If Universe is expanding, what is happening to Time dimension?
968934
Time isn't a dimension all by itself - it's part of a dimension called space-time.\n\nAnd, I suppose, therefore if space is expanding, then space-time must also be too.
990249
The universe may very well be expanding into nothing. You see, we are used to thinking of expansion in terms of objects expanding into space (3D space) but the universe is space.\n\nThere is really no other way to explain it and it's something you might just have to accept though it's hard to envision.\n\nAnother explaination is that the universe may actually exist in a higher dimension (for example, 2D exists within 3D). According to membrane theory, the universe may have resulted from the collision of two "membranes" in a higher dimention and mass is the overlapping of those membranes.\n\nBut that is just one of the many possabilities.
347537
I have given an answer to this elsewhere, but I will repeat it here.\n\nAssuming that by the question you ask, you are essentially asking what is beyond the edge of our Universe, the answer to which will change depending on whether we live in a flat, open or closed Universe.\n\nOne way to try to understand it is to throw away a dimension, and imagine being a 2 dimensional being living on a sheet of paper. Sort of like a cartoon that you drew. To them, the Universe they occupy consists of only the paper itself. There is only up/down, left/right, there is no in and out of the paper for them, it may exist for us observing them, but they can't see us, and they are not aware of this extra dimension. Living on this sheet of paper, whilst flat on the desk there is quite obviously an edge beyond which to them, is nothingness...... hmmmm\n\nOk, so now imagine that they aren't living on a flat piece of paper but on the surface of a sphere (say of a baloon for example). The inside and outside of the sphere is a dimension inaccessible to them. Therefore, there are now NO edges to their universe. If they travelled upwards from their position (NOT leaving the sphere), then they would eventually come back to where they started. If you then started to inflate the baloon, it would expand, but to the "cartoon" people, all they will experience is seeing their surroundings expand. To them, their universe is expanding into another dimension, that they cannot see, and that it inaccessible to them.\n\nThis in a way, but with one dimension less, could be what is happening to our Universe. There may be no physical edge that we can ever come across, but it could be expanding into another dimension. \n\n\nOn the other hand, if you are asking if the Universe will, one day, simply cease to exist .... then that is a completely different answer!!!!\n\nThe Universe is expanding - into what, could be another dimension - and the amount of matter in the Universe will determine whether or not this expansion will stop and reverse, or whether it will carry on for eternity!  As it happens there is evidence to suggest that the expansion of the Universe is actually accelerating, and so the end of the Universe will be a very dismal cold place.  There will be no stars left giving out light, the heat of the Universe will be stretched out over infinity!  It will be the death of the Universe.\n\nIf there was enough matter in the Universe then the gravitational pull of all the matter could force the Universe to start to collapse back in on itself. Eventually it would all come together in one place in what would be called "The Big Crunch" - and this would be the end of the Universe as we know it.
918805
Time And Relative Dimension In Space
145870
This is a common source of confusion. There is a lot about this on the internet and I would direct you to those resources. However it is like we are ants on the surface of an expanding balloon. To ants, living in a 2 dimensional world, they cannot percieve the third dimension that the balloon is expanding into. \n\nThe attached link gives a very detailed, clear and complete discussion about misconceptions about the universe and its expansion. There are many other less difficult explanations available on the internet, however.
849985
time is just a dimension. like length, width , and height,\nGod lives in a dimension beyond our scope,\nmuch like an ant maybe only realizes 2 dimensions,\neverything is like a plane to them, although it may be curved, they don't comprehend the curvature,\nas we don't comprehend the curvature of space and time.\nbefore and after is a concept that only applies to those who are constrained by 4 dimensions...\ni think God can put the beginning and end of space and time in one simple (package) concept, and \ni wonder what he will do for an encore?\ni don't know,\ni doubt he was playing solitaire
680741
Well we couldnt go to the end.. because time is what results from the universe expanding.. so as time goes on.. the universe keeps growing
1059228
If the universe is everything, then what is it expanding into?\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.  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\nIf the universe is everything, then what is it expanding into?  It seems that our universe is all matter, space, and energy that we can perceive in this closed system.  However, that does not mean that there is not additional matter, space, and energy outside our universe.  In other words, there are probably other universes.  Therefore, the zone that we call our universe (or braneworld) may be moving through or expanding into other universes (or braneworlds).  In sum, all universes may be moving through a multiverse.\n \nSteve\n:-D
830256
The universe is still expanding and speeding up, faster and faster.  The outskirts of the universe can boggle the mind.  It has been thought that the mass of the universe would eventually stop the outward push and eventually draw it back to implode in on itself, then repeat.  Like a thirty billion year old flower.  Now it is believed that the universe will die a cold death with the universe continually speeding off in all directions.  Maybe we will run into another universe that is moving towards our own.  And no we will not fall off a cliff, the universe is expanding at a uniform rate in ALL directions.  There will be no drop-offs...
410204
The space-time continuum is the universe in four dimensions. And considering that I'm alive, then yes, we can survive in it.
1067957
No matter how many 'experts' around here claim that there are alternate universes or other dimensions or a brick wall, nobody--repeat NOBODY--really knows. Tons of theories, but not one single shred of evidence to support any of them.\n\nScientific research has repeatedly indicated that our universe is infinite in scope, and that it will expand forever although its contents (mass and energy) will very, very gradually fade away to nothing.\n\nBefore our universe began, and right now, there's probably nothing else but an absolute and infinite void totally without energy, mass, spacetime, dimensions or anything else.
727803
The known universe appears to be expanding. This does not mean it actually is expanding.\n\nIt might be gravity, or distortions in space affecting our perception of the universe.\n\nIt might be our misinterpretatons of the observations.\n\nThe observation is, that as we find galaxies farther away, they all are moving away, and the farther out they are, the faster they are moving away from us.\n\nDoes this mean the universe is expanding? Perhaps it means that the big bang occured at our location, thus everything is moving away from us. Yah, right....\n\nPerhaps galaxies that were moving at high speeds towards us, have already passed us, and are now moving away from us.\n\nPerhaps galaxies that are moving at high speeds towards us, have the electromagnetic energy from them shifted so much, that we cannot detect them by normal means. This might mean that there are the same amount of galaxies moving towards us as away from us.\n\nPerhaps, the universe was expanding, but is now collapsing, but it takes 15-20 billion years for the light to reach us, and we can only see that they were moving away 15-20 billion years ago.\n\nLots of maybes.
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.
861518
Nobody can answer your second part, if they try its just theory. They know it, I wont try to explain it either. \nIts against all logical thinking to just say..."the universe isnt expanding into something..", it has to be though what nobody knows. A ballon is a very good way to describe this motion, but still can't explain what "it" pushes into.\nIf there is "nothing" beyond the universe, then are we inside of some containment? \nThe idea that there is an end has still not been taken out of the equation...(Jan 21, 2002 Steven Haking lecture on Alternate Times @ Cambridge), he states that since we see into the universe more and more with technology, we see motion and activity as a guage that can tell us timelines of occurrences of the past, and can calculate distances and measure the speed at which these activities take place. And so he goes on to say that if given these calculations are correct, we can measure the entire universes' movement and therefore determine with some confidence where the edge would be, or should be. But, he said, so far we cant find an edge, though if we did, in all probability the universe is pushing itself into another adjacent universe.\nIf it were to be found someday that our universe has an edge, and theres a chance to peer past it....he says, then at least "containment" theory is off the table.
290592
*Edit*\nSorry for editing again!\nTo answer your questions. Yes the past still exists! But objects in the past have a fixed (p,q,r,s,u,v,w,x,y,z,t) location (where each letter represents another dimension in space, t = time). To realise this, think about where you were last Friday at exactly 4:00pm. You're position at that time will never change again. Wherever you were, that's where you'll always have been last Friday at 4:00pm. The rest of this post explains why you cannot go back to that time without dramatic changes in your string physiology, but that time travel may be possible for some types of matter (possibly supersymmetric matter?). Unless matter has moved backward along the time dimension, it cannot move forward, because the time dimension is expanding along with the rest of the universe.\n\nI had this discussion on a drive up to play hockey in Edmonton the other day. Here's my idea but I don't know if it is true:\n\nYes, time travel is possible. Time is just like the three other open dimensions we are used to - you can travel back and forth along the 3 space dimensions and it is possible that things (notice I don't say people, keep reading to find out why) can move back along time. But as far as I know, the four dimensions of space and time do not have radii like the 5-11 compactified dimensions of M-Theory do. Therefore something travelling in time cannot loop back to the same place in time that it was before. Thus you could not go back in time and have yourself arrive at the same place in spacetime that you are today. The dimension is linear.\n\nThe MOST important part of this is the idea of symmetry breaking. In my mind, symmetry breaking accounts for why something traveling back along the time dimension will not encounter the same events that originally occurred when it started it's motion along time. Symmetry breaking is a time dependent event. The easiest way to explain it is to reference the poem "The Road Not Taken" by Robert Frost. Events in time diverge at critical points (usually at critical values for state variables like temperature). Travelling back in time would cause disorder of various aspects of energy and matter in the universe, and different bifurcation paths, or "decisions", might occur, effectively changing the future in ways imperceptible to things that are made up of baryonic matter, which leads me to my final point.\n\nThe only objects that could time travel are those made up of closed, unattached strings. The strings of ordinary matter, like that which we are made up with, are open ended and attached to dimensions. This is why the mass that makes up us and objects like the sun distort spacetime. Time actually travels slower as you approach mass, and this is what causes masses to move toward each other. Time gets warped and masses fall towards spacetime that is in a lower transient state. What makes us up is effectively 'attached' to time, so unless we could change ourselves to be made up of matter of closed loop strings, we cannot attach ourselves from time. This also means we cannot leave our universe either, but that's another story.
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.
12025
no, because time is only a mesurement that we humans have come up with.  if anything, you can't travel through time because there are an infinite number of universes constantly being created.