Of Particular Significance

Why the Curtain Has Not Fallen on OPERA

POSTED BY Matt Strassler

POSTED BY Matt Strassler

ON 02/27/2012

For those of you who read the news reports about OPERA, and its potentially (not) superluminal neutrinos, on Thursday or on Friday morning, and stopped following after that, I have news for you: almost everything that appeared in the press up to that point was wrong in some important details.  Thanks to my readers and their comments and detective work, we’ve collectively managed to figure out much more clearly what’s actually going on.  I put up a relevant post Thursday morning and another Thursday afternoon, but I especially recommend Friday morning’s post (and comments) and Friday afternoon’s post (and comments).  I really emphasize the value of the comments; I have some very well-informed and insightful readers who contributed a great deal.  You can read this summary post first, and then go back to the older posts and read through the earlier viewpoints and the detailed commentary.  [The science press has caught up, though; here’s an accurate article from 2/27 in Nature.]

Most press reports on Wednesday, Thursday and Friday boiled down to this statement: “The OPERA folks found a loose wire, and when they fixed it their timing shifted by 60 nanoseconds [billionths of a second], bringing neutrino speeds right back to where they were supposed to be.”  That’s certainly what the original Science Insider article implied, from which many articles took their cue.  This is illustrated in the Figure below (labeled (b) to be consistent with a figure from an earlier post. )  The original OPERA result — that neutrinos arrived 60 nanoseconds before they were expected to — is shown as (a).

But this statement is completely wrong.

(a) OPERA originally claimed neutrinos arrived early by 60 nanoseconds (ns), with an uncertainty of about 10 nanoseconds, shown by the black vertical bar. (b) Incorrect press reports widely suggested that OPERA had found a mistake (a "loose wire") that caused a 60 nanosecond shift and brought the measurement back into agreement with expectations. (d/e) But in fact the two problems identified so far by OPERA, a sensitivity to an optical fiber's exact orientation and a miscalibrated timing oscillator, are both large compared to the original measurement, are both imprecisely known, and point in opposite directions. This makes the situation entirely unclear for the moment.

In fact the OPERA press release made clear that there were two problems (a problematic fiber-optic cable and a miscalibrated oscillator), causing shifts in opposite directions, and mentioned that a re-run of the experiment would be necessary.  Still, most press articles seemed to give this lip service, and assume the correct reading of the situation was that the fiber was the main source of the problem, and that a re-run of the experiment was just pro forma.  They mostly stuck with the simplistic idea that the OPERA people found a mistake and now everything agrees nicely with Einstein.  A few, such as the New York Times, did a somewhat better job.  But they still missed key points.

So what is the real story?  Probably in the end everything will indeed agree with Einstein, but that is not known to be the situation right now.  Instead things at OPERA are in a much greater degree of disarray.  The two problems they identified are pretty big, potentially as big as the effect they measured or bigger.  This is illustrated in (d/e) of the Figure.  They know roughly how big they could be.  But they have no idea how big they actually were during the experiment.  Not yet anyway — they’re working on it, through indirect methods that they haven’t described to us.  In the case of the fiber they have made clear that the effect could be up to 100 nanoseconds, but might be smaller.  And they have implied that the problem with the oscillator could be tens of nanoseconds, though they haven’t been precise about that.    The sum of the two problems together is therefore completely uncertain; it could be big or small, positive or negative.  It could explain the shift they found, but not necessarily.  They hope to figure this out to at least some degree, and be able to tell us more in a few weeks.

In short: the two problems together might give a shift of 60 nanoseconds in the right direction and explain their original unexpected result, but this is not yet known to be the case.  For all we know right now, there could be another experimental problem which is the real cause of the 60 nanosecond shift.  The mystery of the 60 nanosecond shift is not resolved.  

Added for clarity and emphasis: That said, there is currently no credible evidence that neutrinos travel faster than light.

We also learned a lot more, mainly from a German newspaper article that readers translated for us (translation in the first comment on this post), about this “loose wire”, or much more accurately, problematic optical cable.  It wasn’t loose.  But it had a job to do, and how well it did its job turned out to be very sensitive to exactly how it was oriented.  Its job was to bring a timing signal — a periodic flash, basically — into a box that converted the flash into an electronic signal, which went from there into OPERA’s main clock (which is the one that had a miscalibrated oscillator.)  What the OPERA folks discovered — and this wasn’t obvious, apparently, and took some “detective work” to find — is that if this cable wasn’t oriented just right, not all the light would get into the box, and that would cause the box to fire its electronic signal a bit late — tens of nanoseconds too late.  [Thanks to expert readers who left comments over the weekend, we’ve learned a great deal more about how this works, although there’s still more to be understood.]  And this would make the expected time for the neutrinos later than it was supposed to be, meaning the neutrinos would appear to arrive early.  But they don’t know how the fiber was oriented during the experiment — they didn’t know about this problem, so they weren’t monitoring the fiber, and it may have shifted around over the three years of the experiment — so they don’t know how big this effect was while the experiment was running.

In short, this was not just some crappy loose wire.  It was quite a bit more subtle than that, and much harder to find.  And it is very hard now to diagnose its effects.

Now is that the whole story?  Maybe not.  As I emphasized in an update to Friday afternoon’s post (and as three of my readers also pointed out), there is something deeply mysterious going on.  Both of the problems that OPERA has uncovered would be expected to be unstable.

  • The oscillator was at some point measured to be calibrated; now it is not properly calibrated.  What happened?  When did this change?  Before the experiment started?  After it ended?  During it?
  • And any delay caused by the optical fiber was very sensitive to how the fiber was oriented.  But was the effect of the fiber constant throughout the entire experiment?!?  It is hard to believe that the orientation of the fiber didn’t change at all over the period of three years (2009, 2010, 2011) during which the original version of the OPERA experiment was carried out.   Simply jostling it during maintenance would have been enough to cause a timing shift.

Naively, then, we would have expected that if the fiber and/or clock had something to do with the problem, the result obtained by OPERA would not have been the same across all three years (but it was!), and/or that the version of the experiment done during two weeks in October and November of 2011, using much shorter neutrino pulses, would have given a different result from the original one (but it did not!)

So what’s going on?  Is there some good reason that the fiber, or the fiber and the clock together, would give a stable 60 nanosecond shift across three years?  Or are the fiber and the clock not actually responsible, perhaps because their effects were actually smaller than feared?   Could some other large and still unknown problem in fact be responsible for causing a stable 60 nanosecond shift?

Unless I’m totally missing the point, these mysteries must all be obvious to the OPERA folks and must be bothering them a lot.

No matter how well the OPERA experimenters are able to estimate the size of the combined effect of these two problems, the only way to fully resolve these mysteries is to fix the known problems and re-run the experiment (in May).   If OPERA then finds no shift remaining, they can conclude that they probably found the cause of their anomalous result.  If there is still a shift, then either there’s some other unknown problem that’s responsible or they’re still measuring apparently-faster-than-light neutrinos.  But other experiments (BOREXINO, ICARUS and LVD) will be making their own measurements at the same time, so they’ll either get the same shift (suggesting a real physics effect) or no shift (suggesting OPERA has an additional problem) or perhaps all different shifts (which would suggest this measurement is even harder than it already appears!)

So I think we’ll be talking about OPERA at least through May — and don’t be surprised if new problems turn up with the measurements made by the other experiments, delaying the results, so perhaps this will continue all summer before it is resolved.  But, umm… I’m told that Warren Buffet suggests you not invest in stocks that depend on Einstein being overthrown in 2012.

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48 Responses

  1. What i do not realize is in fact how you’re not really a lot more neatly-appreciated than you might be now.
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  2. Come now. Before the OPERA experiment the presumption was there were no superluminal neutrinos. And these recent revelations should rightly restore the prior state of affairs. The burden of proof rests with those who would claim otherwise.

    1. The interview was before the errors were announced. The commentary on the errors is from the interviewer, not Ereditato.

  3. For any M-theorists reading this: The point is as follows: M-theory predicts gravity, non-abelian gauge theory, and SUSY. M-theory with the infinite nature hypothesis predicts SUSY in the form of particles, some of which explain dark matter. M-theory with the finite nature hypothesis predicts SUSY in the form of symmetry principles within Wolfram’s automaton. When Fernández-Rañada explained the Pioneer anomaly as anomalous gravitational acceleration of clocks, he ignored M-theory and MOND. If you study his analysis and assume that both M-theory and MOND are correct, then you get the Rañada-Milgrom effect, at least approximately.

  4. http://www.astro.umd.edu/~ssm/mond The MOND pages (McGaugh)
    Empirical evidence indicates that MOND shows that something is wrong with the equivalence principle, GRT, and Newtonian gravitational theory. Experimental gravitationalists need to seize this golden moment in the history of physics.

  5. Matt: Thank you for being very patient with me. My impression is that Steven Weinberg and Sheldon Glashow think that I am a crackpot (THEY COULD BE CORRECT!). It might be that Prof. Fernández-Rañada regards me as a crackpot. See http://vixra.org/pdf/1203.0016v1.pdf “Anomalous Gravitational Acceleration and the OPERA Neutrino Anomaly (Updated)”.
    In reply to an e-mail query, Professor Glashow kindly provided (Nov. 18, 2011 CE) a list of 31 questions:
    “1) why is the sm group su(3)xsu(2)xu(1)?
    2) why are there 6 quarks?
    3) why are there 6 leptons?
    4-13) why are quark masses and mixings what they are?
    14-23) why are lepton masses and mixings what they are?
    24-26) why are the three gauge couplings what they are?
    27) what’s the origin of neutrino masses?
    28) Is there a std. model higgs boson? where?
    29) what breaks electroweak symmetry?
    30) why is the cosmological const so small?
    31) are neutrinos superluminal?”
    I strongly believes that question 31 is answered in the negative and completely explained by the Rañada-Milgrom effect.

  6. Matt: I know the difference between muon neutrinos and neutralinos, I merely made a mistake like saying malaria when I meant dengue fever. When I use the term Seiberg-Witten theory I merely mean M-theory in its conventional form. There is M-theory which is what I call Seiberg-Witten M-theory or M-theory with the infinite nature hypothesis. I advocate modified M-theory with the finite nature hypthesis (THIS THEORY DOES NOT YET EXIST!). The Rañada-Milgrom effect is 100% precisely defined — the problem is it might be merely approximately correct. I say that Milgrom, McGaugh, and Kroupa have amassed overwhelming empirical evidence in favor of MOND. If MOND is correct, then Newtonian gravitational theory is slightly wrong, GRT is slightly wrong, and the equivalence principle is slightly wrong.

  7. Matt: Your point that I don’t understand M-theory, Seiberg-Witten theory, or neutralinos is 100% correct provided that M-theory with the infinite nature hypothesis is correct. However, I claim that overwhelming empirical evidence shows that the Rañada-Milgrom effect is APPROXIMATELY correct irrespective of what the true quantum gravitational theory is. ADMITTEDLY, THIS DOES SEEM CUCKOO.

    1. Yep. It sure does.

      MOND is a serious theory with quality people behind it. It’s almost certainly wrong, but it’s legitimate in that at least there are equations that make some sense and one can try to test it experimentally. The experts already know this; you’re not telling them anything new.

      Meanwhile, if you can’t keep neutrinos and neutralinos straight, how can we trust you to keep anything straight?

      By the way, could you please define Seiberg-Witten theory, for our edification? What type of problem were they trying to solve when it was invented?

  8. Matt: Your point about “what an easy way … to win a Nobel prize.” YES, YES, YES!!! Any experimentalists who read this should think very carefully about the Rañada-Milgrom effect. Experimentalists should have discovered the Rañada-Milgrom effect 20 years ago.

  9. If the M-theorists are correct about M-theory, then the Rañada-Milgrom effect is not really correct, it is merely approximately correct and some weird theory involving Fermi pairing of neutralinos might explain the Rañada-Milgrom effect. This is what I meant about neutralinos. How does M-theory explain MOND? This is a big problem for M-theory.

  10. “… it is very clear that they ignored it. Wisely, as it would not affect fast particles at the relevant time scales and accelerations.” MOND in the guise of the Rañada-Milgrom effect does not affect the NEUTRINOS — it throws off the GPS TIMING.

    1. I’m afraid your big message on MOND is inappropriately long and off topic, and it also makes it clear you don’t understand M theory, or Seiberg-Witten theory, or neutralinos. So I can’t approve it.

      You’ve made your point about timing for now though. I haven’t checked GPS timing and MOND, but there are plenty of reliable experts on MOND, and I’ve never heard one suggest that the GPS system’s success or failure could be used (as you are suggesting) to test whether MOND is correct. Indeed, if you were correct, experimentalists (including some I know personally) would be piling all over each other to do the experiment; what an easy way that would be to win a Nobel Prize, to use an existing satellite system and simply compare it with an atomic clock! So my guess is that your claim has, in fact, already been checked and refuted by the experts.

  11. One thing is clear: the OPERA team (as well as the Gravity Probe B science team) totally ignored Milgrom’s MOdified Newtonian Dynamics (MOND).
    My analysis is that the results of Milgrom, McGaugh, and Kroupa prove that the Rañada-Milgrom effect is approximately valid for low gravitational accelerations, and the facts about gravitational lensing prove that the Rañada-Milgrom effect is approximately valid for high gravitational accelerations.

  12. Matt, the argument CERN management should have claimed this was an OPERA experiment responsibility doesn’t work. Half of the measurements – both distance and time – were done by CERN people. CERN surveyers used GPS to pinpoint the source location, specifically for this experiment. CERN’s beams-department engineers (Javier Serrano) worked with the OPERA team to provide a travel time measurement between the source at CERN and a point just before the OPERA detector’s electronics, using accurate GPS receivers. This included timing the proton beams’ interactions at CERN, and timing the creation of intermediate particles eventually decaying into neutrinos (see the fairly reliable Wikipedia entry: http://en.wikipedia.org/wiki/Faster-than-light_neutrino_anomaly) OPERA’s time calibration was rechecked by a CERN engineer (in addition to the national labs). CERN also modified their CNGS beam (clearly affecting other experiments) to allow OPERA to repeat their experiment. CERN provided more than just a neutrino beam, they allowed modifications to their facility (installing new timing equipment) and lent their engineering expertise.

    1. I don’t think I agree with your point. CERN people may have participated in the work, sure. But that’s very different from bearing responsibility and standing behind the result.

      When I write papers, I often get assistance from other people. But if someone gives me some assistance on a paper that I write, but doesn’t actually sign off on the paper’s result, I am not going to blame them, nor should anyone blame them, if my result proves wrong, even if it is due to their mistake. I put the paper together start to finish, so it’s my job to check what they did, not their job to check what I did.

      In the end, the OPERA people who signed the OPERA paper (and not everyone from OPERA did) have the responsibility to check everything the CERN people did, as well as everything that the OPERA people did. That’s the way it works in science. That’s why the OPERA people are checking their results (and the CERN people are not doing that, except possibly when requested by the OPERA people.) By the same token, CERN modified the CNGS beam on request from the OPERA people. OPERA is calling the shots here; CERN is granting requests and assisting. That’s appropriate for a supporting laboratory.

      A scientific experiment involves a very long set of steps. Just because a few people from CERN participated in a few of the steps does not make them responsible. Responsibility lies with those who thought through and tried to check the entire chain of steps. Those are the members of the OPERA collaboration, and not non-OPERA members of CERN.

      Had CERN made an error which OPERA failed to catch — which might still prove to be the case — you could argue they both bear a measure of responsibility. Fine. I won’t entirely disagree.

      But OPERA, and NOT CERN, was responsible for the entire set of steps, including the cable and the clock. CERN bears zero responsibility for these items, and bears zero responsibility for the claim that these items had been properly checked.

  13. There is more in Science on this. The connector is coax and screwed in. What they did was check what happens when the connector is unscrewed a bit. It introduces an extra delay, with the value depending on how much the connector is unscrewed and the strength of the pulse. As far as I can make out, there is no apriori reason to believe the connector was indeed loose to begin with. This doesn’t seem as big an issue as the initial reports had it. If one goes about pulling and pushing things out, one definitely will find ways to pry things loose enough to produce the needed 60 ns discrepancy.
    So looks like we are back to square one–either OPERA is right and we have new physics, or there is an experimental error waiting to be either discovered or implicitly proved with a refuting replication. Note that assuming a connector stayed exactly and precisely loose enough to produce the same delay across many years is an impossible explanation; the simpler explanation is the connector stayed tight throughout. The tight state is its stable state.

    1. A small correction – the connection is coax and plugged in (not screwed in). So they unplugged it a bit to check (didn’t unscrew it).

    1. David, it´s the first time I read the paper, thanks. I lament not having any new of Prof. Kroupa and his theory. I congratulate that we are along a similar line of investigation. To explore where the force of gravity is around the FTL neutrinos, that is an astonishing case, seems a good idea.

  14. Matt,

    I’ve re-read one of your first posts about OPERA where you express concerns about mixing systemic and statistical errors which I share. Do they still do it in their estimates of the effects of these newly discovered problems?

    Also, how do these issues affect the main core experiments of OPERA?

    1. Since they don’t understand their newly identified problems clearly, they haven’t given an updated statement of their uncertainties. We’ll probably get that in a few weeks.

      I don’t think these issues affect the neutrino oscillation experiments that form OPERA’s main program. The timing requirements for that program are much less severe.

      1. I think the nature of the optimal beam for the speed measurement and oscillation detection is different. For speed measurement they prefer a short-pulse version, and for oscillation detection something which generates large numbers of neutrinos every spill. I think their repeat this March/May is going to use the short-pulse version, so the oscillation detection is going to be on hold for the speed repeat experiment. Actually all experiments at LNGS using the CNGS beam would be on hold, I guess.

    2. I could expect that of journals, but the people in charge of funding, might not necessary be old physicists, but accounts with sci fi leanings. For instance NASA’s breakthrough propulsion got funded, dispute being a magnet for barn pot physics, so neutrino physics might still get more not less funding. Even without superlumality neutrinos are still fascinating with key links to dark matter, the problem of generations and the weak nuclear force. I really hope funding doesn’t dry up, leaving the statistics allowing both the OPERA superlumal result and convensional Einstein relavity both allowed for neutrinos would be leaving too much of a hole in physical science.

  15. Human nature being what it is I expect the following:

    1) Given the “embarrassment” of OPERA, expect funding (where it hasn’t already been committed) required for other labs to conduct similar tests on high energy muon-neutrinos to dry up. Watch for Japan to drop out of the ‘race’ (and I use that term ironically) to measure neutrino velocity.
    2) Where funding for testing by other labs has been committed, do not expect any test results to be released publicly unless they are in accord with sub-light neutrinos. Results indicating sub-light neutrinos will be publically announced and released very quickly. However, any apparent finding of FTL neutrinos will be under “continuing analysis”.
    3) With nothing to lose at this point, and everything to gain, only OPERA can ‘vindicate’ itself. They, and they alone, are likely to quickly release the results regardless of what they find.

    Just my opinion of course…

  16. Well between the OPERA measurement and the year delay from broken solder joints, its been quite a debacle for CERN. Hope the Higgs measurement holds up, or tax payers might not fund any more experiments. I have to admit to now, being too biased to have a clear view on the measurements. When the first FTL measurement came in, I immediately tied it to a extra force generated by a U(1) axial guage on neutrinos, which i’ve (cautiously) believed in for 5 years,and got a instant mechanism for FTL neutrinos from it, by combining the Scarnhurst speed up for photons in a Casmir Vacuum, and the reduction in the number of frequency modes in a material where there a background sea of slow moving neutrinos in matter (which i need to balance out the charges on nucleons). So now the experimentist don’t believe in FTL any more, I still got a mechanism for it, that doesn’t want to dissapear. Since i like the symmetry, i’ll bet that OPERA will still see FTL neutrinos when they redo the experiment with the optic fiber fully plugged in. But I think i’ll be in the minority in this.

  17. Well , who are we to decree that faster than light is forbidden ? how about space being digital/quantized ? then faster than light is NOT forbidden !!
    what if light itself having variable speed thru time ?
    As NO existing theory describe reality as it is then how dare we to instruct nature how to behave ? how can tiny creature on a tiny planet in a tiny universe — compared to totality of existence– dare to decide what reality is or is not ? i am not against science for sure , but any science that enclose reality in the prison of human imagination is leading human imagination and creativity itself to ultimate perdition.

  18. Dear Matt. , Dear Friends : It would be very wise to transcend the phenomenon and go beyond it , going beyond we then can see the human mind , asking , seeking , wondering , feeling …….and here we find the true meaning of all , faster than light or not this is not the problem , the real point is the mind beyond who can grasp existence , a space-time , a theory , an idea , a concept …..here my friend matt. is the true knowledge , knowledge far above and beyond physical science.

    1. This is a science website, not a philosophy website. There is a place for such discussions, but this website (and in particular the comments to this scientific discussion) is not such a place.

  19. Sorry, I’m a “West Wing” nut (a television drama in the USA). The moral of an episode, which revolved around a failing space probe, was this: “Kids, don’t be afraid to go to the blackboard because you think you’ll make a mistake. Just look at how the big guys do it. It’s not whether you made a mistake, it’s what you learned, and that you had the courage to try.”

    1. There is indeed a lesson here. The OPERA folks don’t look nearly as bad to scientists as they do to non-scientists.

      No scientists have said to me, or written in the comments, that the OPERA people are bad scientists because they made a mistake. In fact a lot of us are impressed by how difficult an experiment it was and how tough it was to poke a hole in what they’d done. [And they found these problems themselves, without outside help.]

      Scientists tend to be angry that the OPERA people allowed such a media frenzy to take place over a preliminary result, making the whole scientific community and scientific process look bad.

      1. “Scientists tend to be angry that the OPERA people allowed such a media frenzy to take place over a preliminary result, making the whole scientific community and scientific process look bad.”

        I fully agree, but they are not the only ones to blame here. I still can’t understand why CERN got involved in this, this must have been high management decision to take active part in media coverage of OPERA announcements. Well, that was wrong decision, close to PR disaster – in the eyes of general public of course, not in scientific community. The only thing they should do was to keep telling everyone that it’s not their experiment and they have no comments. Then they would be on the safe side. And now public image of this institution may be quite heavily damaged – and without any real reason.

      2. In the age of blogs, I doubt that they could have done much to avoid it…
        The rumor was already out before the press conference, and let’s face it, physicists that wouldn’t talk with everybody willing to listen about such an outrageous result are animals as rare as a shy stage actress. CERN and OPERA probably thought that “taking the matter in their own hands” and explaining the result could have prevented speculations even more baseless by journalists who learned of the affair by word of mouth.
        Obviously, the fatal error in this reasoning is the assumption that journalists actually listen to somebody….

        1. Agreed. Clearly there’s a limit to what you can do when you say “Well, yes, it would be revolutionary if true, BUT YOU MUST REALIZE IT PROBABLY ISN’T TRUE”, and your interviewer writes an article in which you are said to have described the result as “revolutionary”.

          To be fair, many in the media did get the message that scientists as a whole thought the result very implausible.

          But there’s also the issue of what people read or remember of the media’s news articles. Do they read just the headline and the first paragraph? If so, all those cautions in the fifth paragraph won’t help.

  20. there is no doubt the majority of the media mishandled reports about the OPERA problems, and yet I still see the (albeit optimistic) possibility that the media and public at large may learn some pretty valuable lessons about how experimental science (not just physics) works: the general tale of scientists measuring something exceptional and unexpected and then trying very hard to find some technical problems in their own experiment because they can’t quite believe it themselves (discovering some technical difficulties in the process that were non-trivial to foresee) must be a very common story in science; I personally underwent something similar repeatedly in the biology lab, I think every scientist did, although of course not on the same level of importance that the Einstein connection put OPERA. I think this could prove an important glance behind the curtains of science for the general public

    1. It is indeed a very common story indeed; I have seen it dozens of times. But the problem is that the majority of the public is reading/hearing mainstream media, and uninformed but noisy bloggers, more than it is reading interpretation by people who really understand how science is done. So I am not yet convinced these lessons, which would indeed be valuable, are likely to be learned. More likely is that people will come to the conclusion that scientists don’t know what they’re doing (and so will have another reason not to pay any attention to those climate scientists who obviously don’t know what they’re doing either.)

  21. Matt, you are right, the mystery of the 60 nanosecond shift is not resolved. Basically MINOS, OPERA and ICARUS are facing and irregularity or anomaly related, in my opinion, to the gravitational pull caused bay neutrinos from Geneva to Gran Sasso. As relativity says a gravity field curves light and matter. If neutrinos cause the gravitational anomaly no matter how the OPERA team fits the software and the hardware that the irregularity will remain. Nevertheless we should wait for next measurements.

  22. What I don’t get is why in all the descriptions I’ve seen there appears to be only one signal channel for timing? I’m certain it’s more expensive to provide more redundancy, but almost any extra hardware that would allow more comprehensive auditing of experimental results would be cheaper than what OPERA is going through now. The verifiability of the timings is clearly critical for the experiment. Was there more redundancy in the design than has so far been apparent?

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