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Physicists Propose New Kind of Quantum Tunneling 163

Posted by ScuttleMonkey
from the good-ideas-debunked-the-fastest dept.
KentuckyFC writes to tell us that scientists from the UK and Germany are proposing a third kind of quantum tunneling. They propose that a quantum particle is capable of changing into a pair of "virtual particles" capable of passing through a potential barrier before changing back. The supposition also provides some interesting methods of possibly testing string theory. So many interesting and useful possibilities, I guess that just means it will be debunked faster than other scientific theories.
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Physicists Propose New Kind of Quantum Tunneling

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  • by phantomfive (622387) on Tuesday April 21, 2009 @03:38AM (#27657029) Journal

    So many interesting and useful possibilities, I guess that just means it will be debunked faster than other scientific theories.

    Your glass the wrong size often there, mate?


    A good percentage of us believe FTL travel is possible. You came to the wrong place with that attitude.

    • by who knows my name (1247824) on Tuesday April 21, 2009 @03:59AM (#27657123)

      Does anyone else get an uneasy feeling about the use of the word debunk in the summary?

      • Re: (Score:3, Interesting)

        Lets face it, if FTL travel isn't possible, the human race is doomed. Therefore, having the attitude that it is impossible is not useful to anyone. I know that as a scientific mind, you're supposed to follow logic and precedence. But if you plan to make a groundbreaking discovery, you pretty much have to chase what's believed to be impossible.

        If there's any limitation to the scientific mind, it's that it dismisses the far out there, which is (sometimes) the next step forward.

        • Lets face it, if FTL travel isn't possible, the human race is doomed

          Why? If FTL is impossible then it is unlikely that there will be a single human civilisation spanning the galaxy, but that doesn't preclude interstellar travel. Even at 10% of the speed of light it would be possible to colonise the entire galaxy in as little as a million years; a small fraction of the time that life has existed on this planet and much less time than some of the previous dominant species have survived.

          • I wonder if we'd be able to proliferate quickly enough, however, to prevent ourselves from being wiped out by a catastrophic occurrence in our local neighborhood within our galaxy. Say, a supernova a few hundred light-years away.

            • by RsG (809189)

              Broadly speaking, if we can cross those distances at a reasonable sublight pace, we've clearly already solved that problem.

              Travelling at high speed through interstellar space exposes the spacecraft to deadly levels of radiation. Remember that space is not strictly a vacuum, and motion is relative, so at 0.5c every hydrogen atom you cross paths with is, from your frame of reference, hitting you at half the speed of light. The faster you go, the worse this problem gets, to the point where at near light spee

        • by rbanffy (584143)

          "Lets face it, if FTL travel isn't possible, the human race is doomed."

          That's not a valid assumption. It is absolutely viable to colonize planets around other stars with slower than light travel. It's just not practical to do round-trips. There probably are many viable rocks within a 20 light-year radius.

          We need the kinds of non-reactive propulsion needed to propel spaceships to the speeds needed to reach their destinations before the grand-grandchildren of the crew forgets what they are doing.

          Without FTL,

          • I'm not completely convinced that 20 light-years is nearly "far enough".

            • by rbanffy (584143)

              20 light-years is about by Wolf 562. There are about 5 stars with detected gas giants around them in this radius, about a dozen without them but with no data on smaller rocky planets we can't yet detect.

              There must be plenty of rocks we could live on within this distance. I don't say Earth-like planets, because we would need to replace the whole biosphere with something that doesn't want to kill itself by eating reciprocally toxic earthlings, but Ganymede and Europa-like bodies with low gravity, plenty of wa

    • Re: (Score:2, Insightful)

      by Fleeced (585092)

      So many interesting and useful possibilities, I guess that just means it will be debunked faster than other scientific theories.

      Your glass the wrong size often there, mate?

      Not necessarily... the more exciting an idea is, the more interest it attracts, and so the quicker its ideas are either proven true or false... or, since we're dealing with quantum physics, we'll discover a whole bunch of other stuff which makes absolutely no sense, but is nonetheless true.

      • by TheRaven64 (641858) on Tuesday April 21, 2009 @07:43AM (#27658033) Journal

        Not necessarily... the more exciting an idea is, the more interest it attracts, and so the quicker its ideas are either proven true or false.

        Ideas in physics are never proven true. They are shown not to contradict any existing evidence, that is all. I can't think of any more than a few decades old which have survived even this. The best most theories can hope for is being shown to be a reasonable approximation within certain constraints. Eventually it may be possible to find a theory which both makes meaningful predictions and isn't contradicted by experimental results for a much longer time, but this hasn't happened yet and is unlikely to for quite a long time.

        Physics is not about finding things that are 'true' it is about finding things that make useful predictions. Newtonian motion is not 'true', but it makes predictions that are sufficiently accurate (as long as you are not travelling at more than a tiny fraction of the speed of light or near a very large gravitational force) that we can use them.

        • Ideas in physics are never proven true. They are shown not to contradict any existing evidence, that is all. I can't think of any more than a few decades old which have survived even this.

          I may be a bit behind the times, but the Law of Conservation of Energy comes to my mind pretty quickly.

          • Conservation of momentum, maybe (baring some quantum effects). Conservation of energy is violated on the microscale all of the time, but in aggregate it cancels out.
            • by RsG (809189)

              That doesn't really contradict what he said. The net energy is still always conserved, even if locally it appears to be violated. From a "big picture" point of view, wherein we consider local quantum effects in relation to one another, not just by themselves, conservation is as true now as when we first proposed it.

              Conservation of mass/energy goes back how far? The concept of mass equivalence is Einstein's era (more or less), but the concept of conservation in the first place is nineteenth century. Cert

        • Ideas in physics are never proven true.

          The insight above is basically the philosophy of science of Karl Popper. Theory implies experimental predictions. If experimental predictions are false, then theory is false.

          Then Thomas Kuhn pointed out that it's even worse than that. Really, it goes: Theory+Auxiliary Assumptions => prediction. If prediction=false, then (theory=false OR auxiliary assuptions=false).

          The OR in that statement can never be completely eliminated. For example, if you assume there is a small invisible planet somewhere insid

        • Ideas in physics are never proven true. They are shown not to contradict any existing evidence, that is all. I can't think of any more than a few decades old which have survived even this.

          I can: Relativity (both Special and General) and Quantum Mechanics. These have been around for over 100 years (since 1905). SR and quantum theory are the two most precisely tested scientific theories ever.

  • Is real but rare (Score:5, Informative)

    by physburn (1095481) on Tuesday April 21, 2009 @04:00AM (#27657125) Homepage Journal
    This won't be debunked, its true. Once you look at the feynman diagrams its obviously a possible effect. Trouble is, it will have a very low probability, at each end of the conversion possible you've got two weak force vertices, and one of the heavy 80/90 GeV/c^2 W or Z weak force carriers. So the total amplitude goes as E^2/M_w^2 g_w^4 and square that for a probablity. So for photons that might need to tunnel (optical frequencies about 1eV) you have a tunnelling probability of 10^-18, that so very rare physicists will probably never see it.

    .

    Quantum Mechanics [feeddistiller.com] feed at Feed Distiller, come there and make your own feeds

    • What I am curious about is: assume you get the virtual particles which then tunnel: what is the probability that they will tunnel with the same probability, then recombine properly? It seems to me (without having done the math), that there is some possibility here of ending up with a quantum Goretex, or, in other words, a Maxwell's Demon of sorts, no matter how small its effect might be.
    • Re: (Score:3, Insightful)

      by Anonymous Coward

      "This won't be debunked, its true. Once you look at the feynman diagrams its......"

      And even though everything else may be uncertain, and a thoery which predicts everything down to the smallest bit of truth is lacking, you state with confidence that anything found in feynman diagrams must be true?

      Models are just models.

      • by corsec67 (627446)

        Models are just models.

        Maybe, but some [ipernity.com] are better looking than others.

        /note to self: it might be a bad idea to post while drinking...

      • by rbanffy (584143)

        There is no such thing as "true" in Physics. There is "fits the measurements" and "doesn't fit the measurements".

    • by damburger (981828)

      You can't say 'it is true' if it hasn't been observed. Just because it falls nicely out of the maths, doesn't mean it corresponds to a physical reality. Hell, string theory has some nice maths to it.

      Because it would be incredibly rare even if it did happen, it being forbidden by some currently unknown physics would not have been noticed before now.

      • by earlymon (1116185)

        Just because it falls nicely out of the maths, doesn't mean it corresponds to a physical reality.

        I don't think you really know that, one way or another.

        I remember my theoretical calculus prof threatening to fail me if I didn't give up the idea that when Reimann was referring to dimensions greater than 3, he really did mean, dimensions. For me, it all fell out of the math and had to be reality.

        Our search for the subatomic has opened the door for understanding our universe in many dimensions - latest M theory, anyone?

        So, I'm just saying - maybe you're on a roll...

    • Wrong Diagram! (Score:3, Informative)

      by Roger W Moore (538166)

      This won't be debunked, its true. Once you look at the feynman diagrams its obviously a possible effect.

      If you read the paper and not the very bad summary in the article - along with a wrong diagram - then this is not what they are suggesting. They calculate the neutrino digram shown in the article and which you estimated and come up with a probability of O(10^-130) times a function of the neutrino mass, barrier thickness and photon energy. This would be an interesting way to measure neutrino mass if the probability were not so low.

      What they are actually wanting to test is whether there are new, fractiona

  • cat (Score:5, Funny)

    by RuBLed (995686) on Tuesday April 21, 2009 @04:07AM (#27657141)
    Great!... Now we need to not only guess if Schrodinger's cat is alive or dead but also if it is still inside the box as well.
  • by Anonymous Coward on Tuesday April 21, 2009 @04:09AM (#27657155)

    I just tunnel over SSH. It works fine...

  • by dltaylor (7510) on Tuesday April 21, 2009 @04:14AM (#27657177)

    From the paper, it looks like this is enough stronger than a hypothesis, to justify the appellation "theory". There's enough information to build detectors that can discriminate the rate of tunneling (if any, of course) between this virtual particle mode, the conversion mode, and "classical" (uncertainty) tunneling.

    Time for the experimentalists to take their shot at confirming/denying this one.

    One question, though, about the conversion mode: where's a reference for a description of the impetus for the conversion? Is it a sort of uncertainty where the "current" mode of the particle is one of the allowed states of its energy, an oscillation like neutrinos, or does the string (if you go there) pick up energy from an extra-dimensional impact (changing its "tune") then release it in another impact or emission to return to the previous state?

    • There is no "impetus" for the conversion; it is simply a matter of probability.
    • From the paper, it looks like this is enough stronger than a hypothesis, to justify the appellation "theory".

      They are suggesting a new type of charged particle that somehow we have not seen - the diagram in the article summary is the wrong one, you need to read the paper. As such it is extremely hypothetical and, unless the experiment is trivial (and at the sensitivity levels suggested I'm not sure that it is), it would be good to see some evidence that these new charged particles are consistent with the ultra-precise g-2 experimental results testing QED. There are also precision K and B physics experimental data

  • by mrRay720 (874710) on Tuesday April 21, 2009 @05:32AM (#27657457)

    They already don't quite understand the two types of quantum tunneling they already have, and they want to have a third? Everyone knows that you get your existing shit in order before you go expanding, especially in the current economic climate. Like two types isn't enough already anyway!

    Who do they think they are, string theorists??

  • by paiute (550198) on Tuesday April 21, 2009 @07:37AM (#27658003)

    I object to using the term debunk when referring to disproving a scientific hypothesis that was put forth in good faith by those willing to have it tested. The word debunk means to expose bunkum - which originally meant empty speech and which came to mean claims made by people who knew they were spewing crap.

    The proposed model may turn out to exist only in the brain of a couple of overcaffeinated physicists, but it is not bunkum and cannot be debunked.

  • by RevWaldo (1186281) * on Tuesday April 21, 2009 @08:03AM (#27658203)
    Theoretical physicists do come up with their best hypotheses on 4/20.
  • I find it interesting that I browse a site that casually has a story like this: "They propose that a quantum particle is capable of changing into a pair of 'virtual particles' capable of passing through a potential barrier before changing back" sandwiched between two stories about video games, as though they both belong in the same broad category (of "nerdy" or something).

  • I believe it's actually the fourth. Quantum macroparticle tunneling [trygve.com] was first documented in 1987.

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