by Jason Palmer
Science and technology reporter
23 September 2011
detectors are needed to catch neutrinos,
that are so elusive
as to be dubbed "ghost particles"
A meeting at CERN, the world's largest
physics lab, has addressed results that suggest subatomic particles
have gone faster than the speed of light.
The team has published its work so other scientists can determine if
the approach contains any mistakes.
If it does not, one of the pillars of modern science may come
Antonio Ereditato added "words of caution" to his CERN presentation
because of the "potentially great impact on physics" of the result.
The speed of light is widely held to be 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.
Thousands of experiments have been undertaken to measure it ever
more precisely, and no result has ever spotted a particle breaking
"We tried to find all possible
explanations for this," the report's author Antonio Ereditato of
the Opera collaboration told BBC News on Thursday evening.
"We wanted to find a mistake - trivial mistakes, more
complicated mistakes, or nasty effects - and we didn't. When you don't find anything, then you say 'well, now I'm
forced to go out and ask the community to scrutinize this'."
Friday's meeting was designed to begin
this process, with hopes that other scientists will find
inconsistencies in the measurements and, hopefully, repeat the
"Despite the large [statistical]
significance of this measurement that you have seen and the
stability of the analysis, since it has a potentially great
impact on physics, this motivates the continuation of our
studies in order to find still-unknown systematic effects," Dr
Ereditato told the meeting.
"We look forward to independent measurement from other
Graphic of the Opera experiment
Neutrinos come in a number of types, and
have recently been seen to switch spontaneously from one type to
The CERN team prepares a beam of just one type,
muon neutrinos, and
sends them through the Earth to an underground laboratory at Gran Sasso in Italy to see how many show up as a different type, tau
In the course of doing the experiments, the researchers noticed that
the particles showed up 60 billionths of a second earlier than they
would have done if they had travelled at the speed of light.
This is a tiny fractional change - just 20 parts in a million - but
one that occurs consistently.
The team measured the travel times of neutrino bunches some 16,000
times, and have reached a level of statistical significance that in
scientific circles would count as a formal discovery.
Professor Antonio Ereditato of CERN:
understatement that these are unexpected results"
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.
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 told BBC News.
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".
Speed of light broken by neutrinos at CERN
September 23, 2011
A fundamental subatomic
particle, the neutrino,
seems to be capable of
travelling faster than the speed of light
(that is, the speed of a photon
through a vacuum).