Relatively Speaking

With a hat tip to our occasional commenter Ron….

Remember those faster-than-light neutrinos? The ones that threatened to overturn relativity, and along with it everything we think we know about how the universe works?

Well, it turns out that maybe they weren’t faster than light after all — they might have only appeared to be faster than light because their arrival time was mismeasured. The mismeasurement was (it seems) caused by the researchers’ failure to account for the effects of ….. relativity!

I hear an echo of the great ongoing debate between Einstein and Bohr on the foundations of quantum mechanics. In an attempt to discredit the uncertainty relation, Einstein proposed an experiment involving a clock in a box on a scale. The clock opens a shutter at a precise moment, and while the shutter is open, a photon escapes from the box. The clock records exactly the time interval in which the shutter is open; the scale records exactly how much mass escapes from the box — and our simultaneous knowledge of the time and the escaped mass violates the uncertainty principle.

Bohr — after 24 hours of so of agony — triumphantly refuted Einstein’s argument by observing that a) the height of the clock above the ground is uncertain, b) therefore the gravitational force felt by the clock is uncertain, and c) therefore the measurement of time is uncertain — because relativity tells us that clocks run slower or faster depending on the force of gravity.

Einstein, in other words, had erred by failing to account for relativity. If this new explanation for the neutrino phenomenon proves correct, the neutrino researchers at OPERA will be in illustrious company.

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16 Responses to “Relatively Speaking”


  1. 1 1 Bennett Haselton

    So taking the latest twist into account, what’s *your* answer to the question that you posed at
    http://www.thebigquestions.com/2011/09/26/on-revolutionary-finds/
    i.e., which do you think is more likely — that neutrinos can travel faster than light, or that the South won the Civil War? (And would your answer have been different before the most recent revelation?)

  2. 2 2 Harold

    It was always much more likely that there was some error in the measurement. The intriguing thing is to find out where that is. This explanation has a beatiful simplicity, and a certain irony.

  3. 3 3 Mark Draughn

    The problem I have with van Elburg’s explanation is that it seems like a pretty obvious thing to check. If I understand his supposition correctly, the clocks are stationary (or close enough) but the problem is occurring when the clocks are synchronized via GPS, which involves satellites in motion. But that just means that the neutrino timings are off because the clocks are out of sync. That seems like an easy thing to check–and an important thing to check. More generally, the designers and operators of the GPS system are well aware of special relativity and design the on-board clocks to take it into effect. I’m sure the designers of the receivers used at national physics laboratories do the same.

    I’m not saying someone didn’t make a mistake (being a software developer, I naturally suspect an error in the analysis software), but clock synchronization seems like the kind of thing I’d check really carefully before announcing that something was moving faster than light.

  4. 4 4 Jerry

    “I’d check really carefully before announcing that something was moving faster than light.”

    Politicians change opinions faster than speed-of-light on a regular basis….

  5. 5 5 Ken B

    One thing that was rarely mentioned is that neutrinos have been “timed” before. We have observations of them from supernovae and while their speed could not be determined it seems that did not arrive early enough as the proposed time here would imply. In other words the claim had direct empirical problems from the get-go, whihc would argue for circumspection.

  6. 6 6 Roger Schlafly

    Chad Orzel does not believe this explanation. There are others who do not either.

    Einstein didn’t really believe in the uncertainty principle, and probably was not satisfied with Bohr’s explanation.

  7. 7 7 Mark Draughn

    Interestingly, although the supernovae neutrinos did not get here as fast as the CERN results suggest, they got here faster than the visible light wave (by about three hours). This is thought to be because they were emitted earlier in the process of stellar collapse…but what if it wasn’t? Also, an earlier experiment at Fermilab also seemed to show superluminal neutrinos, but with less statistical significance. Unless someone finds a clear error in the CERN experiment, someone somewhere is probably going to have to try this at least one more time.

    My own highly uninformed and uneducated guess is that this will turn out to be another example of a real superluminal phenomenon that doesn’t violate causality. Like phase waves, for example, which can move faster than light, but which can’t be used to transmit information faster than light.

  8. 8 8 Byron

    I’m in over my head intellectually on this, but here goes. Isn’t it an assumption of Einstein’s relativity that the speed of light is the speed limit on everything in nature? So how does accouting for relativity solve this problem of measurement of the speed neutrino. Aren’t we just importing Einstein assumption into this calculation on the speed of neutrinos?

  9. 9 9 Mike H

    @Byron – suppose a policeman books you for speeding, saying “you passed that bridge at 9am, and the next one at 10am. The bridges are 81 miles apart, and the speed limit is 80″

    However, your defence lawyer points out “the policeman’s clock is wrong”.

    Now, this doesn’t prove you were not speeding. It does mean that the policeman’s measurements don’t prove you were. If you adjust the measurement to take into account the policeman’s badly-behaved wristwatch, and perhaps your speed will be within the limit.

    Now, we have some neutrinos that were measured as going faster than ‘c’. Einstein’s theories are on trial. However, in their defence, someone has pointed out “the clocks were wrong. You failed to take into account General Relativity”

    This doesn’t prove relativity is correct. However, it does mean that the measurements that seem to show the neutrinos were speeding may not actually prove that relativity is wrong. If you adjust the measurements to take into account the researcher’s badly-behaved clocks, perhaps it will show the neutrinos were travelling within the limit.

  10. 10 10 Andy Wood

    @Byron

    Special relativity is well established from a multitude of previous experiments (Maxwell’s equations, the Michelson-Morley experiment, etc). All of it’s implications have to be accounted for before you can claim that it has been refuted by an experiment. If the clocks haven’t been calibrated properly because someone forgot about time dilation, then the theory isn’t being applied consistently.

    @Roger Shafly
    Thanks for that link.

    I must say, I’m with Chad Orzel on this. On Facebook, I offered even odds that the systematic error would be discovered within a year, and odds of 1 to 5 that it would be discovered within 5 years (nobody’s taken me up yet). The reason I was so stingy was that I assumed that with over 100 authors on the paper, the error would be really hard to find. (Compare with the Pioneer Anomaly, for instance.) I would be shocked if the error turned out to be something so trivial.

  11. 11 11 Roger

    Byron: Isn’t it an assumption of Einstein’s relativity that the speed of light is the speed limit on everything in nature?

    Einstein explained the theory in terms of assumptions, but, as Andy explained, there were experiments supporting relativity before Einstein.

  12. 12 12 Andy Wood

    I’d also add that it’s not an assumption of relativity that the speed of light is a speed limit on everything in nature. It follows as a consequence of more fundamental assumptions.

  13. 13 13 Ken B

    @Mark D: Even if they find an error someone will want to repeat it, correcting that error.

  14. 14 14 ted

    GPS satellites are not “good clocks” in their own inertial reference frames. They keep ECI time – time adjusted to be that in the Earth centered reference frame over which they are at the moment. Also, both the CERN and Grand Sasso sites have their own local cesium clocks, with GPS used only for synchronization. This would appear to invalidate van Elburg’s argument – but the GPS metrologists, who correct for various special relativistic and general relativistic effects, ought weigh in on the whole question.

  15. 15 15 sabre51

    Like some others I am definitely over my head. But could you speak to this a bit more? Isn’t relativity a direct consequence of the fact that the speed of light is constant regardless of the positions, speeds, and all other characteristics of the objects? That is, no matter how much relativity distorts the mass, velocity, etc. of the neutrinos, the measurement devices are a certain distance apart and no signal can travel that distance faster than a given speed (of light)?

  16. 16 16 Paul Tanenbaum

    It looks to me like there’s a logical error in
    the explanation of the result, whch you reference.
    It refers to relativity in its argument. But
    the experiment, per se, is a test of relativity.

    Is that not circular reasoning, the fallacy
    of petitio principii?

    PT

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