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Does anything actually move?

  1. Jan 31, 2008 #1
    I have been told that nothing actually moves through space at the smallest level in the quantum field. Instead the eneregy/properties from one are transfered to another. Is this true ? do our hands and bodies literally move or do we 'morph' through space like pixles on a tv screen
     
  2. jcsd
  3. Jan 31, 2008 #2

    ZapperZ

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    Who told you this?

    For future references, whenever you want us to explain things that you read, heard about, or were told, you must cite the source. Or else, we only have your interpretation of what you read, heard, or were told to go by.

    Zz.
     
  4. Jan 31, 2008 #3
    LOLLOL I have no ****ing clue about Quantum mechanics on this level and yet I ahd this exact thought for some reason the other day based on absolutely NOTHING to do with qm. WTF
     
  5. Jan 31, 2008 #4
    Sorry im a bit new to this - to be honest I cant remember the source but I would LOVE any enlightenment on the subject either way as its been bugging me for ages.
     
  6. Jan 31, 2008 #5
    According to quantum theory particles only exist at a particular point in space at the exact moment of measurement. At other times the existance of the particle is undefined. At least, that's my interpretation of the theory. This means that particles can move from place to place without existing in between. This would only be true for quantum systems though, and wouldn't be true for the system of interdependent particles that make up your arm.
     
  7. Jan 31, 2008 #6
    So basically, when I move my arm, I move it, it's not like what makes up my arm are exchanged with whatever was in the place I moved my arm to? lol
     
  8. Jan 31, 2008 #7
    Yes, when you move your arm, you actually move it, the particles in your arm are not replaced. Things really do move. I'd really like to know who told you that too, if you can remember.

    Maybe you confused it with this - 'things never touch, the magnetic fields on the atomic level repel each other so that the subatomic particles never actually contact each other.' I've heard this from quite a few sources, namely philosophical discussions surprisingly enough. Of course, the 'never' in that statement can be taken loosely as we can collide certain particles together.
     
    Last edited: Jan 31, 2008
  9. Jan 31, 2008 #8
    I'd be inclined to play devil's advocate here and say that on the atomic level there is no way of telling if an atom that moved from one place to another is still the same atom. It may be indistinguishable from the previous atom, but that doesn't mean it's the same atom does it? The fact that (according to quantum theory) the atom didn't exist in between lends weight to the argument that the atom in its new position is actually a comlpetely new atom.
     
  10. Feb 2, 2008 #9

    Mentz114

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    Yes it does. That's what indistinguishable means.

    It seems to be an unnecessary complication to think that everything has to be destroyed and recreated everytime it moves. Sounds like an idea that would appeal to mystics.
     
  11. Feb 2, 2008 #10
    I don't know, the pixel analogy sounds pretty good for describing CI's idea that inbetween measurements of a maximal resolution (i.e. pixels) no one can say what is happening.
     
  12. Feb 2, 2008 #11
    Why?
     
  13. Feb 2, 2008 #12
    Mystics or Metaphysics?
     
  14. Feb 3, 2008 #13
    I think it is time to mention the term 'tunneling', where something may appear at a new location without being able (AFAIK) to be located in the in-between locations.
     
  15. Feb 3, 2008 #14

    ZapperZ

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    No, I don't think we should talk about tunneling, because the same can be said about any QM system described by plane-wave states.

    Note that if I put magnetic particles in a tunneling barrier, I can affect the tunneling properties of electrons tunneling through that barrier in the form of an increase in inelastic tunneling (versus the regular ballistic tunneling). Thus, this already tells you that the electrons had to pass through that "in-between locations", or else, why would it matter that I had magnetic particles in the barrier?

    Zz.
     
  16. Feb 3, 2008 #15
    How then, if I may ask, is the electron able to ignore the forces that would keep it on its side of the barrier?
     
  17. Feb 3, 2008 #16

    Mentz114

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    ColorSpace:
    This is the mysterious part of QM. Things do tunnel, and 'ignore' barriers. No point asking how, it just happens, and has been experimentally tested.
     
  18. Feb 3, 2008 #17

    ZapperZ

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    It doesn't "ignore" it. That's why there is a "potential barrier". But since the description of the electron involves "wavefunctions", it includes the ability to penetrate through the barrier. That is part of the mathematical formalism, and in QM, the formalism comes first ahead of any kind of physical interpretation that we want to put into it.

    This also has nothing to do with your assertion that it doesn't move through the barrier, because I could also ask you the same question on how your electron is able to ignore the "forces" to simply skip the barrier and appear on the other side.

    Just as a reference, I've actually performed both ballistic and inelastic tunneling experiments on conventional and high-Tc superconductors, including changing the nature of the insulating tunnel junction. So that's why I'm quite familiar with this.

    Edit: I'm including a reference for the inelastic tunneling that I mentioned earlier:

    J.R. Kirtley and D.J. Scalapino Phys. Rev. Lett. 65, 798 - 800 (1990).

    Zz.
     
    Last edited: Feb 3, 2008
  19. Feb 3, 2008 #18
    By coincidence, I just found this quote in Bohm & Hiley "The Undivided universe", page 50:

    To be honest, I don't understand very much of what is said here, however it kind of sounds like it might be a good response to your objection. :)
     
    Last edited: Feb 3, 2008
  20. Feb 3, 2008 #19
    I would have said that there's some validity to the interpretation suggested in the OP because of the requirement that we take seriously the indistinguishability (is that a word??) of fundamental particles. As we all know, you don't get the right statistical behavior for particles unless you consider the process A+B -> A+B to be the same as the process A+B -> B+A, in other words, saying that electron A ends up here and electron B ends up there is indistinguishable from the reverse, because electrons are indistinguishable.

    With all that said, however, I don't see any value in asserting that my movement through space is better described as the transfer of my electrons' properties to the electrons of the air through which I was moving. The only meaningful way I could think of to identify "my electrons" is to say that they're ones currently interacting with all the other particles in my body. I don't know what it means to say that they're not the same ones I had two minutes ago but are different ones with the same properties.
     
  21. Feb 3, 2008 #20

    ZapperZ

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    No, it isn't. Because it is the same thing as the "phase slip" that we observe in superconducting loops in SQUIDs. You are then faced with trying to explain how affecting something doesn't affect it, which is an oxymoron.

    Zz.
     
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