Faster-Than-Light Neutrinos?

By Sean Carroll | September 23, 2011 11:09 am

Probably not. But maybe! Or in other words: science as usual.

For the three of you reading this who haven’t yet heard about it, the OPERA experiment in Italy recently announced a genuinely surprising result. They create a beam of muon neutrinos at CERN in Geneva, point them under the Alps (through which they zip largely unimpeded, because that’s what neutrinos do), and then detect a few of them in the Gran Sasso underground laboratory 732 kilometers away. The whole thing is timed by stopwatch (or the modern high-tech version thereof, using GPS-synchronized clocks), and you solve for the velocity by dividing distance by time. And the answer they get is: just a teensy bit faster than the speed of light, by about a factor of 10-5. Here’s the technical paper, which already lists 20 links to blogs and news reports.

The things you need to know about this result are:

  • It’s enormously interesting if it’s right.
  • It’s probably not right.

By the latter point I don’t mean to impugn the abilities or honesty of the experimenters, who are by all accounts top-notch people trying to do something very difficult. It’s just a very difficult experiment, and given that the result is so completely contrary to our expectations, it’s much easier at this point to believe there is a hidden glitch than to take it at face value. All that would instantly change, of course, if it were independently verified by another experiment; at that point the gleeful jumping up and down will justifiably commence.

This isn’t one of those annoying “three-sigma” results that sits at the tantalizing boundary of statistical significance. The OPERA folks are claiming a six-sigma deviation from the speed of light. But that doesn’t mean it’s overwhelmingly likely that the result is real; it just means it’s overwhelmingly unlikely that the result is simply a statistical fluctuation. There is another looming source of possible error: a “systematic effect,” i.e. some unknown miscalibration somewhere in the experiment or analysis pipeline. (If you are measuring something incorrectly, it doesn’t matter that you measure it very carefully.) In particular, the mismatch between the expected and observed timing amounts to tens of nanoseconds; but any individual “event” takes the form of a pulse that is spread out over thousands of nanoseconds. Extracting the signal is a matter of using statistics over many such events — a tricky business.

The experimenters and their colleagues at other experiments know this perfectly well, of course. As Adrian Cho reports in Science, OPERA’s spokesperson Antonio Ereditato is quick to deny that they have overturned Einstein. “I would never say that… We are forced to say something. We could not sweep it under the carpet because that would be dishonest.” Now there’s a careful and honest scientist for you, I wish we were all so precise and candid. Cho also quotes Chang Kee Jung, a physicist not on the experiment, as saying, “I wouldn’t bet my wife and kids [that the result will go away] because they’d get mad. But I’d bet my house.” A careful and honest husband and father.

Scientists do difficult experiments all the time, of course, and yet we believe their results. That’s simply because it’s proper to be extra skeptical when the results fly in the face of our expectations: extraordinary claims require extraordinary evidence, as someone once paraphrased Bayes’s Theorem. When the supernova results in 1998 suggested that the universe is accelerating, most cosmologists hopped on board fairly quickly, both because we had a simple theoretical model in hand (the cosmological constant) and because the result helped explain several other nagging observational problems (such as the age of the universe). Here that’s not quite true, although we should at least mention that Fermilab’s MINOS experiment also saw evidence for faster-than-light neutrinos, albeit at a woefully insignificant level. More relevant is the fact that we have completely independent indications that neutrinos do travel at the speed of light, from Supernova 1987A. If the OPERA results are naively taken at face value, the SN 87A should have arrived a couple of years before we saw the explosion using good old-fashioned photons. But perhaps we should resist being naive; the SN 87A events were electron neutrinos, not muon neutrinos, and they were at substantially lower energies. If neutrinos do violate the light barrier, it’s completely consistent to imagine that they do so in an energy-dependent way, so the comparison is subtle.

Which brings up a crucial point: if this result is true (which is always a possibility), it is much more surprising than the acceleration of the universe, but it’s not as if we don’t already have ways to explain it. The most straightforward idea is to violate Lorentz invariance, a strategy of which I’m quite personally fond (although I’ve never applied the idea to neutrino physics). Lorentz invariance says that everyone measures the speed of light to be the same; if you violate it, it’s easy enough to imagine that someone (like, say, a neutrino) measures something different. Once you buy into that idea, neutrinos are an interesting place to apply the idea, since our constraints on their properties are relatively weak. It’s an interesting enough topic that there are review articles, and even a Wikipedia page on the idea.

And there are more way-out possibilities. Graininess in spacetime from quantum gravity might affect the propagation of nearly-massless particles; extra dimensions might provide a shortcut through space. This experimental result will probably give a boost to theorists thinking about these kinds of things, as well it should — there’s nothing disreputable about trying to come up with models that fit new data. But it’s still a long shot at this time. I hate to keep saying it over and over in this era of tantalizing-but-not-yet-definitive experimental results, but: stay tuned.

A few of the countless good blog posts on this topic:

CATEGORIZED UNDER: arxiv, Science, Top Posts
  • Jan de Wit

    Were people even looking for electron neutrinos ‘a couple of years’ before SN 87A?

  • Jim Cliborn

    Good blog! Keep us informed as understanding progresses. You are a good, clear thinker and writer, don’t give us up!!

  • Lab Lemming

    Are there any astrophysical sources for this kind of neutrino, or are we stuck with terrestrial experiments? Skimming the papers suggests that aiming this thing at a detector in the pacific or antarctica would be very difficult.

    Anyway, my geologic interpretation is that they have the world’s most expensive earthquake detector.

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  • Ellipsis

    very small correction — most, if not all, of the 24 neutrinos that were detected from SN1987A were electron antineutrinos, not electron neutrinos. (It is possible that 3 or 4 of the 11 events detected in the Super-K detector in Japan from SN1987A were neutrinos rather than antineutrinos, but this was far from clear.)

    (and yes, if neutrinos are Majorana, electron neutrinos and electron antineutrinos are just different helicity states of the same particle, but not if they are pure Dirac, etc etc etc. And I would personally bet about 1000:1 that the OPERA result is due to a systematic effect [but not 10000:1].)

  • Jorge Laris

    Or maybe Speed light is increasing over time… Ok is very improbable.

  • Raimo Kangasniemi

    I have to a bit sceptical about our ability to detect neutrinos from the 1987 supernova with the 1983 equipment. The amount of neutrinos caught in 1987 wasn’t terribly high even then.

  • MrCompletely

    a nicely nuanced and non-dismissive interpretation of a nicely nuanced and non-hyperbolic announcement that has, predictably but unfortunately, resulted in a comically un-nuanced (perhaps even anti-nuanced) avalanche of headlines. it’s nice that we don’t have to dig too far for sobriety.

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  • Mike Martin

    So, the only conclusion here is that faster than light neutrinos are expected but not probably? What about the implications with the mass of the Neutrinos. Can we call them tacchions?

  • Brian Lacki

    Lab Lemming,

    There probably are, but we haven’t detected them yet.

    The way to make astrophysical neutrinos is basically to take a high energy proton or neutron and let it crash into something — either another nucleus or into a photon. If the collision is high enough energy (more than a few hundred MeV in the center of momentum frame), pions (and more exotic mesons) will be created. Those decay into muon and electron neutrinos and other particles, and muon neutrinos are what this experiment were using. (Also, neutrino oscillations I think will convert other neutrinos into muon neutrinos on astrophysical scales.)

    The problem is that neutrinos are also produced by cosmic rays hitting the upper atmosphere. These atmospheric neutrinos drown out astrophysical neutrino at GeV scales, at which this experiment worked. It’s only at high energies (TeV to PeV or higher) that you can look for astrophysical neutrinos with IceCube and other neutrino telescopes. If we think the speed of neutrinos increases with energy, then timing TeV neutrinos will be a more powerful experiment than timing GeV neutrinos.

    Of course, with this kind of experiment, you also want to do timing: a steady source of TeV-PeV neutrinos isn’t enough. Gamma-ray bursts might be sources of high energy neutrinos, and since they don’t last long, you could time the difference between when the neutrinos and the photons arrive. They’re also very far away, billions of light years, so any difference in speed will have a long time to accumulate into a large delay. The only problem may be if the delay becomes too long — if the neutrinos arrive years and years before the photons.

    But at the moment, we don’t know that gamma-ray bursts (or any other transient source) emit high energy neutrinos for sure: the Sun and Supernova 1987A are the only extraterrestrial sources of neutrinos detected so far.

  • Doug

    Re #8: We did detect those neutrinos at a time when neutrinos moving close to the speed of light would have been expected to arrive from SN 1987A. Even if 1983 detectors wouldn’t have been able to detect it, you would still have to explain why an unusual neutrino burst consistent with a supernova explosion was detected at just the right time to fool us into thinking GR is correct for this supernova.

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  • Gene

    So if its true we have to give up Lorentz invariacne or causality? … I hate it either way.

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  • Rick

    “So if its true we have to give up Lorentz invariance or causality? … I hate it either way.”

    I don’t think we’ll have to give up either when this is sorted out. But, if we have to, I vote for giving up Lorentz invariance.

    In the meantime, this is the best approach:

  • Gavin Flower

    Has anyone considered that going through matter, might cause these neutrinos to go a bit faster than light? If that is correct, then comparing this experiment to neutrinos travelling through space may not be valid!

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  • jimthompson

    I’m rather disappointed with the response of theorists to this paper: isn’t it a theorist’s JOB to immediately start writing papers and talking about all the implications if this result IS correct? Not a peep , that I’ve seen, about what OTHER experiments might or might not see etc. etc. The fact that the paper is probably wrong has NEVER seemed to stop theorists in the past……After all, this paper is probably NOT going to be refuted for at least a week, perhaps much longer.

  • Ranger Dan

    Did they try putting new batteries in their calculator?

  • Torbjörn Larsson, OM

    So … has everybody caught where they goofed yet?*

    It is an easy one. According to the paper the distance measurement procedure use the geodetic distance in the ETRF2000 (ITRF2000) system as given by some standard routine. The european GPS ITRF2000 system is used for geodesy, navigation, et cetera and is conveniently based on the geode.

    I get the difference between measuring distance along an Earth radius perfect sphere (roughly the geode) and measuring the distance of travel, for neutrinos the chord through the Earth, as 22 m over 730 km. A near light speed beam would appear to arrive ~ 60 ns early, give or take.

    Of course, they have had a whole team on this for 2 years, so it is unlikely they goofed. But it is at least possible. I read the paper, and I don’t see the explicit conversion between the geodesic distance and the travel distance anywhere.

    Unfortunately the technical details of the system and the routine used to give distance from position is too much to check this quickly. But the difference is a curious coincidence with the discrepancy against well established relativity.

    * Extraordinary claims need extraordinary evidence. Other outstanding concerns are:

    1. This needs to be repeated.

    2. It is not a clear photon vs neutrino race. Physicist Ellis and others here noted that the time differential for the supernova SN 1987A was a few hours, but at the distance of ~ 200 000 ly it should have been years if the suggested hypothesis would be correct.

    3. Analogous to the experiments where light waves seemingly travels faster than photon speed in vacuum, they don’t measure travel times of individual neutrinos but averages over a signal envelope. That must be carefully measured to establish that particles (or information, for that matter) travels faster than relativity allows.

    Especially since the neutrino beam oscillates between different kinds of particles!

  • Bruce Cohen (Speaker to Managers)

    Isn’t it true that in this context “giving up Lorentz invariance” means just for a few exceptions like muon neutrinos? As I understand it, current quantum physics is based on Special Relativity and there’s a lot of experimental evidence for that basis using many different particles of different masses. Anyone have a theory as to why most particles would be Lorentz invariant, and only one or few would not? And especially why one form of neutrino is and another is not (based on the Supernova 1987A observations).

    Of course there was a similar choice awhile back, when Bell showed (and Aspect and other experimenters proved) we’d have to give up either locality or causality, and most chose to give up locality.

  • JK Finn

    From the arxiv paper ( ):

    In terms of interactions in the detector, the νμ contamination is
    2.1%, while νe and νe contaminations are together smaller than 1%.

    Wasn’t there some interesting result last year about a possibly significant difference between the masses of νμ and νμ? If true, wouldn’t this be likely to distort the distribution of arrival detection enough to shift the calculated value?

    Still reading the paper, maybe it is mentioned there…

  • Paul

    jimthompson: actually, theorists have been writing papers about tachyonic neutrinos for years. There was some motivation from tritium decay experiments, where some data can be interpreted as the electron antineutrino having a slightly negative mass^2.

  • anon

    #22, you sure about that? i get km’s for the difference

  • Low Math, Meekly Interacting

    Cool! Thanks!

  • Clive Robinson

    Does c actually have to be the same as the speed of light that we can measure? Is it conceivable that photons have an extremely small rest mass, and so don’t travel exactly at c?

    I’m sure there’s a reason which I’ve forgotten about since my university physics days, particularly as no-one else seems to be suggesting it. I think it may mess up QED for instance, but is it absolutely inconceivable? I’d be grateful if someone could explain why this couldn’t possibly be what’s going on here.

  • scott gray

    There is a theory already out there to explain this result.

    Start here:

  • Pccitizen

    Interested observer here, not easily keeping up with things like this, but having lots of fun trying. BUT – I thought neutrinos were shown to have mass. How do they even travel at the speed of light? Or does that only apply to photons (electromagnetic radiation I guess). And one question above… if light travels slower in glass e.g., why wouldn’t neutrinos travel (at least microscopically) slower thru mass? Please don’t yell at me.

  • Nameless

    Re Doug #13: neutrinos propagate as mass eigenstates. It’s possible that there is one mass eigenstate with zero or very small positive mass-squared (which is the one that was observed on the day of SN1987A), and another eigenstate with negative mass-squared. Due to its nonzero mass, the second eigenstate could arrive long before 1987. Furthermore, negative-mass-squared neutrinos could be dispersed over a period of, say, a year, and be completely lost in background noise.

    Even saying that “the SN 87A should have arrived a couple of years before we saw the explosion” is not quite right, because we don’t know the dispersion relations (speed vs energy) for this weird neutrino.

    If what we have is a tachyonic/negative-mass-squared effect, (v-c)/c would scale as E^{-2}. That effect would get stronger as we go down the energy scale, and I’m pretty sure that it would’ve been detected by now. (It’s easy to calculate that OPERA-like neutrinos with 100 MeV energy would travel at twice the speed of light).

    On the other hand, if it is a Lorentz-violating effect, (v-c)/c would scale as some positive power of E, and the violating eigenstate could possibly get to Earth just before the well-behaved eigenstate. There is an article on arxiv (hep-ph/9712265) that claims that such a burst was seen by a neutrino detector in France about 5 hours ahead of the main bunch.

  • jimthompson

    @Paul nah, that doesn’t work as it’s not about THIS experiment. Nameless at #31 comes closer. My conclusion is that this result is so unlikely to hold up that even theorists can’t be bothered to probe the implications (though surely someone will prove me wrong, momentarily…)

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  • Brian137

    Thank you for discussing this, Sean. This thread doesn’t seem to contain the usual spate of insightful/provocative comments. Maybe we are mostly dazed and nonplussed. Oh well, “systematic error” has been a good horse so far. I’ll check back tomorrow.

  • Iain

    What would be the effect of photons ‘following’ the curvature of space and neutrino’s travelling in a truly straight line?

  • Andrew Hearin

    Suppose for argument’s sake that the result is sound. Do we really need Lorentz violation, or massive photons, or quantum gravitational interactions, in order to account for it? How does the effective index of refraction of the vacuum for photons compare to muon neutrinos? The sense of this effect is at least correct: electron/positron pairs pop out of the vacuum far more often than do muon/anti-muon pairs simply because electrons are 200 times lighter than muons. Moreover, the scattering cross-section of photons off of electrons is many orders of magnitude larger than that the scattering cross-section of a neutrino off of its associated lepton. So couldn’t this be accounted for by photons failing to travel on null geodesics in vacuum due to ordinary QED scattering events?

  • ursusmaritimus

    Why do you people care so much? Go have fun outside, maybe share a laugh with a real person before oblivion comes.

  • Sean

    Iain, for what it’s worth, the order of magnitude of an general-relativistic effects should be three or four orders of magnitude smaller than the claimed signal.

  • Julius Mazzarella

    Can anybody answer this question because I am not a scientist. I thought that as long as something does not accelerate faster than the speed of light it would not violate special relativity. If the particle starts out faster than light…would that still be a problem? Like Tachyons ( spelling?) ..theoretical particles that travel faster than light?

    How about the vacuum thing? I thought the speed of light constant was for a vacuum??

    How about this . Can special relativity handle something like. “Almost constant”..”give or take ” ? Sort of like trying to predict prime numbers, although they may exist you can only be so accurate( Riemann Hypothesis. )

  • sansar swaroop saxena

    it is only possible if muon nutrino is mass less particle but as it is a part of atom it may contribute sme mass possibly may be negligible or very less but einstein might had considered its presence but if its true then relativity fails………..

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  • Kevin

    Very cool, but I remain skeptical because of the size of the effect – if Lorentz invariance can be violated, is there any reason to think it would be… just ever so slightly violated? If neutrinos are truly not bound by the speed of light limit, then why not expect to see neutrinos moving convincingly faster than the speed of light rather than just barely measurably faster?

    Anyway, very interested in watching this unfold.

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  • Terry Newton

    IF this result is confirmed (and that’s a big IF), perhaps quantum tunneling may offer an explanation? Some experiments show propagation far in excess of C because tunneling is a position uncertainty thing, no space to go through (see arxiv 0204043v1). However causality is preserved, information has not been shown to travel faster than C. Tunneling is statistical, it takes an accumulation of events to reveal the information, thus any single event cannot carry information. What makes me think of tunneling is the scale seems about right – flash memory chips work by tunneling electrons through a tiny glass barrier using a few tens of volts of energy, enough to spread out the “jumping electrons” enough to cross the barrier, where they become trapped when the energy is lowered. In the neutrino experiment, there is a 200mhz component, that would be a wavelength of about 5 feet, or cresting every 2 1/2 feet. The energies in the experiment are are far higher than what takes place in a thumb drive, so to my feeble brain seems like the average tunneling distance, if that’s what’s going on, combined with the high frequency of oscillation, might be enough to account for the discrepancy. Maybe, big shot in the dark. The main point is just because the statistical average velocity of something exceeds C, doesn’t mean that information can exceed C. If tunneling is at play here (or any phenomena involving quantum uncertainty), I’d expect the spread of detection events to increase as distance increases, and over large distances would be indistinguishable from noise.

  • Tintin

    It’s all relative. To make sure, I just verified it in my basement with a shoebox, a flashlight and couple of bricks (a good approximation to rocks): according to Bahcall’s modeling, during my experiment, about 5 x 106 solar neutrinos/ cm^2-s zoomed through the bricks, but NO photons made it through! I therefore conclude that through the rocks under the Alps, neutrinos moved not only faster than light by a factor of 1 in 40,000, they move infinitely faster.

  • http://facebook Pamela

    Go Neutrinos go!!! I am excited and ready to learn more!

  • Nalliah Thayabharan

    All of my investigations seem to point to the conclusion that they are small particles, each carrying so small a charge that we are justified in calling them neutrons. They move with great velocity, exceeding that of light – Nikola Tesla 1932

    Experimental tests of Bell inequality have shown that microscopic causality must be violated, so there must be faster than light travel. According to Albert Einstein’s theory of relativity, nothing with nonzero rest mass can go faster than light. But zero rest mass particles can go faster than the light. Neutrinos have a small nonzero rest mass. Faster than light interactions are a necessity and they provide the non local structure of the universe. We should understand the relation between local and nonlocal events like the dynamics of universal structure. In any physical theory, it is assumed that there is some kind of nonlocal structure violates causality. If neutrinos are traveling faster than light, then neutrinos must be on the otherside of the light barrier going backwards in time, where the future can interact with the past.

    – Nalliah Thayabharan

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  • Elizabeth

    The information I have gathered from my physicist friends is that previous neutrino experiments had measured faster than light results, but were not used because of measurement uncertainties. Also, isn’t it only the tau-neutrino that is registering faster than light results (please let me know if I am mistaken)? If it were some kind of mistake or anomaly, wouldn’t other neutrinos measure faster than light results as well? Something very interesting is happening, and while I am skeptical, I can’t help but be very excited as well. I am holding my breath until the results are back from the Fermi Lab experiments.

    One more question, has it been explained yet how a neutrino can go the speed of light or near speed of light considering that it has mass, unlike had been previously thought?

    Also, to those physicists who are reacting to these results dismissively, that kind of response is just as damaging to good science as readily accepting the results as proof-positive. Be skeptical, not dismissive.

    I am not a physicist and greatly appreciate the informed discussions. This is all very exciting.

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  • sovan ghosh

    As we know that if a particle moves in a resisting medium , its resistance increases with velocity “v”.but the character of atmospheric resistance is difference .there is no such rule for this case.experiments results give us that 1. a particle moving with velocity less than 800ft/sec.resistance is varies approximately the square of velocity.
    2. when the velocity approaches the speed of sound the resistance varies as the cube or higher power of velocity but 3. if the particle moves higher than 1350ft/sec or greater that speed of sound again the resistance varies as the square of velocity . neutrino have tiny mass so it may be act like this when it moves faster than light, may be in the resisting medium it behave like this.
    may be when the particle moves at the speed of light it converts into into energy and this energy is actually the millions of neutrinos which can able to move faster than light and it is the smallest unit particle.
    but i have a question

    that is it possible to get the neutrinos with out fission and fusion ?

  • Paul

    I wonder if the neutrino beam is changing in some subtle way over the length of the 10 usec spill. For example, maybe the proton/secondaries beam is inducing currents in structure of the target, causing the particles to diverge slightly more, or maybe the graphite is expanding slightly due to heating, reducing the number of interactions.

  • george james ducas

    About your experiment concerning the speed of light:

    All constants with units are in fact variables. And so the speed of light varies. Only those functions that originate outside the universe appear in the universe as true constants such as pi are without units, which transcend.

    All functions in the universe are products of velocity and time

    E^(i*pi) = -1 = -D = Velocity x Time is the big bang

    All functions are products of the following equations

    Phi + phihat = 1 = D = time + velocity is the template for all quadratic and polynomial forms

    Phi x phiat = -1 = -D = time x velocity are single inertial fields or proper systems

    Einstein cosmological constant is equivalent 2 and 2 pi is the fine structure constant.

    2 represents (v+v)/v, the ratio of scalar and proper velocities, which is also the wave and particle duality.

    George James Ducas

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  • Jesse M.

    “The most straightforward idea is to violate Lorentz invariance, a strategy of which I’m quite personally fond”

    A question about this comment by Sean. I was under the impression that most of the time when physicists discuss the possibility of a violation of Lorentz invariance, they’re not actually suggesting that the most fundamental laws of physics break Lorentz-symmetry, but rather that spontaneous symmetry breaking shortly after the Big Bang might have left some sort of “relic field” present throughout space that would have its own rest frame, and particles would behave differently depending on their velocity relative to the field. That’s what seems to be suggested by this article for example. If it’s just a matter of a physical field with its own preferred frame, and the most basic laws are still Lorentz-invariant, then it seems to me there would always be at least the theoretical possibility of shifting the field’s rest frame (say by raising the energy levels to what they were before spontaneous symmetry breaking and thereby restoring the symmetry, then letting energy decrease so the symmetry gets randomly broken again). And if this is a case, it seems to me that any FTL would still at least theoretically allow for causality violation–Alice could send a message to Bob which was FTL in her frame but backwards in time in Bob’s, then something could shift the rest frame of the field between them, making it possible for Bob to send a reply which was FTL in his frame and backwards in time in Alice’s, such that she would receive the reply before she sent the original message. However completely impractical it might be to do this, it seems like at a theoretical level, as long as the most fundamental laws of physics are Lorentz-symmetric, any FTL should lead to the theoretical possibility of causality violations.

  • James Ph. Kotsybar

    — James Ph. Kotsybar

    The young lady known simply as Bright,
    who could travel at speeds fast as light,
    said, “While I’m never late,
    I’m concerned that my weight
    goes to infinite mass, though I’m slight.”

  • Steve Bergman

    I’m not a physicist. And I don’t even play one on TV. But I do try to keep up with the highlights as a layman. And with the understanding that peer review of this experiment has barely gotten started, and will likely turn up some unexpected systemic error…

    If it did turn out to be true, and if the neutrinos were taking a shortcut through one or more extra dimensions, could that mean that gravitons might do the same thing, and propogate slightly faster than light? And could it also mean that the surprising weakness of the gravitational force (compared to other forces), and the notoriously weak interactions of neutrinos with other matter, might be related?

    I’m not sure if that makes sense at all. I guess gravitons would be gauge bosons. And it’s really the force carrying gauge boson for gravity that is hypothesized to possibly dissipate into extra dimensions to explain gravity’s apparently weak force. And not any sort of fermion, like the neutrino.

    I just happened to notice the similarity between those two “remarkably weaks” in relation to the talk about extra dimensions being a possible explanation for these allegedly FTL neutrinos, and thought, “hmmm…”.

    -Steve Bergman

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  • noreneherman

    Einstein did not really get it in the end.

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  • h w looi

    If the scientists are right that neutrinos are faster than light, then contrary to what most experts believe in, neutrinos do not have any mass. And since they do not interact or interact as strongly as photons to the numerous types of particles, antiparticles, matter, dark matter and gravity in a vacuum, they are not slowed down by these entities as in the case of light. Therefore they should be able to move faster than light. The C in Einstein’s equation should be the speed of neutrinos in a vacuum!
    Actually, the particle or entitiy that has no mass, no charge and absolutely do not react or interact with anything in this universe should hold the ultimate speed record. Unfortunately, it is by definition impossible to detect.

    Alternatively, if neutrinos do have a tiny mass, then the speed of light in an absolute vacuum where there are none of those numerous types of energy, particles, matter, gravity etc. is in fact much higher than the 300,006 km/sec of the speed of the measured neutrinos. In other words, C > 300,006 km/sec and the neutrinos has not exceeded the real unimpeded speed of light. The speed of light that we have been measuring is not the maximum speed that light is capable of if it is not slowed down by the numerous “things” that really exist in a so called vacuum.

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  • Ruben

    If this results turns out to be real… I was wondering if the differences in speeds between light and muonic neutrinos are because the light weakly interacts with some sort of field that permeates the universe. Will the number resemble in order of magnitude to the one expected from a weak interaction with dark energy?

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  • David Schroeder

    Here’s a thought: What if neutrinos are slightly tachyonic only when moving through solid matter, and move at c in vacuum? In that case the speed of neutrinos from supernova 1987a would not be distinguishable from c. Assuming the superluminal departure from light speed for neutrinos is roughly proportional to the amount of matter they traverse, the arrival time of the 1987a neutrinos would be advanced by only a small fraction of a second. For example, if the amount of matter the 1987a neutrinos had to traverse was equivalent to 1000 times the distance in the Gran Sasso experiment, then these neutrinos would have arrived about 6 microseconds earlier than expected. That would have been completely unnoticeable.

    Something that might also be relevant: A team, led by Martin Tajmar, at the Austrian Research Center, reported acceleration pulses emanating from a rapidly spun-up, ring-shaped superconductor (2003-2007). These were tens of magnitudes larger than allowed by General Relativity. Perhaps there’s a connection to the strange neutrino results. As a garage tinkerer, I’m actually trying to replicate their experiment at:

  • http://NA Geoman631

    I am an engineer, not a physicist. Speed = distance over time. If the distance is wrong – the speed is incorrect. If we know the correct speed, we can calculate the correct distance???

  • BohdanUke1

    Puny Brains! Y’all think that by using @ 5-6% of your brain you know anything for sure?

    It will be proven that FTL particles do and have existed; whether it’s from this current experiment or others in the future. Another surprise… Duh.

    Airplanes won’t not fly ’cause they’re heavier than air… Infinity. What does that mean?

    Please, know one thing for sure: you don’t!

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  • Einstein family ?

    Undoubtably The LHC team will getting a letter of no- no from the
    Einstein Family .At c mass becomes infinite and the force required to
    becomes infinit fintithe s

  • Einstein family ?

    Undoubtably The LHC team will getting a no-no letter from the
    Einstein Family .At c mass becomes infinite and the force required is the same.
    We await peer review .

  • Vasanth BR

    Perhaps, when the particle is small enough for its wave function not to collapse and its velocity is large enough, it tunnels through space; traversing in a higher dimension.

  • Carl

    Extraordinary claims don’t require extraordinary evidence. It is the facts of the experiment that require an explanation. The explanation of these facts is that the particles are traveling faster than light. Or that there is an error in this theory. But they are unable to find the error. Subsequent experiments may unearth the error. But if the error is not found then does that mean the FTL theory is correct? NO. It just means an error in the theory hasn’t been found. What is required is not just another experiment (which might unearth an error in the theory) but an elaboration of the theory itself – how their FTL theory works – how it explains the facts. At the moment their theory is so vague as to be completely useless.

  • Tosh

    The reaction of many physics folks reminds me of the reaction of people in my profession (Aerospace Engineering) in the 1930’s and 40’s. Due to the Prandl-Glaurette compressibility expressions that were denominated in terms of the speed of sound drag appeared to increase asymptotically as v approached mach = 1. Obviously since we have rockets and supersonic vehicles this limitation was theoretical not practical. Clearly we haven’t observed (or known we’d observed) as many violations of this rule but the logic seems to flow.

  • S. Dino

    I certainly hope that the people at CERN did not make the mistake Torbjorn Larsson outlined in comment No.22 – that would be bad, but I do like the calculation, it’s of just the size to set things right. However, let’s assume CERN got it right; let’s assume those muon neutrinos really are moving faster than light. In the spirit of Jimthompson’s comment No.20 I propose the following:

    1) The electron-neutrino, like the photon, has zero rest mass. The muon and tau neutrinos have small (non-zero) rest mass.

    2) Mass increases with velocity as specified by m = m_o/(1-(v/c)^2)^1/2 but deviates from the Einstein equation at high energy such that as v goes to c mass is a high, but finite, multiple of the rest mass. In other words FTL velocities are possible – given enough energy. (Sorry AL, but you had a good run for 106 years).

    Given these assumptions we would expect the following:

    1) Electron-neutrinos from Super-Nova 1987A would arrive along with the photons from the explosion – just as was observed – because both the electron-neutrinos and the photons truly have zero rest mass and travel at c upon formation. Oh, and for those of you who insist on neutrino oscillation, the neutrinos (be they electron, muon or tau) produced by SN 1987A only had an energy of 10 MeV – not enough for FTL (see below).

    2) CERN’s 17 GeV FTL muon-neutrinos have enough energy (i.e. a high enough multiple of their rest mass) such that their velocity is greater than c (if only by a little).

    3) Given enough energy, not just muon-neutrinos, but electrons, protons and everything else with non-zero rest mass can be accelerated to v greater than c.

    Indeed, if we knew the rest mass of the muon-neutrino (which, sadly, we do not) we could derive a light-speed transition energy factor that we could apply to all matter. For example, if the muon-neutrino had a rest mass of say 1 KeV and assuming CERN’s 17 GeV transition to FTL, we would have a light-speed transition energy factor of 17 GeV/1 KeV = 1.7×10^7. It would then take 5.11×10^5 eV (1.7×10^7) = 8.7×10^12 eV = 8.7 TeV to accelerate an electron beyond c, and 1.6×10^16 = 16 PeV to accelerate a proton beyond c. These particle energies are beyond our current means, but this would explain why we have not observed FTL effects with these particles – we have not yet pumped enough energy into them.

  • TSK

    Before anyone is continuing to speculate over superliminal velocities, I would like to point
    out something interesting…

    Determination of the CNGS global geodesy

    To get the exact point on the surface of earth, we need to know the position
    of the GPS satellites for a given time and their distance from us. No problem so far,
    GPS is able to provide us with that information.

    The authors used the Bernese software which is available under

    There are some kinds of problems which will be further points of investigation
    if my first suspicion is incorrect.
    One problem: You will normally compile Bernese yourself and it is a known problem
    that FORTRAN compilers are very different in their quality to numerical
    problems. The second problem is that FORTRAN constants are stored in REAL
    precision (6-7 digits) if you are not declaring them. Anyway…

    Lets imagine a programmer did the marginal error of not using the correct
    reference ellipsoid value of 6 378 137 m, but the abbreviated version
    6 378 000 m.

    What will be the influence on the GPS precision ? Practically *NOTHING* because
    the satellites are symmetrically around the earth and position accuracy is very insensitive against
    height changes if the distance between sender and receiver is long enough.
    For example, to get a 18 m change for a distance of 730 km you need a height difference of
    5 km !
    So the values are in fact accurate concerning the position and noone will see a problem,
    the software is reliable.

    But what if you want to know the *distance* between two points on earth ? Having a slightly
    smaller value has the effect that the calculated distance is smaller than the actual distance.

    How much ?

    730534.610 km * ( (6 378 137 /6 378 000)-1.0) = 15.7 m

    15.7 m / 299 792 458 m/s = 52.3 ns

    Opera difference: 53.1 and 67.1 ns

    Strange coincidence, isnt it ?

  • Robert Clark

    It should be noted that superluminal speeds need not entail causality violations, that is, back in time signaling. What it would require is a preferred frame.
    See here:

    Newsgroups: sci.physics.relativity, sci.physics, sci.astro, sci.math
    From: Robert Clark
    Date: Sun, 2 Oct 2011 06:27:24 -0700 (PDT)
    Subject: On causality and superluminal speeds.

    Bob Clark

  • David Brown

    Consider this possibility: The OPERA experiment is correct given their false assumption about GPS calibration. The OPERA experimenters ignored what I call the Rañada-Milgrom effect.

    According to Rañada, the Rañada effect (as I call it), if it exists, “would imply that all the clocks would be changing with a constant acceleration or, in other words, there would be a nonuniformity of time.” My qualitative understanding of Rañada’s basic idea is as follows: In Rañada’s theory, the interaction of dark energy with the background gravitational potential produces a distortion in Einstein’s field equations. In order to mathematically model this distortion, Rañada distinguishes “the proper speed of light” from the “non-proper speed of light” (which is a result of the dark energy distortion underlying the Pioneer anomaly). The “proper speed of light” remains constant as the universe expands. The “non-proper speed of light” increases slightly as the universe expands due to the interaction of dark energy with the background gravitational potential. The “non-proper speed of light” is a book-keeping device to allow Rañada’s quantitative theory to predict the anomalous acceleration of clocks due to the Rañada effect. The non-proper acceleration due to the dark energy distortion in the background gravitational potential implies a blue shift of light with respect to the proper speed of light. “This means that an adiabatic non-proper acceleration of light has the same radio signature as a blue shift of the emitter, although a peculiar blue shift with no change of the wavelength (i.e. all the increase in velocity is used to increase the frequency).” (See page 9 of Rañada’s 2005 paper on the Pioneer anomaly.) A. F. Rañada’s “The Pioneer anomaly as acceleration of the clocks” Found. Phys. (2005)
    In Rañada’s theory, the anomalous acceleration of clocks is a result of how dark energy interacts with the background gravitational potential. In my physical interpretation of Seiberg-Witten M-theory with neutralino physics, the anomalous acceleration of clocks is a result of the weak interactivity of neutralinos and also how D-brane force interacts with neutralinos; the anomalous acceleration of clocks is an apparent effect because neutralinos are not detected — in other words, spacetime appears to get a slight extra redshift from the undetected neutralinos. When gravity attracts neutralinos, then D-brane force mysteriously and 11-dimensionally seems to cancel the inertial-mass energy of the neutralinos. I claim that Rañada-Milgrom real-or-apparent effect has a model consisting of replacing the -1/2 in the standard form of Einstein’s field equations by -1/2 + dark-matter-compensation-constant, where this constant is roughly equal to sqrt(15) * 10**-5.

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  • Koulder

    My long experience with measurements inclines me to say that systematic errors, the ones which affect accuracy, are often very difficult to assess, especially with absolute measurements like the Opera’s. One has to sift through hints and clues often scattered among a myriad of data, while stirring immagination in order to arrive at verifiable hypotheses.
    The problem is one needs to be determined like some investigators typical of some detective story. Several times it happened to me to be looked at as the “bad one” because of my resolution to track down possible sources of systematic errors.
    Perhaps someone already knows who could be the “bad” detectives by both CERN and INFN this time. They are strongly needed, I think.

  • John

    Very interesting discussion… how about revisiting Inflation Theory. The violation of c here is tiny, Inflation was huge, perhaps due to the energy differences. This will be worth investigating when all systematic measurements are vetted out. If relativity were not involved this would be just another odd result.

  • Aartisharma

    first of all scientist should check the speed of neutrinos in vacuum that decide the difference between the neutrinos & photons.higgs-bosson particle should be discovered by detecing it presence in sunlight & the rays coming out from the sun because it give an idea which particle is present in higgs-bosson which helps further in getting an idea from which particle our universe is created & which particle was emit first &which particle is fast.scientist can also find the higgs__bosson in recent developing solar system & can also find the origin of second recent developiing solar systemv

  • Aartisharma

    scientist should discover second recently developing solar system which particle makes the universe

  • Phillip Helbig

    Check out this paper:

    I particularly like the abstract.

    Another favourite of mine is by Max Tegmark, the famous poet:…470L..81T

  • Pingback: Neutrino Hypotheses Non Fingo | My Blog()

  • Guthrie Prentice

    Ironically, the suggestion that neutrinos take shortcuts in higher dimensions has actually been suggested as far back as 2005:

    and that neutrinos could even travel backwards in time using said shortcuts:

    by oscillating into sterile neutrinos, travelling through the extra dimension, and re-entering normal space then oscillating back into one of the 3 known flavors of neutrino.

    What is far more interesting though, is that these papers also state that gravity, being comprised of closed strings, like sterile neutrinos, could also take the same shortcuts. This might lead to interesting testable cosmological phenomena regarding gravity travelling faster than light as well.

    Also, this does raise a question in the back of my mind Sean, does this leave the door open for certain phenomena regarded as pseudo-scientific to have a basis in physics? Namely, I’m thinking that the flow of information either faster than light or backwards in time, might be possible if one embedded said information on a gravity wave or neutrino beam, meaning in future, a form of precognition or telepathy might be possible, if it isn’t naturally so already in a very weak form. (I’m actually a skeptic of psychic phenomena, but if faster than light travel of matter or information is allowed in physics, it does raise the question about what sort of phenomena might have to be re-examined simply to shut up the woo contingent.)

  • Everyone Knows

    “It is a miracle that curiosity survives formal education.” – Albert Einstein

    I’d like to believe that Einstein himself would be open to, and fascinated by the possibility, and wouldn’t be so arrogant to rule things out in order to protect his theories.

    People are often limited only by their own doing, hence they don’t even know they only think within a box!

    In all honesty I know nothing, but it’s all very interesting to me, whether or not OPERA’s findings stands the test of time!

  • Everyone Knows

    …..By chance I happened to watch a documentary on these findings the other day (on BBC2 I think!). I believe the that the media publicizing the astonishing findings of the OPERA experiment have failed to convey the mood of those conducting the experiment regarding the findings.
    The physicists explained on the documentary that they themselves find the results nearly impossible to digest and feel uncomfortable with accepting them. They have looked for every possible flaw in the experiment themselves.

    After thorough scrutiny, and no way to disprove their findings, they took the brave decision to release the results to the wider scientific community, to see if someone outside the OPERA group can find the flaw.

    They have not approached this like they are confident in their findings. They merely want to understand where they might have gone wrong. It was apparent to me that the OPERA scientists are in greater disbelief than you, me and everyone that refuses to believe.

  • WizardLarry

    Speed of thought is instant… in a sense that- If telepathy is possible- thought would travel faster than the speed of light. I know it’s just my mystified opinion, but some phenomena that are now proven and completely ‘normal’ were magical, when they were first encountered.

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Cosmic Variance

Random samplings from a universe of ideas.

About Sean Carroll

Sean Carroll is a Senior Research Associate in the Department of Physics at the California Institute of Technology. His research interests include theoretical aspects of cosmology, field theory, and gravitation. His most recent book is The Particle at the End of the Universe, about the Large Hadron Collider and the search for the Higgs boson. Here are some of his favorite blog posts, home page, and email: carroll [at] .


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