Schlieren flow visualizations illuminate a world of activity that we almost never pay attention to, even when we’re causing it to happen. Simple things like breathing, sneezing, clapping hands, or just producing heat from our normal human body temperature can be seen with this surprising technique.

We’ve watched Schlieren videos of matches being struck and lit before, yet the hidden complexities within fluid dynamics can make these experiments feel fresh with each new example. From The New York Times:

Schlieren imaging requires a light beam in which the rays are all parallel to each other. Deflected in the right way, the light reveals differences in the density of the gases in the flame…

If the patterns in the flame seem incredibly complex, that’s because they are. The mixing of the gases is an example of turbulence, which the Nobel Prize winner Richard P. Feynman called “the most important unsolved problem of classical physics.”

To better understand how these visualizations are made, watch this next: Skunkbear’s What Does Sound Look Like?

Also in the archives: more fluid dynamics, more Schlieren imaging, and more videos from NYT’s Science Take.

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