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Happy 450th birthday to Johannes Kepler

Happy 450th birthday to astronomer Johannes Kepler (Württemberg, Holy Roman Empire 1571)!

Kepler tracked the orbital path of Mars and published his three famous laws of planetary motion — which validated Copernicus’s theory of a sun-centered solar system — and later helped Isaac Newton discover the law of gravity. Kepler was nearly blinded from a smallpox epidemic when he was three, and he developed the first eyeglass designs for nearsightedness and farsightedness. He was also the first to explain that the tides are caused by the moon, the first to propose that the sun rotates on an axis, and the first to use planetary cycles to calculate the year of the birth of Jesus.

People nowadays focus on Kepler's scientific work, but if you look at his bio, you'll see that he bounced all over central Europe because he was on the outs with both the Lutherans and the Catholics -- he went to school in Tubingen and worked as a math teacher in Graz, but fighting during the Thirty Years War pushed him to Prague and Linz and eventually to Regensburg, where he was buried and within a couple of years after his death in 1630 his gravesite was demolished.

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Kepler spent years, using the precise astronomical observations of Tycho Brahe, trying to put the observational positions of the planets in circular orbits, without success. It was only when he realized (his 1st law) that the orbits of the planets were ellipses, with the sun at one focus, that the observational data made sense.

It's his fault (his 2nd law) that the length of the solar day on earth varies throughout the year, based on the distance of the earth from the sun, that "high noon", when sun is at the highest point during the day, only occurs at 12 o'clock a few time a year, and that the sun comes up later some days in January even though the days are getting longer (at the sunset end).

After making these brilliant deductions, he spent the rest of his life trying to establish that you could inscribe and circumscribe the orbits of the planet in series of polygons (triangle, square, pentagon, etc) with increasing number of sides as you progressed away from the sun (how could you do that if the orbits are ellipses?).