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Big bang from planck length

  1. Aug 26, 2014 #1
    All - my first post, and as a lay person interested in quantum physics, forgive me if my questions are naive or ill-informed.
    Is it possible that the Universe inflated then exploded into being from a singularity smaller than Planck length?
    If I understand the concepts properly, the Planck length is so small that matter spontaneously pops into and out of existence (i.e. quantum foam) and Heisenberg's uncertainty principle applies when trying to observe anything.
    What I'm wondering is if that means, over the incredibly vast scales of Cosmological time, that anywhere in the observable universe as matter pops into and out of existence at Planck length scales, if one piece of matter could eventually go rogue, inflate and obliterate the current observable universe, starting the cycle all over again?
    Am I understanding things correctly - or hopelessly confused?
    The idea occurred to me while I was watching bubbles of dishwash foam in the sink as I was washing the dishes.
    Maybe I need to get a dishwasher...
     
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  3. Aug 26, 2014 #2

    phinds

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    What you are missing is that the universe did NOT start at a single point in space. The extent of the universe is not known (it may be infinite in which case it has always been infinite, or it may be finite but unbounded) but it was never a single point.

    The term "singularity" in the context of the big bang does not mean "point" it means "a place where the math of our theories gives a result that is not physically possible and so that we don't have to keep saying that all the time, we're going to give it a name ("singularity") and just say that."
     
  4. Aug 26, 2014 #3
    Hmmm - a fundamental misunderstanding on my part clearly.
    So when physicists talk about inflation, do they mean the universe simultaneously inflating at all points, everywhere?
     
  5. Aug 26, 2014 #4

    phinds

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    Exactly so. "Inflation" is still not considered a fact, just very likely as it explains more than any other theory. Further discussion of all this in the link in my signature.
     
  6. Aug 26, 2014 #5

    marcus

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    I think that's a good way to put it! That does describe on very common picture of inflation.

    There are variants, in some scenarios inflation starts at different times in different regions. So it is more chaotic in its starting and stopping.

    But what you said is a good description of inflation say in our locale, as affects us and all the stuff we can see. That's the simplest.
     
  7. Aug 27, 2014 #6
    Right. So in effect, we have a very hot, ultra-dense soup which suddenly coalesces into cosmic scale matter everywhere? (or on different time scales according to different theories) rather than a big explosion per se (the expression big bang would appear to be a little misleading).
     
  8. Aug 27, 2014 #7

    phinds

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    "Bang" is way more than a "little" misleading because it so often makes people think of an explosion in space which is by definition something that happens at a point in space. "Big Bang" was coined by Fred Hoyle who preferred a steady state model. It has been widely "quoted" that he meant this as a derisive term but he denied that.

    Yes, the plasma of the early universe coalesced into atoms and things about 400,000 years after the singularity and the time of this happening is called the "surface of last scattering" and shows up as the Cosmic Microwave Background.
     
  9. Aug 27, 2014 #8

    marcus

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    I agree. There is no one dominant version of inflation. There are different ideas about what might have started it, how it worked, and how it came to stop. And it is still not considered a fact (as Phinds pointed out).

    Phinds I didn't see your reply as I was writing, didn't realize you had already responded. Basically just repeating your main points.

    Djamie it sounds like what you are asking about is the type of research called quantum cosmology---QC is theorizing about the very early universe and how quantum effects (you mentioned Heisenberg uncertainty principle HUP) may have been involved, and may have played some part in the start of expansion. HUP is the basic reason theorists speculate that a collapsing phase of the universe would BOUNCE (and avoid the unphysical condition of infinite density). Intuitively speaking matter and geometry resist being "pinned down"

    At the current time if you look at prevailing QC research you see somewhat of a change compared with 10 or 20 years ago, the models studied in at least half the papers now have the expansion of our universe begin as a rebound from a prior contracting phase.
    Searching with the Stanford "Inspire" research data base shows the changing research emphasis. Here are the QC papers that appeared since 2009.

    "quantum cosmology" since 2009, Inspire search:
    http://inspirehep.net/search?ln=en&...search=Search&sf=&so=d&rm=citation&rg=25&sc=0 (720 found as of 26 August 2014)

    "quantum cosmology" and not "loop" since 2009, Inspire search:
    http://inspirehep.net/search?ln=en&...search=Search&sf=&so=d&rm=citation&rg=25&sc=0 (355 as of 26 August)
    The loop QC models, among others, always involve a bounce.
    So do some of the non-loop, but others of the non-loop have no prior contracting phase and have things start with a quantum fluctuation.

    Before year 2000 the idea of starting with a quantum fluctuation was more popular. There was little or no Loop QC (it is a fairly recent development) and quantum bounce cosmology was less common in research.
    "quantum cosmology" 1995-1999, Inspire search:
    http://inspirehep.net/search?ln=en&...search=Search&sf=&so=d&rm=citation&rg=25&sc=0 (395 found as of 26 August 2014)

    "quantum cosmology" and not "loop" 1995-1999, Inspire search:
    http://inspirehep.net/search?ln=en&...search=Search&sf=&so=d&rm=citation&rg=25&sc=0 (368 as of 26 August 2014)
     
  10. Aug 27, 2014 #9
    Fascinating - thank you for your help.
    Some reading for me to do - and I may be back with some further questions.
     
  11. Aug 27, 2014 #10

    phinds

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    Marcus, I'm always happy to see your responses as they are always more extensive and informative than my own and I enjoy reading them.
     
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