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Which is Faster: Neutrinos or News?

22 September 2011

Many readers may already be familiar with some intriguing news coming from the OPERA neutrino experiment in Europe: they have observed evidence that certain types of neutrinos travel faster than the speed of light!  The BBC and Science News have reported on it and the official technical paper was just posted for reading at  CERN's official press release is now available, too.

What's going on?

OPERA is an accelerator-based neutrino experiment.  An intense beam of muon neutrinos is produced by one of CERN's accelerators and aimed at a cavern inside a mountain in Gran Sasso, Italy, about 732 km away.  The experiment is looking to examine the 'oscillation' of muon neutrinos into so-called tau neutrinos.  Along the way, someone thought to measure the time it took for the neutrinos to travel from Switzerland to Italy.  Special relativity tells us that the speed of light is the ultimate speed limit.  The OPERA research team found that the neutrinos took less time than expected, or about 60 billionths of a second faster than what should be about a 3 thousandths of a second journey.  Now, no measurement is worth anything if it doesn't include an analysis of the uncertainties associated with it.  After much painstaking work, the OPERA team concluded that their uncertainty on the measurement is 10 billionths of a second.  Their measurement is 6 times that; in statistical terms, this is a six-sigma result (if they have understood their sources of uncertainty properly).

"Over 3 years, OPERA researchers timed the roughly 16,000 neutrinos that started at CERN and registered a hit in the detector. They found that, on average, the neutrinos made the 730-kilometer, 2.43-millisecond trip roughly 60 nanoseconds faster than expected if they were traveling at light speed." -- Science News

There are many, many stringent tests of special relativity.  It would be surprising, actually shocking, to see this claim verified and shown to be correct.  But science crawls inexorably forward by verifying or overturning results every day, slowly contributing to more and more sophisticated models that increase their predictive accuracy and precision. Sometimes those models are substantially revised!

What's going on, really?

OPERA is scheduled to present their analysis and results to the world on Friday evening, European time, at CERN (webcast). The technical paper describing their work went online on Thursday night. The news that OPERA had some interesting results spread around the world as early as Sep 19 when a blogger started to share the analysis.  The virtual science-news sphere lit up almost immediately and soon the mainstream news, radio, and television media got interested.  Could it be true?  Could we finally have the evidence to modify Einstein's Special Theory of Relativity? The challenge for the rest of the scientific world has been that the technical paper wasn't released until Thursday evening, several days after the media started asking questions.

So, in this case, news of the neutrino speed-limit violations far oustripped the science of the neutrino!

As Kostelecky is quoted to have said, "Extraordinary Claims require Extraordinary Evidence!"  Let's see what happens.


--by T.I. Meyer, Head, Strategic Planning & Communications

You can join in the discussion with our colleagues and other physics-minded followers on the Quantum Diaries blog.

p.s. If you tweet, look for #mundaneneutrinoexplanations for a good chuckle.  Thanks, JG!