back to article CERN boffins re-running neutrino speed test

In the wake of September’s surprising experimental results that suggested the observation of faster-than-light neutrinos, CERN has announced that it has been re-running the experiment over recent days. Since the pre-publication release of its original dataset, CERN’s data has been raked over by physicists, scientists, computer …


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  1. Richard French

    Can anyone explain why the experiment doesn't use a fibre optic loop so that the neutrinos can be received by the same facility as send them out in the first place. This would reduce the complexity of the experiment removing time anomalies (or have I missed something in my naive knowledge of physics).

    1. Wize

      Because it neutrinos, not photons.

      I shouldn't take the piss tho. Its a good idea. But I don't think they have neutrino compatable reflectors.

    2. cloudgazer

      Simple answer, because you can't constrain neutrinos to a fibre optic cable, why would you be able to? Fibre optic isn't magic - it only works on photons, and only photons of certain energies at that.

    3. Anonymous Coward 99

      Neutrino Physics 101

      Because neutrinos hardly interact with matter, you can't steer them once they have been produced. The only way the experiment works is by putting the detector in line with the beam that is being produced. Then you have to work out which neutrinos MAY have come from the source (since the universe is filled with background, ....)

    4. Mike 140

      Sorry, but yes, you have. Neutrinos aren't affected by a wave guide such as a fibre optic cable. They stop for nothing and nobody. Their path is a geodesic. With only occasional exceptions they pass through matter as though it doesn't exist.

    5. tyo.

      You can't send neutrinos through a fiber because they won't reflect on its walls. Neutrinos practically don't interact with matter, they go right through it.

    6. Yes Me Silver badge


      Can't be done. Neutrinos travel through ordinary matter such as glass without taking much notice of it; they don't obediently follow along a fibre like photons do. Most of the neutrinos that make it from CERN to Gran Sasso aren't detected, they just continue on their way; just a very few of them interact with the detector material and get recorded.

      It's quite different from the original Michelson-Morley experiment that led Einstein to figure out relativity, where the photons were indeed reflected back.

    7. Michael Chester

      Neutrinos != light

      They would just pass straight through the fiber optic cable, and there's no good way of directing them which would allow you to send them in a circle (even the detectors are inefficient, since they interact so rarely with anything)

    8. John H Woods Silver badge


      ... neutrinos won't go round a fibre optic loop. In fact they pass through pretty much everything, which is why creating a neutrino detector is such hard work.

    9. Robert E A Harvey

      I don't think you can persuade neutrinos to go round corners.

    10. Anonymous Coward 99

      Neutrino Physics 101

      Because Neutrinos hardly interact with normal matter, they cannot be steered, you have to put the detector in line with the source.

    11. Steen Hive

      Because neutrinos could pass through the walls of your 'fibre-optic' cable (and maybe right through the middle of every planet in the solar system as well) without even breaking a sweat.

    12. StevieB

      Neutrinos are not photons.

      They act in ways different to light. The ones causing all the problems have been fired through 730km of rock, the chances of them following an optical fibre are, I would suggest, slim to none.

    13. Anonymous Coward
      Anonymous Coward

      The neutrinos are not being sent along a conduit, they are literally passing through the Earth to the detector, such is their nature. This site has a good explanation

    14. John G Imrie

      Youve missed something

      Nutrinos don't flow down a fiber optic cable the way light does. The problem with nutrinos is that they are so small the pass through allmost everything. Occasionally, where occasionally is a verry small number, one hits a sub atomic particle and can be detected.

    15. Sorry that handle is already taken. Silver badge

      Neutrinos care not for earthly possessions

      Neutrinos tend not to interact with matter, and anyway they're not photons so optical fibres would be unlikely to help even if they weren't so weakly interacting.

      To give an idea of how weakly interacting there are, the solar neutrino flux at the distance of earth's orbit from the sun is on the order of 10^14/m²s, and it takes gigantic detectors built in deep underground caverns containing tens of thousands of tonnes of water to pick up even a handful of them each year.

    16. wtf is a handle


      neutrinos pass through nearly any matter. Just looked it up and said even passes through planets, wtf

    17. Graham Dawson Silver badge

      Neutrinos only interact very weakly with matter and wouldn't follow an optical fibre.

    18. Martin Gregorie

      Because a neutrino beam can't be bent.

      Photons can be made to follow an optical fibre if the angle they make with the sides of the fibre is low enough for them to all be reflected back into the cable.

      However, neutrinos are particles that barely interact with other particles enough to be detected, which is why they can travel 732 km through solid rock. The chances of reliably deflecting such a beam in a circle are approximately zero. Similarly, they carry no electric charge so magnets won't deflect them either.

      To show how unreactive neutrinos are, Its been calculated that a neutrino beam can penetrate a lightyear of solid lead without loosing more than a few percent of its brightness and they can whistle through the sun almost without noticing that it was there.

      So, as collisions don't deflect them, they can't be reflected by anything, and magnets or electric fields don't affect them, you have no choice except to design the experiment around measuring a straight beam on neutrinos.

    19. Heironymous Coward

      flogging a dead horse

      18 responses and counting, all with minor variations on the theme "neutrinos pass thru anything and are hard to detect", without any non-topical interruptions - got to be an El Reg record. Sorry to break the chain, guys :-)

    20. oldredlion

      Has any one said neutrinos won't follow a loop yet?

    21. Cirret

      Neutrinos are not photons. Neutrinos pass through matter almost as if it doesn't exist, so guiding them with optic fibre or anything else is a non-starter. I don't see why you think this would have simplified the experiment.

  2. Chris Haynes

    A new dataset is expected by the end of November

    November?! I thought these things were moving faster than the speed of light?

    1. Steen Hive

      November 30th, 1492

    2. Anomalous Cowturd

      Bring it on...

      This is ALL fantastic stuff.

      The more accuracy, the better.

      Physics. The FULL understanding of which is what EVERYTHING is made of...



      It's all physics really...


      Oh, and philosophy... :o)

      1. Allan George Dyer

        In the same way that...

        all [electronic] computing is toggling voltage levels. Just because you know the complete CPU instruction set, it doesn't mean you understand an XML schema or machine vision. A list of fundamental particles doesn't tell you about the elegance of the extended phenotype of a caddisfly larvae.

        Still, fantastic stuff about the bottom layer.

      2. Anonymous Coward
        Anonymous Coward

        Re: Bring it on

        "It's all physics really... Possibly..."

        Possibly not:

      3. commonsense


        It's the best guess at an explanation of the things that we observert are made of.

    3. John 62
      Big Brother


      They're going to measure how neutrinos will be affected by the moustaches being grown.

  3. NoSh*tSherlock!

    To Richard French

    Neutrinos are seriously hard to direct - from Cern they simply aimed directly at Grand Sasso through the earth - and they went through without a problem - further reading will tell you they are so good at slipping through stuff they receiver at Grand Sasso is solid lead and only records an occasional impact,

    So it is much like light going throuh space on a tiny scale - as far as a neutrino is concerned the occasional atom nucleus is so far from the next that a collision is very rare. Furthermore a neutrino does not carry any charge (AFAIK - correct me if I am wrong) so it does not easily get diverted by electrons or protons.

    If you sent it down a fibre optic it would simply go straight out at the first bend.

  4. Robert E A Harvey


    Igor! The Swit...

    Oh, you have already, already.

    1. Michael H.F. Wilkinson Silver badge

      Yeth, marther!!

  5. Unicornpiss

    @Richard French

    Not sure what you mean by a fibre optic loop. Neutrinos are not photons, and wouldn't be carried by a fibre-optic loop. They would pass through it completely, the same as they do through the entire planet. There is nothing known that can reflect them either. Using fibre optics wouldn't even work for a speed test with light, as the velocity of the photons would be changed by the fibre optic medium I believe, complicating the calculations.

  6. Richard French

    Enough already ....

    I didn't know HOW naive I was .... thanks for all the replies - I did have the whole thing A about T

    1. frank ly

      And more.....

      It's A about F, or A over T. (It's your day for corrections isn't it?)

    2. Dan 10

      @Richard French

      Think yourself lucky - I asked more or less the same thing on a previous related article, but received a single thumbs down and no explanations!

  7. Anonymous Coward

    I Say Measurement Error

    Very much like "Cold Fusion" and all the perpetual energy generators out there.

  8. Anonymous Coward
    Anonymous Coward

    What about the *other* part of Richard's question?

    Ok, so we know that neutrinos won't follow a loop, but even if they could you would have another problem. In order to get any kind of accurate measurement you would need to have a decent sized loop*. As soon as you have a decent sized loop all the other problems related to a moving** frame of reference come back into play and you would have to try to compensate for the effects around the whole loop***.

    * A small loop would have the problem of "how many times has that neutrino been around?

    ** Earth revolving and orbitting.

    *** Which unfortunately are unlikely to add up to a net zero.

  9. Long John Brass

    Igor we need more Igor's

    If CERN doesn't have an Igor on staff and a big red switch or lever I'm going to me very dissapointed.

    Lets face it, these guys are doing mad^H^H^H MAD science.

    Wild haired white-coated boffins are one thing

    But if you don't have an Igor or two, you just ain't doing it right :)

  10. Anonymous Coward
    Anonymous Coward

    This is old news

    Announced 3 days ago in many other places. El Reg is running behind. Not the first time btw.

    1. ~mico

      The delay in publication was caused by time dilation in the vicinity of superluminal neutrino beam.

    2. Heironymous Coward


      It's like they get weekend off or something... WTF??

    3. John G Imrie

      No No No

      Ell Reg is on Standard Relativistic Time, every one else reporting this is on Neutrino Time.

      That's why the clocks went back over the weekend.

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  12. Mage Silver badge

    Some pulses received

    .... . .-.. .--. -- . .. .- -- - .-. .- .--. .--. . -.. .. -. .- -. . ..- - .-. .. -. --- ..-. .- -.-. - --- .-. -.--

    A 1907 Coherer for Radio probably works better than any detector for Neutrinos

  13. Andy Farley

    Could they not...

    have different spacings between the pulses to correlate them better?

  14. Scott Broukell

    "Hello ... CERN help desk.."

    "What?, your neutrino experiment gave some strange results, ...... mmmm ....... have you tried turning it off and then on again ?

  15. Solly

    Sorry but we don't serve neutrino's in here.

    A neutrino walks in to a bar.

    1. Scott Broukell

      A neutrino goes into a pub ...........

      .... and not a single person notices it.

      Within minutes several billion, squillion other neutrinos go into the same pub.

      Once again nobody notices a thing.

      Then one neutrino lepton to the bar and did a little jig, which may or may not have caught the attention of at least one person in the bar.

      I blame it all on the amount of tau-killer slammers.

      <did i post this twice?>

    2. Scott Broukell

      A neutrino went into a bar ........

      ... and not one person noticed.

      75 trillion squillion other neutrinos went into the same bar and still nobody noticed.

      Then one neutrino lepton to the bar and did a little jig, which may or may not have been noticed by at least one or more peeps in the bar, but who can tell?

      I blame it all on those tau-quila slammers.

  16. Dan 10

    Take note...

    .. all those involved in hysteria-backed (as opposed to purely evidence-based) debates such as the dreaded global warming:


    Or maybe it's just the lack of government tax £££/$$$ etc that leave the neutrino debate to people that know what they are talking about, rather than politicians.

    1. Sorry that handle is already taken. Silver badge

      No, it's not heretical to challenge someone's findings

      But it is considered poor form if you fail to propose an alternative explanation for the evidence and simply accuse the "other side" of political bias.

  17. John Smith 19 Gold badge
    Thumb Up

    Whatever happens will be interesting.

    Either CERN learns more about the sort of subtle errors that can mess up this sort of experiment (no difference) or it learns something new about the physics.

    Good result either way.

    1. Andy Fletcher

      Or perhaps....

      ...quantum tunneling wasn't taken into account, so we just get confirmation of something we knew already (in the 1920's). If it's not a measurement error, that's where my money goes given that neutrino's travelling through the vaccuum go slower than light, but neutrinos going through rock (perhaps) go a tiny bit faster.

  18. This post has been deleted by its author

  19. Loyal Commenter Silver badge


    How can the scientists involved be certain that the neutrinos they measured were the ones sent from CERN?

    Given that huge numbers of these things come streaming through space from all directions and zip happily through the Earth all the time, could the measurement not been of neutrinos from another source, such as solar neutrinos?

    Is it a case of the neutrinos being generated at CERN being somehow focussed into a tight beam, and multiple detections being made at Gran Sasso at the same time? I find this unlikely, especially the focussing of neutrinos, which AFAIK are only susceptible to the weak nuclear force.

    Of course, I stand to be corrected...

    1. Ian Michael Gumby


      You're right.

      The Neutrinos could be from outside the chamber. But then again, they could probably discount them through statistical analysis or tracking of the path and direction.

      I think that they may have gotten it right by changing some of the parameters of the experiment.

      Personally I would love for the changes not to work and explain the neutrinos. Sorry, I'm a sci-fi geek at heart and the unanswered question makes for some good sci-fi type speculation.

    2. Anonymous Coward
      Anonymous Coward

      correctional measures applied

      the neutrinos are generated from a tight beam of 2GeV protons, whose momentum constrains the neutrino beam, the neutrinos having very little transverse velocity. Its more complicated, of course, there are intermediate pions and a magnetic funnelling, if the link below describes what is actually done. (paywalled, abstract only)

      So, the focus is achieved by tuning the protons to have just enough energy to generate the neutrinos "at rest" in the moving frame of the protons (- i.e. near "c") - this eliminates transverse velocity and therefore produces a non-diverging beam.

      Therefore there is a reasonable signal-to-noise in the detector - still only a few detections per bunch of 10^14 neutrinos, but enough for a picture to emerge. - that we can all argue about. The statistical analysis is hard, and may contain errors, hence the move to a "gapped" pulse, with a big feature in the middle, a more distinctive profile.

    3. defiler

      That seems to be the point

      By modulating the neutrinos on a distinct pattern, they should be able to show that it's the same stream. And also they'll be able to see if the modulation smears or any such. That's the way I see it anyway. Tea anyone?

  20. Clive Galway

    My guess

    Just a layman's stab, and I am not that well informed on the news item, but aren't the neutrinos meant to be passing through the centre of the earth?

    As mass warps space-time, then thinking of the rubber sheet with a ball on it analogy, aren't the neutrinos maybe taking the straight short route (following the line where the undeformed rubber sheet would be if the ball wasnt there) rather than the long bendy route down the dip in the sheet, through the ball and up the other side.

    Is there anything else that we can detect going in one side of the earth and coming out the other? If not, how can we attribute this FTL phenomenon to neutrinos? Maybe anything that has the ability to ignore matter is not following the same rules as everything else and so will appear to be travelling FTL.

    Just wild speculation from someone with no more qualifaction to be asking the question apart from hair rather like Albert Einsteins - But hey, if you have the mad scientist look about you, that qualifies you in my book ;)

  21. Neil Barnes Silver badge

    Why are they bothering doing it all again?

    Surely - cause occurring before effect - they already know the result?

  22. FredScummer
    Paris Hilton


    Reading all the responses relating to these naughty neutrinos which won't be guided by a fibre optic cable and I realise that I've obviously entered the wrong club. I didn't see a sign indicating that only Albert Einstein's could enter. Very sorry, will exit and see if I can find the room I want.

    Paris because I hope she'll be in the room I'm looking for, as I want to practice being a neutrino.

  23. JeffyPooh


    Use these neutrinos to provide short-cut-through-the-Earth communications between European, Asian and USA stock markets for real-time traders and their evil programmed trading clusters.

    We will only know that this has been done when it's too late - after some anonymous brokerage house wakes up one morning to find they've captured *all* the money in the world.

    Don't laugh - they're digging trenches across New England to save a few milliseconds...

  24. Anonymous Coward
    Anonymous Coward

    this might...

    "as far as I can tell"? - without even looking you mean.

    here's how they do it:

    A conceptual design is presented for a high-power pion production target and collection system, which is suggested to be used as source for the proposed CERN muon-neutrino factory. A relatively low-energy proton beam of 2.2 GeV which is pulsed at 50 Hz with ∼1014 ppp and 4 MW average power has been chosen as driver. The deleterious effects of the up to 1 kW/g power densities deposited in the target and its surroundings by the proton beam are a major technical challenge since it seriously limits the lifetime of all solid components. A target, which consists of a free surface mercury-jet with a high axial velocity, allows efficiently to carry the heat away from the production region without need for beam windows. The secondary pions are collected and injected into the pion decay channel by means of a magnetic horn. This horn which has to surround the Hg-jet target is known to be very radiation resistant as well as light and easy to exchange. The suggested mechanical layout and technical parameters of the target, horn and cooling system are discussed.

    So, they know when the target protons are released and that the rest of the reaction is pretty much as fast as light. Hence they can infer the time density of the neutrino pulse.

    As for the last remark, "Fire them at a different detector .. same result" - how the fuck would you know?

  25. Alex C
    Thumb Up

    What I like about this is that Cern's response was (paraphrased) "ooh - interesting. That shouldn't happen - it's probably an error somewhere, though we were pretty careful. Lets run it again in a simpler way and see if it happens again. "

    They tend not to start shouting about how they've made something travel faster than light, but can't prevent the journalists from inferring it.

  26. ChaosFreak
    Black Helicopters

    How can this be replicated?

    If I recall correctly, the hallmark of the scientific method is to verify an experiment by having an independent experimenter replicate the results using the same experimental setup.

    How is that possible with the LHC since there is only one in existence?

  27. Mountearl

    I can't believe you have all missed the obvious....

    It's because the so-called experts at CERN used a Denon AKDL-1 to connect their detector to the timing circuit. As it can transmit the whole of the internet in 8 picoseconds, running faster than light with a few megabits of data is no sweat.

  28. Paolo Marini

    light neutrinos?

    are neutrinos affected by light and if so could the detector equipment actually be taking a "snapshot" of their reflection instead of the real ones?

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