Feb 27 2012

FTL Neutrinos? Einstein Can Rest Easy

Last September the OPERA collaboration in Italy announced that they had detected neutrinos apparently traveling faster than the speed of light. In their experimental setup the neutrinos arrived about 60 nanoseconds ahead of what the speed of light would have produced. The first persons to be skeptical of this result were the researchers themselves. They understood that this result is at odds with perhaps the most confirmed theories in all of science – Einstein’s theories of special and general relativity. According to relativity theory nothing can travel faster than the speed of light in a vacuum. This is not a practical limitation, it is inherent to the fabric of the universe.

Every now and then a lab somewhere claims to have broken this law of relativity, but in every case (so far) it seems that they simply made an experimental error or interpreted their results incorrectly. This ultimate speed limit seems to be as solid a law of physics as the conservation of energy, and experiments that seem to break this law suffer the same fate as those who believe they have invented a perpetual motion or free energy machine.

This claim, however, was different because the scientists exhaustively searched for any possible source of error they could think of and eliminated it, and the 60 nanosecond discrepancy persisted. Only when they did everything they could to disprove their results did they announce them to the world – still with the proper caution that was due. They essentially asked the rest of the scientific community to help them find the source of the error, while tentatively saying that if their results are true, wouldn’t that be interesting.

The claim was met by the scientific community with the proper skepticism. Most scientists did not believe the results and were confident that the source of error would be found. Some cited the fact that light and neutrinos from very distant supernova arrive at the earth at almost the same time (relatively) and therefore neutrinos must be traveling at the speed of light. True – unless the experimental neutrinos act differently because they are at a different energy level. This is not a convincing argument, but is theoretically possible. The general thinking was this – what is more likely, that the laws of physics have been overturned, or that this very complicated experimental setup has some minor source of error that is yet to be detected?

The response of the media was mixed, as you might expect. Many articles included the proper scientific skeptical response, but many also emphasized the amazing results. Anecdotally I encountered people in the public who only took from this story that something was found to travel faster than the speed of light, so Einstein was wrong, and that proves that scientists don’t really know what they are talking about, so whatever crazy theory they happen to prefer may be true also.

I joined the majority of scientists and skeptics who were confident that some source of experimental error would be found (which is just playing the odds). It would be fascinating and a huge science story if it turned out to be correct, but just terribly unlikely.

It is therefore not surprising that the apparent source of error has now come to light. According to the AAAS: 

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.

Even in this scientists are being properly cautious. This is a potential explanation for the neutrino anomaly, but it needs to be confirmed. It seems likely, however, given that this effect matches the 60 nanosecond discrepancy of the previous experiments.

I love this whole science news story. It is a great opportunity to teach the public how science really works. The original scientists were skeptical of their own results and did everything they could to find their own error. When they couldn’t, they published their results, but without grandiose claims of changing our understanding of the universe and overturning a century of physics. The scientific community met the claims with skepticism and immediately started suggesting possible sources of error, each one was investigated to see if it were actually true. Meanwhile the implications of the claim were discussed, to put them into the proper context of data that we already have. If this experiment is true, then how do we square that with previous observations and experiments?

Now, it seems, the anomaly has been resolved, but that has to be confirmed as well.

Science is a self-skeptical, self-corrective but messy process. It would be great for the public to have a greater appreciation for this, so that they can more easily smell pseudoscience when they encounter it.

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