Please create an account to participate in the Slashdot moderation system

 


Forgot your password?
Close
typodupeerror
×
Opera Science

Superluminal Neutrinos, Take Two 98

Posted by Soulskill from the now-with-infinitely-more-scrutiny dept.
Coisiche writes "To address the many responses to their original findings, the OPERA team who reported the detection of faster-than-light neutrinos is starting a new and improved version of their experiment. 'The neutrinos that emerge at Gran Sasso start off as a beam of proton particles at CERN. Through a series of complex interactions, neutrino particles are generated from this beam and stream through the Earth's crust to Italy. Originally, CERN fired the protons in a long pulse lasting 10 microseconds (10 millionths of a second). ... [In the new experiment], protons are sent in a series of short bursts — lasting just one or two nanoseconds, thousands of times shorter — with a large gap (roughly 500 nanoseconds) in between each burst. This system, says Dr Bertolucci, is more efficient: "For every neutrino event at Gran Sasso, you can connect it unambiguously with the batch of protons at CERN," he explained.'"
This discussion has been archived. No new comments can be posted.

Superluminal Neutrinos, Take Two More

Superluminal Neutrinos, Take Two

Comments Filter:

  • Congrats to the Opera team (Score:3, Funny)

    by Anonymous Coward on Friday October 28, 2011 @08:05AM (#37867568)

    I knew browsers were getting fast, but faster than light?

    • Re:Congrats to the Opera team (Score:5, Funny)

      by lpp ( 115405 ) on Friday October 28, 2011 @08:09AM (#37867628) Homepage Journal

      It's not for general use, rather it's primarily a development tool. As has been shown time and time again, the earlier you catch bugs, the lower the cost required to fix them. Now, with faster than light browsing, you can see the bugs on your website before you've even coded it. As a result, you simply don't code the bug in the first place and save a lot of time rewriting poor CSS and markup.

    • I knew browsers were getting fast, but faster than light?

      I downloaded the nightly build last night and was getting frustrated as it kept returning pages I didn't request. I felt better this morning though, I needed those pages today.

    • Well a least we know one of FireFox's new features coming up in two years!

  • The only thing to arrive early in Italy (Score:5, Funny)

    by captainpanic ( 1173915 ) on Friday October 28, 2011 @08:07AM (#37867600)

    ... is a neutrino.

    Oblig and not even so related xkcd: http://xkcd.com/282/ [xkcd.com]

  • This new experiment seems much more suited to examining the speed of neutrinos. Can't wait to hear the results.

    • Re: (Score:2)

      by hazydave ( 96747 )

      Hopefully this time they also properly account for all of the relavitistic effects due to using GPS satellites as a time base. In the first experiment, they apparently did not account for shortening of distances on earth from the satellite's reference frame. They could prove they have properly corrected for this by sending the neutrions both E->W and W-> East. If the numbers don't match, there's still a problem.

      • Hopefully this time they also properly account for all of the relavitistic effects due to using GPS satellites as a time base. In the first experiment, they apparently did not account for shortening of distances on earth from the satellite's reference frame. They could prove they have properly corrected for this by sending the neutrions both E->W and W-> East. If the numbers don't match, there's still a problem.

        Lol you say that like the equipment producing the neutrinos and detecting the neutrinos is easy to move around...

      • Re: (Score:2)

        by AJWM ( 19027 )

        Actually, the (detected) neutrinos go mostly NW -> SE, and GPS sats being in inclined orbits, go both NW -> SE and SW -> NE, and you need at least three of them to determine a position.

        The paper on relativistic effects of moving GPS satellites was a good idea, but not quite as explanatory as it claimed to be.

  • Applied particle physics? (Score:3)

    by eggstasy ( 458692 ) on Friday October 28, 2011 @08:20AM (#37867714) Journal

    I've always found particle physics fascinating, though I won't claim to understand any of it.
    I'm disappointed that people are so vehemently against nuclear reactors these days that Germany is shutting some of them down.
    And, of course, we're not in a hurry to use nuclear weapons either.
    Radiation therapy has been a good application, but I would like to believe it will eventually be replaced by something less aggressive and more specific. Super-heavy atoms are really cool, but they're always so unstable we can barely measure them.
    What other practical applications can we hope to achieve?
    Will fusion be cleaner than fission and more publicly acceptable?
    Inquiring minds want to know.

    • Re:Applied particle physics? (Score:5, Funny)

      by Anonymous Coward on Friday October 28, 2011 @08:31AM (#37867820)

      I'm disappointed that people are so vehemently against nuclear reactors these days that Germany is shutting some of them down.

      Yeah? Just wait until Germany gets hit with a tsunami, like Japan did. That decision won't seem so dumb then.

      • Re: (Score:1)

        by Soft ( 266615 )

        Yeah? Just wait until Germany gets hit with a tsunami, like Japan did. That decision won't seem so dumb then.

        Switzerland is an even better example on that point. :-) They too are heading towards shutting down their nuclear reactors.

      • Well, I'm a factual person, not an emotional one, as such, I'm hardly ever afraid of anything.
        So let's examine the facts:
        1) The rest of the world is not Japan, or the Ring of Fire
        2) Germany, in particular, has one of the lowest earthquake hazard rates in the world
        3) Hills, where cities were built in the dawn of time, are safe from floods and invaders. Can't go wrong with 100m of solid rock.
        4) Any place that's sufficiently inland is safe from a tsunami. The rest of the world is not an island.
        5)....
        6) Profit!

    • Will fusion be cleaner than fission and more publicly acceptable?

      Well, a lot of people seem to think so.

      But they're mostly wrong. Fusion will produce neutrons, which will produce radioisotopes of the containment vessel, if nothing else.

      Which means the problem of "nuclear waste" won't actually go away with fusion. It'll just be different sorts of waste.

      • Re: (Score:1)

        by Anonymous Coward

        in fact, the halftime of the (longest lived) nuclear waste produced in fusion reactors is around 80 years. i.e. the waste is effectively controllable.

        furthermore, there can be no disasters with a fusion reactor. the natural tendency of the system is to stop (and cool down), thus any malfunction leads to the reactor halting.

    • Re: (Score:1)

      by ianalis ( 833346 )

      FYI, particle physics is high-energy physics and different from nuclear physics. CERN deliberately does not engage with nuclear physics.

    • Radiation therapy is actually on its way to becoming less aggressive and more specific. For example proton beam radiotherapy, while not yet widely available, is able to conform much closer to the target tumor while sparing much more healthy tissue than traditional xray treatments. Full disclosure: I'm a former proton radiation patient and now work for a medical physics department at a hospital which delivers the treatment.

  • Good to see the scientists are being so disCERNing.

  • Helpful but not that helpful (Score:5, Informative)

    by JoshuaZ ( 1134087 ) on Friday October 28, 2011 @08:23AM (#37867752) Homepage

    This is helpful but not that helpful. There are at this point a variety of potential explanations for what went wrong in the OPERA experiment. These include mismeasuring the tunnel length, issues with the clock calibration, and issues with the statistical analysis among other issues. It is important to note that while the OPERA group is double checking most of these issues, this experiment only really helps deal with a single problem, the statistical analysis of the neutrinos. If they are associated to individual bursts, the statistical test will be much simpler. So even if this still gets the same result, this won't be that strong evidence that there's something real going on here.

    A better replication attempt is that which is being done by MINOS http://en.wikipedia.org/wiki/MINOS [wikipedia.org], the equivalent experiment at Fermilab in the US. One reason that OPERA was paying careful attention to the arrival times (when their main interest was actually in measuring neutrino oscillation) was that MINOS had earlier reported data that tentatively suggested that some neutrinos might be going too fast. Now that OPERA has done their work, MINOS is working on doing a more detailed analysis that should be out by around February.

    Overall, I still think that there's a mistake here, but it is interesting to see how long this is taking to find where the mistake was. The apparent initial sprint by physicists to find the error is turning into a marathon. The data though still needs to be somehow reconciled with the fact that neutrinos from SN 1987a (a supernova that occurred close to Earth and whose light and neutrinos reached Earth in 1987 ahref=http://en.wikipedia.org/wiki/SN_1987Arel=url2html-7691 [slashdot.org]http://en.wikipedia.org/wiki/SN_1987A> had the neutrinos arrive when conventional theory predicted them, that is a few hours before the light. This isn't due to neutrinos traveling faster than the speed of light, but due to the fact that neutrinos are produced at the way beginning of a supernova in the core and then fly out with a headstart because they can easily avoid most of the matter in the star but the light takes time to get through the star. But, if the neutrinos traveled faster than light to the extent OPERA data suggests then SN 1987A neutrinos should have arrived years earlier.

    There are some other possibilities that would reconcile the two claims. For example, it is possible that neutrinos actually travel faster in a denser medium. This would be really weird. It is also possible that the reactions we think produce neutrinos actually produce a very short lived tachyon which itself decays into a neutrino. This starts running afoul of Occam's razor, but would explain why one would see too much velocity in the OPERA setting but not from the supernova. This hypothesis is actually also pretty easily testable: one needs to use a shorter distance for one's neutrino detectors and see if the apparent velocity goes up.

    Overall, I still suspect that this is a fluke or error of some kind. But I really hope it isn't. This could be the Michelson–Morley experiment of our error, the first anomaly which leads to a glimpse of some fantastically deeper understanding of the universe. But I really wouldn't bet on it.

    • Re:Helpful but not that helpful (Score:5, Funny)

      by jfengel ( 409917 ) on Friday October 28, 2011 @08:41AM (#37867922) Homepage Journal

      This could be the Michelson–Morley experiment of our error

      There's a Freudian slip for ya.

    • Re: (Score:1)

      by mburns ( 246458 )

      AZSquib found the problem - uncalibrated 100MHz timers. The master clock only served to obscure the drift of these ordinary Ethernet timers.

    • The article talks about them removing some of the systematic errors, not just doing the experiment in a new form.

    • Re: (Score:1)

      by srees ( 1290588 )
      It's known that gravity affects light. Perhaps gravity's impact on neutrinos is less than that on light, and thus the mass of the star going supernova kept the light back slightly from the neutrinos. I wonder if the scientists in this test adjusted for the relative effect of the target moving. If two beams of light traveling in opposite directions could observe each other's speed, they'd think the opposing beam was going double the speed of light. Likewise, the rotation of the Earth during the measurement

      • Re: (Score:2)

        by Sir_Sri ( 199544 )

        Alas I don't have time to fully pick apart the relativity argument (which is wrong btw, they appear at the speed of light relative to each other, time dilation and all that), but they are actually sourcing the neutrinos themselves. Since photons are massless, but neutrinos might have mass they should be more effected by gravity, or equally, but that's one of the questions. Photons self interact, it's possible neutrinos self interact less than photons, meaning the 'speed of light' we observe is actually no

      • GR-based explanations (with or without extra dimensions) have been considered, and they don't work: http://arxiv.org/abs/1109.6312 [arxiv.org] http://arxiv.org/abs/1109.5687 [arxiv.org]

    • Re:Helpful but not that helpful (Score:5, Informative)

      by bcrowell ( 177657 ) on Friday October 28, 2011 @12:27PM (#37870976) Homepage

      This is helpful but not that helpful. There are at this point a variety of potential explanations for what went wrong in the OPERA experiment. These include mismeasuring the tunnel length, issues with the clock calibration, and issues with the statistical analysis among other issues.

      The distance measurement and clock calibration were initially proposed by people outside the calibration as simple explanations, but at this point it's clear that they are simply not credible explanations. Contaldi http://arxiv.org/abs/1109.6160 [arxiv.org] suggested early on that the clocks could have been put out of synchronization by transport, but the OPERA team clarified that they were calibrated after transport, through GPS. Van Elburg, who is apparently completely ignorant of how GPS works, proposed that it could be a special-relativistic time dilation effect due to the orbital motion of GPS satellites relative to the lab frame. The distance measurement would have to be off by 20 meters in order to explain the 60 ns shift, and that's completely implausible.

      All of the really obvious, stupid explanations have been ruled out -- which is not a big surprise, since 170 PhD's in the OPERA collaboration had their reputations on the line, so they were highly motivated to detect any really dumb blunders. So the remaining sources of error really are things in the general category you're referring to as statistical analysis. Some serious suggestions have been made that seem viable: (1) There could be a correlation between the direction of emission of the neutrinos and the time at which they were emitted during the 10 us beam pulse. (2) There could be a correlation between the distribution of energies in the neutrino beam and the time of emission. (3) There could be spillover from previous beam pulses. (4) There could be subtle effects in the electronics such as dead-time. Every single one of these possible errors is eliminated in the design that they're currently running, with 1- or 2-ns pulses instead of 10 us ones.

      A better replication attempt is that which is being done by MINOS http://en.wikipedia.org/wiki/MINOS [wikipedia.org] [wikipedia.org], the equivalent experiment at Fermilab in the US. One reason that OPERA was paying careful attention to the arrival times (when their main interest was actually in measuring neutrino oscillation) was that MINOS had earlier reported data that tentatively suggested that some neutrinos might be going too fast. Now that OPERA has done their work, MINOS is working on doing a more detailed analysis that should be out by around February.

      The trouble with MINOS is that (1) they have poorer statistics, (2) the energy is lower than the one used in CNGS (and the FTL effect, if real, is energy-dependent), and (3) OPERA's design was closely based on MINOS's, so subtle sources of error that are present in OPERA are likely to be present in MINOS as well. A better candidate for totally independent checking of the OPERA result is Tokai to Kamioka (T2K).

      But, if the neutrinos traveled faster than light to the extent OPERA data suggests then SN 1987A neutrinos should have arrived years earlier.

      If you believe both the OPERA result and other results at lower energy, then there is an energy-dependence in the speed that is different than that predicted by special relativity. (If neutrinos were tachyons, which is consistent with SR, then OPERA neutrinos would have been slower than SN1987A neutrinos, because tachyons go slower when you put more energy in them. This is the opposite of what is actually claimed observationally.)

      There is essentially no hope for reconciling this observation with theory, unless we are in the middle of a major scientific revolution where everything is so weird that we just can't make sense of it yet -- which I don't find plausible. If neutrinos really went faster than light, then they would emit

    • Re: (Score:3)

      by Prune ( 557140 )
      Listen bro, if we assume that only muon neutrinos are tachyonic, there's a trivial explanation as to why the neutrinos from SN 1987a did not arrive faster: lorentz-violating neutrino oscillations. First of all, the tachyonic neutrino's speed would only be very slightly above c, and every time it changes, it's speed would be slightly below c. Note that any initial acceleration of a tachyonic neutrino while going through the star's gravity field (due to its imaginary mass it goes along a spacelike geodesic) w

      • Re: (Score:2)

        by Zouden ( 232738 )

        This is the best comment that ever started with "Listen bro".

      • if we assume that only muon neutrinos are tachyonic, there's a trivial explanation

        This possibility has been investigated, and it doesn't work: if different neutrino flavors had different limiting velocities of propagation, then neutrino oscillations would go away when the neutrinos propagated over long distances, because the wave-packets would split up. http://arxiv.org/abs/1109.5682 [arxiv.org] This is contrary to previous observations.

    • I think the OPERA team, judging from the various responses to criticisms, have been very thorough in avoiding the most obvious mistakes, such as GPS frame dragging etc.

      My initial thought is that perhaps the GPS distance calculated between the two points uses an arc, i.e. along the curve of the earth and that the neutrinos traveling along a straight line caused the error, but I'm pretty sure that something that obvious would have been noticed after they repeated the experiment 15'000 times.

  • when you can just go back in time and recheck your results?

  • What bothers me about this, is that there is a certain likelihood, that the reason why the story was released so early, was not so much that the researchers hoped to get more people to review their findings, as that they might have hoped to get the necessary funding and/or intstrument time for this experiment faster (or even get it at all).

    Mind you, running the experiment the way they now do is certainly the right thing to do if you want to measure the speed of neutrinos. The former experiment struck me as

    • Re: (Score:1)

      by whovian ( 107062 )

      Perhaps, but the reality is that when applying for funding, the lack of first paper/proof-of-concept or even preliminary data can count against you. I'm more inclined to look at media sources as a source of misrepresentation and hyperbole.

    • What bothers me about this, is that there is a certain likelihood, that the reason why the story was released so early, was not so much that the researchers hoped to get more people to review their findings, as that they might have hoped to get the necessary funding and/or intstrument time for this experiment faster (or even get it at all).

      What bothers me about your comment, is that there is a certain likelihood, that the reason why you would post such a ridiculous statement, with so many unnecessary and misplaced commas, is that you really don't understand how projects like this operate (and couldn't be bothered to do any research before mouthing off).

      Instrument time is scheduled months and years in advance for these projects. They're modifying their experiment and using instrument time that was already allocated. I suspect that there's

      • Exactly.

        The most exciting phrase to hear in science, the one that heralds new discoveries, is not “Eureka” but “That’s funny...”
        —Isaac Asimov (1920–1992)

  • How can they be sure? (Score:5, Funny)

    by GoNINzo ( 32266 ) <GoNINzoNO@SPAMyahoo.com> on Friday October 28, 2011 @09:16AM (#37868374) Journal
    They changed the outcome by observing it! This is just another example of Big Physics ruining the results of science by observing the location of particles.

    • Perhaps we could apply this concept to the government - Change the outcome by close observation

  • Every time this is discussed on slashdot, we get comments from people asking if neutrinos are tachyonic, why did the supernova SN 1987a ones not arrive earlier. The answer is very simple: neutrino oscillations, where only some (probably muon type) are superluminal. http://arxiv.org/abs/1109.6055 [arxiv.org] PS I still think experimental error is the most likely explanation, but I'm tired of hearing the invalid criticism of the SN 1987a observations. Stop it, it's getting fucking annoying!
    • Technically you are right but Occam's Razor gets pretty dull if you have to hypothesize that one type of neutrino is superluminal and another is not. Other than mass, aren't electrons, muons, and tau particles pretty much identical? Shouldn't their associated neutrinos be, too? So you are right that SN 1987a doesn't prove that muon neutrinos aren't superluminal, but it, combined with the similarities of the leptons and their neutrinos is still a strong indicator that they aren't.

      • Re: (Score:2)

        by Prune ( 557140 )
        It's been known ever since Popper's time that the sort of inductive reasoning implicit in "is still a strong indicator that they aren't" is not scientifically valid: http://en.wikipedia.org/wiki/Critical_rationalism [wikipedia.org]

      • Re: (Score:2)

        by AJWM ( 19027 )

        Other than mass, aren't electrons, muons, and tau particles pretty much identical? Shouldn't their associated neutrinos be, too?

        You do realize that it only takes a difference in mass for particles to be tachyonic or non-tachyonic, right? Sure, that difference is by a factor of i, but it's still just the mass.

    • The tachyonic mass needed for to get the OPERA result, is easily calculated and its root minus one time 120 MeV, which is impossible as the weak decays show the masses of even the tau neutrinos to be less than a KeV, and the others less than 1eV. So tachyonic neutrinos are definitely not consistent with both OPERA ad SN1987a.

      ---

      Alternative neutrino speed theory [blogspot.com]

      • Re: (Score:2)

        by Prune ( 557140 )
        Can you post the calculation of the 120 MeV? Keep in mind the possibility of the beam crossing something that we haven't noticed yet, if you know what I mean. Depending on how well the new MINOS results agree with this, we shall see.

        On a related topic: how to build a neutrino communications device that is fairly compact (as in, portable)?
        • Sure, see ArVix: 1190.5917v2, but its,

          Standard particles E = mc^2 /sqrt( 1- v^2/c^2), a tachyon has v>c, and an imaginary mass, m = sqrt(-1) * m(tachyonic), so we get:

          E = m(tachyonic) c^2 / sqrt( v^2/c^2 -1 )

          So, m ~ sqrt (2 (v-c)/c ) * E

          E was around 20-40 GeV (Same speed was measured for all velocities, which doesn't look like a tachyon, in particular doesn't fit with the tachyon equation above).

          And (v-c)/c ~ 2.5 *10^-5

          That Gives m = 120 Mev, (or in the paper with error bounds, m~ (110 to 1

  • Superluminal Neutrinos, Take Two, and call me yesterday morning.

    Sorry

  • Given their fine control over the neutrino pulses, it sounds like the they should be able to modulate the stream---e.g., change the interval between pulses---to transmit a signal. This would give speed-of-light, noise free communication in a straight line through the earth (reducing the latency for US-australia communication by a factor of pi). It's a bit expensive for general use, but would be an amazing science-fiction level achievement.

  • How this article has nothing to do with Opera, the browser. Despite the /. icon for this story being the trademark red O.

  • The Michelson–Morley experiment doesn't show that there is no aether , only that we are not moving relatively to it. Particles that have more mass than neutrinos have more inertia to the expansion of space. Since space is expanding uniformly in all directions (like a rising cake), no matter what direction you look, the expansion is the same, the neutrinos get pulled with less resistance through the expanding space than the rest, so they arrive faster.

Slashdot Top Deals

Statistics are no substitute for judgement. -- Henry Clay

Close