Neutrinos May Stick to Speed Limit After All

Part of the detector used in the OPERA experiments. Source: © CERN 2006

Anyone with a passing interest in science news will no doubt remember that last September researchers working on the OPERA project at CERN reported that they had measured neutrinos, a tiny sub atomic particle, travelling faster than the speed of light. This finding defied the laws of relativity that were proposed by Einstein a century or so ago, that defined that nothing could travel faster than the speed of light.

Did this mean that the laws of physics would need to be rewritten? Could time travel be possible? Would neutrinos get fined and lose their driver’s license for going faster than the cosmic speed limit?

Understandably, the researchers were pretty excited by this discovery but knew the significance of it being true. Before claiming anything for certain they put the word out to the rest of the scientific community to ask if they could find any mistakes.

Since then I hadn’t heard much about it until yesterday when I saw a news article pop up stating that they had found a problem in the connection between a GPS unit and the central timing device used in the measurements. Preliminary tests suggested that this resulted in the unit registering activity approximately 60 nanoseconds earlier than it should have. This would appear to explain last year’s finding of neutrinos arriving 60 nanoseconds earlier than the speed of light. While they still had to run the full experiment to be sure, this appeared to me to solve the problem completely. But of course, that’s never the full story.

Today I’ve found more comprehensive reports that describe two possible faults. As well as the fault between GPS and central clock that could have made the neutrinos seem faster, a fault in an oscillator used to synchronise the GPS units may have measured the neutrinos as slower than what they actually were. So it’s possible that they can actually travel even faster than what the first reports suggested!

Since the initial measurements became news last year plans have been made to replicate the experiment by teams in Europe, the USA and possibly Japan. The OPERA team will also be repeating the experiment again after fixing the possible faults in the system. However, it will take some time to set up, perform and analyse the results from this experiment. But when the consequences affect our understanding of the universe this much, you want to get things right.

I suspect that the measurement of the neutrinos speed will be shown to be wrong and there will be no need to change the laws of physics (for now at least). However, my opinion is not based on any in depth knowledge of physics or these experiments, just the idea that it easier to make a small mistake in an experiment that involves this much high tech gadgetry spread 730kms apart than it is to make a discovery this significant.

For now, we’ll just have to play the waiting game and see what pops up in the news next.


UPDATE (17th March): A separate research team at CERN, from the Icarus group, have reportedly adjusted their own experiments to measure the speed of neutrinos. The results measure neutrinos travelling at the same speed as light, not faster. Read more about it at BBC News now, and probably other places soon.



See the links to news reports above


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