I probably have no idea what i am talking about, but here is my question none the less.

I have heard that we have seen the "fringes" of the universe. Now, I have always thought of the universe as being everything that can possibly exist. All that is, is the universe. It makes sense to me that the universe is infinite in everyway, but these "fringes" throw me off. If there are fringes of the universe, doesn't that imply that "something" else lies on the other side of these fringes. If that is so, wouldn't whatever lies on the other side still be part of the universe? I feel like space has to be infinite becuase there is no "center" of the universe, so it must just go on forever.

Now, i feel like i may not be grasping the idea of space. I always hear space compared to a 2d surface (like the surface of a balloon), and i am not sure what that means exactly, because we are obviously in a 3d world. What am i missing?

thank you
reenpeery

Nobody knows whether the universe is finite or not. I'm not sure where you heard that it isn't, but that is a common assertion without evidence for it or against it. (And it's often used as a metaphor for philosophical purposes and such, or in figurative exaggeration such as that it's so big compared to us that it might just as well be infinite, so sometimes it can sound like someone's saying that even if (s)he doesn't mean it.)

If it's infinite, then we can't be near its fringes or its middle because it doesn't have them. If it's finite, then we can be, but nobody knows in that case what's beyond it or what the edges are like, and it's even possible that it's finite but still without edges or a middle (due to some funky way of wrapping around itself... which could mean that we'd see two of some objects in opposite directions with light looping around like Pac-Man traveling off the right side of the screen and in from the left side, but we don't have any way to determine that right now). A recently-discovered very large area with a serious shortage of galaxies in it compared to other areas of our field of view has been described as a possible sign of a boundary of the universe, in which case we would be closer to it in that direction than we are in the other directions. There's also a tiny variability in the nature of the microwave background radiation based on what direction you look in, but I haven't seen whether that's thought of as indicating our position in a finite universe, or our movement relative to the biggest frame of reference of all, or something else.

What we can be described as "on the fringes of" is our galaxy, although others would describe our galactic position as more like halfway between the middle and the edge.

The 2D descriptions are just analogies, to make unvisualizable ideas visualizable or compare unfamiliar concepts to familiar ones.

Some theories require extra spatial dimensions from 4 on up which we can't detect or imagine ourselves, or involve some peculiar compression/stretching/bending of space in a way that's most easily visualized as happening in an extra spatial dimension. So, to try to illustrate those concepts, people simplify the world down by at least one dimension, using two to represent what we normally think of as the plain ordinary three, so that they'll have the third dimension available in which to show whatever higher-dimensional oddity they want to talk about, because they just can't use actual higher dimensions to show what they're REALLY talking about.

Another analogy using a 2D universe has nothing to do with extra dimensions but just seeks to make an unfamiliar concept more familiar anyway: the expansion of space. What's most accurate to say is that all three dimensions are stretching so the space between any two points gets longer, but most people have never seen anything expanding like that in three dimensions, so the idea of the universe as a 2D balloon surface is used instead because people are quite familiar with balloon stretching. The idea is to get people to apply what they're familiar with in 2D balloon surfaces to the less familiar 3D setting for the same concept of stretching. It doesn't mean anyone's claiming the universe is actually 2D; it just means that they're momentarily pretending, or talking AS IF it were 2D, to get audiences to take the 2D concept and then step it up to three.

Reenpeery, you might also be getting stuck with regards to the universe, and the observable universe. The latter could be said to have a fringe, but it's not physical, just a function of the finite speed of light and the age of the universe.

http://en.wikipedia.org/wiki/Observable_universe

http://en.wikipedia.org/wiki/Cosmic_...ound_radiation

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If something is in me which can be called religious then it is the unbounded admiration for the structure of the world so far as our science can reveal it... of the manifestations of the profoundest reason and the most radiant beauty, which are only accessible to our reason in their most elementary forms...
Albert Einstein