This Nature blog post reports on some possible sources of error that may rule out the problem of the superluminal neutrinos reported by the OPERA team earlier in September 2011.
The neutrinos are subatomic particles produced at CERN near Geneva that arrive 2.4 milliseconds later in Italy after travelling unperturbed under the Alps. In Italy, they are measured by detectors from the OPERA team in Gran Sasso.
In September, the OPERA team reported an anomaly in the speed the neutrinos were taking to travel the 700 or so kilometres from Switzerland to Italy. The anomaly meant the neutrinos were arriving 60 nanoseconds too early. That may seem like nothing, but it was enough to be travelling faster than the speed of light.
The OPERA team physicists were extremely wary of annoucing such a discovery - if the neutrinos were indeed superluminal, this would violate Einstein's theory of special relativity. They searched their data for 3 years in order to verify possible sources of errors.
The main difficulty in measuring this contentious speed was to measure with extremely high precision both the distance and time travelled. The first is extremely difficult because neutrinos hardly interact with anything and so when they travel they just race through mountains and even the Earth's crust. Since physicists cannot travel unperturbed through the Earth's crust, they have to make the measurement in convoluted ways.
Measuring the travel time is also difficult, because you have to make sure your clocks in Geneva and Gran Sasso are synchronised to a much better accuracy than 60 nanoseconds.
Yesterday, the OPERA team announced through a CERN press release that they have found two potential sources of error in their time measurement to do with their GPS synchronisation.
However, to first approach the problem is not quite solved: the first potential source of error would actually reduce the anomaly, whilst the second would increase it. The OPERA team cannot conclude anything until they run further tests in May which will hopefully clear the problem.
So watch this space, but most probably only to confirm that Einstein's theory still works down here on Earth.