dipper@utastro.UUCP (Debbie Byrd) (12/27/85)
Today is the birthday of the man who first described the planets' orbits around the sun. More about Johannes Kepler -- when we come back. December 27: Kepler's Revelation Today is the birthday of Johannes Kepler, who discovered the shapes of the orbits traveled by the planets around the sun. That was a great discovery, especially considering that when Kepler was born in 157l, many people still thought that the sun went around the Earth! Kepler on the other hand believed Copernicus -- who'd said that the planets orbit the sun. He set about to try to find a theory that would describe the orbits of the Earth and the other planets. Kepler concentrated his study on the planet Mars. He spent nearly a decade trying to prove that Mars orbits the sun in a perfect circle. But he didn't succeed -- because the orbit of Mars isn't exactly circular. After long years of labor, Kepler realized that Mars' orbit describes an ellipse, which is a kind of squashed out circle. The difficulty had been that, in the case of Mars and the other known planets, this ellipse is plump and round -- very nearly circular. The observations fit -- and Kepler's theory was simple and elegant. Afterwards, people had to believe that Earth was not in the center of the universe. Script by Deborah Byrd. (c) Copyright 1984, 1985 McDonald Observatory, University of Texas at Austin