Hal Clement is the pen name of Harry Clement Stubbs, one of the most exactingly scientific of science-fiction writers. Most of his novels and stories work out in minute detail the physical conditions for life on other worlds, from the astrophysical characteristics of the planet and its system to the chemical composition of its seas and atmosphere and the physiological adaptations of its inhabitants.

Stubbs was born in Somerville, Massachusetts. His interest in science and technically accurate science fiction dates from about 1930, when a Buck Rogers panel referred to a race to Mars, "forty-seven million miles away," and young Hal went to the library to check the reference. He took a B.S. in astronomy at Harvard in 1943, a master's degree in education at Boston University in 1947, and an M.S. in chemistry at Simmons College in 1963. His first published story, "Proof," appeared in Astounding Science-Fiction in June...