I know we can only travel so far due to humans, but if we could travel forever in the universe, what would be outside the universe if anything?
202521
As far as we know, the only "wall" is the event horizon of the observable universe, the events beyond it from our point of observation are too far away to have their light reach us given the age of the universe. This "wall" of observation is approximately spherical (mod the local curvature) and is continually expanding at the speed of light. Every observation point in the universe has its own event horizon/observable universe.\nOtherwise, there is no evidence to think that the universe is anything but infinite. Recent observations of the cosmic microwave background give us information that the cosmology of the universe is flat, ie. planar. This does not tell us whether the universe is compact or not. The only other types of cosmologies that agreed with Einstein's equations were spherical and hyperbolic.\nFor more information, see the source.
578921
My opinion through many meditative thoughts:\n\nI believe our universe exists as a point in what you call 'the void'. A point having the geometric meaning of no volume, dimensionless.\n\nI believe what you are considering the void is what I call space. Our universe is what we can view, touch and explain through science we have developed. Space on the other hand is an infinitely dimensional medium, in which our universe was born. \n\nOur universe is nothing more than a 'disturbance' in space, and in space our universe exists as a point. This point is a fraction of infinity, yet everything is a fraction of infinity. So in the humble realization that we are nothing (a fraction of infinity), we realize we are equal to everything we can fathom, as it too is a fraction of infinity no matter how large.\n\nSo, through the realization that we are nothing comes the discovery that we can be equal to as much as we can fathom. \n\nI believe this means everything that makes up the universe and space has its own existence or presence known to space and must exist.  This existence holds true for our universe and what we would consider other universes. The disappearance, or non-existance of any defined object and its position in space no matter how small, down to a point, would truly have mind boggling consequences. \n\nIf time travel is possible than there must be alternate universes, as we know it.  It is a deadening thought to ponder.  Almost pointless until we figure out gravity, which I believe will open the door to all other understandings.
613182
The Universe itself doesn't necessarily need something to hold it together, it just is.  \n\nAs far as what's outside the Universe, science cannot answer that question, so it is left to speculation.\n\nMy opinion: the Universe exists within the realm of God, so the spiritual world is outside of it, but that is just an opinion, not fact!
114017
The universe is said to be expanding,at least in the sense\nthat all of the galaxies are supposed to be drifting farther\naway from each other.That would seem to contradict your notion of a tremendously big circle as there's no gravitational pull binding them together.\n Also,if space is finite...then what's outside the boundaries?
584303
Great question!  Space goes on forever - outwards.  HOWEVER, we don't think of ourselves as being "in space" while we are on Earth, so we could argue that there is a distance around the earth that, for the purposes of colloquial conversation, is not space.  Where does earth end and space begin?  Maybe at the minimum height for an unpowered stable orbit?
127324
Supposedly, we can only see just a small fraction of our universe.  With some many places, the odds are pretty good that there exists life somewhere else in the universe.\n\nHowever, with those odds, the chance of us finding them is almost zero.  Humans have existed for almost no time at all compared to the life of the universe, so the chance that another life form exists at this exact moment in time is very small.\n\nWith the large universe, somehow one of us would have to get interstellar travel.  But the chance of one of us randomly bumping into each other is very small because the universe is that large.\n\nAlso, who says other life forms want to expand to other places.  Maybe both of us will just be happy living on one planet and staying there until the life form goes extinct.\n\nThe only way we could prove any of these theories is to actually find other life, but given the above, the chance of that is almost zero.\n\nAll that said, I think there is/was life out there, but I don't think we'll ever find it.  Maybe they made it to Type I and self-destructed like we might. :)
91879
*Edit2*\nBe careful! Most people that have replied to this question have obvious lack of knowledge in quantum field theory, relativity, cosmology, string theory and particle physics. I don't know where they get their facts from, but they are outdated and don't contain any correct information from ANY of the five fields I listed above. They do sound very matter-of-fact though. At least go to that www.superstringtheory.com website to see for yourself who is right and who is wrong.\n\nWhat you have loosely described is called the horizon problem. It was a huge problem for cosmologists and physics theorists to solve, and all the answers aren't quite in place yet, but I'll give you the jist and you can visit that website I mentioned to get the real goods on exactly why and how we know what we know.\n\nThe "big bang" was actually not an explosion, it was a rapid expansion, like a balloon being inflated. The universe started out as nothing but a seemingly empty vacuum that expanded so fast it released a whole lot of energy. This energy started out as extremely hot radiation that cooled into particles like quarks and gluons. These quarks and gluons then came together to form protons which then cooled further and formed atomic matter, which we are all familiar with (except for religious folk who don't want to think very hard, they like simple, three-word answers that start with "G" and require no thought).\n\nThe horizon problem, kind of like what you described, is that light can only travel at a fixed speed, but the universe is huge (over 50 billion light years across) and has NOT existed long enough to allow light to travel from one side to the other (the oldest light we see has travelled 40 billion light years even though the universe is only 14.5 billion years old - the discrepancy is due to expansion). In fact, it is unlikely that light from one side of the universe will ever reach the other side because the universe is expanding faster than the speed of light. \n\nWhat inflation also did is almost instantly expand the matter that now makes up the Earth so far away from the matter making up those early galaxies that the light from them is only just reaching us today. The light takes even longer to reach us than the distance to the galaxies because we are moving away from those galaxies faster than the speed of light. You might think this means the light would never reach us but this is not true because as the photon travels towards us, the expansion rate of the part of the universe it is traveling through gets slower and slower relative to us until the photon's speed is greater than the expansion speed and it zooms to us. Thus the galaxy might have started out only a few billion light years away but the expansion caused the photon to take 10 billion years to get to us, so we see these galaxies as they were 10 billion years ago.\n\nAs for the rest of the horizon problem: Studies of the cosmic background radiation show that the entire universe was isotropic in the beginning (that means it was almost the same everywhere). The cosmic background radiation is almost like a giant cast of the universe - it shows the shape and contours of many different properties of the universe when it was only about half a million years old. Anyways in order for the universe to be the same everywhere, it means the particles had to be all interacting with each other over a short distance, and inflation explains this very well. It makes the universe and all matter in it small enough that all matter is initially able to interact before being blown all outward in 3 dimensions like a balloon.\n\n*Edit*\nI just want to add that the universe is ~14.5 billion years old and the Earth is not travelling at the speed of light relative to spacetime, we zip around our galaxy at a few hundred kilometers a second and our galaxy whips around its cluster at an even greater speed, but not even close to the speed of light.
255034
In spite of what some yo-yo answered, the universe IS expanding, but whether or not it's expanding inside something else is absolutely and totally unknown. In the far distant future our science might have progressed to a point where we'll have the means to answer that question. Instead of driving yourself goofy over wondering what our universe is inside of, best to just try and imagine an absolute and infinite void totally without space, time, energy, mass, or anything else.
130702
how do you understand anything?  We can't understand everything there are things beyond our comprehension.  Try to think about this, does space end?  Is it infinte?  what is infinite?  You kno?
88101
Nah, there's nothing out there. It would take too long to travel to any of the planets. By the time I got to Jupiter I would be wearing diapers and being fed Geritol through an IV everyday.
191954
There is no way for us to know since we are defined by our own universe.  There does not need to be a substance outside of our universe for it to expand.  A substance would slow us down.\n\nThe most popular theories for what lies beyond our universe are nothing (nothing to us anyway, it would be nothing of this universe so we certainly wouldn't recognize it), and other universes.  But explaining multiple universes gets complex and it's hard to decide if they are more like bubbles or like russian matryoshka dolls.
134026
Space is very vast and the distances are in the order of millions of light years to the farthest reaches of the universe. Even if we learn to travel at the speed of light, it will be impossible to travel for millions of years for one person or one generation. Some have proposed that there may be holes in the fabric of space-time which would enable us to reach such places without going throught the distance in between. This remains to be proven.
598300
If all matter is over 90% empty space, then there should theoretically be small vacuums throughout the entire universe.  However, such a vacuum would be impossible to detect, contain, or sustain.\n\nPerhaps beyond the edge of the universe, a perfect vacuum exists.  All the matter/energy ever can only take up so much space.  However, there is no way to observe or reach that vacuum either.\n\nMmmm... uncertainty!
424853
We can only see the universe out to our horizon (essentially the distance of cosmic microwave background radiation about 13.7 billion light years away).  The size of the rest of the universe can't really be known.  Some cosmologies make our corner of the universe as a "pocket universe" in a much larger multiverse where physical constants (and so the behavior of so called physical laws) vary over unfathomable distances with little universes peppered throughout it.  So, we can't really say how big it is, only how big the portion we can actually see is.\n\nHere is a little summary in a review of a fun book:\nhttp://www.theosophy-nw.org/theosnw/science/sc-imo17.htm\n\nThis Science article would be a good read too.  Any university library will have a subscription and a good public library will too, or you can buy the article online. \nhttp://www.sciencemag.org/cgi/content/summary/309/5737/1022\n\nWith the universe so large, I think it highly unlikely that life did not evolve elsewhere, especially considering how quickly it seems to have arisen on Earth.  Intelligent life is another story and much harder to address.  A great book about life written for non-science major college students is "Life in the Universe" by Jefferey Bennett et al. Get it used, or maybe for Christmas.  With some effort it is accessible even to a junior high school student.\n\nhttp://www.amazon.com/Life-Universe-Jeffrey-Bennett/dp/0805385770/sr=1-8/qid=1163518785/ref=sr_1_8/102-7735916-8685767?ie=UTF8&s=books
647121
If there was just nothing, we would never know what could happen because we wouldnt exist.\nI believe there is more out there in the universe than what we know of.\nWether we discover these things or not is hard to ever say.
580182
It is quite possible for the universe to be both finite and without a boundary. No wall, but still it doesn't go on forever. Here's a way of visualizing it. Imagine that nomatter which direction you choose, you will eventually get back to your starting point if you go far enough in a 'straight' line. Impossible? Free your mind. It happens in two dimensions on the surface of a sphere. While it currently looks like the universe really is infinite, such three dimensional spheres were models used for finite universes until the data showed they are probably wrong.
445132
Hi!\nI also think that it is impossible for humans to be alone in this vast Universe ....\nIn fact I believe there are some primitive civilizations here in our galaxy at approximately 31000 light years away, some antique civilizations at 3,1 millions light years away, an evolved civilization at approximately 100 million light years and that in the Universe could exist some 3000 "super - societies" and at least 300000 similar to ours in terms of technical evolution. Still there is that old problem: if they exist, why we didn't manage to "get in touch? After all, this "is" the main objective of S.E.T.I and so far ...nothing.\nThere are some explanations for all this - great distances which actually limits the possibilities of a "radio communication",  the great consumption of energy in order for such a long travel to became possible even in an unconventional way (such us      teleportation) and the  ultimate barrier - speed of light....\nIs there life out there?..... As the "Drake'" equation shows, the probability is very high (there isn't a connection between the figures I wrote earlier and the Drake equation).In the end we simply can not prove anything related to this issue but I guess that questions like this makes life is so interesting