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Imagine an eruption of energy/mass $E$ from a singularity $O$, as in a Big Bang. After the energy/mass $E$ is all at more than a distance $d$ from $O$, is it for some value of $d$ possible that there could be a new eruption of energy/mass from $O$, i.e. a new Big Bang? If yes, is there an upper limit to the number of succeeding Big Bangs?

Qmechanic
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Sapiens
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    That is a very incorrect picture of the big bang. – MBN Apr 03 '14 at 18:00
  • I am asking questions, and am not presenting a picture of the Big Bang. – Sapiens Apr 03 '14 at 18:06
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    The Big Bang wasn't an eruption of energy/mass E from a singularity O. Your question is predicated on the idea that the Big Bang was like an explosion happening at a point with everything flying away from that point. The Big Bang was completely different from this, so as it stands your question can't be usefully answered. – John Rennie Apr 03 '14 at 18:15
  • How was it different from an explosion happening at a point? Is it that space itself is thought to have come into existence with the Big Bang? If the latter, why not take the center of the spatial ball coming into existence as the origo O of my question? – Sapiens Apr 03 '14 at 18:20
  • You might be interested in this pop-sci level description of the Big Bang that I posted on the SciFi Stack Exchange. Alternatively see this answer for a more rigorous discussion. – John Rennie Apr 03 '14 at 18:20
  • Or I posted the same answer on this site here – John Rennie Apr 03 '14 at 18:22
  • In your statement "Actually, at the moment of the Big Bang the FLRW metric predicts that the spacing between any two points falls to zero, but the universe remains infinite.", what is the meaning of "point". Is it the same as the meaning of "physical particle"? – Sapiens Apr 03 '14 at 18:27
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    @user24406 point would mean spatial coordinates. But the idea you have of the Big Bang is an event that happens at a location. In truth, the Big Bang is a moment in time, not an event (don't be fooled just because we called it a "bang"). It had no location, so one cannot ask what if it happened again at the same or another location. – Jim Apr 03 '14 at 18:43
  • John Rennie: It seems from your other post, and other considerations, that some of these matters are still up for grabs as they concern areas where relativity and QT conflict. If the physical universe is finite and the universe is infinite, I cannot see why the metaphor of an erstwhile explosion is not apt. – Sapiens Apr 03 '14 at 18:44
  • Jim: A change in spatial coordinates merely can come about simply by a mathematical transformation! But surely physicists mean something more than the truism that one can change coordinate system ad libitum when describing physical reality. In particular, the intended meaning of the Big Bang must include the idea that the physical particles were infinitely close to each other - whatever that means. If space itself outside the lump of matter were matter-less, I do not see why anyone here believe that the Big Bang cannot be assigned a place; what mathematics would forbid such an assignment? – Sapiens Apr 03 '14 at 18:58

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There are several scenarios that point out cyclic cosmologies. The first one is called Matter bounce cosmology which is based on the idea that that the universe originated from a cosmological bounce in which quantum fluctuations develop into a scale-invariant spectrum of curvature perturbations. The bounce is realized beyond Einstein's General Relativity and introduces new forms of matter which violates key energy conditions, since these two aspects allows to avoid the cosmological singularity. Another one is the so-called Ekpyrotic Cosmology which represents our universe as a Dp-brane which arises in string theory. There are two branes separated by a 5-dimensional bulk spacetime (one of those branes is our universe), which contains an attractive force called quitessence which causes the two branes to approach, collide, move through and bounce off each other. The collision seen from an observer living in one of the branes look like a big bang. This collisions and separation of the branes happen infinitely many times.

For more information check the following arxiv articles:

  1. Lehners, J., Ekpyrotic and Cyclic Cosmology, arXiv:0806.1245v2
  2. R. Brandenberger, The matter bounce alternative to in iflationary cosmology," arXiv:1206.4196v1.
Leonhard Leibniz
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