Thanks to schlieren photography, cameras are able to see things our eyes normally miss -- like airwaves splitting around a car in a wind tunnel, for example. The technique works by forcing light through a very small opening to a recording medium, which means that even tiny fluctuations in this light -- such as those caused by the way it's bent by changing air pressure -- are captured. In fact, the word schlieren actually means "regions of a transparent medium, as of a flowing gas, that are visible because their densities are different from that of the bulk of the medium," according to The Free Dictionary.
While all of that's pretty interesting, what's even better is getting to see the principle in action. Here, the technique has been used by Royal Melbourne Institute of Technology (RMIT) lecturer Phred Peterson to show just what happens to the air around a match as it slowly sparks into a flame.
The initial strike looks like a mushroom cloud as sparks spray out to the sides, disturbing the air around them. Then, as the match heats up, you can clearly see the hot air around it begin to rise. As the match comes into flame, it almost looks like the air currents are liquid -- sort of like what you'd see inside a lava lamp.
Of course, this isn't the first time schlieren photography has been used to capture remarkable images. The technique has been around since the early 1800s and a quick search on YouTube will bring up lots of fascinating videos, like this Science Channel segment posted by YouTuber cplai that details the process quite nicely and even shows what looks like a guy blow drying his hair with a flame thrower.
We also showed youback in 2008. But here's a warning: schlieren photos and videos are kind of addictive, so make sure you have some time to dive into the fascinating photographic technique, or your day might just go up in smoke.