“Faster Than Light” Neutrinos Likely the Result of a Bad Cable Connection
Posted by mattusmaximus on February 23, 2012
**Update (2-25-12): It seems the situation is a bit more complicated than previously thought, and there is another potential source of error that has been discovered. More details at this CERN link: http://press.web.cern.ch/press/PressReleases/Releases2011/PR19.11E.html
Last September you may recall quite a bit of buzz going around about the supposed discovery of faster-than-light neutrinos. While the media was going nuts about it, and while various cranks were crowing about “the physics establishment being overturned”, a number of scientists and science bloggers (including me) expressed great interest in this experimental result while also providing a cautious dose of skepticism about the entire affair. That’s because a theory that is so well-tested as Einstein’s relativity could be overturned or radically adjusted by such a result only if we were absolutely sure of the outcome; and, at the time, not even the scientists who announced the FTL result were very sure of it…
This tended to be the general view among physicists about the apparent “faster-than-light” neutrinos 🙂
Well, it seems our skepticism was well-founded. From a recent post on the Science Insider blog, it looks as if the “faster-than-light” neutrino signal (which amounted to a discrepancy of 60 nanoseconds or 0.000 000 060 seconds) was probably the result of a bad cable connection…
It appears that the faster-than-light neutrino results, announced last September by the OPERA collaboration in Italy, was due to a mistake after all. A bad connection between a GPS unit and a computer may be to blame.
Physicists had detected neutrinos travelling from the CERN laboratory in Geneva to the Gran Sasso laboratory near L’Aquila that appeared to make the trip in about 60 nanoseconds less than light speed. Many other physicists suspected that the result was due to some kind of error, given that it seems at odds with Einstein’s special theory of relativity, which says nothing can travel faster than the speed of light. That theory has been vindicated by many experiments over the decades.
According to sources familiar with the experiment, the 60 nanoseconds discrepancy appears to come from a bad connection between a fiber optic cable that connects to the GPS receiver used to correct the timing of the neutrinos’ flight and an electronic card in a computer. After tightening the connection and then measuring the time it takes data to travel the length of the fiber, researchers found that the data arrive 60 nanoseconds earlier than assumed. Since this time is subtracted from the overall time of flight, it appears to explain the early arrival of the neutrinos. New data, however, will be needed to confirm this hypothesis. [emphasis added]
If true (and my money is on it being true), it wouldn’t surprise me at all. When I was an undergraduate doing research work in a mass spectrometry lab, it took me and my lab mate a couple of days to figure out why the damn thing wasn’t working properly. After almost two days of checking everything (every setting, every seal on the chamber, every line of code), what was the error?
Answer: a bad BNC cable *facepalm*
And I was just working on a lousy table-top sized mass spectrometer. I can barely imagine the level of complexity in dealing with an experiment of the scale of the CERN-OPERA operation; the fact that they could have missed a lone, loose fiber optic cable doesn’t surprise me at all.
While I’m pretty certain that this error (or similar ones) will explain the situation, I still think it is worthy for some outside research group to attempt a replication of the original, apparent FTL neutrino result. I say that because it could be worth really nailing down exactly what went wrong in this whole experiment so that other researchers don’t make similar mistakes in the future. Of course, there is the outside chance (however infinitely remote that may be) that perhaps there is something legitimate to the FTL result.
Either way, science marches on and we learn something about the universe. Neat, eh? 🙂