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After reading Does the universe have a center? and trying to find a place in my mind for "There exists no center", I asked myself:

If there is no center, in what direction our universe will collapse, as soon that time has come? Does this mean the collapse will happen in an instant everywhere?

And if not so, couldn't we say, the center is that point where the collapse finishes(Even if we couldn't determine where this will be)?

ps.: While writing this I made a scene in my had where a spherical object is expanding in every direktion without adding any matter to it and without the posibillity to describe anything outside the sphere. When this spehre now starts collapsing without destroying any matter the same way it didn't create any (thats the actual concept of our universe, isn't it) then everything will get closer to a specific point if observed from "outside the box". But inside the sphere you will just notice that everything is reduicng its distance to everything else without beeing able to notice a specific point this things are moving to as this "point" would be a coordinate of a higher dimension.

Is this more or less the answer to my problem?

Or would there be such a point even from inside, but we just can't determine it by any mean?

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  • $\begingroup$ There are no physical signs that are indicating that the universe will collapse, again. What our cosmological data and models are describing are changes in the matter density of the universe and in its dark energy content. These are also linked to a number of distance and time scales that are physically meaningful from any given vantage point. The spherical representations that you are used to from various media publications are no more meaningful than a medieval disk shaped representation of a flat Earth was. $\endgroup$
    – CuriousOne
    Commented May 31, 2016 at 12:11
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    $\begingroup$ @CuriousOne: So you are telling me earth isn't flat? I know people all arou.... errh allaflat the world who know you are wrong. sarcasm. Ok, so: The concept that the universe will at some point collapse again isn't that up to date anymore? What are keywords to research about and which are to be avoided, when I'm interested into getting an idea of how the universe is "presented"? $\endgroup$
    – Zaibis
    Commented May 31, 2016 at 12:17
  • $\begingroup$ You don't need to think about collapse to worry about this: collapse is just expansion run backwards (not exactly, but close enough for these purposes) so you can instead ask: ' if the universe has no centre, how can it have expanded from a small initial state?': if you understand one you understand the other. $\endgroup$
    – user107153
    Commented May 31, 2016 at 16:42
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    $\begingroup$ Look into the latest dark energy and precision cosmology. It seems that nature has given us, at least in our era, a rapidly expanding universe that will, for the foreseeable future continue to expand and accelerate. Already today, all but the local group of galaxies are out of our reach. In maybe ten billion years time nothing will be "left" for us "to visit" but the merger of the milky way and Andromeda. Eventually even this may dissolve, but we can't really know the future. This is just speculation based on a few data points. $\endgroup$
    – CuriousOne
    Commented May 31, 2016 at 20:44
  • $\begingroup$ @CuriousOne --I think that what the OP's getting at is, whether a "critical density" is likelier to result in the collapse of a spherical universe than in the collapse of a universe where space is either hyperbolical or flat. (I haven't actually seen a cosmological model for any local or single universe whose space would consist of "a" sphere, but Nikodem Poplawski has an ECT-based multiverse model whose LU's would each consist of the space between one sphere inboard of another, "like the skin of a basketball".) SVP, save me a question by responding to this comment. (?'s make me nervous.) $\endgroup$
    – Edouard
    Commented Feb 28, 2022 at 22:07

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Sticking with the sphere analogy, first remember that in this analogy, the Universe is a shell, i.e. only the points on the surface of the sphere exist in the Universe, not points inside or outside. If the Universe has a spherical geometry, then the centre would be the centre of this sphere, which is not in the Universe anymore (which is why one would say the Universe has no centre, defined as the point where the big bang happened.) This is the point where it would collapse to, if it ever did.

It is more likely, however, that the centre of the Universe is everywhere. This is consistent with a critical density Universe with flat geometry (which is what most cosmologist believe our Universe to be). In this scenario, the centre of the Universe expanded, but not into a sphere, rather into a flat shape, and thus the centre of the Universe is everywhere. In this case, the Universe will never collapse, but will stop expanding as time goes to infinity.

For completeness I'll add that for a negative curvature hyperbolic Universe, the centre would also not be in the Universe. I think it's fascinating that whatever our Universe turns out to be (though strong evidence for flat), the Universe will either be everywhere or nowhere in the Universe.

Geometry of the Universe

[image: http://abyss.uoregon.edu/~js/images/universe_geometry.gif ]

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  • $\begingroup$ you mean the center be everywhere or nowhere? $\endgroup$
    – Zaibis
    Commented May 31, 2016 at 12:25
  • $\begingroup$ @Zaibis In the current Universe, yes. I should also say though that we define the centre as the point where the big bang happened, so obviously it was in the Universe at the moment that happened. $\endgroup$
    – hsnee
    Commented May 31, 2016 at 12:26
  • $\begingroup$ You wrote "the Universe will either be everywhere or nowhere in the Universe. " Also you should add your last comment into your answer, as this helped me a lot in understanding the basic concept of the spherical representation. But anyway all of these representations ever made and still make me not get where I can consider my self beeing on it and therefor I have trouble understanding the whole concept. Should I post a new question about it? $\endgroup$
    – Zaibis
    Commented May 31, 2016 at 12:32
  • $\begingroup$ What do you mean by "where I can consider my self being on it"? $\endgroup$
    – hsnee
    Commented May 31, 2016 at 15:40
  • $\begingroup$ My problem in understanding those representations is, while I'm expected to be within a 2 dimensional frame, where am I and in how far my actions (moving in directions) would affect my position on that plane. $\endgroup$
    – Zaibis
    Commented May 31, 2016 at 15:44

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