Sidney Rosen is presently professor emeritus of astronomy at the University of Illinois. He still teaches in a special undergraduate program called Unit 1. His field, however, is not astronomy, but the history of science. When he finished his doctorate at Harvard in 1955 (on the GI Bill), Rosen’s wife, Dorothy, a children’s librarian in the Boston Public Library at the time, persuaded him to write a book about Galileo, and to his surprise, Little, Brown bought it. The book received good reviews and went through sixteen printings. The success of this book sparked similar bios of the great early Renaissance physician Paracelsus, who is considered the “father of chemotherapy”; the astronomer Johannes Kepler, who first worked out the planetary orbits; and R. Buckminster Fuller, designer of the geodesic dome.