(((relevant to recent discussion on extropians@)))
Gambling with the Earth
If physicists create killer strangelets, we're all doomed. Should we
take the risk?
THE probability that dangerous Earth-devouring particles will be born
at a new particle accelerator in the US may be tiny, but scientists
have played down the devastating potential costs in their risk
assessments, a physicist now says.
Adrian Kent of Cambridge University accepts that the chances of
catastrophe are minuscule. But he claims physicists are not accounting
for the scale of the potential devastation--the destruction of the
entire planet--in their risk analysis. "Small catastrophe risks are
more costly than we've generally considered," says Kent.
Last year, sensational newspaper reports suggested that a new particle
accelerator, the Relativistic Heavy Ion Collider (RHIC) at Brookhaven
National Laboratory on Long Island, could put the Earth in peril. The
accelerator might create blobs of matter called strangelets containing
"strange" quarks, as well as the usual "up" and "down" types in
ordinary matter. If a strangelet were stable and negatively charged,
it might begin eating the nuclei of ordinary matter, converting them
into strange matter. Eventually this could consume the entire Earth.
Physicists reassured the public by pointing out that such a chain of
events is nigh-on impossible (New Scientist, 28 August 1999, p
24). The main reason for their confidence is that it's very unlikely
that strangelets would be stable or negatively charged.
Astronomical evidence is also reassuring. Heavy ion collisions occur
naturally, for instance when cosmic rays smash into heavy nuclei on
the Moon. Yet the Moon has existed for 5 billion years without being
devoured by a ravenous strangelet.
Arnon Dar, Alvaro De Rújula and Ulrich Heinz of the CERN particle
physics laboratory near Geneva used the fact that stars are not being
changed into strange matter at a significant rate to calculate the
maximum probability of the Brookhaven collider creating a dangerous
strangelet during the accelerator's lifetime. The result was less
than 20 chances in a billion, which the team called "a safe and
stringent upper bound" (Physics Letters B, vol 470, p 142). Thus
reassured, the Brookhaven lab set RHIC running in June.
But Kent now argues that this probability is far from acceptable when
compared with risk assessments of other possible hazards, which factor
in the scale of the devastation if things go wrong. He points out that
radiological protection policy in Britain deems it unacceptable for
solid nuclear waste to pose more than a one-in-a-million chance of
killing around five people a year on average. To achieve the same
level of risk, global annihilation by a strangelet would have to have
a probability of 1 in 1015 or less, because it has the potential to
wipe out all 6 billion people on the planet.
John Marburger, director of the Brook-haven lab, does not accept this
line of argument. He says that the risk limit calculated by the CERN
researchers was not a safety assessment in the sense used in nuclear
energy safety analysis. "In my opinion, no such risk assessment is
possible," says Marburger. "We do not know how a 'dangerous
strangelet' would be created, and we do not know the properties of one
if it were."
De Rújula agrees. "We've been standing on our heads to try to convince
people it's not true and to come up with limits on it, and this number
comes from very, very pessimistic assumptions." He says it is "absurd"
to take such a minuscule maximum probability and multiply it by the
number of people who would die if a strangelet swallowed the
world. "It's not going to happen," he says.
From New Scientist magazine, 07 October 2000.
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