Seeing a Sonic Boom

A shockwave spreads from the tip of a supersonic jet
Variations in air pressure and temperature show up as darker regions, similar to the "heat shimmer" seen above a road on a hot day.
Image Credit:

September 3, 2015

As a Northrop T38 Talon tears through the skies above the Mojave desert at supersonic speeds, it compresses the air in front of it, creating a shockwave at its tip that spreads outward at the speed of sound. This compression changes the air’s index of refraction, allowing it to be visualized through a technique known as Schlieren photography. While Schlieren photography is difficult enough with a stationary object, this picture was even harder to take than usual; it had to be captured from a subsonic aircraft, right as the supersonic jet flew under it. Note the shimmer of the plane’s exhaust, several hundred degrees warmer than the air around it.