a speed relative to the speed of sound Mach number is a ratio of the speed of a body (aircraft) to the speed of sound)
Mach is named after Ernst Mach an Austrian philosopher and physicist.
Mach 1 is about 717mph Mach 2 is twice that. The speed of sound varies due to atmospheric conditions and density of the air.
Most commercial airliners fly below Mach 1
#mach#speed of sound. ernst mach#aircraft#sonic#sonic boom