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Thread: Heisenberg's Uncertainty Principle and Virtual Particles.

  1. #1 Heisenberg's Uncertainty Principle and Virtual Particles. 
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    HUP states that there are limits on how accurately we can measure certain physical quantities such as position and momentum. Thinking about a vacuum in outer space we assume it contains absolutely nothing and zero energy. But we can't be sure of this zero energy because of the same argument. There may in fact be energy, and this energy can produce two virtual and opposite particles which then exist for a short time before they collide and then annihilate each other turning back into energy.

    My point is this:- Many texts that I have read talk about the energy that gave birth to the particles as appearing 'out of nothing' - the context is supposed to be an absolute vacuum after all. Now HUP might well be right in saying that we can't be certain BEFORE the event that there isn't any energy in the 'vacuum'. However we can be absolutely certain AFTER the event that a vacuum didn't exist if it turned out that the space in question contained the energy from which the two virtual particles arose. And in that case the energy was already there. It didn't appear out of nothing because we now know that we didn't have a vacuum in the first place.


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    Forum Radioactive Isotope MagiMaster's Avatar
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    The argument that lets virtual particles exist also says they have to stop existing before the universe becomes aware of them (in most cases at least).


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    Very strange. It makes me wonder to what extent some theorists are prepared to make nonsense of reality in order to suit the mathematics. The abstract should only be allowed to represent the real if its conclusions are at least possible.
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    Quote Originally Posted by nimzo256
    Very strange. It makes me wonder to what extent some theorists are prepared to make nonsense of reality in order to suit the mathematics. The abstract should only be allowed to represent the real if its conclusions are at least possible.
    Virtual particles in some sense are the result of quantum field theories being perturbtive theories. They serve a purpose in that these theories produce very accurate predictions, based on the Feynman diagrams that utilize virtual particles. .

    However, the "reality" of virtual particles is something else again. They are not, even in principle, detectable as particles, but are manifested only as the forces that they mediate. One can get into a long and useless philosophical debate on the ontology associated with virtual particles. The bottom line is that as a theoretical device they produce accurate models of that which can be measured, so their independent existence is not important. A more accurate non-perturbatice theory may in the future eliminate a need for the device.
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    Quote Originally Posted by DrRocket
    Quote Originally Posted by nimzo256
    Very strange. It makes me wonder to what extent some theorists are prepared to make nonsense of reality in order to suit the mathematics. The abstract should only be allowed to represent the real if its conclusions are at least possible.
    Virtual particles in some sense are the result of quantum field theories being perturbtive theories. They serve a purpose in that these theories produce very accurate predictions, based on the Feynman diagrams that utilize virtual particles. .

    However, the "reality" of virtual particles is something else again. They are not, even in principle, detectable as particles, but are manifested only as the forces that they mediate. One can get into a long and useless philosophical debate on the ontology associated with virtual particles. The bottom line is that as a theoretical device they produce accurate models of that which can be measured, so their independent existence is not important. A more accurate non-perturbatice theory may in the future eliminate a need for the device.
    Very interesting. There seem to be gaps that science hasn't yet filled but which are bridged by maths. Attempts to provide scientific explanations lead to nonsense (eg. virtual particles are allowed to exist for a short time as long as the universe doesn't discover them - nature playing hide and seek?) as far as we're concerned but we seem to be prepared to put up with this because the maths reliably tells us what will happen.

    Interesting to think what the future will hold. Will science catch up and be able to coherantly explain why the mathematical models work, or will the maths forge even further ahead? Could it be that there are parts of reality that science just isn't capable of explaining, but can be made use of because of mathematical modelling?
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    The math is an explanation. Most laypeople want something more, but that doesn't really fall under science. It's more a question of philosophy.

    Of course, that doesn't mean scientists are completely satisfied with just the math, and many think that such weirdness is a good reason to keep looking for new ideas. That doesn't really mean that being weird makes the idea less physical than a more intuitively understandable idea though.
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    Quote Originally Posted by MagiMaster
    That doesn't really mean that being weird makes the idea less physical than a more intuitively understandable idea though.
    Absolutely right. However I can't help wondering if our success in unlocking nature's secrets using mathematics has now gone beyond our ability to intuitively understand nature.

    Take the Big Bang. Scientific orthodoxy tells us the Big Bang happened everywhere and the universe expanded into itself (the universe is everything so there was nothing else for it to expand into). Intuitively very difficult - but apparently fine mathematically.
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    It's certainly gone beyond laypeoples' ability to understand it intuitively. I think many (if not all) experts manage to get a good grasp of things though, and don't rely solely on the math. Of course, the universe isn't under any obligation to be understandable, we just hope that it ultimately is (and the successes of science suggest that it is at least mathematically describable).
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    Quote Originally Posted by MagiMaster
    It's certainly gone beyond laypeoples' ability to understand it intuitively.
    But since the average layperson is unable to balance a checkbook that is not surprising.

    Quote Originally Posted by MagiMaster
    I think many (if not all) experts manage to get a good grasp of things though, and don't rely solely on the math. Of course, the universe isn't under any obligation to be understandable, we just hope that it ultimately is (and the successes of science suggest that it is at least mathematically describable).
    Mathematics is the language of physics. Understanding is facilitated by mathematics in the same sense that understanding a novel is facilitated by English (or French, or German, or ...). People who don't understand mathematics also fail to understand the meaning of "understand".

    Those who do not understand mathematics are scientifically illiterate.

    "To summarize , I would use the words of Jeans, who said that ‘the Great Architect seems to be a mathematician’. To those who do not know mathematics it is difficult to get across a real feeling as the beauty, the deepest beauty, of nature. C.P. Snow talked about two cultures. I really think that those two cultures separate people who have and people who have not had this experience of understanding mathematics well enough to appreciate nature once." – Richard P. Feynman in The Character of Physical Law
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    Sorry, I was using the word math in the way laypeople understand it. (Which, I agree, often isn't much at all.)
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    Hmm, as a physicist, I am still surprised how mathematics - which is as I understand it an idealisation of reality - manages to describe Nature. Isn't this puzzling to anyone else? And yet, there are simple situations that mathematics cannot solve accurately.
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    Quote Originally Posted by Dishmaster
    Hmm, as a physicist, I am still surprised how mathematics - which is as I understand it an idealisation of reality - manages to describe Nature. Isn't this puzzling to anyone else? And yet, there are simple situations that mathematics cannot solve accurately.
    Mathematics is the study of any kind of order that the human mind can recognize. Any connection between mathematical models and reality is in the purview of science, not mathematics.

    You might want to read Eugene Wigner's essay "The Unreasonable Effectiveness of Mathematics in the Natural Sciences".

    http://www.physik.uni-wuerzburg.de/f.../QM/wigner.pdf
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    Quote Originally Posted by DrRocket
    Quote Originally Posted by Dishmaster
    Hmm, as a physicist, I am still surprised how mathematics - which is as I understand it an idealisation of reality - manages to describe Nature. Isn't this puzzling to anyone else? And yet, there are simple situations that mathematics cannot solve accurately.
    Mathematics is the study of any kind of order that the human mind can recognize. Any connection between mathematical models and reality is in the purview of science, not mathematics.
    Are you suggesting that the success of mathematics in physics and other natural sciences is a result of the human mind that creates models of Nature?
    Quote Originally Posted by DrRocket
    You might want to read Eugene Wigner's essay "The Unreasonable Effectiveness of Mathematics in the Natural Sciences".

    http://www.physik.uni-wuerzburg.de/f.../QM/wigner.pdf
    Thank you for the suggestion. I have read it, but I was quite disappointed, because it did not really address my problem. As soon as it got to the crucial point explaining the relation between mathematics and phyiscs, it basically did it by confirming that there is one by mentioning some impressive examples for this.
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  15. #14  
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    Quote Originally Posted by Dishmaster
    Quote Originally Posted by DrRocket
    Quote Originally Posted by Dishmaster
    Hmm, as a physicist, I am still surprised how mathematics - which is as I understand it an idealisation of reality - manages to describe Nature. Isn't this puzzling to anyone else? And yet, there are simple situations that mathematics cannot solve accurately.
    Mathematics is the study of any kind of order that the human mind can recognize. Any connection between mathematical models and reality is in the purview of science, not mathematics.
    Are you suggesting that the success of mathematics in physics and other natural sciences is a result of the human mind that creates models of Nature?
    I have no idea WHY mathematics is so successful in physics, beyond the fact that nature seems to be orderly. I only know that is does appear to yield deep insights.

    My point is that mathematics per se is not related to the study of nature. One can constrct mathematical models that are perfectly consistent and that have nothing to do with natural behavior. One can also construct mathematical models that are exquisitely accurate. The construction of accurate models is science, not mathematics. Why science has been successful in building such accurate models is a pleasant mystery.
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  16. #15  
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    Hey DrR, what happened to the bear ????
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    Quote Originally Posted by MigL
    Hey DrR, what happened to the bear ????
    You should ask such questions via PM so as not to rip the thread completely off topic, and who says Dr. Feynman is not a bear of a man?
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