Scrap the warp drive: New test shows neutrinos not faster than light

This article has been updated to correct the location of the Gran Sasso laboratory.

It looks like warp speed, time travel and other cool stuff from science fiction are still fiction, after all.

A new experiment at the Gran Sasso laboratory in Italy has found that neutrinos don’t travel faster than light, refuting the results of an experiment in September that seemed to find that they did.

The earlier experiment by the Oscillation Project with Emulsion-Racking Apparatus (OPERA) team at Gran Sasso set the physics world on its ear, because the results seemed to disprove Albert Einstein’s assertion in his Special Theory of Relativity — the foundation of a lot of what we know about the universe — that nothing could travel faster than the speed of light.

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The new experiment, from the competing Imaging Cosmic and Rare Underground Signals (ICARUS) team, duplicated the OPERA tests but with different detectors and found that neutrinos travel at light speed, but not faster. “The result is compatible with the simultaneous arrival of all events with equal speed, the one of light,” the scientists said in posting their results.

Both experiments involved shooting subatomic neutrino particles 454 miles from CERN in Switzerland to Gran Sasso in Italy. In Opera’s experiment, the neutrinos arrived 60 nanoseconds sooner than light.

Some physicists immediately expressed skepticism at the results, which in physics terms was like hearing that the sun doesn’t rise in the East, and the OPERA team also said the results had to be verified. In February, scientists said that had found equipment flaws — a loose fiber optic cable and a problem with an oscillator providing GPS time stamps — in the OPERA experiment that could have thrown off the results.

The ICARUS experiment duplicated OPERA’s effort but used a different detector, the Liquid Argon Time Projection Chamber, “a novel detector which allows an accurate reconstruction of the neutrino interactions,” Carlo Rubbia, a Nobel Prize winner and spokesperson for ICARUS, said in a statement issued by CERN.

"ICARUS measures the neutrino's velocity to be no faster than the speed of light,” Rubbia said.

With the new results out, physicists are breathing a sigh of relief. Sandro Centro, another spokesman for ICARUS, told the BBC he, like other physicists, had been skeptical of the OPERA results.

"I didn't trust the result right from the beginning — the way it was produced, the way it was managed," he told the BBC. "I think they were a little bit in a hurry to publish something that was astonishing, and at the end of the day it was a wrong measurement."

So scientists are happy that the universe is what they thought it was, even if science fiction fans might be disappointed that things like intergalactic travel, which would require faster-than-light speed to be feasible, are once again out of reach.

Assuming, of course, that the ICARUS results hold up. Indications are that they will, although CERN Research Director Sergio Bertolucci said in CERN’s statement that “it is important to be rigorous” and that more experiments will be held in May “to give us the final verdict.”

Bertolucci also gave credit to the OPERA team for behaving “with perfect scientific integrity in opening their measurement to broad scrutiny, and inviting independent measurements.

“This,” he said, “is how science works.”

About the Author

Kevin McCaney is a former editor of Defense Systems and GCN.

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