Monday, February 27, 2012

Superluminosity Redux

Remember that story from last September, about the startling report by a group of physicists at the OPERA neutrino detector in Italy and how they'd apparently been measuring neutrinos traveling superluminally? The paper said that, on average, neutrinos were making the trip in about 60 nanoseconds less than it would take light to make the trip. The paper generated some major waves in the science community, as it appeared to go against everything we thought we knew about relativity. However, despite the startling (and frankly, alluring) possibilities faster-than-light travel would open up, most people (myself included) remained highly skeptical, given that relativity has always been correct every single time it's been tested.

Now, it appears that the answer to the question may be as simple as a loose cable connection. Scientists at OPERA have said that they found a loose connection in a fiber optic cable that brings signals from GPS satellites to OPERA and its main detector. When the cable was tightened and re-tested, data was found to arrive around 60 nanoseconds faster than previously thought...which is just about the time discrepancy seen in the experiment. The paper claimed a time accuracy of \(\pm10\) nanoseconds, so if the 60 nanosecond systematic error is removed, it's quite possible (and most likely) that the neutrinos are traveling just a bit slower than light \(-\) although not by much, certainly.

There's another interesting tidbit lurking here, though: according to the scientists, there may be another error in the setup, involving a piece of equipment that time-stamps the neutrino arrivals \(-\) but this error might actually increase the speed of the neutrinos over what was claimed previously. I haven't found any estimates of the time increment this might have, and it remains to be seen if it actually exists, but rest assured I will keep you informed when I find anything.

In all likelihood, this is how it will end up. The timing error by a loose cable will be found to account for the discrepancy, and relativity will stand triumphant once again. I'll be the first to admit it would be pretty interesting for the opposite to be true, and for the neutrinos to actually be moving superluminally \(-\) but that's how science works. It's a search for the truth (or at least it should be), not what you want to be true. And, really, relativity is already pretty incredible as it is. I mean, the very fabric of spacetime fluidly adjusting itself so that light in a vacuum always moves at a particular speed relative to an observer? Time actually slowing down in a gravitational potential well? Space being something that curves and deforms based on the presence of mass-energy (which are really just two aspects of the same thing)? How impossibly cool is that??

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