Science
Exploring a Mysterious Plasma Effect in a High-Speed Jet of Water

What if I told you that a stream of water hitting a glass surface creates an arc of plasma? Lots of people suspected our favorite mad scientist, Ben Krasnow, might be playing an April Fool’s joke on us when he posted this video last night claiming that blasting a piece of glass with a high-intensity, directed stream of water would actually generate a plasma across the surface of the glass.

But it’s no prank. Ben is riffing off of a paper he discovered on the National Academy of Sciences website explaining the little-known, little understood phenom called “extreme hydrodynamic sheer.”

Ben’s video does an excellent job of explaining what’s happening, but basically, a charge is created as the water, being blasted under high pressure from a hydraulic power ram through a tiny 100 micron tube (at about 240 meters per second), hits the surface of the glass and then jets off along the surface at a 90 degree angle. Where the sudden charge differential occurs, it actually creates a little blue arc of plasma. Cool!

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Gareth Branwyn is a freelance writer and the former Editorial Director of Maker Media. He is the author or editor of over a dozen books on technology, DIY, and geek culture. He is currently a contributor to Boing Boing, Wink Books, and Wink Fun. And he has a new best-of writing collection and “lazy man’s memoir,” called Borg Like Me.

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