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How did someone came up with the idea that , an outcome doesn't exist until we r .

  1. Jul 3, 2012 #1
    How did someone came up with the idea that , an outcome doesn't exist until we r.....

    How did someone came up with the idea that , an outcome doesn't exist until we really observer it?
    How did that person say it?how did he really know that the cat(Schrodinger's cat thought experiment), is neither dead or alive(superposition) until we observe it? any proof? this doesn't make any sense??
     
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  3. Jul 3, 2012 #2

    Simon Bridge

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    Re: How did someone came up with the idea that , an outcome doesn't exist until we r.

    Nobody has. The idea is that a quantum system prepared in a superposition state remains in that state until an attempt is made to measure a specific state. The nature of the measurement event is subject to some debate but it is usually taken to be some interaction that requires a specific state.

    The fact that Schrodinger's Cat does not make sense in this description is the whole point. It illustrates a problem with the Copenhagen interpretation of quantum mechanics. Arguments continue. Treat it as a koan.

    Bear in mind that the cat is not a quantum system ... so do you understand why someone would think it would be legitimate to describe it if it were one?
     
  4. Jul 3, 2012 #3
    Re: How did someone came up with the idea that , an outcome doesn't exist until we r.

    is the cat analogy just an example to demonstrate what is going in the quantum world, or the cat is actually neither dead or alive until we really observe? or is that how a particle would behave?
     
  5. Jul 3, 2012 #4

    Simon Bridge

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    Re: How did someone came up with the idea that , an outcome doesn't exist until we r.

    You know about cats right? What do you think? Is the cat actually in a superposition of alive and dead?

    A particle, however, will be described by an undetermined state unless something happens to determine that state. The act of observing a thing influences the thing.
     
  6. Jul 3, 2012 #5
    Re: How did someone came up with the idea that , an outcome doesn't exist until we r.

    the cat is/was never in a super-position (of dead-alive). the super-position is at only at the microscopic level (during radioactive decay in this case) and is fragile and breaks down at some point well before engulfing the cat.

    the superposition does not extend well beyond the particle, it "collapses" (i'd rather use the word gets modified/entangled to something else) as it interacts with any/many of the various elements/components of the external environment
     
    Last edited: Jul 3, 2012
  7. Jul 3, 2012 #6
    Re: How did someone came up with the idea that , an outcome doesn't exist until we r.

    Let's assume ,particles (that cat is made out of) doesn't interact with any things at all. If so,could the cat be in superposition?
     
  8. Jul 3, 2012 #7
    Re: How did someone came up with the idea that , an outcome doesn't exist until we r.



    Yes, but the biggest object that has been successfully put into superposition is 400-atom molecule. Superpositions are real, not hypothetical
     
  9. Jul 3, 2012 #8
    Re: How did someone came up with the idea that , an outcome doesn't exist until we r.

    really? how can we say exactly? :O proof?

    thanks
     
  10. Jul 3, 2012 #9
    Re: How did someone came up with the idea that , an outcome doesn't exist until we r.

    does this mean that particles are aware that we are looking at us? alive or something? lol
     
  11. Jul 3, 2012 #10

    Demystifier

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    Re: How did someone came up with the idea that , an outcome doesn't exist until we r.

    Actually, there is some kind of a proof. If one assumes that nature is local, then Bell theorem can be viewed as a proof that outcome does not exist until it is observed.

    Conversely, if one assumes that outcomes exist even without observation, then Bell theorem can be viewed as a proof that nature is nonlocal.

    See also
    http://www.iafe.uba.ar/e2e/phys230/history/moon.pdf [Broken]
     
    Last edited by a moderator: May 6, 2017
  12. Jul 3, 2012 #11
    Re: How did someone came up with the idea that , an outcome doesn't exist until we r.

    let's say we flip a coin with our eyes closed. it falls on the ground and I do not know if it is head or tail until I open my eyes to see it actually. Does this superposition theory mean, the coin that 'fell to the ground' is neither head or tail unless I open my eyes and really observe it?

    It is Flat too. but side is not determined unless I really observe it???but if it is on the ground,it HAS to be either head or tail,right?
     
  13. Jul 3, 2012 #12

    ZapperZ

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    Re: How did someone came up with the idea that , an outcome doesn't exist until we r.

    Look up quantum interference on buckyballs, for example. Furthermore, the often-referenced Delft/Stony Brook SQUID experiments shows that 10^11 particles can be in a quantum superposition of states.

    When you "look" at something, you have something that interacts with it. Think about that a little bit more. Thus, such interaction, at the quantum level, affects that system.

    Zz.
     
  14. Jul 3, 2012 #13
    Re: How did someone came up with the idea that , an outcome doesn't exist until we r.

    we we usually look at something, light waves(electrons(?) ) interacts with the object then they comes back to the eye or something similar. When we 'look' at the particle, what do you think happens? hmm..?
     
  15. Jul 3, 2012 #14

    Simon Bridge

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    Re: How did someone came up with the idea that , an outcome doesn't exist until we r.

    It is possible, in principle, for large objects to be prepared in a superposition of some sorts of states. However - arguments like that sort-of miss the point Schrodinger's Cat is trying to make. The thought-experiment is often misrepresented in popular media which does not help.

    I used to think of it as the cat did the measurement, rendering it dead or alive. These are classical rather than quantum mechanical states after all. Before opening the box, therefore, we have a classical probability distribution. We don't know if the cat is dead or alive until looking but looking does not kill (or save) the cat, nor does the time evolution of the cat's life-state involve wavelike properties.

    In general - classical probability describes the researcher's state of knowledge of a classical system - quantum probability describes the Universes state of knowledge of the quantum system.

    I say I used to think like that ;) I still think it is a useful stepping-stone.

    This is not correct - it is possible to prepare a particle in a superposition of the first two energy eigenfunctions of the infinite square well ... the size of the well can be any size you like, say, the length of the lab. I'm sure you'll agree that a wavefunction spanning many meters extends well outside the particle - however you want to define the size of the particle.

    The concept of a "collapse" has issues too and should be taken with caution. Like, above, I described the collapse of a quantum system leading to a change in classical state of the cat. Or did the wave-function collapse when the cat died/failed-to-die? Or was it when I looked? Perhaps I got someone else to look, and they tell me ... did the collapse happen when they looked or when they told me what they saw? Maybe it collapsed for them and not for me until they tell me? But what if they can't get hold of me and just leave a message on my voicemail? Does leaving the message collapse the wavefunction or does my accessing voicemail collapse it? What if I forget to check voicemail or there is a fault and my supplier deletes the voicemail? Does that make the collapse un-happen?

    The point of the whole set of questions is that this way of thinking about the system is nonsense. However - we still have to use this quantum mechanics stuff. Just beware of attempts to simplify the situation for some idea of a layman.
     
    Last edited: Jul 3, 2012
  16. Jul 3, 2012 #15

    ZapperZ

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    Re: How did someone came up with the idea that , an outcome doesn't exist until we r.

    I'm not sure what you're asking here, considering that you already know that light or other entitles interacts with the object. So what's the problem?

    Here's evidence that even with just ONE interaction, it can destroy the original state of the system and causes the new system to be a coupled system with the "interactor".

    https://www.physicsforums.com/showpost.php?p=1498616&postcount=55

    Zz.
     
  17. Jul 3, 2012 #16
    Re: How did someone came up with the idea that , an outcome doesn't exist until we r.

    I will check it sometimes. So Simon Bridge,are you telling that thinking according this is kind of stupid and we better not ?
     
  18. Jul 3, 2012 #17

    Simon Bridge

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    Re: How did someone came up with the idea that , an outcome doesn't exist until we r.

    I think silvercat is thinking that "looking at the cat" means "some photons hit your eye" ... eg. the act of observation occurs when the photons hit your eye, and, in the Copenhagen interpretation, the act of observation collapses the wavefunction ...

    ... which is the kind of thinking Schrodinger was trying to highlight.

    Does the observation occur then though? Or is it when the light triggers electro-chemical signals in the optic nerve? Or when the brain enters that state which says "Ugh: the cat is still alive! WTF?!"

    ... this type of thinking tends not to be all that productive. Open box, cat is dead, looking at the cat did not kill it. Hang on to that. I don't think it is "stupid" as such - the paradox is a useful koan. What all this means is we have to be very careful about what we assume is going on when we do the math in quantum mechanics. We have to be very careful about what we say is happening. Watch Feynman, or others, talk about quantum experiments - a particle leaves a source and arrives at a detector and we can say nothing, in detail, about how it got from one to the other :)

    It may be an interesting exercize to figure out some similar experiment that does not require a cat maybe dying. You need some quality of a clearly non-quantum system which can be state A or state B, then rig things so the statistics of the states is linked to some quantum statistics displaying interference... this is why the cat's state can be represented as a superposition like that.
     
    Last edited: Jul 3, 2012
  19. Jul 3, 2012 #18
    Re: How did someone came up with the idea that , an outcome doesn't exist until we r.

    the problem is this. when we observe a mobile phone, light wave(or light particles/electrons?idk ) hit the phone and they return to the eye then we see the mobile phone.

    When we observe a particles that is ins superposition,does the same thing with the mobile phone happen?

    and to change its superposition,how does the particle detect that we are observing it somehow? got it?
     
  20. Jul 3, 2012 #19
    Re: How did someone came up with the idea that , an outcome doesn't exist until we r.

    re posting this because this one's answer will help me to get this point exactly (hoping).

    let's say we flip a coin with our eyes closed. it falls on the ground and I do not know if it is head or tail until I open my eyes to see it actually. Does this superposition theory mean, the coin that 'fell to the ground' is neither head or tail unless I open my eyes and really observe it?

    It is Flat too. but side is not determined unless I really observe it???but if it is on the ground,it HAS to be either head or tail,right?
     
  21. Jul 3, 2012 #20
    Re: How did someone came up with the idea that , an outcome doesn't exist until we r.

    wola!! That is another thing to think.yeah that is almost what I meant. same question arises .
     
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