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Faster-Than-Light Neutrino Puzzle Claimed Solved by Special Relativity

361 points by dhimes 15y ago

thegrossman 15y ago
This is an almost trivial application of special relativity. It was be absolutely shocking if the dozens of scientists involves in the neutrino experiment didn't take this into account.
- dhimes 15y ago
  That's what I was thinking too- this may be destined to become a problem in a relativity class (perhaps a little above Modern Physics, though). But then maybe I don't fully understand the subtleties.
- Udo 15y ago
  I'd file this under "systematic measurement error", and the team specifically said that something like it was the most likely cause for the results. They also said that if neutrinos really were FTL, we'd have observed this effect much earlier (for example when we started measuring supernova radiation bursts). So, the article's hypothesis is a very good candidate for a real flaw in the experiment's design. The scientists probably didn't take this into account because they assumed their setup already compensated for all kinds of clock drift... I wouldn't call this an epic failure just yet, because even if this turns out to be the root cause it's a pretty standard type of mistake as far as science experiments go. That's why we have independent reviews, and that's why they are necessary.
  - dhimes 15y ago
    They also said that if neutrinos really were FTL, we'd have observed this effect much earlier (for example when we started measuring supernova radiation bursts). I am seriously doubtful that these neutrinos are traveling faster than light, but I've also been skeptical of this argument since it was presented. It would be pretty hard to have observed this if they weren't looking for it because they would have to sift through old data. For example, for SN 1987A the FTL neutrino event would have preceded the visible light neutrino event by over four years. They could go through all of the old data, to be sure, but they would have to specifically have had to be looking for something which they think fundamentally is impossible in order to find something like this. So, if these events were even recorded at all, it's certainly not clear to me that they would have done this (at the time of the FTL announcement, that is- of course, they should be doing it now). it's a pretty standard type of mistake as far as science experiments go Yes, but when one makes it this far it is big news. No matter what I give props to the scientists to publicly invite the scrutiny they did. That took balls.
- deleted 15y ago
  [deleted]
- gruen 15y ago
  In 1999, NASA lost a $300MM Mars probe due to a metric/imperial conversion oversight. Shocking, yes; unheard of, no.
  - crocowhile 15y ago
    Reference: http://en.wikipedia.org/wiki/Mars_Climate_Orbiter#Communications_loss http://en.wikipedia.org/wiki/Mars_Climate_Orbiter#Communicat...
  - Eliezer 15y ago
    But then they found the error afterward. These physicists were looking for an error, hard.
- Confusion 15y ago
  They obviously did take all kinds of relativistic effects into account. It's not like they forgot about relativity. It's just that they may have overlooked a higher-order effect that is usually neglected because it is so small. Something like overlooking magnetism when looking at electricity (magnetism is a relativistic effect of moving electrical charge, but since the forces involved are so small, they are easy to miss and neglect)
  - mrb 15y ago
    Confusion, funny how you said weeks ago that "relativity cannot possibly be relevant in explaining the time difference" - http://news.ycombinator.com/item?id=3030735 http://news.ycombinator.com/item?id=3030735 - and you downvoted me who was suggesting a relativist effect could explain the 60ns difference (although I was wrong about which particular effect)... coughitoldyousocough ;)
    - jrockway 15y ago
      His name is Confusion...
    - drzaiusapelord 15y ago
      Maybe the dude read a few articles or had time to think. Using one's posting history as a "gotcha" because we humans aren't allowed to change our minds for some reason, seems like a really, really odd thing to do.
      - mrb 15y ago
        Yes. But it doesn't justify his insulting replies ("I will not explain why: please actually read..."). Next time he will hopefully be more polite.
    - Confusion 15y ago
      What I meant, but I agree I didn't clearly say as much, was that completely forgetting about relativity could not possibly be the answer. At the time I was slightly annoyed at the large number of lay people who implied as much (which implies the team was being a bunch of idiots, which to seems typical of the less than respectful average attitude people have towards scientists). Those people certainly didn't have subtle effects like these in mind. So I shouldn't post when I'm annoyed, because then I tend to bark at things that are not what they appear to be.
- jcfrei 15y ago
  my thoughts exactly - my guess is that the editor wanted to point out this potential source of an error, because his readers were likely to understand it. to me the error seems to be too trivial for an experiment of that magnitude.
- drzaiusapelord 15y ago
  How many of these guys are GPS satellite engineers? It sounds like they falsely assumed that the GPS system would take care of all relativistic effects and they can just use absolute time for measurement. The GPS system was not remotely designed for this level of accuracy. The issue here could really be a misconception of how well GPS works and what it was designed to do. GPS, like all technology, has a distinct difference between theory and practice and is also engineered for certain use cases. It may be that no one really thought about this stuff until now because we're talking such tiny increments of time over such large distances. Regardless, its early in the game to know whats going on, but I'd be really surprised if suddenly neutrinos were FTL and no one noticed until sometime this year. This is starting to look like another case of super-smart over-specialized eggheads making assumptions and not seeing the big picture, like when NASA/Lockheed lost the Mars Climate Orbitor over imperial to metric conversions.
  - starwed 15y ago
    >This is starting to look like another case of super-smart over-specialized eggheads making assumptions and not seeing the big picture What a fucked way to spin this -- the group asked for outside help in explaining their results and finding any mistakes.
    - drzaiusapelord 15y ago
      If these guys were humble researchers unsure of their results, perhaps RUNNING TO THE MEDIA AND SCREAMING ABOUT BREAKING THE LIGHT BARRIER should have been agenda item #8484 not #1. Seriously, if you're claiming you're doing FTL, asking for outside help isn't some noble act, its pretty much required. The idea that these guys are infallible and systemic errors never happen is incredibly naive. Christ, remind me never to get between nerds and their starship Enterprise fantasies.
      - krschultz 15y ago
        Did you read the original press release?
      - 15y ago
- pmjordan 15y ago
  "Almost trivial"? You're vastly exaggerating. I'm pretty sure most physics graduates would get problems of special relativity as applied to rotating (i.e. accelerating) systems completely wrong, as it's usually just not taught. Yep, someone doing the experiment should have ideally spotted it, but it's already an extremely complex system, so I'm not surprised they didn't.
- bermanoid 15y ago
  This is an almost trivial application of special relativity. This is even less than a trivial application of special relativity, it's literally a third grade "distance = rate x time" problem: Skipping over the relativistic stuff, which is quite frankly unnecessary (or rather, it's necessary, but the CERN authors apparently already included the corrections), the only two equations of import are (re-named vars for lack of LaTeX): 1) time_baseline = dist_baseline / c 2) time_observed = dist_baseline / (c+v) where v is the speed of the satellite. In other words, if two things are moving towards each other, then you should use the combined velocity to compute the time. Duhhh... Now, the fact that the difference in these formulas turns out to almost exactly explain away the problem is certainly suggestive, I'll be honest about that. But if this was all there was to the story, it would be massively embarrassing for someone at CERN, this is the type of error I mentally ruled out immediately because these people should be way too careful to be making elementary screwups like this. This is the type of error that freshmen lose points for on a mechanics 101 test, not one that eludes dozens of physicists working around the clock for a month. So I'm skeptical here; it's not that the author of this paper is wrong (though there are credibility red flags in the paper, even beyond the fact that he's not a physicist [he's a computer guy], like the fact that he defines gamma as the inverse of the commonly used relativistic quantity, something that indicates only a passing familiarity with the field), it's that I'm not sure that the CERN guys could reasonably be assumed to have made this mistake. Then again, maybe everyone else looking over the work also assumed that they'd dotted their i's, and didn't bother checking the trivial stuff. It's certainly happened before...
  - VladRussian 15y ago
    if formula using (c+v) explains the situation while we may be sure that the CERN physicists calibrated their systems using various SR formulas with "gamma" (i.e. 1/(sqrt(1-v2/c2)) ), that would be an interesting comment on SR :) [especially considering that the Michelson-Morley experiment confirming the constant and isotropic "c" - the foundation of SR - wasn't calibrated using the SR's rules following from such properties of "c"].
jasondavies 15y ago
Link to arXiv paper: http://arxiv.org/abs/1110.2685 http://arxiv.org/abs/1110.2685
- qntm 15y ago
  I've never seen "photon" spelled with an F before.
  - themgt 15y ago
    I think English isn't the author's first language: The authors of the OPERA paper [5] seem to include a correction for the Lorentz transformations, but they not correct for the change in scenario. And because they project back the time of provided by the moving clock to the baseline they seem to incorrectly assume that the outcome of their experiment should be equivalent to that using a clock in the baseline reference system
    - eldina 15y ago
      Still a little odd, as the Dutch are generally considered to be the best non-native speakers of English in Europe.
      - mauro_oto 15y ago
        Foton is spanish for Photon, I guess it's the same way in Dutch. (It is)
        mladenkovacevic 15y ago
        I'd imagine Photon is spelt Foton in pretty much any phonetic language in the world (or as they would say fonetic lol)
        kachnuv_ocasek 15y ago
        You mean fonetik?
kiwidrew 15y ago
But the GPS satellites and receivers already correct for these relativistic effects. Specifically: "The engineers who designed the GPS system included these relativistic effects when they designed and deployed the system. ... Further, each GPS receiver has built into it a microcomputer that (among other things) performs the necessary relativistic calculations when determining the user's location." [1] [1] http://www.astronomy.ohio-state.edu/~pogge/Ast162/Unit5/gps.html http://www.astronomy.ohio-state.edu/~pogge/Ast162/Unit5/gps....
- themgt 15y ago
  I think it's more subtle than that - it's due to the motion of the satellites relative to the experiment (i.e. the direction of the neutrino path), not to the individual ground stations
- thegrossman 15y ago
  Relativistic effects are only taken into account when determining the position of the satellite itself, and the rate of it's clock. It can't compensate for the effect in the linked-to article (namely, the fact that the distance and flight time between the neutrino source and destination is shorter according to the satellite, versus an observer on the ground) because that effect depends on the specifics of the experiment. Consider this: If you flipped the location of the neutrino source and destination, you'd actually get the reverse effect (neutrinos would appear to be going slower than light). So it's up to observers on the ground to compensate for relativistic effects of this nature. (As I mentioned in another comment, I would be shocked if they didn't already do that)
  - onemoreact 15y ago
    Neutrino's are hard to detect and even harder to generate in detectable quantites. So for now we have exactly one location and one path in the world where we can both generate and detect them at a reasonable distance. Also, GPS satilites don't orbit in one direction you need 3 to quickly get an accurate posisiton so they use a wide range of orbits to minimize the number needed. http://www8.garmin.com/aboutGPS/ http://www8.garmin.com/aboutGPS/ Which is something the article seems to miss.
martincmartin 15y ago
If true, this just goes to show how many effects you need to take into account when dealing with numbers that are 2 thousands of a percent. Effects that can normally be ignored because they're in the noise, turn out to be in the signal instead.
martinkallstrom 15y ago
And Einstein snickers high up in the heavens, his hair as white and woolly as the cloud upon which he partakes his afternoon slumbers.
- martinkallstrom 15y ago
  "Fools", he mutters under his breath, "Neutrinos flying faster than light... I pity your indolence." With wiry fingers he taps his pipe on his knuckles, flinging burnt tobacco beyond the edges of the cloud. "Ah well," he sighs, connecting his iPhone to his Macbook Air, "time to install iOS 5. I bet those servers are not running as red hot any longer".
macaroni 15y ago
could someone please explain this, i wish i could say i get it, but i am so confused. i don't understand, are they not using gps just to synchronize the clocks on both ends? what does it matter if in orbit the distance seems shorter or longer if observed (viewed) from the satellites (is this what they are saying?)?
- themgt 15y ago
  The simplest way I can (try to) understand it is to imagine a line drawn between CERN and Gran Sasso. From the GPS point of view(consider the GPS satellites as stationary), this line is moving approximately in a Gran Sasso->CERN direction, and is therefore very slightly shorter than what the researchers on the ground calculated
- podperson 15y ago
  Let's suppose you're trying to time a 100 yard dash based on sound. Someone fires a gun, the race starts, and when the first runner crosses the finish line another gun is fired, you determine the elapsed time. There are obvious things to correct for -- e.g. if you're standing at the finish line the sound from the finish line will take 1/3 of a second (roughly) to get to you, so you need to adjust your calculation. Now suppose that you are standing off on a barge during the race. You know the distance to the start and finish lines but ignored the drift of the barge because you figured it was insignificant. We're talking 60 nanoseconds. The satellites are moving at tens of thousands of miles an hour.
  - podperson 15y ago
    "the sound from the _start_ line" :-)
alain94040 15y ago
Wouldn't an obvious test involve sending something else than neutrinos through the same path, and measure that they are slower?
- sp332 15y ago
  The path goes through the earth, so they can't send things on the same path. The detector is far underground to protect it from interference.
ck2 15y ago
Why don't they have synchronized atomic clocks on the ground?
- perlgeek 15y ago
  They do, and they used a mobile atomic clock to compare the times. The problem is that both locations are in different, accelerated frames of reference, so reasoning about time in those frames of reference can become non-trivial.
  - quijote 15y ago
    Apparently they didn't use a mobile atomic clock but a mobile gps clock to compare the times: http://operaweb.lngs.infn.it/Opera/publicnotes/note134.pdf http://operaweb.lngs.infn.it/Opera/publicnotes/note134.pdf So it appears they synchronized both timing sources with an orbiting clock, and the critique from this dutch guy seemingly stands.
DanielBMarkham 15y ago
Okay. This should be an easy one but somehow I'm getting stumped. I understand the difference in frames between the GPS satellites and the ground, but the sats themselves are fixed to each other, right? And the ground stations are also fixed to each other. Each pair is in a separate frame. But the measurement was on the ground, and the ground stations are not accelerating relative to each other, not from the satellites. So is this saying that the ground stations set their clocks initially wrong because of their relative movement to the satellites? If so, wouldn't this be proven out by comparing the neutrinos time to the time of a photon?
- InclinedPlane 15y ago
  I haven't read the article yet. However, the ground stations are deeper in the Earth's gravity well than the satellites. That is equivalent to acceleration in relativity.
  - route66 15y ago
    And the ground stations have a different potential with respect to each other, so their reading of elapsed time could differ. That's what I understood from another article on that subject.
  - lutorm 15y ago
    That's negligible.
    - hebejebelus 15y ago
      When it comes to 60 nanoseconds, I'm not sure anything is negligible.
      - VladRussian 15y ago
        The GR effects here is on the scale of 1e-15s, i.e. several orders of magnitude less than observed 6e-8s. 7 orders of magnitude is "negligible" as GP correctly stated.
daimyoyo 15y ago
Until the faster than light result can be recreated in an independent experiment, I am treating this like cold fusion. Neat result and absolutely deserving of further investigation, but not definitive.
- Jach 15y ago
  I don't really get why you're being downvoted to oblivion, that's a great stance to take on science in general. So much media buzz is made over n=1 things; you can cut out a lot from your information diet by ignoring things until they get replication. If special relativity is wrong, we'll find out in due course, and the current counter-evidence against special relativity is hardly a dent compared to the massive evidence in favor (both theoretical and experimental). Just a few days ago I discovered this paper: http://arxiv.org/abs/1005.4172 http://arxiv.org/abs/1005.4172 They assert Events as the only fundamental object, not space, not time. Then: "by asserting that some events have the potential to be influenced by other events, but that this potential is not reciprocal, we can describe the set of all events as a partially ordered set or poset, which is typically known as a causal set" and from there they derive Special Relativity.
  - jholman 15y ago
    Actually, while I fundamentally agree with the "ignoring things until they get replication" proposal, I think there's an impracticality there, due to the way information dissemination works. There will be no flurry of HN links about this when someone replicates it (even assuming, for the sake of argument, that neutrinos really can be fired FTL, all of current physics is wrong, etc etc). Maybe a single link. It just won't have the network effect; too much of the collective audience's interest has already been consumed. And there'll definitely be no HN links when the third and fourth teams replicate it. Even if that's a wrong claim for this hypothetical result about relativity, consider yesterday's "forced exercise and Parkinson's" link ( http://news.ycombinator.com/item?id=3106799 http://news.ycombinator.com/item?id=3106799 ). That result is _completely_ immature (the rat experiments tested something very different from the human experiments, there has only been one human experiment, the causal story is all conjecture, etc), and there's no _way_ we're gonna hear about it when it's usefully mature (i.e. after ten more studies). (Epistemologically, I think the current result is not far removed from alternative medicine - there's some evidence, but no elegant pattern of evidence across multiple contexts, and no rigorous-but-failed attempts at falsification.) It's an interesting subject, and an interesting research programme, and I want to know about things like this, but it's too early to take this into account when making lifestyle tradeoffs. So it seems to me that my choices are kind of ugly: I can read a LOT of cutting-edge stuff, and read all the follow-ups, knowing that most of the ground-shakers won't actually pan out. Or I can wait 20 or 50 or more years until it starts showing up in undergraduate textbooks. Or... I don't know, there must be other options, but I don't know what they are. Another option is reading Malcolm Gladwell et al, which I think is generally viewed with a certain exasperation by the genuinely knowledgeable? Is there a blog or magazine or whatever, that popularizes science, with this slightly delayed view? "Exciting science news from 10 years ago, complete with a decade of 20/20 hindsight!"
crizCraig 15y ago
What's the general consensus on whether or not this was actually debunked? http://www.wepolls.com/p/3873491 http://www.wepolls.com/p/3873491
deleted 15y ago
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zb 15y ago
This paper: http://tycho.usno.navy.mil/ptti/1996/Vol%2028_16.pdf http://tycho.usno.navy.mil/ptti/1996/Vol%2028_16.pdf states that "the time rate is appropriate to observers on the surface of the rotating earth, that is, in the ECEF". I'm interpreting that to mean that the issue raised in the OP is not correct, but I am by no means an expert in relativity. Interestingly, the paper also states ('Missing Relativity Terms?', pp. 195-197) that there has been confusion in the past caused by people thinking the time is measured in the ECI frame. It shows that the uncorrected-for relativistic effects have an error on the order of only 2-3mm for a stationary observer on the earth's surface (the same is not true for e.g. other satellites). 'In short, there are no "missing relativity terms."'

361 points by dhimes 15y ago

This is an almost trivial application of special relativity. It was be absolutely shocking if the dozens of scientists involves in the neutrino experiment didn't take this into account.

dhimes 15y ago
That's what I was thinking too- this may be destined to become a problem in a relativity class (perhaps a little above Modern Physics, though). But then maybe I don't fully understand the subtleties.
Udo 15y ago
I'd file this under "systematic measurement error", and the team specifically said that something like it was the most likely cause for the results. They also said that if neutrinos really were FTL, we'd have observed this effect much earlier (for example when we started measuring supernova radiation bursts). So, the article's hypothesis is a very good candidate for a real flaw in the experiment's design. The scientists probably didn't take this into account because they assumed their setup already compensated for all kinds of clock drift... I wouldn't call this an epic failure just yet, because even if this turns out to be the root cause it's a pretty standard type of mistake as far as science experiments go. That's why we have independent reviews, and that's why they are necessary.
- dhimes 15y ago
  They also said that if neutrinos really were FTL, we'd have observed this effect much earlier (for example when we started measuring supernova radiation bursts). I am seriously doubtful that these neutrinos are traveling faster than light, but I've also been skeptical of this argument since it was presented. It would be pretty hard to have observed this if they weren't looking for it because they would have to sift through old data. For example, for SN 1987A the FTL neutrino event would have preceded the visible light neutrino event by over four years. They could go through all of the old data, to be sure, but they would have to specifically have had to be looking for something which they think fundamentally is impossible in order to find something like this. So, if these events were even recorded at all, it's certainly not clear to me that they would have done this (at the time of the FTL announcement, that is- of course, they should be doing it now). it's a pretty standard type of mistake as far as science experiments go Yes, but when one makes it this far it is big news. No matter what I give props to the scientists to publicly invite the scrutiny they did. That took balls.
deleted 15y ago
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gruen 15y ago
In 1999, NASA lost a $300MM Mars probe due to a metric/imperial conversion oversight. Shocking, yes; unheard of, no.
- crocowhile 15y ago
  Reference: http://en.wikipedia.org/wiki/Mars_Climate_Orbiter#Communications_loss http://en.wikipedia.org/wiki/Mars_Climate_Orbiter#Communicat...
- Eliezer 15y ago
  But then they found the error afterward. These physicists were looking for an error, hard.
Confusion 15y ago
They obviously did take all kinds of relativistic effects into account. It's not like they forgot about relativity. It's just that they may have overlooked a higher-order effect that is usually neglected because it is so small. Something like overlooking magnetism when looking at electricity (magnetism is a relativistic effect of moving electrical charge, but since the forces involved are so small, they are easy to miss and neglect)
- mrb 15y ago
  Confusion, funny how you said weeks ago that "relativity cannot possibly be relevant in explaining the time difference" - http://news.ycombinator.com/item?id=3030735 http://news.ycombinator.com/item?id=3030735 - and you downvoted me who was suggesting a relativist effect could explain the 60ns difference (although I was wrong about which particular effect)... coughitoldyousocough ;)
  - jrockway 15y ago
    His name is Confusion...
  - drzaiusapelord 15y ago
    Maybe the dude read a few articles or had time to think. Using one's posting history as a "gotcha" because we humans aren't allowed to change our minds for some reason, seems like a really, really odd thing to do.
    - mrb 15y ago
      Yes. But it doesn't justify his insulting replies ("I will not explain why: please actually read..."). Next time he will hopefully be more polite.
  - Confusion 15y ago
    What I meant, but I agree I didn't clearly say as much, was that completely forgetting about relativity could not possibly be the answer. At the time I was slightly annoyed at the large number of lay people who implied as much (which implies the team was being a bunch of idiots, which to seems typical of the less than respectful average attitude people have towards scientists). Those people certainly didn't have subtle effects like these in mind. So I shouldn't post when I'm annoyed, because then I tend to bark at things that are not what they appear to be.
jcfrei 15y ago
my thoughts exactly - my guess is that the editor wanted to point out this potential source of an error, because his readers were likely to understand it. to me the error seems to be too trivial for an experiment of that magnitude.
drzaiusapelord 15y ago
How many of these guys are GPS satellite engineers? It sounds like they falsely assumed that the GPS system would take care of all relativistic effects and they can just use absolute time for measurement. The GPS system was not remotely designed for this level of accuracy. The issue here could really be a misconception of how well GPS works and what it was designed to do. GPS, like all technology, has a distinct difference between theory and practice and is also engineered for certain use cases. It may be that no one really thought about this stuff until now because we're talking such tiny increments of time over such large distances. Regardless, its early in the game to know whats going on, but I'd be really surprised if suddenly neutrinos were FTL and no one noticed until sometime this year. This is starting to look like another case of super-smart over-specialized eggheads making assumptions and not seeing the big picture, like when NASA/Lockheed lost the Mars Climate Orbitor over imperial to metric conversions.
- starwed 15y ago
  >This is starting to look like another case of super-smart over-specialized eggheads making assumptions and not seeing the big picture What a fucked way to spin this -- the group asked for outside help in explaining their results and finding any mistakes.
  - drzaiusapelord 15y ago
    If these guys were humble researchers unsure of their results, perhaps RUNNING TO THE MEDIA AND SCREAMING ABOUT BREAKING THE LIGHT BARRIER should have been agenda item #8484 not #1. Seriously, if you're claiming you're doing FTL, asking for outside help isn't some noble act, its pretty much required. The idea that these guys are infallible and systemic errors never happen is incredibly naive. Christ, remind me never to get between nerds and their starship Enterprise fantasies.
    - krschultz 15y ago
      Did you read the original press release?
    - 15y ago
pmjordan 15y ago
"Almost trivial"? You're vastly exaggerating. I'm pretty sure most physics graduates would get problems of special relativity as applied to rotating (i.e. accelerating) systems completely wrong, as it's usually just not taught. Yep, someone doing the experiment should have ideally spotted it, but it's already an extremely complex system, so I'm not surprised they didn't.
bermanoid 15y ago
This is an almost trivial application of special relativity. This is even less than a trivial application of special relativity, it's literally a third grade "distance = rate x time" problem: Skipping over the relativistic stuff, which is quite frankly unnecessary (or rather, it's necessary, but the CERN authors apparently already included the corrections), the only two equations of import are (re-named vars for lack of LaTeX): 1) time_baseline = dist_baseline / c 2) time_observed = dist_baseline / (c+v) where v is the speed of the satellite. In other words, if two things are moving towards each other, then you should use the combined velocity to compute the time. Duhhh... Now, the fact that the difference in these formulas turns out to almost exactly explain away the problem is certainly suggestive, I'll be honest about that. But if this was all there was to the story, it would be massively embarrassing for someone at CERN, this is the type of error I mentally ruled out immediately because these people should be way too careful to be making elementary screwups like this. This is the type of error that freshmen lose points for on a mechanics 101 test, not one that eludes dozens of physicists working around the clock for a month. So I'm skeptical here; it's not that the author of this paper is wrong (though there are credibility red flags in the paper, even beyond the fact that he's not a physicist [he's a computer guy], like the fact that he defines gamma as the inverse of the commonly used relativistic quantity, something that indicates only a passing familiarity with the field), it's that I'm not sure that the CERN guys could reasonably be assumed to have made this mistake. Then again, maybe everyone else looking over the work also assumed that they'd dotted their i's, and didn't bother checking the trivial stuff. It's certainly happened before...
- VladRussian 15y ago
  if formula using (c+v) explains the situation while we may be sure that the CERN physicists calibrated their systems using various SR formulas with "gamma" (i.e. 1/(sqrt(1-v2/c2)) ), that would be an interesting comment on SR :) [especially considering that the Michelson-Morley experiment confirming the constant and isotropic "c" - the foundation of SR - wasn't calibrated using the SR's rules following from such properties of "c"].

jasondavies 15y ago

Link to arXiv paper: http://arxiv.org/abs/1110.2685 http://arxiv.org/abs/1110.2685

qntm 15y ago
I've never seen "photon" spelled with an F before.
- themgt 15y ago
  I think English isn't the author's first language: The authors of the OPERA paper [5] seem to include a correction for the Lorentz transformations, but they not correct for the change in scenario. And because they project back the time of provided by the moving clock to the baseline they seem to incorrectly assume that the outcome of their experiment should be equivalent to that using a clock in the baseline reference system
  - eldina 15y ago
    Still a little odd, as the Dutch are generally considered to be the best non-native speakers of English in Europe.
    - mauro_oto 15y ago
      Foton is spanish for Photon, I guess it's the same way in Dutch. (It is)
      - mladenkovacevic 15y ago
        I'd imagine Photon is spelt Foton in pretty much any phonetic language in the world (or as they would say fonetic lol)
        kachnuv_ocasek 15y ago
        You mean fonetik?

kiwidrew 15y ago

But the GPS satellites and receivers already correct for these relativistic effects. Specifically: "The engineers who designed the GPS system included these relativistic effects when they designed and deployed the system. ... Further, each GPS receiver has built into it a microcomputer that (among other things) performs the necessary relativistic calculations when determining the user's location." [1] [1] http://www.astronomy.ohio-state.edu/~pogge/Ast162/Unit5/gps.html http://www.astronomy.ohio-state.edu/~pogge/Ast162/Unit5/gps....

themgt 15y ago
I think it's more subtle than that - it's due to the motion of the satellites relative to the experiment (i.e. the direction of the neutrino path), not to the individual ground stations
thegrossman 15y ago
Relativistic effects are only taken into account when determining the position of the satellite itself, and the rate of it's clock. It can't compensate for the effect in the linked-to article (namely, the fact that the distance and flight time between the neutrino source and destination is shorter according to the satellite, versus an observer on the ground) because that effect depends on the specifics of the experiment. Consider this: If you flipped the location of the neutrino source and destination, you'd actually get the reverse effect (neutrinos would appear to be going slower than light). So it's up to observers on the ground to compensate for relativistic effects of this nature. (As I mentioned in another comment, I would be shocked if they didn't already do that)
- onemoreact 15y ago
  Neutrino's are hard to detect and even harder to generate in detectable quantites. So for now we have exactly one location and one path in the world where we can both generate and detect them at a reasonable distance. Also, GPS satilites don't orbit in one direction you need 3 to quickly get an accurate posisiton so they use a wide range of orbits to minimize the number needed. http://www8.garmin.com/aboutGPS/ http://www8.garmin.com/aboutGPS/ Which is something the article seems to miss.

martincmartin 15y ago

If true, this just goes to show how many effects you need to take into account when dealing with numbers that are 2 thousands of a percent. Effects that can normally be ignored because they're in the noise, turn out to be in the signal instead.

martinkallstrom 15y ago

And Einstein snickers high up in the heavens, his hair as white and woolly as the cloud upon which he partakes his afternoon slumbers.

martinkallstrom 15y ago
"Fools", he mutters under his breath, "Neutrinos flying faster than light... I pity your indolence." With wiry fingers he taps his pipe on his knuckles, flinging burnt tobacco beyond the edges of the cloud. "Ah well," he sighs, connecting his iPhone to his Macbook Air, "time to install iOS 5. I bet those servers are not running as red hot any longer".

macaroni 15y ago

could someone please explain this, i wish i could say i get it, but i am so confused. i don't understand, are they not using gps just to synchronize the clocks on both ends? what does it matter if in orbit the distance seems shorter or longer if observed (viewed) from the satellites (is this what they are saying?)?

themgt 15y ago
The simplest way I can (try to) understand it is to imagine a line drawn between CERN and Gran Sasso. From the GPS point of view(consider the GPS satellites as stationary), this line is moving approximately in a Gran Sasso->CERN direction, and is therefore very slightly shorter than what the researchers on the ground calculated
podperson 15y ago
Let's suppose you're trying to time a 100 yard dash based on sound. Someone fires a gun, the race starts, and when the first runner crosses the finish line another gun is fired, you determine the elapsed time. There are obvious things to correct for -- e.g. if you're standing at the finish line the sound from the finish line will take 1/3 of a second (roughly) to get to you, so you need to adjust your calculation. Now suppose that you are standing off on a barge during the race. You know the distance to the start and finish lines but ignored the drift of the barge because you figured it was insignificant. We're talking 60 nanoseconds. The satellites are moving at tens of thousands of miles an hour.
- podperson 15y ago
  "the sound from the _start_ line" :-)

alain94040 15y ago

Wouldn't an obvious test involve sending something else than neutrinos through the same path, and measure that they are slower?

sp332 15y ago
The path goes through the earth, so they can't send things on the same path. The detector is far underground to protect it from interference.

ck2 15y ago

Why don't they have synchronized atomic clocks on the ground?

perlgeek 15y ago
They do, and they used a mobile atomic clock to compare the times. The problem is that both locations are in different, accelerated frames of reference, so reasoning about time in those frames of reference can become non-trivial.
- quijote 15y ago
  Apparently they didn't use a mobile atomic clock but a mobile gps clock to compare the times: http://operaweb.lngs.infn.it/Opera/publicnotes/note134.pdf http://operaweb.lngs.infn.it/Opera/publicnotes/note134.pdf So it appears they synchronized both timing sources with an orbiting clock, and the critique from this dutch guy seemingly stands.

DanielBMarkham 15y ago

Okay. This should be an easy one but somehow I'm getting stumped. I understand the difference in frames between the GPS satellites and the ground, but the sats themselves are fixed to each other, right? And the ground stations are also fixed to each other. Each pair is in a separate frame. But the measurement was on the ground, and the ground stations are not accelerating relative to each other, not from the satellites. So is this saying that the ground stations set their clocks initially wrong because of their relative movement to the satellites? If so, wouldn't this be proven out by comparing the neutrinos time to the time of a photon?

InclinedPlane 15y ago
I haven't read the article yet. However, the ground stations are deeper in the Earth's gravity well than the satellites. That is equivalent to acceleration in relativity.
- route66 15y ago
  And the ground stations have a different potential with respect to each other, so their reading of elapsed time could differ. That's what I understood from another article on that subject.
- lutorm 15y ago
  That's negligible.
  - hebejebelus 15y ago
    When it comes to 60 nanoseconds, I'm not sure anything is negligible.
    - VladRussian 15y ago
      The GR effects here is on the scale of 1e-15s, i.e. several orders of magnitude less than observed 6e-8s. 7 orders of magnitude is "negligible" as GP correctly stated.

daimyoyo 15y ago

Until the faster than light result can be recreated in an independent experiment, I am treating this like cold fusion. Neat result and absolutely deserving of further investigation, but not definitive.

Jach 15y ago
I don't really get why you're being downvoted to oblivion, that's a great stance to take on science in general. So much media buzz is made over n=1 things; you can cut out a lot from your information diet by ignoring things until they get replication. If special relativity is wrong, we'll find out in due course, and the current counter-evidence against special relativity is hardly a dent compared to the massive evidence in favor (both theoretical and experimental). Just a few days ago I discovered this paper: http://arxiv.org/abs/1005.4172 http://arxiv.org/abs/1005.4172 They assert Events as the only fundamental object, not space, not time. Then: "by asserting that some events have the potential to be influenced by other events, but that this potential is not reciprocal, we can describe the set of all events as a partially ordered set or poset, which is typically known as a causal set" and from there they derive Special Relativity.
- jholman 15y ago
  Actually, while I fundamentally agree with the "ignoring things until they get replication" proposal, I think there's an impracticality there, due to the way information dissemination works. There will be no flurry of HN links about this when someone replicates it (even assuming, for the sake of argument, that neutrinos really can be fired FTL, all of current physics is wrong, etc etc). Maybe a single link. It just won't have the network effect; too much of the collective audience's interest has already been consumed. And there'll definitely be no HN links when the third and fourth teams replicate it. Even if that's a wrong claim for this hypothetical result about relativity, consider yesterday's "forced exercise and Parkinson's" link ( http://news.ycombinator.com/item?id=3106799 http://news.ycombinator.com/item?id=3106799 ). That result is _completely_ immature (the rat experiments tested something very different from the human experiments, there has only been one human experiment, the causal story is all conjecture, etc), and there's no _way_ we're gonna hear about it when it's usefully mature (i.e. after ten more studies). (Epistemologically, I think the current result is not far removed from alternative medicine - there's some evidence, but no elegant pattern of evidence across multiple contexts, and no rigorous-but-failed attempts at falsification.) It's an interesting subject, and an interesting research programme, and I want to know about things like this, but it's too early to take this into account when making lifestyle tradeoffs. So it seems to me that my choices are kind of ugly: I can read a LOT of cutting-edge stuff, and read all the follow-ups, knowing that most of the ground-shakers won't actually pan out. Or I can wait 20 or 50 or more years until it starts showing up in undergraduate textbooks. Or... I don't know, there must be other options, but I don't know what they are. Another option is reading Malcolm Gladwell et al, which I think is generally viewed with a certain exasperation by the genuinely knowledgeable? Is there a blog or magazine or whatever, that popularizes science, with this slightly delayed view? "Exciting science news from 10 years ago, complete with a decade of 20/20 hindsight!"

crizCraig 15y ago

What's the general consensus on whether or not this was actually debunked? http://www.wepolls.com/p/3873491 http://www.wepolls.com/p/3873491

deleted 15y ago

[deleted]

zb 15y ago

This paper: http://tycho.usno.navy.mil/ptti/1996/Vol%2028_16.pdf http://tycho.usno.navy.mil/ptti/1996/Vol%2028_16.pdf states that "the time rate is appropriate to observers on the surface of the rotating earth, that is, in the ECEF". I'm interpreting that to mean that the issue raised in the OP is not correct, but I am by no means an expert in relativity. Interestingly, the paper also states ('Missing Relativity Terms?', pp. 195-197) that there has been confusion in the past caused by people thinking the time is measured in the ECI frame. It shows that the uncorrected-for relativistic effects have an error on the order of only 2-3mm for a stationary observer on the earth's surface (the same is not true for e.g. other satellites). 'In short, there are no "missing relativity terms."'