Quantum Fluctuation : Causal

Discussion in 'Physics & Math' started by The God, Mar 12, 2017.

  1. The God Valued Senior Member

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    For basics, interested may refer to wiki link.

    Points for discussion:

    1. Is this phenomenon causal?
    2. Is it simply Heisenberg Uncertainty principle on Energy/Time, then should it not be prevalent everywhere?
    3. What is the minimum and maximum possible energy of such particles? If there is any limit.
    3. Are we looking for some cause behind or the concept is fully consistent requiring no further research on basic aspects?
    4. Will the Quantum Gravity, throw some further light on this? Point is, is this concept open to change.

    (Let's exclude the standard that any theory is open to change.)
     
    Last edited: Mar 12, 2017
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  3. exchemist Valued Senior Member

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    I'm not quite sure what you mean by asking if the phenomenon is "causal". Can you elaborate? Are you asking whether it is an effect of something else, or whether it causes something else?

    As I understand it, it is effectively a manifestation of the Uncertainty Principle, applied to fields in a vacuum. I think it is in principle prevalent everywhere, but in practice its effects would be swamped by the stronger ones due to matter and radiation, everywhere except a vacuum.

    As I understand it, there are no particles in vacuum fluctuations, only "virtual particles", which are so-called precisely because they are NOT particles (!), as is made clear in this rather nice explanation: https://profmattstrassler.com/artic...ysics-basics/virtual-particles-what-are-they/

    There is something else called "pair production", which occurs with high energy photons and so forth, but as I understand it this is something distinct from the more general idea of vacuum fluctuations. I am open to correction on this though.

    Regarding the cause behind it and quantum gravity, I'm no expert on Quantum Electrodynamics, so I'll have to leave this to those that are.
     
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  5. The God Valued Senior Member

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    Yes, effect of something else.
     
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  7. exchemist Valued Senior Member

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    Ah OK. Well I suppose you might say it is due to quantum uncertainty, but really that is sort of just restating what it is, in other terms, rather than saying it has a "cause". QM has uncertainty built in, at the most fundamental level, due to the relationship between conjugate variables: https://en.wikipedia.org/wiki/Conjugate_variables

    As far as strict cause it concerned I'd be tempted to say no, it is just the way the world appears to be if the QM model is right - which seems so far to be the case.

    But let's see if more knowledgeable people can comment further on this......
     
  8. pluto2 Registered Senior Member

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    I think I read somewhere that quantum mechanics could be false though.

    However if this is true, the entire structure would collapse and humanity will be back into the dark ages.
     
  9. origin Trump is the best argument against a democracy. Valued Senior Member

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    Not sure if you were just joking...

    QM is not false. There could be parts of it that are incorrect and I am sure that there will be improvements to the theory. There may even be a radical new theory that replaces QM, but in any event the changing of a theory would not cause the calamities that you are talking about.

    GR was a radical departure from Newtonian gravity theory and we seemed to have made it through that alright.
     
  10. The God Valued Senior Member

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    The question popped in while searching around for HR. The HR is also a quantum mechanical effect, and implied cause is gravity around BH. So the specific point if Fluctuations are causal or not or don't know.
     
  11. karenmansker HSIRI Banned

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    Here's an interesting causal quantum vibrational phenomenon:

    'How does a nose generate the signals that the brain registers as smell? The conventional theory says it’s down to the different shapes of smelly molecules. But fruit flies have now distinguished between two molecules with identical shapes, providing the first experimental evidence to support a controversial theory that the sense of smell can operate by detecting molecular vibrations. '

    Excerpted from:

    https://www.newscientist.com/article/dn20130-fly-sniffs-molecules-quantum-vibrations/
     
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  12. The God Valued Senior Member

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    The wiki link on "quantum fluctuation" says..

    In quantum physics, a quantum fluctuation (or quantum vacuumfluctuation or vacuum fluctuation) is the temporary change in the amount of energy in a point in space, as explained in Werner Heisenberg's uncertainty principle.

    Uncertainty principle is a given explanation for this, but should it not have a cause behind.
     
  13. exchemist Valued Senior Member

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    Yes, that's more or less what I was thinking, when I wrote my previous post on this.

    In the QM model, position and momentum make up one pair of conjugate variables, while energy and time make up another pair. This uncertainty, or more properly "indeterminacy", is just a feature of the model - and one which is supported by observation. So at present there seems no scientific reason to challenge it, though people who are philosophically determinists, as Einstein was ("God does not play dice"), still search for ways to get over it, via "hidden variable" theories and so forth.
     
  14. The God Valued Senior Member

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    I am not challenging it. I am aware of these pairs and associated maths. Point is very simple...the cause behind fluctuation. The uncertainty principle describes the phenomenon, it cannot cause the event to happen. What is the trigger?
     
  15. exchemist Valued Senior Member

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    If you are aware of the maths I am not quite sure why you ask the question. There is nothing to trigger and no cause, any more than there is a cause for why any other measurement in QM tends to yield a range of values centred on an expectation value, rather than an exact value.

    If your question is what causes nature to have this probabilistic quality, I'm not sure anyone knows: it just is. Apparently. So far, at least.

    But I'd be interested to see if anyone else can comment further on it.
     
  16. The God Valued Senior Member

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    For something to happen, it requires trigger or cause. Can you disagree with this ?
     
  17. exchemist Valued Senior Member

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    Yes I rather think I can. Take radioactive decay. The decay of an atom is an event - it happens. But does it have a cause? Do you count the fact that the atom is less stable than its reaction products a cause? Perhaps. But then, what "causes" the atom to decay now, say, rather than next week? Nothing - it is truly random.
     
  18. karenmansker HSIRI Banned

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    What 'causes' seemingly random radioactive decay has 'cause' (a trigger) within the subquantum . . . . but since we have difficulty detecting phenomena at such subplanckian levels, it is doubtful (currently), that we will identify that trigger soon. Best to approach this domain via Casimir Effect detectors, base frequency E and M harmonics, etc. IMHO.
     
  19. The God Valued Senior Member

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    Iop.org has this..


    Radioactive decay occurs in unstable atomic nuclei – that is, ones that don't have enough binding energy to hold the nucleus together due to an excess of either protons or neutrons. It comes in three main types – named alpha, beta and gamma for the first three letters of the Greek alphabet.
     
  20. exchemist Valued Senior Member

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    Yes, but so what? That explains why they have a tendency to decay but it does not provide a cause for why a given nucleus should decay at one instant rather than another. It is an intrinsically random process, driven by QM randomness (vacuum fluctuations again).

    I think at this point in science we just have to acknowledge there is an element of intrinsic randomness, i.e. lack of causality, in what we observe at the quantum scale. It is apparently the way the universe is - and we are back to Feynman's speech about going to another universe if we don't like it.
     
  21. The God Valued Senior Member

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    Feynman is gone to another universe, probably to check.

    Anyways, this will take us to the sore point of causality in QM, which will not be concluded, and will be forced Feynman way. But I think cause-effect is something which is very dear to nature notwithstanding Earthly Feynmans fiats.
     
  22. exchemist Valued Senior Member

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    Haha, very good!

    Your philosophical point about the drive to seek cause for observed effects is surely the heart of scientific enquiry. Nobody would argue with that at all.

    But in science there also comes a limit to what we can infer as cause, because speculations that cannot be tested by observation cease to be scientific - and there are limits to what we can observe.
     
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  23. Schmelzer Valued Senior Member

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    Despite Feynman, there are causal interpretations of quantum theory. Feynman did not like them, because they were not Lorentz-covariant. They violate Einstein causality. And this is unavoidable, any causal interpretation has to violate Einstein causality, because with Einstein causality you can prove Bell's inequality, which is violated by quantum theory.
     

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