Written in 1965, this popular science book by Paul Ceuzin presents astronautics as a driving force of social, economic, and technical transformation for terrestrial civilization. After a brief historical survey (from Wang-Tou to Sputnik), it reviews satellite applications (telecommunications, meteorology, navigation), civilian spin-offs of space technologies (miniaturized electronics, portable atomic energy, new materials), biological obstacles to long-duration human spaceflight, and the military and legal stakes of the space conquest. Written at the dawn of the Apollo program, the book argues for a calm acceptance of the astronautical revolution and concludes with a plea for international cooperation in space.