calculations with
Tycho Brahe's data,
Kepler concluded that
this model of planetary
motion was inconsistent
with the data of Tycho
Brahe. Using Tycho's
data, Kepler was able to
formulate Kepler's Laws
of planetary motion in
which planets move in
ellipses and not
circles.
Johannes Kepler discovered the
three 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 polyedra inside
spheres. 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 The Cosmic Mystery . Here is a selection explaining the relation between the planets and the platonic solids:
On October 17, 1604, Johannes 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, provided further evidence that the cosmos was not changeless; this was to influence Galileo's argument. It has since been determined that the star was a supernova, the second in a generation, called Kepler's Star. No further supernovae have since been observed with certainty in the Milky Way, though others outside our galaxy have been seen.
In his 1619 book, Harmonice Mundi, as well as the treatise Misterium Cosmographicum, he also made an association between the Platonic solids with the classical conception of the elements: The tetrahedron was the form of fire, the octahedron was that of air, the cube was earth, the icosahedron was water, and the dodecahedron was the cosmos as a whole or ether. There is some evidence this association was of ancient origin, as Plato relates one Timaeus of Locri who thought of the Universe as being enveloped by a gigantic dodecahedron while the other four solids represent the "elements" of fire, air, earth, and water.
To his disappointment, Johannes Kepler's attempts to fix the orbits of the planets within a set of polyhedrons never worked out, but there were other rewards. Since he was the first to recognize the non-convex regular solids (such as the stellated dodecahedrons), they are named Kepler solids in his honor.
Johannes Kepler's most significant achievements came from the realisation that the orbits of the planets were ellipses, not circles. This realisation was a direct consequence of his failed attempt to fit the planetary orbits within polyhedra. Kepler's willingness to abandon his most cherished theory in the face of precise observational evidence indicates that he had a very modern attitude to scientific research. Kepler also made great steps in trying to describe the motion of the planets by appealing to a force which resembled magnetism, and which emanated from the sun. Although he did not discover gravity, he seems to have attempted to describe the first empirical example of a universal law, to explain the behaviour of both earthly and heavenly bodies.
Johannes Kepler also made fundamental investigations into combinatorics, geometrical optimization, and natural phenomena such as snowflakes, always with an emphasis on form and design. He was also notable for defining antiprisms.
Only two years after his death (1632) his grave was demolished by the Swedish army in the Thirty Years' War.
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