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Beginning of space, time, matter, energy

  1. Feb 20, 2006 #1
    Frederick’s “Empty Nest” post reminded me of a thought that I have had on occasion. Perhaps it is essentially what Frederick’s post is getting at, I’m not sure. (Note: This is not intended to imply a theory but is simply meant as a question about what we know or don’t know.)

    What is the evidence and / or theoretical basis for concluding that space and time (or spacetime) and normal energy and matter (and I suppose if they do exist dark energy and matter) all came into existence at the same instant and as part of the same process?

    In other words, from our current knowledge, what precludes the possibility that space itself already existed and was expanding (even accelerating) prior to a "big bang” bringing the matter / energy of our observable universe into existence to be carried along with the already expanding space?

    -PD
     
  2. jcsd
  3. Feb 20, 2006 #2

    Nereid

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    Well, since the 'earliest' currently solid physics can take us (QFT+GR) is a Planck second (in a Big Bang universe), 'nothing' must be the answer.

    If you choose to accept one or other of the many theories which claim to unify QFT and GR, then you will find your answer there.

    If you insist that any such unified theory must have observational/experimental support (beyond just support for QFT and GR separately), then you will have nothing to say.

    Putting this another way: 'spacetime' is a theoretical construct (GR the theory); choose another theory to work within, and your questions can only have meaning in terms of the constructs of that new theory.

    Unless, of course, you want to try to argue that there is some 'reality' which 'exists' independent of theory (beyond that which you yourself can experience directly with your own senses)! :smile:
     
  4. Feb 20, 2006 #3
    Of course, you could take the view that Hoyle was right and assume a Steady-State Universe where there was no beginning to even worry over... :)

    -Dan
     
  5. Feb 21, 2006 #4

    Chronos

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    You could, but there are a myriad of observations [or lack thereof] that rule out the possibility our observable universe is infinitely old. Of course it is possible the observable universe is a small region embedded in some larger, more ancient, and possibly infinite universe, but, that is not very interesting. It is doubtful such an entity would have any observational consequences in our universe.
     
  6. Jul 7, 2008 #5
    This idea (of the spontaneous creation of space/time/matter/energy from nothing) contains of course the inherent paradox that there already had to be something, before anything could exist, before any motion/change whatsoever could occur.

    So such a possibility is to be rejected before hand as such can not have possibly be the case.

    This only leaves room for time being eternal and also matter/energy being eternal (which we can conclude seperately based on the fundamental principle of conservation of energy/mass). We can only transform matter/energy into other forms, but in no way create or destroy it. And since matter/energy is inconceivable without there being time and space, hence also time and space are eternal.

    The idea of time being infinite (not having a begin) is not a paradox (and can not be ruled out beforehand), but the very idea of the infinite is of course inperceivable without contradiction.
    As can be worked out it is just because the infinity of time is a contradiction,that it is an eternal proces, unfolding endlessly in time.
     
  7. Jul 7, 2008 #6

    marcus

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    there is no evidence to conclude that (IOW no scientific grounds for assuming an instant of creation)

    So I agree with Nereid when she says the answer to your question must be nothing, i.e. no evidence.

    Nothing precludes possibilities such as the prior existence of space, and indeed matter and energy.

    The problem is that in order to talk about it you need a consistent mathematical model of the behavior of geometry and matter around the time of the big bang. And the model should be potentially testable by having observable consequences in the present.

    Classical (non-quantum) models break down at the big bang---stop computing, don't give finite numbers. On the other hand quantum cosmology models developed in the past ten years do not break down---so they let one follow time-evolution backward to a time of very high density and temperature (big bang conditions) and then on past there to an earlier period.

    A lot of people have now joined the quantum cosmology (QC) research effort so there is a lot of scholarly publication. You can get an idea from this keyword search of QC papers published since 2005
    http://www.slac.stanford.edu/spires...+date+>+2005&FORMAT=WWW&SEQUENCE=citecount(d)
    most of the first ten or twenty papers on the list of hits deal with QC bounce models---space and matter collapse to a high density state where gravity becomes repellent due to quantum effects, and then re-expand.

    nothing is said about why space and matter happen to be there, or if they came from anywhere or always existed---that's more philosophy. what they do in QC is they quantize the classical cosmology model and discover that it then does not break down, so it can be run further back in time---and an era of contraction appears. the next thing is to derive observable consequences for astronomers to look for, as a test.

    there are several approaches to studying before big bang which are being pursued, and a book is scheduled to come out around April 2009 which collects stuff by leading experts on this---chapters written from a variety of viewpoints. Not all the models involve a bounce like I described! there is quite a variety. It's going to be a thick (expensive) book. But that's a sample taste anyway.
     
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