This is an intelligent, revealing biography, but in a specialized field and not for a popular market. The battle between world revolution and world obscurantism is personified by Nicolaus Copernicus of Poland, who in spite of the disbelief of his contemporaries, miserable instruments, the acceptance of the Ptolemaic system, disproved astrology and made possible modern astronomy. Copernicus is viewed in relation to his century, the concepts of the time. He is traced in his slow, steady development as a man who, though child of his times nevertheless proved to be the great master of the physics of the sky. His early life, universities, Cracow, Italy, his canonship and the comparative case of life as nephew of a famous Bishop his genius for mathematics, philosophy, medicine, his ideas of calendar reform and the origin of his tower where his observations were made and his calculations publicized in De Revolutionibus Orbium Coelestium. The reception of the book and the ideas produced tremendous repercussions; Bruno, Pycho de Brahe, Kepler, Galileo contributed to the Copernican theory, and its influence was felt up to Eddington and Einstein. The focus of the book, however, is on the medieval world and a man who extended the universe.