A Fascinating Demonstration of Schlieren Optics, Which Visualize Otherwise Invisible Gasses

Harvard Natural Sciences Lecture Demonstrations has created a video demonstrating Schlieren Optics, a process that makes it possible to view small changes in air refraction, making visible gasses that are otherwise unseen by the naked eye. The video demonstrates the effect with hot air from a candle as well as gasses such as helium.

via DIYPhotography