This photo by Dr. Gary Settles was made using the schlieren technique, which involves a lens, a curved mirror, a razor blade and other objects. This technique reveals disturbances in the air. I've ordered the surprisingly expensive book by Settles all about it, and plan to make some of my own, although it will be hard to do better than this candle image. I don't know what it is about these photos, but they have a sweetly dated look. Is it the colors? The clothes? Of course the technique itself is low tech, especially compared to the new kinds of scientific imaging of turbulence you can see nowadays- all digital renderings. To see more schlieren photography and the the New York Times article about it:

http://www.nytimes.com/2008/10/28/science/28cough.html

Photo: Gary Settles/Penn State