Q: CERN’s faster than light neutrino thing: WTF?

Physicist: The story here is that CERN has been generating neutrinos, firing them 730km, to a detector in Gran Sasso, Italy, and those neutrinos have been consistently (so far as their instruments say) arriving 60 ns (0.00000006 seconds) earlier than they should.

These sorts of things crop up every few months, with varying credibility, but the credibility of this group is higher than most.  Faster than light claims have always (so far…) turned out to be a hoax, or a misunderstanding, or an error.

In this case it’s very likely to be an error.  When you’re talking about neutrinos you’re usually talking about just a couple of data points.  You generate a fantastic number in beam-form somewhere, fire it many times through the Earth at a detector far away and, with luck, you’ll detect one.

There are a lot of ways for a 60 nanosecond or 60 foot (light speed is about 1 foot per nanosecond) error to creep into an experiment involving a beam of “ghost particles” traveling 730km, from CERN to Gran Sasso, that produces no more than one or two data points at a time.

The neutrino beam generated at CERN is passed through the Earth and detected in Italy. Neutrinos are hard to detect because they barely interact with matter at all. Hence the whole "don't worry about the Earth being in the way" thing.

This is news firstly, I suspect, because everybody hates the light-speed cap.  Ever since 1905, when Einstein did his big, fancy “you can’t go faster than light” paper, there has been an unending tide of people coming up with ideas for moving faster than light.  Every single one has utterly failed, but the point is that the cap has a way of getting under everyone’s skin.

Human nature: If you tell someone they can't travel faster than light, then suddenly that's all they've ever wanted to do.

But mostly this is news because special relativity (which immediately implies the light speed cap) has been verified thousands and thousands of times in the last hundred and six years.

If you were to hear “scientists find that mustachioed men tend to ride unicycles more often than their clean-shaven brethren” you wouldn’t think twice about it (well, maybe twice), because there isn’t a towering monolith of evidence to the contrary.  You might wonder why they bothered looking into it, but whatever.

At the other end of the spectrum is relativity, which is really what’s at stake.  It is so well tested, and so well verified, that it has become the yardstick against which other physical theories are measured.  Often you can hear physicists laughing (cackling) at other physicists and saying things like “… and their scalar field wasn’t even Lorentz invariant!” (translation: “their thing violates relativity”).  Every single time anyone has ever made the claim that they have evidence that there’s something wrong with relativity, they’ve turned out to be wrong.

Unlike the sound barrier or the 4-minute mile, which were thought to be impossible merely because they were very difficult, the speed of light is inexorably tied up in the nature of existence, and matter, and time, and all that falderal.

So the reaction of most physicists to the CERN faster-than-light fiasco is: “wow… they really messed something up”.  In fact, the physicists at CERN (being physicists themselves) published the results not so much to say “hey, look what we did” so much as “fellow dudes and dudets… we really messed something up”.

If it’s a real discovery we should be extremely interested!  But, don’t hold your breath.

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28 Responses to Q: CERN’s faster than light neutrino thing: WTF?

  1. Clueless says:

    In your FTL you use light cones to illustrate how time travel could come about by exceeding the speed of light. In the unlikely event that the neutrino story is confirmed it would still be travelling upwards, and so presumably could not violate causality. Correct me if I’m wrong but travelling at right angles (spacewards with zero time) would seem to imply infinite speed (at least in the frame of the traveller), and travelling ‘downwards’ (or backwards in time ) would mean either mean going faster still(!) and not departing but arriving (which is consistent with entropy and the arrow of time) with a (random?) departure time some time before. The consequence is awesome and unnerving, but is the the premise sound? Would infinite velocity be necessary?

  2. qwert says:

    What is the meaning of the experiments showing that light moves through cesium vapor quicker than it does through a vacuum?


  3. The Physicist The Physicist says:

    Lightspeed is probably the best way to define “infinite speed”. The difference between something traveling faster than light, or teleporting, or going back in time and being in several places at once is (surprisingly) just a matter of perspective. This came up in a recent post.

  4. Pasquale Michael Ferrillo says:

    Some day, some physically intuitive physicist (I’m not one of those) will realize that mass-less particles are nonsensical. As are physical singularities. These are artifacts of mathematics. And one not need ‘overthrow’ special relativity in order to do away with these. If the set of all velocities is not closed, but open, with a supremum slightly greater than the speed of light, or, if the recent neutrino results are verified, slightly greater than the neutrino speed, then we at once remove the special relativity singularity, and allow both photons and neutrinos to have mass. Then we could consider possible models for these entities. Take light for instance. A dipole, perhaps composed of an n-bit and a p-bit (perhaps sub-multiples of the negative and positive electric charges), spinning (in our reference frame, tumbling in it’s) in it’s plane of polarization might do the trick. Or maybe a quadrapole or hexapole, etc. will do it. Carry on physicists.

  5. Will says:

    A lot of physics, especially advanced and theoretical physics, sounds silly and nonsensical at first (and some of it continues to sound like utter nonsense even after you understand it properly). Just because it seems nonsensical doesn’t mean it’s actually wrong. After all, there’s no particular reason why the universe has to make intuitive sense to the human brain.

  6. Jeroen Versteeg says:

    I have a question related to this whole neutrino vs. light speed stuff. I understand that any particle that has mass cannot ever travel at the speed of light. I also learned that any particle without mass must travel at the speed of light.

    What I don’t get is why neutrinos always travel at almost the speed of light. Why do a never read about slow neutrinos? Do the decay events they originate from always “try to” put as much leftover energy as possible into the neutrinos’ kinetic energy?

  7. Jason says:

    Jeroen: Because neutrinos are so lightweight that any energy will send them traveling very fast. They are some 1/1000 of the mass of an electron. And it is hard to slow them down since they don’t interact much with other matter.

  8. Jason says:

    Correction: Neutrinos weigh about 1/1,000,000 the mass of an electron

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  10. Will says:

    Basically, neutrinos weigh so little and interact with matter so weakly that even tiny amounts of energy will send them hurtling off at near-lightspeed.

  11. Darshan says:

    I just have one small query. They said its 60ns earlier. But my problem is how did they measure time so accurately? I know there are atomic clocks nowadays that have great precision but still allows inaccuracy. The atomic clocks are also mainly owned by governments etc so I am not sure if cern has one. One more thing is, how did they relay the message across that the particle has being sent? Our main way of sending messages is via EMWaves which follows the speed of light so how did they go across before speed of light?

    It takes light 2.4ms to travel the distance they sent the neutrinos to. Even if they calculated this precisely and allowed for some inaccuracy by adding this time gap they could still have it wrong. The area where thy could probably go wrong is to ignore decrease in speed of light through different materials. I am really not sure how they measured the time but would love if someone could send me the experiment notes I would love to go through it.

  12. The Physicist The Physicist says:

    The paper CERN released is here.
    The clocks they’re working with are far more accurate than 1ns. Rather than signaling each other about when the beam was generated and when it was detected, they just told each other the time on their clock after the fact. If they had wanted to, with their clocks in place, they could have conducted the experiment by mail.

  13. Will says:

    It would be kind of pointless to be conducting experiments like this if you didn’t have clocks with that level of accuracy really.

  14. David Brown says:

    Is the OPERA neutrino anomaly merely an experimental error? The OPERA team has some of the best physicists in Europe and spent 6 months attempting to shake bugs out of the experiment. Has the OPERA team empirically confirmed string theory? I have suggested:
    MILGROM DENIAL HYPOTHESIS: The main problem with string theory is that string theorists fail to realize that Milgrom is the Kepler of modern cosmology.
    Why do the multitudes of astrophysicists disagree with me? They say that the equivalence principle has been verified to 14 decimal places of accuracy. I say that the equivalence principle has been verifies to 14 decimal places of accuracy for real mass-energy but NOT for virtual mass-energy. It is possible that virtual mass-energy always obeys the equivalence principle but this has not been empirically proven.
    Define the Rañada-Milgrom effect as replacing the -1/2 in the standard form of Einstein’s field equations by -1/2 + dark-matter-compensation-constant, where this constant is approximately sqrt((60±10)/4) * 10^-5 as suggested by the Pioneer anomaly.
    http://www.astro.umd.edu/~ssm/mond The MOND pages (McGaugh)
    http://www.astro.uni-bonn.de/~pavel/kroupa_cosmology.html Pavel Kroupa: Dark Matter, Cosmology and Progress
    Why is the OPERA anomaly precisely in the range of the Rañada-Milgrom effect?

  15. Robert Poet says:

    Two clocks are started together at Cern.
    One is taken to Grand Sasso.
    The surface rotational speed at Grand Sasso is greater than that at Cern due to the lower latitude.
    I estimate the difference to be 0.021546Km / sec.
    Altering the speed of light by this amount reduces the transit time of the neutrinos by approx 17.4 secs.
    But a more accurate correction may need the gamma formula 1/(root(1-Vsquared/Csquared) where V= C+0.021546.
    Unfortunately this is beyond by mathematical ability to evaluate.

    Robert Poet 16/11/2011

  16. Sabeeh says:

    I find that scientists live with ‘tinted vision’. I studied physics at degree level and one of my observations of the clever professors was that they tend to develop theories based on certain assumptions (that they do not question because these assumptions came from a genius of old), then use mathematics to try and prove the theory. As long as they manage to ‘prove’ it the consequences with implication of ludicrous scenarios simply do not matter. Example of ludicrous consequences – super strings, parallel universes etc…
    Then even the greats (like Hawking) have to eat humble pie when they actually got it completely wrong (but managed to convince the community they were right !).
    Please use OBSERVATION as your key tool to understanding, then come up with theories to try to explain what you saw ! (like they used to do in the good old days).

    Recently we have the faster than light speed travel observed. Once it is verified (I think it will be) then we need to go out and try to explain it.
    The variable speed of light theory is also gaining ground (and why not ! it certainly makes more sense than a constant c, with its contracting/stretching ‘spacetime’).
    That’s my other gripe; things get fantastical and yet nobody says ‘hang on guys’ what we are saying does not even make sense and how on earth can we explain it to the lay person !
    You are turning science into a ‘belief system’ because only a handful of people supposedly understand it (though they still can’t explain it to anyone else !), so the rest of us mere mortals have to take it on ‘faith’ that there are these fantastical ‘wormholes’, ‘parallel universes’, ‘strings’ etc…

  17. Yoron says:

    I liked this post. It’s quite balanced and points out that we have a lot of experiments validating light as a constant and Relativity per se. One of the statements there is that mass won’t go FTL. And it makes sense to me.

    So to make neutrinos move FTL will need more evidence than just this test. There are a lot of things that can have an importance in this ‘result’, and the whole thing is incredibly close to the edge of what we can measure today. I don’t expect it to be FTL myself, and until I’ve seen more, and differently made, tests I will continue to doubt it.

    With QM as the new ‘star’ many seems to find Relativity a irritation. A lot of the things Relativity defines is extremely hard to measure, as for example where time dilations and Lorentz contractions stop making sense. Myself I expect them to be at a QM scale. And that means that QM needs to take it into consideration, if they want their theory’s to fit Relativity. Finding Relativity not to fit, as with gravity, QM may be a the simple choice, but I doubt it.

  18. I haven’t read the results but I assume they adjust for the rotation of the Earth and for the fact that there is a special relativity time dilation effect due to the relative speeds of rotation of the emitter and detector and (possibly) a gravitational time dilation effect also?

    An unexpected geogravitational pulse at one end or the other might cause a time shift but I suspect that the effect would be much smaller than 60nS unless th epulse was huge.

  19. Another thought… speaking as a Chartered Minerals Surveyor (and a methematician) with experience of geodetic surveying techniques I think at least part of the error will be in the calculation of the straight line distance between emitter and detector to an accuracy of better than 0.3m in 730 km when the distance has been surveyed around the curved surface of the Earth)

  20. asdfasdf says:

    Hasn’t there been a recent development about this? I read in a newspaper that they figured out what the mistake was. unfortunately the newspaper was not in english, so I didn’t really understand it.

  21. The Physicist The Physicist says:

    A couple problems have been found, including a now infamous “loose wire”, but I’m waiting to see if they have everything sorted out when they start up again in May before posting anything about it.

  22. Pingback: Q: Will CERN awaken the Elder Gods? | Ask a Mathematician / Ask a Physicist

  23. Ron says:

    When in May???

  24. themoron says:

    what’s your take on the “tachyons”?

  25. themoron says:

    do you think they can actually travel faster than the speed of light?

  26. Leonardo Rubino says:

    There was a lack of high school physics knowledge:


  27. Xerenarcy says:

    no mention of the revised FTL measure?

    last i checked they revised it to approx c + 6ns. but how this was done i’m a bit disappointed – the 6ns is the intersection of two different results, from two different observers: one reporting subluminal speeds and another reporting superluminal speeds. specifically there are two peaks of data, who’s margins of error meet in agreement at +6ns.

    interesting too is that the subluminal measurement used detectors with known position, while the superluminal measurement did not, indicating that the two measurements are, effectively, from two different reference frames (one that is position-like and another that is momentum-like). if these are indeed two different reference frames, then we have an indication of asymmetry of either mass or time depending on what you measure and how.

    even more interesting is that the higgs boson discovery appears to be subject to a similar dismissal of asymmetry – the 125 figure, again, has been averaged from two independent readings of 124 and 126. the circumstances of those figures are not as simple as the neutrino case, but besides the point…

    it seems like there is a good deal of denial going on that relativity may not be entirely correct. it does a very good job and (so far) nothing else works as well on the same scales, but relativity, in how it is used and what it is founded on, might be flawed. if it is then these experiments operating on absurd scales (smallest mass, fastest speed) should come up with the same discrepancies relativity is struggling with elsewhere (black holes for instance, big bang singularity, etc). and so far that is what i see happening (neutrino and higgs, metric changing sign, entanglement subtleties when approaching uncertainty limits with and without relativistic conditions, MWI, etc)

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