Not Winging It, But Ringing It
Filed by KOSU News in Science.
May 28, 2013
Humans do it with smoke.
Dolphins do it with air.
With a little snort, dolphins can produce a nearly perfect “air” rings, (sophisticated non-dolphins called them toroidal vortices) which they turn into underwater toys.
If they leave the rings alone, (because air is lighter than water) the underwater circles will expand, rise to the surface and disappear — so very playful dolphins don’t let them rise. In the video below, you can see them pushing the rings down, so the water pressure keeps them compact. Or — just for the fun of it, it seems — they will make a ring smaller by cutting it in two — with a quick bite!
So here the dolphin approaches …
… then, (extremely quickly, so fast you can’t see how) it takes a nip out of the bigger bubble, instantly restitching the two loose ends into a smaller, more compact bubble that keeps the bubble tight and lets them keep playing …
Dolphins (I learned watching videos with dolphin expert Diana Reiss and Stanford bubble physicist Manu Prakash) sometimes blow two bubbles, giving the second one an extra push that sends its sailing right through the first — a kind of dolphin parlor trick.
But their favorite thing, it seems, is to use their noses (called rostrums) to spin the bubbles without ever touching them. They intentionally create turbulence in the surrounding water that can make the ring spin very tight, or they’ll design a looser, wigglier bubble, move it along until it’s about to burst, and just before it does, they open their mouths …
… and swallow it!
While humans and dolphins obviously play with rings, it’s possible humpback whales do this too. The video shows humpbacks sending air rings to the ocean surface, but in one of them, the giant underwater author suddenly pops up mid-ring to take what looks like a bow in front of a boat of whale-watchers.
Volcanoes, of course, don’t take bows. But in any ring-blowing contest, Italy’s live volcano, Mt. Etna, deserves some kind of trophy for Gorgeous Ring Production. This nearly perfect ring got coughed straight out of a mountain …
The video ends with a complicated series of rings within rings produced by the Soviet Union in 1961. It is the biggest man-made toroidal vortex in human history, and it’s the only ring in this video collection that made me wince. [Copyright 2013 NPR]