A History of Short Words

From the New York Times Crossword Puzzle

MACH

Fri, 20 Sep '24
Kind of number represented by the equation M = v/c
Mon, 25 Dec '23
Physicist Ernst
Thu, 22 Jun '23
Name associated with speed
Wed, 29 Mar '23
Ernst who studied sonic booms
Sat, 22 Jan '22
Speed of sound
Fri, 27 Aug '21
It's calculated relative to the speed of sound