BoomerGirl Diary

Tonight, as I recover from not one, but THREE, tornado warnings, fraught with worry for the thousands of people who didn't get out of Galveston in time, a video of dolphins playing with mysterious self-propagating bubbles makes me smile.

Thanks to my friend, Deb, for sending me this mesmerizing footage. Here's what her e-mail said about the phenomenon you're about to see:

The attached video is of dolphins playing with silver colored rings which they have the ability to make under water. It isn't known how they learn this or if it's an inbred ability.

As if by magic the dolphin does a quick flip of its head and a silver ring appears in front of its pointed beak. The ring is a solid, donut shaped bubble about 2-ft across, yet it doesn't rise to the surface of the water!

An explanation is that they are"air-core vortex rings". Invisible, spinning vortices in the water are generated from the tip of a dolphin's dorsal fin when it is moving rapidly and turning. When dolphins break the line, the ends are drawn together into a closed ring. The higher velocity fluid around the core of the vortex is at a lower pressure than the fluid circulating farther away. Air is injected into the rings via bubbles released from the dolphin's blowhole. The energy of the water vortex is enough to keep the bubbles from rising for a few seconds of play time.

As we watch the worst of Mother Nature unfold in the Gulf of Mexico, it's nice to know there are still beautiful things happening somewhere under the sea...or, in an aquarium, anyway.