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Is Big Bang a good term?

  1. Apr 12, 2013 #1
    I'm new to this forum, so I apologize if this has been raised/discussed before, or if this does not make much sense...

    I've been watching numerous debates about the Big Bang and the origins of the universe, and I can't help but think that Big Bang is not a good term for describing the early universe, since it provokes questions that don't make any sense (such as "what caused the Big Bang", "what was before the Big Bang", etc...)

    When people hear the term "Big Bang", they think of it as some sort of an event that actually happened at some point in time (t0). On the other hand, if I understand it correctly, it's not an event that actually happened, but just a certain imaginary barrier that one can approach infinitely closely when going back in time (as a thought experiment) but which cannot be crossed. In other words, if you take any moment of real (existing) time (t > t0), there is an earlier existing moment (t0 < t' < t), so the actual Big Bang event is an imaginary concept and not something that ever happened in reality.

    I'm not sure if this has any physical bearing, but I would imagine that "t" could be substituted by a time function that actually goes back to -infinity when you approach t0 (going back in time), which would make the universe infinitely old (i.e. move the Big Bang moment back in time to -infinity) and avoid all these questions about the cause of the Big Bang, etc. Not sure if this could be done beyond the Planck moment, though...

    Anyway, if someone had similar thoughts on this, I'd appreciate some pointers. It just seems to me that the term "Big Bang", however simple it might be, is quite misleading (as are some other expressions often used in the various articles on cosmology, such as "the beginning of the universe", etc...)
  2. jcsd
  3. Apr 12, 2013 #2


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    A surprising number of cosmologists are studying models of the start of expansion involving a bounce. Here's one.http://arxiv.org/abs/1304.3122
    Planck 2013 results support the simplest cyclic models
    Jean-Luc Lehners, Paul J. Steinhardt
    (Submitted on 10 Apr 2013)
    We show that results from the Planck satellite reported in 2013 are consistent with the simplest cyclic models for natural parameter ranges i.e., order unity dimensionless coefficients, assuming the standard entropic mechanism for generating curvature perturbations. With improved precision, forthcoming results from Planck and other experiments should be able to test the parameter ranges by confirming or refuting the core predictions - i.e., no observable primordial B-mode polarization and detectable local non-gaussianity. A new prediction, given the Planck 2013 constraints on the bispectrum, is a sharp constraint on the local trispectrum parameter gNL; namely, the simplest models predict it is negative, with gNL < -1700.

    Cosmology with time going back before the start of expansion (eliminating the breakdown of theory called the "singularity") is a very active research area. There are hundreds of "big bounce" papers already and many young researchers getting into the field. So this paper I give as an example is simply that, one example.

    You can see, in the summary I quoted, the intense interest in testability among people working on bounce cosmology models. They are offering models which can be falsified by current or future observations.

    So I think there is no reason to assume that the start of expansion was "the beginning of time" or "the beginning of the universe", as one might read in popular accounts or hear claimed in mass media TV.

    As for the term "Big Bang" it is often pointed out that it is a very unfortunate choice of words. It is misleading because it suggests an explosion from some central point out into empty space. It was originally applied as a DEROGATORY term by Fred Hoyle, an advocate of steady state cosmology. He did not like expansion cosmology and he started using "big bang" as a dismissive epithet. It doesn't give an accurate idea, but it caught on, maybe because of alliteration/humor/cool sound?

    Here is a search for "quantum cosmology" in the research literature that has appeared since 2009.
    If you are curious it will give you an idea of the mix of approaches being studied, that go back before the start of expansion and avoid the classical (i.e. pre-quantum) failure called the "singularity". The classical vintage-1915 model does indeed fail at start, but that does not mean that nature needs to fail, or that contemporary models now being studied need to.
    Last edited: Apr 13, 2013
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