Scientists reject rivals' light-speed claims

A study showing that sub-atomic particles can travel faster than the speed of light – thereby overturning more than 100 years of theoretical physics established by Albert Einstein – must be wrong, according to a rival team of physicists.

Last September, scientists involved in the international Opera experiment said that a beam of neutrinos had arrived 60 billionths of a second faster than light would have travelled from the underground particle physics laboratory at Cern in Geneva to the Gran Sasso facility in Italy, 466 miles away.

Over the weekend, the Opera scientists said they had repeated the experiment with minor modifications to the length of the particle beam to take into account a possible source of error. They said they found the same result – neutrinos that could travel faster than light.

Under Einstein's theory of relativity, nothing can travel faster than the speed of light. Otherwise, it would be possible to travel through time.

Now a second group of scientists, part of the Icarus collaboration, has re-analysed the same beam and concluded that the particles could not have travelled faster than light speed without exhibiting a fall in energy levels, which was not detected.

The re-analysis of the same neutrino beam by the Icarus group of physicists is the first serious study to question the "faster-than-light" findings that have astonished and confounded scientists in equal measure. Physicists involved in the Icarus collaboration have posted the new interpretation of the Opera's results on a scientific website stating that the neutrinos would have lost discernible amounts of energy had they travelled faster than the "universal constant" of light speed – about 186,282 miles per second.

As this was not the case, the particles could not have travelled faster than light, the Icarus team said. "Our results therefore refute a superluminal [faster than light speed] interpretation of the Opera result."

Tommaso Dorigo, a high-energy physicist at Cern who was not part of the Icarus group, said that the Icarus study is "very simple yet definitive" in refuting the almost heretical notion that sub-atomic particles can travel faster than light.

"The Icarus result says that the difference between the speed of neutrinos and the speed of light cannot be as large as that seen by Opera, and is certainly smaller than that by three orders of magnitude and compatible with zero," Dr Dorigo said on his blog. A definitive answer to the question of whether the Opera results hold water may have to wait until next year when scientists involved in the Minos consortium will carry out similar tests with American particle accelerators in Illinois.