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Simple Question about the Universe

  1. Nov 10, 2011 #1
    I have read in various places that the universe essentially consists of three principles: space-time, physical matter/energy, and the physical laws that govern the first two.

    Do we know the order in which these three things came into existence?

    I'm confused by the role of the physical laws. Are these laws necessary for the universe to exist? Do stars form into a barred spiral galaxy structure solely because of the physical laws that govern them?
     
  2. jcsd
  3. Nov 10, 2011 #2

    marcus

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    The simple answer is NO, we do not.

    I speculate that within your lifetime, or anyway the lifetimes of some of us here, we may be able to rule out the possibility that any of those three things first came into existence at the time of the "BB" or start of expansion. That is, we may have a model, supported by observational evidence, in which time runs back to conditions before "BB" without the model breaking down.

    We already have several models that go back before start of expansion. One or more of them are worked out in enough detail that one can try to make testable predictions: e.g. the way expansion starts may leave an imprint on the microwave background which can be looked for, as a test, given the kind of observational instruments one can expect to be launched in the next decade or two.

    As an illustrative example, perhaps the simplest such model (involving minimal extra assumptions) is Loop cosmology, in which gravity is quantized and turns out to repel at extreme density so there is a BOUNCE. A universe like ours, collapsing, reaches such high density that it rebounds and enters a natural period of inflation.

    So in that model, which can be both run in computer simulations and solved using equations, there is no beginning of time, spatial geometry, matter, or physical law. The smooth rebound that replaces the "big bang" is only the start of expansion, not of the other more profound awesome stuff you mentioned. Yes something happened 13.7 billion years ago, but the really Big Questions are put off---shoved back in time for possible later consideration. I guess you could say that instead of being "postponed" the Big Questions are "pre-poned."

    The general research area here is called "quantum cosmology" QC. (Quantizing the cosmological model tends to make the singularity go away---apparently it was an artificial result of not using quantum theory---and often makes time continue on back further into the past, in one way or another.)

    Although the research papers are mostly too technical, some readers might want to check out the titles, and some of the summaries at the beginning, so I will give a recent QC search link. This will get both Loop QC AND OTHER QC, and is restricted to papers appearing 2009-present.
    http://inspirehep.net/search?ln=en&...m=&d2y=&sf=&so=a&rm=citation&rg=10&sc=0&of=hb

    The search currently gets 288 recent QC papers which is too many but I have it ordered by the number of times papers were cited by other research, so you tend to get the most read and referred-to ones first. Looking over the first 20 or so will give an idea of what is happening in the QC field nowadays.
    Most of the top 20 listed will have some kind of REBOUND replacing the big bang, something that has gotten a growing number of researchers interested lately.
     
    Last edited: Nov 10, 2011
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