1895 – Austria
‘The ratio of the velocity of an object in air to the velocity of sound in air is termed the Mach number’
If the Mach number is 1, speed is called sonic. Below Mach 1 it’s subsonic; above Mach 1 it’s supersonic.
Captain Chuck Yeager was the first person to break the sound barrier, on 14 October 1947. His flight was in the Bell X-1 rocket under an US government research program.
THE JET ENGINE