If the universe is constantly expanding, what is it expanding into?
816973
The answer is that it really isn't expanding into anything.  If you're confused, it's a kind of confusing idea.  Also, remember that almost by definition the universe is everything that exists, so to some extent it's meaningless to talk about what's "outside" the universe (of course, that stops no one from wondering... ;) ).\n\nOf course, that doesn't really help you much, so there's two examples, one of which is a really common one which leads to a misleading answer and one is the one I use when thinking of this issue which gives you a better idea.  The first and common one is to imagine/pretend that the universe is two-dimensional (e.g. you can move left or right or forward or backward, but up and down have no meaning), and specifically that the universe is the surface of a balloon.  Now, if put little stickers with galaxies on them on the balloon, and measure the distance between these stickers with a tape measure stretched along the surface of the balloon (the tape measure can't go through the balloon because the area inside the balloon isn't a part of our 2D universe) you have a universe.  Now blow into the balloon, causing it to expand.  The stickers on the balloons surface will stay attached to the points they were attached to, and the part of the balloon between all the stickers will expand, so that if you again take out your tape measure and measure the distances between the stickers, the distances will have increased.  This gives you an idea of how the universe (the 2D surface of the balloon) can be expanding.  However, in this case you can go, "Ah-ha!, but the balloon is expanding into the air", which makes you think that the real universe must be expanding into something.  This may even be part of why you asked the question.  But, as I said first, the universe basically by definition contains everything, so we have a contradiction.\n\nThis brings me to my second example, and the one I use.  Imagine that the universe is a two dimensional surface made of square bricks.  This surface is either infinite or has some chape such that it has no edges (it might be a sphere or what not).  Now, define the width of one of these bricks as some unit of length (a mile, a light-year, a million light-years, an inch, whatever).  Let's say one brick has a width of one light-year for the purpose of this discussion (but also note that you could make it correspond to, say, one billionth the width of an atomic nucleus or any other very, very small distance).  Now, let me again stress that a brick is one light-year wide (and hence has a square area of one square light-year or one light-year squared) *by definition*, and thus a brick in this example is *always* this size.\n\nNow, with that in mind, you could imagine putting galaxy stickers on random bricks (yes, I know a galaxy is thousands of light-years wide, but bear with me).  If you pick two such stickers, and count the number of bricks between them you get their distance, because each brick is one light-year wide, the distance between them.  Now, you let time pass, and as time passes rows and columns of bricks are inserted between existing rows and columns (and everytime you insert a row you also must insert a column and vice versa) in some mechanical, predicatable fashion.  Now, after some amount of time of this, you go back to the two stickers you picked and count the number of bricks between them, and you'll have found that the number has gone up, so that the distance between them has increased (because each block is defined as being one light year wide).  Now the stcikers never moved, they were always on the same brick, it's just that there are, as time passes, more bricks separating them.\n\nIf this seems like a hokey example, remember that we could make the bricks any size we like, including smaller than any particle or atom or whatever.  So, we change the example to make the bricks of a really, really small si
465735
The Universe is Expanding because it has been observed that the galaxies within the Universe are moving away from us at tremendouse speeds. The Doppler Effect explains the red shift observed through hundreds of telescopes which confirms the fact that the galaxies are moving away from us. If the Universe were not expanding, then the Galaxies would not be all moving away from us, but moving with us. The more perplexing question is if the Universe is expanding, then it is expanding into what?
187984
No one knows.  The universe is expanding at such an incredible rate that we'll never reach anywhere near the end of the universe and even if we could travel there at the speed of light we'd die of old age before getting anywhere near the end.
36543
As I understand it, the universe is in fact finite.  However, it's expansion is continuous and progresses at such a rate that we can not, with current technology, move beyond to see the end.
10073
The size of the universe in terms of length, width, height, time is in a state of flux. At any instant it may be expanding or contracting. The universe is generally accepted to be currently expanding. \n\nM Theory (the conglomeration of the 5 superstring theories) tells us that the universe is the result of, so called, “membranes” colliding in such a way that create a pocket of space which we call the universe. If M Theory is accurate, it is probable that there are many universes just as there are many planets, solar systems, and galaxies. \n\nFor more information:\nhttp://en.wikipedia.org/wiki/M_theory
1098923
There is an end to this universe.  But, it is constantly expanding and contracting.  Empty space is what lies outside of it.  The universe is encroaching into empty space.
122538
Currently the universe is expanding. However, we are not sure yet whats going to happen in the future. This is because it is possible that the universe will constantly keep on expanding as it is right now. Or it is also possible that the gravitational pull of the universe will be so huge that it will collapse under its own gravity. Right now, we are almost at a point of intersection between these 2 cases and in a few thousand years we'll know exactly where this is going. Ofcourse, you and I wont be around to witness that, but astronomically its a small amount time.
1099710
You are thinking 3 dimensionally. There is no center to the universe in 3 dimensions even though it IS expanding...
1035265
Which is the end of expanding universe? If any end exists, what will be behind this end?\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 “\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/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.  \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.\n\nSteve\n:-D
202004
I believe it does. The entire universe is a living creature that's expanding every day.
686202
Universe theories talk about a finite and unlimited Universe. The Universe is unlimited because it has no boundaries. There is no edge, no end where a spaceship would have to stop. See it as a tiny bug walking on the surface of a big balloon. The ballon has a finite dimension, but the bug will never find the end, so it is unlimited from the bug's point of view.\nSo, the Universe can be expanding or contracting or staying the same size. This is a very important question to answer in modern astronomy. Latest studies say that it is expanding, but it has not been totally proved.\nAnd where it is expanding? The Universe is creating more space and time where there is nothing.
5491
What you really mean to ask is, if the Universe is expanding, a phenomenon that by every conceivable standard of measurement and observation is universally (pun definitely intended) accepted by the scientific community to indeed be fact....\n\n...then what is the Universe exanding into????\n\nThe spooky thing is that no one knows. Science, with \nthe help of the Hubble Telescope has been able to see\nonly about 13 Billion light years out but the Universe itself is estimated to be about 14-15 Billion years old.\n\nThe universe is expanding into the vast emptiness of \nspace. Some scientists have speculated that there may be other universes that extend far beyond our own \nbut its mere speculation. NASA hopes that the next generation of Space Telescope technology scheduled to be launched in 2011, will have the capcity to observe  the very edge of the universe about 15 Billion years away and the very first light created in the aftermath of the Big Bang.
55707
You get into Quantum Theory with your intrigue and there is no evidence to support that the universe is not infinate.\n\nHOWEVER, according to the Big Bang theory there was nothing and then there was something in a centralized location millions (billions) of years ago. At the speed that the universe is spreading outwards there has to be an end to it and scientists are trying to get telescopes powerful enough to see to the beginning of time.\n\nWhat lays on the other side? Nobody knows.
83937
Yes the universe is expanding, thanks to dark energy and perhaps the shape of space itself.\n\nThe space, as far as I know, existed already. From what I understand, our universe exists within a 5th dimension. The "big bang" was really the collision of two membranes that caused a big release of energy along the contact surface and the formation of all matter (initially in the form of a quark-gluon plasma). This matter has kept expanding since and can probably expand indefinately along the 5th dimensional membrane, but there's really no way to know. Some speculate that the reason the expansion of the universe is accelerating right now is that we are in for another collision at any moment, which will destroy all matter as we know it. Sleep tight.
722611
the universe is constantly expanding although the rate is slowing and never reaches zero.\nexperts believe that the universe is finite yet has no edge, just like the surface area of a sphere. this could imply that if u reached one 'end' of the universe, u would end up on the opposite side or something like that
384787
The universe is curently about 156 billion light years across, expanding at a rate of 71(+/-4) kilometers per second per megaparsec. Current observations dictate that this rate is accelerating.  So we will go on, and on, and on for eternity
398088
I asked that question to Dr. Brian Greene, author of "The Elegant Universe".  His answer was "the Universe is continually expanding", and therefore, you can't put a size on it.  The Universe, in a sense, CREATES the space it's expanding into.  It is all-encompassing.