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I am a software engineer and not an astrophysicist but I want to know if anyone is working on sorting out what exists outside the universe?

So what about outside spacetime? what is there? or shall I assume there are infinite galaxies? and even that is not a satisfying answer. I know this question might get closed soon ... but guys please tell me what is there outside the space as we know it? since childhood I have wondered about this.

Its really a simple question. If we say that we live "inside" a Universe ... then we are objectively saying that there IS something "outside" the universe as well? Am I crazy? What exists there? Is it just empty space? Or what?

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Possible duplicate: physics.stackexchange.com/q/7359 –  Qmechanic Apr 5 '11 at 19:25
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Short answer: We have no clue –  user1708 Apr 5 '11 at 19:51
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marked as duplicate by Qmechanic Sep 18 '13 at 17:06

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2 Answers

you are not crazy. its a very good (and deep) question but current physical theories don't have any compelling evidence to work about what sort of space, space-time itself would be embedded on, or if such a embedding space could have any physical consequences on our space-time. There is brane-world scenarios where such models are studied, but no evidence to support anything of this sort so far

from the current factual perspective, current General Relativity assumes space-time is curved due to gravity sources, but to understand curvature mathematically you don't need to assume any outer space, so an expanding space-time in itself is a totally consistent idea mathematically. There is no requirement to postulate an outside, ambient space

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"Curiosity" as einstein would describe it is the "requirement to postulate an outside, ambient space ... " –  Ritwik G Apr 5 '11 at 19:00
    
that is not what i mean with requirement; requirement in this context would mean that: introducing such model would predict something that cannot be predicted otherwise. So for the purpose of my answer, i'm explicitly and intentionally disregarding any aesthetics or philosophical requirements –  lurscher Apr 5 '11 at 19:08
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There exists a mathematical space into which our universe is embedded, but it is mathematical because nothing as we know it can get out of the universe or enter the universe.

After the big bang the universe is expanding in three dimensions analogous to the way that the surface of a balloon expands in two dimensions: all points on the balloon surface recede from each other and the surface gets large. The balloon surface is not expanding into anything, as far as the points on the balloon go. In three dimensions all points in our universe recede from each other, having all started from the one point of the big bang.

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The whole point of coordinate-free physics (of which I have more or less no comprehension) is to dispense even with the need for a mathematical overspace. –  dmckee Apr 5 '11 at 19:16
    
I don't know that a downvote is really called for here. One can embed the manifold in a higher dimension space if you want, its just that such a thing must not have any physical meaning or effect. –  dmckee Apr 5 '11 at 19:33
    
@dmckee, is true that is not needed to understand all our current observations, however in other related questions it has been discussed that general relativity doesn't explain the current space-time topology or how it might change over time. See physics.stackexchange.com/questions/1787/…, @anna, i simpathize with your viewpoint, +1 –  lurscher Apr 5 '11 at 19:37
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