These are some photographs taken by Gary Settles, an engineering professor at Pennsylvania State University. I came across them in a recent article in the New York Times (you can find the original article here). Unfortunately, the process is very poorly explained in the article, but he seems to be doing something that allows him to create images of disturbances in the air that are otherwise invisible to the eye. Pretty cool stuff. Not exactly art photography, but then again neither was the work of Harold Edgerton (search for him on google images for more great photographs, including the famous bullet-through-an-apple).