when universe contains everything,why do they say universe expands like a balloon?what's beyond the balloon?
79119
Our universe has 4 dimensions of space-time, and the domain of these domains is finite.  However, the expansion of that is in a larger dimensional space--meaning more than our four dimensions, with higher dimensions orthogonal to our four.\n\nThink of the 2-D surface of a balloon.  If you were a 2-D being on the surface on that balloon, you'd have no concept of the 3-D space inside and outside the balloon--your entire existence wouldbe contained on that 2-D surface.  But if the balloon inflated, you 2-D reality would grow in the context of the larger 3-D reality which was beyond you.
275416
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?
188759
There are a number of possible answers, and the subject is still being researched both by using theoretical arguments and  by looking for clues in the data we can gather from peering deep into space.   You're not crazy for asking questions like this, or, if you are, you're at least in good company.  These sorts of questions are the bread and butter of a subdiscipline of physics called cosmology.   \n\nOne common theory is the big bang theory, as others have mentioned.  This has had to be modified in a number of ways over the years as more data comes in, but many basic elements of the idea remain valid.  One is the idea that since were talking about an expansion of spacetime, there is no center to the expansion, or, alternatively, all points are equally the center.  This is hard to imagine in three dimensions, but it's easy if you consider only two.  Imagine you have a mathematically perfect balloon, that is one that can be shrunk down to a single point, and expanded to any size, and it perfectly symmetric.  If you expand this balloon, is there any point on the two dimensional skin of the balloon which can be said to be the center of this expansion?  No, all points are moving away from each other equally.  There is a center, but it occurs in a higher gemoetric dimension that the one the skin of the balloon has, so it's effectively off the map.  Our universe is expanding in much the same way, only it's a three dimensional volume and not a two dimensional sheet.\n\nAs for what was there before...  This is a difficult one to answer since we have no method for peering back beyond the start of the universe, so we need to make guesses about this.  One possibility is that the universe has existed forever, and it's cyclic, expanding, and then collapsing, and rising again, and so on.  This was a popular early idea in big bang theory, but doesn't seem likely now.  As best we can tell from observational data there isn't enough mass to pull the universe back together, and so it's expected to continue expanding and cooling, and eventually this expansion, which is actually increasing in rate due to dark energy, will achieve such a high rate that matter will be pulled apart at the subatomic level, ending in something that has been called "the big rip".  But, even if this is the case, there are mechanisms by which our universe could be the offshoot of an earlier one.  Theoretical work in string theory suggests that if compressed to a high enough degree, matter can trigger a spontaneous exapnsion of spacetime, which generates more energy as "tension" in spacetime, which can then come into exsitence as additional matter.  Some calculations of the minimum mass needed to create a universe the size of ours through this process run as low as a few tens of kilograms.  So, black holes in an earlier universe, if large enough and dense enough, can expand into their own universe, one which is disconnected spatially from the earlier one, which may or may not have enough mass to collapse again, but local areas within it can collapse to a high enough density to start the process all over again.  So, rather than a single universe pulsing in and out of existence as in the earlier oscillatory model, this model suggests something that would be rather like a tree or bush growing and branching, with each branch being a universe, and each bud which produces a new offshoot being a black hole which spawns another universe on the opposite side of it.  One universe could give rise to a great many more, and while each one is finite in the time for which it exists, each one is a branch of limited length, the entire tangle of univereses has been going on forever.
441363
In addition to memac63's pretty good answer, intergalactic space and the entire universe is filled with other "things" that don't necessarily have any solidity -- dark energy (the mysterious force that's causing the universes's expansion rate to increase), gravity (its range is infinite), and something called the cosmic microwave background radiation which is the "afterglow" from the Big Bang.\n\nGod should be spelled B-I-G B-A-N-G\nPBrax@netscape.com
962950
This sort of question generates the highest percentage of false and meaningless responses of any other I know of in A&S forum. Here's the real poop. According to the BB model of the universe, the universe is expanding, but there is no boundary beyond which there is only empty space into which stars and galaxies are expanding into. This is a common misinterpretation due to a widespread inability to grasp the concept of curved space. On a large scale, every can consistently be presumed to be pretty much the same as it is in our neighborhood, although any conclusions about what lies beyond the observable universe are impossible. However, the volume of the universe may be either finite or infinite. This is simply not known. In General Relativity, finite *and* unbounded is not a contradiction.
558467
Is our universe in another universe?  \n\nBefore we can address that question, we must first define universe.  \n\nThe word universe denotes all space and everything (matter, energy) contained within it.  The prefix uni means one.  The root verse means word, carnate message, meaningful substance, matter.  Questions regarding our universe persist today.  Does it have a beginning and end, or does it go on forever and ever?  Is it linear or curved?  If it has limits of length or curvature, then what lies beyond the Universe?  If something lies beyond the Universe, then can’t we accurately call that the Universe?\n\nSome lay people and some scientists conceive of the universe as infinite space.  Others define the universe as finite, or limited (perhaps curved), space.  Still others incorporate the elements of matter and/or energy into their definition of the universe, as opposed to the space beyond matter and energy.\n\nGiven these concepts of our universe, some scientists conclude that the “totality of space could be infinite. Shrink an infinite space by an arbitrary amount, and it is still infinite. (Scientific American March 2005).”  \n\nAs to the notion that we live in an ever expanding universe, moving away from every other universe on the fabric of space-time, some scientists are careful to point out that “\nAndromeda, our nearest large galactic neighbor, is actually moving toward us, not away. Such exceptions arise because Hubble's law describes only the average behavior of galaxies (Scientific American March 2005).”\n\nIn accordance with your supposition that our universe is in another universe, “it has been hypothesized by some scientists that the universe may be part of a system of many other universes, known as the multiverse (http://en.wikipedia.org/wiki/Universe).” Modern astrophysicists talk about multiple "pocket" universes that branch off from one another.  Stephen Hawking points out that parallel pocket universes can have no effect on a real observer inside a single pocket, so, according to Hawking, they are theoretical baggage that should be eliminated from cosmology, the study of the origins of the universe.\n\nSome string theories define the universe as a three-dimensional space in an invisible space having more dimensions. This is, in essence, a universe within a universe.  Our zone, a “braneworld” could periodically bounce into another parallel braneworld.  This may create what would appear as a Big Bang from one perspective or a Big Bounce of alternating expanding and contracting universe from another perspective.  Such a cataclysmic event is thought to occur 300 billion years from now, resulting in the rearranging and creation of a new universe.\n\nIs our universe inside another universe?  Well, apparently the Men in Black had it right.  Our universe seems to be inside of something else, another universe, called the multiverse.\n\nSteve\n:-D
828819
Thats a question that physics is still trying to answer.  \nThere are 3 types of theories on how big the universe is and the shape of it.  It is either flat, meaning it will always be this large and continue forever.  There is the closed ellipse type, meaning the universe started from something, but unfortunatly will end after its reaches its max capacity and starts to shrink again.  There is still the hyperbola theory meaning that the universe started at a finite point and is always expanding.
1106252
speaking in all logic terms all religon aside.  The universe always was it and it always will be here in one way or another.  But before the "big bang" the universe was smaller, much smaller infact than it was before this catastrophic event.  After the big bang everything that was once very very dense and all close together, is now moving apart from eachother at a considerable rate, leaving more and more area of what we call "space".
757860
One of the latest theories (not widely accepted) is that it was caused by the interaction of two other universes at the sub-atomic super-string level. This collision caused a catclysmic explosion at a  point of singularity, creating all the matter and energy we now have in our universe, which then began to expand and cool. \nSimple isn't it?\n\nAnother theory is that the universe is a state of perpetual pulsation. It expands, and then crashes in on itself to a singularity point, and then explodes again, this has been going on forever.\nEven simpler isn't it?\n\nThis could explain why so many people believe in God. It is simpler to understand. \n\nWhich theory you believe is up to you.
1048724
Before we can address that question, we must first define universe. \n\nThe word universe denotes all space and everything (matter, energy) contained within it. The prefix uni means one. The root verse means word, carnate message, meaningful substance, matter. Questions regarding our universe persist today. Does it have a beginning and end, or does it go on forever and ever? Is it linear or curved? If it has limits of length or curvature, then what lies beyond the Universe? If something lies beyond the Universe, then can’t we accurately call that the Universe?\n\nSome lay people and some scientists conceive of the universe as infinite space. Others define the universe as finite, or limited (perhaps curved), space. Still others incorporate the elements of matter and/or energy into their definition of the universe, as opposed to the space beyond matter and energy.\n\nGiven these concepts of our universe, some scientists conclude that the “totality of space could be infinite. Shrink an infinite space by an arbitrary amount, and it is still infinite. (Scientific American March 2005).” \n\nAs to the notion that we live in an ever expanding universe, moving away from every other universe on the fabric of space-time, some scientists are careful to point out that “\n\nAndromeda, our nearest large galactic neighbor, is actually moving toward us, not away. Such exceptions arise because Hubble's law describes only the average behavior of galaxies (Scientific American March 2005).”\n\nIn accordance with your supposition that our universe is in another universe, “it has been hypothesized by some scientists that the universe may be part of a system of many other universes, known as the multiverse (http://en.wikipedia.org/wiki/U... Modern astrophysicists talk about multiple "pocket" universes that branch off from one another. Stephen Hawking points out that parallel pocket universes can have no effect on a real observer inside a single pocket, so, according to Hawking, they are theoretical baggage that should be eliminated from cosmology, the study of the origins of the universe.\n\nSome string theories define the universe as a three-dimensional space in an invisible space having more dimensions. This is, in essence, a universe within a universe. Our zone, a “braneworld” could periodically bounce into another parallel braneworld. \n\nThis may create what would appear as a Big Bang from one perspective or a Big Bounce of alternating expanding and contracting universe from another perspective. Such a cataclysmic event is thought to occur 300 billion years from now, resulting in the rearranging and creation of a new universe.\n\nWhich is the end of expanding universe? That may be determined in 300 billion years, when it stops expanding (like a balloon). If any end exists, what will be behind this end? A multiverse void containing other expanding and contracting balloons, referred to as universes, may exist beyond our own.
514889
Outer space extends to the end of the universe. Further, the universe is constantly expanding. No-one knows if anything is beyond the end of the universe.
5808
Nobody really knows for sure.\n\nThere's a theory that the universe is expanding in a spherical shape and will continue to expand until it reaches maximum entropy. At that point all of the energy and matter in the universe will be equally distributed and the universe will no longer be able to support life.\n\nThere's another theory that the universe will expand (again, roughly in the shape of a sphere) until all of the galaxies exhaust their kinetic energy. At that point the universe will begin contracting. When the contracting is complete a singularity containing all of the mass in the universe will form and explode in a big bang.\n\nIf you think about it, if the latter theory is true then it's possible that the universe has expanded and collapsed an infinite number of times in the past!
737662
If you just want a short answer, I'll say this: if the universe is infinitely big, then the answer is simply that it isn't expanding into anything; instead, what is happening is that every region of the universe, every distance between every pair of galaxies, is being "stretched", but the overall size of the universe was infinitely big to begin with and continues to remain infinitely big as time goes on, so the universe's size doesn't change, and therefore it doesn't expand into anything. If, on the other hand, the universe has a finite size, then it may be legitimate to claim that there is something "outside of the universe" that the universe is expanding into. However, because we are, by definition, stuck within the space that makes up our universe and have no way to observe anything outside of it, this ceases to be a question that can be answered scientifically. So the answer in that case is that we really don't know what, if anything, the universe is expanding into.\n\nNow, for those of you who want a more comprehensive discussion:\n\nLet me begin by saying that "expanding" isn't really the best word to describe what is happening to the universe, although that is the word that is often used - a word choice which I think leads to a lot of unnecessary confusion regarding what is already a difficult topic! A more accurate word for what the universe is doing might be "stretching".\n\nThe difference between "expanding" and "stretching", for me at least, is that an "expanding universe" conjures up an image where there is a bunch of galaxies floating through space, all of which started at some center point and are now moving away from that point at very fast speeds. Therefore, the collection of galaxies (which we call the "universe") is expanding, and it is certainly fair to ask what it is expanding into.\n\nThe current theories of the universe, however, tell us that this is not the picture we should have in mind at all. Instead, the galaxies are in some sense stationary - they do not move through space the way that a ball moves through the air. The galaxies simply sit there. However, as time goes on, the space between the galaxies "stretches", sort of like what happens when you take a sheet of rubber and pull at it on both ends. Although the galaxies haven't moved through space at all, they get farther away from each other as time goes on because the space in between them has been stretched.\n\nOf course, when we think of space in everyday life, we don't think of it as something which is capable of stretching. Space, to us, just seems like something which is there, and which everything else in the universe exists within. But according to Einstein's theory of general relativity, space isn't really as simple as our common sense tells us. If we want to understand the actual way that the universe functions, we need to find some way to incorporate Einstein's ideas into our mental picture and imagine space as a more complicated entity which is capable of doing things like "bending" and "stretching".\n\nTo help us imagine this, a lot of people have come up with analogies for the universe in which space is represented by something more tangible. For example, there is the analogy with a sheet of rubber (or sometimes a balloon) that I mentioned above. My favorite analogy, though, involves imagining the universe as a gigantic blob of dough. Embedded in the dough are a bunch of raisins, spread throughout. The dough represents space, and the raisins represent the galaxies. (To the best of my knowledge, this analogy was originally proposed by Martin Gardner in his 1962 book Relativity for the Million.) We have no idea how big the dough is at this point - all we know is that it is very big, and we, sitting on some raisin somewhere inside it, are so far away from the "edge" that
1033786
this is actually a common misconception about the big bang.  the universe may be something like the two dimensional surface of a sphere.  it is finite yet has no boundary and no center.  nothing exists "outside" the universe.  to quote a dead writer, "there is no there, there".\n\nread this:\nhttp://www.sciam.com/print_version.cfm?articleID=0009F0CA-C523-1213-852383414B7F0147
533024
Is our universe in another universe?\n  \nBefore we can address that question, we must first define universe.  \n\nThe word universe denotes all space and everything (matter, energy) contained within it.  The prefix uni means one.  The root verse means word, carnate message, meaningful substance, matter.  Questions regarding our universe persist today.  Does it have a beginning and end, or does it go on forever and ever?  Is it linear or curved?  If it has limits of length or curvature, then what lies beyond the Universe?  If something lies beyond the Universe, then can’t we accurately call that the Universe?\n\nSome lay people and some scientists conceive of the universe as infinite space.  Others define the universe as finite, or limited (perhaps curved), space.  Still others incorporate the elements of matter and/or energy into their definition of the universe, as opposed to the space beyond matter and energy.\n\nGiven these concepts of our universe, some scientists conclude that the “totality of space could be infinite. Shrink an infinite space by an arbitrary amount, and it is still infinite. (Scientific American March 2005).”  \n\nAs to the notion that we live in an ever expanding universe, moving away from every other universe on the fabric of space-time, some scientists are careful to point out that “\nAndromeda, our nearest large galactic neighbor, is actually moving toward us, not away. Such exceptions arise because Hubble's law describes only the average behavior of galaxies (Scientific American March 2005).”\n\nIn accordance with your supposition that our universe is in another universe, “it has been hypothesized by some scientists that the universe may be part of a system of many other universes, known as the multiverse (http://en.wikipedia.org/wiki/Universe).” Modern astrophysicists talk about multiple "pocket" universes that branch off from one another.  Stephen Hawking points out that parallel pocket universes can have no effect on a real observer inside a single pocket, so, according to Hawking, they are theoretical baggage that should be eliminated from cosmology, the study of the origins of the universe.\n\nSome string theories define the universe as a three-dimensional space in an invisible space having more dimensions. This is, in essence, a universe within a universe.  Our zone, a “braneworld” could periodically bounce into another parallel braneworld.  This may create what would appear as a Big Bang from one perspective or a Big Bounce of alternating expanding and contracting universe from another perspective.  Such a cataclysmic event is thought to occur 300 billion years from now, resulting in the rearranging and creation of a new universe.\n\nIs our universe inside another universe?  Well, apparently the Men in Black had it right.  Our universe seems to be inside of something else, another universe, called the multiverse.\n\nSteve\n:-D
664286
the universe is expanding i do believe that cuz all the evidence our scientists have gathered over the yrs points in this direction. \n\n    as to where it is expanding, i guess u mean into what. well no one knows. we haven't been able to see what is at the end of the universe so we can't know what is beyond it. the notion of an endless universe is not right because then the big bang theory would have to be wrong. see, if the universe were endless then it would immediately imply that it had no beginning which has been proved wrong.\n  \n   so your question is pretty hard to answer directly. but if u look at it in another way then u can say that the universe is filling up some empty space just like water fills up a bucket slowly as u increase the level of water in it.
429563
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.