A screw up not quite faster than the speed of light


An experiment that claimed to clock neutrinos travelling faster than the speed of light, a result which, if true, would have upended modern physics as we know it, may have been fatally flawed. Glitches in the GPS system used to synchronize atomic clocks in the study may have tainted the outcome, according to a number of sources.

Science Insider broke the news Wednesday, simultaneously thrilling skeptics in the physics community and breaking hearts among those who had hoped to form the vanguard of a new time-travelling elite. Citing “sources familiar with the experiment” Edwin Cartlidge wrote that “a bad connection between a fiber optic cable … and an electronic card in a computer” appears to account for the 60 nanoseconds faster than light speed the neutrinos were timed travelling between two research centres in Europe.

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.

Later Wednesday, researchers at OPERA began circulating a statement acknowledging two possible problems with the experiment, Nature reported:

First, the passage of time on the clocks between the arrival of the synchronizing signal has to be interpolated and OPERA now says this may not have been done correctly. Second, there was a possible faulty connection between the GPS signal and the OPERA master clock.

Our own Nick Kohler wrote about the initial experiments in this magazine in November. It’s worth going back and reading his entire story, but just to give you a sense of how revolutionary these results would have been if confirmed, here’s a chunk:

(S)cientists working on the so-called OPERA experiment at the European Organization for Nuclear Research (CERN) outside Geneva generated blasts of neutrinos and sent them south, through the rocky subterranean precincts beneath the Alps, then high into Italy’s Apennines mountains, where, near the city of L’Aquila, they popped up in a neutrino detector at the underground Gran Sasso National Laboratory—a distance, all told, of some 730 km. The latest OPERA findings appear to back those earlier results—the neutrinos arrived a shocking 60 billionths of a second or so faster than a beam of light.

Should that result hold up, physicists will either have to scrap Einstein’s theory of special relativity or accept a range of phenomena now confined to science fiction—for example, that an observer travelling past a swift-flying neutrino would witness the particle hurtling backwards in time and appear at its destination before beginning its journey. The confirmation, made by scientists working on the collaborative OPERA experiment, generated enormous international chatter among physicists, who remain skeptical of the results but who must nevertheless contemplate what it would mean if a faster-than-light, or “superluminal,” neutrino proves real. Such a development would upend everything we know about the concept of “causality,” opening up the possibility of time travel at the subatomic level, and even suggesting the existence of new, hitherto unknown dimensions. More than that, it might require us to contemplate the possibility of wormhole portals connecting a Geneva suburb with the mountains of central Italy.

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A screw up not quite faster than the speed of light

  1. Overall, this was a very productive screw up… it got both the public and the scientists to speculate outside of box.  (Although I don’t personally know of any scientist that thought it was likely to stand up, they all thought it was fascinating to contemplate the consequences if it did)

    That said, in 60 ns light travels about 60 ft. (18.5 m)   In an optical fiber it travels a little slower but not that much, so it is hard to see that by loosening the connection a few turns this effect shows up.  As a result, the only rational conclusion is that there is a massive conspiracy, possibly because the folks at CERN were growing jealous over all the attention climate scientists were garnering.  In retrospect it is clear that earlier attempts at seeding a controversy were made through a collusion with Dan Brown, but that flopped because the movie sucked.

    • You funny.
      In fiber (presumably singlemode) that’s about 12 m….so obviously not accounted for in terms of actual distance by a fiber misalignment.

      More likely the misalignment produced an air-gap etalon, introducing a significant group delay at the wavelength they were using.  But if that’s the case I’m a little surprised they didn’t notice a lot of dispersion in the pulse right off the bat.

    • The movie didn’t suck at all.  But the rest of the rational explanation still holds.

  2. I’ve been following this issue since it came out, and frankly, it is FAR from settled. In fact the neutrinos may have been going FASTER than the original experiment concluded.

    While the connection in question MAY have resulted in timing the particles FASTER than they were actually going, the issues they’ve discovered with the oscillator may have in fact resulted in them being timed SLOWER than they were actually going.

    Without independent confirmation from MINOS et al. nothing has been settled at all.

    A scan of all the available data going back decades shows that from the moment we gained the capability to track neutrinos successfully, the data has ALWAYS suggested that neutrinos travel faster than light.

    It’s just that up until recently we didn’t have any 5-sigma results, (the bar we set for calling something an actual discovery ie reflecting odds suggesting there is less than 1 in 3.5 million that the result was produced by chance).

    Results from SN 1987A showed the neutrinos arrived five hours “too early” for example. The claim until now has been to suggest that the neutrinos would’ve left five hours earlier since they’re unaffected by gravity and can pass through standard matter quite easily. The claim is that they should’ve arrived five years earlier if they were really faster than light.

    However, since we didn’t have reliable equipment in place five years previous, it hardly seems proper to suggest that anything was debunked at all. It’s an explanation that was convenient, but no more than that.

    We know so little about neutrinos that really one would think we should hold off on any sort of declaration at all until we get more results.

    That said, my money is not only on neutrinos being faster than light, but that they consititute a portion of the explanation for the “dark matter” puzzle.

    It’s even possible that neutrinos are tachyons, and how interesting would that be given tachyons are supposed to be an imaginary construct!

    • I’m with you all the way, Phil.  Neutrinos, I have always believed, are the answer to everything.  Or at least something!

  3. And I have to say, I’m getting tired of the hyperbole concerning “time travel” and the supposed breakdown of causality.

    Faster than light neutrinos don’t neccesarily mean anything of the sort. In fact it’s a serious stretch. I know it’s really exciting to claim that, but really it just shows a weak understanding of causality and imagination run amok concerning time machines and the like.

    Even if neutrinos are tachyons moving backwards in time, it may in fact form a basis for explaining the mechanism of how standard matter moves “forward” in time, ie an action/reaction displacement that REINFORCES causality.

  4. Now let’s tighten up the connections on the computers running the climate models and see what happens…

  5. Teller said “Two paradoxes are better than one; they may even suggest a solution.”  Another paradox about neutrinos is that they always have spin left-handed relative to their momentum but, if they have mass, then coordinate systems exist, specific to each neutrino, in which its spin is right-handed.  I don’t see a connection to superluminal propagation, other than that both effects violate special relativity, but it might be profitable if better physicists than I am consider both paradoxes.

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