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Double slits and virtual photons

  1. Aug 5, 2004 #1
    A while ago I was reading David Deutsch's book "The Fabric of Reality".

    Deutsch proposes that the double slit experiment is explained by the presence of large numbers of virtual photons, which leave the source, hit the wall, travel through the slits, and interfere with each other, much the same as real photons (if there are enough of them).

    Then the real photons being emitted individually interfere with this virtual photon field and the characteristic interference field is produced.

    From what I recall, Deutsch states that this is the only way of plausibly explaining the double slit experiment.

    What do you people think about the idea?
  2. jcsd
  3. Aug 5, 2004 #2


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    Looks to me like going along the same lines as a theory I've been debunking in TD - see https://www.physicsforums.com/showthread.php?t=37087 Virtual photons are nothing but the manifestation of electric and/or magnetic fields - how do you suppose photons could interfere with that?
  4. Aug 5, 2004 #3
    <<Virtual photons are nothing but the manifestation of electric and/or magnetic fields>>

    Think some more.
  5. Aug 5, 2004 #4


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    Actually I'm suprised you haven't heard of David Deutsch, despite having ideas that are regarded as 'unorthodox' (to put it nicely) by many in the physics establishmnet, he is a professor at no less place than Oxford University and still commands quite alot of respect.

    I have read David Deutsch's book (not all of it tho', it's interesting and the man is undoubtly very, very clever, but slightly off his rocker. I couldn't help smirk a little at his transcripted converstaions with the 'crypto-inductivist'). What he is actually proposing is not related to virtual photons; he proposes a variation on the MWI in which interference patterns such as those seen in the double slit experiment are caused by the ineractions of real photons and what he calls 'shadow photons'.

    Clearly in order for his shadow photon theory to be correct it must be consistent with the quantum formalism (or at least give predictions that match thos eof the quantum formalism is most situations, tho' I believe the shadow phton explanation is just menat to be an ontology for the quantum formalism) and notwithstanding the Ashfar experiment it must be consistent with the Copenhagen interpreatation, etc. So no, it isn't thge only possible explanation.
  6. Aug 6, 2004 #5


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    Ok. Let me rephrase that then. Virtual photons are nothing but the manifestation of electric and/or magnetic fields. If you want to say otherwise, make your case, although odds are it'll get busted to TD.
  7. Aug 6, 2004 #6
    I apologise for using the term "virtual photon" rather than the correct term used by Deutsch of "shadow photon".

    jcsd, I didn't get through all the book either. I stopped reading it around about when he wrote that philosophers are in the business of cooking up believable sounding arguments to keep the public satisfied. (Disclaimer: this statement is inevitably coloured by my own memory.)

    anti crank, didn't you read jcsd's reply before posting #5? The correct term is "shadow photon", and then we get into issues of what a "shadow photon" is. We are allowed to spend some time thinking about it, and it is best if we are flexible in our thinking.

    Are there people who have considered opinions on shadow photons, and on their validity or otherwise? I would welcome hearing from you.
  8. Aug 6, 2004 #7
    real photons are the manefestation of EM fields. i dont think anybody knows what virtual photons are... in fact, i'm not too sure anybody knows what real photons are either :-)
  9. Aug 7, 2004 #8


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    I must confess that in this case I am at a disadvantage, as I have not heard of Deutsch or shadow photons. While I will look for that book in my university's library, I doubt I'll have time to give it a full read, as I have plenty of work already
    As for virtual photons.... I've no idea whether they exist or not. But classically, the force between charges is mediated by electric or magnetic fields, and in QED by virtual photons, hence my assertion. However, in this case, I would appreciate being taught a lesson myself if there are any experts on quantum field theory here to give it.
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