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I Is Schrodingers cat real or just a way to put a lack of data

  1. Dec 20, 2016 #1
    you put a cat in a box with radiation And a poison vile, and the radiation has a 50% chance of killing the cat. Before you open the box and actually measure the results the cat is both dead and alive simultaneously. This is how subatomic particles work, as discovered from the double slit experiment. However "as above, so below" , so wouldn't that mean that this equation should work for all particles regardless of size? And if so wouldn't that mean that facts and data are mearly a paradigm that w'eve created, and the universe is just a creation of us and our mental perception?
     
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  3. Dec 20, 2016 #2
    Wasn't Schrodingers cat originally meant as a sort of comment on the uncertain basis of quantum states rather than meant to be taken literally? After all, the cat is in one state regardless of whether it's been observed. I know absolutely zip about quantum physics so don't think I am trying to answer the question, I'm just saying that I've always thought this example was not meant to be taken seriously.

    In regard to your last question, that seems to be a rather anthropocentric view don't you think? What's in doubt is the state of the observer's brain - it has not aligned with the cat's state. If beliefs or knowledge are represented in the brain as certain physical arrangements, then were we able to examine the observer's brain we should not be able to find an arrangement that represents the true state of the cat. The cat's state is what it is and that is physically sound. The observer's brain's state also is what it is. The problem is that until observation, there is no correspondence between the two states. That is, no representation of the cat's true state can be found in the observer's brain. So in a sense I think what you say is correct - the universe is what it is and that is physically sound, but the state of our brain at any moment may not enjoy a correspondence in representational terms. Thus it is our own physical state that we are talking of, and not necessarily the true state of the universe. Indeed, given that the possible physical arrangements of a finite set of interconnected neurons and glial cells and molecules and so on are all we have to cause representations of the physical state of the universe, perhaps we cannot ever come to a proper correspondence between outer and inner states.
     
  4. Dec 20, 2016 #3

    fresh_42

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    You can find a whole lot of threads of all levels on PF about Schroedinger's cat by using the search option. Here are just two:

    https://www.physicsforums.com/threads/schrodinger-cat-superperposition-vs-sharp-state.877799/
    https://www.physicsforums.com/threa...ation-of-the-schroedinger-cat-duality.883996/

    Your expression "is it real" cannot be answered by physical means. It is philosophical by nature which we won't discuss here. What is left is the question to which extend this thought experiment does explain the mathematical nature of QM. This can go really deep and might even be controversial to some extend, which is the reason I suggested to read what's already been said about it.
     
  5. Dec 20, 2016 #4

    ZapperZ

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    I have no idea what you meant here.

    Schrodinger Cat is an illustration of the principle of superposition that is inherently present in QM formalism. There is no question that superposition occurs - there are way too numerous experimental observations that point to this. In fact, these observations were already well-known in Chemistry even before QM was formulated. It was just that people at that time had no idea how to explain many of these observations.

    So I have no idea what this "creation of us and our mental perception" is. If this is purely philosophy, you might want to say a quick goodbye to this thread before it is closed.

    Zz.
     
  6. Dec 20, 2016 #5
    @ZapperZ obviously this can be seen as controversial, however it was a legitimite question and isnt purely philosophical. I meant if a particle is in superposition until observed, and the wave function is just every possible outcome, then would that make the particle an independent variable unto your perception of it which creates the outcome?
     
  7. Dec 20, 2016 #6

    ZapperZ

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    " then would that make the particle an independent variable unto your perception of it which creates the outcome"

    I have no idea what that means. What is "the particle an independent variable unto your perception" mathematically?

    Please do a search on "realism", especially in the Recent Noteworthy Physics Papers thread in the General Physics forum.

    Zz.
     
  8. Dec 20, 2016 #7
    If you look up the double slit experiment, you'll see that particles are in superposition, meaning that they're literally recorded as potential outcomes until they are observed and recorded. Your perception of the particles literally changes the whole wave function. This is where Schrodinger got the idea of the figurative experiment with the cat. My question though is, why would the cat be any different as it is just a larger number of particles?
     
  9. Dec 20, 2016 #8

    ZapperZ

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    First of all, to be exact, the particle's PATH is in a superposition. To say that "the particles are in superposition" is a mistake because one has to specify the OBSERVABLES that are in such a superposition of states. I can easily cause an observable to be in a definite state, while other observables are still undetermined and still in a superposition.

    Secondly, do a search on Delft/Stony Brook experiments, where they have shown superposition of a huge number of particles (1011)

    It has nothing to do with size. It has everything to do with maintaining coherence in every part of the entity. This isn't easy to maintain spatially and temporally, which is why quantum effects are very difficult to be seen macroscopically.

    Zz.
     
  10. Dec 20, 2016 #9

    Nugatory

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    When Schrodinger proposed his thought experiment, he was not suggesting that the cat would end up "both dead and alive" (which is a somewhat misleading way of describing superposition - you'll find it in pop-sci treatments of quantum mechanics, but not in serious textbooks). He was pointing out a problem in the then-current (~1930) understanding of quantum mechanics: everyone knew perfectly well that the cat would be either dead or alive and not in this weird superposition, but the math didn't seem to predict that outcome.

    This problem was solved over the next few decades with the discovery of decoherence - google for "quantum decoherence" or give David Lindley's book "Where does the weirdness go?" a try. It turns out that the same Schrodinger's equation that leads to superpositions of subatomic particles predicts that larger systems composed of enormous numbers of interacting particles (like a speck of dust, or a bacteriurm, or a cat, ....) will behave classically; this is loosely analogous to the way that the ideal gas law and thermodynamics emerge when you apply Newton's laws to a system made up of a large number of molecules.

    So:
    1) Yes, the equation works for everything regardless of size. However, just as the behavior of a large volume of gas is very different than the behavior of a single gas molecule bouncing around in an otherwise empty box, the end result of applying the equation in different situations can be very different.
    2) It is, obviously, impossible to disprove the proposition that "the universe is just a creation of us and our perception". However, there is nothing in quantum mechanics, Schrodinger's cat, or the double-slit experiment that gives us any reason to accept that proposition either. Based on our current understanding of the math behind quantum mechanics, there's no reason to doubt that the universe was out there and obeying the laws of physics long before there were any conscious beings to imagine it into existence, and it will still be out there long after we're gone.
     
  11. Dec 20, 2016 #10
    I don't understand how that's so confusing. so if the particle is
    Okay, I understand what your saying now. Nonetheless, it is still a really weird finding that i'll have to dive deeper into. Anyways, Thanks for the insight!
     
  12. Dec 20, 2016 #11

    atyy

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    In the orthodox interpretation of quantum mechanics, observers and their observations are real. The wave function, including superposition, is not necessarily real.

    Many consider the orthodox interpretation incomplete, so there are other attempts at interpretation such as Bohmian Mechanics, the Many Worlds Interpretation, and Consistent Histories.
     
  13. Dec 20, 2016 #12
    Yes, this is what I had thought I'd read at some stage. Thanks for expressing it so clearly! I should read some of these references...
     
  14. Dec 20, 2016 #13

    atyy

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    But decoherence does not solve the problem - decoherence does not remove the need for Copenhagen, or some other alternative that may be along the lines of Bohmian Mechanics, Many Worlds or Consistent Histories etc.
     
  15. Dec 20, 2016 #14

    PeterDonis

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    No, that's not what superposition means. Try this by Scott Aaronson (it's a cartoon, yes, but it makes a valid point about QM):

    http://www.smbc-comics.com/comic/the-talk-3
     
  16. Dec 20, 2016 #15

    Nugatory

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    I agree, decoherence does not solve the underlying foundational questions. It does move the discussion of these questions well beyond the starting point of this thread though, and that's progress.
     
  17. Dec 20, 2016 #16
    What about chemistry? Could you please expand a bit about that?
     
  18. Dec 20, 2016 #17
    I thought that the idea of a sentient observer being a requirement to explain QM had long been discarded.
    For me anyway it falls down at the first hurdle, what causes the sentient observer to exist in the first place?
     
  19. Dec 20, 2016 #18

    PeterDonis

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    I think ZapperZ is referring to cases like that of benzene, which showed that the classical "tinker toy" model of how molecules worked was not correct, well before QM came along and explained why. The benzene ring is a six-carbon ring that, according to the "tinker toy" model, should be composed of three double bonds and three single bonds--i.e., the bonds should not all be identical. This should have shown up as, for example, the presence of two different versions of molecules where an atom or group other than hydrogen was substituted for two adjacent hydrogens in the ring: one version where the two different atoms are separated by a single bond, and the other where they are separated by a double bond. However, all experiments showed only one version of such molecules, indicating that all six bonds in the ring were identical and the "tinker toy" model of chemical bonds was not correctly predicting how such structures worked. QM explains this, heuristically, by saying that all six bonds in the benzene ring are in a superposition of being double bonds and single bonds, and that is why they are all identical.
     
  20. Dec 21, 2016 #19
    In quantum computation experiments, it is extremely difficult to keep, say, three particles in superposition of states. Imagine how difficult it would be to keep the approximately 10^30 fundamental particles comprising a cat in a superposition of states. This is a thought experiment. Obviously if you actually conducted this experiment in real life, the cat would be either dead or alive before you opened the box.
     
  21. Dec 21, 2016 #20

    dextercioby

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    The "tinker toy" model mentioned above by Peter Donis was the G.N. Lewis' model of the covalent chemical bond (octet rule). It's still being taught in chemistry classes worldwide. The quantum mechanical modelling of the chemical bond is a really complex subject (two different formulations) which is taught at university level.
     
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