However, I don't think that the universe is infinite, so I'd have to say that it is a sphere (merely because, if everything expands from a point, and all sides leave at the same speed, the result is a sphere).

I also approve of the multi-dimensional perspective, in which the spacial dimensions that we are used to are flat, but the others are "curled up".

One, the universe is infinite. There would be no shape in such a case. This is allowed under the big bang theory, believe it or not.

Second option, the universe is finite. If so, it is a hyper-shape. Since that word I made up probably doesn't exist, allow me to explain. If the universe is spherical, it is a hypersphere. That is, it is like a 3 dimensional curved surface, which we cannot imagine. We can however, picture 2 dimensional surfaces, such as the surface of the earth. There is no center or edge to the surface of the earth, and the universe would be the 3D equivilant of the 2D earth. No center, no edge. But like normal shapes, there are countless possible hyper-shapes the universe could be.

Now as to whether or not something could the expansion, physicists would say yes. The energy of the vacuum is said to be causing the expansion to accelerate. Under supersymmetry models, the vacuum energy could transform from having negative preasure to positive, which would halt the expansion and cause the universe to contract. But this is speculation at this point, and I'm not sure how valid it is.

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Originally posted by Eh:
2 Options.

One, the universe is infinite. There would be no shape in such a case. This is allowed under the big bang theory, believe it or not.

Second option, the universe is finite. If so, it is a hyper-shape. Since that word I made up probably doesn't exist, allow me to explain. If the universe is spherical, it is a hypersphere. That is, it is like a 3 dimensional curved surface, which we cannot imagine. We can however, picture 2 dimensional surfaces, such as the surface of the earth. There is no center or edge to the surface of the earth, and the universe would be the 3D equivilant of the 2D earth. No center, no edge. But like normal shapes, there are countless possible hyper-shapes the universe could be.

Now as to whether or not something could the expansion, physicists would say yes. The energy of the vacuum is said to be causing the expansion to accelerate. Under supersymmetry models, the vacuum energy could transform from having negative preasure to positive, which would halt the expansion and cause the universe to contract. But this is speculation at this point, and I'm not sure how valid it is.

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Other options: The Expansion = Nothing..zero points, so that
Something needs a nothing for movement to exist,(if you are something, then try moving through 'something else' of the same 'something'.

The virtual vaccum pool provides the Minimum Nothing, this allows products of less 'somethings' to move at an ever increasing speed, the more 'something' you are, the less movement through the nothing happens, infact the more something you are, the more still you become, until the 'Nothing' cannot support you, and you fall through a hole of your own making.

As you Fall, you drag nearby 'somethings' towards you, the more 'something' you become.

For things that are made of minute 'somethings' they can skirt around the pool with the greatest of ease! and the swiftness of speed! in fact they start jumping from place to place, as their freedom of movement allows, they eventually skip so far, they become a 'virtual' Nothing, which feeds the virtual pool of nothingness, which expands at ever increasing moments, which allows the 'somethings' extra dimensional movements.

Galactic Points can re-emerge as virgin births of Vaccum Nothingness, Hyperdimensionally linked from the outside in, and inside out.

Case opened and closed!

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Originally posted by Eh:
Why do people insist on calling the vacuum nothingness? It is a thing (field) and is packed with energy. For once, I would like to hear people call matter nothingness, because it's basically the same as empty space. And no, this vacuum does not require any outside space to expand. Intuition is the only reason that idea is around, but we already know intution isn't much help in modern phyiscs.

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You are correct, in that Nothingness is a very bad descriptive word.

Vacuum, void of matter is not void of energy.

Vacuum energy is space that has no fixed points of matter within certain horizons.

The presence of matter slows the vacuum, or provides stability for distance to be calibrated btween two or more 'physical' bits of matter. A large quantity of matter resists being moved by vacuum space.

A small quantity of matter cannot resist being moved at a certain speed within a large open field of Vacuum Space, it may be the same thing as Matter, but the scale of quantity is vastly different.

If the universe is endless, then "I" must be in the center, for the center would be everywhere. Or, would that be another way of saying God embraces everything?

The Advent of Dionysus - Online Book

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If the universe had a shape that would imply boundaries

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Not true... depending on what you mean by boundary.

We know plenty of shapes that have no ends, edges, or whatever; for example lines, parabolas, circles, and hyperbolas all have no boundary. Planes, klein bottles, ellipsoids, and parabolic cylinders also have no boundary.

As opposed to things like line segments whose boundary is its endpoints, circular arcs also have endpoints, a disk have a boundary which is a circle, a ball has a boundary which is a sphere, et cetera.

(by no boundary, to be technical, I mean their boundary is the null set in the homological sense)

Hurkyl

But because of the cosmological principle (the universe looks the same everywhere) the hyper-shapes are the only options supported by cosmologists. The problem is, if the the universe is so big that we can only ever see a small region of it, we can never know for sure what the overall shape is, or if there is a center.

If, on the other hand, the universe was finite, and had a boundary, it would imply an outside. But how can you have an outside to that which is inclusive of everything? Perhaps the Truman Show?

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Originally posted by Eh:
Interesting bit of information to add to this discussion. I said that finite universes must be hyperbolic or a hypersphere, but this is wrong. I did some reading, and it appears there are solutions to GR that would allow for a spherical universe with a center and edge. Someone will have to clarifiy that, because I could be reading something wrong.

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I think this is correct -- I've read about something similar lately. You might want to Google for "white hole models" or "white hole cosmology". For example, there's the following paper that discusses such models ("Lemaitre-Tolman", in this case):
http://www-library.desy.de/preparch/gr-qc/9803/9803014.ps.gz

Another example would be the "Oppenheimer-Snyder" solution, which is created by pasting an inner chunk of FRW solution to an outside of Schwarzschild solution. This would collapse to a black hole, but its time reversal is also a solution, and it can be seen as a Universe coming from a "white hole".

This has an expanding ball of matter as the Universe with a definite edge, and empty space outside. Many people mistakenly think the standard cosmologies are like this; they're not. Considering the above GR solutions, it does turn out to be possible, although it's a rather obscure possibility (I wouldn't have heard of it if I hadn't intensively searched the web for such things). Cosmologists seem to think of it as bizarre or unlikely for reasons I don't completely understand (it's not homogeneous at least).

I also have no idea how compatible this is with newer information on acceleration of expansion and so on. If anyone finds out anything interesting based on this, please post here.

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By the way, a sphere is not a ball, it's the edge of a ball; the edge of a 3D drop of water is 2D, and the edge of a 4D drop of water is 3D. This 3D edge is what Hawking means when he says the Universe is a sphere.

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Originally posted by Iacchus32:
Then again, if you were to take a drop of water and suspend it in weightlessness, it would assume a perfect sphere (I guess?) which, implies the shape of the universe. Of course that would also imply a center of gravity wouldn't it? Meaning, does the universe have a center?

The Advent of Dionysus - Online Book

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If it is a sphere, then yes, obviously. And this is the only shape that I can see as feasible, if you take the BB theory as being correct.

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Originally posted by Mentat:

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Originally posted by Iacchus32:
Then again, if you were to take a drop of water and suspend it in weightlessness, it would assume a perfect sphere (I guess?) which, implies the shape of the universe. Of course that would also imply a center of gravity wouldn't it? Meaning, does the universe have a center?

The Advent of Dionysus - Online Book

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If it is a sphere, then yes, obviously. And this is the only shape that I can see as feasible, if you take the BB theory as being correct.

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Here's a link to NASA which shows the universe is flat, not a sphere or open saddle shape.
The universe is flat says NASA

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Originally posted by Eh:
A flat universe can still have an overall shape and be finite.

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I should have included this too. The NASA folks say the universe will expand forever.

Here's the conclusions cut and pasted:

1) Universe is 13.7 billion years old with only a 1% margin error.
2) First stars ignited 200 million years after the Big Bang.
3) Light in WMAP picture from 380,000 years after the Big Bang.
4) Content of the Universe:
4% Atoms, 23% Cold Dark Matter, 73% Dark energy.
The data places new constraints on the dark energy. It seems more like a "cosmological constant" than a negative-pressure energy field called "quintessence". But quintessence is not ruled out.
Fast moving neutrinos do not play any major role in the evolution of structure in the universe. They would have prevented the early clumping of gas in the universe, delaying the emergence of the first stars, in conflict with the new WMAP data.
5) Expansion rate (Hubble constant) value: Ho= 71 km/sec/Mpc (with a margin of error of about 5%)
6) New evidence for Inflation (in polarized signal)
7) Fate of the Universe: it will expand forever...