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Randomness of quantom particles.

  1. Jan 25, 2010 #1
    I have a question about schrodinger cat experiment. If it really is true that the cat is alive and dead at the same time, then what would happen if we took another box which is closed from the top and has a mixture of carbon, hydrogen, oxygen and other elements needed to create a small goldfish inside it, and asked 7 billion people to believe that if the box is opened, a fish will be inside. Will that actually happen? i know its a bit crazy but i recently watched a documentry from michio kaku and he said that the nature of the universe is such that our thoughts can have some influence on this world. Im sure he doesnt mean that we can change lead to gold just by thinking... but since the quantum world is so random when its unobserved, can the randomness actually transform all the elements in the box into a perfect live fish? since it is just a matter of probability, can this actually happen?
     
  2. jcsd
  3. Jan 25, 2010 #2
    The thought experiment was made up as an attempt to show that such a scenario would be ridiculous (as the cat would be either dead or alive, not both).

    QM can only predict probabilities, and the probabilities even interfere with themselves, but at the macro level one event or the other has actually happened.

    (or something close to that)
     
  4. Jan 25, 2010 #3
    What can happen and what "could/will" happen are two different things. I think in modern physics we calculated the probability of all electron momentum being in sync and rolling a golf ball across the table. I believe on average it took 14 billion years(older than the age of the universe).
     
  5. Jan 25, 2010 #4

    f95toli

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    In principle yes, but that has nothing to do with Schrodingers cat, observations or even quantum mechanics,
    Regardless of how well you shuffle a deck of cards there is always a finite chance that the cards will end up in the correct order (1-ace for all colours); it is just very very unlikely. This is the same thing.

    Now, the probability of ending up with a gold fish is of course astronmically small but it does not change the fact that it is possible.

    (and of course you would need to get the energy to assmeble the elements etc from somewhere else, but lets assume that it is not a closed system)
     
  6. Jan 28, 2010 #5
    Cheers for tha f95. but can u plz clarify how this is not releated to quantum mechanics? I thought it is at the atomic level that lines start to blur between what we think is definate and absolute and what seem to be complete chaos at that level, especially when it is not being observed?

    Or have i misunderstood something?

    Also, was the schrodinger cat thought experiment used for or against the quantum theory? I thought it was to show an aspect of quantum theory, not how wrong it is.
     
  7. Jan 28, 2010 #6
    It's not chaos really, it's just probabilistic. Also, it's not so much when it's 'observed' as to when we try to magnify the effects to the macro level so it CAN be observed. Anyway, what f95 was saying is that the particles by virtue of just bouncing around in the container could create a fish, given proper conditions and not violating conservation of energy.

    I don't know why this would be relevant. There is nothing in QM (or any physics naturally) to allow you to account for 'belief force'.

    No, it was to show how wrong it is. But it doesn't really mean it's 'wrong'... It's just that we only ever see a live or dead cat. So there is a disconnect somewhere... at the limit of quantum mechanics.
     
  8. Jan 28, 2010 #7
    What Michio Kaku said is probably one of the interpretations of quantum mechanics. There are several, and I don't think all of them introduce the human mind into the interpretation. I have not seen the particular show you saw. But he does have a tendency to talk about speculative physics as if it were true. At least when it is string theory. But I haven't seen it, so I don't know.

    This thing about the cat in the box is also subject to the interpretation of QM. In one interpretation it will be in a superposition of alive and dead states. In others, I believe that it will not. The important thing is that you can calculate the probability of finding a dead cat, and it will agree with experiments.

    And I have to correct one of your statements. QM is actually completely deterministic between observations, not random. The randomness only comes in when you make a measurement and the system is in a state which allows several outcomes. The choice of outcome is random, controlled by some probabilities that are defined by the system's wave function).

    Torquil
     
  9. Jan 28, 2010 #8
    Thanks for the clarifications, all of you.
     
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