Neutrinos May Not Travel Faster Than Light After All

Researchers in Italy say a bad connection between devices could explain a startling result they had last year, when they thought they'd witnessed particles traveling faster than the speed of light. Further tests await, but it appears there was a subtle problem with the equipment at the lab, as many physicists had expected. The laws of physics may not need to be rewritten after all.

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Albert Einstein said nothing should travel faster than the speed of light, so it was quite a shock last year when physicists in Italy said they had evidence that a subatomic particle called the neutrino was violating that cosmic speed limit.

Many scientists suspected the result was just a subtle error in the experiment and, as NPR's Richard Harris reports, now there's a possible culprit.

RICHARD HARRIS, BYLINE: You know how your cell phone might not charge up if you don't get it plugged in quite right? Well, it turns out that something almost that mundane might explain the astonishing news last year that neutrinos had been clocked traveling faster than the speed of light.

The lab that did that experiment is buried miles under a mountain in the Italian Alps. The neutrinos in question got fired toward them from an accelerator on the Swiss-French border and they used GPS to synchronize their watches.

But here's the catch. GPS signals don't travel through rock, so the signal came into the buried lab on an optical fiber. Lucia Votano, the head of the Gran Sasso Laboratory, says that fiber plugged into the electronics at the lab.

LUCIA VOTANO: This connector was not perfectly plugged. OK?

HARRIS: Or, at least, that's a problem that the researchers are now investigating. It turns out that this is a finicky connection, and if you don't get it just right, you can get bad information about what time it is. And when you're measuring time in billionths of a second, there's almost no room for error.

As it happens, the scientists in Italy also found another possible problem with their gear. A funky oscillator, if you want to get technical, but that potential problem would actually have made their measurement of the neutrinos too slow, not too fast.

So how to sort this out? Votano says they're gearing up for a new round of experiments this spring. Once again, the lab on the French border will fire neutrinos their way, but this time, several instruments will clock them when they arrive at the Gran Sasso Lab in Italy.

VOTANO: All of these measurements will be independent, each one from the other, so we will have a multiple answer. I mean, independent answer on this velocity neutrino measurement.

HARRIS: And, if you're a betting person, the smart money will be on neutrinos doing what Einstein thought they would do, traveling no faster than the speed of light. Of course, that's not as exciting as tossing out some of the laws of physics, but, oh well.

Richard Harris, NPR News.

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