Though the universe has not changed significantly in the past several centuries, man's knowledge of it has grown enormously. This is the story of four pioneer scientists — Copernicus, Tycho, Kepler, and Galileo — who did the most to enable us to understand the universe as we do today. Author Robert Silverberg brings to life vividly the men and their times. He shows how Newton and the scientists who followed him built on the discoveries of these great pioneers.