Lightspeed neutrinos: you read it first on WEIT!

by Matthew Cobb

Alert WEIT reader Occam refers to the announcement yesterday from the ICARUS team working at CERN that if those pesky OPERA neutrinos had indeed gone faster than light, then they should have shown a loss of energy. They didn’t, so they didn’t. You can read two rather more worked out arguments, one  experimental (here) and another that is theoretical (here).

What’s interesting is that Occam points out that our very own Torbjorn Larsson pointed this out in a discussion on WEIT: “-There is no Cherenkov radiation as expected for particles traveling faster than surrounding photons travel.”

As Occam points out, this is precisely the point made by Cohen & Glashow theoretically, and confirmed by M. Antonello et al. experimentally.

WEIT: it’s all you need!


  1. Posted November 22, 2011 at 7:18 am | Permalink

    I had already read this, but of course it isn’t really much of an explanation to use a weaker scientific theory to prove that the stronger scientific theory isn’t in error, is it?

    I’m looking forward to them identifying the error.

    • Reginald Selkirk
      Posted November 22, 2011 at 7:25 am | Permalink

      I’m looking forward to someone identifying the error for them.

    • J
      Posted November 22, 2011 at 8:20 am | Permalink

      I don’t think this is necessarily true, as the “stronger” theory has to reproduce the “weaker” one to some extent, and since we know that both the Standard Model (of particle physics, so the ability of the neutrino to emit a neutral Z boson which can then decay to an electron-positron pair) & special relativity are remarkably successful to many orders of magnitude precision, we can’t necessarily throw away predictions that follow from them to probe anomalous results.

      Having said that, you’re quite right – if the neutrinos are essentially taking a shortcut through another dimension then (as far as I’m aware – I don’t know much about models with extra dimensions eg. string theory) there’s no reason to assume they would radiate in this manner (though nor would they be superluminal in this case).

      Having said THAT… sadly it’s more likely that an error is to blame (but I’d like to be wrong!)

      • Posted November 23, 2011 at 2:47 am | Permalink

        I worded my response incorrectly. What I should have said is…

        “We cannot use a scientific theory to disprove an observed fact”

    • Posted November 22, 2011 at 11:41 am | Permalink

      Lots of smart, motivated people are digging, but you would think rationalists would not be allowed to dismiss the experimental result until and unless. That is, “justified true belief” has to actually be justified, after all. Handwaving about effects that have never been observed (Cohen-Glashow radiation) isn’t going to do it.

      You are aware that they redid the experiment using very short bursts, right? So they’ve eliminated the suggestion that it was an effect of averaging over a distorted pulse shape.

  2. Hempenstein
    Posted November 22, 2011 at 7:20 am | Permalink

    WEIT: it’s all you need!

    Money back if not satisfied.

    • daveau
      Posted November 22, 2011 at 8:41 am | Permalink

      Double your money back! On me.

      • Strider
        Posted November 22, 2011 at 10:32 am | Permalink

        I’ll take some money, too!

  3. NewEnglandBob
    Posted November 22, 2011 at 7:20 am | Permalink

    “WEIT: it’s all you need!”

    It even has culinary and sartorial (cowboy boots) advice.

  4. TJR
    Posted November 22, 2011 at 7:30 am | Permalink

    I thought love was all you needed?

    • Blah
      Posted November 22, 2011 at 8:24 am | Permalink

      Hysterical Sex is all you need!

    • TrineBM
      Posted November 22, 2011 at 2:16 pm | Permalink

      Slogan: WEIT! Love is all you need

  5. Posted November 22, 2011 at 7:32 am | Permalink

    Don’t particles need a charge to emit Cherenkov radiation, and isn’t a neutrino not charged?

    • J
      Posted November 22, 2011 at 8:01 am | Permalink

      It does indeed, so Cohen & Glashow in their paper (the theoretical one) discuss “analogs to Cherenkov radiation”, with the main one being in the form of an electron-positron pair resulting from the decay of a Z boson (no charge) emitted by the neutrino.

  6. Posted November 22, 2011 at 7:37 am | Permalink

    This matter won’t be solved, however, until we get an explanation for the time discrepancy. After all, it’s conceivable that, contrary to all our understanding, the neutrinos are faster than light and don’t lose energy.

    No, I don’t think that’s the case. At this point, I’d bet at least a dinner that this will turn out to be an experimental error. But the experiment’s results are still anomalous and unexplained.

    Asimov put it best: “The most exciting phrase to hear in science, the one that heralds the new discoveries, is not ‘Eureka!’ (I found it) but ‘That’s funny…’” I’m pretty confident that we won’t get faster-than-lignt neutrinos out of this one, but we should get some sort of exciting new discovery. I’ll bet dessert on that one.



    • daveau
      Posted November 22, 2011 at 8:46 am | Permalink

      I’m with Ben on this. I think there will be something very interesting learned here, even if it isn’t FTL travel.

      • Posted November 22, 2011 at 8:59 am | Permalink

        And it doesn’t even have to revolutionize our understanding of physics to be “very interesting.” Even if it’s a mistrake, it’s a very, very, very subtle one and understanding that mistrake will have big implications for all sorts of other experiments, past, present, and future.

        The OPERA crowd deserves nothing but kudos. They’re making for some really interesting times, in the best possible way. No matter how the chips ultimately land, this experiment is a smashing success (if you’ll excuse me).



    • eric
      Posted November 22, 2011 at 9:59 am | Permalink

      I agree. I remember back when Kamiokande was getting different solar neutrino results from the other detectors, and they finally figured out that (these) neutrinos oscillate.

      Classic example of an interesting and unexpected result…which didn’t radically overturn physics…and which involved neutrinos. :)

  7. Lurker111
    Posted November 22, 2011 at 8:00 am | Permalink

    What others have said: IF the neutrinos are really toodling along at > c, THEN they’re already violating relativity and the Standard Model and its corollaries. Thus, you can’t use relativity or Standard Model logic to disprove them. So the bottom line is, is the measurement correct or not?

    My money’s still on the “or not.”

  8. Tulse
    Posted November 22, 2011 at 8:21 am | Permalink

    I think this is an excellent example of why empiricism is at the root of science. Ultimately theory can’t trump objective observed results — it can suggest that those results are suspect, and point to ways to test those suspicions, but reality trumps theory every time. The job of theory is to model reality, and if our measure of reality doesn’t conform to theory, then it’s theory that has to change.

    That said, I’d be very surprised if these results stand.

  9. prasad
    Posted November 22, 2011 at 8:35 am | Permalink

    Matthew Strassler (physics prof at Rutgers, and a pretty good particle physics communicator – and rumor monger – this year) explains why the ICARUS argument isn’t conclusive:

    One problem with their argument is, OPERA itself makes an energy measurement of its neutrinos (in fact they bin it to see if they can find an energy dependent speed – they don’t) which straightforwardly shows their neutrinos, if they’re superluminal, nevertheless don’t undergo this Cherenkov like mechanism. Given this, surely ICARUS is saying something in agreement with OPERA, not in contradiction. I think the paper is basically lightspeed party crashing on their part.

  10. MKray
    Posted November 22, 2011 at 8:45 am | Permalink

    Look at arXiv:1110.0989 on the preprint server (Googling arXiv:1110.0989 will get it)
    for what seems to me a nice explanation without dumping SR:
    Abstract: We argue that the neutrino advance of time observed in MINOS and OPERA experiments can be explained in the framework of the standard relativistic quantum theory as a manifestation of the large effective transverse size of the eigenmass neutrino wavepackets.

    I’ve seen no criticism of this. One author is a sometime spokesman for the Opera team, and a member of Group on Opera team who have dissented.

  11. Torbjorn Larsson, OM
    Posted November 22, 2011 at 1:25 pm | Permalink

    Thank you!

    But we have the causality in reverse, because I nicked that hypothesis from Cohen & Glashow and didn’t attribute it at the time.

    [As I reconstruct it I felt that it was among the circulating ideas and TL;DW (Too Long; Didn't Write).]

    Which maybe makes these ftl neutrinos a little bit more believable …

    WEIT: it’s all you need!

    That seems very, um, likable.

    I keed, I keed! It is a good blog.

    • Ichthyic
      Posted November 22, 2011 at 2:27 pm | Permalink

      It is a good blog.

      oh, you’ve gone and done it now!

  12. Posted November 22, 2011 at 2:07 pm | Permalink

    I am a complete no-nothing in physics, but I find I still want to ask a question which has been puzzling me.

    Einstein proposed special relativity in 1905. Neutrinos were first postulated in 1930. How did Einstein know that the speed of light would be a limiting factor on a particle which was at the time completely unknown?

    Please feel free to post gales of laughter and tell me how obvious the answer is.


    • MadScientist
      Posted November 22, 2011 at 2:22 pm | Permalink

      Einstein based his special relativity on the apparent behavior of light. Neutrinos were predicted ~1930 to avoid a violation of the conservation rules; the energy and mass were predicted and there was nothing to suggest that they might travel faster than light. Neutrinos have been observed over the past few decades and until now there has been no evidence that they travel faster than light in a vacuum. So, Einstein’s SR has held up over all that time – it’s not that he was psychic, he just happened to propose something which worked very well and which has still never been contradicted.

      • Posted November 22, 2011 at 5:56 pm | Permalink

        You touch on something else which I find puzzling. There’s a lot of talk about the speed of light through a vacuum, yet CERN is an underground facility on the Swiss/French border, and it is sending neutrinos to an underground facility in Italy. What is the speed of light through rock? I had always assumed 0 because it’s always been very dark when I have been underground without my own torch.

        • J
          Posted November 23, 2011 at 1:34 am | Permalink

          The speed of light in a vacuum is a fundamental speed limit (usually called c) that, according to Einstein’s Special Relativity, can’t be reached & certainly not exceeded by particles with mass. As you accelerate them they acquire more energy, which makes them behave as if they were a bit heavier & so need more energy to go a little bit faster & so now they’re even heavier (and so on).
          Beating the speed of light in a material isn’t anything new – look up Cherenkov radiation on Wikipedia. Light through a material (that it can pass through, so not rock) travels at c/n where n is the refractive index of the material. But for the neutrinos to appear as if they’re beating they’re exceeding c, speed of light in a vacuum, then this is violating that principle from SR.

          • Posted November 23, 2011 at 4:22 am | Permalink

            Thank you. That has actually helped my understanding of what is going on here.

          • Chris Booth
            Posted November 27, 2011 at 8:55 am | Permalink

            Excellent comment, J. Succinct and clear. I, too, much appreciate it. Thank you.

    • David
      Posted November 22, 2011 at 2:29 pm | Permalink

      I could be wrong, but I believe the theory is that nothing can break the light speed barrier or anything with mass can not go faster than light.

      Although recently I have read that theoretically some particles can go fvaster than light as long as they never go slower than light. That makes my head hurt though.

      • Posted November 22, 2011 at 5:59 pm | Permalink

        Yes, definitely in head hurting territory. Mine seems to hurt most of the time though.

  13. MadScientist
    Posted November 22, 2011 at 2:13 pm | Permalink

    Surely there was Cherenkov radiation (after all the neutrino will in fact be traveling faster than light through the bulk of its path). I haven’t read the articles yet, but I would guess the radiation produced is not consistent with superluminal neutrinos. I was reading Ethan Siegel’s post which included a brief mention of a 25ns jitter in the clocks used at OPERA. Any similar issues with the timing at CERN would make the superluminal claim rather dubious. Add to that the fact that I’m not convinced the physical distance involved is known well enough.

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  1. [...] Neutrinos the “faster than light” neutrinos did NOT exhibit the type of radiation that they were expected to exhibit. So, where was the error? If nothing else, we learned something from all of this. [...]

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