Science_Illustrated_Australia_-_Issue70_2019

scienceillustrated.com.au | 7

When a plane flies faster than the speed of

sound, the pressure waves in front don’t

have time to flow around the aircraft and the air

becomes compressed, eventually producing a shock

wave, its energy discharge yielding the sonic ‘boom’

for which supersonic planes are famous. NASA has

managed to capture this image of two such shock

waves interfering like ripples on a pond, with the

resulting variation of air density causing light to bend

differently and so be observed as different colours.

Compressed air: two sonic

shock waves in collision

Photo // NASA
NA

SA