Neutrinogate: Speed of light appears to be relatively safe

Looks like those neutrinos that arrived 60 nanoseconds ahead of schedule in that CERN experiment, the one that everyone keeps claiming proves relativity incorrect in the absolute speed limit of the universe, may have been mismeasured after all.

To get a clearer picture, the distance the neutrinos traveled is straightforward. They began in CERN and were measured via global positioning systems. However, the Gran Sasso Laboratory is located beneath the Earth under a kilometre-high mountain. Regardless, the OPERA team took this into account and provided an accurate distance measurement of 730 km to within tolerances of 20 cm. The neutrino flight time is then measured by using clocks at the opposing ends, with the team knowing exactly when the particles left and when they landed.

But were the clocks perfectly synchronized?

Keeping time is again the domain of the GPS satellites which each broadcasting a highly accurate time signal from orbit some 20,000km overhead. But is it possible the team overlooked the amount of time it took for the satellite signals to return to Earth? In his statement, van Elburg says there is one effect that the OPERA team seems to have overlooked: the relativistic motion of the GPS clocks.

Meaning, rather than overturning relativity, the researchers just missed a potential variable.

I want faster than light travel to exist, because otherwise, crossing the vast gulfs of space between stars in a human lifetime is going to be impossible and Star Trek type universes are likewise impossible. But I’m not going to de facto assume that faster than light travel happened just because some practically insignificant amount of time was shaved off of an extraordinarily short distance. My money was always on a mismeasurement. And if the GPS clocks’ relativity resulted in a roughly 64ns delay in the timing, that fully accounts for the 60ns difference. The napkin calculation I linked before on a RCimT post pretty much says it all — if we got neutrinos that travelled that amount faster than the speed of light from a star we’ve been studying for some time, then it means we’d be getting some neutrinos several years ahead of schedule.

Edit: Bah, DarkSyde got to this before me. Ah well.

Neutrinogate: Speed of light appears to be relatively safe

17 thoughts on “Neutrinogate: Speed of light appears to be relatively safe

  1. 1


    I want faster than light travel to exist, because otherwise, crossing the vast gulfs of space between stars in a human lifetime is going to be impossible…

    You’re forgetting the Lorentz factor; it may require ridiculous amounts of energy, but from the perspective of the traveller, the journey time need not be excessive.

    … and Star Trek type universes are likewise impossible.

    Say it ain’t so!

    (Treknobabble FTW!)

  2. 2

    Agreed, John — but if Starfleet Command has already been wiped out by Klingons by the time the Enterprise reaches Alpha Centauri, what kind of universe would it be? (One where humans aren’t the good guys, I guess.)

    And of course, none of this mentions the fact that our DNA would be torn to ribbons in interstellar space without some way to shield us.

  3. 6

    Michael – I basically never use the “gate” suffix except ironically, and I thought I was being funny, in all honesty. I don’t particularly think anything but Watergate lives up to the Watergate scandal.

  4. 7


    Michael – I basically never use the “gate” suffix except ironically…

    I will put a note in my Google Reader that blogger #103 uses the “gate” suffix only ironically & leaves his readers to guess this 🙂

  5. 8


    Michael, I take it from the specificity of your two comments that you (as I) find nothing substantively disputable about Jason’s post, hence could but quibble about inconsequential trivia.

    (That’s to the credit of the blogger)

  6. 11

    I see the current neutrino measurements to be one more datum that would need to be very carefully verified before being taken with any greater weight: there is the well-known detection of 24 anti-neutrinos from the direction of the LMC at three separate sites several hours ahead of the first visual sightings of Supernova 1987A (previously observed to be a B3 supergiant, Sanduleak –69° 202).

    Against this is the current theory in some vogue of neutrino scintillation, positing that the various leptonic flavours of electron neutrino, muon neutrino, and tau neutrino oscillate between one another, which requires a non-zero rest mass and therefore ensure neutrinos cannot travel exactly at the speed of light: it doesn’t necessarily rule out superluminal velocities, but I’m unconvinced a non-zero rest mass (or to be precise, expectation values for the various eigenstates) would allow it.

    What we really need is a nice, close-by supernova event here in the Milky Way to duplicate the 1987 results, seeing as its been over 400 years since the last supernova in our galaxy. Hopefully not too close: several hundred light years would be nice and spectacular (the science fiction writers have legitimate worries about supernovas at a relatively small distance of say, 10 parsecs or so).

  7. 12

    Philip @11: Imagine for a moment that the original CERN neutrino trial is accurate (and duplicable), and that the calculated 64ns GPS discrepancy is also accurate. That means the neutrino arrived 4ns after what would be expected by the speed of light. That’s plenty under the speed of light to provide enough wiggle room for the scintillation hypothesis.

    Determining whether scintillation is happening though is a whole different story. The only experiment I could imagine (limited as a layperson though I am) would be a clean test environment where absolutely no outside interference could get in, where you can do nothing but shoot tons and tons of neutrinos at a detector until you start detecting the different flavors. How do you keep out neutrinos from the cosmos in such a rig? How did CERN manage it in their experiment, aside from just building deep underground?

    I do know that the sun’s spitting out ~1/3-1/2 the neutrinos we expected to see, so it’s well possible scintillation is happening. I just can’t wrap my head around how to test for it.

  8. 13

    Physics Prof. Chad Orzel (tutor to the Queen of Niskayuna) over at Uncertain Principles has this to say:

    …none of the stories I’ve seen about this (and I admit, I haven’t read all of them) contain any actual journalism. By which I mean that none of them include any comments from anyone associated with OPERA asking whether they think the claim has any merit. Which means that even taking the Arxiv Blog out of the equation, what we have here is a single-author preprint from somebody in the Department of Artificial Intelligence at a Dutch university, claiming to have found an issue that was missed by a large collaboration of physicists. Which is possible, but not what I’d call a rock-solid case. Until I hear something from people associated with the original measurement acknowledging that this is a possible solution, I’m going to remain skeptical

    Chad goes on to speculate about the nature of the error ~ it’s well worth reading the whole thing.

  9. 14


    if I’ve done my back-of-the-envelope calculations correctly, the travel time from the LMC is still a tighter fit to the speed of light in vacuo by an order of magnitude than the corrected-for 4 ns variance we’re speculating upon (“Imagine…”); and I gather 4 light nanoseconds is not hugely greater than the estimated tolerance for measurement (supposed to be 20 cm) so that I wouldn’t rule out another undiscovered error.

    [4 light nanoseconds:]
    3times 10^8 ms^{-1} cdot 4times 10^{-9} s approx 1.2 m

    [3 hours’ time difference in 168,000 years of travel, as normalised to a 730 kilometer path:]
    frac{7.3times 10^5 m}{8times 365times 1.68times 10^5} approx 1.5 mm

    i.e. much better experimentation required 🙂

  10. 15

    Michael: while I absolutely agree these experimentalists (first I’ve encountered that word, I always just used experimenter!) are not stupid, and that they’ve attempted to account for relativity by their own admissions, they evidently put out a call for scientists to doublecheck their work and spot something they missed. Meaning they WANT J. Random Blogger to try to outsmart them.

    For every person saying “you forgot to account for the curvature of the Earth”, there’s another person positing something that makes sense, like that the relativistic effects of the GPS-based time system they use actually has relativistic effects for transmission, on top of the relativistic effects that GPS already compensates for. And evidently, while they claim to account for relativistic effects, they did not explain how exactly they did so in the original published paper.

    Phil Plait has a good writeup of this here.

  11. 16

    Philip: So without proper duplication, a 4ns variance is within measurement error bars, or isn’t? I’m not sure which you’re suggesting.

    Also: holy crap, WordPress can do LaTeX without a plugin. That’s kinda awesome.

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