[Ghost]

"IT SEEMS very rude to come to
someone's party and tell him that he
lost a bet again," said cosmologist Luis
Lehner of the Perimeter Institute in
Ontario, Canada. Lehner did it anyway.
He was speaking at a meeting to
celebrate Stephen Hawking's 70th
birthday. The bet in question was over
whether a point of infinite density and
space-time curvature, known as a
singularity and usually found at the
centre of a black hole, can also exist in
a naked form without its black hole . At
a singularity, all our existing physical
laws go out the window. This doesn't
normally matter because the black hole
that surrounds the singularity is ringed
by a one-way membrane called an
event horizon, which lets light and
information in, but not out. That means
the singularity cannot affect anything
beyond the event horizon.

Near a naked singularity , however,
things would become bewildering as
we would no longer be able to predict
the fate of anything in its line of sight.
"It might not actually do anything nasty,
but we have lost predictive power,"
says Lehner. "I couldn't tell you if this
glass would be sitting on the table
tomorrow."

In 1991, Hawking bet Kip Thorne and
John Preskill of the California Institute
of Technology in Pasadena that all
singularities are clothed. Six years later
he lost, when situations emerged where
naked singularities can exist, although
they are unstable and vanish or retreat
behind an event horizon with the tiniest
perturbation.

Lehner has now proposed another
situation where naked singularities
might exist: in the extra dimensions
proposed by string theory . The rub is
that this time, they aren't unusual.
To understand why, think of black holes
as points in the four dimensions we
experience - three of space and one of
time. These become "black strings"
when extended into a fifth dimension of
space (see diagram).

Black strings are unstable and break up
into smaller black holes like a stream of
water splitting into droplets. Lehner
showed that at the point where a
smaller black hole pinches off from the
stream, the black hole's radius is zero,
which means its density is infinite. In
other words, it is a naked singularity.
Lehner showed this will happen any
time you have a black string.

Thorne, the beneficiary of the bet, was
in the audience and said the study was
"beautiful work". Of course this comes
with a big caveat: we only need to
worry about these naked singularities if
the universe has five dimensions -
something that isn't yet clear. String
theory suggests there are at least five
dimensions, but cosmologists without a
stake in the bet might hope that it is
proved wrong. Otherwise they will have
their work cut out explaining the laws
of physics at a naked singularity.

Source 13/01/12.

http://www.newscientist.com/mobile/a...mg21328474.500

[RedneckR0nin]

Wicked thread Ghost

[MrCorpse]

<iframe width="420" height="315" src="http://www.youtube.com/embed/_ytMq6JNSA8" frameborder="0" allowfullscreen></iframe>