Akademik

(or Keppler, 1571–1630)

The founder of modern astronomy, Kepler was born near Stuttgart. It was as an assistant to the Danish astronomer Tycho Brahe (1546–1601) that he began his astronomical career, and from Tycho he derived his respect for minute and accurate observation. He said that it was the slight discrepancy between the actual position of Mars and its predicted position (eight minutes of arc) that pointed the road to a complete reformation of astronomy. Kepler himself harboured many Pythagorean, occult, and mystical beliefs, but his laws of planetary motion are the first mathematical, scientific, laws of astronomy of the modern era. They state (i) that the planets travel in elliptical orbits, with one focus of the ellipse being the sun; (ii) that the radius between sun and planet sweeps equal areas in equal times; and (iii) that the squares of the periods of revolution of any two planets are in the same ratio as the cube of their mean distances from the sun.