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Quantum theory and the implications on human life

  1. Jan 10, 2014 #1
    Hey guys,

    I’m interested in knowing if there are any known implications of quantum theory in the macroscopic scale, regarding randomness. Small particles behave probabilistically, but that has any consequence in the macroscopic or in the microscopic (but higher scale than those particles – like molecules, etc) deterministic cause-effect world?

    Example: the position of the eletron is random by nature, but that radomness implies randomness in the orbital properties and chemical reactions that atom can make? Or the ''randomness effect'' just ends in that smaller particles?

    The undeterministic quantum world affect our deterministic world of classical physics/chemistry?

    Thank you
     
  2. jcsd
  3. Jan 10, 2014 #2

    bhobba

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    Of course it does - chemical properties are basically all quantum effects.

    For example that electrons occur in shells and chemical reactions depended on those shells.

    Even life is dependent on it. My understanding, from very dimly rememberd biology classes, is that's because carbon can form 4 bonds which is quantum mechanical in nature.

    You will probably find Erwin Schrodinger's famous What Is Life of interest:
    https://www.amazon.com/What-Life-Au...tmm_pap_title_0?ie=UTF8&qid=1389397356&sr=1-1

    Just one of its many gems:
    'The mutations are actually due to quantum jumps in the gene molecule'

    Thanks
    Bill
     
    Last edited by a moderator: May 6, 2017
  4. Jan 11, 2014 #3
    Thanks for the answer.
    I know that those quantum properties have influence on the type of chemical reactions that occur (etc), but those properties are constant right? I'm asking a different question here. My question is if the undeterministic nature of those subatomic particles implies thar our world is undeterministic (random by nature). When I say ''our world'', I mean the part of nature that influences us most (directly if you wish) - macroscopical level and bigger particles.
    I don't know if I'm explain my problem right or if it makes any sense.
     
    Last edited by a moderator: May 6, 2017
  5. Jan 11, 2014 #4

    ZapperZ

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    But are you not able to determine this on your own? When you decide to get up from your chair, did that happen, or was there some uncertainty in whether you are able to determine that you got off your chair or not?

    Our classical world hasn't changed, even after we know about QM, and it is also why many people found QM to be strange, because it doesn't fit into what we know of with our ordinary world. There are ongoing research into trying to find this boundary between the strange world of QM and the familiar world that we are used to.

    In the meantime, if you commit a crime, you cannot invoke QM as your defense.

    Zz.
     
  6. Jan 11, 2014 #5

    bhobba

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    Its an inherently unknowable question. Chaotic behavior in deterministic systems like Classical mechanics means they are for all practical purposes undeterministic. And powerful theorems from probability such as the law of large numbers show that often deterministic behavior emerges from a probabilistic basis.

    The bottom line here is given any deterministic theory one can find some kind of underlying basis for it that is probabilistic (eg QM implies classical mechanics in the classical limit) and conversely (eg Bohmian mechanics is a deterministic explanation for QM).

    Thanks
    Bill
     
  7. Jan 12, 2014 #6
    I think It's not too easy to answer your chair problem, because if the chemical reactions involved on the decision were random, you could say the action was random. Scientists don't know how to explain everything about the brain. It was just making a hypothesis. But from what I can see, altough I'm not aware of the new developmentw in that area, the evidence seems to lead to the conclusion that the brain works in a deterministic way , with classic eletromagnetism (or is not like that?). However, a lot of action we make seem to have a cause in the past
     
    Last edited: Jan 12, 2014
  8. Jan 12, 2014 #7
    Chaotic behavior function like when you throw a dice? When we throw a dice, we say It's random, but really, if we knew all the variables related to the dice throwing, we could predict the number, so it is deterministc.

    I read somewhere that the only true ramdomness is quantum mechanics. But I guess we never know if scientist will find tommorow that the particules do not behave randomly, there is pattern and function deterministically, caused by something. Or am I wrong?
     
  9. Jan 12, 2014 #8

    bhobba

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    You are on the right track.

    Does the world operate deterministically or randomly is a meaningless question. We have no way of knowing if it really depends on a deeper level that operates differently.

    Anyway this is really getting off QM and the mods will likely, correctly, close it.

    Thanks
    Bill
     
  10. Jan 13, 2014 #9
    Ok, thank you :)
    Just to finish, because this question it's not about QM: chaos theory/chaotic behavior is undeterministic in the same way scientific community accepts QM is, or is like the dice throwing I was talking about?
     
  11. Jan 13, 2014 #10

    ZapperZ

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    This is incorrect. Chaos theory and chaotic behavior are completely deterministic. The definition of chaotic behavior is that a small change in the initial parameters can result in a wildly different outcome, so that you really can't predict what will happen when you tweak those parameters. It has nothing to do with it not being deterministic.

    Zz.
     
  12. Jan 13, 2014 #11

    bhobba

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    No.

    There are two issues here that are getting mixed up.

    One issue is in a deterministic theory you can get chaotic behavior. This is when small errors grow, so in practice, even though its in principle deterministic, it cant be used to predict anything with reasonable certainty. The determinism is practically useless.

    The other issue is given a deterministic theory you can find a model where that determinism emerges from a deeper probabilistic layer - classical mechanics is an example of that where it emerges from QM. And conversely is given a probabilistic theory you can hypothesize an underlying layer that is deterministic and its lack of knowledge of initial conditions, or something like that, that leads to probabilistic behavior - Bohmian Mechanics does that with QM. What this means is its inherently unknowable if nature is fundamentally deterministic or probabilistic. It would seem to be an unknowable question.

    Thanks
    Bill
     
  13. Jan 14, 2014 #12

    DevilsAvocado

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    To get determinism; most would agree on definite properties, in the fundamental building-blocks of nature, as a prerequisite.

    Many important experiments have shown empirically that definite properties are not compatible with predictions of quantum theory, in which the Stern–Gerlach experiment is just one of them.

    https://www.youtube.com/watch?v=uqDlIgUDEIA

    This video might look contradictory, because here the classical magnets show "analog" behavior and the quantum electrons show "digital" (i.e. only up/down spin), which might be misinterpreted as definite. However, if we run this measurement in a sequence of three magnets, passing only the upper beam to the next, measuring spin along the z → x → z axis, still will result in a 50/50 up/down, after the last magnet. That's because of QM superposition of indefinite properties.

    So, what about randomness? Well, maybe the most famous experiment of all, the double-slit experiment, shows in a very apparent way that the fundamental nature of our world is intrinsic random.

    220px-Doubleslit3Dspectrum.gif

    If we run single electrons or photons, one at a time, there is no way to know in advance which slit it will go thru (not even for Bohm), and if we try to measure which slit, the interference pattern will disappear. Now, one might think that if we just had very fine-tuned and sensitive instruments, we could "sneak a peek", and get which-slit information anyway. But this is impossible. In fact, it turns out that if the laws of nature were such that they provided us with an option to mathematically determine in advance which slit the quantum particle will go thru – the interference pattern would disappear!

    Now, I leave it to you to believe in any philosophical interpretation; that states that the true nature of the world, despite of experimental facts, still is perfectly determined – we're just forbidden, by both theory & experiments, to find this "delicate fact" out ...

    Personally, I prefer Occam's[/PLAIN] [Broken] razor. :wink:

    As bhobba pointed out; quantum effects is an intrinsic part of the genetic evolution, and besides "jumps", we are bombarded with ultraviolet light and cosmic rays every second, and some might cause mutations, while others pass right through.

    If this seems to 'trivial'; why not buy a quantum hardware random number generator, and travel to Las Vegas!? :biggrin:
     
    Last edited by a moderator: May 6, 2017
  14. Jan 14, 2014 #13

    DevilsAvocado

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    Say hwuht!? :surprised This is the most outrageous thing I ever heard!! :grumpy:


    (:rofl:)
     
  15. Jan 14, 2014 #14
    Quantum uncertainty does not imply that results are truly random. Quantum states are not fully determined - and when they are resolved there is convincing evidence that "collapsed" state is not locally determined. But this is far from evidence against determinism.

    On the other side, when a quantum state collapses, there is no possibility of predicting with certainty what its state will be and the result can be used to generate a number sequence that is as random as any other known to science.
     
  16. Jan 14, 2014 #15

    DevilsAvocado

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    Do you suggest that QM uncertainty imply that results are determined?

    Do you have any evidence for determinism?

    It sure looks like true randomness to me...

    As random? Can you specify any random source that is more accurate and trustworthy than QM?? That for example, can preserve 100% true randomness for 4.47 billion years, like uranium-238??

    Do you agree that (contrary to any classical phenomena and initial conditions) we are on a theoretical level "doomed" to never predict the decay of an alpha particle in the uranium above, nor which slit an electron will go thru in the double-slit experiment?

    Because if we do – we will change the outcome of physical experiments!
     
  17. Jan 14, 2014 #16

    atyy

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    As bhobba correctly said in #11, it appears that no experiment can say whether "reality" is truly deterministic or random. Randomness and determinism can arise from each other, so true randomness or determinism are properties of theories. If we know a theory is the final theory, then we will know whether "reality" is truly deterministic or random. However, while an experiment can tell us that a theory is consistent with observations, it cannot tell us that a theory is final.

    What we can say is that quantum mechanics is a theory in which randomness is fundamental, and that all observations so far are consistent with quantum mechanics.
     
    Last edited: Jan 14, 2014
  18. Jan 14, 2014 #17

    DevilsAvocado

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    atyy, do you agree that if "the final theory" turns out to be (nonlocal) deterministic, this theory is – already by knowledge available today – handicapped in such a way that it is forbidden to make any determined predictions about QM outcomes, like in the double-slit experiment?

    Whereas if "the final theory" turns out to be intrinsic random, there is no such reservations, and we are free to dig as far as we wish into the wonders of nature.

    Agreed?

    (Personally I don't understand how a "final theory" could survive the restriction above... :eek:)
     
  19. Jan 14, 2014 #18

    atyy

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    I don't agree. Bohmian mechanics is an example of a theory that reproduces all non-relativistic quantum mechanics, and is deterministic. Bohmian mechanics predicts deviations from quantum mechanics. There is a concept of "quantum equilibrium" in Bohmian mechanics that is analogous to the concept of "thermal equilibrium" for classical mechanics. The apparent randomness of quantum mechanics happens only in the restricted "quantum equilibrium" regime of Bohmian mechanics, just as "thermal equilibrium" is a restricted regime of classical mechanics.

    Whether Bohmian mechanics works for relativistic quantum theories is still being researched. However, since all present quantum field theories can be thought to have a cut-off, above which they are not relativistic, it can be argued that Bohmian mechanics can in principle also explain quantum field theory.
     
  20. Jan 14, 2014 #19

    DevilsAvocado

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    If I understand you right; you are saying that the option to deterministically in advance predict which slit a single electron will go thru in the double-slit experiment – is still open and very possible in Bohmian mechanics. All it takes is more clever theoretical research and maybe experiments...

    Correct??
     
  21. Jan 14, 2014 #20

    atyy

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    Definitely more experiments, since Bohmian mechanics is basically saying there is some regime of nature in which quantum mechanics fails. In that regime, we could maybe get no randomness in the double slit experiment. Of course, we don't expect quantum mechanics to be falsified for any current double slit experiment, so a better place to look might be the early universe. An example is Colin and Valentini's http://arxiv.org/abs/1306.1579 Phys. Rev. D 88, 103515 (2013).
     
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