Posted on 09/26/2001 8:40:32 PM PDT by aculeus
Lab tests have proved that bubbles can sink floating objects. The findings add weight to suggestions that methane bubbles escaping from methane reserves in the seabed might have been to blame for vessels disappearing in the Bermuda Triangle and the North Sea.
The Greek mathematician Archimedes realised that for something to float, the density of the liquid has to be greater than the density of the object. So a simple argument is that if you mix enough bubbles into a liquid to lower its average density, an object floating on its surface should sink. People have suggested that this process is behind the mysterious demise of many ships that sank for no obvious reason.
However, Bruce Denardo at the Naval Postgraduate School in Monterey, California, was sceptical. He points out that rising bubbles often carry currents of water up with them, exerting an upwards force on the floating object. For all but the most violent bubbles, this upward drag might be enough to keep an object afloat.
Bubbling under
Denardo and his colleagues decided to test the theory. They filled a four-litre glass beaker with water, then fed in air at the bottom at varying speeds. Then they dropped in steel balls filled with varying amounts of water and air to see how easily they would sink. If, in the absence of rising bubbles, the ball only just floated on the surface, switching on the bubbles made it sink.
"We were surprised that the theory was confirmed," says Denardo. "This is just what one might naively expect, but we expected that an upward drag would occur."
Even so, the case isn't closed, Denardo says. Because the experiment was carried out in a closed container, he thinks upward currents might not have had room to form. In the open sea, upwellings would form more easily in the region of the bubbles, while the water would flow downwards again a short distance away.
Secret weapon
Initially this would help a boat to stay afloat. But if the vessel were swept slightly to one side, it might just hit the down currents and sink.
Denardo concludes that we can't rule out the methane theory for ships lost in the Bermuda Triangle. "If a phenomenon can be made to occur in a lab, it probably occurs somewhere in the natural universe," he says.
If bubbles can indeed sink ships, the military might want to use them as a weapon. Michael Stumborg, a researcher at the US Naval War College in Rhode Island, has proposed building "buoyancy bombs" that would collect and release bubbles.
An underwater vehicle could extract methane from a deposit in the seabed, then transport it to a point underneath a target ship. "The release of the methane will reduce the buoyancy of the ship and could in principle sink it," says Denardo.
Journal reference: American Journal of Physics (vol 69, p 1064)
Carting a load of air around underwater sounds safer and more environmentally-friendly than a load of methane.
I say it's either the aliens or related to the question "Who is John Gault?"
LOL!!
Watch out for that chili AND beer. That's an explosive combination!
Years ago, some of my colleagues at a military electronics lab were looking in the manual that covers the uniform (JAN) coding system for naming technical materiel. For example, one of the radar displays we were working on was designated the SPA-25, where "SPA" somehow meant "Shipborne Display, Radar."
They noticed that if you had, say, a "BBB-3", it would mean "Underwater Bombing Pigeon, Mark III."
So it would not surprise me if there was already a designation available for "Underwater Farting Cow."
So, did you like the 'cockroach' thread?
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