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Location: UFOUpDatesList.Com > 2001 > Sep > Sep 28

Bubbling Seas Can Sink Ships

From: UFO UpDates - Toronto <ufoupdates@home.com>
Date: Fri, 28 Sep 2001 11:42:17 -0400
Fwd Date: Fri, 28 Sep 2001 11:42:17 -0400
Subject: Bubbling Seas Can Sink Ships

http://www.newscientist.com/news/news.jsp?id=ns99991350

Bubbling seas can sink ships

19:00 26 September 01
Johanna Marchant

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)

19:00 26 September 01




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