Kepler, Johannes

Austrian Astronomer. Kepler proposed the fundamental simplification of the Copernican scheme by hypothesising one ellipse for the orbit of each planet. This achieved a very good fit, and finally put to rest the Platonic scheme of explaining the motions of the heavens in terms of compounds of uniform circular motion.

Kepler is famous for three laws, firstly, elliptical orbits for planets, secondly the law that a line from the sun to a planet sweeps out equal areas in equal times, and finally that the square of the time a planet takes to complete one orbit is proportional to the cube of its mean distance from the sun. Kepler was the first whole hearted and public advocate of the Copernican system. He is also famous for trying to reproduce the ratios of the orbits of the planets from fitting together the five perfect solids, and the theory that the sun holds the planets in their orbits by magnetism.

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Physics

Contributed by: Richard P Whaite