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Vacuum a necessity for BigBang?

  1. Dec 21, 2007 #1
    Is vacuum a necessity for BigBang?
    I believe most acknowledged theory for the beginning of Universe states that BigBang happened when nothing existed but vacuum or void.
    But is there a physical observation or a well-established theory that BigBang can only occur in vacuum where nothing "exists"?
    Isn't it possible -maybe not probable but possible- that BigBang can occur anytime anywhere in our Universe regardless of its occupants?
    Could it be that "our" Bigbang occurred in a already-crowded universe? maybe this'd explain the imbalance of matter/antimatter following the primeval state of our universe.
  2. jcsd
  3. Dec 21, 2007 #2


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    No vacuum, no void. When the say "nothing existed", they mean nothing existed. The big bang was the beginning of space.
  4. Dec 21, 2007 #3
    Can quantum fluctuations in a vacuum trigger a BigBang in an already established universe?
  5. Dec 21, 2007 #4


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    Since by definition the big bang was the beginning of the universe, no. The question makes no sense.
  6. Dec 22, 2007 #5
    The question does make a sense if you think about baby universes that might "spawn" from ours at quantum-scale. Although we may have no way of knowing for sure, it's still mathematically possible.
    And that may happen "inside" a universe regardless of an eternal vacuum.

    I can provide you some links to broaden your "senses" Russ, if you want to.
  7. Dec 22, 2007 #6


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    No, this is most emphatically not what the big bang theory says. The big bang is NOT creatio ex nihilo. The idea of the big bang is that all of the mass-energy of the universe, everything that exists today, was concentrated into a infinitesimal volume. This is called a singularity. There is a huge difference between a singularity and nothing. A singularity is everything, just compressed into a small volume, quite the opposite of vacuum.

    What occured "before" that, e.g. a quantum fluctuation of universal proportions, is unknown and perhaps unknowable.
    Last edited: Dec 22, 2007
  8. Dec 22, 2007 #7
    Every black hole has a singularity at the center. Perhaps there is a "fractal" geometry to the universe with miniverses embedded inside the innumerable black holes, much like a mandelbrot set.
  9. Dec 22, 2007 #8


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    there is already a major professional literature about this with many different scenarios. I would be interested to know what authors you are thinking of. I don't mean popularizations, which are watered-down. I think you are familiar with the technical writings of some prominent people.

    Are you thinking, for example, of Andrei Linde (he was at Moscow and is now at Stanford)? Or Sean Carroll? Or Penrose? Or Vilenkin? Are you thinking about the Eternal Inflation scenarios?

    I would like to know where you are coming from, because we cannot deny the existence of a large technical literature by respected people about this kind of thing----but we should try to address what you have in mind specifically instead of talking in complete generality.

    Personally I do not find the Eternal Inflation scenarios very interesting or testable, they seem very speculative to me, almost like fantasy. Regarding that and various other scenarios as well, I am not worried that the vacuum beside me could explode and make another rapidly expanding universe, or that a domain wall from a big bang at the neighbor galaxy would suddenly pass thru Berkeley and kill us. :biggrin: You probably aren't either.
    Also I don't think that OUR big bang hurt anybody else in a prior spacetime region. I think if it did begin in another region it was probably in a black hole and our universe expanded OUT THE BOTTOM of that black hole (so to speak) in a way that DID NOT INTERFERE and made an entirely separate region of spacetime. The mathematics for that is simpler, in my view, but it is all very speculative anyway. These are just my personal attitudes and should not influence you. But I am curious about how you envisage these things and whose work you have been reading. So tell us if you wish to, or give some links.
    Last edited: Dec 22, 2007
  10. Dec 22, 2007 #9
    The whole notion of a beginning of the universe makes little sense.
    Logically, one would think a big bang would occur when something that was under tremendous pressure is suddenly introduced to an environment with no pressure.

    But the something had to come from somewhere...or did it?

    In math, making something from nothing is easy. You just break zero into +1 and -1. You can further break -1 into -2 and +1 and on and on and on, as long as the sum total remains zero, you haven't created or destroyed anything on a net basis.

    So how did zero become +1 and -1? Did it require consious thought? Who's? Was "nothing" just bored with itself? Where did the first thought come from?

    The answers only lead to more questions.
  11. Dec 22, 2007 #10


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    I agree. But many cosmologists nowadays do not consider the Big Bang to be the beginning of the universe. One can discard the idea of a beginning of the universe, and assign the Big Bang a meaning which does make sense.

    For example Anthony Aguirre recently posted a paper where he explicitly stated that in the context of Inflation, the Big Bang corresponds to the reheating at the END of an inflation episode. If you believe in inflation (as many cosmologists seem to) then the precise meaning of Big Bang, for you, refers to conditions right after inflation stopped, and the inflaton field decayed.

    I don't like Aguirre's paper, but he is highly influential. One has to acknowledge how top professionals are using terminology in contemporary cosmology. I will get a link to the paper.

    Eternal Inflation, past and future
    Anthony Aguirre
    38 pp., 6 color figures. Contribution to R. Vaas (ed.): Beyond the Big Bang. Springer 2008
    (Submitted on 4 Dec 2007)

    "Cosmological inflation, if it occurred, radically alters the picture of the `big bang', which would merely point to reheating at the end of inflation. Moreover, this reheating may be only local, so that inflation continues elsewhere and forever, continually spawning big-bang-like regions. This chapter reviews this idea of 'eternal inflation', then focuses on what this may mean for the ultimate beginning of the universe. In particular, I will argue that given eternal inflation, the universe may be free of a cosmological initial singularity, might be eternal (and eternally inflating) to the past, and might obey an interesting sort of cosmological time-symmetry."
    Last edited: Dec 22, 2007
  12. Dec 25, 2007 #11
    my theory is that our universe was started from an extremely large star that exploded and all of its matter was blasted ouwards. but around that big star there are other stars its size perhaps kazillions of miles away
  13. Dec 25, 2007 #12
    When people asks questions about: "what was prior to the big bang?" or "who made the big bang?" I believe they may have misunderstood something. If, there was a big bang, though what I'm going to say doesn't depend on that notion - we being here doesn't make any sense. And I'm not saying this in a religious kind of sense, it concerns everything matter/ennergy. It being here does not make any sense.

    And why is that? Well, the answer is quite easy: "because we are animals!" Simple and elegant. We are a result of evolution, and our set of thinking is a result of this. We come from something, our parents. And they come from something, their parents. And so it goes. Yet, it is hard to fully comprehend that we came from maybe the one cell a "billion" years ago. But we still do, we comprehend. By use of logic. And so we can go, further and further.

    But it all stops when talking about the big bang. Because: what was prior, or was there a prior?

    The easiest answer is: our logic is flawed. We have a logic that is adequate to reason all the way back to the "beginning of time," but there it stops. And all the answers we come up with, which are based on the present logic, will be wrong. One must first deduce a logic that do not demand "a moment of creation. And this logic have to be coherent to todays logic.

    All speculations on what came before a big bang will therefore be unfruitful. THat is, when it is given that there was a big bang ;). Because if there wasn't, one can push our logic even further back. Even then we will encounter the same qustions about "the beginning" or what to call it.
  14. Dec 25, 2007 #13


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    The big bang was an episode of high density and temperature but there is no scientific evidence showing that it was the beginning.

    Henxan, you don't seem to have been paying attention, because what you say is directly contradicted by the facts. There is plenty of cosmology research in the past 5 years which pushes back before the high temperature event called the big bang. And the new research has had important consequences.

    We cannot say we KNOW, because the models have not yet been distinguished. Some models which fit the data break down and do not go back further. Other models which fit the data equally well do not break down---and they continue back further. As yet, we cannot say that there was or was not a beginning. First ways must be developed to test the models empirically to see which is more accurate.

    The new research (mainly in quantum cosmology) in the past 5-7 years has had major consequences. This year we have seen international conferences and workshops focus all or in part on models of pre-bang. It appears to be a fertile research area for young people to get into. New people are becoming prominent whose names were not known back in the 1990s. The face of cosmology is being changed, at least in part by the emergence of modern quantum cosmology.

    If you want some links to recent (2007) articles to read, please ask and some of us (myself or others) will be happy to post some for you.
    Last edited: Dec 25, 2007
  15. Dec 25, 2007 #14
    The problem is not so much with logic but with the assumption of creation. We don't see things being created, what we see is things that change instead. Why should anyone assume that existence needed to begin at some arbitrary point? Since this gratuitous scenario generates unanswerable paradoxes, the logical approach is to drop the assumption. The method is simple:

    Problem: assuming some paradox, resolve it.
    Solution: remove the assumption.
  16. Dec 25, 2007 #15


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    that impresses me as a very sensible attitude, and it goes along with modern big bang cosmology, which redefines the big bang as a change (rather than a beginning).

    It becomes more intuitively understandable, as a brief episode of very high temp and pressure.
  17. Dec 26, 2007 #16
    "Since by definition the big bang was the beginning of the universe"

    The big bang thoery starts at planck time. Before that you will need a Quantum Gravity theory.
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