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OMG another Virtual Particle question. Runnnn

  1. May 14, 2010 #1
    Hahaha, yeah I did a search on these forums for questions regarding Virtual Particles and it seems its "the horse thats been beaten to death with a stick". But, I still have questions so please try and answer them because the people on there are much more versed than me in physics. I am a computer software engineer but I love physics because of how mysterious it is. So, on with the questions...

    If Virutal Particles pop in and out of existence but turn into real particles when observed.. what does it mean to observe it? How do we not observe it to notice that its a virtual particle?

    Is it possible that these particles are moving so fast and are so small that they are not poping in and out of existence but just moving at an extremely fast rate to which it looks like they are poping in and out. Maybe they shoot around so fast their speed is not observable but seem to be here and there then here again.

    I guess thats all for now, I'll ask more questions once these are addressed.

    Thanks a bunch,
  2. jcsd
  3. May 14, 2010 #2
    A virtual particle cannot be observed. Ever. A virtual particle only pops up in the mathematics needed to compute physical quantities. It's actually just a tool to keep track of very complicated calculations (a very handy one indeed!).

    So the reason why these things are introduced in the first place is because of the way calculations are handled in quantum field theories. If we had a different (better and exact) mathematicalmethod the whole concept of a virtual particle can be thrown in the bin.

    In fact, there are some examples of quantum field theories which completely circumvent the need for the virtual particles as a tool.
  4. May 14, 2010 #3
    I am not sure whether this is relevant to the actual context of the original question, sometimes descriptions of Hawking radiation of Unruh temperature involve "virtual particles popping out into existence". Those correspond to actual calculations, but one should keep in mind that they are merely friendly images of the actual calculations, not supposed to describe fundamental processes. In particular in the cases of Hawking or Unruh temperature, many subtleties are swept under the rug, such as the notion of free particles in different vacua, namely different observers unrelated by a Lorentz boost call " free particle" different quantum states.

    A virtual particle popping out into existence (without further description of what we mean by that) would in flat empty space violate energy-momentum conservation.
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