Odds are, you've probably never heard of the Schlieren effect (I hadn't until today). In layman's terms, it's simply the ability to see changes in air density, like when you turn on a hair dryer or open a can of soda (we know air is rapidly moving, we just can't see it). That's probably not a very helpful description but you'll see what I mean in the clip above from YouTube user brusspup.

Using a concave mirror, a light source, a razor blade and a camera, brusspup was able to visualize these invisible changes in air density. It almost looks like special effects or camera tricks but the user claims it is 100 percent science so I'll take their word for it. All I know is that it's incredibly impressive and I want to try it for myself.

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