elephant03
Do you think that Universe is Infinite in size or do you think that is had an end to it's space and time? I know that there is millions and billions of galaxies in our universe. Do you think there is only one universe or many?

Do you think the Universe has a end to space?elephant03
Do you think that Universe is Infinite in size or do you think that is had an end to it's space and time? I know that there is millions and billions of galaxies in our universe. Do you think there is only one universe or many?
ocalhoun
I think the universe either goes on infinitely, or if it does have limits, is a 3D surface of a 4thD hypersphere (or other hypershape), so it would start over again at the end.
Especially in the latter scenario, it is (relatively) easy to imagine that there could be many such universecontaining hyperspheres, either sitting next to each other, or nested within each other, or both. Bikerman
The universe is finite but unbounded. We cannot say whether there are other universes outside our own  some think so, others do not. Without the ability to test such a hypothesis it is speculation, not science.
My own speculation is that Lee Smolin might be onto something. I find the idea of universes 'evolving' intellectually satisfying. That does not, of course, mean that it is correct  it doesn't even make it likely. LotusNegra
When Einstein created general relativity theory, the space was supposed to be curve near mass. But supposing space is infinite and very very far there are no mass, in there the space should be linear again. But that violates some general relativity's laws. Einstein's solution was to make the entire universe curve, and eventually it would touch the other side, so it was no more infinite.
So, a finite universe is just a hypotesis to validate Einstein's theory, and while experiments prove that it is correct, the hypotesis are assumed to be correct to. That's how physics work. DoctorBeaver
My belief is that we (meaning our universe) is on a 3dimensional (plus 1 of time) brane in a higherdimensional cosmos.
Mass and energy cause curvature of spacetime. At the furthest limits we can see, space still appears flat. But we have no way of knowing what is beyond the range of our vision. There may well be enough energy and mass in the universe to cause it to curve back on itself  to be "closed". Not only could our brane be curved, but the higherdimensional cosmos could, and probably would, also be curved or warped. At 1 time it was thought that measuring the rate of expansion of the universe would answer the open/closed question. Measuring the rate would enable us to calculate the total mass/energy and, hence, work out whether it is open or closed. However, the accelerated rate of expansion has rather thrown a spanner in the works there and made things a lot more complicated. Dark matter serves only to further complicate the issue. We need to measure the amount of force that is driving the expansion before we can calculate what the expansion rate would be without it. As that force is so miniscule, that is a bit tricky to say the least. It is possible that the figure is down near the Planck scale and hence beyond anything we could ever actually measure empirically. _AVG_
The Universe is so large that it's size cannot be measured ... plus, if one assumes that it is expanding, then how can the space have any kind of boundary?
Thus, in short, there is no limit to the space in the universe neither is there any limit to time. Also, there could be more than one Universe ... Multiverse? ocalhoun
That makes no sense at all. What is the largest thing that can be measured then? 8166UY
It's indeed strange to say it can't be measured if it has a size. I think it has no size and goes on for infinity. A big nothing makes no sense and a lot of things learn that things repeat in nature. So I'd go for an approach which displays it like particles which always have a bigger contrain. So I expect that the omniverses circle around each other and make new flocks together.
Bikerman
Consider the 2D surface of a balloon. Clearly it has a size. If you were on that surface then where would the 'edges' be?
DoctorBeaver
Round the bit you blow into! Bikerman
There's always one isn't there Georgeboy
I can not believe that the Universe would be finite. Suppose that there is a possibility to reach the end... You go to there and what would you try to do, or what would I try to do...? Yes, I would like to know what is behind that border. If there is a massive construction, you can again ask yourself; "hmmm, how thick would this massive construction be?"... This should be again a big question and thereafter you can ask what will be the next part?
Pure mathematically I would say infinite. There will be always a possibility to add another mile. But the border with finite but unbounded is quite close to it. It seems to be a very little difference. DoctorBeaver
And it's usually me DoctorBeaver
I don't like infinities. In any case, if the Big Bang theory is correct (and it certainly seems to be the best candidate) then the universe cannot be infinite. It cannot be infinite if it is expanding. An expanding infinity is an impossibility.
However, it is possible that there is no edge. Space could be curved or warped to such an extent that travelling far enough in a straight line will bring you back to your origin; similar to travelling around the inner surface of an expanding sphere. I like that idea as it does away with all those nasty infinities. poppat
I think you are all thinking like humans with our limited knowledge and I think there is an aspect to dimension that we dont yet understand. I don't think that I know enough to really contibute to this forum properly, but I still believe that what we know is only a tiny snippet of all that there is to know. I think there is more that is beyond human science and way beyond religion and if people keep on talking to each other we will get it in the end.
poppat profbis
May be we are like cell in a human body compared to universe. There are millions of cell, and each cell has millions of micro organism. May be our galaxy is like one of the cell of the universe and there are millions of other galaxies. Conclusion: We are not smart enough to conclude the answer yet.
ocalhoun
Not so much, really. Look at geometry: A circle is all of the points (which each have 0 size) that are a certain distance away from a single point on a 2D plane. There are an infinite number of points along the curved line that makes up the circle. But, consider this: both a small circle o and a big circle O have infinite points, but the larger circle could be twice the perimeter of the small, and therefore have twice as many points around it. (infinity x 2) Now, just imagine a circle with a constantly growing diameter; now you have an expanding infinity. (The number of points on the expanding circle.) Drathan
Lol, my thoughts.. (not really thought but something i was thinking that would be funny) Ok, say you took an infinite tape measure.. and stretched it out for eternity, if the universe was infinite, you would never see it again. If it were finite, You would hit your back (and probably say, "Oh i was getting a bit itchy.")
Battle_Off
I really have no idea, but if the is an 'edge' of the univers, I'd love to go there, what would you see?
Wouold you see a wall which you just can't get past? like in pc games where you are just walking against a wall, but not going anywhere. ocalhoun
More likely, it would be just like the edge of the Earth. For a long time explorers looked forward to (or feared) finding the edge of the Earth, but as it turns out, it is round, so if you go far enough you just end up where you started. It is possible that the universe is the same way. Just like how the old explorers never found the edge of a 2D Earth because it curved in the third dimension, space explorers may never find the edge of the 3D universe because it curves in the fourth dimension. *has epiphany* And perhaps if you could travel in that fourth dimension far enough, you'd end up where you started because of a curve in the 5th dimension, and so on for higher and higher dimensions! Of course, there's no evidence for that at all, but that theory does seem to have a nice symmetry to it, and it would fit in nicely to the semifractal nature of the observable universe. DoctorBeaver
I appreciate that there are various mathematical infinities. But if the points on the circle were infinitely small, you'd have the same amount on each. In any case, I was talking about an infinite size. If something is infinite in size, it cannot get any bigger as that would infer it was not infinite in the first place. ocalhoun
Partly it would depend on how you define the universe. If our universe is the 3D surface of a hypersphere, and we were somehow able to discover other similar hyperspheres all around it, would these new discoveries be part of 'the universe' or not? If they are part of the universe, then the universe is probably infinite. If you consider those other spheres to be other universes, then it is finite.
DoctorBeaver
If you take the view that "universe" means "everything there is", then if there are multiple hyperspheres, they are part of it. But that still does not mean the universe is infinite. Your argument is akin to saying that if there is only 1 ball in a sandpit, it is finite but if there are many then it is infinite. Clearly, that is a specious argument. In any case, regardless of what may or may not be in it, an infinite universe cannot, by definition, get any larger. As I said, if it gets larger then it was not infinite to start with. One also has to be careful to distinguish between infinite and boundless. Just because something doesn't have a boundary doesn't mean it is infinite. The balloon analogy demonstrates that well. ocalhoun
It is infinite in the sense that if you traveled outside of the 'sandpit', then the universe would 'stretch' to accommodate you as you got further away. Since it includes everything, you cannot find the edge of it, because when you get there, the edge becomes defined by you. DoctorBeaver
If you cannot find the edge of the universe, how can you get there? I believe the universe is closed but boundless  akin to the surface of a balloon. You can travel as far as you like in any direction but you will not find a boundary. You will eventually return to your point of origin due to the curvature. welshsteve
I'm no expert but my opinion is there is an end, but the universe is expanding all the time, and nothing can leave anywhere within it fast enough to catch up the edges.
Eventually, it will implode on itself deanhills
I did some Web searches, as this question really made me think and is probably going to stay with me for a while. The following argument looked interesting to me (http://curious.astro.cornell.edu/question.php?number=166):
Bikerman
I'm trying to stay out of this debate for a while since it seems to me that you are, by degrees, getting to grips with the problem without my intervention (not that I am some 'guru' here, but this is a problem I've devoted some time to).
disvi3tphong
i would say this is a very interesting question/topic
my assumption..i think it's infinitely endless. =] aw man..now i'm really thinking about it and it just fascinates me pll
I think that universe goes far.... but maybe it's not as big as we think.
During a long time people thought that when you arrived at some place on the earth (the end of the earth) you were falling into nothing. Until they discovered all the rest of our planet. I think it's same here, now we think it's really big but... Maybe we only need to discover it. It's too bad we can't fly at the speed of light. SonLight
How big do you think it is? Telescopic evidence suggests that it extends to 20 billion light years, give or take a factor of two. Some theories suggest it's a lot bigger, but we can never see all of it. In my opinion, 10 billion light years across is "big" already  it really doesn't matter much to us whether it's a lot bigger than that.
Surely, if we discover "the rest of the universe" it will prove to be larger than the part we know about today.
Besides speed, we would need 20 billion years or so to take a good look around. I prefer to let our telescopes do the walking, even though it means we can only see faraway things as they were a long time ago. Perhaps the cosmological background radiation is analogous to the place where people used to think you would fall off the edge of the Earth. Science seems to assume there is a boundary there at the "big bang" that we have no possibility of ever reaching beyond. Perhaps that limit will eventually fall, but it is unimaginable how it could. ocalhoun
A good analogy. I suspect someday that people will think of the idea of there being an end to the universe as being just as silly as we think of the idea that you could fall off of the edge of the Earth. deanhills
Thanks Chris. Would have been nice to learn about it as a "problem". How did you come to devote a lot of time to it? Think I understand though that it could potentially take up the space equal to the Universe to outline the problem Bikerman
Well, I devoted some time to it when trying to plough my way through General Relativity. The geometry of space and time is something that emerges from the equations of GR, though the answer to 'what shape is the universe' is still unresolved. It is obviously 'flat' on a small scale and this brings up the first major problem in discussing this matter  local geometry vs global geometry. We can make sensible statements about the local (observable) universe and the geometry of it, but we can only speculate about the global geometry (the 'shape' of the entire universe) since much of it cannot be observed by any method. When we are talking about the local geometry, what we mean, essentially, is does Pythagoras' theorem work or not? (ie do the angles of a triangle sum to 180 degrees)? Now, if space is flat then the laws of Euclidean geometry say that the answer is yes. If, however, space is warped or bent then the answer is no. We can use the symbol omega to represent the curvature of space. If omega = 1 then space is flat and pythagoras' theorem holds. If omega>1 then space is curved into a spheroid and the angles of a triangle sum to > 180. If omega <1 then space is 'saddle shaped' and the angles of a triangle sum to < 180. Now, obviously at very small scales then space is pretty flat so we need to draw really big triangles to test this. This is nicely illustrated by the wiki diagram: deanhills
Thanks Chris. I think I can understand now what you mean. Think I need to take a course in this before I can understand the calculations though. I can understand the basics, but as you say, one would have had to struggle with this for a very long time to be able to debate meaningfully about it. Related topics
