Bullwhips, breaking the sound barrier, and science in progress

New year resolution: blog more.

We’ve been big fans of Destin Sandlin ever since his original chicken video (seriously: take a look), and into his Smarter Every Day YouTube channel. His latest film is outstanding.

If you were in central Newcastle just before Christmas you might have seen an Australian street performer doing whip stunts. You’ll certainly have heard him, as the tip of his whip exceeded the speed of sound and produced that characteristic crack sound, which echoed down the street.

If you’ve read or thought about that at all you’ve probably worked out that the tapered shape of the whip means that as the wave of movement reaches the tip, the tip is accelerated violently, reaching the speed of sound and beyond. ‘Why whips crack’ is one of those things that’s felt ‘known’ for quite some time.

Yeah, turns out there’s a bunch of detail missing from those sorts of explanations. And all you need to start to uncover it is a curious YouTuber, a high-speed camera, a world record-holding whip performer (who also happens to be a mechanical engineer and fluid dynamicist), and a bunch of academics willing to come together to do some experiments in a motion capture studio.

This film is great. It captures not just new detail about how a whip exceeds the speed of sound, but also offers a glimpse into how science is done.

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