That neutrinos travel 60 nanoseconds faster than light must be an “artefact of measurement,” after all. The results announced last week by the ICARUS team means that Einstein's 1905 theory of Special Relativity that nothing travels faster than light — the cornerstone of modern physics — is still valid. The reconfirmation of light's eminent place comes in the wake of the September 23, 2011 announcement by the Oscillation Project with Emulsion-tRacking Apparatus (OPERA) team that the subatomic particles travelled faster than light. Both the teams used the same extremely short duration neutrino pulses to reconfirm the time taken for the neutrinos fired at CERN to reach the Gran Sasso National Laboratory in Italy located 730 km away. The ICARUS team led by Nobel Laureate Carlo Rubbio analysed the speed of seven such pulses using a different technique. While OPERA continued to find the neutrinos travelling faster than light by 60 nanoseconds (with an uncertainty of 10 nanoseconds), ICARUS found that the speed of subatomic particles was just four nanoseconds faster than light, well within the “experimental margin of error.” “These [the neutrinos] arrived in a time consistent with the speed of light,” notes the CERN press release.

Researchers have been poking holes ever since OPERA first published its results. Nobel Laureate Sheldon Glashow's immediate criticism that the superluminal neutrinos did not exhibit any effect similar to Cerenkov radiation that would essentially reduce the particle's energy during its journey was strengthened by the ICARUS group's observation last November. The team did not find any evidence that the neutrinos travelling faster than light had lost energy during their 730 km journey. Though this observation had an element of implausibility, the remote possibility of some unknown mechanism playing a role could not be ruled out. But Rubbio's latest results settle the issue. Fresh measurements by both the teams are to be made when the experiment is repeated in May. But there is only a slim chance of OPERA proving to be right as it had recently disclosed two possible faults that could have led to an error in the speed calculation. While many would criticise OPERA's researchers for their haste in announcing the extraordinary results before checking for all possible errors, the way the team conducted itself was perfectly in line with the methods of science. The group had checked the accuracy of data of more than 15,000 neutrinos for about six months before going public. It never claimed to have proved that neutrinos travel faster than light. In fact, it wanted a reconfirmation of the results by others. Publishing its data was one of the best ways of achieving this end.

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