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What is at the center of the universe? after the Big bang?
Sure, the analogy is two dimensional, because we're used to curved two dimensional spaces. If you could already visualise curved three-or-four dimensional spaces, you wouldn't use the analogy. Main point is that the balloon's surface has no centre. And no reason why all the ant colonies couldn't exert attractive forces on each other (perhaps by running springs across the surface, with effects analogous to gravity), causing the entire space to recollapse, despite there still being no center of collapse (within the two-dimensional analogy).I believe Balloon and ant example is a poor analogy. In this analogy, ant would see only other ants moving away in two dimensional space. But in actual universe, you would see matter moving away in three dimensional.
The earth! We can't see that now, because, I believe, the universe is in a temporary state, so it is not now obvious.What is at the center of the universe? after the Big bang?
Sorry but this is all wrong. The solution to the equations of general relativity describing a homogeneous, isotropic and infinite are perfectly happy with the current observations. You do not need to have a center of the universe that everything else is moving away from. There is no net gravitational force on anything in the universe, since in general relativity gravity is not a force. Instead all the matter in the universe follows geo-desic paths determined by solving the equations. The solutions tell us that everything moves apart even though the infinite universe is homogeneous.If there is no center, all the galaxies would be attracted equally by the surrounding galaxies. So there wont be any net gravitational effect on any Galaxy on a large scale (Ignoring short distance ones like Andromeda). But still
most of the astronomers believe in a big crunch due to gravitational attaction provided the matter density in the universe is less than critical density and also Dark energy is said to be of overcoming gravity. So here we are clearly accepting gravity on large scales which is not possible if the universe doesn't has a center.
I am not saying that there is a center to a universe but still its not clear.
Does that mean that the Universe is constant? Does that mean while the outer shell is expanding ... the Universe is also contracting at the center?there is no centre, or you can say everything is at the centre.. Because the universe began in a single point, the whole universe and its centre where the same point, so now everything is at the centre of the universe.
This is also why no matter where in the universe you place yourself every thing seems to be moving away from you, like you were at the centre. Because of the expansion of the universe...
No, No and No are the answers I'm afraid.Does that mean that the Universe is constant? Does that mean while the outer shell is expanding ... the Universe is also contracting at the center?
Also, Isn't ther violation of conservation of mass during Big bang?
Sorry but this is all wrong. The solution to the equations of general relativity describing a homogeneous, isotropic and infinite are perfectly happy with the current observations. You do not need to have a center of the universe that everything else is moving away from. There is no net gravitational force on anything in the universe, since in general relativity gravity is not a force. Instead all the matter in the universe follows geo-desic paths determined by solving the equations. The solutions tell us that everything moves apart even though the infinite universe is homogeneous.
It all boils down to initial conditions. The Big Bang caused everything to begin moving apart and hence they continue to do so. It is a common misconception that the Big Bang happened at a point. This is not the case. It happened everywhere. There is no one point you can trace all the matter in the universe back to if you run time backwards.
By the way, the Big Crunch is not thought by anyone to be a reasonable prediction of the universes future. It is not supported by the observations at present. Even if it was, it dosn't require a center of the Universe to exist in order to occur. A Big Crunch is NOT where all the material in the Universe moves to a single point. What it is is that density of the universe goes to infinity, but there can still be an infinite (or indeed finite) distance between points in the infinitely dense universe.
It is true that we cannot be certain that the universe is infinite given that we only observe a finite portion. However even if somehow, in violation of present theories (the solutions of GR we use to model the universe require it to be infinite), the universe is finite there is nothing that make the center of the finite blob special. It just happens to be the center.I wouldn't argue with general theory of relativity. Here you are considering universe as infinite. So many things are possible under infinite universe. If the universe is infinite, no one would dare to say that there is a center to the universe. But how can anyone be so sure that universe is infinite ? and not finite ?. Is there any sound practical evidence that universe is infinite ? Infinite universe would also mean infinite energy which is beyond my grasp. Please explain.
A quick google search found http://www.astronomycafe.net/cosm/bang.html" [Broken] which might be helpful. Read these and post any questions you still have.You are saying that Big Bang happened everywhere. How can this be ?
Can you give brief explanation or direct me to some link ? I never heard of this..
I'm not sure what any of this question means. See below, I hope that clear up the confusion.You are saying that under big crunch, density of the universe goes to infinity.
We know that there is nothing higher than infinity. How one can measure distances in an infinitely dense universe ? Please explain.
This is only true assuming a finite mass, since the mass of the universe is infinite it can be infinitely large as well as being infinitely dense.Infinite density means zero volume.
See above, the Big Bang is NOT a point of zero volume. It is a singularity so discussion of volume is meaningless.How can one measure distances in zero volume ? Are you talking about extra dimensions ?
Those questions are irrelevant, since the universe does not need to be spatially infinite to lack a center. That's one of the things that the balloon analogy tells us.So many things are possible under infinite universe. If the universe is infinite, no one would dare to say that there is a center to the universe. But how can anyone be so sure that universe is infinite ? and not finite ?.
The Big Bang was not an explosion and the unverse looks pretty much the same in every direction.Whats at the center, well, first answer whether universe in restricted to some expanse or not ? The point of bigbang needn't be the center (how do we know if the explosion was symmetrical in all dimensions)
PS: Sorry if this sounds unconvincing,i am a novice in this field. I am just sharing my views.
Could you please explain how a three dimensional universe could be finite but still has no center ?Those questions are irrelevant, since the universe does not need to be spatially infinite to lack a center. That's one of the things that the balloon analogy tells us.
Wallace that is exactly the same as I said. (What I meant at least)."It is a common misconception that the Big Bang happened at a point. This is not the case. It happened everywhere. There is no one point you can trace all the matter in the universe back to if you run time backwards."
I did, it was my first post:"You are saying that Big Bang happened everywhere. How can this be ?
Can you give brief explanation or direct me to some link ? I never heard of this.."
All the above looks fine but is there any evidence for fourth dimension which is beyond human perception ?Visualizing it isn't really possible because our eyes (and thus our brains) are limited to seeing in 3 dimensions, but in 1 dimension (the edge of a circle), the perimeter has no center, but finite length and is curved in a second dimension. In two dimensions (the surface of a sphere), the surface has no center, but a finite area and is curved over a third dimension. In three dimensions, then, the space would have no center but finite volume and there must be a curvature in higher dimensions. The three concepts are the same.
You can't visualize why/how, but if you fly far enough in one direction, you'll end up back where you started, just like if you were flying around the earth.
Yup... Math, and reasoning.All the above looks fine but is there any evidence for fourth dimension which is beyond human perception ?
Imagine you are on a sphere, and you move in 2d. Eventually, you will move around the sphere, and come back to where you were.How can you be so sure that if someone travels in some direction in the universe would reach the same starting point ?
just out of curiosity:Those questions are irrelevant, since the universe does not need to be spatially infinite to lack a center. That's one of the things that the balloon analogy tells us.