CERN scientists believe they've established just how neutrinos were apparently able to travel faster than light.
Last September, scientists working on CERN's Opera experiment reported that the subatomic particles were reaching Gran Sasso in Italy very slightly sooner than they should. If true, this would have meant that Einstein's special theory of relativity was wrong, and that the speed of light could be exceeded.
The team eventually identified two possible sources of error - the crystal oscillator which was timestamping the events and an optical fiber connection.
Both of these are still possible problems, says CERN - but the first would actually have made the neutrinos appear to travel too slowly. In other words, whether or not the oscillator's working properly, it's the connection that seems to have caused the 'faster-than-light' journey.
The optical fiber connector that carries the external GPS signal to the Opera master clock may not have been working correctly when the measurements were taken, CERN has confirmed, which would have increased the neutrinos' apparent speed.
The Opera team won't know for sure what's been going on until the original experiment is repeated, with more tests scheduled for May.
"While continuing our investigations, in order to unambiguously quantify the effect on the result, the collaboration is looking forward to performing a new measurement of the neutrino velocity as soon as a new bunched beam is available in 2012," it says.