Big Bang machine could
destroy Earth
by Jonathan Leake
Science Editor
A NUCLEAR accelerator designed to replicate the Big
Bang is under investigation by international physicists
because of fears that it might cause "perturbations of the
universe" that could destroy the Earth. One theory even
suggests that it could create a black hole.
Brookhaven National Laboratories (BNL), one of the
American government's foremost research bodies, has
spent eight years building its Relativistic Heavy Ion Collider
(RHIC) on Long Island in New York state. A successful
test-firing was held on Friday and the first nuclear collisions
will take place in the autumn, building up to full power
around the time of the millennium.
Last week, however, John Marburger, Brookhaven's
director, set up a committee of physicists to investigate
whether the project could go disastrously wrong. It
followed warnings by other physicists that there was a tiny
but real risk that the machine, the most powerful of its kind
in the world, had the power to create "strangelets" - a new
type of matter made up of sub-atomic particles called
"strange quarks".
The committee is to examine the possibility that, once
formed, strangelets might start an uncontrollable chain
reaction that could convert anything they touched into more
strange matter. The committee will also consider an
alternative, although less likely, possibility that the colliding
particles could achieve such a high density that they would
form a mini black hole. In space, black holes are believed
to generate intense gravitational fields that suck in all
surrounding matter. The creation of one on Earth could be
disastrous.
Professor Bob Jaffe, director of the Centre for Theoretical
Physics at the Massachusetts Institute of Technology, who
is on the committee, said he believed the risk was tiny but
could not be ruled out. "There have been fears that strange
matter could alter the structure of anything nearby. The risk
is exceedingly small but the probability of something
unusual happening is not zero."
Construction of the £350m RHIC machine started eight
years ago and is almost complete. On Friday scientists sent
the first beam of particles around the machine - but without
attempting any collisions.
Inside the collider, atoms of gold will be stripped of their
outer electrons and pumped into one of two 2.4-mile
circular tubes where powerful magnets will accelerate them
to 99.9% of the speed of light.
The ions in the two tubes will travel in opposite directions
to increase the power of the collisions. When they smash
into each other, at one of several intersections between the
tubes, they will generate minuscule fireballs of superdense
matter with temperatures of about a trillion degrees -
10,000 times hotter than the sun. Such conditions are
thought not to have existed - except possibly in the heart of
some dense stars - since the Big Bang that formed the
universe between 12 billion and 15 billion years ago.
Under such conditions atomic nuclei "evaporate" into a
plasma of even smaller particles called quarks and gluons.
Theoretical and experimental evidence predicts that such a
plasma would then emit a shower of other, different
particles as it cooled down.
Among the particles predicted to appear during this cooling
are strange quarks. These have been detected in other
accelerators but always attached to other particles. RHIC,
the most powerful such machine yet built, has the ability to
create solitary strange quarks for the first time since the
universe began.
BNL confirmed that there had been discussion over the
possibility of "perturbations in the universe". Thomas
Ludlam, associate project director of RHIC, said that the
committee would hold its first meeting shortly.
John Nelson, professor of nuclear physics at Birmingham
University who is leading the British scientific team at
RHIC, said the chances of an accident were infinitesimally
small - but Brookhaven had a duty to assess them. "The
big question is whether the planet will disappear in the
twinkling of an eye. It is astonishingly unlikely that there is
any risk - but I could not prove it," he said. |
