- A dictionary of medical eponyms

Mach's number

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In fluid mechanics, the ratio between the speed of an object moving through a fluid to the speed of sound in that fluid. Mach numbers less than one indicate subsonic flow (the sound moves faster than you); Mach numbers greater than one indicate supersonic flow (you are faster than the sound).


  • E. Mach and P. Salcher:
    Photographische Fixirung der durch Projectile in der Luft eingeleiteten Vorgänge.
    (Peter Salcher (Austrian photographer, 1848-1928).
    Sitzungsberichte der Akademi der Wissenschaften in Wien, 1887, 95: 764-780.
    The experiments described in this classic paper were carried out in Fiume with the support of the Royal Austrian Navy. P. Salcher worked at the Marine Academy in Fiume.

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