Seeing the invisible
This is what the world would look like if you could see invisible air currents, temperature gradients, and differences in pressure or composition of the air.
Schlieren imaging is a method to visualize density variations in transparent media. The term “schlieren imaging” is commonly used as a synonym for schlieren photography, generally in water or tissue-mimicking media. The method provides a two-dimensional (2D) projection image of the acoustic beam in real-time (“live video”).
Some researchers say that schlieren imaging is equivalent to an X-ray radiograph of the acoustic field. [Via: wikipedia]