Given current accuracy of the techniques, is it possible to identify a real, existing tunnel (stright I think) to make the direct comparison of the speed of light and of neutrinos? The hypotetical tunnel from CERN to OPERA would-be too long. If we were able to increase accuracies by two decades, then would a 7.3 Km tunnel suffice ? The 60ns difference would become around 600ps. Suppose there is such a tunnel, suppose it can be availabe to physicists. Apart from all the logistics problems of generating and detecting light and neutrinos at the two ends of such tunnel, are there other difficulties?
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Related: When the speed of light has been measured, recently? and What is the highest accuracy of measuring time differences achievable today?. Note that T2K will likely have reported in long before then and the matter may disappear. – dmckee --- ex-moderator kitten Dec 15 '11 at 15:24
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BTW--It is not clear that you are going to get a big improvement in timing accuracy as these things are set by (1) the precision to which you can match some feature (often the rising edge) of the pulses in calibration data (2) light and electronics noise in the detector and (3) any multiplicity of paths that might generate a particular signal (as in reflection in hodoscopes and light guides). Still, there are new detector technologies coming down the pipe, and perhaps some of them will be more amenable to precision time matching. – dmckee --- ex-moderator kitten Dec 15 '11 at 16:57
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Unlike neutrinos, light will be slowed down by gas in the tunnel, which would have to go through the Earth. It is much cheaper and easier to mathematically analyze the OPERA results to find their error, were they ever to release their detailed protocol, which is unlikely, because they don't seem to want the error discovered.
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Because they haven't published the detailed satellite data and correction algorithm, instead they ask the rest of the world to trust their accounting for relativistic effects related to the rotation of the Earth. I would ask them to make their GPS algoritms public. If they don't publish enough to check their GPS independently, which they haven't, they should lose their funding. – Ron Maimon Dec 15 '11 at 22:08
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1There is_no_way an international collaboration with 200 physicists is hiding anything. I am saying that not because that with so many people someone would leak something, but because in science you do not hide things. One man can be corrupt and hide everything. An international collaboration plays by the rules of established science. You don't just pull their funding because of one man who has not read all the publications. – hpekristiansen Dec 15 '11 at 22:42
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@Hans-Peter E. Kristiansen: Obviously they aren't purposefully hiding something, it not a conspiracy, it's just a collective phenomenon in large collaborations. Each person who is entrusted with this relativistic correction or that calculation, or this bit of programming has an incentive to keep his or her work as private as possible, both because this guarantees their position (nobody else knows how to do it) and because if, heaven forbids they made a mistake, they can catch and fix it themselves without anyone else finding out. Leadership must push against this tendency. OPERA's doesn't. – Ron Maimon Dec 16 '11 at 01:10
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Ron, have you ever been part of one of these organizations? I've been in half a dozen and haven't observed this behavior in any of them. There is intense internal scrutiny and competition for most parts and a fair amount of people peering over your shoulder even we you're working on a modest little corner of the experiment. Presentations at collaboration meetings can be very trying times if you aren't sufficiently prepared. – dmckee --- ex-moderator kitten Dec 16 '11 at 01:17
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@dmckee: I have not been a part of a large collaboration, and I am sure the ones you have been involved in are well run. But the OPERA collaboration published a startling impossible result, and at the same time managed to not publish just enough of their methods so that the error cannot be discovered independently. The only conclusion one can come to is that the internal process at OPERA is rotten, and that the result is not trustworthy. If there were an actual neutrino speed-of-light violation, it would have been announced with enough analysis and internal data so that anyone could check. – Ron Maimon Dec 16 '11 at 01:32
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@RonMaimon I think they are just trusting the GPS itself, not redoing calculations from scratch. I have been saying that to all intents and purposes the GPS might have redefined the meter for all we know. Geodesics does not require this level of accuracy over such large distances. – anna v Dec 16 '11 at 09:06
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I have also suggested that the last experiment measuring the velocity of light should be repeated in a straight section of the LHC vacuum tubes to confirm the velocity of light in vacuum. For all we know http://en.wikipedia.org/wiki/Speed_of_light the last 1972 laser interferometer experiment was not done in vacuum http://prl.aps.org/abstract/PRL/v29/i19/p1346_1 ; I cannot tell how relevant this would be as the paper is behind a pay wall. One would have to carefully study the experiment to see whether the value of c in vacuum was really measured. – anna v Dec 16 '11 at 09:15
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@anna v: At least the timing part of the GPS they are doing is from scratch, because they need to synchronize their clocks to better than standard precision. It is not likely that they are modelling the sattelite orbits, but they must be doing something nontrivial, nobody knows exactly what. As for c-measurement/meter-calibration uncertainties, these are known to be orders of magnitudes smaller than the effect. – Ron Maimon Dec 16 '11 at 19:01