Picture of Johan Kepler Courtesy of The Bettman Archive. From engraving by MacKenzie

Johan Kepler was a German astronomer who lived between 1571-1630. Kepler used Tycho Brahe's observations of Mars to show that planetary orbits are not circular, but, in fact, elliptical (or shaped like an egg).

Kepler also found other laws describing the motion of planets, and helped prove that the Copernican model of the universe was correct.