2011-09-23 06:20:26
By Jason Palmer Science and technology reporter, BBC News
Puzzling results from Cern, home of the Large Hadron Collider, have confounded
physicists - because it seems subatomic particles have beat the speed of light.
Neutrinos sent through the ground from Cern toward the Gran Sasso laboratory
732km away in Italy seemed to show up a tiny fraction of a second early.
The result - which threatens to upend a century of physics - were put online
for scrutiny by other scientists.
In the meantime, the group says it is being very cautious about its claims.
They will be discussing the result in detail in a conference at Cern on Friday
afternoon, which can be viewed online.
"We tried to find all possible explanations for this," said report author
Antonio Ereditato of the Opera collaboration.
"We wanted to find a mistake - trivial mistakes, more complicated mistakes, or
nasty effects - and we didn't," he told BBC News.
"When you don't find anything, then you say 'Well, now I'm forced to go out and
ask the community to scrutinise this.'"
Caught speeding?
The speed of light is the Universe's ultimate speed limit, and much of modern
physics - as laid out in part by Albert Einstein in his theory of special
relativity - depends on the idea that nothing can exceed it.
Albert Einstein in Pittsburgh on 28 December 1934 Much of modern physics
depends on the idea that nothing can exceed the speed of light
Thousands of experiments have been undertaken to measure it ever more
precisely, and no result has ever spotted a particle breaking the limit.
But Dr Ereditato and his colleagues have been carrying out an experiment for
the last three years that seems to suggest neutrinos have done just that.
Neutrinos come in a number of types, and have recently been seen to switch
spontaneously from one type to another.
The team prepares a beam of just one type, muon neutrinos, sending them from
Cern to an underground laboratory at Gran Sasso in Italy to see how many show
up as a different type, tau neutrinos.
In the course of doing the experiments, the researchers noticed that the
particles showed up 60 billionths of a second sooner than light would over the
same distance - a tiny fractional change, but a consistent one.
The team measured the travel times of neutrino bunches some 15,000 times, and
have reached a level of statistical significance that in scientific circles
would count as a formal discovery.
But the group understands that what are known as "systematic errors" could
easily make an erroneous result look like a breaking of the ultimate speed
limit, and that has motivated them to publish their measurements.
"My dream would be that another, independent experiment finds the same thing -
then I would be relieved," Dr Ereditato said.
But for now, he explained, "we are not claiming things, we want just to be
helped by the community in understanding our crazy result - because it is
crazy".
"And of course the consequences can be very serious."