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Thread: Cyclic Universe..

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    Cyclic Universe..

    I was just wondering what peoples thoughts were on the plausibility of this model for a cyclic universe ?

    Is is possible that we live in an eternal universe that goes through never ending cycles ?


    Far away is close at hand in images of elsewhere...

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    Quote Originally Posted by kevin1981 View Post
    I was just wondering what peoples thoughts were on the plausibility of this model for a cyclic universe ?

    Is is possible that we live in an eternal universe that goes through never ending cycles ?
    Well.... cool graphics. :^) I think the model suffers from the same problem that the "standard" cyclic universe suffers from, i.e., as matter/energy eventually falls back into a very hot and dense state, it does not duplicate the conditions of the early inflationary big bang.

    But even if it did, what evidence is there supporting this model, and how would you ever find such evidence that supported it?
    Everyone is entitled to his own opinion, but not his own facts.

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    Quote Originally Posted by Cougar View Post
    Well.... cool graphics. :^) I think the model suffers from the same problem that the "standard" cyclic universe suffers from, i.e., as matter/energy eventually falls back into a very hot and dense state, it does not duplicate the conditions of the early inflationary big bang.
    How do you know it does not duplicate the conditions of the early inflationary big bang ?

    How do you know other cyclic models do not duplicate the conditions of the early inflationary big bang ?

    Quote Originally Posted by Cougar View Post
    Well.... cool graphics
    Yeah i thought so too, i really like neon colours !
    Far away is close at hand in images of elsewhere...

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    Quote Originally Posted by kevin1981 View Post
    How do you know it does not duplicate the conditions of the early inflationary big bang ?

    How do you know other cyclic models do not duplicate the conditions of the early inflationary big bang ?
    Well, off the top of my head, the nature of energy and matter within the Universe has and will continue to change since the earliest stages. A lot of it has changed from potential to motion and radiant heat. Some fused matter has become heavy elements. A lot more neutrons. A lot more black holes.
    "I'm planning to live forever. So far, that's working perfectly." Steven Wright

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    Quote Originally Posted by Noclevername View Post
    Well, off the top of my head, the nature of energy and matter within the Universe has and will continue to change since the earliest stages. A lot of it has changed from potential to motion and radiant heat. Some fused matter has become heavy elements. A lot more neutrons. A lot more black holes.
    I see, yes, that all makes a lot of sense.

    So are there big problems with getting a cyclic universe to reset back to the very first initial conditions that we have observed with our current
    model of understanding ?
    Far away is close at hand in images of elsewhere...

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    It's hard for me to see the 2nd law (entropy) overcome even in a collapse.
    We know time flies, we just can't see its wings.

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    It seems like this is very big on fancy graphics showing their model, and very small on supporting evidence for that model.
    Conserve energy. Commute with the Hamiltonian.

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    Quote Originally Posted by Grey View Post
    It seems like this is very big on fancy graphics showing their model, and very small on supporting evidence for that model.
    Yes, I was having a discussion with someone and he sent me this video saying that it was intuitive to him and he thinks that it
    makes a lot of sense. And i agreed with him, from a parsimonious point of view an eternal never ending cycle makes al lot of sense.

    However, looking out at our own universe and understanding what we do about the laws of nature, i wondered how plausible it could be
    that this or any other cyclic model was the answer to what was going on.

    From my layman understanding, the current mainstream view is that dark energy we keep pushing the universe apart and everything
    will get cold and dark.

    So like i said, i am interested in knowing if an eternal cyclic universe is possible under the current understanding of the laws physics.

    Just because something is intuitive and "makes sense" does not necessarily mean it is right !

    Thanks
    Far away is close at hand in images of elsewhere...

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    Quote Originally Posted by kevin1981 View Post
    So like i said, i am interested in knowing if an eternal cyclic universe is possible under the current understanding of the laws physics.... Just because something is intuitive and "makes sense" does not necessarily mean it is right !
    That "sense" is subjective only. There's nothing physical that supports the view.

    A more straightforward cyclic universe was speculated for many years, but that was when it was figured that the expansion must be slowing down, based on all the mass/energy within the universe with its gravitational attraction. (That makes "sense.") Re-collapse was one of three possible scenarios in this situation. (The others were "continue to expand forever," or "sit on the knife-edge between the two.") IIRC, the "cyclic" part of a re-collapsing universe was speculated in a handwavy sort of way, but when investigated, they couldn't make it work due to quantum physical constraints.

    But then measurements of distant objects implied the acceleration only slowed for the first several billion years, then it started speeding up. So the possibility of a "straightforward" sort of cyclic universe became very remote. Of course, it is unknown whether the current state could undergo some seriously nonlinear transformation, but there's no known physical process that provides any "sense" to such a speculation.
    Everyone is entitled to his own opinion, but not his own facts.

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    Quote Originally Posted by kevin1981 View Post

    Is is possible that we live in an eternal universe that goes through never ending cycles ?





    I like this video which traces universe history into the trillion and trillions of years. It doesn't look cyclic at all. It is interesting how later universe evolution occurs on vastly large timescales but there doesn't seem to be a state that slows, ends or reverses the flow of time.

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    Moved to S&T for discussion.
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    Very interesting material. You first have to consider that atoms are made entirely of photons.
    Alfred Schrader 2019

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    Quote Originally Posted by alfredschrader View Post
    Very interesting material. You first have to consider that atoms are made entirely of photons.
    Alfred Schrader 2019
    alfredschrader

    You have promoted these ATM claims before. Do not bring them up again, particularly outside of the ATM forum.
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