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\MARK POST #6259

https://en.wikipedia.org/wiki/Mach_number

…”The Mach number is named after Austrian physicist and philosopher Ernst Mach, a designation proposed by aeronautical engineer Jakob Ackeret. As the Mach number is a dimensionless quantity rather than a unit of measure, with Mach, the number comes after the unit; the second Mach number is “Mach 2” instead of “2 Mach” (or Machs).

This is somewhat reminiscent of the early modern ocean sounding unit “mark” (a synonym for fathom),

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.”[3]”…

https://en.wikipedia.org/wiki/Fathom

X,Y,Z AXIS DEPTH

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