Look At All This Pretty Sound

From NPR:

When light passes between areas of different air density, it bends. You’ve probably noticed the way distant pavement seems to shimmer on a hot day, or the way stars appear to twinkle… In the mid-nineteenth century, German physicist August Toepler invented a photography technique called Schlieren Flow Visualization to visually capture these changes in density. The setup is a bit hard to explain in words (watch the video above for a full explanation) but it allows scientists and engineers to see things that are normally invisible: the rising heat from a candle, the turbulence around an airplane wing, the plume of a sneeze.

This video shows the sound of a hand clap, a towel snap, an AK-47 firing: it is mesmerizing. [NPR]