Particle Collider

Neutrinos Still Breaking Speed Limits

Article written: 18 Nov , 2011
Updated: 26 Apr , 2016


New test results are in from OPERA and it seems those darn neutrinos, they just can’t keep their speed down… to within the speed of light, that is!

report released in September by scientists working on the OPERA project (Oscillation Project with Emulsion-tracking Apparatus) at Italy’s Gran Sasso research lab claimed that neutrinos emitted from CERN 500 miles away in Geneva arrived at their detectors 60 nanoseconds earlier than expected, thus traveling faster than light. This caused no small amount of contention in the scientific community and made news headlines worldwide – and rightfully so, as it basically slaps one of the main tenets of modern physics across the face.

Of course the scientists at OPERA were well aware of this, and didn’t make such a proclamation lightly; over two years of repeated research was undergone to make sure that the numbers were accurate… as well as could be determined, at least. And they were more than open to having their tests replicated and the results reviewed by their peers. In all regards their methods were scientific yet skepticism was widespread… even within OPERA’s own ranks.

One of the concerns that arose regarding the discovery was in regards to the length of the neutrino beam itself, emitted from CERN and received by special detector plates at Gran Sasso. Researchers couldn’t say for sure that any neutrinos detected were closer to the beginning of the beam versus the end, a disparity (on a neutrino-sized scale anyway) of 10.5 microseconds… that’s 10.5 millionths of a second! And so in October, OPERA requested that proton pulses be resent – this time lasting only 3 nanoseconds each.

The OPERA Neutrino Detector

The results were the same. The neutrinos arrived at Gran Sasso 60 nanoseconds earlier than anticipated: faster than light.

The test was repeated – by different teams, no less – and so far 20 such events have been recorded. Each time, the same.

Faster. Than light.

What does this mean? Do we start tearing pages out of physics textbooks? Should we draw up plans for those neutrino-powered warp engines? Does Einstein’s theory of relativity become a quaint memento of what we used to believe?

Hardly. Or, at least, not anytime soon.

OPERA’s latest tests have managed to allay one uncertainty regarding the results, but plenty more remain. One in particular is the use of GPS to align the clocks at the beginning and end of the neutrino beam. Since the same clock alignment system was used in all the experiments, it stands that there may be some as-of-yet unknown factor concerning the GPS – especially since it hasn’t been extensively used in the field of high-energy particle physics.

In addition, some scientists would like to see more results using other parts of the neutrino detector array.

Of course, like any good science, replication of results is a key factor for peer acceptance. And thus Fermilab in Batavia, Illinois will attempt to perform the same experiment with its MINOS (Main Injector Neutrino Oscillation Search) facility, using a precision matching OPERA’s.

MINOS hopes to have its independent results as early as next year.

No tearing up any textbooks just yet…


Read more in the news article by Eugenie Samuel Reich. The new result was released on the arXiv preprint server on November 17. (The original September 2011 OPERA team paper can be found here.)

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55 Responses

  1. Brandon White says

    I don’t really know much of anything about this, just throwing out an idea.

    Gravity causes a distortion in space-time that all matter is bound to, but since the Neutrino is a WIMP, could it be possible for it to not be affected by this distortion.

    • Anonymous says

      I’ve wondered that myself. The supernova neutrinos crossed mostly “flat” space.

    • Anonymous says

      spacetime. Gravity is less of a force than really a sort of non-force. A particle falls in spacetime on a path for much the same reason a minimal flight path from New York to London takes you over Iceland. Since neutrinos are nearly massless the path they follow is not to different from the path of a photon.

      This matter is irritating. To be honest I find it terribly difficult to believe these results. There must be something not right with the setup.


      • Anonymous says

        LC, I truly enjoy reading all your comments and beg you to please not consider this disrespectful, but the fact that you find it irritating, makes it all the more interesting. I am literally perched on the edge of my seat, waiting for the next installment. I love physics!

      • Anonymous says

        I address this in a long post that his not restricted to a column.


      • Anonymous says

        Right now, I am on LC’s side here.

        Suppose you are traveling in a car, and the speedometer was saying zero. You point this out to the driver, he taps the speedometer, and the needle jumps up to a sensible position. Probably, the speedometer sticks. However, another passenger maintains that the car could have an alternative way to travel that ignores conventional space-time, so you can go between two separated points in space without velocity: this could revolutionize transport, but conventional science is unwilling to concede that the traditional theories are wrong, and the car and petrochemical industries are keen to prevent their vested interests…

        These latest timings do not fit with current physical models. They also do not fit with the results of other experiments. If you believe particles are traveling faster than light then you are believing in the results of one experimental team (who, to their great credit, admit that the results are extraordinary and likely to be a timing error) and rejecting the findings of many other equally diligent experimental teams in many different fields.

        As an experimental scientist, I believe that physical phenomena can be simulated with mathematics. I believe there is an explanation that will fit these measurements in with all the others. I hope that in time – may it be soon! – we have that explanation. I suspect the explanation will be a dull one; for faster than light travel breaks so much of conventional physics that it is hard to see how we could start putting Humpty Dumpty back together again.

        We shall see…

      • Anonymous says

        Physical phenomena can indeed be modeled/simulated through mathematics. However, one must always be careful not to assume any particular result of that mathematics is automatically physically true. Some mathematically possible solutions just don’t exist in the physical world, and believing otherwise can lead to lots of erroneous conclusions.

        For this, I’m hoping they are right and want them to be right, but I also agree that additional testing and experimentation is needed. As they say in the programming world, with enough eyes all bugs are shallow. With enough different scientists poking at the problem we will eventually get to what is really happening.

  2. Anonymous says

    Perhaps some thing is still up with physical aspect of OPERA facility that they’re still unable to account for.

    Why not run it on alternate facility?

  3. Daniel Beck says

    I think it’s too early to really say what will be the result, science has been wrong before… I happen to think it will turn out to be a bug in the system. But I wonder, what do you all think would be the result if this turns out NOT to be a bug. How might this change our understanding of things? Forget simply changing text books wouldn’t it potentially set our understanding of physics back nearly a hundred years?

    • Torbjörn Larsson says

      Why? These results, whether they are true or not, means that we are more informed than yesterday.

  4. CUSTOMER says

    What are the three state duty cycles looking like?

  5. Anonymous says

    It is better to have an open mind. Time and again the human race has proved that age old theories in can be dead wrong.

    • Redoubt South says

      Absolutely! We should at least now know that we aren’t nearly as smart as we think we are.

      • Torbjörn Larsson says

        Why? These results, whether they are true or not, means that we are smarter than yesterday. So we should probably think that.

    • Anonymous says

      It depends on what theories. Newton was not wrong, it is still in use. It was just not that accurate compared to Einsteins relativity theory.

      Being wrong does not automatically mean that all is wrong. It is just fine tuning the models. Or discover a complete new sets of physics.

      Also this discovery also does not automatically mean that god exists, that time travel is possible or some other quack pseudo science. Even if the neutrino does move faster than the speed of light then this does not mean that the humans would be able to use if for time travel. As far as I know, humans do not exists out of Neutrino’s. Everything you are surrounded also does not consist of neutrino’s. And on top of it, these speed difference is very small, probably useless on the human scale.

    • Anonymous says

      I comment in another post on this. We don’t want good theories to be “dead wrong.” We might expect them to fail outside some domain of observation, such as how classical mechanics gives way to relativity and quantum mechanics. Yet classical or Newtonian mechanics is a very robust way of looking at the world. It is not dead wrong. The OPERA results if they are correct are more disturbing than the black body problem or the perihelion advance problem in last 19th century physics.

      It is my hope that this is resolved, or that it remains some result unique to Gran Sasso that is not duplicated elsewhere. This can then be safely put away as not real.


      • Prof. Michael O. Zimmermann Ph says

        where are you going to post your comment on this subject??? give us the site, PLEASE

      • Anonymous says

        My post is here, dated or time stamped around the time I wrote the post you answered to.


      • // We don’t want good theories to be “dead wrong.” //

        well said LC. When Einstein came up on the scene, Newton did not go tumbling down.. it was just that the scope got (very) limited for Newtonian physics. So perhaps, with all this nano-level measurement we are:

        1. either looking at a finer level of physics where Einstein’s scope gets limited to a certain extent.
        2. or missing something – not to provoke a local/non-local hidden variable debate here! (:P) – in the instrumentation or the calculations.

        we’ll all have to wait for more tests like the one about to be conducted at FERMILAB.

        thanks a lot for the wonderful insight into the thing that’s happening with neutrinos 🙂

  6. Anonymous says

    The speed of the neutrinos, greater than c, permit they scape at the black holes. Since that the neutrinos have mass according to the four moment is false that the particles with mass can not travel above c. Also that the speed of the particles depend of the class of interaction since in the terms of energy the neutrinos are of similar to the high energy photons but the neutrinos have not the electromagnetic interaction. Thus, the speed of particles do not only depend of their inertia (thesis of the autor in his work Speeds greater than c.). It must include also the classes the interactions of the particles in the model for explain their speed.
    Alfonso Leon Guillen Gomez

    • Torbjörn Larsson says

      But wouldn’t ftl particles just have their own escape horizon (which would be the real event horizon now)?

      • Anonymous says

        The general physical condition for that a particle scape of a black hole is that travels above c. The neutrinos satisfy this condition.

      • Gore Gogore says

        no they don`t. They will just create another sfere of even horizon , smaller than (and contained inside) the one created by light because they travel faster and weight less (to nothing)

      • Anonymous says

        Please, what is your theoretical context?. For example, let insert next text taken of wikipedia: “One of the most well-known examples of an event horizon derives from general relativity’s description of a black hole, a celestial object so dense that no nearby matter or radiation can escape its gravitational field. Often, this is described as the boundary within which the black hole’s escape velocity is greater than the speed of light. However, a more accurate description is that within this horizon, all lightlike paths (paths that light could take) and hence all paths in the forward light cones of particles within the horizon, are warped so as to fall farther into the hole. Once a particle is inside the horizon, moving into the hole is as inevitable as moving forward in time, and can actually be thought of as equivalent to doing so, depending on the spacetime coordinate system used.” . To read right this text it must consider that is based in c as limit maximum of the speed. Of other hand, the energy of the neutrinos is similar to high energy photons. Thus, in a gross approximation we can omit their energies but no their speeds. Althought in the case of the photon its energy is not as particle while in the case of neutrinos whether. This is a great difference..

      • Anonymous says

        I would have to agree that the faster an object/particle is traveling the smaller its event horizon would be when interacting with a black hole. If going fast enough, I could see the event horizon reducing to a singularity/zero-size, which would be effectively unreachable by the particle in question, however.

      • Anonymous says

        Do you agree in the two contrary cases: 1. neutrinos fallen in a black hole 2. neutrinos are produced by a black hole?

      • Torbjörn Larsson says

        As krenshala notes, unless there is something about the structure of a black holes that prevents it, gravity would gradually increase towards the singularity.

        Hence neutrinos, which have finite energy and speed, would eventually fall into an event horizon of their own.

        If you are asking about Hawking radiation in the membrane approximation, the more realistic physics is perhaps of Unruh radiation in a high energy gravity field.

        The ever increasing curvature would give the same result for neutrinos. I assume they would observe the same effective black hole temperature (or the No Hair theorem falls) and the higher velocity would compensate for the higher local gravity acceleration where they have to be emitted. (See the first formula on the linked page.)

      • Anonymous says

        According to Relativity, if the neutrinos fall into a black hole or if a black hole produce neutrinos, inside of the black hole, would the neutrinos travel timelike paths (since v>c)?

      • squidgeny says

        What’s a “timelike path”?

      • He’s got it backwards, actually. You and I and everything we know travel in timelike paths because we move in time more than we move in space. A spacelike path is one that traces more movement in space than in time. Since the speed of light is the divider, you actually have to travel faster than the speed of light in order to trace a spacelike path. Wikipedia has more:

      • Anonymous says

        A curve on past light cone

      • Torbjörn Larsson says

        That depends on whether the observation is an independently repeatable fact, and what the new physics is.

        That is all open.

        What doesn’t seem to be open is particles escaping black holes, as of yet.

      • Anonymous says

        We have a new physical fact: the speed of the neutrino exceeds to c. I have proposed a hypothesis in the best scenary: The neutrinos escape from black holes, for discussion while this forum this open. The starting point is the standard theory of Relativity of Einstein of which I am a very old opponent. My questions are simple question of method. In the moment, it says that the neutrino travels in the time, exactly in the past. This is a inevitable consequence of the Relativity. Finally, the hypotheses are to test but it is not possible to prove what has not been formulated.

  7. Anonymous says

    A number of observations and measurements have thrown us some loops in the last several years. The first is from the FERMI and more recently INTEGRAL results on the arrival time for distant light sources. These sources are GRBs at billions of light years out. High and low frequency radiation arrive at the same time. That means there are no quantum fluctuations of spacetime, which is commensurate with what I am working on. I think quantum fluctuations of gravity only exist on horizons, and since spacetime is a holographic projection from horizons they carry no uncertainty. So I am fine with that. The LHC is telling us there are no Higgs signal above about ? = 2.5, which is too low a confidence level to say it exists. Based on the standard model and supersymmetric extensions of the standard model the Higgs field at interaction energy sqrt{s} above a few TeV should be shouting at us. This is a problem, but one which might be telling us that the symmetry breaking mechanism has subtleties we have not thought of. The other is that the electron has a monopole structure down to about 10^{-29}cm, which means any signature of stringiness is not there. Alright, this might mean the string for an electron is an open string attached to our cosmological D-brane and attached to another. There is then maybe a QCD-like flux across our D-brane which forces elementary particles, except the graviton, to have a point-like end on our D-brane and the other attached to another. This may put nice constraints on the wild and wooly world of string/M-theory. This can also be seen as potentially welcome. These results force us to ask reasonable questions, and may put constraints on our theories such that they are more understandable in the future.

    The problem with these OPERA results is that it means we are maybe really lost. The difficulty is less with traveling faster than light than it is with the stability of the vacuum. Here is the problem. In special relativity the rest mass of a particle obeys a momentum interval rule, similar to spacetime distance with space and time,

    (mc^2)^2 = E^2 – (pc)^2

    where p is a momentum. If p = 0 it is not hard to see where the biggest physics equation E = mc^2 comes from. Now I will set c = 1 and we have that

    m = sqrt{E^2 – p^2).

    If the momentum of this particle is such that it is moving faster than light then p > E, the square root is negative and the mass of this tachyon is imaginary valued. That is a problem, for physically we have no idea what it means for a particle to have an imaginary mass. Now let us quantize these results. The momentum is replaced by the operator p = -i?? and E = i??/?t and these operate of a wave function ?. I set ? = 1 for simplicity. This gives the Klein-Gordon equation

    ?^2? – ?^2?/?t^2 = m^2?.

    The term m^2? is negative and is associated with a potential V = (m?)^2 that a quadratic polynomial in the field. The force of this potential is F = -?V/??. This potential is negative valued and is a downwards parabolic function. So the tachyon runs away from any ? = 0 and is unstable. This means the vacuum is unstable. We then have a very serious problem if this particle should exist.

    Of course for neutrinos one must work with the Dirac equation, but that is mathematically more complicated, so I will defer from going into that. If neutrinos are tachyons then this means there is something going on which strikes hard at the core of physics. This almost means that our theories do not fail gracefully, such as how classical mechanics gave way to relativity and quantum mechanics.


    • Torbjörn Larsson says

      Thanks, interesting!

      That means there are no quantum fluctuations of spacetime, which is commensurate with what I am working on. I think quantum fluctuations of gravity only exist on horizons, and since spacetime is a holographic projection from horizons they carry no uncertainty.

      As you probably know by now, this layman has the temerity to agree with this from a position of enlightened ignorance.

      Gravitons likely exist, as you can derive them from (a low energy) quantization of general relativity. Whether as elementary particles or pseudoparticles is open, I take it.

      Spacetime appears to lack fluctuations. Hence spacetime would appear as a classic property. Whether as collapsed or decohered wavefunction, or any other mechanism, is open, I take it.

      I am intrigued by the formulation here. In your model, is the projection not carrying uncertainty because it doesn’t for fundamental reasons? Or because the projection makes the projected horizon appear classical? (Say, because of decoherence under projection from over the whole horizon surface.)

      for physically we have no idea what it means for a particle to have an imaginary mass.

      I think you mean for a real particle here. Virtual particles can have imaginary mass I think.

      One description I read over that is that virtual particles can be considered artifacts of our description of quantum field effects, similar to pseudoparticles such as phonons in crystals. Even electron mass is effectively changed as it travels in the conduction band of a crystal, hence we introduce “effective mass”.

      Imaginary mass would, I take it, adhere to effects that seems to violate causality by way of correlation but doesn’t, similar to entanglement. Say, classically a collective scattering induced by one wavefront that correlates with a later incoming wavefront.

      • Anonymous says

        Virtual particles are off shell and can be imaginary, and travel faster than light, so to speak. However, information still travels at v <= c.

        Low energy gravitons are constructed from the bimetric perturbation

        g_{??} = ?_{??} + h_{??}

        where h_{??}is a metric term with some perturbing influence on top of a flat spacetime ?_{??} metric. This term can be written according to field amplitudes ?_{??}

        h_{??} = ?_??_?.

        The field amplitudes are written according to raising and lowering operators a^† a

        ?_? = ?_? sum_k[a^†(k) f(k) + a(k)f*(k)]

        which fits into standard quantum mechanics. Here f(k) is an oscillatory function, k the wave vector proportional to the momentum and ?_? a polarization direction.. This is generalized for string theory. The graviton is then similar to a diphoton, which are “bunched” into pairs.

        The vacuum object which quantum fluctuates is the stretched horizon of a black hole. This is a surface one Planck unit or string unit of length above the classical horizon of the black hole. This object has no radial direction embedded in it, and the fluctuation is due to an uncertainty relationship due to the non-commutative geometry with the radius and time. The field data is on the stretched horizon and is holographically projected to the rest of spacetime. The fluctuation of the horizon by the r and t uncertainty determines the projection, but it does not correlate with a fluctuation of the spacetime coordinates outside the stretched horizon.


      • Torbjörn Larsson says

        Thanks again!

        So a fundamental property of the projection, huh? It would definitely add a certain je ne sais quoi, parsimony perhaps, to the hypothesis.

        I look forward to anything out of this. (I am rather agnostic about holography as such, not having understood how it comes about. So it places like Planck energy on my radar – if it exists, fine.)

  8. westelca21 says

    The only problem with the results is the apostles of Einstein refusing to abandon their religion, that they have based their entire lives and careers on and open their minds to other possibilities.

    Einstein’s theories have reached their limits, now it’s time to switch paradigms and rediscover the real scientific genius called Tesla.

    All Einstein gave us was the bomb, Tesla gave us the 21st century and we are still trying to understand all his discoveries, one hundred years later!

    • IVAN3MAN_AT_LARGE says

      Click here.

    • Torbjörn Larsson says

      I note that the keyword Tesla probably means we have an EU troll commenting.

      Science is acclaimed for its absence of faith and reliance on fact. The one who is touched by a religious outlook would be the one mentioning it.

    • Torbjörn Larsson says

      Unfortunately not unrelated to trolling of antiscience, this is why we all should stop using the apparent nonsense term “paradigm”.

      I haven’t read Kuhn’s work, but if he presented a testable definition and had it tested then or later, I am unaware of it. Rather, I read somewhere that he used ~ 20 different descriptions at one time or other.

      It is, to all appearances, a trivial “just so” story. The continued progress of science seems naively to invalidate any claims of different modes of it.

      We have too many of those stories, enabling confusing science and especially its edges with false folk science or philosophic claims. Just … stop!

  9. Anonymous says

    What if the neutrinos actually have a tiny negative mass?

  10. Anonymous says

    What if the Neutrinos have a tiny negative mass?

    • Torbjörn Larsson says

      I refer to lcrowell’s comment below: the vacuum would destabilize.

      • Anonymous says

        I’ve no idea if they have negative mass, but clearly the vacuum hasn’t destabilized (based on what others have posted the results would be). So either neutrinos don’t have negative mass, or having negative mass doesn’t destabilize the universe. 😉

    • Anonymous says

      “What if the Neutrinos have a tiny negative mass?”

      -please don’t think outside the box.

  11. Torbjörn Larsson says

    Besides the concern that massed ftl particles destabilizes the vacuum, the resulting form of time travel would destabilize the entire universe. Of course, as both results are founded in relativity (special vs general), why would a ftl neutrino care? =D

    The good thing is that the standard cosmology has validated general relativity and hence special relativity on all scales, now including the missing galactic sized scale (the Eris dark matter galactic model).

    3 additional points:

    – I read the new experiment has lost the earlier ~ 10 ns precision and ended up with ~ 50 ns due to the changed timing. Suddenly the 60 ns difference seems less certain.*

    – I read the number of abstaining OPERA members stays the same, ~ 15 out of ~ 100. (Round number, can’t remember if they have 80 authors or 80 members.) Some jumped on as authors, some left.*

    – “Researchers couldn’t say for sure that any neutrinos detected were closer to the beginning of the beam versus the end, a disparity (on a neutrino-sized scale anyway) of 10.5 microseconds”.

    That, and that the relativistic signal is actually mediated by the travelling wave front if a measured distribution of particles and not individual particles. Changing the wave packet form is how photon wave guides can make waves seem to travel “faster than light in vacuum”.

    * Um, okay, none of that in the Nature article. Maybe rumors then.

  12. Anonymous says

    If these results are true could this possibly be related to entanglement?

    • Torbjörn Larsson says

      No, entanglement carries correlation, not causation: the whole point of the validity of Bell test experiments (which have much more certainty than any other physics observation in some cases, up to ~ 20-30 sigma IIRC) is that they validate that QM obeys relativity.

      (And if QM obeys relativity, there can be no hidden variables, which is the reason to do the experiment.)

  13. magnus.nyborg says

    I personally still lean towards the result being an experimental error, but if it is not then it is very exciting.

    Perhaps afterall the key is the WIMPy nature of the neutrino wich allows it to travel through mass and interacts with its surrounding in an unprecedented way. If that is the case, then surely this will provide needed clues for a better understanding.

  14. Anonymous says

    Duplicate Ignore

  15. Anonymous says

    I sent a thesis to BBC stating what if neutrinos are not breaking the speed barrier but the time barrier. Einstein predicted that space time is warped around or even into the planet and part of this was proven in 2008 by the gyro experiment performed by NASA. What if somehow these neutrinos are interacting with this warped space time and their time frame is being slowed down. They would only appear to be breaking the speed barrier from our perspective time frame using our standard measurements but really time is just slowed down for them and they are travelling a speed below light speed. This would fit into relativity and both recent observations made would still be valid.

    Another theory I recently had:

    It was theorized some time ago that time slows down for objects as they approach the speed of light well neutrino’s are a different particle than light and they so say travel nearly the same speed so does this not affect them too?

    I mean I’m not a scientist (unfortunatly I was never in a financial position to get a PHD or anything like it) I just read a lot of stuff but to me it sounds silly to disregard decades of scientific knowledge based on an experiment which is NOT performed in a clean vacuum of space. Rather than trying to change science or debunk something which has been claimed maybe they should look at it from a different angle.

    When we use to run experiments in a test at school the tube had to be completely clean as to not be contaminated but this experiment is sending it through a planet which is not only spinning, has tons of radio and magnetic interference but also warps space time let alone all the other things we do not currently yet know. Interesting yes, but does it debunk Einstein, I don’t think somehow not with all the other things he has predicted that has come or atleast partly been proven true.

    I mean these are just ideas I had. I guess there’s probably more to it than this but I think something else is going on here. This is just my theory of it and I can’t provide calculations they are just observations I’ve tried to make by putting together other people’s work.

    I use to love connecting the dots as a kid 🙂

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