Mach number which was also unit-first, and may have influenced the use of the term Mach. In the decade preceding faster-than-sound human flight, aeronautical engineers referred to the speed of sound as "Mach's number", never "Mach 1". Mach number is useful because the fluid behaves in a similar manner at a given Mach number, regardless of other variables. As modeled in the International Standard Atmosphere, dry air at mean sea level, standard temperature of , the speed of sound is . The speed of sound is not a constant; in a gas, it increases as the absolute temperature increases, and since atmospheric
Mach 1: A Story of Planet Ionus Mach 1: A Story of Planet Ionus Mach 1: A Story of Planet Ionus is a 1957 science fiction novel by Allen A. Adler. A paperback version was published in 1966 by Paperback Library with the alternate title Terror on Planet Ionus. While testing an experimental warship, the "Mach 1", a human pilot and his companion are kidnapped into space by aliens from the planet Ionus, which turns out to be a moon of Saturn. There, they confront an oversized monster named Karkong who is menacing the Ionians. Karkong follows them back to Earth. Chaos ensues. Damon Knight wrote of