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B Space expanding or Time speeding up? Part 2

  1. Apr 4, 2017 #1
    Two questions, underlined:

    I have read that the universe began with a singularity.
    Then space began expanding.
    How can space expanding affect a singularity? Has this conundrum been resolved?

    If time was speeding up, is would act the same as space expanding, but it would affect a singularity, bringing the temperature down. This would mean time pre-exists the universe.
    Many tests have concluded that space is not actually made out of "anything", so how can it expand?
    But time is unknown in the properties of its constituents, so may have a possibility of speeding up.
    In these two examples, time speeding up seems simpler, more elegant than space expanding. Is this correct? Or does it bring its own complications?
  2. jcsd
  3. Apr 4, 2017 #2
    Most Big Bang models do not actually include singularity. They can describe points in time very close to it, but not singularity itself, since infinite energy density, temperature, curvature etc are not mathematically tractable.

    It's like a mathematician talking about (0, t] set of real numbers. The set has numbers arbitrarily close to zero, but zero itself is not in that set.

    If you ask "so what do Big Bang models say about t=0 moment?", they usually presume that before you can extrapolate to t=0, new, currently unknown physics changes the picture, and nonsensical infinitely dense state never existed.
  4. Apr 4, 2017 #3
    How "time speeding up" theory explains CMB?
    Also, rotational curves of galaxies were analyzed already some 40 years ago, I think. No slowdown in distant galaxies was found.
  5. Apr 5, 2017 #4


    Staff: Mentor

    This is a highly idealized, notional model that is not the one that is actually used by cosmologists. The earliest state of the universe of which we have firm evidence is a hot, dense, rapidly expanding state that, according to our best current model, was what came out at the end of inflation. But we don't know how inflation started or what came before that (we have various speculative models that we are only in the very early stages of trying to test).

    Unless you can find an acceptable reference (textbook or peer-reviewed paper) that gives such a model (I'm not aware of any), it's out of bounds for discussion here. We can't discuss speculations that don't have a testable model.
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