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An Evolving Universe

  1. Jul 14, 2011 #1
    Is it possible we will never know what caused the big bang due to the instance of the Big Bang being a by product of something we know nothing about and if so is it possible the Big Bang destroyed any evidence of any element of creation..?

    To progress slightly, if the universe is truly unique, how will we know we can understand the origins of the universe if the creation of the universe was a by product and in essence has evolved into a new universe, one removed from its parent/s or origins, will all subsequent universes be different

    e.g missing that 1 bit
     
  2. jcsd
  3. Jul 14, 2011 #2
    Of course this is entirely possible. I am not so confident as to think it is guaranteed we will ever be able to completely understand black holes, quasars, the big bang and the quintissential essence of a "beggining" of out universe.

    We shouldnt assume we will understand the beggining of the universe, it may be the fact just escapes us or it may be that we could never through science explain the beggining as it operates on a completely different context to the U now. As GR only holds for so long, quantum gravity theory is required for grand unification and it may be too esoteric or impossible to be understood based on the current metric of the universe - like being in a world entirely made of blue and trying to discover red - no matter what shades you make the blue it will never be red, a crude analogy but hopefully you get my point.
     
  4. Jul 14, 2011 #3

    bcrowell

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    You seem to be thinking of the Big Bang as an event that happened in a preexisting landscape of space and time. That isn't the way it's described in general relativity, which is currently the only theory of gravity we have that is supported by empirical evidence. Here are a couple of FAQ entries about that:
    http://www.astro.ucla.edu/~wright/cosmology_faq.html#BBB
    https://www.physicsforums.com/showthread.php?t=506991 [Broken]

    But anyway, I think we can modify your question just slightly and come up with an answer that is basically "yes" to an even stronger statement. As far as we know, practical issues make it impossible for us to gain information about certain times and places that existed at t>0 (where t=0, which would be the big bang, doesn't actually exist as a moment in time). For example, the universe was so hot and dense at t=1 minute that the only information we have -- and the only information we are ever likely to be able to get -- about events before t=1 min consists of nothing but statistical averages concerning things like the abundance of certain elements, but nothing whatsoever about specific events that occurred at specific times and places. Any detailed information about events before that has been obliterated more thoroughly than anything written on a piece of paper and thrown into a furnace. So it's not just that we can't access information about t<0 because "the Big Bang destroyed any evidence of any element of creation." We can't even access certain information about t<1 min because the heat of the early universe destroyed any evidence of anything that happened in the earlier universe.

    There may also be limits on our knowledge of the universe that are not just practical but fundamental. The universe may be either finite or infinite: https://www.physicsforums.com/showthread.php?t=506986 We also know that it has a cosmological constant. If it's infinite, then the accelerating expansion caused by the cosmological constant will eventually cut off any given observer from more and more of the rest of the universe (due to a cosmological event horizon), and there will be events in the early universe from which that observer can never, even in theory, receive information, because not even a ray of light could have gotten to him/her from that event, even given infinite time to travel.

    Although GR is the only theory of gravity we have that is well established empirically, there are other theories that would allow time to be extrapolated back before the big bang, and there are even theories such as Penrose's Conformal Cyclic Cosmology in which it is possible to get information about certain very specific events that occurred at specific times and places before the big bang.
     
    Last edited by a moderator: May 5, 2017
  5. Jul 14, 2011 #4

    phinds

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    I assume that you are not here contravening the rather detailed chronology given by Weinberg about events that occur after about t=1/100th of a second. These ARE, if I understand it correctly, "statistical averages" in a way, so likely do fit in with what you are saying, but they DO provide for more details of events than is implied by your statement. Possibly the only confusion I have about your statement is that you may be using the word "specific" in a more restrictive sense than I would, but Weinberg's book has been around for a while and I'm new to all this, thus my question.


    GR is to my mind on a par (or more) with Newton's "LAW" of gravity. We just call it a "theory" because that's now the prefered term so as to avoid any presumption of finality (and in fact we already KNOW it isn't final and we need a theory of quantum gravity to enhance it just as it enhanced Newton's). In other words, if we were using the same criteria today that were used in Newtons' day, we would call it the "law of general relativity". My question is, do any of these other theories have ANY established empirical evidence that they could be correct or are they just mental constructs at this point that can't (yet) be falsified but which are hardly on a par with GR even though GR and all of them share the name "theory"? Or put differently, am I correct in believing that if we WERE to call GR a "law" and not a "theory", there is no way we would even consider (right now) calling any of these others "laws"?

    Thanks
     
  6. Jul 15, 2011 #5
    Had similar thoughts myself where another BB just happens all over again after this universe has long since dissipated away, like a Russian doll concept. I suspect that the only evidence we have is that it seems nice and elegant being a cyclical BB event instead of a one off, never to be repeated BB event. Unfortunately, this is not a proof, and any evidence based on CMBR rings would also have to rule out all other possibilities.

    Does Penrose's CCC theory also dispense with the need for inflation altogether?
     
    Last edited: Jul 15, 2011
  7. Jul 15, 2011 #6
    I'd need to know how CCC suggests each Big Bang goes on to create another Big Bang and why these Big Bangs are happening



    Ex nihilo = Quantum fluctuation
     
  8. Jul 16, 2011 #7

    phinds

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    Ben, any chance of getting answers to my questions in post #4 ?

    Thanks,
     
  9. Jul 18, 2011 #8

    Chronos

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    You need evidence of an earlier incarnation of the universe to validate any such theory. Cosmologists are looking, but, without success to date. If each BB erases all evidence of earlier incarnations, it is effectively a refrierator light fairy conjecture.
     
  10. Jul 18, 2011 #9

    phinds

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    I know I've read that there is at least one hypothesis that there IS some remnant of previous universes but that presupposes the existence of previous universes as well as the correctness of the hypothesizer's belief about how the remnant would exist. I find this concept (previous universes) to be even more difficult to believe in than some of the other concepts in cosmology and QM, BUT I find that my native belief has nothing to do with the correctness of science so I'm curious ... are there any significant number of well-respected scientists who believe in the "previous universe" hypothesis?

    I see it mentioned in places like "through the wormhole" TV show but I consider that to be pretty much crap since it frequently has Morgan Freeman spouting utter nonsense ("information can be transmitted instantaneously across vast distances") that are a serious warping of current knowledge so I find that program to be entertaining but untrustworthy.

    Thanks
     
  11. Jul 18, 2011 #10
    phinds, I agree wormhole is an entertaining show and it raises awareness of the science of Cosmology which is a very good thing indeed in a world of ignorance. However, I hope it doesnt do more harm than good filling young minds with wrong ideas, if they are wrong. Perhaps it could be more clear when it is being speculative?
     
  12. Jul 18, 2011 #11

    phinds

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    Although they ARE very speculative sometimes (and often not clear that they are being so) in many instances they are NOT being "speculative" at all, they are just plain flat WRONG, and sometimes in seriously misleading ways. The most blatant example I can remember is the one in my post, where the "science editor" if there is such a person for this show, clearly does not understand non-locality and had Morgan Freeman making the statement I attributed to him. The quote may not be exact but the statement literally and unambiguously was that information can be transmitted instantaneously across vast distances.

    I was REALLY disappointed to find that show making such mistakes since I DO find it quite entertaining and well-produced (if you can overlook the occasional seriously bone-headed statement) even if sometimes very speculative without being clear that they are BEING speculative.
     
  13. Jul 18, 2011 #12

    bcrowell

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    I mean "specific" in a very restrictive sense. For instance, I just scratched my nose. That's a specific event. What I'm referring to as statistical averages would include abundances of elements, CMB anisotropy, and basically all other data we have from the very early universe. A counterexample to my statement would be something like the observation of gravitational waves from the collision of a specific pair of primordial black holes -- which we haven't seen yet.

    Penrose claims to have evidence from the CMB anisotropy to support his theory, but it's very controversial. In general, we know that GR is wrong before the Planck time, since GR is classical rather than quantum-mechanical. There are theories of quantum gravity such as loop quantum gravity that do seem to have started making some contact with observation: https://www.physicsforums.com/showthread.php?t=514640
     
    Last edited: Jul 18, 2011
  14. Jul 18, 2011 #13

    bcrowell

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    Oh, definitely. For instance, loop quantum cosmology makes a very robust prediction of a bounce. There is a significant number of well-respected scientists working on LQC, and I assume they're optimistic LQC is right, although I don't know whether they'd use the word "believe."
     
  15. Jul 18, 2011 #14

    bcrowell

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  16. Jul 18, 2011 #15

    phinds

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    very helpful, good links, thanks Ben
     
  17. Jul 18, 2011 #16
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