Victor Stenger on speedy neutrinos: did we cause God?

Over at Puffho, Victor Stenger ponders the evidence for faster-than-light neutrinos in a nice piece called “No cause to dispute Einstein.”  Many of us know Victor as an eloquent atheist/physicist, but he also informs us us that he worked for thirty years on neutrinos. Clearly, he’s eminently qualified to pronounce on the CERN experiments suggesting that those particles can move faster than light.

Stenger makes two points.  First, like many physicists he’s wary of the results, mainly because they’re contradicted by earlier data on supernovas:

However, a big fly in the ointment is the supernova in the Large Magellanic Cloud, which sits just outside our galaxy 168,000 light-years from Earth. It was first seen by the naked eye on February 24, 1987. Three hours before the visible light reached Earth, a handful of neutrinos were detected in three independent underground detectors. If the CERN result is correct, they should have arrived in 1982. So, if I were a wagering man, I would bet the effect will go away because of some systematic error no one has yet been able to think of.

However, if particles can move faster than light, then there’s an astounding conclusion: effects can precede causes.

. . . superluminal [faster-than-light] motion in no way contradicts Einstein’s theory of special relativity published in 1905. Einstein’s equations fully allow for particles to travel faster than light — provided they never travel slower. Physicists have speculated about such objects for years. They are called tachyons. Many searches have been conducted, with no significant signals until now.

Einstein showed that it was impossible to accelerate a particle moving less than the speed of light (in a vacuum) to the speed of light or higher. Similarly, a tachyon cannot be decelerated to or below the speed of light. Only massless particles, such as photons, travel at exactly the speed of light.

However, there is a problem with tachyons. They imply that cause and effect are interchangeable. Consider the famous duel between Aaron Burr and Alexander Hamilton on July 11, 1804. An observer moving by at less than the speed of light with respect to the participants would have seen the bullet from Burr’s gun enter Hamilton’s lower abdomen. However, another observer moving faster than light would have seen the bullet emerge from Hamilton’s abdomen and enter Burr’s gun. Did Burr kill Hamilton or did Hamilton kill Burr? [jac note: I don’t understand the last sentence since in no frame of reference did Burr die. But the point is clear.]

Stenger says—and I did not know this—that the principle that causes must precede effects was an add-on that Einstein made to his theory of special relativity; it was not a consequence of his theory itself.  And if particles can move faster than light, then our whole notion of cause and effect is inverted.  This complete reversibility of time, and hence of cause and effect, is inherent in the Feynman diagrams of particle-particle interactions.

As a card-carrying New Atheist, and author of several good books on atheism, Stenger can’t resist using this possibility to get a little dig in at the faithful:

So, if confirmed, the reported result from CERN or any future observation of superluminal motion will not lead to the overthrow of Einstein’s theory of relativity. Its significance will be to overthrow the distinction between cause and effect. At the worst, Einstein might be faulted for taking causality a little too seriously.

Finally, you might want to ponder what effect the demise of causality would have on the notion of God as the ultimate cause of all there is.

___________

Over at the Guardian’s science section, Alom Shaha points out why the “Faster than light story highlights the difference between science and religion.” It’s all about doubt, replication, and hesitancy, of course:

 But the recent fuss over the possible existence of faster-than-light neutrinos illustrates precisely how different science and religion are when it comes to questions of “belief” or “knowledge”. . .

One of the things that appeals to me about science is that, unlike religion, science is not dogmatic. It does not say: “This is the way things are, and it can be no other way.” Instead it says something like: “Based on the evidence we have so far, this is how things probably are; if clear and solid evidence is discovered that shows this is not how things are, then we will need to change our minds.”

Science can seem rather weak in comparison to the certainties religion offers. But it is this very “weakness”, this refusal to issue absolute statements of truth, that allows science to progress, and to come up with increasingly better ways of explaining the world.

It’s the usual stuff, but the public can’t hear this too often.  Religion not only offers no certainties, but offers no knowledge, either.

h/t:  Luke

80 Comments

  1. Posted September 28, 2011 at 10:42 am | Permalink

    Well, to be fair…religion offers a great deal of certainty — absolute certainty in many instances. “I know that my redeemer liveth,” as Handel put it so beautifully.

    It’s just that it’s a completely unjustified certainty, is all. Especially considering how many of the “facts” about which the religious are absolutely certain aren’t merely worng, but batshit fucking insane.

    Cheers,

    b&

  2. Kevin
    Posted September 28, 2011 at 10:43 am | Permalink

    Oh, but religion doesn’t claim to offer knowledge. Only a different way of knowing.

    Get it? Different. One means stuff you can understand. The other means — well, nothing at all.

    Checkmate!

    • betelg
      Posted September 28, 2011 at 2:16 pm | Permalink

      LOL!

  3. Gregory Kusnick
    Posted September 28, 2011 at 10:55 am | Permalink

    “If the CERN result is correct, they should have arrived in 1982.”

    Seems to me Stenger is making an unwarranted assumption here that all superluminal neutrinos must travel at the same speed. If he wants to argue that the limiting speed for neutrinos is 1.000025c, then that might make sense. But he doesn’t; he argues instead that neutrinos are tachyons, constrained to travel faster than light, which means their superluminal speed will be energy-dependent, just as it is for subluminal particles. In that case there’s no reason to suppose the neutrino speed measured at CERN has any direct relation to the speed of supernova neutrinos. Stenger of all people should know this.

    • newenglandbob
      Posted September 28, 2011 at 11:52 am | Permalink

      …their superluminal speed will be energy-dependent…

      Energy dependent which way? The closer to the speed of light, the more energy required? Or the further from the speed of light (even faster) the more energy required?

    • Posted September 28, 2011 at 10:41 pm | Permalink

      Should “c” actually be glossed as “the speed of light”? Isn’t it really “the constant of relativity” or “the constant of mass/energy”, defining the relationship between energy E and mass m, having units of distance/time (squared), and setting a limiting velocity that only light in a vacuum, being massless, can reach?

      Calling it “the speed of light” suggests that light has some privileged relationship to energy and matter, when in fact the connection is pure happenstance.

      • Gregory Kusnick
        Posted September 29, 2011 at 12:29 am | Permalink

        Not sure what you mean by “pure happenstance”. It’s not a coincidence that the c in E=mc^2 is the speed of light; Einstein got there by reasoning from Maxwell’s equations, which are explicitly about the propagation of light in a vacuum.

    • Diane G.
      Posted September 28, 2011 at 10:47 pm | Permalink

      Undoubtably a painfully stupid question, but…how do we know (some) neutrinos didn’t arrive here in 1982?

    • Torbjorn Larsson, OM
      Posted September 29, 2011 at 5:20 am | Permalink

      First off, it isn’t “the CERN results” but results with CERN (by the OPERA team). CERN provides the neutrons, OPERA measures them elsewhere.

      Second, it is OPERA’s own results that the discrepancy is energy independent!

      [However, there are always loopholes. Here the neutrinos are different kinds, for example.]

  4. Josh
    Posted September 28, 2011 at 11:13 am | Permalink

    As Sean Carroll pointed out at Cosmic Variance, there is really no need to throw out causality if the neutrino results hold up. Physics could be perfectly fine without Lorentz invariance, but without causality what would physics even look like? There would be no initial value formulations, and we’d have no meaningful notion of predictability.

    • neil
      Posted September 28, 2011 at 12:33 pm | Permalink

      Carroll also points out that the SN87A observations do not necessarily contradict those of OPERA. The SN87A neutrinos were lower energy electron neutrinos whereas the OPERA are higher energy muon neutrinos. Neutrinos do occillate between the forms and I do not know how that relates to the findings, but my blog reading suggests that most physicists do not think SN87A or an implied violation of causality necessarily rules out a superluminal finding.

      That said, most say that they expect the observations will prove to have some prosaic explanation.

    • Posted September 28, 2011 at 1:02 pm | Permalink

      I’m not seeing how a particle’s (alleged) capability to travel FTL affects causality at all.

      I’m no physicist, so if anybody cares to, please correct me.  Here’s what I’m thinking:

      Chains of events (i. e., things happening) don’t necessarily depend on a human sense organ to come along and perceive them in order for them to have happened.  Light sends information to our retinas at 300,000 kps.  Sound travels to our ears at .33 kps.  I don’t think anyone claims that discrepancy as a problem for causality.  We just have to understand that even though we see an event before we hear it, the event did happen at a certain, discrete moment.

      How would information from an event reach us before the event happened?  So what if the information is traveling at 400,000 kps?

      Ok.  What am I missing?  Ready, go!

      • Gregory Kusnick
        Posted September 28, 2011 at 1:15 pm | Permalink

        What you’re missing is special relativity, which says that events separated by a spacelike interval (i.e. not bounded by light cones) have no well-defined order. Different observers see them happening in different order, depending on their relative speed. So you can’t definitively say that A caused B if the alleged causal link is superluminal. To some observers, it will look like B came first.

        • Posted September 28, 2011 at 1:36 pm | Permalink

          Ok. And because observers may detect an event (either with their biological sense organs or with a technological, prosthetic sense organ) at different times, we can’t say the event in fact happened at one, objective moment?

          This still sounds to me like the act of observing has some crucial role to play in whether anything happens or not.

          But I’m confident I just don’t know enough physics. I’ll stop stinking up the thread with my amateurism now. 🙂

          • Marella
            Posted September 28, 2011 at 4:01 pm | Permalink

            I’m no expert either but one of the weird things about physics is that the act of observing does have measurable effects, such as the fact that one electron can go through two slits if not observed but only one at a time if it is observed.

            • Gregory Kusnick
              Posted September 28, 2011 at 6:49 pm | Permalink

              “Observer” in relativity theory means simply an inertial frame of reference in which measurements can be made. It does not imply a conscious mind taking notice of anything.

              With regard to the two-slit experiment, the photon always goes through both slits. However it can interfere with itself on the other side only if both paths are undisturbed. If you disturb one path by measuring the photon as it goes by, then you “decohere” the quantum state and prevent the interference. But again it has nothing to do with conscious observers; it just has to do with the photon interacting with atoms in the measuring device on one path but not the other. Not nearly as mysterious as people tend to think.

              • SLC
                Posted September 29, 2011 at 5:20 am | Permalink

                This is somewhat of a hand waving explanation which many physicists have found unsatisfying. This unsatisfaction has led to the parallel universe proposal (not to be confused with the multiple universe hypothesis; the two are not the same although the former may be a subset of the latter) in which the same experiment is being performed at the same time in a parallel universe and the photon goes through the other slit in that experiment.

            • Posted September 28, 2011 at 8:36 pm | Permalink

              I’m aware that taking measurements during an experiment can affect what happens during the experiment, as Gregory explains. That’s not what I mean.

              My question is: What does the speed of particles have to do with the notion of causality? Why is causality upended if we can detect particles that have travelled to us a little faster than 300,000 kps?

              All of the weirdness, it seems to me, has to do with how we detect or perceive events to be happening – not that information from an event could somehow arrive somewhere before the event occurs.

              OK. Now I’m done.

              • Andrew G.
                Posted September 29, 2011 at 1:19 am | Permalink

                One of the standard examples is the tachyon duel.

                Alice and Bob fight a duel in the following manner: they start back to back, walk away from each other at a large fraction of the speed of light for 8 seconds (as measured by their own previously synchronized clocks), at which point they fire their tachyon pistols at each other. Alice is a better shot than Bob.

                What happens from Alice’s point of view is this: she gets winged by Bob’s poorly-aimed shot when her clock reads, say, 4 seconds, before she would otherwise have fired. Annoyed by this breach of the rules, she immediately shoots Bob dead – but this shot arrives at Bob when his clock reads 2 seconds, long before he fired any shot at all. Oops.

                The actual timings depend on the speeds of the duellists and the tachyons, but the presence of any faster-than-light signal allows you to set up a similar paradox where a cause produces an effect which in turn produces a second effect which is in the causal past of the original cause (and could therefore prevent it from ever happening, producing a paradox).

              • Torbjorn Larsson, OM
                Posted September 29, 2011 at 5:24 am | Permalink

                The idea, that Stenger and Kusnick remarks on, is that your version of causality was replaced by the physically realizable version of relativity. (Since relativity by its nature shows that the order of events will have to lock different for different observers, if their laws of physics should remain the same.)

                If that goes, there is no useful version of causality left.

      • neil
        Posted September 28, 2011 at 1:20 pm | Permalink

        Information arriving before it is sent alters the set of prior information, upsetting causality. It is a form of the grandfather paradox.

        • Chris V.
          Posted September 28, 2011 at 9:41 pm | Permalink

          Also not up on the physics, and so rather confused by this. It seems to me that this does not upset causality, but messes with our ability to determine causality, at least until all information is available. Irrespective of one’s ability to see which came first, something did, in fact, come first. Neil says that information arriving before it is sent creates a paradox. Totally granted. But the information does not arrive before it is sent. It arrives faster than the image of the person sending it, but does not exist before it is sent.
          Assume you had a large enough telescope to resolve a person on a planet orbiting a star press a button, but received the information from that button-press (maybe containing information on how to build such a telescope). I don’t see the paradox here. The message arriving at faster than C simply let you know that an event occurred in the past which, if you follow the instructions, you will be able to witness. Everything we witness at astronomical distances happened in the past. How is this different from seeing a bullet it the wall, then hearing the shot you now expect? We don’t mix up causality there, so why should we here?
          I’m sure it’s just my own lack of understanding.

          • Posted September 28, 2011 at 9:52 pm | Permalink

            Precisely what I’m saying.

          • Gregory Kusnick
            Posted September 29, 2011 at 12:22 am | Permalink

            “Irrespective of one’s ability to see which came first, something did, in fact, come first.”

            You might think so, but you’d be wrong. Special relativity says that for events with spacelike separation, there is no objective fact of the matter as to which happens first, since that would require a privileged global frame of reference against which everyone measures time. Einstein showed that there is no such master clock; each inertial frame has its own local clock, and those clocks don’t agree on the order of spacelike event pairs.

            The way this leads to paradoxes is as follows. Say we have event A1 happening on Earth, followed by event A2 a short time later. Meanwhile (at spacelike separation) we have event B happening near Alpha Centauri. There will be some frames in which B appears to happen before A1, and other frames in which B appears to happen after A2. So if superluminal communication were possible, we could use it to send a signal back in time from A2 to A1 by using B as a relay (A2 -> B in one frame, B -> A1 in another).

            • Chris V.
              Posted September 29, 2011 at 7:43 am | Permalink

              Sorry, I must just be dense.
              I still don’t see how this is a paradox. It looks more like a misperception of causality rather than communicating back through time. Even though we’re looking at space-like distances, causality is confined within the system of the actors, A1, A2, and B. While an observer at C may see B occur before A1 and another at D see the B occur before B, within the system of A1, B, A2, there is still a relative order for the events, no? A signal from A2 would still have to travel from Earth to Alpha Centauri and back again, even superluminally. Since A1 already happened on earth, I fail to see how, locally, that signal would be travelling back in time. I can see that distant observers could mistake the order of events, but that would not include any of the actors.

              • Posted September 29, 2011 at 8:27 am | Permalink

                Again, this is precisely what I’m thinking.

                Why should a superluminal speed = traveling into the past? Even at 400,000 kps, it will take a particle 2 seconds, that is, time, to travel 800,000 kilometers.

              • Gregory Kusnick
                Posted September 29, 2011 at 10:36 am | Permalink

                “within the system of A1, B, A2, there is still a relative order for the events, no?”

                No. B’s notion of the order of events depends on his motion relative to A. He can choose a frame in which A2 is in his past, and receive a superluminal message from A2. He can then accelerate into a frame in which A1 is in his future, and send a superluminal reply to A1. So A1 gets the reply before the original message was sent at A2. There is no global time axis against which the “real” order of events can be measured, and therefore no objective fact of the matter as to whether A1 has already happened on Earth at the time B receives the message from A2. B will always see A1 happening before A2, but is free to shift them around at whim relative to his own “now”.

              • Chris V.
                Posted September 29, 2011 at 11:29 am | Permalink

                I guess I just can’t wrap my head around this.
                Alpha Centauri is about 4.24 light-years from Earth. Whatever we observe from that system today occurred about 4.24 years ago. Are you saying that we can change that by changing frames somehow? If a FTL message came from there at 2c, it would arrive in 2.12 years, and give us information about an event which cannot be directly observed for another 2.12 years. The event still would already have happened.
                I don’t understand about changing frames. You seem to be saying that an observer at B can accelerate into a different frame, but I don’t see how that fits. We’re talking moving faster than light, not back in time. B cannot receive a signal before it is sent, no matter the speed at which it is sent. If the signal is sent at a speed which allowed it to travel from Earth to A. Centauri in a day, and back in another day, it still arrives back on earth after it left, not before.

              • Gregory Kusnick
                Posted September 29, 2011 at 12:47 pm | Permalink

                I think your problem is that you’re still trying to visualize all this as happening on a big sheet of graph paper with a space axis and a time axis, and everything is measured against those fixed axes.

                That’s not the way it works. Since everyone has their own reference frame, you need two sheets of graph paper, one for A and one for B. If A and B are motionless with respect to each other, the two sheets are parallel and the time axes line up. But if B is moving with respect to A, then the sheets are not parallel and the time axes do not line up. B’s sheet has rotated and his time axis is now tilted relative to A’s. It’s now possible for A to send a superluminal signal to B that moves forward on A’s time axis but backward on B’s time axis, and vice versa.

                I’m oversimplifying somewhat, but that’s the gist of it. In special relativity, superluminal signalling is equivalent to time travel because you can always find a frame whose time axis is tilted such that the superluminal signal moves backward along it.

              • Posted September 29, 2011 at 1:14 pm | Permalink

                I think it’d also help to imagine a simpler universe with nice, round numbers for the speed of light. And imagine the distant observer being close enough to, say, observe the as-fast-as-light message in transit before it reaches its destination.

                One of the implications of FTL communication is that all sorts of hard-to-compute problems become easy to compute simply by sending the results back to the calculating device before they’ve been calculated. But we observe a universe in which things are hard to compute, not easy, which is empirical evidence that strongly argues against FTL communication.

                It’s kinda like P =? NP. If P != NP, one would expect it to be damned hard, if not impossible, to prove the fact. If P = NP, one would expect it to be relatively straightforward, even if it’s a bit mind-bendin to the uninitiated. That nobody’s yet figured out which is the case is a very strong indicator that P != NP, even though we’ll probably never be able to prove it for a fact.

                Cheers,

                b&

              • Chris V.
                Posted September 29, 2011 at 2:42 pm | Permalink

                Thanks for the explanations. I think I can see (sort of) how the 2 locations can be at angles to each other such that the forward flow of time for one is reversed for the other. Wouldn’t we see evidence of this in the form of observed phenomena happening in reverse?
                Also, inasmuch as a calculating machine could be fed its own results through use of these 2 frames, of what benefit would it be to the 2nd frame? The amazing results would only help those locally in frame 1 (ie frame 2’s past). Unless you mean that the existence of the ability to send messages faster than light means that you can change at will what frame you are in.
                Couldn’t this happen with STL information as well, if the cause and effect were separated by enough time?

    • Posted September 28, 2011 at 2:01 pm | Permalink

      Right. If causality goes to the wall, what’s left to hold things together except God’s Will??

    • sasqwatch
      Posted September 28, 2011 at 10:51 pm | Permalink

      I am also no physicist, though I play one on TV…

      but if I understand Vic Stenger correctly, it’s quite possible that “cause and effect” could be an emergent property of macroscopic hunks of space-time. That is, time-reversibility inherent in the standard model could be just the way it is, on the level of the subatomic, and time’s arrow itself only makes sense when applied to larger collections of stuff (that is, it is a consequence of statistical entropy).

      If that’s true, “cause and effect” on the subatomic / quantum level would be nonsensical. Would explain a lot. (see Timeless Reality – the book was a great read)

      • Torbjorn Larsson, OM
        Posted September 29, 2011 at 6:27 am | Permalink

        Ah thanks, I wondered what Stenger was on about! If he takes the opportunity to push a pet theory, that at least makes sense.

        I don’t think the physics does however. The different versions of causality and time arrows are necessary for physics as we know it today. So I doubt quantum mechanics would survive untouched by such an idea.

        And that, I think, is a no go, since of all theories QM is even worse to replace than relativity. (Is unique, since it is known to minimize both number of variables and parameters AFAIK.)

  5. Insightful Ape
    Posted September 28, 2011 at 11:47 am | Permalink

    Stenger’s argument I very interesting. The kalaam(kalam) “proof” for god, originally invented by Muslims but also favored by apologists like William Lane Craig, depends heavily on the notion of causality.
    The future will be exciting.

    • newenglandbob
      Posted September 28, 2011 at 11:59 am | Permalink

      The future will be exciting.

      Or maybe the past will be.

      • Posted September 28, 2011 at 12:25 pm | Permalink

        Oh, no, the future was exciting, but I suspect the past will be quite dull…

        /@

      • Alex, Tyrant of Skep
        Posted September 28, 2011 at 3:51 pm | Permalink

        No, the past will have been going to have been exciting. Sheesh, at least get your tenses right 😉

        • Torbjorn Larsson, OM
          Posted September 29, 2011 at 6:13 am | Permalink

          I was glad I unread that, before I was going to be confused!

    • Tulse
      Posted September 28, 2011 at 1:52 pm | Permalink

      The notion that these results could undermine the First Cause arguments for god seems like a category error to me. One can’t explain why the physics of the universe requires no cause by invoking that physics.

  6. Aelfric
    Posted September 28, 2011 at 11:47 am | Permalink

    I am about as far from a physicist as you can get, but doesn’t the fact that the neutrinos from the 1987 supernova arrived before the visible light imply that they were, in fact, traveling faster than the speed of light, if only infinitesimally so? I realize probably not, but any simple and brief explanation would be appreciated! Thank you.

    • Posted September 28, 2011 at 11:59 am | Permalink

      No, the difference in arrival times matches closely with classical modeling.

      In short, when the core collapses, a burst of energy is released. The neutrinos, not hindered by the remaining shell of the star, start their journey immediately. The photons, on the other hand, are still trapped in the middle of a very dense, dark mass, and it takes a few hours for the shockwave to propagate through the remains of the star so the visible energy can be released.

      b&

      • Llwddythlw
        Posted September 28, 2011 at 12:14 pm | Permalink

        In fact, a similar effect occurs in our own sun. A fairly simple calculation shows that a photon originating at the centre of our own sun takes roughly 4,000 years of banging into solar material (being absorbed and re-emitted) to reach the surface.

        • Posted September 28, 2011 at 12:29 pm | Permalink

          Even outside stellar interiors light can travel slower than c, the speed of light in vacuo, otherwise, for example, lenses wouldn’t work!

          /@

        • Gregory Kusnick
          Posted September 28, 2011 at 1:10 pm | Permalink

          Right, but the first photons we see from a supernova would not be the ones banging around in the interior. The first photons we see would be the ones created at the surface when the shockwave impacts the photosphere. So it’s the acoustic speed of the shockwave that accounts for the delay, not the tortuous path of the interior photons, which account for the light curve in the days and weeks following the implosion.

          (Disclaimer: I’m not a physicist either, astro- or otherwise, but that’s my amateur understanding of it.)

          • Aelfric
            Posted September 28, 2011 at 1:31 pm | Permalink

            Thanks all for showing me the light (pun intended).

          • Llwddythlw
            Posted September 28, 2011 at 2:02 pm | Permalink

            Yes, now that I think about it, the solar example is somewhat different as it’s a pure random walk problem inside the solar plasma.

            • Torbjorn Larsson, OM
              Posted September 29, 2011 at 6:09 am | Permalink

              It’s fun though. Think of the headache of those photons being knocked about!*

              When photons scream in space, can anyone hear them?
              ———-
              Actually mostly absorbed and re-emitted, if I remember correctly. Random walk with delays.

  7. Llwddythlw
    Posted September 28, 2011 at 11:59 am | Permalink

    At some point in the supernova collapse, the material isn’t perfectly transparent to photons, and it takes them a while to get out.

    • Llwddythlw
      Posted September 28, 2011 at 12:07 pm | Permalink

      To be more precise, photons have a larger interaction cross section in a dense stellar plasma than neutrinos.

      • MadScientist
        Posted September 28, 2011 at 3:09 pm | Permalink

        Just like the photons in our own sun which is far from the conditions of a nova.

        • Llwddythlw
          Posted September 28, 2011 at 4:49 pm | Permalink

          And even further from a supernova. The process of photon diffusion would also occur in stars that are much more massive than our sun, for example a red giant before it goes supernova.

  8. Kevin
    Posted September 28, 2011 at 1:10 pm | Permalink

    While I do believe that the final disposition of this finding will probably be mundane, I do have a question that perhaps one of the physicists might be able to address.

    Would faster-than-light speed by neutrinos be evidence of their ability to travel through extra-dimensional space more readily than other particles? In other words, if there are 11 dimensions (or whatever the current number is) that light must travel through, wouldn’t that provide sort of a natural speed limit? And wouldn’t faster-than-light travel by neutrinos then provide some evidence of ways to test string or superstring hypotheses?

    Forgive me if that’s hopelessly muddled … but that’s what came to mind when I heard the news.

  9. eric
    Posted September 28, 2011 at 1:11 pm | Permalink

    [Stenger]: Einstein’s equations fully allow for particles to travel faster than light — provided they never travel slower.

    But AIUI, they did travel slower. Specifically, when they interacted with the detector, they slowed down.

    I think this particular detector looks at Cherenkov radiation. Cherenkov radiation is produced when a particle traveling faster than [light in that medium] slows down to the speed of [light in that medium]. So when a particle stops emitting, it is obviously traveling slower than [light in a vacuum] since at that point it is only traveling a the speed of [light in the detector medium]

    Shorter version: I think (but am not 100% sure) that no STL detector should be able to detect a FTL particle, since “detection” implies slowing down to sub-light speeds.

    • Gregory Kusnick
      Posted September 28, 2011 at 1:17 pm | Permalink

      I don’t think they’re detecting the neutrinos directly. Rather, they’re detecting the decay of (subluminal) muons created when neutrinos bang into something.

      • eric
        Posted September 28, 2011 at 1:20 pm | Permalink

        Sure. But what happens when it bangs into a muon? It slows down, right? We know E(initial) because we produced the damn things. We think we know v(initial); this is the measured time until impact. We know E(final) based on muon mass and energy. Calculate v(final). If it’s less than c, no FTL.

        • eric
          Posted September 28, 2011 at 1:20 pm | Permalink

          Err…bangs into something to create a muon. Ignore my sloppiness, I think you get the gist…

          • Gregory Kusnick
            Posted September 28, 2011 at 1:27 pm | Permalink

            Sorry, I’m still not following. When a neutrino bangs into something to create a muon, it disappears. All the energy goes into the muon (and possibly other reaction products). The neutrino doesn’t “slow down”; it’s just gone.

      • neil
        Posted September 28, 2011 at 1:23 pm | Permalink

        Also, they cannot “follow” any particular neutrino. They match up distributions sent with distributions detected. Apparently, that is problematic for the conclusion of superluminal neutrinos as well.

        • Torbjorn Larsson, OM
          Posted September 29, 2011 at 6:06 am | Permalink

          Yes, it is – the SN 1987A neutrinos were a “harder” result since they were individual neutrinos. Incidentally you can make light seem to go faster (than in vacuum) in materials too, by changing the waveform.

          There are all sorts of these problems with the OPERA results. If they found a discrepancy, why wasn’t it energy dependent? Screams simple (or not so simple) systematic error in time or length measurements.

    • eric
      Posted September 28, 2011 at 1:17 pm | Permalink

      Oops, just a short continuation, but if we did detect a FTL particle with a STL detector, AIUI it would not look like it was going FTL at all. It would instead look like it was a STL particle going backwards. A cloud chamber curved trace would spiral out instead of in, a straight trace would move towards the origin, etc. Just as in the Hamilton/Burr example: to the FTL particle, STL things seem to happen in reverse; to the STL particle (i.e., us), the FTL things seem to travel in reverse.

    • Torbjorn Larsson, OM
      Posted September 29, 2011 at 6:00 am | Permalink

      Good point!

  10. BilBy
    Posted September 28, 2011 at 1:25 pm | Permalink

    Gosh. *blink in astonishment* I’m just a zoologist. I spent the day chasing some lizards in the field. I have always been proud and happy to be a zoologist. Having read all this though, I think that, for the first time, I actually feel a little…well…physics envy

    • Marella
      Posted September 28, 2011 at 4:07 pm | Permalink

      I spent the day chasing some lizards in the field.

      Sounds good to me, I hope it was nice weather. 🙂

  11. MadScientist
    Posted September 28, 2011 at 3:04 pm | Permalink

    The question of ‘superluminal speed’ comes about by an analysis of Einstein’s equations. Einstein was simply putting bounds to complete his model when he added that cause must precede effect. It is difficult to imagine how anything can be superluminal – it either has no mass and is faster than light or it has mass, is faster than light, and was never slower than light. Now even if we were to assume that some class of particles exist that travel faster than light (something never observed to date), even that would not affect our notion of cause and effect because the dominant particles in our universe cannot be superluminal.

    The folks at FermiLab are gearing up to do a neutrino speed experiment; I’m expecting the results to be “nothing to see here”. I also wonder how much energy goes into the reactions – is it sufficient to create particles with mass traveling faster than light? If not, then the laws of conservation are in doubt. I’m still betting against ‘faster than light* neutrinos’

    * light in vacuum that is – neutrinos and other high energy particles habitually travel much faster than light as they travel through matter.

    • Posted September 28, 2011 at 3:14 pm | Permalink

      I also wonder how much energy goes into the reactions – is it sufficient to create particles with mass traveling faster than light?

      Not if Einstein was right.

      Once you get to relativistic speeds, accelerating something mostly adds to its mass, as the speed of light is an asymptote. Actually accelerating something to the speed of light would require an infinite amount of energy.

      The reason that photons travel at the speed of light is that they don’t have any mass at all.

      Neutrinos are understood to have mass because they have been observed transmuting into different particles, which is something that’s only possible for particles with mass.

      Of course, if Einstein was worng, all bets are off….

      Cheers,

      b&

      • yesmyliege
        Posted September 28, 2011 at 6:12 pm | Permalink

        Perhaps the FTL neutrinos have, or sometimes have, negative mass?

        • Torbjorn Larsson, OM
          Posted September 29, 2011 at 5:59 am | Permalink

          But general relativity predicts that you don’t have mass dipoles, as you would have if you have both polarities. Conversely, its low energy quantization gives a positive “charge” graviton.

          Think of it this way, the “field” is actually spacetime curvature, so mass have to be one kind.

          Obviously I am relaying more on inertial mass than, say other particle masses from Higgs fields in the standard model of particles, but the last mechanism should go through there too.

  12. Brian P. Rabbit
    Posted September 28, 2011 at 7:53 pm | Permalink

    Perhaps I missed something but what does the neutrino results have to do with religion? The ‘dig’ seems completely unwarranted and unhelpful, especially in light of the fact the results have yet to be reproduced and/or verified.

    Additionally, the obvious mocking of religion in some of these comments comes across as arrogant and belittling as when I hear claims “evolution is just a theory”, “global warming is a hoax”, or “of course 9/11 was an inside job; since when does steel melt as such low temperatures?” Perhaps I have completely missed the point but I would hope Commentators on science topics would leave philosophy (which encompasses religion) to the Philosophers, just like Scientists often choose to do.

    Science should and does focus on the exploration of the world from an objective perspective while drawing no philosophical conclusions; meanwhile philosophy is the study of general and fundamental problems, such as those connected with existence, knowledge, values, reason, Mind, and language while drawing no scientific conclusions. Let Us leave them both that way; shall We?

    • Nicolae C.
      Posted September 29, 2011 at 10:42 am | Permalink

      Oh, wow, it’s like an even dumber version of non-overlapping magisteria.

      “the obvious mocking of religion in some of these comments comes across as arrogant and belittling as when I hear claims ‘evolution is just a theory’, ‘global warming is a hoax’, or ‘of course 9/11 was an inside job; since when does steel melt as such low temperatures?'”

      Really? Are you suggesting that the claims of religion about the way the real world works are as well-supported as evolution, anthropogenic global warming, or the 9/11 tower collapse? I just… holy crap, please, share this information with us poor dumb unenlightened masses. PAY ATTENTION LADIES AND GENTLEMEN Brian P. Rabbit is about to do what no clergy, no theologian, no philosopher has ever done, which is demonstrate that religion isn’t dumb bullshit for children and morons.

      Either that or he’s just another godhaver sitting around and getting wienery about semantics and epistemology so as not have to deal with Thoughts.

    • Darth Dog
      Posted September 29, 2011 at 2:43 pm | Permalink

      @Brian “what does the neutrino results (sic) have to do with religion?”

      If the neutrino result destroys the idea of causality, that effectively destroys any attempt to use the cosmological argument to prove the existence of God. No causation, no need for a First Cause.

      If you read this blog regularly, you’ll see that there has been a lot of discussion about believers invoking God because they need a cause for something, from events in their personal life to the existence of the universe.

  13. Posted September 28, 2011 at 10:55 pm | Permalink

    Is it conceivable that something travelling near the speed of light (or “the limiting velocity” as above) could gain a quantum of additional velocity (I’m using the word strictly, not as woo) and then be going faster than c without having been in that tricky “infinite-energy” stage? I’m thinking of the way an electon can “tunnel” from A to C without appearing at B. Can there be tunneling through speed as there is through space? (I get very confused about just what gets reversed on the other side, so this idea could be quite silly.)

    • Chris V.
      Posted September 28, 2011 at 11:18 pm | Permalink

      My understanding is that the answer is no. Unless you’re talking about wormholes. What the extra quantum of energy does is add a 9 (or less) to the 99.9999…% of C, without ever reaching it. Every increase in velocity requires an even larger addition of energy.

      • SLC
        Posted September 29, 2011 at 5:24 am | Permalink

        In simpler terms, energy supplied to the particle increase its mass,not it’s velocity as one approaches the speed of light. Thus, it would require an infinite amount of energy which would result in a particle of infinite mass to actually achieve the speed of light.

    • Torbjorn Larsson, OM
      Posted September 29, 2011 at 5:54 am | Permalink

      “Quantum jumps” are folk physics. Quantization of energy (quantum mechanics) or fields (quantum field theory) are precise in quantum mechanics. Velocity is a quantity that isn’t quantized, for example.

      Tunneling should be relativistic as they are described by the wavefunction in the causal quantum mechanics theory. And IIRC experiment seems to confirm this, mostly. (Again you can have virtual particle effects I believe, that seems to break causality but in the end doesn’t.)

  14. Gayle Stone
    Posted September 29, 2011 at 4:37 am | Permalink

    Victor gave simple explanation that even us “dummies” can understand. Only he now, and George Gamow in the past have had the ability to bring expanations down to our level. Bully for Stenger.

  15. Torbjorn Larsson, OM
    Posted September 29, 2011 at 5:45 am | Permalink

    It is clear from the exposition that Stenger is a member of an older generation of physicists:

    “When you read, “Einstein proved that particles cannot go faster than the speed of light” you have to understand that this was not a consequence of the basic axioms of the theory of special relativity. To prove this he introduced an additional assumption now called the “principle of Einstein causality”: cause must always precede effect. In that case, it then follows that we can’t have superluminal motion.”

    To refer to the simplest axiomatized version as “the theory” is both undue math worship and undue physics slander.

    In this case it is a bit iffy, since Einstein did too, but nevertheless: the idea that tachyons aren’t real particles comes from them acquiring imaginary energy, not that they break causality.

    That allowed Einstein to make a simple interpretation of causality, that causality is a property of real particles with real energy. It was necessary too, since the classical version of seeing the effect after the cause is no longer appropriate according to relativity. If different reference frames have the same physical laws, some observers will observe events happening in other frames in reverse order.

    So yes, physicists toyed with the notion of positrons as electrons moving backwards in time, et cetera. Nothing came out of it. Today I think it is a result of modern gauge theories (which preserves laws in the same way as relativity does) that you can’t use tachyons because the lightcones of the theories will be destroyed.

    Interestingly in this context, quantum mechanics allow instead for complex energies of virtual particles. Those are shortlived artifacts of a quantum field theory (QFT) where a field consists of relativistic particles interacting locally. Those are described by Feynman diagrams. [Disclaimer: haven’t studied QFT.]

  16. vel
    Posted September 29, 2011 at 6:35 am | Permalink

    Okay, this does not make sense, the oohing and ahhing that magically effect will suddenly preceed cause. FTL particles would given an *appearance*, to an outside observer’s perception that effect could come before cause. However, to the actual actors, this doesn’t seem to ever be the case at all, and cause always precedes effect. So, in reality, and not in subjective perception, there is nothing special happening.

  17. Diane G.
    Posted September 30, 2011 at 12:52 am | Permalink

    http://xkcd.com/955/


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