In this first volume in the Space Biology and Medicine series, contributors describe the current status of their understanding of space, highlighting physical and ecological conditions as well as heavenly bodies, and provide general information that will prove useful in the later volumes. The book is divided into four parts: Part I, Historical Perspective; Part II, The Space Environment; Part III, Life in the Universe; and Part IV, Space Exploration. Chapter contributions were made by both U.S. and Russian authors. The book also features an appendix of Astronomical and Physical Quantities, a detailed subject index, and an 8-page color section.