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Perhaps we do see quantum behavior at the macroscopic scale

  1. Jul 14, 2011 #1
    Okay, I will preface this by saying that I have no formal education in physics. I am just a regular man with an active mind and healthy dose of curiosity. There may be some errors in my terminology, but hopefully you'll get what I am saying. Heck, maybe this is already a well known hypothesis.

    Now, as I understand it, by adding together all possible wavelengths of myself, we can find my most probable state. Further, until I am observed, according to quantum theory, I am in a state of superposition. Now, since I am a sentient being, I am continually being observed by myself. This would seem to account for the collapse of the wavefuntion into one, definite, state. Now, here is where my own thinking comes in. I require a certain amount of time to observe my surroundings, process the data, and then consciously become aware of what I have observed, much more time than the instants that Time itself may be divided into. This means that there are MANY iotas of Time in which myself, and, indeed, my entire surrounding environment, go unobserved (considering this, has anything ever, truly, been observed?), even as it and I are acted upon by macroscopic forces. Wouldn't this put me back into a state of superposition?

    The objection that immediately comes to my mind, is that we, collectively, never see macroscopic objects changing states. However, if an object were to change states, it would most likely change to the next most probable state. And I'd wager that we would not notice the change. This is compounded by the fact that we live such pathetically short lives. What are the odds of any member of the human race seeing an object change to say, its' 17th most likely state? It makes a great deal of sense to me, especially when using my own body as an example. Since I observe myself ;and thus cause my wavefuntion to collapse very frequently; the numbers are never allowed to play out very far, keeping the probability of me winding up in a noticeably different state negligible. To be clear, I am saying that we, and everything around us, very likely DO change states, but the changes are so small, we simply do not notice.

    I would appreciate your comments or corrections.
  2. jcsd
  3. Jul 14, 2011 #2


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    Welcome to PhysicsForums, karatepig!

    Actually, your conscious mind does not cause the collapse of every wavefunction represented by your body. As you suggest, perhaps it is more like few or none. Who knows? But either way, you would not be able to experience a superposition of 2 different states of yourself anyway. Think of the Many Worlds Interpretation and you will see why not.

    And also: you never witness something changing from a superposition to a pure state. An observation may "cause" wave function collapse, but you can never objectively be certain that is what happened. You can only deduce this from the setup.
  4. Jul 14, 2011 #3
    Well, if every possible state is accounted for in an alternate universe, then sure, logic tells me I would not experience all the untold number of alternate lives simultaneously. But if alternate universes are not being constantly created (it is just a theory, after all), then I don't see why I wouldn't experience minor changes in my state from time-to-time. Would you mind telling me why you prefer the Many Worlds Interpretation? My main objection to it is that a parallel universe would need:
    1. A process by which all the matter and energy within said universe could be created, and such process must be somehow tied to everything that happens everywhere in the universe.
    2. A place to exist. These Parallel universes would have been multiplying exponentially since at least the formation of THIS universe (assuming this is the "original" universe), meaning an ever-growing number of universes would have to be popping into existence somewhere.
  5. Jul 14, 2011 #4
    Let me say first that I am not a physicist. I find these kind of questions fascinating.

    karatepig wrote...

    "This means that there are MANY iotas of Time in which myself, and, indeed, my entire surrounding environment, go unobserved (considering this, has anything ever, truly, been observed?), even as it and I are acted upon by macroscopic forces. Wouldn't this put me back into a state of superposition?"

    I like your question very much. In my opinion nothing has ever, truly, been observed AS IT IS RIGHT NOW.

    The speed of light is finite, objects are separated by distance no matter how small, therefore information must take some time to reach you so we are always observing THE PAST.

    Sometimes the past can be billions of years, sometimes the past can be atto-seconds. Depends on what kind of 'instrument' you use to make the observation.

    I think you are aware of this time lag, however the observation is 'continuous' (even though it may be an observation about the past) If the object is changing states shouldn't we see that change?

    UNLESS the observation is not continuous, then in my opinion anything can happen (within reason)

    I have no opinion at this time about superposition. Let someone more qualified adress that :smile:
  6. Jul 14, 2011 #5
    Welcom, karatepig.

    From the perspective of most interpretations of quantum mechanics, an observer doesn't need to be conscious. An observer could just as easily be a photon. Recently, a theory called quantum Darwinism was preliminarily experimentally verified. It essentially says that the uniform macroscopic world emerges from a Darwinian process of particles observing each other until only one reality remains.

    The many-worlds interpretation of quantum mechanics doesn't actually postulate multiple universes in the cosmological sense. It simply suggests that the wavefunction never really collapses when a measurement is made, and that we instead only observe one part of that un-collapsed wavefunction.

    Your quantum state is changing all the time, and modern science doesn't dispute that. But it doesn't do quantum mechanical things like end up in two places at once because its particles are constantly "observing" each other. Only if you isolated each individual particle in your body from every other one could it start to behave like a quantum object. If that were to happen, however, you wouldn't be conscious.
  7. Jul 14, 2011 #6


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    To be clear, consciousness is not required for an "observation". Observation really means interaction. When two particles interact, they collapse each others' wave functions.

    From there, it's pretty simple to see. Get a trillion atoms together and the collective macroscopic object behaves macroscopically, with no superposition of states.
  8. Jul 14, 2011 #7
    Good job saying what I said in way fewer words.
  9. Jul 14, 2011 #8


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    You da man. I just the also-ran (who didn't read the backlog before posting).
  10. Jul 14, 2011 #9
    That all makes perfect sense (the interaction thing actually rings a bell. I am going off of dusty memories from a book here). I'll have to look up the details of the Quantum Darwinism experiments.
    From Cjames "The many-worlds interpretation of quantum mechanics doesn't actually postulate multiple universes in the cosmological sense. It simply suggests that the wavefunction never really collapses when a measurement is made, and that we instead only observe one part of that un-collapsed wavefunction"

    You just derailed the storylines of many a sci-fi show....
  11. Jul 15, 2011 #10
    Well, no, not really. For the 'collapse' to happen, the interaction should be macroscopic, i.e. involve gazillion of other particles. The two particles may entangle their wavefunctions though, in which case macroscopic interaction of one particle will collapse the wavefunction for both of them. But the gazillion has to be involved somewhere somehow.
  12. Jul 15, 2011 #11
    If it makes you feel any better, multiple cosmological universes might still exist. It's just that they don't have anything to do with the many-worlds interpretation of quantum mechanics. These two ideas have been conflated in popular science.
  13. Jul 15, 2011 #12
    Question:In your opinion does the 'collapse' have anything to do with consciousness?
  14. Jul 15, 2011 #13
    But if you take the wave function of the two-particle system, then this wave function won't collapse.

    In the Copenhagen interpretation, which is the only one where wave function collapse occurs, you just have to arbitrarily divide the world into the "classical" measurement apparatus and the quantum system being measured. Von Neumann proved, in his famous quantum mechanics "Bible", that where you place the dividing line is physically meaningless: regardless of which particles are considered part of the measuring device and which particles are part of the system, you'll get the same experimental result.
  15. Jul 15, 2011 #14


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    Right. However, the OP is talking about observing himself. To his own observation, all his wavefunctions are collapsed, and he is not superposed.
  16. Jul 15, 2011 #15
    IMHO no, 'collapse' (or rather 'apparent collapse' or 'collapse for all practical purposes') has nothing to do with consciousness, as I understand it (and I do not pretend that I do) it's just a statistically most probable thing to happen, one of those thermodynamic things like gas filling the entire volume or heat flowing from hot to cold.
  17. Jul 15, 2011 #16
    This is why I really like the theory of quantum Darwinism, because it isn't arbitrary. It postulates that a special quantum state, called a pointer state, evolves. Pointer states are quantum mechanical in nature, but they are resistant to the effects of entanglement and superposition, so they appear classical.
  18. Jul 15, 2011 #17

    What do you mean by 'particles' that are not yet collapsed? What are they and how do they interact?
  19. Jul 15, 2011 #18


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    Particles are described as wavefunctions. When a particle is not being interacted with, its wave function begins to spread out. (eg. photons, electrons and larger particles in a two-slit experiment. They follow all possible paths from source to destination, including through both slits). If the particle interacts with its environment (such as a detector), its wave function collapses, and its path from source to destination becomes fixed (i.e. it is observed to pass through exactly one of the slits).
  20. Jul 15, 2011 #19

    Where did the 'particle' come from? You were speaking of a spreadout wavefunction and suddenly you introduced the notion of 'particle' without an explanation(a spread out wavefunction is potentially interacting with the whole environemnt at all times)? I know it's a grey area, my questions are only meant to show the impossibilty of a coherent classical explanation.
  21. Jul 15, 2011 #20


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    We were always talking about particles. That's what the OP is made of.
  22. Jul 15, 2011 #21

    I read that, but 'particles' is a term used by non-professionals(and you are a professional AFAICS).

    Saying 2 uncollapsed 'particles' interact and cause the collapse of their respective wavefunctions is misleading and confusing. AFAIK, decoherence is still a murky area that no one understands in detail, hence your strong statement "When two particles interact, they collapse each others' wave functions" sounds either wrong/incomplete or simply unwarranted at this time
  23. Jul 15, 2011 #22


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    Agreed, but I am trying to phrase the answer within the context of the OP's scenario.

    I probably should have prefaced with the part about the particles being wave functions that get smeared out.
  24. Jul 15, 2011 #23
    A very common phenomenon is not compatible with any kind of corpuscularist model or representation or semantics : the electrical contacts, like in relays and switches.
    It works only because conduction electrons are waves, whose wavelength is larger than the interatomic distances in the metal, mainly copper or more noble metals. Conduction electrons travel and bump on phonons or other crystalline defects at Fermi speed, for Fermi energy level. They are much more wide and long than crystalline cells. So they can jump over the major defect a contact is (with fine oxydization, grease, adsorbed gases, so on). It may be called a tunnel effect if you like.

    One may argue whether this tunnel effect is quantic or not. It is solid state physics, and it remains undulatory.
    Last edited: Jul 15, 2011
  25. Jul 15, 2011 #24


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    This sounds like standard electron tunneling, as seen in semiconductors. The electrons, particles though they may be, have a probability cloud that is larger than the gap, meaning that the electron has a non-zero probability of being on the oppisite side of the gap.
  26. Jul 15, 2011 #25
    An atom is 99.999% empty space so an electron does not have to tunnel through anything because there is nothing there.

    Using the word 'tunneling' implies that there is some kind of physical barrier that an electron overcomes, (not by going through it) by the 'magic' of statistics, probabilities.

    This is nonsense and embarrassing.:smile:
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