# The Universe - infinite or not ?

by drag
Tags: infinite, universe
 P: 683 Are you sure that's not just an accelerating universe?
P: n/a
 Originally posted by JamesBell Olivers bells thesis 201 says that a universe can not expand without stretching and bursting causing a catastrophic wave of death and destruction of neutrinos and protons, the force of the rip will be 1.000000000000000000000000000000000000000000000000000000000000000000000 00000000000000000000000000000000000000000000000000000000000000000000000 00000000000000000000000000000000000000000000000000000000000000000000000 00000000000000000000000000000000000000000000000000000000000000000000000 00000000000000000000000000000000000000000000000000000000000000000000000 000000000000000000000000000000000000000000000000000001*10Exp

P: 3,714
 Originally posted by CJames I agree with Eh, although not necessarily in the way he explained it. To me it is much simpler. An infinite number is not "the biggest number possible." An infinite number, actually, has an infinite amount of room to grow. You can add, divide, multiply infinities together and you get back another infinite number. If you didn't, you'd get all sorts of paradoxes in mathematics. Mentat, by saying an infinite universe can't get any bigger, you are saying an infinite universe has no more room to grow. You are implying that the universe has to have space to grow into. You know that is not the case.
No, I never said that it was because it didn't have room to grow into. I said that it was because it was as big as it could possibly get.
P: 3,714
 Originally posted by MajinVegeta The universe(universe=everything) is infinite, but the spacial demensions are the ones expanding into the actual universe. It's like, what is the universe expanding into? Well, lets substitute "universe" as "subuniverse". So it's what is the subuniverse expanding into? the actual universe. I hope you understand what I mean(as I am having a hard time describing this).[a)] [:))]
This is very near (if not identical) to one of the BB theories, that people bring up quite a bit, especially in threads about the incompatibility of infinite universe with BB theory.
P: 3,714
 Originally posted by Eh The important thing seems to be that expansion does not necessarily make the universe larger. This is one of the weird things you get from infinity, but it does not seem to have an inherent problem. As you noted before, each region in an infinite universe is infinitesimal compared to space as a whole. That is, each point is pretty much zero compared to the universe. Within any region, local expansion occurs where distances between points increases. But even though local expansion is occuring within the region, the size of that region is infintely small compared to the whole universe - and always will be. There is nothing preventing local expansion from occuring, and the size of the universe never changes. Again, this is because of the nature of infinity.
I understand all of this, I was talking about the idea that the spacial dimensions themselves are expanding. I had thought that this is what BB theory was all about. If this were the case, then the universe could not be infinite.
 P: 3,714 CJames, infinity is not the biggest that you can get mathematically. But is the biggest that you can get physically.
 P: 1 you gotta think outside the box man. like the universe can grow and grow. but like, what is it growing in? yknoe, what outside this box man, is the universe square? and outside of each wall is there an equal and opposite universe, or if its a circle, it wouldnt matter if you left te universe and looked at it because it wouldnt be there, you would be in a place where time and space didnt exist until you got there, and you would float forever thinking until you turned into your own universe, and you were the creator man. i swear i dont knoe what im talking about man. lmao.
 P: 2 The universe is not infinite nothing is naturally infinite we only see the universe as infinite because we are so small compared to it and we really dont know where it ends but it does have an end and wont expand forever because like all things it will eventually run out of energy. Space may be infinite but the universe is not.Now whether it will just stop or collapse in on itself is another thing maybe it will collapse and just create another big bang or just stop and for whats outside the universe it could be nothing or it could be another universe how do we know that there wasnt a universe when the big bang happened and that the force from the big bang didnt push that universe out of the way or push or destroy part of that universe so our universe could form but our universe could just be a galaxy or a planet in an even bigger universe if you get what i mean but yes the universe does have an end and it is not infinite.
 P: 4 the universe is not infinite because it is currently thought that the universe is expanding but we could have an infinite number of parallel universes.......................but also the earth was flat at one time and every planet was manipulated by earth's gravitational force???
P: 20
 Quote by RuroumiKenshin The universe(universe=everything) is infinite, but the spacial demensions are the ones expanding into the actual universe. It's like, what is the universe expanding into? Well, lets substitute "universe" as "subuniverse". So it's what is the subuniverse expanding into? the actual universe. I hope you understand what I mean(as I am having a hard time describing this).[a)] [:))]
I think i do. So there is a "wall" at the edge of the universe.... say the expansion of matter is the only definition of this wall. It has more room but no stuff. The expanding universe continues on its path, I would guess dispersing at its edges more and more. But even on the outer limits of what could physically hold together we could not tell there is nothing there because there is nothing to mark its presence, other than nothing.

So say one day we could count the physical universe on any level I think we would have to call that infinite (even being quantifiable) because we have no words in any language to describe it.... Just like a Dodo first seeing things that could eat them, how could they tell there birdbrained friends that didn't see the other colony that got slaughtered anything about what happened when so many words are missing.

Well kind of went off on a different direction... sorry, it happens.
P: 20
 Quote by dad3 .......but also the earth was flat at one time and every planet was manipulated by earth's gravitational force???
We think too much of ourselves. That was destruction and undeniable forces that brought us back there. And our way too "I'm better than you" mentality that keeps us there. IMnotsoHO if we weren't so good at those traits our species would be either way more primitive or as my optimism likes to think way more developed than it is today. Maybe not the same, but more.

When did a people invent the printing press? Columbus proved it was round right? Hell we didn't even know an apple falling from above you would hit you on the head until after the guy who once again proved the basics of what is was told to shut up or die. We are a bit full of ourselves, maybe not a bunch of you all, but I would be tempted to say a majority of all of us peoples.
P: 177
 Quote by dad3 the universe is not infinite because it is currently thought that the universe is expanding but we could have an infinite number of parallel universes.......................but also the earth was flat at one time and every planet was manipulated by earth's gravitational force???
The best model of the universe found so far indicates that the universe is at least extremely large, perhaps infinite (since the total density of the universe is near that which would make it flat and therefore infinite). Expansion is a matter of geometry, if one imagines a flat infinite 2-d plane on which figures are drawn, expansion of the plane would lead to every measurable distance increasing (according to rulers that do not change in size with the expansion), so the figures would enlarge into (geometrically) similar ones.
 Quote by jposs So there is a "wall" at the edge of the universe....
There is no edge of the universe (on this point it doesn't matter whether the universe is finite or infinite). In order to have an edge the universe would have to behave differently from what is observed (for instance, general relativity (among many other things) wouldn't work since the universe would not be representable as differentiable manifold near the edge).

Off topic (and irrelevant): This may be the first time I've seen a thread from 2003 necroposted (though I guess it was also posted to in 2009, but that was also a necropost, and it lead to no discussion so I don't think it counts).
P: 4
 Quote by jposs We think too much of ourselves.
Exactly
 P: 132 I do not see how the universe or the multiverse can be finite. It is a all or nothing situation. Nothing can't co exist with something. If you say the universe started with the big bang then how long was this tiny super dense singularity sitting there for before the bb? If you say the universe if spacialy finite then what would happen if you reached the end? The fact that we exist means time and space are both infinite.
 PF Patron Sci Advisor P: 8,897 I would argue that proposal, binbots. Nothing exists amongst something all around us - like empty space between stars. It is difficult to prove the universe is either finite or infinite. Einstein surely thought it was infinite and I'm not inclined to argue with him. But, his logic was newtonian and he waffled a lot. WMAP suggests the universe is almost exactly flat - which implies it is infinite, or at least too close to call. What does that mean? A universe comprised of a finite amount of matter expanding into an endless void? An infinite amount of matter expanding into an even more endless void? The only relevant part, IMO, is the observable universe. Beyond that is the playground of mathematicians and philosophers - who remind us why our ancestors found theology appealing.
 P: 41 I believe the universe is finite. Richard Feynman's law of "alternative histories" states that each incidents happens in a different way in a different universe. If our universe was infinite, how could there be many universes. I believe that the size of a universe is finite, but the number of universes is infinite. Besides, ever since the big bang, the space between celestial objects has been increasing. Only finite things can increase in size.
P: 533
 Quote by mdmaaz I believe the universe is finite. Richard Feynman's law of "alternative histories" states that each incidents happens in a different way in a different universe. If our universe was infinite, how could there be many universes. I believe that the size of a universe is finite, but the number of universes is infinite. Besides, ever since the big bang, the space between celestial objects has been increasing. Only finite things can increase in size.
The last part wasn't exactly true. If you start with the set of integer which is infinite, you map each element to twice their size i.e. n maps to 2n, then the two sets have the same cardinality, although distance between each integer is now twice as before. So when we say the universe is expanding, all we are saying is the the scale factor of the metric changes, in much the same way as "expanding" the set of integers. Thus an infinite space can expand in such a way. That said, I personally prefer a finite universe ;-)
 P: 132 There is room for our infinite universe with other infinite universe. There is infinite room in infinity. I think the question is how is our universe infinite. Are we inside a larger universe etc etc? Is our own universe apart of infinite space? Or are there infinite parellel universes. Either way it is all infinite. It is the same on the small scale. No matter how small we go we will always ask: well what is that made of? The answer to the questions of the universe is that there will always be more questions forever................................

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