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Can virtual particles appear ANYWHERE?

  1. Feb 18, 2008 #1
    Can they appear inside a black hole? Can they appear between an electron and the nucleus? Inside a nucleus? Can two sets appear at exactly the same place? What prevents them from appearing exactly where other existing matter is?
     
    Last edited: Feb 18, 2008
  2. jcsd
  3. Feb 18, 2008 #2
    As another question can they appear INSIDE Of another particle?

    Can you have a virtual whatever-the-hell fit inside of a quark?
     
  4. Feb 18, 2008 #3

    Danger

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    I know that they keep showing up in my beer, and it's beginning to irritate me.
     
  5. Feb 18, 2008 #4

    jtbell

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    Hey, don't write them off so quickly! Remember Donald Glaser got the idea for the bubble chamber while watching bubbles rise in his beer. :biggrin:
     
  6. Feb 22, 2008 #5

    tiny-tim

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    Only real things are real

    Virtual particles appear only in mathematical calculations.
    Real particles exist. That's what "real" means. :smile: Virtual particles don't.
    Virtual particles always have momentum greater than energy, which means they'd be faster than light!
    When people say that a particular type of force is "mediated" by virtual particles (eg, photons), they mean that those particles appear in the Hamiltonian, not that they really appear.
     
  7. Feb 22, 2008 #6
    Aren't virtual particles the same as the vibrational modes of the Casimere effect - both are the zero point energy, right? If so, then since the matter of the parallel plates in the Casimere effect prevents some vibrational modes of the zero point energy (which is the same as virtual particles, right), then virual particles (vibrational modes) cannot appear were matter is. Does this sound right? Thanks.
     
  8. Feb 22, 2008 #7
    I belive this is the hawkings radiation... or am I wrong?

    Tachyon.
     
  9. Feb 22, 2008 #8
    Hawking's radiation, in simplest terminology as I understand it refers to the radiation produced at the event horizon of a black hole, wherein a virtual particle may be caught behind the event horizon however it's virtual partner escapes and is released as energy. Thus the black hole decays.
     
  10. Feb 22, 2008 #9
    ooh so virtual particles aren't some sort of undetectable particles, they simply aren't real? so when someone refers to virtual particles, is it along the same lines as refering to distance, velocity, or force; words(or numbers) which refer to changes or properties rather then actual "things"? i know, this is a total nooby question (i JUST started reading "a brief history of time" two days ago, and it's pretty much laying the foundation for my understanding of quantum mechanics at the moment)
     
  11. Feb 22, 2008 #10

    malawi_glenn

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    One thing:

    According to heisenberg: [tex]\Delta E \Delta t > \hbar / 2 [/tex]
    (HUP)

    So I have always been taught that the virtual particles "exists", but only during a time according to HUP. During that time, conservation of energy and momenta is allowed.

    Cvan: according to tiny-tim , virtual particles just show up in our calculations. So either both you and me have missunderstood virtual particles completley, or else tiny-tim is wrong :P

    friend: I was also about to about to take the Cashimir effect ;)
     
  12. Feb 23, 2008 #11

    tiny-tim

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    Are we physicists or mathematicians?

    Don't be blinded by the mathematics!

    :smile: Physicists mustn't believe everything mathematicians tell them! :smile:

    We can't detect virtual particles, not even indirectly, and not even during the HUP time - they're just a convenient way of calculating fields (forces).

    http://en.wikipedia.org/wiki/Hawking_radiation
    http://en.wikipedia.org/wiki/Virtual_particle
    No, it's even worse - different observers can agree on the distance between two objects, or at least can agree on a formula to convert one observer's measurements to another's. In that sense, distance is "real".

    But the mathematics doesn't tell you anything about where the "virtual particle" is, or when, or its velocity, or anything which could, even in principle, be measured. :frown:

    Feynman diagrams, for example (which is where most people think they've seen virtual particles!), are not snapshots - they're a convenient mathematical device for calculating the coefficients of the Dyson polynomial (they make sure that you don't leave out any terms)! :smile:
     
  13. Feb 23, 2008 #12

    malawi_glenn

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    Then what IS a force. IS the force mediated by virtual particles, or is it "just" mathematical formalism.
     
  14. Feb 23, 2008 #13

    tiny-tim

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    A force is "real", because it can be measured by physicists. :smile:

    A virtual particle can't. :frown:

    I repeat:
     
  15. Feb 23, 2008 #14

    malawi_glenn

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    I read that, but you did not answer what a force is. How is the force mediated in "real" world.
     
  16. Feb 23, 2008 #15

    turbo

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    Theoretically, we cannot detect virtual particles because they are inextricably bound to their antiparticles which cancel their properties. However, the Casimir force is a pretty good demonstration that they exist. For those not familiar, the Casimir force demonstrates that two neutral conductive surfaces that are situated near enough to one another to suppress the formation of virtual pairs with wavelengths longer than the gap between them, will be attracted to one another due to the reduced pressure between the surfaces.

    Hawking radiation is the promotion of virtual particles to real (unbound) particles when virtual pairs arise on the horizon of a BH, and one of the virtual particles is trapped by the BH while the other goes free. This argument is not as compelling as the Casimir force because it is entirely theoretical and is predicated on the reality of gravitational singularities, which may be, after all, a product of a mathematical breakdown in GR and may not exist in reality. There are other measurable effects that point to the existence of virtual particles, however, and some Internet searching will turn up examples.
     
  17. Feb 23, 2008 #16

    tiny-tim

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    A force "is" what it "is"

    I don't know "what" a force is! :blushing:

    As a physicist, I can measure a force. :smile:

    As a mathematician, I can calculate a force. :smile:

    But that's all!

    Do you know "what" time is?​
     
  18. Feb 23, 2008 #17
    Yeah, thats what I was trying to say using one sentence and key stage 2 english. :)

    Tachyon.
     
  19. Feb 23, 2008 #18

    malawi_glenn

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    I know all that tiny-tim, but:

    i. Virtual and existence is not a contradiction a priori

    ii. real and existence is not equivalent

    i.e A virtual particle is not a real particle, but we can not a priori rule out the possibility that a virtual particle can exist. Real particle exists, that we know since we can decet them directly. Virtual particles are harder to proove that the exists since we cant measure them directly. But as the Cashimir Effect has demonstrated, (as Turbo-1 also mention) virtual particles exists.

    And I would say that all physicists also are mathematicians in some sence since the language of physics is math. But not all mathematicians are physicists.

    I dont "know" what time is, since I dont have taken any advanced course in General Relativty yet, but i "know" that time is strongly connected to space, so lets skip the disscussion about time from now on.

    But if I got you right, you are arguing that " A force is a force. " We can only measure its properties, but we can not say what it is. As we say about the electron, that an "electron is an electron", it has wave- and particle properties, but on a very fundamental level, an electron is an electron. Nothing else nothing more. Have I understood you correctly?
     
  20. Feb 23, 2008 #19
    ah? A conjugate variable of mass/energy?
     
  21. Feb 23, 2008 #20
    Can't we "measure" virtual particles by measuring the force of the Cashimir Effect? We might be measuring multiple modes of virtual particles, but that's still a measurement, isn't it?
     
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