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Poll: Is the universe finite?

  1. Yes, there is general agreement among the experts that it's like that

    2 vote(s)
    25.0%
  2. No, there's a general consensus that it's flat and infinite

    3 vote(s)
    37.5%
  3. It's controversial---the experts disagree

    3 vote(s)
    37.5%
  1. May 13, 2003 #1

    marcus

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    Is the universe finite?

    Was the big bang located at a single point and did it involve a finite amount of energy?
    Is space like the surface of a balloon (except 3D instead of 2D)
    that is gradually expanding?
    Does it have positive curvature so that if you continue along a straight line you might get back to the same place?
    Are cosmologists at odds about the finiteness vs. infiniteness of the universe or has a consensus developed based on reliable observations?
    I want to know what PF posters think so I'll try to construct a poll---this is my first attempt at a poll.
     
    Last edited: May 14, 2003
  2. jcsd
  3. May 14, 2003 #2
    Re: Is the universe finite?

    The only thing that scientists largely agree on is that space has no boundaries or edges. It is called the no boundary proposal (Stephen Hawking).

    Our measurements of space indicate it is perfectly flat, which means that it is very large indeed. We can not distinguish between an infinite space and a very large space in observations.

    The Big Bang supposedly was not a single point in space, but all of space was expanding.
     
    Last edited: May 14, 2003
  4. May 14, 2003 #3

    Eh

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    The no boundary proposal is something entirely different.

    But the question of infinite can never be confirmed by any experimental evidence. But if nature holds no other infinites, I would wager space is finite.
     
  5. May 14, 2003 #4

    russ_watters

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    The way the poll is worded, its a factual question, not an opinion. The vast majority of experts DO in fact agree that the universe is boundless, yet is epanding and is therefore finite. Thats a fundamental aspect of the Big Bang theory.
     
  6. May 14, 2003 #5

    Eh

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    Those same experts will tell you expansion does not necessarily equal a finite universe.
     
  7. May 14, 2003 #6

    russ_watters

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    Staff: Mentor

    If it started small with a Big Bang Singularity, it must have been finite when it began. So does that mean at some point in time it went from finite to infinite? That makes no sense.
     
  8. May 15, 2003 #7

    marcus

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    Nobody claims the big bang singularity was pointlike
    on the contrary
    here is a cosmology FAQ about that

    http://www.astro.ucla.edu/~wright/infpoint.html

    QUESTION "How can the Universe be infinite if it was all concentrated into a point at the Big Bang?"


    The answer begins: "The Universe was not concentrated into a point at the time of the Big Bang. But the observable Universe was concentrated into a point...."

    Then it shows a picture of the big bang (a finite section of an infinitely extending big bang).

    The part of the universe from which light has already reached us, the observable universe which is around 80 billion LY diameter at present, WAS concentrated a single point------like in the picture---but that is only a finite piece of an infinite universe

    Here is an alternative link to the Michael Turner survey article
    on new (post 1998) cosmology:

    http://www.lp01.infn.it/proceedings/turner.pdf

    I posted a link to this article in the Los Alamos archive earlier
    but now that does not seem to work. Fortunately the alternative
    does, at least for the moment. This article is invaluable because
    authoritative and up to date (as of spring 2002).
     
    Last edited: May 15, 2003
  9. May 15, 2003 #8
    AFAIK, there are really only two possibilites now: a flat, infinite universe -- this is the preferred view -- or a flat finite universe with nontrivial topology. ie, the universe 'wraps around' spatially like a game of Asteroids. I am told there are problems with inflation in a finite universe, but there are sky searches and stuff underway to look for evidence of it (ie a hall of mirrors effect.) see

    http://arxiv.org/abs/astro-ph/9802012
    http://arxiv.org/abs/gr-qc/0005128
    http://arxiv.org/abs/gr-qc/9911049
     
  10. May 15, 2003 #9

    marcus

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    In effect, a "Donut" universe---a zerocurvature cylinder with ends identified.
    I have seen mention of sky searches for repetition of that sort
    but I also get the strong impression that "hall of mirrors" donut is viewed as only a marginal possibility and that preference is predominantly for flat infinite.
     
    Last edited: May 15, 2003
  11. Sep 11, 2004 #10
    Finite Universe?

    Well this is a serious question. The only problem is that you will probably never get anyone to tell you the Truth. Astronomers, Physicists, nor Mathematicians, actually understand Nature. In other words, at best, all knowledge is a Guess of varying Degrees ... No one knows the Absolute Truth, or anything reliable about Mathematics or the Mathematical Sciences. In which case, with all their Billions spent on Research, if they get anything correct ... Well. Do you believe in Luck? Because, for a fact, the correctness of any subject being taught is a Probability Measurement.

    Now, consider what would be the effects upon the expanding Universe Theory if the Motion of every Object followed an Orbital Path? I mean, just think, in a case such as this, every Object would appear, relative to their Orbital Paths, either moving away or towards Earth ... Thus, rendering the same visual effects as described in the Big Bang Theory.

    e. terrell
     
  12. Sep 11, 2004 #11
    No, the universe is not finite. It is infinite. There is no end to it. If there were, where woudl it be? Would you be notified with a sign that says, "The Universe ends here"? It's silly to say the universe is finite. It makes no sense.
     
  13. Sep 11, 2004 #12
    I personally think there should be 100 % of the votes in "controversial". The others implies that you are biased on something that has not been proven. That's not a really good stand to take. I would like to say it is infinite, but until it turns from a theory to a law, it's controversial.

    Then again, in theory, aren't all laws theories? :smile: jk

    Paden Roder
     
  14. Sep 11, 2004 #13
    Actually, you are right. All laws are theories. Nothing is proven to be right and never will be.
     
  15. Sep 12, 2004 #14
    I guess its controversial – the experts disagree.

    How can space extend out forever? I don’t think it can. So what is the geometry of space if its not infinite?
     
  16. Sep 14, 2004 #15
    Q. Was the big bang located at a single point and did it involve a finite amount of energy?

    A. Yes.

    Q. Is space like the surface of a balloon (except 3D instead of 2D)
    that is gradually expanding?

    A. Yes and No. The universe is like a balloon (finite). But, only a subset of this volume contains all normal matter.

    Q. Does it have positive curvature so that if you continue along a straight line you might get back to the same place?

    A. Yes

    Q. Are cosmologists at odds about the finiteness vs. infiniteness of the universe or has a consensus developed based on reliable observations?

    A. Finite - minority
    infinite - majority

    I think the majority favor an infinite universe only because a reasonable alternative has not been presented to date that would indicate otherwise.

    Until we have a better understanding of dark energy and dark matter, we will not be able to explore some options that should come to light explaining how contraction would be possible when considering the present rate of expansion.
     
  17. Sep 14, 2004 #16

    Chronos

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    No, it happened everwhere. The total energy involved may, however, been huge thought finite (opinion).
    Possibly. But, I think the answer is a bit more complicated than that.
    It probably has some curvature, albeit might be local. No, you cannot travel back to the same place. You would spiral outwards with expansion.
     
  18. Sep 15, 2004 #17
    The notion of an infinite universe leads to obsurdities - particularly if its homogenous - there would be an infinite number of identical solar systems, with identical earths and human populations - even an infinite number of Yogi(s). All things of finite probabability are repeated an infinite number of times (plentitude with a vengence). We would be the victims of a gigantic cosmic hoax - each of us falsely believing we are unique.
     
  19. Sep 15, 2004 #18
    Maybe these types of issues arise because somewhere along the way, theorists have slipped into digital thinking - as James Jeans once said: you can prove almost anything is you fail to consider the law of the excluded mean. The big bang may not have been a singular event - as Eddington said.."the most satisfactory theory would be one that made the beginning not too unasthetically abrupt. Perhaps inflation is not a phenomena that had a beginning and an end, but rather it is an ongoing process in a negative pressure environment that creates mass as it expands (an idea once posed by its originator). These models do not require a critical density universe to be infinite - ergo the choice between the finite and infinite is dissolves because there is no rational mathematical model for the latter.
     
  20. Sep 15, 2004 #19
    well, a theory not too old.. have said that the universe is finite and has the shape of a dodecaedron (12 pentagons in a round shape). and whenever the light comes in from a certain pentagon, it gets out from the opposite one giving illusions for other pentagons and dodecaedrons..
    but my question is: if that universe if finite and it is completly inside this dodecaedron.. then from where comes the light which gives different illusions.. which make us think that our universe is infinite?
     
  21. Sep 26, 2004 #20
    The universe is a creation out of the state of eternity. Eternity is a condition without time. All is now. The creation was a dimensional energy differential. The universe will continue to expand and exist until all energy differentials drop below the Planck level at which time no actions can take place. In effect all clocks stop ticking. Thus the universe is finite.
     
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