Nasa: Kepler and His Laws

This site from NASA provides biographical details about the lives of Tycho Brahe and Johannes Kepler. Discusses Kepler's successes at developing laws of planeatry motion. States the three laws and discusses each one individually. Proivdes details about what an ellipse is and of the elliptical nature of planets' orbits. Provides period-distance data in support of Kepler's thrid law. Well done.