Researchers say they have found a possible flaw in the setup of an experiment that appeared to show particles traveling faster than light.
The result of the experiment was met with widespread skepticism by the scientific community when it was announced last September by the Geneva-based European Organization for Nuclear Research, or CERN.
The speed of light was considered by physicist Albert Einstein to be the ultimate speed barrier.
In an interview with RFE/RL correspondent Eugen Tomiuc, CERN spokesman James Gillies said two potential issues have been identified that could have influenced the timing of the speed of neutrino particles during the Swiss-Italian experiment known as OPERA (Oscillation Project with Emulsion-Racking Apparatus experiment).
Gillies told RFE/RL that results of further measurements and tests will be announced later this year, but it looks increasingly likely that Einstein will be proven right after all.
RFE/RL: Scientist and layman alike were surprised and skeptical when CERN announced last September that neutrinos -- electrically-neutral particles -- had traveled the 730 kilometers from Geneva to Italy’s Gran Sasso 60 nanoseconds faster than light. If proven correct, the implications were enormous. Now we are being told that this ultra-sophisticated experiment may have gone slightly wrong. What’s the explanation?
James Gillies: First of all, we don't yet know whether there is an explanation, and we won't know that for sure until we repeat the measurements with [the] beam.
But what the OPERA collaboration has seen is two possible effects in their operators that could affect their timing measurement.
One is the frequency of an oscillator which was not what it had been expected to be, and the other is an optical fiber connection that brings the GPS signal from the GPS system into the OPERA experiment's master clock. What they've done is measure these things now, and found them to be not what they would've expected.
Whether that was the case when they were taking data with the beam last year and before, we can't possibly know. So, although there is suspicion now pointing at the operators, we do need to do more tests with the beam before we can be absolutely certain.
RFE/RL: But for such a complex experiment, would it be possible that it all boils down to a loose fiber-optic cable, as was initially reported?
Gillies: I saw in some places that this was reported as a loose cable. Now optical fiber systems are a little more subtle than that.
It's more than a loose cable, and these kinds of things have been looked for, [and] looked for, [and] looked for over and over again.
And I have to stress that we just don't know for sure, we won't know for sure until we've repeated the measurements with [the] beam from CERN.
RFE/RL: There was a second test in November which appeared to confirm the results of the first one, in spite of persisting skepticism among scientists. Did they get it wrong twice in a row?
Gillies: The first test was with quite a wide beam pulse from CERN, and the second test was with a much narrower beam pulse from CERN, which allowed the experiment at the other end to tie down the neutrinos arriving to a three-nanosecond departure window from CERN.
And results from those two sets of measurements are compatible. So if these two features had been present both times, than that would be also quite consistent. If they weren't present both times then the effect would still stand.
RFE/RL: What’s the next step? Could the experiment be repeated? And if so, how soon?
Gillies: The OPERA experiment informed CERN of this last night. Now up to last night the accelerator operation schedule for CERN [said it] will beam to Gran Sasso in May. Now I know that that's being discussed but it's too early to say whether that will be brought forward or not."
RFE/RL: So is there still a slight chance that Einstein might be proven wrong in the end?
Gillies: I think that the jury is still out, but the bulk of the feeling is that Einstein is not going to be proven wrong and that something will be found in the operators.
I think that most of the physics community would believe that, but it's a very, very subtle measurement to make.
So it's quite impressive that it's possible to [get] this kind of precision at all."