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Time Before the Big Bang?

  1. Dec 8, 2011 #1
    For simplicity, lets just imagine that our big bang is the only big bang, ever.

    People always ask me, when did the universe "explode" in the big bang? How long did it take, and what was before it? I always get caught in my own words when they ask, as I have never really pondered these questions. After thinking about this for a second, I tell them "It didn't take time. It happened all at once, since before the big bang, there was no time." I've never heard of this, or read anything about it, but am just assuming that this is true (just a little theory i came up with in my head?) I'm just asking if this is true.

    Thanks!
     
  2. jcsd
  3. Dec 8, 2011 #2

    Drakkith

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    Tell them that we simply don't know and the Big Bang is simply a point in time where the standard model of the universe breaks down. We don't use it beyond that point. There ARE other models that try to predict the universe before the big bang, but there is zero evidence.
     
  4. Dec 8, 2011 #3
    As an interested and not too knowledgeable layman, your answer seems to me to be about all that can be said about it. Of course, many of us wonder, and speculate, about the OP. One of the things I wonder about is: can/do astrophysicists and cosmologists say that certain "pre-big bang" scenarios are more likely, more reasonable? And why?
     
  5. Dec 8, 2011 #4

    Drakkith

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    I only know of about 2-3 that are even accepted as "reasonable", so I really can't say. I would assume so though.
     
  6. Dec 8, 2011 #5
    Thanks for the honest reply. Here's another question.

    Are the computer simulations of the very large scale structure of our universe (presumably extending beyond our observational horizon) based in any way on assumed pre - big bang conditions, or are they based solely on extant observational data (in conjunction, of course, with theoretical inferences based on that data)?

    I'm absolutely fascinated with what I've learned of this (via science videos, with apparently good pedigrees, at YouTube).
     
  7. Dec 8, 2011 #6

    Drakkith

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    I believe they are based only on our observations and current understanding of science. But I'm not an expert on cosmology.
     
  8. Dec 8, 2011 #7

    DaveC426913

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    Our understanding of the BB is that we believe the 4 dimensions of space time were created in the BB, so it is believed that time (as we know it) did not exist before that event.
     
  9. Dec 8, 2011 #8

    Chronos

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    Einstein deduced space and time are irrelevant prior to the 'big bang'. This is not to say they did not exist, merely to say they cannot be defined with respect to our observable universe.
     
  10. Dec 8, 2011 #9
    I don't know of any particular reason to believe that. That is, it seems to me to be essentially speculative. We might just as well assume some sort of preexisting medium, or whatever, mightn't we?

    As Drakkith said, "the Big Bang is simply a point in time where the standard model of the universe breaks down".

    Isn't that the case?
     
  11. Dec 8, 2011 #10
    Irrelevant wrt our understanding of our universe during Einstein's time. Yes, that makes sense to me.

    However, there is the current observational inference of accelerated universal expansion. Might this be accounted for wrt topographical anomalies in a preexisting medium?

    Not defined, I agree. But nonetheless speculated about -- wrt the only data that's available, ie., our observable universe. If one assumes a preexisting reality, is there any particular reason to assume that that preexisting reality is essentially differerent from the reality of our universe?
     
  12. Dec 8, 2011 #11

    Chronos

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    You are assuming a definition of 'reality' that has no observational support.
     
  13. Dec 8, 2011 #12
    I'm not necessarily assuming anything. What I asked was if one assumes a preexisting reality, then is there any reason to assume that that preexisting reality is essentially different from our observationally supported reality(ies) (inferred or directly observed)?
     
  14. Dec 9, 2011 #13

    i would just like to raise a point that time do existed before big-bang. According to quantum physics, there is a moment of time called planck time which is the time before big-bang. Correct me if i'm wrong
     
  15. Dec 9, 2011 #14

    DaveC426913

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    No. planck time is a unit of time. It's how long light takes to travel one planck length.

    What you may be thinking of is the plank epoch, which is the first planck time unit after the Big Bang i.e. from 0 to 10^-43 seconds of its life.
     
  16. Dec 14, 2011 #15
    thanks dave for the clarification!
     
  17. Dec 14, 2011 #16
    Before one discusses whether something existed or not, a well articulate definition of the term is required. I am unaware of how time is defined within The Corpus of Cosmology. If someone can provide a succinct definition of time then it will be easier to evaluate the veracity of the statements being made.
     
  18. Dec 14, 2011 #17
    Doesn't eternal inflation tied to String Theory seem to imply that time may hve existed before the Big Bang ( as loose as the connection is between these two theories! ). Or, stated differently the multiverse existed before the Universe.

    Although, since eternal inflation is only eternal into the future, I guess this just pushes the questione further back, as one could then ask what came "before" the multiverse.
     
    Last edited: Dec 14, 2011
  19. Dec 14, 2011 #18
    I have had similar conclusions / questions. What came before the Universe and then Multiverse? What could be beyond the universe - and not just the observable universe? and even what is in between the smallest quanta scales? Perhaps these things are just so different to our local reality as to be impossible to imagine or understand?
     
  20. Dec 14, 2011 #19

    Drakkith

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    There is no possible way to answer these questions currently. And also no way to know if there is any kind of multiverse or not.
     
  21. Dec 14, 2011 #20

    Chronos

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    Time prior to the big bang relies on the assumption it is somehow fundamental - independent of the universe. This is a dubious assumption, not unlike assuming gravity is independent of matter - which we are fairly certain is erroneous. Time and gravity are probably emergent properties of the universe and were undefined, or existed only as a potential at the instant of the big bang. A deeper discussion is provided by Florian Girelli, Stefano Liberati, Lorenzo Sindoni: Is the notion of time really fundamental? http://arxiv.org/abs/0903.4876
     
    Last edited: Dec 14, 2011
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