Hillsborough: Ask the Times

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Ask the Times

By TIMES WIRES
Published July 27, 2007

I have seen the term Mach used as a measure of airspeed for jets, but what scale is it based on and what is its origin?

Named for Ernst Mach, an Austrian physicist born in 1838, the number is based on the ratio of the speed of an object, such as a jet, to the speed of sound in atmospheric gases. That speed depends on the type and temperature of the gases. Mach is a variable number that describes the effect when some of the energy of the aircraft goes into compressing the air surrounding it. Mach 1 is the point at which the speed of an object approaches the speed of sound, or becomes transonic.

[Last modified July 27, 2007, 00:36:04]

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