The Big Bang Bamma

I have some questions too, if you dont mind.11. What do they mean when they say that the universe is flat? For local geometry, I know that it means the curvature is zero very close to zero, because "ratio of average energy density of the universe over critical energy density as " and "=1 or alittle >1". (All qoutes taken from Wikipedia.) And they also say that that "Even if the universe is not exactly flat, the curvature is close enough to zero to place the radius beyond the horizon of the observable universe." What exactly does that mean? As I read on, I get more and more confused. I can't even begin imagining how it would look like in 3(?)-D.I'm not very big on math, so please just explain it in plain english, if that is even possible.12. This might be a silly question, but is there a center of the universe? If we assume that Big Bang is true, and that the universe started out as a singularity and that it will eventually shrink and become a singularity and so on, then there should be a center. Like if we inflate a baloon, then we find it's center, then when we deflate it (or increase the pressure around the baloon), it will eventually become a small ball of rubber in the place where the center of the inflated baloon used to be. Given that the baloon is homogenious on the inside and made out of the same material etc.Hubble's law says something about the objects red-shift being proportional to the obfect's distance. I heard it being interpreted as accelerating rate of expansion of the universe as the objects get farther away. But further away from what? Does it mean that we are at the center of all things? Or does it have something to do with universe being isotropic, so then it wouldn't metter where you are or what direction you are facing.Does this question even make sence from the GR point of view or is it one of the "beyond the universe" or "before time" type of thoughts?I've read a few threads about it on this forum and did some extra reading elsewhere on the internet, but I lack good footing in the subject. I think its a real cool theory and I'd like to learn more.

I might be misunderstanding the concept of the term "radius". Ever since I can remember radius was distance from the ourter edge directrly to the center. How can a strait line have curvature?I think I understand why they say the universe is flat. But then its only flat from our perspective, right? If there was a being so large, looking at the universe from the "outside", for that being our universe could be a perfect sphere and have a very definite and positive curvature."From us. And every other point in the universe. Think of the balloon blowing up and all the points on the surface stretching away from each other."OK. I understand that. But I'm still not entirely clear about Hubble's law."Any two points which are moving away from the origin, each along straight lines and with speed proportional to distance from the origin, will be moving away from each other with a speed proportional to their distance apart."So it just says that with time the universe is expandinig at a faster rate, and all the objects within the universe get further away from each other at a faster rate and so on. I guess it explains that there is no center for that purpose."However, the best way to calculate the recessional velocity and its associated expansion rate of spacetime is by considering the conformal time associated with the photon traveling from the distant galaxy.That is Hubble's law."I guess that the term "distance" mislead me into wondering "where from" and "to what". In my mind, "conformal time" seems to explain it better. I think I'm starting to understand."No, there is not. The balloon is the rubber surface, not the space inside. Same with the universe. It is the surface that matters, except that the surface is 3d. This is child's play to a mathematician as one of the first things they learn is that a sphere is a 2d object, not 3d. It is the surface that matters. There is no inside. The sphere can be defined without any reference to a 3d embedding space. The inside does not exist! There is no spoon..."OK, gotcha.But, if we take a balloon and measure its circumference, or diameter, we could find its center, or really the center of the sphere of air that the balloon surounds. So could there be an imaginary center of the universe, or space within the universe?P.S: Those graphs don't make any sense to me. I don't even know what they are of.This message has been edited by Ragged, 11-15-2005 03:45 PM

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"I may disagree with what you have to say, but I shall, to the death, defend your right to say it" ~ Voltaire

So what were they saying about radius haveing a curvature. Im still confused about that.Also, if we can find the edge of the universe couldn't we calculate a center? An imaginary one?Please read my previous post. I would like to get some insight on all this.

[removed after rereading teh above posts]OK, I think I got that part down. No center sounds good. . I'll post more questions as I do more research. Thanks for your help.This message has been edited by Ragged, 11-17-2005 01:56 PM