Schlieren Optical Technique Incredibly Shows The Flow Of Heat And Gas

Using Schlieren flow visualization, Harvard Natural Sciences Lecture Demonstrations can show small changes in the air that would usually go unseen by the naked eye. By pointing a light at a concave mirror and focusing the light onto the edge of a razor blade in front of a camera, the heat of a candle or helium from a balloon can be seen. Incredible!

NPR covered this technique back in April.