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Source of Virtual Particles in Space?

  1. Feb 24, 2013 #1
    I'm trying to understand the nature of the virtual particles that exists in empty space. I understand that they 'bubble' in and out of existence, but why do they exist in the vacuum of space? If all particles spend some of their time as virtual particles, does quantum mechanics suggest that some of the subatomic particles in my body may be disappearing and reappearing in intergalactic space, contributing the expansion and acceleration of the universe (negligibly, of course)? Or do I have no idea what I'm talking about?
     
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  3. Feb 24, 2013 #2
    Trying to understand quantum mechanics using our classical, everyday, terminology takes some time....

    I'd say, briefly, virtual particles are artifacts of our mathematical models and have not been detected.

    Here is an introductory description I found in Wikipedia....

    and another:
    No one knows 'why' they exist in 'empty' space and they have never been detected. It is believed there is a vacuum energy that permeates all of space and 'virtual particles' may be part of that...see here: http://en.wikipedia.org/wiki/Vacuum_energy

    but beware, there is no evidence that virtual particles 'blink' in and out of existence nor is there a complete consensus that the Casimir effect is proof of vacuum energy...as stated here.


    .

    For more check out ZERO POINT ENERGY in wikipedia

    'suggest'..well, maybe you could extend it to your scenario....but it's not likely to happen during the limited age of this universe...It's about as likely as your glass of milk disappearing and reappearing on Venus....or on your neighbors table....You can read about a related effect," quantum tunneling", which plays a role in radioactive decay and semiconductors.

    PS: If you search in these forums [from the SEARCH] menu at the top of this page, you'll find this subject has been explained many times, many different ways....
     
  4. Feb 24, 2013 #3

    Bill_K

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    Must we go through this again? :cry:
     
  5. Feb 24, 2013 #4
    http://www.scientificamerican.com/article.cfm?id=are-virtual-particles-rea

    This is why I am so perplexed. There's a lot of ambiguity in the various things I read.
     
  6. Feb 25, 2013 #5

    tom.stoer

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    Sorry Prof. Kane - or whoever has written this text - you should know that this is WRONG! There is no violation of conservation of energy, all there is is a violation of the on-shell relation between energy energy and momentum. We have numerous threads discussing these questions.

    But to be honest I am sick and tired to comment and discuss this nonsense; sure all these experts know better, so why the hell do they always repeat the same b...sh..?
     
  7. Feb 25, 2013 #6

    JK423

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    This should be a next thread, "Why experts insist on repeating nonsense" :tongue:
    Having already a difficulty in the interpretation of QM seems not to be enough for them, they want to confuse people even more.
     
  8. Feb 25, 2013 #7

    tom.stoer

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    Good point!
     
  9. Feb 25, 2013 #8
    Ty1er: if you haven't read this discussion,and want more insights give it a try....

    https://www.physicsforums.com/showthread.php?t=671363&highlight=virtual+particles

    You'll note there are different views expressed. I happen to like Tom.Stoer's, but cannot refute all of mfb's comments either...so I try to keep an open mind.

    Also, I believe a related issue is particle production in expanding geometry...that is, how real particles emerge from the vacuum perturbations during, say, the inflationary era of our universe, and also how particles emerge in the presence of cosmological horizons, like Hawking radiation and the Unruh effect. These do NOT prove the existence of virtual particles, but there are a lot of effects for which we have that appear to be solid theories and for which any experimental evidence [observations] can be debated.

    I don't think it's mentioned much in this discussion, but we have had extended discussions about "What is a particle."..that is a 'real' particle, like a photon or an electron, and if you read any of those you'll find it's an interesting question...and the subject of active research papers.

    [I find it helpful to keep in mind what Richard Feynman said...something to the effect that 'You must accept nature as she is, absurd.' I personally think a major problem may be that it not always clear which absurdity she is allowing to be revealed to us.]
     
    Last edited: Feb 25, 2013
  10. Feb 25, 2013 #9
    I've found some more articles online, and I think I've come to the conclusion that my questions are unanswerable at the moment. The hypotheses about dark/vacuum energy that are out there have yet to become substantial theories. I'm not educated on the math that goes into this stuff, so I can't fully grasp some of these concepts until they become more concrete in the arena of science.
     
  11. Feb 25, 2013 #10

    jtbell

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    The "virtual particles are real" and "virtual particles are not real" camps agree on the mathematics of quantum field theory, and the predictions that it makes for things that we can actually observe experimentally. They disagree on the words that should be used when discussing QFT in non-mathematical language, among themselves or with laymen.
     
  12. Feb 25, 2013 #11

    tom.stoer

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    Not so sure about that. I have the impression that some virtual particle fans do not understand the formalism, its limitations and the reason why and when it fails. My impression is that some of them have not seen anything else but perturbative treatment of QED.
     
  13. Feb 25, 2013 #12
    we have plenty of answers!! You get to pick!!

    You will often discover the more finely tuned your questions the less finely tuned are answers.


    They ARE 'substantial', I think, but in the absence of agreed upon observable parameters, sorting out details is, well, theoretical. That's because we have more math than seems to fit our universe; some fits, some doesn't; The ability to make accurate predictions and verify those predictions via experimental observations is a big determinant about what people can agree upon is an appropriate 'theory'.
     
  14. Feb 25, 2013 #13

    Bill_K

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    Tom, Please don't assume that if someone disagrees with you, it is due to lack of education. There may be other reasons.
     
  15. Feb 25, 2013 #14
    Substantial in their own right, yes, but not on the level of relativity or evolution. (not yet, anyway.) Those are concepts that are clear and understandable and answer huge scientific questions. Maybe it's just the nature of quantum mechanics, but several varying and ambiguous answers don't satisfy my curiosity. I guess I'm guilty of wanting the simple answer that just isn't there.
     
  16. Feb 25, 2013 #15
    By the time you finish reading this post the particles that make you you have already disappeared and reappeared millions of times. For all practical purposes, you(your body) are not the same now as it was before you started reading this post.
     
  17. Feb 25, 2013 #16
    Via what process do you think electrons, atoms, and so forth appear and disappear instantaneously?

    What do you think the half life of stable atoms is, say, like hydrogen?
     
    Last edited: Feb 25, 2013
  18. Feb 25, 2013 #17
    Whether "real" or not, is it OK to ask questions like these?

    Do virtual particles engage in gravitational interaction while they exist?

    Sometimes questions about gravity ask things like, "What if the Sun instantly disappeared?" or "What is the impetus to initial motion for a mass placed at rest in curved space?" These questions are usually dismissed as asking about a physically impossible scenario. But what about virtual particles? Do they appear and disappear in a such a way to ask these questions of them?

    If they do, what about after they exist? Wouldn't their gravitational attraction continue to interact with distant matter long after the virtual particle no longer existed?

    This would be like the answer to the "how does gravitational influence get out of a black hole?" question where the gravitational influence is assigned to the space around the thing rather than to the singularity. If virtual particles interact gravitationally, does that influence remain after they are gone similar to the black hole?

    Is the point of pair creation allowed to have any velocity?

    Virtual particle pair creation conserves momentum, but doesn't that require that we allow the point location of the pair creation to have a velocity with respect to our observation frame of reference? If the creation points are not allowed to have relative velocities wouldn't that allow a special frame of reference in which all the pair creations do conserve momentum?
     
  19. Feb 25, 2013 #18
    1st question: They don't appear and disappear instantaneously just very fast. I am not familiar through what process is used.

    2nd question: I'm not sure i understand the question, Hydrogen is not radioactive? although some Isotopes of hydrogen are and can decay. I don't understand the relevance of your question regarding my statement?
     
  20. Feb 25, 2013 #19
    micky...my point is that stable particles do not disappear...nor reappear..as you have stated. They do not go anywhere'...

    The half life of stable atoms is waaay longer than the age of the universe....

    The body does replace it's constitutents over time but not because anything 'disappears and reappears'.....the skin, for example, sloughs off old dead surface skin and grows new from within....
     
  21. Feb 25, 2013 #20

    lots of good discussion here...
    https://www.physicsforums.com/showthread.php?t=671363

    demystifier puts it this way in one view:

    " virtual particles don't cause decoherence {nor gravity} simply because virtual particles don't exist. .."
     
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