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B Wave-particle-duality and the evolution of the universe

  1. Jun 8, 2017 #1
    If i've understood correct, every particle in the universe exists in a waveform, which i've understood to mean propability where the particle does exist?

    Then which i've understood is, that the wave transforms into a particle only when observed, is this correct?

    Then if it is correct, how could the universe ever even have began, or evolve into a state where it can produce conscious beings (the observers), if there was (as there assumably wasn't) no observer in the beginning of the universe? Because, wouldn't that mean that the universe only existed as a propability (instead of physical) to the point where the first observer emerged? how could such only potential state of the universe ever evolve into anything, or would that suggest that it evolved into every possible form until the first observer emerged?

    Pardon me if this has been already asked and answered, or if i've just understood something fundamentally wrong.
     
    Last edited: Jun 8, 2017
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  3. Jun 8, 2017 #2

    Drakkith

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    "Observation" should be taken to mean something closer to "interaction". No conscious observers are required.
     
  4. Jun 8, 2017 #3
    what kind of interaction is required as minimum to the particle to transform from wave to actual particle?
     
  5. Jun 8, 2017 #4

    Nugatory

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    There is no transformation from wave to particle; that idea is based on an early understanding of quantum phenomena that was abandoned more than 75 years ago with the development of modern quantum theory. You will still hear people speaking of "particle behavior" when they mean "its position is tightly constrained by the most recent interaction" because the thing that makes a particle a particle is that it has definite position, but that does not mean that it's actually transforming from a wave into a particle. It just means that the wave is becoming more sharply peaked.
     
  6. Jun 8, 2017 #5

    atyy

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    Whether and how one needs to get rid of the fundamental status of the observer in quantum mechanics is unresolved. It is the famous "measurement problem" of quantum mechanics.
     
  7. Jun 8, 2017 #6
    is there a point where the particle can start to be thought as defined, or at it's sharpest peak, should we call it the most probable? and what kind of status does the probability wave have amongst the scientists: do they see the wave as an actual physical phenomenon, or only as a potential, or maybe something in between?

    In double slit-experiement: what kind of interaction with the instrument is required to change the intereferce pattern?
     
    Last edited: Jun 8, 2017
  8. Jun 8, 2017 #7

    jtbell

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    Yes. :biggrin:

    This is the province of interpretations of quantum mechanics. A number of them are currently valid/possible and promoted seriously by various physicists. Unfortunately, since they reduce to the standard textbook mathematics of QM and therefore make the same predictions for measurable outcomes of experiments, there is no way to distinguish them experimentally. Choosing among them is therefore a matter of personal philosophical preference.
     
  9. Jun 11, 2017 #8
    The ultimate thought that i had when i thought of this was, that depending on the type of the required interaction with the wave function to change (or peak) into a particle; if it would require a conscious observer, then wouldn't it lead to following conclusion: in the early state of universe there was no conscious observer, therefore the universe should remain in completely potential state which could not lead into actual physical universe we observe now. Yet the universe is definitely physical now, which must mean that the universe either had an unknown observer in the beginning, or the universe did not begin in the point which we see as it's beginning, but the universe is rather a 4-dimensional block, where the causality we see actually describes the order of the matter in the block, instead of the so called arrow of the time. And since the block is a stagnant object (the dimension of time has no progression, it just exists as a whole) the whole thought of the physical matter evolving into a conscious creatures makes no sense, since it would require the stagnant matter to spontaneously change it's perspective to the block universe, from stagnant 4-dimensional to 3+1. In that case, wouldn't the most logical conclusion to be that the consciousness is as a matter of fact something external from the universe, experiencing the universe like a video game or a movie?

    Block, meaning either a physical block where every possible moment of the universe actually exists, or a potential block, which like a video game, has a potential to take every possible outcome within the presets.

    I wouldn't like to go too philosophical here, but the way i see it the thought of the propability wave is actually very problematic if just the presence of other propability waves isn't enough to peak the wave into a particle.
     
    Last edited: Jun 11, 2017
  10. Jun 12, 2017 #9

    bhobba

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    The involvement of conscious observers is a pretty backwater idea these days - but still legit. It does however lead to issues like you mention - but they can be overcome - however the overcoming of them leads to a very weird view of the world - still you cant disprove it like you cant disprove solipsism.

    We know a lot more about a phenomena called decoherence these days and the easiest way to get out of trouble is simply to say an observation happens whenever decoherence occurs. This follows from the formalism of QM which everyone accepts. If you believe consciousnesses causes collapse all you would have to do is say the result after decoherence isn't known until a conscious observer appears - rather weird - but there is no way of disproving it.

    Thanks
    Bill
     
    Last edited: Jun 12, 2017
  11. Jun 12, 2017 #10

    bhobba

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    You are thinking of the block universe theory which, you may not know, is by forum rules off topic here, so you shouldn't really talk about it.

    Personally I think it's a good rule because for me it's philosophical gobbledygook. But hey - whatever floats your boat and BTW I don't make the rules - take it up with the mods if it worries you.

    At a mathematical level its well known what QM is these days - its whats called a generalized probability model - in fact the next simplest after ordinary probability theory:
    https://arxiv.org/abs/1402.6562

    That's why many arguments about QM are simply rehashes of arguments about what probability means:
    https://arxiv.org/abs/1402.6562

    My view is simple - probability is simply what the Kolmogerov axioms say it is like Euclidean Geometry is what Euclid's axioms says it is. Now applying it - well that's another matter eg in Euclidean geometry a point has no size only position and a line no width. Such do not exist but everyone that applies it has no issues.

    A classic on probability theory was written by a guy called Feller:
    https://www.amazon.com/Introduction-Probability-Theory-Applications-Vol/dp/0471257087

    The first few pages talks a bit about this sort of thing. It would be well worth your while to go to a library and read those pages.

    Thanks
    Bill
     
    Last edited: Jun 14, 2017
  12. Jun 12, 2017 #11
    What kind of experiemental evidence do we have for the decoherenece?
     
    Last edited: Jun 12, 2017
  13. Jun 13, 2017 #12
    But why do you insist on completely eliminating the terms "particle" and "wave-particle duality" just because there are more details in a modern, precise description? Rather than demanding that wave-particle duality is a completely outdated idea (as you've essentially expressed here and in other threads also), why not simply accept that the term "particle" means just as you described... the wave is becoming more sharply peaked? The description and mathematical properties of a wave can change over time... and sometimes a wave becomes sharply peaked... even until in many interactions it acts like a highly localized entity. How is that simple description so completely outdated to eliminate the term wave-particle duality? Just because we do not consider that a hard marble suddenly expands into the likes of a water wave does not mean the term is useless, rather it can be adapted to represent just what you just described in modern terms. Historical terms and descriptions are engrained in science vocabulary and teaching, and it would serve the many students here better if as a "staff: mentor" you would take a more practical attitude toward teaching the next generation rather than demanding that "we are smarter now" and "those old terms are outdated and useless". Not very helpful to the many students that are still taught by a generation who were still present when the original ideas were formulated.
     
  14. Jun 13, 2017 #13

    Drakkith

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    That's exactly what he's done. But in doing so, the wave-particle duality disappears since particles can no longer be described like a classical particle. There's no duality if the "particle" part no longer applies.

    Note that the particle part of the duality is expressed as classical particles. As Einstein said: "It seems as though we must use sometimes the one theory and sometimes the other, while at times we may use either. We are faced with a new kind of difficulty. We have two contradictory pictures of reality; separately neither of them fully explains the phenomena of light, but together they do."

    The advent of quantum field theory and quantum electrodynamics completely removes any description of particles in terms of classical particles. A single theory, that of waves, now fully describes ALL behaviors of particles, thus eliminating the duality. Trying to modify the wave-particle duality to take this new description of particles into account is contradictory, as there is no duality if both descriptions are wave-like descriptions.

    I disagree entirely. Pretending that the duality still exists when, in fact, it doesn't, is exactly what you do not want to do. Students deserve to be taught the correct information, not concepts that have been shoehorned somewhere they don't belong because of nostalgia.
     
  15. Jun 13, 2017 #14
    I finished my undergraduate physics classes less than a decade ago. My graduate QM classes that I finished no longer than 4 years ago were still full of semi-classical derivations and arguments. Even my Quantum Optics textbooks are full of semi-classical descriptions and "heuristics". I highly doubt that a sweeping change has gone through physics since then, jumping from classical mechanics straight to complete QFT. The story of the evolution of QM is still told and the techniques leading up to understanding QM and QFT are still taught with semi-classical mathematics and arguments. I understand what you're trying to say, and were it only for nostalgic reasons it would be silly, but we must still speak to modern pedagogical realities and how students are still learning modern physics. I have no problem with emphasizing modern ideas, but it seems a bit strong to dismiss these ideas immediately and unconditionally. The tone here makes me feel like I've stepped back 60 years where I'll be slapped with ruler if I say "duality". I had similar question about QM when I first learned it, but I have since come to terms with old contradictions, and I did it without the old ideas being unconditionally banned from the vocabulary.
     
  16. Jun 13, 2017 #15

    Drakkith

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    It hasn't been banned. If you want to discuss the history of quantum physics or classical heuristics then talking about the wave-particle duality is perfectly fine. But students (and non-students) need to be told that the duality doesn't actually exist anymore outside of that. The contradiction between the particle and wave models doesn't exist anymore in modern physics and people need to understand that.

    All the heuristics and semi-classical models and methods you learned in school are necessary to transition students between the simpler classical models and the very complex quantum models. But the final results of these quantum models should be told, as they represent the most accurate knowledge of physics at the atomic and subatomic scales. This is even more important for concepts which are especially confusing and widespread, like the wave-particle duality.

    You'll find that we address various misconceptions quite often here at PF. Even if the details of the underlying theory are well above the knowledge level of the person asking the question, we explain that their question involves a misconception and that modern physics has moved past it and it is no longer an issue.
     
  17. Jun 14, 2017 #16

    bhobba

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    It might help you if you look at a bit of the history of the idea:
    https://www.amazon.com/Einstein-Quantum-Quest-Valiant-Swabian/dp/1491531045

    The above details exactly how it came about. But of relevance here is Einstein was shown a copy of De-Broglie's thesis and immediately recognized it was an important step in the solution to the quantum puzzle and highly recommended the paper - De-Broglie's thesis advisers couldn't even understand it which is why they sent it to Einstein for comment. Needless to say with the great mans endorsement he got his PhD, besides the examining committee liked the math. But Einstein knew it was not right - it was simply a stepping stone to its real solution. Someone asked Schrodinger - if its a wave then it should have a wave equation. He found one. But from that point on things moved quickly overthrowing all the old ideas and replacing them with new ones:
    http://www.lajpe.org/may08/09_Carlos_Madrid.pdf

    The final result was Dirac's Transformation Theory published at the end of 1926 which is generally what's called QM today. It showed there was no particles or waves - just quantum stuff.

    Thanks
    Bill
     
    Last edited: Jun 14, 2017
  18. Jun 14, 2017 #17

    bhobba

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  19. Jun 14, 2017 #18

    bhobba

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    With your background a study of an axiomatic treatment will likely help.

    THE textbook IMHO, and many that post here agree, is Ballentine - QM - A Modern Development:
    https://www.amazon.com/Quantum-Mechanics-Modern-Development-2nd/dp/9814578584

    Here QM is developed from 2 axioms - even Schrodinger's equation etc is derived from symmetry, not postulated.

    That symetry is the basis of much of modern physics is one othe great discoveries of 20th centrury physics. If you havent been exposed to it before as a warmup I highly recccomend the follloing in this order:
    https://www.amazon.com/Mechanics-Third-Course-Theoretical-Physics/dp/0750628960
    https://www.amazon.com/Physics-Symmetry-Undergraduate-Lecture-Notes/dp/3319192000

    Thanks
    Bill
     
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