Science and Society, Technology

FTL neutrinos FTW!

* Ahem *  Well, not quite.              (Note: FTL = Faster Than Light)

The first image, taken in 2007, of a neutrino interaction. The neutrino, coming from the left of the figure following an interaction, produces several particles identified by their tracks in the detecting 'brick'. Credit: INFN (Italian National Institute of Nuclear Physics)

Not entirely, at least.

Those of you watching the science news today may have noticed an awful lot of excited wittering about results being published today which suggest the neutrinos may have broken the speed of light.

Please note the use of ‘may’ there.

First, a brief note on neutrinos themselves.  My favourites of the subatomic particles*, they are virtually massless, seldom interact with, well, anything (making them tricky as hell to detect), and on top of it all, have a pretty fascinating discovery story, at least some of which involves enormous underground pools of bleach.

They’re similar to electrons, in fact, except for the intriguing characteristic of having no electrical charge.  How’re they made?  By nuclear reactions and certain kinds radioactive decay - our sun, for example, pumps out a fairly respectable number of them, but at least some of our experiments actually involve our making them, and pointing detectors in their direction**.

Oh, and also?  Neutrino detectors are seriously, seriously beautiful and involve some wonderful chemistry/physics.  Examples include IceCUBE!, Super-K, and MINOS.

Now, on to the Science of the Day.

Nothing, at least according to one of Einstein’s equations (you know, the one beginning e=…), can travel faster than the speed of light in a vacuum (light travels slower in dense media***).  However, scientists on the Opera (Oscillation Project with Emulsion-tRacking Apparatus) experiment are announcing today, at Cern, that they appear to have results showing neutrinos doing exactly that.

And it’s got everyone extremely excited because, well, it could overturn causality - the idea that cause comes before effect.  We’re talking _time travel_ here, people.  And having to fundemtnally relook at our understanding of physics.

Amusingly, though, it does, finally, allow us the following joke (thanks @rmi!):

“We don’t allow FTL neutrinos here”, said the barman. A neutrino walks into a bar.

Over the last three years, our somewhat-bemused scientists have been watching the arrival of some 15,000 neutrinos, and noticed that they were arriving slightly faster than they should.  Apparently, some 60 billionths of a second earlier, with an error margin of plus/minus 10 billionths of a second.  This in a 730km, 2.4 millisecond (ish) trip.

At this point, I’m going to quote from the Guardian:

The measurement amounts to the neutrinos travelling faster than the speed of light by a fraction of 20 parts per million. Since the speed of light is 299,792,458 metres per second, the neutrinos were evidently travelling at 299,798,454 metres per second.

Physicists can claim a discovery if the chances of their result being a fluke of statistics are greater than five standard deviations, or less than one in a few million. The Gran Sasso team’s result is six standard deviations.

To everyone’s credit, the scientists involved are being very careful to point out that they are not, as yet, claiming to have overturned any equations whatsoever, and are asking their colleagues to help them either verify the results, or figure out what happened.  Which is pretty awesome :)

And there are a number of alternate hypotheses floating around for the result.  Perhaps they took a shortcut through some other dimensions, for example. Perhaps the ultimate speed isn’t that of light, but of neutrinos, and something’s slowing light down more than we thought.

And, in a really fun conversation thread on Facebook, Ethan Dicks said the following:

For comparison, when I was at IceCube, three sigma results were trivialized, but four sigma is where you start to think about publishing. If they want to support overturning a simple and fundamental thing like the speed of light, six sigma is not overkill.

Not having seen their evidence yet, I would initially wonder if the neutrinos didn’t take some “shortcut” during the muon-tau oscillation. After all, the important phrase is nothing can go faster than light *in its medium*. If the neutrinos are doing something unfathomably bizarre, perhaps the speed of light still holds, but we don’t understand the medium or the path the neutrinos took.

I’d bet on some flavor of “hyperspace” before I’d bet on time travel.

Ethan’s a former researcher and three-time South Pole Winter-over for the University of Wisconsin-Madison and the IceCube Collaboration. He ran AMANDA for a while, then then helped install and run IceCube for a bit, too.

And perhaps it’s nothing at all: a fluke, or some new interesting effect.

Either way, we’ll be watching closely!

The paper can be found here, and Cern’s doing a webcast, too.  I _would_ link to all the coverage out there, but there’s tonnes of it, and you have Google :)


* They’re like the ninjas of the subatomic particle world.  Very, _very_ sneaky.  Also, I get the impression, rather diffident.  And, possibly, they may help explain why our universe favours matter over antimatter (they can change ‘flavour’ from muon neutrino to electron neutrino). Thanks to Seth for alerting me to that one.

** Yes, I am paraphrasing :)

*** I’m forbearing from making any puns here about poor media reportage and shining the light of knowledge onto things



It’s worth noting that arXiv isn’t peer-reviewed, much as I absolutely love the papers posted thereon :)

Also, I’d like to know who’s driving the media frenzy on this - the scientists?  Cern?  The media itself?  Because at the moment, the news is actually ‘we have something interesting which we cannot currently explain’.  Yes, it’s _very_ interesting, but still… I’d have been far more interested to hear about this once it’s been through all the checks and balances the scientific community will go through over these results. If it turns out to be an error, I’m concerned there’ll be the inevitable chorus of ‘naughty scientists, wasting our money and time, blah blah blah’.  So yes - is this actually _responsible_ science reporting?

  • Brent

    Ethan Siegal on his Starts With a Bang blog makes the interesting point that neutrino speeds have already been measured from supernova explosions and they are consistent with the speed of light. (see

    I think it’d be cool if the absolute speed limit was a bit faster than light, but I think it more likely that a systematic error has occurred.


  • aimee whitcroft

    Awesome point :)

    The scientists were careful to say that they’d ruled out anything obvious, but yes, sadly, the most likely thing is

    It’s not systematic error OR FTL, though - there may be something else going on, too. Perhaps it’s only a short-distance effect?

    No idea, and it’s pretty unlikely that it’s FTL, but the wittering is fun. Cheers for the article, Brent :)

  • Lawrence D’Oliveiro

    Either way, whether they’re really travelling FTL or taking a shortcut through hyperspace, it’s still pretty amazing. Because maybe, just maybe, humans will be able to travel the same way someday…

    • aimee whitcroft

      Indeed :) although moving from subatomic to macro is an interesting challenge :)

  • Torbjörn Larsson, OM

    Note that they don’t explicitly give or mention the conversion between the geodesic GPS system they used and the neutrino chord beam travel distance. Curiously, the difference is 22 m for 730 km of distance, or ~ 60 ns for particles traveling near light speed; exactly the sought discrepancy.

    There are other problem, not having a replicating experiment yet the largest.

  • Grant Jacobs

    This article at ArsTechnica might interest readers here: More details on the “faster than the speed of light” neutrinos (about the possible sources of error and checking them).

  • Rich d’Rich

    I was sent this:

    which posited a statistical error.

    Torbjorn: I would assume that they’d positioned the source and detector to an appropriate level of accuracy, probably in earth centred XYZ coords. 1ns=300mm, right, and GPS post-processing gets accuracies in the 100mm range.

  • jesse jimenez

    Relativity doesn’t forbid ftl if it is already at ftl.It forbids ftl acceleration,if you have mass.

  • Falafulu Fisi

    The idea of time traveling is an absurd and nonsense idea regardless if some objects can travel faster than light or not. The idea of time traveling is a pure mathematical construct only and has no correspondence to physical reality at all. This is when physicists become substituting mathematical constructs as if it is the same thing as physical reality. Physics must be guided by objective philosophical principles rather than mathematical constructs.

    There is nothing wrong with the use of mathematics, it is the interpretation of mathematics that it is the problems. Physicists tend to interpret every solutions as somehow corresponds to some unknown physical observable. Negative mass, point particle, time travel , blah, blah, are obviously absurd ideas which should not exist in reality.

  • Falafulu Fisi
  • aimee whitcroft

    Falafulu - I’m not sure I agree. While theoretical physicists do indeed come up with some outlandish ideas/particles, a number of them have, in fact, then turned out to be true. Also, there’s still an awful lot we don’t know about our universe, so making blanket statements is potentially not going to be accurate :)

    Jesse - interesting point :)

  • jesse jimenez

    The other half of the ftl rule is;if it is ftl,it can’t carry a signal/information

  • Rich d’Rich

    You might have one of those smartphone things, Falafulu.

    It’s got a GPS in it that’s been programmed with relativity mathematics to allow for satellites flying around the earth very fast - if it wasn’t, it would send you off to the wrong place.

    And when you upgrade it, the flash memory uses quantum tunnelling to store information in memory cells.

    Mathematical physics is used in the design of stuff we use every day.

  • jesse jimenez

    there are examples of ftl-they just can’t carry a sig/info

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  • Bob Bridges

    Jesse, the reason Relativity forbids acceleration of a mass past c is that mass increases with velocity, up to a theoretical infinity at c itself. If a mass is going faster than c…what would it mean for its mass to exceed infinity?

    Or maybe I just don’t know what I’m talking about.

  • jesse jimenez

    But,does a nuetrino have measureable mass.I think it does.Too many ifs.We have to wait for confirmation.It might break half the rule,but which half?

  • aimee Whitcroft

    Current thought is that neutrinos have mass, but an astonishingly small amount of it…

  • Falafulu Fisi

    Rich said…
    You might have one of those smartphone things, Falafulu

    You’re talking to a physicist.

    Rich said…
    It’s got a GPS in it that’s been programmed with relativity mathematics to allow for satellites flying around the earth very fast – if it wasn’t, it would send you off to the wrong place.

    I already knew that. Relativity regarded space a reified object which is not. In objective philosophy, It is a relational concept only, ie, the mathematics tells us that. It is not an object or matter. It makes sense only in mathematics but it has no concrete existence in physical reality. Relativity is a correct theory (as a physical theory), however, if you hear someone talking about space-time as some sort of objects is simply misleading. Space is not reified object. It is a relational concept only, which is understandable when you look at the mathematics. It doesn’t exist as physical reality.

    I recommend you buy a series of lectures form a physicist named Dr. David Harriman, which is called “Philosophical Corruptions of Physics”, which he described of how mathematics takes over physics, and concepts that are only makes sense in the formulas, physicists just take them blindly and interpret as somehow they correspond to some unknown physical observables or physical realities to be discovered at some stage in the future when technology catches up. Mathematical representation is not the same as physical reality.

  • aimee whitcroft

    I’m a wee bit confused. If space-time isn’t a physical reality, what on earth are we interacting with?

  • jesse jimenez

    Is it true that space is traveling ftl at edge of universe&relativity does not forbid space ftl,and galaxies r riding on the space.Space is going ftl¬ the galaxies-they’re just riding on it.

  • Bob Bridges

    Aimee, by \reïfied object\ I take Falafulu to mean that while matter and energy are measurable objects, space and time are, in a manner of speaking, the LACK of objects, or the place (and time) where both occur. I don’t know enough to say it’s true, but it makes sense to me.

  • Falafulu Fisi

    What does space-time curvature mean? Is time dimension curved on its own? If so, then how does measuring time-lapsed of a physical event be described as curve? Can a 2 nano-sec, 2 micro-sec or 2 milli-sec be something that can be described as curve? Also, Is space dimension curved on its own? How about the combination of the 2 , ie, space-time curvature? What is being curved? What about space with no material or substance ? When is only defined when real objects exists, then space concept can be applied to the relation of object A relative to object B. Without the existence or presence of real objects, then space dimension is meaningless, because it is not an irreducible primary. It is a secondary. Real objects must exist first & foremost as physical reality (irreducible primary) before space as an abstraction concept can then sprung up as a result to describe their relations (secondary).

    Curvature as an abstract concept can only be made sense when it is applied to real objects. Space-time is not real object (or anything substance) of some kind on its own. It makes sense when one looks at the mathematics, however, this doesn’t make sense to go further than just that to deduce, imply or conclude that the mathematical description of space-time curvature is an object. For doing so, is going against or outside the objective philosophical definition of existence.

    Interpretations of Physics must go hand in hand with philosophy or otherwise, it wandered into the domain on non-causal (non-existence) speculation which is exactly what faith/religious believers do. We can’t deny existence by simply making exceptions (according to some mathematical physics solutions’ in some theories) or otherwise, we have to regard everything around us as just a big illusion, nothing is real (exists).

  • Falafulu Fisi

    What is nothing?