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Where did the Big Bang happen?

  1. Jul 27, 2012 #1
    The answer is 'everywhere and nowhere'.

    First of all, remember that our entire foundation is the cosmological principle, telling
    us that no point in the Universe is special. If there were a particular point where the 'Bang'
    happened, that would clearly be a special point and violate the cosmological principle.
    Rather, space and time themselves were created at the instant of the Big Bang (unlike a
    conventional explosion where the material flies through pre-existing space). If we take any
    point in the present Universe and trace back its history, it would start out at the explosion
    point, and in that sense the Big Bang happened everywhere in space.

    In another sense, the location of the Big Bang is nowhere, because space itself is
    evolving and expanding, and it has changed since the Big Bang took place. Imagine the
    Universe as an expanding sphere; at any instant 'space' is the surface of the sphere, which
    is becoming bigger with time (again I'm thinking of a two-dimensional analogy to our real
    three-dimensional space). The place where the 'Bang' happened is at the centre of the
    sphere, but that's no longer part of the space, the surface of the sphere, in which we live.
    In particular, being constrained to the surface of the sphere means we are unable to 'point'
    to the place where the explosion is supposed to have happened. However, all the points in
    our current space were once at the centre of the sphere, when the Big Bang took place.
    what do you say about this?
     
    Last edited: Jul 27, 2012
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  3. Jul 27, 2012 #2

    HallsofIvy

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    You are making the error of thinking that the 'big bang' did happen at a specific point in a space that existed before the big bang. That is an error because space itself was created in the big bang- previous to the big bang there was no "place' for it to occur. Every point in space was "where" the big bag occured.
     
  4. Jul 27, 2012 #3
    As HoI said, the big bang didn't just 'happen'. It's the state that the universe began in, in the standard picture.

    However, this is a very good explanation for explaining why the big bang wasn't some bomb going off in space.
     
  5. Jul 27, 2012 #4

    bcrowell

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    We have a FAQ about this: https://www.physicsforums.com/showthread.php?t=506991 [Broken]
     
    Last edited by a moderator: May 6, 2017
  6. Jul 27, 2012 #5
    The first section lacks evidenciary proof; the rest is a reasonable reflection of our best
    understanding....except this:

    does anyone know of any model that suggests this??
     
  7. Jul 27, 2012 #6
    I believe the OP is referring to the fact that a big bang singularity (as predicted by GR) would involve the universe having zero total size. However, we know that this can't be true, because quantum mechanics forbids a particle from being stuffed into a space smaller than it's wavelength (think uncertainty principle). So, we conclude that GR can't handle extremely small distances at extremely high energies.
     
  8. Jul 27, 2012 #7

    Chronos

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    My guess is space, time and the known laws of the universe were all emergent, so I consider it risky to assume any of the usual rules applied to the birthing process.
     
  9. Jul 27, 2012 #8
    Well, the situation doesn't just come up at the big bang. GR has similar issues with the center of a black hole, as you know. They're both the territory of quantum gravity, which we'll need to describe the big bang in any meaningful way. Loop quantum cosmology has made significant progress in this region in recent years.
     
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