Faster-than-light’ travel explained

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Faster-than-light’ travel explained

By Clive Cookson

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Scientists claiming to have overthrown one of the central dogmas of physics – that nothing can travel faster than light – set out their stall on Friday with a sober technical presentation at Cern, the European nuclear research organisation near Geneva.

As the world of physics buzzed with excitement about a possible revolution in understanding the universe, though restrained by deep scepticism about the experimental results, the researchers explained the basis of their conclusion that subatomic particles – neutrinos – travelled faster than light on a 730km journey from Cern to the Gran Sasso underground laboratory in central Italy.

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Dario Autiero, who presented the results of the Opera experiments to colleagues in the Cern auditorium, challenged colleagues elsewhere to scrutinise them “because of their potentially great impact on physics”.

“Although our measurements have low systematic uncertainty and high statistical accuracy, and we place great confidence in our results, we’re looking forward to comparing them with those from other experiments,” Professor Autiero said.

Scientists involved in two other neutrino beam projects, in Japan and US, said they would re-examine existing data and produce new results to compare with those from Opera.

The Minos experiment at Fermilab outside Chicago found neutrinos possibly breaking the speed of light by a small margin in 2007 but the scientists there decided that their results were not statistically significant.

Jenny Thomas of University College London, who is working on the Minos neutrino experiment, said the US project would rise to Cern’s challenge. “The impact of this measurement, were it to be correct, would be huge. In fact it would overturn everything we thought we understood about relativity and the speed of light,” she said.

After the presentation at Cern, the Opera scientists received warm applause, followed by probing technical questions from colleagues about how they had measured the distance travelled by the neutrinos and their time of flight accurately enough to conclude that they had really travelled faster than light.

Although the excess speed was small – an increase of less than 0.01 per cent – the experimenters said it was well above the margin of error for the project.

The Cern scientists refused point-blank to indulge in any speculation about how their neutrinos might have broken the cosmic speed limit or to take any questions about what their results, if confirmed, might mean for our understanding of the universe. But theorists elsewhere have already set to work.

One idea is that, as many physicists believe, there are hidden extra dimensions of space and time beyond our familiar four (time and three spatial dimensions). If neutrinos can access some of these extra dimensions, they might be able to use them as short-cuts to reach the target more quickly. Hidden dimensions predicted by “string theory” are on the list of possible discoveries to be made by Cern’s huge atom smasher, the Large Hadron Collider.

A related possibility is that the neutrinos travel through a warped form of space-time, which might enable them to move more quickly than ordinary light.

But science fiction enthusiasts should not get too enthusiastic. The speed boost apparently given to the Opera neutrinos took their velocity just above 300,000 kilometres per second from the 299,792km/sec of light. At that rate it would still take many human lifetimes to travel far into our galaxy. And cosmic wormholes still seem a better bet for an intergalactic journey.

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