Not so fast, neutrinos. CERN says light's speedier still

Physics laws appear to be holding up fine with a second experiment showing CERN's neutrinos traveling more sedately than in last year's surprising finding.

As part of the OPERA experiment, physicists tracked how long it takes for neutrinos generated at CERN to reach a detector 730km away in Italy.
As part of the OPERA experiment, physicists tracked how long it takes for neutrinos generated at CERN to reach a detector 730km away in Italy. National Institute of Nuclear Physics (ITFN) in Italy

New experimental evidence is helping disprove last year's highly surprising finding of neutrinos breaking established physics laws by traveling faster than light.

The finding involved clocking the neutrinos--tiny, nearly massless subatomic particles--as they traveled from the CERN particle accelerator near Geneva to the Gran Sasso National Laboratory in Italy, about 730km away. An experiment called Opera found the neutrinos taking less time to arrive than light would, but now another Gran Sasso experiment, Icarus, showed neutrinos making the journey at a more sedate pace under light speed, CERN said.

That finding comes after news in February that a fiber-optic connection problem could have shown too short a neutrino time of flight, though another factor could mean the timing was wrong the other way.

Physicists involved never proclaimed it was time to rewrite physics--just that it was time to check the experiment very carefully first. There's no final judgment yet, but it's clear which way opinions are tilting.

"The evidence is beginning to point towards the OPERA result being an artifact of the measurement," said CERN Research Director Sergio Bertolucci in a statement today. However, to be rigorous about the matter, the laboratories plan to rerun the experiment in May and cross-check it with data involving cosmic ray particles.

"Whatever the result, the OPERA experiment has behaved with perfect scientific integrity in opening their measurement to broad scrutiny, and inviting independent measurements," Bertolucci said. "This is how science works."

Updated at 11:48 a.m. PTto correct a reference in the caption of the main image to neutrinos, not neutrons.

The Globe of Science and Innovation has no scientific function, but the center is a distinctive CERN landmark. Stephen Shankland/CNET
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