i.e. if you travel in one direction in space, will you eventually reach your starting point? I know the universe is finite, expanding, and has no physical edge. It's like our 3d universe is projected onto a 2d surface of a balloon. But the balloon surface IS a pac-man universe.\n\nNow if we're not in a pac-man universe, and there is no edge, what will you reach if you travel in one direction for eternity?
208211
the answer to your question is a definite 'maybe'. We don't know yet. Possibly, we never will.\n\nSome scientists think that it is a pac-man universe. Some think that it's a pac-man universe, but since it's expanding faster than we can ever travel, we'll never know. A few think it's not a pac-man universe, and that, while there are limits to the size of the observable universe, the actual universe is infinite in size. Some think that it's not a pac-man universe, and that it's a dumb question because the universe can expand away from us faster than anything can travel through it. Pretty much all of them will admit that we don't know with anything remotely resembling certainty.\n\nIncidentally, to the best of our ability to measure it, spacetime appears to be flat, and not curved back on itself. However, a couple years ago, a physicist proposed a model involving dodecahdral 'faces' to the universe, resulting in something shaped similarly to a soccer ball, which means pac-man universe with no curvature. Again, we don't know yet, and it may be a long time before we find out... if we ever do.
70961
If the universe is infinite, it doesn't mean that everywhere is the center, it means that it has no center. Or, if you mean relative to the existing matter...well, that isn't infinite, and has a defined center.
319015
"...What are the dimensions (length, width, and height or thickness) of the physical universe (in light years)?..."\nThe universe can't be measured in terms of length, width, and height. Such parameters require some reference point from which measurements can be made, along with some distant boundary where the measurement would end. You simply can't do that with the universe because the universe is isotropic, meaning it's the same in all directions from any observing point. From Earth we can look outward in any direction and 'see' about 13.7-billion light years. From Earth that represents a boundary. Here comes the tricky part: if some alien in a galaxy 13.7-billion light years away from Earth looked outward in all directions (including back towards Earth) they'd 'see' a universe that appeared to be 13.7-billion light years in scope. In other words, the universe has no boundary. To have one it would have to be inside some "thing" else, and there's absolutely no evidence that such is the case.\n\nTo confuse the issue even more, if we had the ultimate telescope with limitless viewing power we still will never be able to see into the universe beyond a certain range. That's because at almost the same instant of the Big Bang the universe briefly expanded faster than light (this doesn't violate relativity because it was the space of the universe that did the expanding). In our 'normal' universe the speed of light is the speed limit which prevents us from ever seeing any of that inflation because it's moving away faster than the speed of light.\n-----------------------------------------------------------\n"...I've read that the universe is thought to be "saddle shaped..."\nMore recent observations point more towards the universe being geometrically "flat." This simply means that the universe appears to be infinite, that its space will expand forever while cooling more and more over the eons.\n------------------------------------------------------------\n"...What does it mean for example, to say that the universe is expanding at a rate of 70 kilometers per second per (x number of light years)?..."\nYou've described the so-called Hubble Constant. (70 km/sec/Mpc) It means if galaxy 'A' is 1 Mpc (1-million ly) away from us it's recessional velocity will be 70 km/sec. If galaxy 'B' is 2 Mpc away then it's velocity will be 140 km/sec It's important to keep in mind though that it's space that's expanding like that, not the galaxies moving THROUGH space; they just get carried along.\n------------------------------------------------------------\n"...I was not able to find a rate of acceleration of expansion..."\nI've been looking for a figure too. So far the only thing I've come up with is -3.15^36 /sec/sec  Darned if I know what the units of measurement are though. Maybe someone else on Yahoo can help us out with that.
175080
Outer space is not nothing. Even without the presence of matter, it is teeming with quantum foam, particle-antiparticle pairs, space, and time. For all we know, spacetime may not exist outside our universe."\nAlso, the universe may not be bounded. The only way to "exit" may be to find a "fourth direction". Ie., think of a point in an unbounded plane. The only way for the point to exit its universe is to somehow find the "third direction".
247849
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
327338
well, spacetime does not seem to end, and nothing is "holding up" spacetime.\n\nthe universe is not infinite. the universe is finite yet has no edge and no center. it may be something like the two dimensional surface of a sphere. nothing inside or outside the sphere exists for the two dimensional surface.\n\nalso, i have something for you to think about. the radius of observable universe is about 46 billion lightyears, yet the universe is 13.7 billion years old.
482427
There may be two answers to this question.\n   First;The universe is spherical.expanding from  a single point.\n   It is definitely finite and will someday become extinct.\n   Seems like a big ball!!\n\n   Second;Time acts as just more than an arrow barreling inexorably in one direction.\n   Every entity in the universe has a zero  time point.\n   You,me and an atom.\n   In any direction we look into the past.\n   This would imply a two dimensional expanding sphere.\n   This would not be much fun!\n   We know the universe works.It incorporates a sort of holographic feature that allows entities to interact,seemingly in a solid sphere.\n   Two people in a room see each other as they were in the past.\n   Maybe three-hundred millionths of a second ago.\n   Because our reaction time is about one-tenth of a second,we have no awareness of this time lag.\n   To be significant to two people they would have to be about 18,000 miles apart.They would be absolutely unaware of each other.\n   This holographic trick of the universe extends to fundamental particles[The uncertainty principle] and to celestial bodies,stars,galaxies and large structures.\n  Philosophers may want to jump in here to try and hone a comprehensive configuration to this phenomenon.\n   Well I hope I did not confuse you to much. I am going to have sit down and figure out just what I said.
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?
156407
Let me ask you, what would it be like of you were at the end of the Earth? Would it be like a cliff that you could jump off? That is silly because the Earth is round. It has a finite surface area but no edge. The edge is the surface you are standing on. Every place on Earth is the edge. It is believed that in a similar way the 3D universe is curved in the 4th dimension, so that it has a finite volume but no edge. Or you could say you are at the edge all the time but don't know it since you cannot perceive the 4th dimension.
598033
This is an interesting idea, and yes it is plausible.  Unfortunately, there is no way for us to surmise whether or not it is true, so this is something that can never make the status of a scientific theory.  \n\n(Misconception: most people think a theory is just an idea, but a true scientific theory must stand up to experimental scrutiny in order for it to make the status of a theory.  Since this concept is impossible to test or verify, it can never be a theory, and must stay in the realm of ideas and friendly debates.)\n\nHere is another cool thing to consider:\nThe Universe cannot be infinite, because it is expanding, which points to its origin where everything began at the same point, namely the singularity of the Big Bang. Therefore, if it is expanding, it is bounded.\n\nHowever, it is thought that it probably doesn't have an edge, much like the Earth doesn't have an edge. If you started in a spaceship and went in a straight line, you would eventually end up where you started, much like if you started at the North Pole and went in a straight line, you would end up back the North Pole.\n\nThe reason: although you would be going in a straight line on the 2-D surface of the Earth, that line is curved in the 3rd dimension. So, if spacetime is curved in the 4th dimension, you could be going in a straight line 3 dimensionally, but it would be curved 4th dimensionally.\n\nHowever, one could look at it this way instead: The Universe does have a definite edge, but as ou approach that edege, you and everything else shrinks, which means you could never make it to the edge.  You wouldn't be aware of the shrinkage because even the measuring devices would be shrunk, so you would think you were going endlessly in a straight line, when in reality, you were approaching an actual finite edge, but never making it.  Again, it can never be tested, so just a thought ;0)
331443
By definition, the universe is a singular entity and no other exists except in theory (ex. Inter-dimensional universes, sub atomic universes and anti-matter universes). If we consider the universe as finite instead of infinite, then we can roughly conclude that it is spherical in shape, and the outermost bodies are roughly equidistant from the center. \n  In Einstein’s theory of the Time and Space continuum, Time and Space are cylinders and the intersection of two cylinders is a sphere. as the intersection of the cylinders change, so does the location of that sphere, It can be see as moving through time, or moving through space, or moving through time and space simultaneously.\n    Not all possible points of time and space are contained with that sphere at one time, but the sphere can pass through them and we move through time and space. Once a point has passed though our sphere it is gone.\n\n   UNLESS the cylinders are actually rings. The intersection of the two rings is also a sphere. In this case, a point can pass through our sphere several times as we are in constant any yet synchronous motion with the other ring. So if our universe is actually a sphere, and the intersection of circular cylinders (rings), galaxy will always be a galaxy, but it can come into existence, die and be reborn all within it's own space it passes through our sphere of existence over and over again.\n\nSorry...this was probably more than you wanted. It's possible, yes, but not likely in this sphere of reality.
80489
I totally know what you mean. I used to think about that all the time, but I would just exhaust myself. I think the only sure thing we know is that we know nothing. I am a bit of an agnostic, but certainly don't think that everything just happened by chance. Was there ever nothing? If so how did we ever get something? If scientist say there is an end to the universe, what is it like a wall? Plexi Glass that you just bounce of of? Or is it like Pacman where you just pop out on the other side? There is so much that is just unexplainable in t his world. I am just glad to be a part of it. I have pretty much given up on trying to figure it all out. While I am in no hurry to die, I am somewhat excited at the possibilty of everything being answered once I go. Good luck in your search for answers. We need the Teacher's Edition of the bible, one with all the answers in the margins( I wonder how much that would go for on eBay?)
321917
Quite an interesting question.  Well, it's true that the Universe is expanding, has been expanding since the Big Bang, and always will expand.  Plus, it's been doing so at the speed of light, so unless there's some way for us to travel faster than that, we're already too late to actually go (or send something) and find out what it's expanding into.  Point B can never reach the end.  Having said that, we're fairly sure that 'nothing' is beyond space.  Space is expanding into nothingness.  Of course, this is a hard concept since most of space has nothing in it anyway.  Yet even  when space is empty, it's still considered 'something.'  This empty 'something' expands into the nothingness.  Confusing, I know, but I can't think of a better way to explain.  Anyway, I don't believe there's a container that would stop the Universe from expanding.  I suppose it could be theoretically possible, but I'm not sure how.  I believe it will keep on expanding forever.
297767
as far as we can tell, the universe is bigger than anything else ever.  the old school of thinking is what named the universe (from Latin, uni = one, verse = turn, ...) and the thought was that it went forever and contained everything.  some dictionaries may have something different to say.\n\nif the universe is finite, then what is at the edge of the universe?  what may lie beyond the universe?  are there other universes?\n\nask God when you get to heaven i suppose.
597381
The Universe cannot be infinite, because it is expanding, which points to its origin where everything began at the same point, namely the singularity of the Big Bang.  Therefore, if it is expanding, it is bounded.\n\nHowever, it is thought that it probably doesn't have an edge, much like the Earth doesn't have an edge.  If you started in a spaceship and went in a straight line, you would eventually end up where you started, much like if you started at the North Pole and went in a straight line, you would end up back the North Pole.\n\nThe reason: although you would be going in a straight line on the 2-D surface of the Earth, that line is curved in the 3rd dimension.  So, if spacetime is curved in the 4th dimension, you could be going in a straight line 3 dimensionally, but it would be curved 4th dimensionally.
77343
The above answers are interesting but, modern physicists speak extensively about 'multiverses'.  So, does one universe end at the edge of another? or, do they 'co-exist' in space and time? OR??????
221639
By definition, parallel lines can never intersect or meet.\nParallel universes, if they would exist, must behave similarly to be truly parallel.\n\nConsider: If parallel universes were to be within a few billion light-years of each other, they would eventually be drawn toward each other. Result: No longer parallel.