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Quantum physics tells us that even a perfect vacuum be populated by "virtual" pairs of subatomic particles. I have read that these particles are allowed to violate the Conservation of Matter and Energy because they do so for such a short amount of time before annihilation that they don't count. I don't buy it. As we.have established that "Virtual Particles" are "real" (by virtue of the fact that well known processes don't occur with out them) . The question still begs. As no conversion is 100 percent efficient ( a photon is still left in our reality even after annihilation) To preserve the laws of physics, the energy to create them must come from somewhere. * .Given this, I have two questions:

  1. Have " virtual" pairs ever been observed and/or isolated?

  2. Where do "virtual" particles come from? (As they would have to come from somewhere to satisfy conservation; regardless of how short a time they spend in our universe.)

    • post is edited and reflects (to clarify what I am asking) information discussed below where Question 1 is answered. Question 2 remains.
user33995
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  • Duplicate? https://physics.stackexchange.com/q/205674/ – D. Halsey Sep 04 '18 at 22:09
  • Also related: https://physics.stackexchange.com/q/30003/44126 – rob Sep 04 '18 at 22:09
  • @user33995 Niether of those questions Observation or Origin are addressed in the flagged questions. – user33995 Sep 04 '18 at 22:26
  • Virtual or not, there are always photons (particles) in the vacuum. – Bill Alsept Sep 04 '18 at 22:37
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    Possible duplicate of Energy conservation of Virtual Particles - Quantum Fluctuation? – knzhou Sep 04 '18 at 22:57
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    You are right that this story doesn't make sense. Almost every single thing in it is completely wrong. The actual mathematics doesn't say any such thing. Unfortunately, this is the "standard" set of oversimplifications used to explain quantum mechanics to the public. – knzhou Sep 04 '18 at 22:58
  • this isn't any more of a mystery than the first understandings of microscopic life in biology. Before the microscope, it was nearly impossibly to fathom life so small it was invisible to the human eye. "How is that possible??" or the first understandings of the spread of infectious disease when nothing visible was passed from one person to another. "How can that be??" so... "Vacuum" doesn't mean absolute nothingness. It's simply absolute nothingness plus the "quantum vacuum". That's a discriptive formula. – user12711 Sep 04 '18 at 23:41
  • @Bill . My point exactly. If the particles enter (our existance and leave ANY energy at all, then there must be some "place " the particles come from no matter how fleeting their existance here. – user33995 Sep 04 '18 at 23:58
  • @knzhou see edit. – user33995 Sep 05 '18 at 00:09
  • Actually, the link does not answer my question.It merely tells me not to take my own question seriously. If I did not take my question seriously, I would not have asked it. – user33995 Sep 05 '18 at 12:27

1 Answers1

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Virtual particle pairs pop spontaneously out of the vacuum and then recombine and disappear; they exist for too short a time for us to isolate the pair, separate them, and then study them. This means there is no way to "see" them directly.

Despite this, their (indirect) influence on experiments is real. There are well-understood problems in QM which, when solved without taking virtual particle effects into account, yield the wrong answer (i.e., the computed prediction does not match experimental data). Take their effects (called "quantum corrections") into account, and you get the right answer.

How good is the match between theory and experiment when quantum corrections are included? Richard Feynman described the match as like predicting the distance between Los Angeles and New York theoretically and having it match the measured answer to within the thickness of a single sheet of paper.

These things furnish physics guys with a high level of confidence that virtual particles are not just theoretical constructs without physical reality, but things that are part of the real world- specifically, what's called the quantum vacuum.

I invite the experts here to weigh in on this with specific examples of the sort I mentioned above.

niels nielsen
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    Pictures of virtual particles popping in and out of vacuum are gross oversimplifications, cf. some of the linked questions in comments above. At the core, virtual particles are just useful mnemonics when calculating scattering amplitudes in higher order perturbation theory. – Avantgarde Sep 04 '18 at 23:31
  • Neils: So like dark matter, we "know" fluctuations and virtual particles exist because if they did not. the world will not work. But that still leaves the other question. Since, matter and energy must.be universally conserved, the question begs " Where do they come from? – user33995 Sep 04 '18 at 23:42
  • the energy required to temporarily create them is borrowed from the vacuum. the loan is returned when they subsequently annihilate. energy conservation holds perfectly on timescales longer that the lifetime of a virtual particle pair. – niels nielsen Sep 05 '18 at 00:17
  • @Neil I understand that matter can come from energy and vice versa, but it still has to come from somewhere. To say that is comes from the vacuum though sounds a little off. If you will pardon the allegory, It a bit like placing an empty cup in a fish tank and saying the water is coming from the walls. Similarly then where does the energy come from since the vacuum exists in our reality? – user33995 Sep 05 '18 at 02:47
  • the behavior of what's called the quantum vacuum defies our conventional intuition, which is based on the behavior of things big enough for us to see, which means the quantum effects are ordinarily miniscule in our every day experience. the rules that you and I grew up with that define the behavior of "big" objects simply do not work in the world of the very small. have you read anything about this stuff, or is this your first excursion into this territory? – niels nielsen Sep 05 '18 at 05:04
  • My first serious excursion. I read about it a while ago but accepted the explanation that things happen so fast that it does not violate Conservation. Then I read " The Trouble With Physics" about how adding one more dimension to Space Time allows Gravity and Electricity to be interchanged. Then I gave it more thought, Since the annihilation produces energy (even if it is given back) by the Second Law of Thermodynamics, some of that energy must remain in our reality even if it is just a photon. So, for there must be a very real violation of Conservation. – user33995 Sep 05 '18 at 12:56
  • Cont... So that got me wondering, is there a " physical location" and extra dimension that would provide the source to our sink and preserve conservation. And provide the "where" in Q2 – user33995 Sep 05 '18 at 13:01
  • there's no physical evidence for any extra dimensions, and very good physical evidence for virtual particles. I'll try to get some more book titles for you which should help. -NN – niels nielsen Sep 05 '18 at 16:35
  • Thanks on the books. As for the dimensions, I agree. Which is what makes the topic so interesting. The particles are real, and their annihilation adds energy to our reality (unless I misunderstand) Then there has to be a way to reconcile Universal Conservation of energy/mass. To me it seems, by Sherlock's Axiom, this is direct evidence of another dimension. – user33995 Sep 07 '18 at 02:58
  • their annihilation returns the energy cost of having created them in the first place; energy is conserved. it gets paid back and forth, back and forth. as richard feynman once said, "what a waste!" – niels nielsen Sep 07 '18 at 03:36
  • But no conversion is 100 percent effiecent. The annilation must generate a photon that stays in our reality. Thus a miniscule amount of energy is conveyed and local conservation is violated. Which of course is fine as long as the violaton is not universal. – user33995 Sep 10 '18 at 15:03
  • this one is 100%. Lots has been written about this. – niels nielsen Sep 10 '18 at 16:50