One of the pillars of physics and Albert Einstein's theory of relativity — that nothing can go faster than the speed of light — was rocked Thursday.
By DENNIS OVERBYE, Seattle TIMES, 9/23/11
Roll over, Einstein? One of the pillars of physics and Albert Einstein's theory of relativity — that nothing can go faster than the speed of light — was rocked Thursday.
European researchers said they clocked an oddball type of subatomic particle called a neutrino going faster than the 186,282 miles per second long been considered the cosmic speed limit.
If true, the result would change the world. But that "if" is enormous.
Even before the European physicists had presented their results — in a paper that appeared on the physics website www.arXiv.org Thursday night and in a seminar at CERN, the European Center for Nuclear Research, to be held Friday — a chorus of physicists had risen up on blogs and elsewhere arguing it was far too soon to give up on Einstein and that there probably was some experimental error.
"These guys have done their level best, but before throwing Einstein on the bonfire, you would like to see an independent experiment," said John Ellis, a CERN theorist who has published work on the speeds of the ghostly particles known as neutrinos. The researchers themselves are not ready to proclaim a discovery and are asking other physicists to independently try to verify their findings. "The feeling that most people have is this can't be right, this can't be real," said James Gillies, a CERN spokesman.
Going faster than light is something that is not supposed to happen according to Einstein's 1905 special theory of relativity, the one made famous by the equation E equals mc squared.
According to scientists familiar with the paper, the neutrinos were fired from a particle accelerator at CERN outside Geneva, where they were created, to a cavern underneath Gran Sasso in Italy, 454 miles away, about 60 nanoseconds faster than it would take a light beam. Scientists calculated the margin of error at 10 nanoseconds, making the difference statistically significant.
Even this small deviation would open up the possibility of time travel and play havoc with longstanding notions of cause and effect. Einstein himself — author of modern physics — said that if you could send a message faster than light, "You could send a telegram to the past."
Alvaro de Rujula, a theorist at CERN, called the new claim "flabbergasting."
"If it is true," he said, "then we truly haven't understood anything about anything. It looks too big to be true. The correct attitude is to ask oneself what went wrong."
The group reporting the results is known as OPERA, for Oscillation Project with Emulsion-Tracking Apparatus. Antonio Ereditato, the University of Bern physicist who heads the group, agreed with de Rujula and others who expressed shock. He told the BBC that OPERA — after much internal discussion — had decided to put its results out there to have them scrutinized.
"My dream would be that another, independent experiment finds the same thing," Ereditato told the BBC. "Then I would be relieved." Drew Baden, chairman of the physics department at the University of Maryland, said it is far more likely that there are measurement errors or some kind of fluke. Tracking neutrinos is difficult, he said.
"This is ridiculous what they're putting out," Baden said. "Until this is verified by another group, it's flying carpets. It's cool, but ... ."
Neutrinos are among the weirdest denizens of the quantum subatomic world. Once believed to be massless and to travel at the speed of light, they can sail through walls and planets like wind through a screen door.
Moreover, they come in three varieties and can morph from one form to another as they travel along, an effect the OPERA experiment was designed to detect by comparing 10-microsecond pulses of protons on one end with pulses of neutrinos at the other. de Rujula noted, however, that it was impossible to identify which protons gave birth to which neutrino, leading to statistical uncertainties.
Ellis noted that a similar experiment was reported by a collaboration known as Minos in 2007 on neutrinos created at Fermilab in Illinois and beamed through Earth to the Soudan Mine in Minnesota. That group found, though with less precision, that the neutrino speeds were consistent with the speed of light.
John Learned, a neutrino astronomer at the University of Hawaii, said the results of the OPERA researchers, if true, could be the first hint that neutrinos can take a shortcut through space, through extra dimensions.
"Special relativity only holds in flat space, so if there is a warped fifth dimension, it is possible that on other slices of it, the speed of light is different," said Joe Lykken of Fermilab. But it is way too soon for such speculation. The OPERA results will generate a rush of experiments aimed at confirming or repudiating it, according to Learned.
"This is revolutionary and will require convincing replication," he said.
Material from The Associated Press is included in this report.
Another Version of the same report:
Neutrinos, like the ones above, have been detected travelling faster than light, say particle physicists. Photograph: Dan Mccoy /Corbis
It is a concept that forms a cornerstone of our understanding of the universe and the concept of time – nothing can travel faster than the speed of light.
But now it seems that researchers working in one of the world's largest physics laboratories, under a mountain in central Italy, have recorded particles travelling at a speed that is supposedly forbidden by Einstein's theory of special relativity.
Scientists at the Gran Sasso facility will unveil evidence on Friday that raises the troubling possibility of a way to send information back in time, blurring the line between past and present and wreaking havoc with the fundamental principle of cause and effect.
They will announce the result at a special seminar at Cern – the European particle physics laboratory – timed to coincide with the publication of a research paper describing the experiment.
Researchers on the Opera (Oscillation Project with Emulsion-tRacking Apparatus) experiment recorded the arrival times of ghostly subatomic particles called neutrinos sent from Cern on a 730km journey through the Earth to the Gran Sasso lab.
The trip would take a beam of light 2.4 milliseconds to complete, but after running the experiment for three years and timing the arrival of 15,000 neutrinos, the scientists discovered that the particles arrived at Gran Sasso sixty billionths of a second earlier, with an error margin of plus or minus 10 billionths of a second.
The measurement amounts to the neutrinos travelling faster than the speed of light by a fraction of 20 parts per million. Since the speed of light is 299,792,458 metres per second, the neutrinos were evidently travelling at 299,798,454 metres per second.
The result is so unlikely that even the research team is being cautious with its interpretation. Physicists said they would be sceptical of the finding until other laboratories confirmed the result.
Antonio Ereditato, coordinator of the Opera collaboration, told the Guardian: "We are very much astonished by this result, but a result is never a discovery until other people confirm it.
"When you get such a result you want to make sure you made no mistakes, that there are no nasty things going on you didn't think of. We spent months and months doing checks and we have not been able to find any errors.
"If there is a problem, it must be a tough, nasty effect, because trivial things we are clever enough to rule out."
The Opera group said it hoped the physics community would scrutinise the result and help uncover any flaws in the measurement, or verify it with their own experiments.
Subir Sarkar, head of particle theory at Oxford University, said: "If this is proved to be true it would be a massive, massive event. It is something nobody was expecting.
"The constancy of the speed of light essentially underpins our understanding of space and time and causality, which is the fact that cause comes before effect.
"Cause cannot come after effect and that is absolutely fundamental to our construction of the physical universe. If we do not have causality, we are buggered."
The Opera experiment detects neutrinos as they strike 150,000 "bricks" of photographic emulsion films interleaved with lead plates. The detector weighs a total of 1300 tonnes.
Despite the marginal increase on the speed of light observed by Ereditato's team, the result is intriguing because its statistical significance, the measure by which particle physics discoveries stand and fall, is so strong.
Physicists can claim a discovery if the chances of their result being a fluke of statistics are greater than five standard deviations, or less than one in a few million. The Gran Sasso team's result is six standard deviations. Ereditato said the team would not claim a discovery because the result was so radical. "Whenever you touch something so fundamental, you have to be much more prudent," he said.
Alan Kostelecky, an expert in the possibility of faster-than-light processes at Indiana University, said that while physicists would await confirmation of the result, it was none the less exciting.
"It's such a dramatic result it would be difficult to accept without others replicating it, but there will be enormous interest in this," he told the Guardian.
One theory Kostelecky and his colleagues put forward in 1985 predicted that neutrinos could travel faster than the speed of light by interacting with an unknown field that lurks in the vacuum.
"With this kind of background, it is not necessarily the case that the limiting speed in nature is the speed of light," he said. "It might actually be the speed of neutrinos and light goes more slowly."
Neutrinos are mysterious particles. They have a minuscule mass, no electric charge, and pass through almost any material as though it was not there.
Kostelecky said that if the result was verified – a big if – it might pave the way to a grand theory that marries gravity with quantum mechanics, a puzzle that has defied physicists for nearly a century.
"If this is confirmed, this is the first evidence for a crack in the structure of physics as we know it that could provide a clue to constructing such a unified theory," Kostelecky said.
Heinrich Paes, a physicist at Dortmund University, has developed another theory that could explain the result. The neutrinos may be taking a shortcut through space-time, by travelling from Cern to Gran Sasso through extra dimensions. "That can make it look like a particle has gone faster than the speed of light when it hasn't," he said.
But Susan Cartwright, senior lecturer in particle astrophysics at Sheffield University, said: "Neutrino experimental results are not historically all that reliable, so the words 'don't hold your breath' do spring to mind when you hear very counter-intuitive results like this."
Teams at two experiments known as T2K in Japan and MINOS near Chicago in the US will now attempt to replicate the finding. The MINOS experiment saw hints of neutrinos moving at faster than the speed of light in 2007 but has yet to confirm them.