Seeing a Sonic Boom
Image Credit: NASA
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.