Action at a distance

Discussion in 'Physics & Math' started by cephas1012, Feb 28, 2004.

  1. cephas1012 Registered Senior Member

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    It is my understanding that physicists have used the idea of virtual particles get rid of the need for "spooky" action at a distance. For example electrons and protons would exchange virtual photons to transmit the electricmagnetic force as oppose to some force field acting on them from a distance. Correct me if I am wrong about any of this. I have a few questions about this idea though.

    1. How can transmitting a particle draw two particles closer together, such as an electron and a proton?

    2. How would the particles "know" the other particle is there in order to send out the virtual photons?

    3. Are virtual photons different from real ones?
     
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  3. AndersHermansson Registered Senior Member

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  5. lethe Registered Senior Member

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    not quite. physicists use classical field theory to get rid of spooky action at a distance.

    this means, for example, instead of a charged particle instantly setting up an electric field throughout all of space instantly, the electric field obeys a local wave equation, the electric field propagates from point to point, locally, as governed by Maxwells equations. thus, already with Maxwell in electromagnetism, Coulombs "action at a distance" law is replaced.

    Newton first coined that phrase with regard to his Law of Gravitation. it was not until Einstein formulated GR that we had a local field theory that described gravity. but this was done in the 1920s, and since then, action at a distance is a historical relic only.

    this has nothing to do with virtual particles, which are a result of quantum theory.


    it follows from the fact that the electromagnetic field is a vector field that it can make attractive and repulsive forces. scalar fields and second rank tensor fields like gravity can only make attractive forces.

    i don't really know an intuitive explanation of this fact, but if you like, i can show you calculations to prove it.

    again, this has nothing to do with virtual particles necessarily.

    i have read a description of this phenomenon on the physics FAQ, but i didn't find it particularly enlightening. i guess this question comes up a lot though. the reason is, i suppose, that it is very hard to see how exchanging particles can result in an attractive force, but this is because you are thinking of virtual particles classically. a virtual particle is really a quantum fluctuation, so this kind of thinking can lead you into trouble.

    you should read the FAQ, which answers just this question.

    this question is also answered in the FAQ

    yes, they are. a real photon is a quantum of energy of the electromagnetic field which obeys Maxwell's equation in the absence of matter. that is to say, it is a free field quantum, it does not interact with other photons or charged matter.

    when there is charged matter present, this real photon is only an approximation, since the electromagnetic field should obey Maxwell's equations with charged matter. so photons that are asymptotically free, we approximate with real photons, and to account for their interactions, we apply quantum fluctuations call virtual photons (which do not obey Maxwell's equations) of the electromagnetic field on top of the real photons (which obey Maxwell's equations with no matter)

    Maxwell's equations are classical equations, and therefore need quantum corrections. this is what the virtual photons do. particles that obey their equations of motion are call on-shell, and particles that do not are called off-shell. (the shell refers to the mass hyperboloid in momentum space)
     
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  7. AndersHermansson Registered Senior Member

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    Iik, I was way out of line

    Please Register or Log in to view the hidden image!

    I'm going to stfu now for about five years or so.
     
  8. beta Registered Senior Member

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    >>1. How can transmitting a particle draw two particles closer together, such as an electron and a proton?

    A virtual particle with a known momentum can be regarded as a plane wave occupying all of space. It has a probability of being anywhere within this wavefunction, so momentum can be transfered to a charge in a direction such that attraction or repulsion can occur.

    >>2. How would the particles "know" the other particle is there in order to send out the virtual photons?


    The virtual particles do not know the polarity of the other charge until their wavefunction interferes with that charge. The wavefunction of the virtual particle is determined by the originating charge, so information regarding the originating charge (carried by the virtual particle) then interferes with the wavefunction of the other charge.
     
    Last edited: Feb 28, 2004
  9. Zarkov Banned Banned

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    657
    >> A virtual particle with a known momentum can be regarded as a plane wave occupying all of space.

    So waves are in and fields are out ???

    >> It has a probability of being anywhere within this wavefunction, so momentum can be transfered to a charge in a direction such that attraction or repulsion can occur.

    And if it just happens not to be where it should at the exact time... we would see anomolies... we don't.
     
    Last edited by a moderator: Feb 29, 2004
  10. beta Registered Senior Member

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    >> A virtual particle with a known momentum can be regarded as a plane wave occupying all of space.

    >So waves are in and fields are out ???

    When considering particles with a known momentum (lets say we know it to an arbitrary precision), then we can relate this to its position, as shown by Heisenberg Uncertainty. The position-space wavefunction then identifies the probability of finding that particle within a certain location.


    >> It has a probability of being anywhere within this wavefunction, so momentum can be transfered to a charge in a direction such that attraction or repulsion can occur.

    >And if it just happens not to be where it should at the exact time... we would see anomolies... we don't.

    When analysis is made of the resultant momentum-space wavefunction, (prior to squaring ), consideration is given to the 'no hit' scenario for the final momentum transfer.

    >Basically physics has been and still is a mess re this

    Zarkov, read the article as referenced by Lethe (FAQ). It's quite user friendly and might explain some of your questions.
     
  11. Zarkov Banned Banned

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    Thanks for the censure James R.

    Obviously you hold quite a grudge.

    Because there is no "freedom to discuss" in this stream of this forum... bye
     
  12. Nasor Valued Senior Member

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    Zarkov you're free to start a thread about your theories, but the way in which you go around inserting your crackpot ideas into everyone else's threads is simply obnoxious. You already have a thread for discussing your 'alternative' ideas. Keep them there.
     
  13. Zarkov Banned Banned

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    Hi Nasor, so now I am not allowed to coment. except in posts stared by Zarkov???

    .. this is nazi behaviour.... you do not have to read my posts if you do not want to.

    I do keep on topic... I am controversial, ... why are you so scared.... because you know you are wrong, perchance?

    I see very little true considered scientific debunking of my assertions and science... all I see is posts like yours,,, totally off topic and derisory.


    This is curious for me, seems I really am stricking a nervous set of people, who are unsure of their science.

    BOO !!!!

    LOL

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  14. Nasor Valued Senior Member

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    I'm not afraid of you Zarkov, I just think that you're rude and annoying. Tell me, how many college-level math and physics classes have you had? How many graduate-level classes? What were they? Since I'm guessing the answer is 'none,' I can't imagine why you would think that you're qualified to discuss something like this.

    It isn't 'nazi behavior' for people to only answer question that they're knowledgeable about, it's just common courtesy. You don't see me running around trying to answer people's questions in the biology forum. Why? Because I recognize that I don't know much about biology.

    The fact that you interpret people's hostility toward you as a sign that we're insecure and feel threatened by your crackpot ideas is proof that your arrogance truly knows no bounds. Did it ever occur to you that maybe people here don't like you simply because you're obnoxious?
     
    Last edited: Feb 29, 2004
  15. cephas1012 Registered Senior Member

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    Thanks for the replies everyone. And thanks for the link lethe. I will respond with more questions if I have any after I finish reading the faq.

    Oh, one thing I can ask now is if I you (lethe) could possibly show me an example of how one would do a calculation with virtual particles. Like two electrons or an electron and a proton exchanging one. I don't know that much quantum mechanics yet, but I like being exposed to it. I will probably be taking my first official course in it sometime next fall.
     
  16. matterdoc Registered Senior Member

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    'Action at a distance through empty space' is the worst assumption in physics. Many alternatives were suggested in the past to overcome this dilemma. Currently we use many types of media (like; fields, imaginary constructs, virtual particles, etc.) to transfer effects. However, none of them satisfied logical requirements. It is imperative to have a physical medium between matter-bodies for their interactions. Kindly refer http://vixra.org/abs/1007.0042
    Nainan
     
  17. origin Heading towards oblivion Valued Senior Member

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    Matterdoc, would you please stop spamming your paper all over this forum, this site is not here for you to advertising yourself!
     
  18. chinglu Valued Senior Member

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    1,637
    Here is a sentence from your "theory".

    Please demonstrate using GPS how this "universal medium" operates with light.

    Thanks.
     

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