Dolphin Rings
Things that make you go, hmm!
The attached video is of dolphins playing with silver colored rings
which they have the ability to make under water to play with. 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! It stands upright in the water like a
magic doorway to an unseen dimension. The dolphin then pulls a small
silver donut from the larger one. Looking at the twisting ring for
one last time a bite is taken from it, causing the small ring to collapse
into a thousands of tiny bubbles which head upward towards
the water's surface. After a few moments the dolphin creates another
ring to play with. There also seems to be a separate
mechanism for producing small rings, which a dolphin can accomplish by a
quick flip of its head.
An explanation of how dolphins make these silver rings 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 reasonably
few seconds of play time.
