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I A thought about parallel universe

  1. Jul 1, 2016 #1
    I thought of something interesting just today.
    Let's say I have a decision to make, left and right, that will lead to different future. The idea is, there is a universe where I choose left which have different future than if I choose right, in that sense I have no problem.
    However, in order for me to choose let's say 'right', there needs to be certain pulses and chemical in my brain that makes me decide 'right'. In order for me to think 'left', there has to be something different in the past that triggers it, could be something like a piece of dust a supernova, that causes me to think differently or have different timing that could leads to it. And even that difference cannot happen unless there is something else different, and that keeps going indefinitely.
    Even when I use a computer to 'randomize' the outcome, I will still press the button at some exact time and the way the electricity goes inside the computer, if it says 'right', no matter how many times you rewind that event, the outcome will always be 'right'. Unless I press it very slightly differently or if the voltage changes ever so slightly that will change the outcome, which again require something else to happen.
    There has to be something different in the past that leads to a different outcome, otherwise the outcome will be exactly the same, every single time.
    In this case, parallel universe simply cannot happen since the past is like a 'closed system', unless probably if time travel possible, but that's another story.
    Is there a problem with this thinking?
  2. jcsd
  3. Jul 1, 2016 #2


    Staff: Mentor

    The many worlds interpretation that you reference is a quantum mechanical concept, not a classical concept. I noticed that you posted it in general physics, but I think that you need to decide what framework you would like for your answers.

    If you are ambivalent then I would recommend QM since all we can say about it classically is that the question doesn't arise.
  4. Jul 1, 2016 #3
    I also wanted to add that a "choice" in the many-worlds interpretation is (usually) not the choice of a human
    To take that for granted you would have to assume that you are actually able to decide for the thing that you did not decide on in this universe.
    If you just think of a human as a "biological machine" then we are highly determined and not actually able to decide much differently in another universe than we do here. (If we started out in the same initial conditions)

    A "choice" would more correctly be the "choice" whether a photon will be absorbed or not or something like that.
    Basically, any quantum mechanical process in which the wave function of a particle collapses.(All just as far as I know)
    I am pretty much as far away from beeing an expert on this as you can be.
  5. Jul 1, 2016 #4
    Well my background isn't physics which is the reason why I posted it in general physics, so I apologize if I didn't post it in the correct board. I'm actually studying computer science but got interested in physics and engineering as well.
    Anyway, I still think there is no way that two choices, when repeated in the same way in the exact same time can lead to different result, even when you're not talking about 'human choices', unless there is something from outside the timeline affecting it like a time traveler. I know that in order for both choices to work, we have to assume that it is possible to have different outcome from exactly the same initial condition, but that doesn't seem possible in the first place, which is why I'm wondering.
    Last edited: Jul 1, 2016
  6. Jul 1, 2016 #5


    Staff: Mentor

    No problem. I moved it to the quantum forum.
  7. Jul 1, 2016 #6
    Ok the main thought behind this is that some things in quantum mechanics really seem/are random.
    Not like "no idea what will happen"-random but more like "i can tell you the probability but not whether or not it will happen"-random.
    So even though NOTHING absolutely nothing is diffenent between two experiments they can still have different outcomes.
    So there is no need for a difference in your past for there to be some randomness in your behavior.

    The many-worlds interpretation tries to resolve the problem of this randomness by saying "everything happens" but in different universes.
    So in the example i made there are a few universes in which the photon is absorbed and a few in which the photon is not absorbed.

    Humans might be chaotic. A tiny variation of something might have incredibly big long term effects.
    So a miniscule difference in some chemical process could possibly make you act slightly different under the right circumstances.

    Personally I don't think that is very plausible but that is up to you to decide.
    I think a miniscule difference in some chemical process will likely have almost no effect at all ....
  8. Jul 1, 2016 #7
    And you could always toss a coin!
  9. Jul 1, 2016 #8
    Let's say you have a handful of some radioactive material. That means the atoms are changing (decaying) by emitting some particle and changing from element A to element B. Your handful starts out as something like 10^23 atoms of "A" and if you watch, at that element's half-life later, there will only be 0.5 x 10^23 atoms of "A." Now why did any particular one of those atoms decay at its particular time? According to your OP scenario, there must be some difference between all of these atoms, with that difference manifested in the particular time each "chooses" to decay.

    This is not the prevailing view. There is no "hidden variable" controlling the particular decay time of each atom. As far as we know, all these atoms are identical. All we can say is, there is a certain probability that any one of the atoms will decay in the next hour or whatever time.

    It sure looks like what we are talking about when we say "random" is something happening, without a cause. No "reason" to decay now rather than yesterday or 10 years from now. Weird, right? You wouldn't be the first person to think that is just not sensible. But there it is.
  10. Jul 2, 2016 #9


    Staff: Mentor

    Many Worlds (MW) is a deterministic theory. Probabilities enter into it because since you don't know a-priori which world you will be in all you can do is assign a probability.

  11. Jul 2, 2016 #10


    Staff: Mentor

    QM is silent on that. It doesn't give a reason. It doesn't mean there isn't one - there may be. Its just the theory doesn't say.

    It maybe nature is just like that - we don't know.

    There is no a-priori reason anything needs a cause.

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