One of the biggest stories in science last year was the announcement by a European physics collaboration that neutrinos can seemingly travel faster than light. Most physicists were skeptical of the result, which would upend a well-tested tenet of modern physics—namely, that nothing outpaces light. And the researchers on the OPERA experiment that made the measurement were themselves very cautious, stating only that they had found a discrepancy that they could not get rid of.
Today reports emerged that problems with GPS synchronization could explain away the anomalous neutrino velocities, although specific details have yet to be confirmed. ScienceInsider’s Edwin Cartlidge reported that a “bad connection between a GPS unit and a computer may be to blame” but cited only anonymous “sources familiar with the experiment.”
The Associated Press got an official if unspecific confirmation from CERN spokesperson James Gillies that “a problem in the GPS system used to time the arrival of neutrino particles was discovered earlier in February.” CERN is the Geneva laboratory for particle physics where the neutrino beam originates; OPERA detects the particles hundreds of kilometers away, in a lab buried in an Italian mountainside, and clocks their velocity on the journey.
Now MSNBC’s Alan Boyle reports that two potential issues have been identified:
One has to do with a fiber-optic connector that sends a GPS time stamp to the experiment's master clock. That connector may not have been functioning correctly when the neutrino-timing measurements were made, and as a result, the recorded flight time would be shorter than the actual time. That alone could explain the seemingly faster-than-light results.
Another potential problem has to do with the oscillator that was used to generate the time stamps for GPS synchronization. This problem could have made the flight time look longer than it really was.
Boyle’s sources requested anonymity because they were not authorized to speak yet on the subject. OPERA, he reports, will issue an official statement on Thursday about the new information. That means that we should know more soon, although it may take some time before physicists can test the effects of any potential glitches.
UPDATE (6:35 P.M.): Nature News is reporting that an official statement from OPERA confirms that two possible GPS-related problems are being investigated.