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Speed-of-light results under scrutiny at Cern | |
(about 2 hours later) | |
By Jason Palmer Science and technology reporter, BBC News | By Jason Palmer Science and technology reporter, BBC News |
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 href="http://arxiv.org/abs/1109.4897" >presented its work so other scientists can determine if the approach contains any mistakes. | |
If it does not, one of the pillars of modern science will come tumbling down. | |
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 the limit. | Thousands of experiments have been undertaken to measure it ever more precisely, and no result has ever spotted a particle breaking the limit. |
"We tried to find all possible explanations for this," the report's author Antonio Ereditato of href="http://operaweb.lngs.infn.it" >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 scrutinise 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 experiment elsewhere. | |
"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 experiments." | |
Neutrinos come in a number of types, and have recently been seen to switch spontaneously from one type to another. | Neutrinos come in a number of types, and have recently been seen to switch spontaneously from one type to another. |
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 neutrinos. | |
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. | |
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. | 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. | 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". | 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". |