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Faster than light neutrinos? A quick calculation

by dave on September 22nd, 2011

A number of people on twitter and elsewhere (including my grad student, Austen) alerted me to an interesting story making its way across the interwebs. A number of sources have reported on a press release put out by the OPERA collaboration.

Here’s the basic idea: OPERA has a detector in Gran Sasso Italy, about 730 km from CERN. CERN produces neutrinos in abundance, and neutrinos have a few important properties:

  1. They are very nearly massless and thus, even at moderate energies, we’d expect them to travel essentially at the speed of light.
  2. They can “oscillate” or change identities, which means that the mu neutrinos produced at CERN can turn into tau neutrinos which the OPERA detector is designed to measure.
  3. They are very weakly interacting, which means that they can pass through solid earth unimpeded.

Light should make the journey from CERN to Gran Sasso in about 3 ms, but according to the OPERA collaboration press release, they are detecting the neutrinos as making the journey in about 60 ns less than expected.

In other words, they are claiming that, unless there is some hitherto undetected systematic, neutrinos are traveling faster than light.

A couple of caveats:

  • The actual paper doesn’t seem to be up on the arXiv yet, so I don’t know exactly what their measurement is.
  • Even once it is, I’m a theorist, not an experimentalist, so I’m unlikely to be able to identify the systematics.

That said, I am pretty darn certain that this result is flawed. Neutrinos have mass, which is why they oscillate in the first place, so if it turned out that a massive particle could travel faster than light (and it wasn’t some sort of issue with not correcting for general relativistic effects or something like that), that would pretty much overturn special relativity.

More to the point, I have a simple calculation that makes me extremely skeptical.

Remember that the neutrinos are supposed to beat light by about 60 ns over a travel time of 3 ms. That’s


  lead=\frac{6\times 10^{-8}s}{0.003s}=2\times 10^{-5}

Now consider a supernova explosion. In particular, consider Supernova 1987A.

This was an explosion about 160,000 light years from earth. The thing is, the neutrinos and the photons from the explosion reached us at almost exactly the same time. In the cause of intellectual honestly, I need to point out that the neutrinos were detected first, by about 3 hours, but this is because the envelope of the explosion was optically thick and the photons had to bounce around a while, while the neutrinos just streamed right out.

But how much of a delay between neutrinos and photons would we expect if the OPERA result applied?


  \Delta t=2\times 10^{-5}\times 160,000yr=3.2\ years

In other words, if the effect really were this large, we would have seen the neutrinos from SN 1987A way back in 1984. Yeah, we would have noticed that.

I don’t want to be too glib, however. There are a couple of key differences:

  1. The neutrinos detected from 1987A were (anti) electron neutrinos, not tau neutrinos. However, since neutrinos oscillate from one flavor to another, I’d be surprised if this was the key difference.
  2. The energies are quite different. In 1987A, neutrino energies were typically a few 10′s of MeV. The neutrinos measured by OPERA are a factor of 100 higher. It could very well be that this is a sensitive function of energy.

Of course, since the expectation is that neutrinos should NEVER travel faster than light, there’s no way to compute what we’d expect.

I, for one, am not going to hold my breath.

-Dave

Edit:

I posted this before getting my hands on the actual paper. In the cause of fairness, I need to mention that the authors of the paper talk about the constraints from 1987A themselves. They rightly refer to this result as a low-energy limit. As you can see from above, I find it unlikely that the differences between the high and low energy limit will have such a huge effect.

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70 Comments
  1. Alex permalink

    I know this is reaching, but . . . neutrino oscillations can still occur if one of the three flavors is without mass. Still, it wouldn’t explain why massless Tau neutrinos would be able to break the light barrier. I’ll sit with the skeptics on this one!

    • dave permalink

      Indeed. We technically measure the Delta m^2, but that doesn’t seem like a terribly likely possibility.

      Of course, were this to be the case, we’re still talking about violating Lorentz invariance. I say, no.

  2. Will Czaja permalink

    When I heard this news I desperately wanted to be back at Drexel to ask you about this. Thanks Prof. Goldberg!

  3. Where is the 100 MeV for neutrinos at OPERA coming from? Looking at http://arxiv.org/abs/1107.2594 it rather looks to me they are dealing with 17 GeV neutrinos, but I am by no means an expert in these things. These would be three orders of magnitude different from SN 1987A. As far as I know, most models with corrections to Lorentz symmetry predict a linear dependence of the correction with energy, so this would become a matter of a day instead of several years. On the other hand, if one assumes a Planck-scale symmetry breaking as in doubly special relativity models,
    this would require a ridiculously large prefactor to be observable on these scales.

    • dave permalink

      I didn’t have the paper at the time, so in my original entry, I had it as a factor of 10 rather than a few hundred (which I’ve since corrected), but in either case, the time dilation effect doesn’t come into it (again, supposing SR is correct). We don’t know the rest mass of any species of neutrinos, but there is no scenario where the gamma factors aren’t huge, and thus (according to relativity) the speed will be arbitrarily close to c. None of these calculations are done in the rest frame of the neutrino.

  4. EktoGamut permalink

    Could the clock synchrozation offsets between LHC and the OPERA explain this?

    • dave permalink

      I’m not sure if it’s quite that simple, but I wouldn’t be surprised if it was something along those lines.

  5. ben permalink

    A few things:

    a neutrino traveling faster than the speed of light would not overturn relativity. Relativity purports that a massive object cannot be accelerated from below the speed of light to a) the speed of light or b) above the speed of light. A massive particle simply winking into existence traveling faster than the speed of light is a valid (though highly unlikely) scenario. Second, I haven’t seen anywhere so far the idea that the lead time was a result of the probability function. Neutrinos don’t exactly exist anywhere. In fact, nothing does, but instead exist in this weird probabilistic space where they are more likely to be observed in certain locations over others. You could observe a rhino seemingly flash into existence in your room or office right now and that’s totally physically valid (though so ridiculously improbable that it’s not going to happen, ever.) but the detection of a particle in a space close to where it has the highest probability of being detected (which is usually how we define position, at least in layman’s terms) isn’t so ridiculously improbable that it wouldn’t ever happen. This is especially so if we are trying to observe huge quantities of neutrinos all the time, which we are, as each observation is another chance of an improbable but possible observation. And even if this isn’t a chance effect of making so many observations, maybe this isn’t a relativistic effect at all, but a quantum one (I love it when relativity meets quantum mechanics :) )

    Lastly, how do we know that the neutrinos from the supernova weren’t seen, or more correctly shouldn’t have been seen 3.2 years early? Neutrinos are incredibly tricky to detect, like you said, so you’re not going to find them unless you’re looking. That and we’re constantly being showered with neutrinos, so how would one know that a sudden surge corresponds to a supernova? Has anybody checked the logs from 1984 to make sure they didn’t get a bunch of neutrinos then? Just sayin..

    • dave permalink

      @Ben, interesting points, but a few comments.

      1. Not true, I’m afraid. It’s not just the case that you can’t be accelerated past the speed of light. A massive particle has an energy E=mc^2*gamma (this is a result of energy conservation and Lorentz invariance). For speeds greater than c, gamma becomes irrational. Energy conservation and Lorentz invariance (central ideas in SR) simply break down, so yes, SR would be wrong.

      2. There could be quantum tunnelling effects for a single particle, but the typical distance would be the wavelength of the neutrinos, a tiny fraction of a meter (and not ~100 meters, which is what would be required here), and it wouldn’t happen to thousands of them consistently.

      3. There were neutrino detectors in 1984, and there was never anything like the spike that we got from 1987A until 1987. It more than doubled our normal neutrino flux, and from that flux, astronomers were able to consistently describe the overall brightness of the explosion (in photons).

      It is possible that there were a few very high energy precursors that arrived a few years earlier, but again, I wouldn’t bet on it. It would have been a very odd effect.

      • Andre Engels permalink

        The difference is not ~100 meters, but ~18 meters. Still requires a very precise measurement not only of the time, but also of the distance – if I have not made a mistake in my calculation, calculating distance over the (flattened) surface of the Earth rather than in a true straight line already would have caused a 60 meter error.

        • dave permalink

          Back of the envelope calculation/error. I figure if it’s within a factor of 10, I’m fine (especially considering the ratio we’re talking about between OPERA and SN 1987A is ~10,000). But thanks for the more accurate calculation.

        • jumpjack permalink

          Distance amongst labs is 730534.61 ± 0.20 meters
          Neutrinos “won” by 18 meters.

      • student permalink

        I read somewhere about so called tachyon mechanics, which solves the problem of imaginary energy and tachyonic antitelephone and other paradoxes supposedly resulting from FTL particles. So it seems to me that tachyons could exist without breaking SR or causality.

        Also, couldn’t the universal speed barrier (c) be slightly more than speed of light? I mean, SR (actually just Lorentz-invariance) only says that there is a speed barrier, and it’s only hypothesized/measured that it’s namely speed of _light_. Just wondering if the effect (~10^(-5)*c) is big enough to be observed in tests of SR?

      • Terence permalink

        @Dave…(im not an expert just completing my bs in physics, but I was discussing this my prof)…you say A massive particle has an energy E=mc^2*gamma (this is a result of energy conservation and Lorentz invariance). For speeds greater than c, gamma becomes irrational…. I agree with this, but if a particle were to be created in a moving frame (no acceleration) and was to be traveling >c opon creation, it would theoretically have a set mass. This would be a set “true mass” therefore m/sqrt[1-v2/c2]. my argument would this would cancel if applied to Lorentz transformation. Eliminating the mass going to infinity.

        • student permalink

          Indeed, there is initially nothing wrong with tachyons having _formally_ imaginary mass, therefore yielding a real energy in the formula E=\gamma*mc^2, because both \gamma and m are imaginary.
          Check for example http://en.wikipedia.org/wiki/Tachyon and
          http://www.ejtp.com/articles/ejtpv6i21p1.pdf for an example in tachyon mechanics.

          There are, however, other things that result from an imaginary mass in quantum field theory, for example tachyon condensation and that tachyons must be spinless particles with Fermi-Dirac statistics, i.e., they are scalar fermions. It would be interesting to try to measure the spins of these neutrinos if they indeed are going superluminal (highly doubt it).

      • alex Zaharakis permalink

        But isn’t your argument about the neutrinos from the 1987 supernova implying that neutrinos at least travel at the speed of light?

        The 3.2hour difference is so small over the distance of 1600000 light years, one could either say that they travel at the speed of light or very very close.

        Now does neutrino light speed violate GR or SR because neutrinos are thought to have mass?

        One would need to approximate out the time delay from the envelope your talking about, then one could infer how close to the speed of light the neutrinos must be traveling.

        ???

  6. Pouria permalink

    Considering your Ask a physicist post a few weeks back, could gravitational waves have caused the discrepency?

    /P

    • dave permalink

      Interesting idea, but almost certainly not. The thing is, if this effect is real it’s (comparatively speaking) huge!

      To give you an idea, general relativity produces a time dilation effect of about 10^-9 on the surface of the earth (which would dwarf any gravitational wave effect). This effect would be several thousand times larger than that.

  7. dwarf permalink

    since analyzing data from particle physics experiments on a daily basis, I know, that tachyons are really common.
    We also do the time-of-flight method and I once spend half a year to find the effect that made kaons look as if they had ß>1. Still the ß-spectrum extends over the ß=1-limit because of uncertainties. And you always have more than you expect.
    I suspect the extraordinarily small errors have their origin in trusting libraries I use only as a rough guide since I know them better. I think the community will soon show them the right equations and then they will go to the building next door and seriously kick the programmers of that library.

  8. JadedIdealist permalink

    Could a slight error in the local curvature of the earth account for this?
    Unless they have a 732km long tunnel that is confirmed straight by shining a laser beam down it the the “as the neutrino tunnels” distance to the detector could be different from either the as GPS calculates distance or the as the surface radio wave travels (slightly incorrectly adjusted for)?

    That is might it be that the neutrinos traveled about 2 metres less distance than they thought because they went in a straight line.

  9. jumpjack permalink

    I guess the neutrinos path is underground.
    What if neutrinos passed through some unknown material which accelerated them over light speed? Wouldn’t it be cool?

  10. qazplm permalink

    I agree one should be skeptical, but isn’t this another in a long string of, for want of a better word, hints that neutrinos (at least some type(s)) can sometimes be tachyons?

  11. nomnom permalink

    how fast would these particles be then? in metres per second.

  12. mike m permalink

    @jumpjack I think your unknown material idea adds another layer of unlikely to this since it would also violate the first and/or second laws of thermodynamics.

    Dr. Dave, I have a few questions about this result that haven’t been answered in what I read yet.

    1. Isn’t the speed of light through the dirt from Switzerland to Italy slower than the speed of light in a vacuum? Are they claiming a discrepancy against the slower or faster speed? Would a discrepancy with the slower speed that still stays under the faster speed actually violate SR?

    2. How well understood are the neutrino oscillations? What causes them and how do their physical/quantum properties change?

    3. At the engineering level I am astounded by the measurement accurancy that they claim and would love to know more about how they accomplish the various measurements. In particular, in order to time the journey they need to know precisely when it starts. Isn’t the neutrino source firing in all directions with equal probability? Perhaps so many are created that the delay until first detection is very small. In any case that source of error is in the wrong direction to explain the result.

    4. If one flavor of neutrino was in fact massless and happened to be the one created at the source, what constraints on its maximum velocity would current understanding place?

    5. Some experiments with laser light pulses have also seemingly shown light leaving a material before it entered, but this was interpreted as the group velocity exceeding the speed of light in a vacuum, while the individual photons still propagate at the expected speed of light for the material. Could something like this be happening the present experiment? I have not read anything suggesting that the neutrinos are sent in pulses so I expect the answer is no. But I wonder if probability-based measurement of a neutrino starting its journey and a probability-based measurement for the neutrino ending its journey together effectively create something pulse-like in the data.

    In any case, the prospect that some part of current understanding is wrong is always exciting. I would think the folks involved have been very careful in verifying the result before going public with something like this knowing the reaction that it would receive, so even if it is ultimately some type of systematic error, it could still be new and interesting in its own right.

  13. Etienne van Zyl permalink

    or maybe our value for light speed is inaccurate as true light speed can only be attained when photon experience no interaction (i.e. in a perfect vacuum), which we cannot recreate when we measure the speed of light here on earth. So maybe ‘c’ is actually neutrino speed and that the slower light speed we measure is a function of our limited experimental abilities, and that light would indeed travel at ‘neutrino speed’ in a perfect vacuum.

    • Roy Gilsing permalink

      @Etienne: this was my first thought exactly! Maybe the conclusion might be that the light speed is not the absolute maximum, but neutrino speed (or even above) and that E=mc^2 should in fact be E=mn^2 with a slight error in all experiments ever done with the wrong “c”. Is this possible?

    • James T. Dwyer permalink

      Perhaps, but the zero rest-mass photon should propagate at greater velocity than any fundamental particle with positive mass.

      However, many of the characteristics of neutrinos seem to be still undetermined, but then much that seems to have been determined is beyond my comprehension. As I understand, evidence indicates that neutrinos oscillate between their three flavors at rates that vary in certain conditions. Each flavor is considered to have differing but tiny amounts of mass. Particle propagation velocity is inversely related to its mass. A MSW effect (see below), also known as the ‘matter effect’, can modify the oscillation characteristics of neutrinos in matter.
      I have found some seemingly related discussions in wikipedia.

      http://en.wikipedia.org/wiki/Neutrino_oscillation

      http://en.wikipedia.org/wiki/Neutrino_oscillation#Beam_neutrino_oscillation
      http://press.web.cern.ch/press/PressReleases/Releases2010/PR08.10E.html
      “On 31 May 2010, the INFN and CERN announced[2] having observed a tau particle in a muon neutrino beam in the OPERA detector located at Gran Sasso, 730 km away from the neutrino source in Geneva.”

      http://en.wikipedia.org/wiki/Neutrino_oscillation#Propagation_and_interference
      “Eigenstates with different masses propagate at different speeds. The heavier ones lag behind while the lighter ones pull ahead. Since the mass eigenstates are combinations of flavor eigenstates, this difference in speed causes interference between the corresponding flavor components of each mass eigenstate. Constructive interference causes it to be possible to observe a neutrino created with a given flavor to change its flavor during its propagation.”

      http://en.wikipedia.org/wiki/Mikheyev%E2%80%93Smirnov%E2%80%93Wolfenstein_effect
      “The presence of electrons in matter changes the energy levels of the propagation eigenstates of neutrinos due to charged current coherent forward scattering of the electron neutrinos (i.e., weak interactions). The coherent forward scattering is analogous to the electromagnetic process leading to the refractive index of light in a medium. This means that neutrinos in matter have a different effective mass than neutrinos in vacuum, and since neutrino oscillations depend upon the squared mass difference of the neutrinos, neutrino oscillations may be different in matter than they are in vacuum.”
      “The MSW effect can also modify neutrino oscillations in the Earth, and future search for new oscillations and/or leptonic CP violation may make use of this property.”

  14. I think they would have to check the calibration of the sending/receiving equipment, to ensure they are both synchronized. If the clocks differ, due to miscalculation, or another effect, such as quantum tunneling; then the result may simply be erroneous.

    If the observable result can [my emphasis] be reproduced by other empirical measurements, it still doesn’t make it correct. Just, reproducible.

    Thank you for posting your analysis, very interesting reading.

  15. Brian Sims permalink

    Note that the experiment does not show that that the neutrinos arrive before photons arrive OVER THE SAME PATHWAY. Rather, it shows that the neutrinos arrive before photons would be expected to arrive over a pathway in which it is impossible to beam photons because the path is through the Earth.

    This also means there’s no way to optically measure the straight-line distance between the two points. In other words, the distance between the labs has to have been derived, using some formula or reference table, rather than measured precisely using a laser. I suspect there is an error in the calculation of the distance between the two labs. I doubt that any reference source used will have been designed for such close accuracy, much less checked between these two particular points.

    The only way to be really certain is to repeat the experiment using a target that has the same pathway open to both photons and neutrinos and directly measure the transit time for each.

    • Brian Sims permalink

      I should’ve waited for the OPERA collaboration’s seminar in which they explained how they measured the location. It certainly bolsters the claim. But if true, a speed for neutrinos faster than c doesn’t necessarily destroy relativity. It could simply mean that neutrinos have less mass than photons, so that the true c should be the speed of neutrinos, not photons.

  16. Gregory Ward permalink

    Regarding mike m’s #5, could there be a slight favoring of faster neutrinos when they look for a particular kind? In other words, not all neutrinos change types, so could the faster (higher energy) ones change types more often than the slower ones, leading to a bias in the measurement of the group velocity? It sounds like they’re only detecting tau neutrinos on the receiving end.

  17. Namara Verdi permalink

    If there is no systematic error, nor human error (which I hope there is/are), then there must be some properties of the neutrino that scientists are not aware. Pure speculation…..matter speeds them up….there is a worm hole in the earth’s crust between CERN and OPERA……the OPERA guys are pulling a sick joke on everyone…however unlikely, the latter seems more probable…hahahahaha

  18. Keith Vinson permalink

    OK, Maybe I haven’t looked hard enough, but my first thought was how did they measure the straight line distance to 20 meter accuracy to begin with?

  19. Nalliah Thayabharan permalink

    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

  20. What if they aren’t traveling faster than light at all. Rather taking a shortcut that we can’t measure or see.

    Is it not imaginable that they took a different route?

  21. James T. Dwyer permalink

    I’m just an innocent observer, but there are some special conditions that might apply to this experiment that might effect the traversal velocity and/or the actual proton-neutrino traversal distance (whatever the experimenters presumed the ideal path of detected neutrinos would be):

    While light is curved when traversing spacetime curved by massive objects, the near relativistic slightly massive neutrinos might be more effected by gravitation.

    The non-zero mass neutrinos passing through the Earth must be effected by its gravitation to some extent, perhaps changing the actual path followed. If the experimenters’ distance estimations presumed some specific (especially if curved) path through the Earth, neutrinos might have actually followed a shortened path over such longer distances.

    While some idealized estimation of gravitational effects might have been employed, actual mass distributions and local gravitational effects can vary at small scales, possibly producing an actual distance discrepancy.

    I understand that the Mikheyev-Smirnov-Wolfenstein effect alters the incidence of neutrino flavor (and mass?) oscillations. Tho the extent that mass and gravitational interactions distinguish neutrinos from light, the neutrinos passing through the Earth’s dense matter might effect neutrino velocity relative to neutrinos or light in interstellar space.

    I suspect that some idealized assumptions in the estimation of distance traversed are subject to unidentified variations producing a discrepancy with actual distance traversed.

    Other factors such as some unaccounted relativistic effects of neutrino velocity, its mass and Earth’s gravitation may have also affected actual neutrino velocity in some unexpected way…

  22. Lost in Space permalink

    If the neutrinos are indeed exceeding c could their increased mass be an indication that they now possessed the properties of more massive ‘sneutrinos’ as in supersymmetry? Perhaps the added energy has somehow converted them? And if so, could their energy now be considered negative?
    And wouldn’t it mean that mass doesn’t have to increase infinitely to reach or surpass c?

  23. Jeremy permalink

    If the spot to spot distance was used to calculate this speed than these claims to have found something travelling faster than the speed of light would be wrong as they would have not accounted for the curvature of the earth. They say that they found them travelling at 1 in 40,000 times faster than the speed of light, but the curvature of the earth would counteract that due to it being approx 46 degrees north (geneva) to 42.4 degrees north (L’aquila). This would mean that that 3.5 degree curvature would compensate for the 1 in 40,000 difference

    This is if the spot to spot difference is used ^^

  24. To be fair the discrepancy with the observations of supernovae were reported together with the original results. For once sensational findings and caveats reached the media nearly simultaneously, like photons and neutrinos from SN 1987a

  25. James T. Dwyer permalink

    As I understand, the detected neutrinos were determined to be FTL by comparison of their statistically derived Time of Flight (ToF) with the ToF estimated for light traveling what was presumed to be the same distance.

    I understand that the distance traversed was presumed to be that returned by standard GPS routines: following the curvature of the Earth! Is there any reason to expect a neutron beam to follow the curvature of the Earth? I don’t think so – please let me know if I’ve overlooked something!

    If in fact the reference speed of light ToF estimate was based on a presumedly curved flight path and the detected neutrinos actually followed a shorter, more direct, flight path through the Earth, the difference between presumed and actual distance traversed could fully account for an erroneous FTL determination of comparative ToF!!!!

    I’m not the only person to identify this potential source of error, but I would like to somehow reach the OPERA collaboration for evaluation! In my experience, it’s often the silly little errors that produce the most intractable problems…

    • dave permalink

      I’m reasonably certain they didn’t do that, but a quick calculation reveals that taking the curved (over the surface) route rather than the direct (through the earth) route would only result in an increase in pathlength of 4m, less than a quarter of the purported result.

      • James T. Dwyer permalink

        Thanks for checking – statements like “…a high precision geodesy campaign for the measurement of the neutrino baseline…” make me suspicious, since the actual path and and therefore distance traversed by detected neutrinos cannot be definitively determined.

        Any discrepancy between the distance assumed in the estimated speed of light baseline and the actual distance traversed by detected neutrons would result in error.

  26. gnomic permalink

    Is it possible that nutrinos follow a different path than light? I’m not taking extra dimentions, but somehow don’t exactly follow the same path through the fabric of spacetime as we understand it.

    OK, I doubt this too as it seems like we would have seen it, but….

    • James T. Dwyer permalink

      Well, even zero mass photons do not propagate linearly through gravitationally curved spacetime – IMO non-zero mass neutrinos should be expected to deviate even more from a linear path (apparently presumed by distance estimations in these experiments) – even when propagating withing the Earth. There is some reason to think that they might deviate even more – please see “the matter effect”: http://en.wikipedia.org/wiki/Mikheyev%E2%80%93Smirnov%E2%80%93Wolfenstein_effect
      “The MSW effect can also modify neutrino oscillations in the Earth, and future search for new oscillations and/or leptonic CP violation may make use of this property.”

      Perhaps we’re ‘seeing it’ (and other things) now!

      • dave permalink

        The gravitational bending of space-time near the surface of the earth is about 10^-9, a factor of 10,000 smaller than the effect seen.

        • James T. Dwyer permalink

          There might be some secondary effect that is significant, such as more massive neutrinos being selectively deflected away from the detectors, skewing results, for example.

          IMO, there are too many unidentified potential effects to consider that neutrino traversal time has been so precisely determined. The actual path and distance traversed cannot be definitively determined – correct?

  27. gnomic permalink

    Another thought… could the experiement itself have expanded the universe – at least as far as the neutrino generation was concerned? Think of the leading wave occuring away from the center of the collision as far as the what we observe. This could in theory occur if neutinos are a paired particle or emitted away from the center of the actual collision.

    Hey…I’m spitballin’ ideas here.

  28. Gorsa permalink

    Is it possible that the neutrino only exhibits the >c speed if it is traveling through mass and not through a vacuum. If this is the case and you account for Supernova 1987A, would the 3hr early arrival simply be an indication of the amount of mass the neutrino passed through on it’s way to us?

  29. Stefan Little permalink

    I haven’t read all the comments but my first thought upon reading the web articles about FTL neutrinos is: does the difference in speed between the clocks in Geneva vs the clocks in Italy account for the difference? I am referring to the Italy site being closer to the equator and thus having a higher angular acceleration from the rotation of the earth.

    I apologize if a similar question was already posted.

    • Jose_X permalink

      A syncing problem might exist, but I would think clock variations due to location on earth, if significant, would not have been overlooked.

      • Jose_X permalink

        I should have added that I would think it’s possible to sync using one set of instrument delays and then do the measurements with a different delay. This would explain data that appears to show too fast neutrinos (or too slow).

        Why might the different delays exist? There are many possibilities, but we should note that digital electronics frequently have a sw component that might have been changed recently without proper analysis of the time issues of the algorithms. In fact, I think the paper mentions an upgrade in the GPS sync hardware in 2008. These new tighter time constraint assumptions might not have led to a re-evaluation if the timing assumptions/requirements in the rest of the system.

        For apparatus recently upgraded and performing measurements at precision levels never attempted before, we can easily see how an instrument design assumption error might sneak in (even more likely if COTS hardware with custom sw forms part of the system).

  30. kevin permalink

    1) Would there be any value in building a second detector say half way along the line, position measured accurately etc, then if the time of flight, (TOF) is halved and hence the arrival time ahead of light (AOL) also halved would it not indicate either a true variation in speed of the neutrino AOL or some proportional anomaly in calibration.
    2) If the TOF differential at the new detector is the same as that observed at the existing detector it would indicate that it is not a change in velocity but a definite calibration error.
    3) In addition a second detector could provide useful information regarding the detection of the neutrino front and true synchronisation of all three apparatus.
    4) Also as with the Hubble space telescope mirror that was ground very accurately but machined incorrectly throughout to put it simply, the differentials between the two detectors could be made and hence subtract any gross error thus accounting for the true velocity of the neutrino beam?

  31. Fred permalink

    I’m no expert and there could very well be some unaccounted for error causing these result but……if these result are accurate I’m willing to bet it’s the result of a quantum effect equally as strange as the observer effect and entanglement.

  32. Larry Gray permalink

    This is exacty the thought I had when I first heard about this. The difference from the supernova result must be explained before the Opera result can be credible. I am not aware of a second supernova observation that would allow any deviation from c for neutrino propogation to be calculated more directly, but I would think this would be much more credible.

  33. Sarantopoulos permalink

    La beauté de la science est qu’elle n’a pas de dogme.
    On peut tout remettre en question, même la vitesse de la lumière.
    ——————————————————————————

    Acceptons le fait, jusqu’à preuve du contraire, que les mesures faites par le CERN sont correctes, et
    supposons que les neutrinos voyagent à la même vitesse que celle de la lumière.

    Que s’est-il passé lors de la mesure de la vitesse des neutrinos?
    Il y a de la gravitation positive et de la gravitation négative!

    Si la lumière parcourt une distance de 730 km à la surface de la Terre, le trajet ne sera pas en ligne droite, mais il épousera la courbure de la surface de notre planète, et subira une attraction égale durant tout le parcours, donc un freinage égal.

    Lorsque le neutrino parcourt une distance de 730 km, le trajet sera en ligne droite. Ce n’est qu’au départ et à l’arrivée qu’il subit une attraction égale à celle du photon, soit la force du diamètre de la Terre. Mais durant la pénétration de la matière il subira une attraction inférieure à celle du photon, donc il sera moins freiné et parcourra 730km plus rapidement.
    Remarquons que ce ne sont pas les mêmes 730km.

    Pourquoi le neutrino subit-il une attraction inférieure en pénétrant dans notre planète?
    Nous dirons que la matière en dessous de lui est celle qui contient le centre de la Terre. Comme il pénètre dans la terre, une partie de la matière est au dessus de lui, ce qui crée une attraction contraire à celle produite par la matière sous lui, tandis que la matière sous lui étant moins importante, il y aura moins de freinage.

    Conclusion, durant la pénétration de la matière par le neutrino du fait de son voyage en ligne droite, le freinage, par rapport à celui du photon est diminué pour deux raisons:
    la masse en dessous de lui est diminuée, donc moins d’attraction positive = moins de freinage.
    la masse au dessus de lui crée une attraction dans l’autre sens, une attraction négative à soustraire de l’attraction positive, ce qui diminue encore le freinage. donc il sera moins freiné.

    Le neutrino a-t-il la même vitesse que la lumière?
    Il faudrait trouver un endroit, dans le vide, et loin de tous corps célestes, afin d’éviter l’effet de la gravitation et pour la lumière et pour le neutrino.

    Meilleures salutations scientifiques.
    P. A. Sarantopoulos.

  34. Ian permalink

    One quick observation, perhaps a tiny enough particle, with mass, moving at the speed of light, could move faster due to “slingshotting” through the gravitational pulls of the other particles around it? On an atomic scale, such small mass, may actually prove to speed up. It’d be like our sun and a comet coming close to striking, but narrowly missing. Or perhaps the forces of two atomic particles revolving in opposite directions as the neutrino passes between, much like the old hotwheels toys with their little speed booster that grips and flings the car down the track. It’s always a thought.
    Sorry about the delay.

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