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Has Light Speed Finally Been Surpassed?

 

HAVE scientists finally found something which breaks the great universal ‘speed limit’ of light? Martin Hickes reports.

In an ever changing universe, scientists have long used one great cosmic benchmark.
 

Since the days of Albert Einstein and his astounding scientific theories of the early 20th C, the speed of light has always been the great constant or ‘speed limit’ against which all others things have been measured.

Enshrined in his two great theories of relativity, scientists for years have long believed that nothing can travel faster than the speed of light.

The theory has been so long one of the great pillars of physics and cosmology that it has formed a fundamental cornerstone in scientific thinking, and underpins not only the great Standard Model of Physics but our basic understanding of the universe itself.

But this weekend at CERN, the home of the Large Hadron Collider, excited murmurings have begun about whether something which seemingly travels faster than light might have been finally detected.

And if it can be confirmed for certain, the scientific community might be forced to undertake the biggest rethink in its history.

In a specially gathered live webcast just this weekend, a team has been unveiling to an excited audience of scientists¸ and to the watching world, how the curious properties of particles called neutrinos might hold the key to the universe.

As a bi-product of on-going research into such, scientists working on the OPERA (Oscillation Project with Emulsion tRacking Apparatus) have been sending bursts of the tiny particles through the earth (using a neutrino beam supplied from CERN)  to a laboratory at Gran Sasso, 730km away underneath a mountain in Italy.

To their immense surprise, preliminary results from the experiment suggest that the neutrinos – which like all things in the universe must obey the law of physics – may have arrived at the target site faster than a beam of light would have done.

Had the neutrinos observed Einstein's laws, the subterranean journey could not have taken longer than the 2.4milliseconds.

However they appear to have instead arrived at Gran Sasso 60 nanoseconds - 60 billionths of a second - earlier than light.

Not a great deal faster – but apparently faster nonetheless – which seemingly goes against science’s most sacrosanct law.

The results are already sending ripples through the scientific community both at the site of the experiment at the cavernous halls of the INFN Gran Sasso National Laboratory, and at CERN, the source of the neutrino beams.

The results, delivered by Dario Autiero, from Institut de Physique Nucléaire de Lyon/CNRS were warmly welcomed by the audience watching this weekend’s special lecture, though many are still sceptical.

'It is a tiny difference but conceptually it is incredibly important,' said Professor Antonio Ereditato, an OPERA spokesman.

 "We have high confidence in our results. We have checked and rechecked for anything that could have distorted our measurements but we found nothing," Ereditato continued. "The finding is so startling that, for the moment, everybody should be very prudent."

The OPERA team were repotedly so cautious about their findings that they have conducted the experiment thousands of times over the last three years, and have opened up their research to other scientists working in the field. "We now want colleagues to check them independently," Ereditato said.

Yorkshire’s Prof Dan Tovey, from the University of Sheffield, working at CERN, who is playing a key role in the ATLAS experiment as part of the Large Hadron Collider team, say the preliminary results are intriguing, but advises caution.

He says: “I would class this under 'extraordinary claims require extraordinary proof'.

“I applaud the initial suggestions but it is highly likely to be the result of an underestimated (or neglected) systematic effect.

“If we were to find particles which apparently travelled faster than the speed of light then this would have fundamental implications for the whole of physics - not least the fact that it would imply that in principle one could send messages backwards in time, violating the principle of causality (e.g. going back in time and killing your mother before you were born etc.).

“There are various weird and wonderful suggestions for how to evade such problems - but the fact remains that theoretically this would cause all sorts of problems. One then has to consider how this relates to other experimental tests of the maximum speed of travel of neutrinos, none of which have seen a similar effect of this magnitude.

“Particularly problematic is the fact that neutrinos from an stellar explosion not long ago called Supernova 1987a were observed to reach the earth three hours before the light from such…but this happened for well understood reasons.

“OPERA is claiming a 60 nanosecond advance over just 730 km by contrast. They state that their claim corresponds to an observation of a neutrino velocity greater than that of light by about 0.0025 %, while the SN1987 result suggests that any such difference in velocity must be less than 2 parts in a billion. So they're going to have to produce some pretty cast-iron evidence if they want to convince people that this effect is 'real'.

“Einstein’s predictions and theories with relevance to light have been tested  time and time again and while I don’t decry the experiment, it would take something absolutely extraordinary for arguably the greatest scientist of our age to be proved wrong.”

“This result comes as a complete surprise,” said OPERA spokesperson, Antonio Ereditato of the University of Bern. “After many months of studies and cross checks we have not found any instrumental effect that could explain the result of the measurement. While OPERA researchers will continue their studies, we are also looking forward to independent measurements to fully assess the nature of this observation.”

“When an experiment finds an apparently unbelievable result and can find no artefact of the measurement to account for it, it’s normal procedure to invite broader scrutiny, and this is exactly what the OPERA collaboration is doing, it’s good scientific practice,” said CERN Research Director Sergio Bertolucci. “If this measurement is confirmed, it might change our view of physics, but we need to be sure that there are no other, more mundane, explanations. That will require independent measurements.”

Prof Frank Close, professor of particle physics from the University of Oxford’s Exeter College, and auithor of the bestselling book ‘Neutrino’ is also cautious.

He says: “Firstly, in my view, this isn’t a discovery. It is an anomaly; they are actually just trying to find whereabouts some oversight might have occurred. In my opinion, it is important to recognise this subtlety.

“Secondly, they are having to measure both distance and time incredibly accurately, and any small error unaccounted for will affect the ratio of distance over time.

“I would reckon it is more likely that there is some yet-to-be included uncertainty in one or both of these measurements, rather than that their ratio rewriting the foundations of science.

“You can fire neutrinos through the earth but you can’t fire a radio wave through and see which arrives first. So the measurement is indirect and there are ample opportunities for some unforeseen error to creep in. My bet is that that is what will transpire.”

ENDS

  • The INFN Gran Sasso National Laboratory (LNGS) is the largest underground laboratory in the world for experiments in particle physics, particle astrophysics and nuclear astrophysics. It is used as a worldwide facility by scientists, presently 750 in number, from 22 different countries, working at about 15 experiments in their different phases. It is located between the towns of L'Aquila and Teramo, about 120 km from Rome.
  • The underground facilities are located on a side of the ten kilometres long freeway tunnel crossing the Gran Sasso Mountain. They consist of three large experimental halls, each about 100 m long, 20 m wide and 18 m high and service tunnels, for a total volume of about 180,000 cubic metres.
  • The OPERA experiment is not actually at CERN - it’s at the Gran Sasso underground lab near l'Aquila in Italy. CERN only provides the neutrino beam.
  • Albert Einstein's theory of special relativity holds that nothing can travel faster than the speed of light. The law was first proposed by Einstein in 1905, and its consequences are far-reaching - the c in the famous equation E=mc2 is the speed of light in a vacuum.
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