“Critical Factor,” Hal Clement, 1953 – Sentient creatures live beneath the soil. To them, our air is outer space.
Comments: Geology sf and classic of hard sf. Read in Star Science Fiction Stories No. 2.
Author: Wikipedia: “Harry Clement Stubbs (May 30, 1922 – October 29, 2003) better known by the pen name Hal Clement, was an American science fiction writer and a leader of the hard science fiction subgenre. He went to Harvard, graduating with a B.S. in astronomy in 1943. While there he published his first story, “Proof”, in the June 1942 issue of Astounding Science Fiction. His further educational background includes an M.Ed. (Boston University 1946) and M.S. in chemistry (Simmons College 1963).”