Certainly one of the greatest scientists who ever lived, Isaac Newton (1642-1727) had a profound impact on astronomy, physics, and mathematics. Among his many achievements were the invention of the reflecting telescopeóthe basic design behind all large telescopes used today; the invention of a branch of mathematics known as calculus, a critical tool throughout science; the elucidation of the three laws of motion; and the development of the law of universal gravitation. Until the coming of general relativity in the 20th century, Newtonís theories were the basis for all cosmological models. When still in his mid-twenties, he was named Lucasian Professor of Mathematics at Cambridge the post now held by Stephen Hawking.