26 comments on “So, this speed of light thing

  1. My guess is neither. They’re a good team, so I’m inclined to accept that their measurements weren’t botched, but they may not have been measuring what they thought they were. The most likely reasons are:

    1) There’s some fundamental factor the experiment didn’t take into account, anything from continental drift to the phase of the moon to Giuseppe the cleaner giving the reference beam particles a quick polish before sending them on their way.

    2) They’ve discovered a new wrinkle in the way the universe works that means the neutrinos actually did get there faster than a straight-line light beam would have, but without exceeding the speed of light.

    Either way, faster than light communication would remain impossible – if the neutrino can take advantage of some wrinkle then it would have to take itself out of our reach to do so, and that would scramble any information we could modulate onto it.

    What I’d like to see is the same experiment but with two receiving stations along the beam. Hard to arrange though, neutrino detectors are tough to build.

    Disclaimer: I’m an optoelectronics physicist, not a particle physicist.

  2. I don’t know, but it is good scientific method – make all the data available and invite all and sundry to have a look at it without any need for FOI requests.

  3. This was a side-discovery of an experiment set up for something else. Something that didn’t really need such accurate clock synchronisation. So my betting is that improving the clock synchronisation between the source and destination will make the effect go away.

    Synchronising clocks is a tough challenge. You cannot just rely on light pulses because a) the speed of light can be slower in different media, such as air, and b) because you cannot get light to get there in a straight line.

    (60ns is equivalent to 17 metres at the speed of light.)

  4. Maybe it’s reflecting the well known fact that time operates at a different rate in Italy. Try queueing in a bank.
    Conducting the same experiment across the Spanish border could probably measure a tortoise exceeding light speed.

  5. Let’s hope it is the real deal.

    Never liked the idea we could not travel faster than light. Quite what the Universe would look like if this is true is another matter, but I would like to think we could travel to the next star within a single person’s life time.

  6. 1. The media, for once, are accurately reporting a potentially big story as a potentially big story. I’ll go on to explain why I think it won’t be, but they’ve got the potential magnitude about right.

    2. I would bet heavily on current physics rather than anything new. That, not least because the special principle of relativity has stood up to every single test thus far. The ‘speed limit’ emerges straight from the special principle.

    3. So what is it, if current physics (probably) still stands? What Matthew said is possible, and at the tail end this could be paradigm-shifting; but my prior distribution assigns the bulk of the probability to the dullest of the null hypotheses: systematic error of some sort or another.

    4. Notwithstanding all of this, the one thing it is not about is frames of reference, pace the idiot editors at the BBC. They promoted to ‘Editors’ Recommended’ some below-the-line nutter who thinks it is to do with whether the speed of light is different when you’re on the earth. Twit. Even the other BTL nutters have given the comment -38. Hanging’s too good for the lot of them.

    5. Science is working, folks. The CERN crowd are doing the right thing by exhibiting scepticism themselves and trying to debunk their own result.

  7. SMSF: you can travel to nearby stars within a person’s lifetime, if you mean the person doing the travelling. Heck, Alpha Centauri is only about four light-years away, so if you can sustain nice high accelerations for long enough, you can probably just about do it within the lifetime of an infant left behind on Earth.

  8. If you want a real physics explanation (including a discussion of Tachyons), try Lubos Motl’s blog, but short answer, it will be a timing error most probably. Faster than light neutrinos (which have mass) would really set the cat amongst the pidgeons of theoretical physics.

  9. Good summary, Philip. I should have mentioned in my original comment that 1) is many orders of magnitude more likely than 2).

    A timing synchronisation problem is definitely a possibility, but they’ve gone to some considerable trouble to rule it out. The way to solve it is to repeat the experiment at longer ranges. Given that they’re using satellite time, the timing error should be a weaker function of straight line distance than the effect they’re trying to measure.

  10. My guess is almost certainly that its a measurement error of some sort.

    It may not be something as obvious as forgetting to calibrate the instruments correctly but could be due to some subtle effect that was previously unknown.

    By way of example when Hertz (IIRC) analyzed light of various wavelengths, he found that most of the results implied that the light travelled at the known speed of light. The sole exception was radio waves for which he got a ridiculously low speed. It just so happened that when he generated radio waves, they bounced off the walls of the room back into his experiment screwing up his results no end.

    On a tangential note, relativity does not rule out FTL particles. It only rules them out traveling at the speed of light with a non-zero or non-infinite mass. It is possible for a particle traveling slightly lower than the speed of light to suddenly travel at a FTL speed without violating relativity (although whether it can actually happen is a different question entirely).

  11. @Philip W: you don’t even need a very high rate of acceleration; if you are going at 1g, you will reach the speed of light after just about 1 year (measured somewhere else!). So, given the necessary infinite energy resource, Alpha Centauri should be a mere five years’ travel away (assuming you are slowing down to zero at a rate of 1g the last year, in order to enjoy the views).

  12. If you accelerate at a constant 1g, relativity enables you to get to the other end of the galaxy 70,000 light years away in about 20 years.

    This is because in relativity moving clocks run slower and moving objects get shorter along the direction of motion. From the point of view of the traveller, the universe is moving at near light speed backwards past her, and therefore gets shorter. From the point of view of the universe, time on the travelling spaceship slows down.

    The Einsteinian version actually allows travel to distant places far more easily than the Newtonian version. Constant acceleration in a Newtonian universe gives distance proportional to the square of the duration, but in the Einsteinian version it is exponential. (Strictly the hyperbolic cosine function, but that’s very close to exponential for large values.)

    As you approach light speed, the universe contracts more and more until at light speed itself the length would be zero. You would arrive instantaneously. Going faster than light implies the ability to travel backwards in time – literally. Any FTL device could be used to construct a time machine. So if true, this would be a lot bigger story even than a perpetual motion machine.

    Almost certainly it’s measurement error of some sort, but it will take a few months to sort out exactly what is going on. If you suddenly notice a lot of physicists at CERN all winning the lottery week-after-week, that’ll be the time to take it seriously.

  13. In the dim and distant past everyone, including scientists, thought that the human body couldn’t cope with speeds over 30mph (or some such slow speed).

    In the more recent past, everyone, including scientists, thought that the speed of sound was a finte limit to travel at in the atmosphere.

    In the future, everyone, including scientists will know that the speed of light is just the speed of light and that objects can avoid travelling at the speed of light. How that happens we don’t know, but neither did the scientists in the 1920s with regards airplanes travelling faster than the speed of sound.

  14. As an aside, I see that one technique used to detect neutrinos relies on a nucleus changing from gallium to germanium and then back to gallium. Naturally it’s been named the Alsace-Lorraine method.

  15. SMFS @ 5:

    “I would like to think we could travel to the next star within a single person’s life time.”

    WTF ! You prejudiced against the married?

  16. Nullius in Verba:

    You’re exactly right: I’ve come back to tell y’all it ain’t happenin!

    All of “natural science” (INduction, to certainly include Physics) is a subset of the overall system of DEduction by which the mind operates. The entire INductive system is merely a recognition of the truth that, if A plus B equal C and D plus E equal B, then A plus D plus E equal C as well.

    In recognizing a dimension, “time,” we merely affirm the hard-wired structure of mind in which something we call an “effect” is (and must be) separate (and “antecedent”) to the paired entity we call “cause.” In the very same way faster-than-light-speed suggests backward movement thru time, it posits also “effects” occurring prior to their “causes”–for all practical purposes, a logical contradiction–that of “uncaused effects.” (And, if “uncaused effects” were actually a possibility, then when scientists search for the “cause” of an “effect,” why, indeed, would they confine their investigation to the temporally precedent?)

    In fact, insofar as I can see, other than shown us by what seems the universality of the cause-and-effect relationship, we have no verification of the independent existence of that we call “time.” As far as we know (or CAN know, with our limited human minds) it’s simply something we’ve “made up” and assigned to any gap perceived between “cause” and “effect.”

  17. It would be nice if they were right, because current physics is a shambles that badly needs some new facts or insights. But I’d guess that the way to bet is agin’.

  18. Matthew – “As an aside, I see that one technique used to detect neutrinos relies on a nucleus changing from gallium to germanium and then back to gallium. Naturally it’s been named the Alsace-Lorraine method.”

    I think that is likely to be the funniest ever comment on this subject.

    19 Gene Berman – “WTF ! You prejudiced against the married?”

    No, but you know married life – it may not actually be an eternity, but it sure feels like it.

  19. Alsace-Lorraine effect – brilliant.

    I wonder how big the headline will be when the team retract their finding in a few months’ time.

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