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Randomness and the life cycle of events of our Universe

  1. Jul 17, 2013 #1
    This is a very important question for me which has bothered me greatly. I started talking about it in the Smolin cosmic natural selection thread.

    What I would like to know is, if the Universe started over a very large number of times (n) from t=0, the start of the big bang, In how many of these Universes would I be sat here typing this question?

    Possible answers are: 1/n, n, 0 !
    What are the reasons and what is the certainty in the theory behind these reasons?

    I have always thought perhaps instinctively that the answer is 1/n because of the apparent randomness from quantum particle interactions right up to the scale of Galactic mergers. Even a hurricane cannot be predicted due to chaos and random behaviour. However I have been told this is wrong and I would like to understand fundermentally why I was wrong. I believe that this is an extremely important question and central to our understanding of our Universe.
     
    Last edited: Jul 17, 2013
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  3. Jul 17, 2013 #2

    bapowell

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    There are many details about the origin of life -- abiogenesis -- that would need to be ironed out before your question could be answered with sufficient certainty. Even after life gets started somewhere in the universe, it needs to evolve to intelligent beings (so that you can sit here and type). While evolution tends to increase the amount of information in the genome, the development of more complex/intelligent beings is by no means inevitable. One must consider the role of contingencies in the establishment of complex life (how inevitable was it that life crawled out of the oceans? If there was no Cretaceous-Paleogene extinction event, would humans ever have evolved?) It seems to me that the development of intelligent life is contingent upon many such critical events.

    Lastly, we would need to stretch our imaginations in order to consider all the different forms that intelligent life might take (must it be carbon based? what kinds of habitat are necessary? could intelligent life live on a star?) Maybe some of these ideas are far out, but it's important to resist the assumption that intelligent life must in some sense be like us.

    Only then can we start discussing the places in the universe where intelligent life might emerge, and only then can we even begin to assign probabilities to this process.
     
  4. Jul 17, 2013 #3
    bapowell, thanks for reply. I wasnt looking at this from an evolution of life perspective. Perhaps we can change the question to would the Sun and earth even exist. My view is that even our own milky way galaxy would not exist more than 1/n times. However, others have said that the exact same events would unfold each time, right down to quantum particle interactions, meaning that the exact same Universe happens every single time, so I just have to think that I have misunderstood something very basic about our Universe.
     
    Last edited: Jul 17, 2013
  5. Jul 17, 2013 #4

    bapowell

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    So you are essentially asking how many solar systems are there with a star like the Sun and a planet like the Earth?
     
  6. Jul 17, 2013 #5
    Does the Universe repeat in such a way that every particle, feature and detail of our universe happens the exact same way over and over, each time the BB is replayed?


    One of the implications for the answer being 1/n could also be that the Universe was not created deliberately and intentionally to be a certain way eg. with me being around, not that that was my reason for asking..
     
    Last edited: Jul 17, 2013
  7. Jul 17, 2013 #6

    bapowell

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    I suppose we would need to have a better understanding of the physics governing these many "starts" of the universe. For example, if the process is ergodic than the question of how likely Earth is in subsequent universes (over time) could be answered by studying how likely Earth is in this universe (over space).
     
  8. Jul 17, 2013 #7
    Again, I am not really concerned about the possiblity of a second earth elsewhere simply due to the virtually infinite size of the Universe, or perhaps the virtually infinite time the Universe might exist for. I just want to know if the EXACT same events unfold in the exact same way, each time the BB replays, so that for example, I can sit here and type this each time?

    I suspect that there are alot of important philosophical implcations depending on the correct answer to this question.
     
    Last edited: Jul 17, 2013
  9. Jul 17, 2013 #8

    bapowell

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    And as I've said, you'd have to me much more explicit about the physics of the BB process in order to answer that question.
     
  10. Jul 17, 2013 #9
    Well I dont know all of the BB Physics for sure, but if we assume that the BB Physics is identical each time would the exact same Universe repeat in detail each time?

    My view is that even if the first 1 second of the BB was somehow made to repeat in an identical way every time, so that every single particle existed with the same energy and position, the Universe would still diverge into a whole range of different structures to ours (although similar) just due to random quantum variation.
     
    Last edited: Jul 17, 2013
  11. Jul 17, 2013 #10

    bapowell

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    So you are essentially asking how deterministic the physics governing the evolution of the universe is. Good question. Of course, classically, you would expect that the exact same initial conditions would spawn the exact same universe each time. But then there are those pesky quantum effects....
     
  12. Jul 17, 2013 #11
    Yes it is a question about determinism, a very good word for it. You have confirmed my thoughts but Chalnoth takes a different view and we usually agree so I started to doubt well, just about everything I thought I knew.
     
  13. Jul 18, 2013 #12
    I have found a reference to determinism in Physics:

    http://en.wikipedia.org/wiki/Determinism


    Based on this it seems that the Universe is not deterministic.
    Unfortunately I am still not entirely clear. Is it something that we do not know for sure?


    If so, the conclusion is that I was not intelligently created or planned, I was a statistical accident..


    It still seems to be "hotly contested". See table at bottom where there is a column for deterministic?

    http://en.wikipedia.org/wiki/Interpretation_of_quantum_mechanics
     
    Last edited: Jul 18, 2013
  14. Jul 19, 2013 #13
    And non-linear effects too such as the butterfly effect. It makes things so much simpler too to have it that way: it starts with a definite initial condition and through random fluctuations and non-linear effects, evolves in time to a particular form likely different from other forms it could take even if the initial conditions were infinitesimally similiar.
     
  15. Jul 19, 2013 #14

    bapowell

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    Right, but this is still a fully deterministic system. Chaos imparts a limitation on our ability to predict the future trajectory of the system, but the equations of motion are nonetheless deterministic.
     
  16. Jul 19, 2013 #15

    bapowell

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    A classical system is in principle fully deterministic. This was initially realized and promulgated by Laplace: if you have the equations of motion and you know the initial conditions of every particle with infinite precision, then you can predict the state of any particle at any future time. However, we live in a quantum world, and we know quantum mechanics is governed by laws that are inherently probabilistic. This changes things (c.f. the table you reference on the wikipedia page)

    I'm not sure it says that -- whether the universe is deterministic or not, it is entirely unclear what its origin was. Fully deterministic worlds are deeply intriguing -- they essentially imply that intelligent agents have no free will -- everything we've done and will plan to do are forced on us by the initial conditions of the universe and the consistency of the laws of physics. Obvious philosophical implications abound. But the question of intelligent design or some other teleogical origin of life is really a different question (i.e. you could still be a statistical accident even in a deterministic world.)

    I'm confused about why many-worlds is considered deterministic -- maybe someone can jump in here and explain? Sure, if I know the quantum state at some initial time, then many-worlds gives me the unitary evolution of the quantum state into the future in a fully deterministic way. But, the quantum state evolves into multiple branches (the superposition of possible states corresponding to different observational outcomes of the state variables). Sitting here in our universe, we have no way of predicting which of these branches we will at any given time evolve along -- this is the same uncertainty inherent in the collapse of the wave function in the Copenhagan interpretation.
     
  17. Jul 19, 2013 #16
    Thanks for replies. I think we all agree that there is a random quantum component that makes each repeat of our Universe different.

    I think I had always accepted that the Universe is non - deterministic as a result of what I had learned about QM, but I think I had also clung to the hope that it was in some way deterministic. There are obviously alot of Philosophical implications to one or the other.

    bapowell said, "But the question of intelligent design or some other teleogical origin of life is really a different question (i.e. you could still be a statistical accident even in a deterministic world.)"
    I will have to have a good think about this.


    I also would like to see what others have to say about this, because I have read somewhere that no one truly understands QM :)


    bapowell, I was also not entirely sure myself whether macroscopic Chaotic systems can also be fully deterministic. I did find this ref:

    http://en.wikipedia.org/wiki/Chaotic_system

    Chaos: When the present determines the future, but the approximate present does not approximately determine the future.
     
    Last edited: Jul 19, 2013
  18. Jul 19, 2013 #17

    bapowell

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    Indeed. If we can work to infinite precision, then chaos presents no limit to our predictive power. It's when practical limitations force us to make approximations that chaos renders our predictions useless. But there's no inherent randomness here -- it's all a result of a tremendous sensitivity to the precise value of the initial conditions of the system.
     
  19. Jul 19, 2013 #18

    bapowell

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    OK, I need to qualify this. Of course, even statistical fluctuations are fully determined in a classical world (the randomness associated with the fluctuation is due only to our ignorance of the positions and velocities of all the particles in the ensemble). What I'm getting at in that statement is that even if the world is deterministic, it doesn't imply that some supreme agent had any role in planning it, or in setting up the initial conditions in any specified way. Even if the laws of physics are fully deterministic, in an experiment where we create many universes with randomly drawn initial data, we'll of course find that they all evolve differently (some have a Tanelorn, some don't).
     
  20. Jul 19, 2013 #19
    Some background here, I started this thread after a discussion with Chalnoth regarding a possible description of the nature of time. I suggested that only the present planck time moment ever exists and that this is always used to calculate particle positions and energies in the next planck moment, perhaps like a 3D video game. The previous planck times or iterations no longer exist, unless they are stored in some way, so time travel to some previous point is not possible because that point no longer exists. Their wave functions have collapsed etc.

    http://en.wikipedia.org/wiki/Planck_time


    However, Chalnoth suggested that every point in time for the Universe could always be calculated even from the very initial conditions of the BB. This would mean that the Universe would have to be highly deterministic, but I had always thought it was the complete opposite due to QM and maybe other reasons.


    The philosophical implications regarding determinism or not, had never occured to me at all before now. I agree that just because a Universe is deterministic doesnt imply that it was all planned, designed or intended to be the way it is, but for sure a non determinstic Universe has no possibility of an intended plan because there is no possibility to know or control how it all unfolds, each BB apparently produces a different Universe although they could be very similar, even if every single particle and physical law starts out the same each time.

    It still appears to me this is a non deterministic Universe unless anyone has anything to add. However Tanelorn will always turn up there at some point :)
     
    Last edited: Jul 19, 2013
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