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 (kernel) team had built Mach and ported it to a number of platforms, including complex multiprocessor systems which were causing serious problems for older-style kernels. This generated considerable interest in the commercial market, where a number of companies were in the midst of considering changing hardware platforms. If the existing system could be ported to run on Mach, it would seem it would then be easy to change the platform underneath. Mach received a major boost in visibility when the Open Software Foundation (OSF) announced they would be hosting future versions of OSF/1 on Mach 2.5, and were investigating Mach 3