QuantumT Posted April 30, 2019 Share Posted April 30, 2019 The universe expands! We can all agree on that. Some say that the universe is all there is. So the universe expands into what exactly? What I am trying to figure out is, if there is some sort of void beyond the universe? And if there is, the universe is not all there is, right? Even a void without space, matter and time is still "something". The problem of a universe with no void around it, is that it does not expand. It stretches. And if spacetime stretches, everything grows in size. Including matter. Particles do not change charge or size. If they did, we would be able to see it. So there must be a void out there! Link to comment Share on other sites More sharing options...
Strange Posted April 30, 2019 Share Posted April 30, 2019 There is no "void" outside the universe - if there were, it would just be part of the universe! The universe (in current models) has no edge or boundary. There are basically two possibilities: either the universe isn infinite (in which case it has no boundary, by definition) or it is finite but unbounded. The usual analogy for that is to consider just two dimensions and imagine the surface of a sphere: it has a finite area but it has no edge; if you travel far enough, you end up back where you started. If the word "stretches" helps you imaging that, then use that. I find it easier to think of it as the average density of matter in the universe decreasing. Link to comment Share on other sites More sharing options...
QuantumT Posted April 30, 2019 Author Share Posted April 30, 2019 1 hour ago, Strange said: There is no "void" outside the universe - if there were, it would just be part of the universe! So that is considered the difference between infinity and finity? Link to comment Share on other sites More sharing options...
FreeWill Posted May 1, 2019 Share Posted May 1, 2019 (edited) 10 hours ago, Strange said: There is no "void" outside the universe - if there were, it would just be part of the universe! It is not easy to exclude the existence of energy and matter free evolving space-time around the space-time with energy and matter, but for sure that if such a structure would exist it would be part of the Universe and regulated by the Laws of Nature. 9 hours ago, QuantumT said: So that is considered the difference between infinity and finity? You can Not have an absolute infinity if the system has a recognisable beginning, because the system (space-time included) will evolve for an exact amount of time; giving an exact size for the system, independent from any observer. The finity of the Universe make any observation possible in it. Edited May 1, 2019 by FreeWill Link to comment Share on other sites More sharing options...
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