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FTL Neutrinos Explained... Maybe

Posted by Soulskill on from the a-definite-possibility dept.

The Bad Astronomer writes "A new paper, recently posted on the arXiv physics preprint server, claims to have explained the faster-than-light neutrino experiment from last month. The author claims the motion of the GPS satellite introduces a relativistic dilation that accounts for the now-infamous 60 ns discrepancy in neutrino flight time. However, I'm not so sure; the original experimenters claimed to have accounted for relativistic effects. I don't think we've seen the end of this just yet."

29 of 226 comments (clear)

  1. Having Read Both Papers by eldavojohn · · Score: 2, Interesting

    (Although I am not a physicist) I understand that this is talking about the concept of "time" from a frame of reference between the GPS satellites and the ground stations. However, the original paper's implementation did not measure time with GPS satellites (that would be silly). Instead, it used the satellites to obtain very precise distances and when they did this, they accounted for relativity. The time recording devices were atomic clocks at the locations of the facilities on the surface of the Earth. As the second article notes, they just said they did this and you assume they did it correctly. However, if they miscalculated relativity between the satellites and ground stations, it's going to be in the form of the distance being incorrectly measured -- not the actual time itself. And that distance (which would be slightly shorter than they calculated) should then result in an explanation of the nanosecond difference.

    --
    My work here is dung.
    1. Re:Having Read Both Papers by SoapBox17 · · Score: 2

      GPS already normally accounts for relativity.... nothing new there. Base on the original paper I think it's highly unlikely they mismeasured the distances. http://www.astronomy.ohio-state.edu/~pogge/Ast162/Unit5/gps.html

    2. Re:Having Read Both Papers by Dan+East · · Score: 2

      I don't understand this as well. Either this is simply a preexisting inaccuracy in all GPS readings due to relativity that has never been taken into consideration (highly unlikely), or there's something else going on that I don't grasp. I don't see how the neutrino motion relative to the motion of the satellites is a factor here, as no direct measurement between the two is being made in that way.

      One of the things the GPS system helped prove was that relativity is real and must be accounted for in systems of that sort, otherwise accuracy will suffer. So I find it very unlikely that something that fundamental was overlooked in the GPS measurements generically.

      --
      Better known as 318230.
    3. Re:Having Read Both Papers by MichaelSmith · · Score: 3, Funny

      Maybe its because GPS understands relativity well enough to get planes to the correct runway, and cruise missiles to their target, but the people who designed it didn't anticipate measuring the speed of neutrinos.

      --
      http://michaelsmith.id.au
    4. Re:Having Read Both Papers by ETEQ · · Score: 5, Interesting

      (I *am* a physicist) Actually, the original paper *did* measure time with GPS - more to the point, they use GPS to establish a common frame between the two locations. Look at Figure 5 of the OPERA paper (http://arxiv.org/pdf/1109.4897v1).

      Having said that, as other replies have noted, this kind of correction is well-understood, so while it isn't explicitly laid out as far as I can tell, it's unlikely the OPERA group screwed this up. What may well be true, though, is that there may be systemic offsets either in the GPS timing system, the implementation at Gran Sasso (they actually have a big waveguide that they run from the Earth's surface all the way to the GPS reveivers they have by their detector deep underground), or any of the myriad corrections that were needed to determine the time-of-flight baseline (although as far as I can tell they worked very hard to get this measurement right...).

      It's also rather suggestive that the author of this paper has no particle physics (or even physics) credentials. So he/she probably doesn't know the OPERA collaboration's processes very well (admittedly, these details should be in the paper, but the tradition of the community is to not do that sort of detail in announcement papers like this...)

    5. Re:Having Read Both Papers by Vellmont · · Score: 2

      The paper doesn't claim that the distances were measured incorrectly, it claims the timing was inaccurate do to special relativity (not general relativity which another poster in this thread was confused by.

      In essence, the paper makes the claim that the experiment is using GPS as a reference clock, and the reference clock (the satellite) is in motion differently, relative to the neutrino source, and detector.

      --
      AccountKiller
    6. Re:Having Read Both Papers by tftp · · Score: 5, Interesting

      60 ns translates into 18 meters at the speed of light. If the error was that large any car GPS device would be showing you as driving on some other street.

      I was working with some high precision GPS receivers, and they can place you on the map with accuracy of a couple of centimeters. The shape of the Earth is also pretty well understood now.

      One unfortunate possibility would be that the clocks are wrong. They had to move them between sites, since they weren't willing or able to synchronize them over the radio where they are (the varying propagation paths would be hard to deal with.) A more pleasing (to me) outcome would be that FTL is real.

    7. Re:Having Read Both Papers by tftp · · Score: 3, Interesting

      Not if the map is also off by 18 meters. How do they put the roads on the map in the first place? Most likely, by GPS, or whatever GPS was calibrated against when it was implemented.

      The current datum for GPS is WGS84. Locations of many places on Earth were carefully measured for centuries, using astronomy and trigonometry. I don't know if they are accurate enough to calibrate the GPS.

      A systematic, uniform error, like a translation of the entire datum, would have no effect on the OPERA experiment - however you slide or rotate the outer shell of a sphere it doesn't change the distance between two points. It would require a systematic but non-uniform error to cause this effect. I guess it is possible, since there is no explanation so far of the OPERA results. Such an error has to be location-specific and it should be invisible to the WAAS.

    8. Re:Having Read Both Papers by GryMor · · Score: 2

      Physics (and velocities) don't work like that, you can't simply sum them.

      If, in a third reference frame, 2 objects are observed to be approaching each other at .75 c, co moving observers in the frame of either object would calculate their respective closing velocity as .96 c

      The velocity addition formula is:

      s = (v + u)/(1+(v*u/c^2))

      --
      Realities just a bunch of bits.
    9. Re:Having Read Both Papers by julesh · · Score: 3, Interesting

      The word "infamous" is often used by scientists to describe problems that a large number of people have attempted to solve and have failed. I suspect that this is the sense the submitter was using it in.

  2. Garbage by Goaway · · Score: 5, Insightful

    This is another easy-to-digest paper written by someone who doesn't have the first clue about what was actually done in the experiment, trying to explain it with undergrad physics. And the press jumps on each and every one of these, no matter how bad they are.

    In this case, GPS clock synchronization to nanosecond levels is regularly done in meteorology, the relativistic effects are well known and compensated for, because it wouldn't work at all if they weren't, and the synchronization was confirmed by a non-GPS method.

    Absolutely nothing to see here.

    1. Re:Garbage by Windcatcher · · Score: 2, Interesting

      I won't call it "garbage", but otherwise I was thinking along similar lines (disclaimer -- I have a Master's in Physics but I haven't bothered to do the math). 60ns is an eternity in an experimental setup, and while the two sites are at different latitudes (and a straight-line three-space trajectory sends the neutrinos along a curved path in spacetime), I can't see earth's relatively weak gravity accounting for such a discrepancy. It's a curved 4-space path, but it's not *that* curved.

    2. Re:Garbage by tftp · · Score: 2

      They don't automatically work out the precise timing. So if one is using GPS for timing one can't just rely on the standard GPS software and calculations for timing.

      That must be bad news for manufacturers of GPS timing receivers. As matter of fact, I was working with this very receiver, it's tiny but it tells you time with 15 ns. accuracy - it is more accurate than the error in the experiment.

      But as I understand the OPERA people weren't using the GPS timing, they physically moved a synchronized clock (and compensated for the effect of moving it.)

  3. Re:Give the researcher some credit by Goaway · · Score: 3, Insightful

    I think it's fair to assume that the researcher would read the original paper before publishing a reaction to it,

    The original paper does not go into detail about the procedures, because it beyond the scope of the paper. You are supposed to go look these things up for yourself, and the person who wrote this paper very clearly didn't.

  4. Could this be quantum weak measurement? by Dr.+Spork · · Score: 5, Funny

    In case you wondered this, check out what could be the world's greatest article abstract: Can apparent superluminal neutrino speeds be explained as a quantum weak measurement?

    Seriously, it's worth clicking, and understanding the abstract doesn't require advanced physics knowledge.

  5. Re:Gut feeling by bmo · · Score: 5, Insightful

    >we know jack and shit

    This attitude is not helpful. This is part of the reason why biblical literalists get away with what they do. They say "hurp, we don't know anything at all, so you may as well believe Genesis word-for-word."

    It is anti-reason and a cop-out.

    And you cap it off with a complete misunderstanding about what a theory is.

    Your post is a load of manure, sir.

    --
    BMO

  6. Re:I hope that this is true. by geekoid · · Score: 2

    Both would be going C by any point of reference.

    --
    The Kruger Dunning explains most post on /. http://en.wikipedia.org/wiki/Dunning%E2%80%93Kruger_effect
  7. Re:I hope that this is true. by Goaway · · Score: 2

    No information can be transmitted, so causality is not violated.

  8. If neutrino were faster than light... by drobety · · Score: 2

    If neutrinos were faster than c, the neutrinos from SN1987A would have arrived "five years sooner," while they were measured arriving "3 hours before the dying star's light caught up" as expected...

    1. Re:If neutrino were faster than light... by Soupster · · Score: 2

      If neutrinos were faster than c, the neutrinos from SN1987A would have arrived "five years sooner," while they were measured arriving "3 hours before the dying star's light caught up" as expected...

      You are making the assumption that the neutrinos from SN1987A were excited to the same or higher energy level by the supernova that the LHC neutrinos were excited to. My bet is this assumption is false.

  9. bogus by bcrowell · · Score: 5, Interesting

    It's bogus. (Yes, I am a physicist.) OPERA used portable atomic clocks, which were moved to the the two labs and then synchronized via GPS (see this article). GPS thoroughly incorporates general relativity (which includes special relativity). It has incorporated GR ever since it was first built, because if it didn't, it wouldn't work. At all. No, not even well enough for hiking and driving. Here is a review article on relativity in GPS. GPS uses coordinates called Earth-Centered Inertial (ECI). These are coordinates (t,r,theta,phi), where the spatial coordinates are spherical coordinates that rotate along with the earth, and t is the time coordinate of a hypothetical observer in a nonrotating frame at rest relative to the center of the earth. General relativity is completely agnostic about what coordinate system you use, so this choice of a coordinate system is not a choice that has any physical significance; it's just a bookkeeping thing. Van Elburg assumes that GPS was constructed by people who didn't understand relativity, and therefore GPS times need to be corrected for relativistic effects. That's just completely wrong.

    --
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  10. Highly Doubtful by Roger+W+Moore · · Score: 5, Interesting

    Maybe its because GPS understands relativity well enough to get planes to the correct runway...

    GPS understands relativity well enough to require General Relativistic corrections. This paper suggests that the GPS clock is inaccurate and suffers a lag based on location which, since GPS requires accurate timing to pinpoint your location a 64ns time difference would put you 20m off your correct location. In addition the author uses a very simplistic model of GPS clock and satellite for getting the clock. I would also have assumed that the GPS clock is based on multiple satellites since it has to know your location to calculate the propagation delay and it does this by comparing one satellite clock to another.

    However the final nail in the coffin is that he doesn't know how to spell photon (it is not spelt foton!)...so I have extreme doubts that this is paper is correct. In fact I'd need to hear from a GPS expert that his simplistic model is reasonable because I don't believe that it is (but then I'm not a GPS expert!).

    1. Re:Highly Doubtful by digitig · · Score: 4, Informative

      Maybe its because GPS understands relativity well enough to get planes to the correct runway...

      GPS understands relativity well enough to require General Relativistic corrections. This paper suggests that the GPS clock is inaccurate and suffers a lag based on location which, since GPS requires accurate timing to pinpoint your location a 64ns time difference would put you 20m off your correct location. In addition the author uses a very simplistic model of GPS clock and satellite for getting the clock. I would also have assumed that the GPS clock is based on multiple satellites since it has to know your location to calculate the propagation delay and it does this by comparing one satellite clock to another. However the final nail in the coffin is that he doesn't know how to spell photon (it is not spelt foton!)...so I have extreme doubts that this is paper is correct. In fact I'd need to hear from a GPS expert that his simplistic model is reasonable because I don't believe that it is (but then I'm not a GPS expert!).

      I'm not an expert either although I have worked on GPS aircraft navigation and augmentation systems. You are right that the GPS clock is based on multiple satellites. A GPS fix needs a minimum of four satellites, and the receiver triangulates position in 4-dimensions: the three spatial dimensions and time (four unknowns, four data points). What's more, those 4 will not be in the same plane (the satellites themselves form 6 orbital planes), so the bit in the article about "The orbits of these satellites are at 20.2 106 m from the earth’s surface in a fixed planes inclined 55 from the equator with an orbital period of 11 h 58 min [3]. This implies that they fly predominantly West to East when they are in view of CERN and Gran Sasso, which is roughly parallel to the line CERN-Gran Sasso" looks to me like a fundamental misunderstanding of the satellite orbits. The satellites on which a time fix is based will not all be travelling in the same direction. It is possible to use other position information as data points, and so reduce the number of satellites needed for a fix, but I'm not sure why anybody would do that when they can improve accuracy by using all visible satellites (and anyway, even if they did use a single satellite plus accurately known spatial position, the author of the paper still wouldn't know which orbital plane the satellite used was, and so wouldn't know the direction of movement).

      --
      Quidnam Latine loqui modo coepi?
  11. Re:I hope that this is true. by Xaositecte · · Score: 2

    The reason the speed of light is an unbreakable barrier is because it would take theoretically infinite energy to accelerate anything past the speed of light. It's the place in the equation where the equations break down into infinity, and we can't predict exactly what's going on.

    If there's evidence that the speed of light isn't an absolute barrier, it means our current understanding of relativity is wrong.

  12. Re:I hope that this is true. by Goaway · · Score: 2

    That situation violates causality only for some definition of causality which is not useful.

    What matters in causality is avoiding paradoxes. You cannot create a paradox using quantum entanglement, thus there is no problem.

  13. Best joke so far by Anonymous Coward · · Score: 4, Funny

    "We don't serve faster than light neutrinos here", said the bartender. A neutrino walked into a bar.

  14. Re:What about the Tunnel? by nedlohs · · Score: 3, Informative

    Through the ground.

    Just like you don't need to remove the air in a "tunnel" between point A and point B to send a beam of light between them, you don't need to remove the rock in a "tunnel" between point A and point B to send a beam of neutrinos between then. Of course enough air will block the light as and several hundred light years of solid rock would block the neutrinos. 900km of rock however is not going to do anything, digging a tunnel would make no difference at all.

  15. Re:LIGHT WILL REDEEM YOU!!! by nedlohs · · Score: 3, Informative

    Photons don't make it though the 900km of rock.

  16. Bogus, please check the sources by xanojsp · · Score: 2

    The authors have documented their whole procedure here: http://www.ohwr.org/projects/cngs-time-transfer/wiki The author of the bogus paper assumes the people who designed GPS and those who use it in metrology labs around the world to manufacture GPS do not know anything about relativity. He also proceeds to an analysis without checking his very basic premises first with the authors of the neutrino velocity paper, or anybody close to the actual experiment. Is it that hard to check one's assumptions first?