DieCommie said:

Like learningtofly says, things can go faster than the speed of light.  The universe expands faster than light, it is estimated to be 100 billion light years across and 14 billion years old so it must expand faster then light for that to be true.

People often cite relativity saying 'nothing can go faster then light' but that is not the whole story.  You have to be careful because relativity is tricky.  You cannot communicate faster than light and you cannot accelerate a mass up to the speed of light.  The universe expanding faster than the speed of light violates neither of these.

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deCypher said:

Also I'm pretty sure we think that the Universe is a finite but not bounded...

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Quote:

finite

–adjective
1. having bounds or limits; not infinite; measurable.
2. Mathematics.
a. (of a set of elements) capable of being completely counted.
b. not infinite or infinitesimal.
c. not zero.
3. subject to limitations or conditions, as of space, time, circumstances, or the laws of nature: man's finite existence on earth.

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Quote:

unbounded

–adjective
1. having no limits, borders, or bounds.
2. unrestrained; uncontrolled: unbounded enthusiasm.

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Do you not see the contradiction here?

deCypher said:

...fourth dimensional hypersphere.

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Quote:

In physics and mathematics, a sequence of n numbers can be understood as a location in an n-dimensional space. When n = 4, the set of all such locations is called 4-dimensional Euclidean space.

Such a space differs from our more familiar three-dimensional space in that it has an additional dimension, indistinguishable from the other three. This fourth spatial dimension is a concept distinct from the time dimension in spacetime, since time is functionally very different from any of the spatial dimensions; formally, spacetime is not an Euclidean space but a Minkowski space.

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Quote:

Hypersphere

The set of points in Euclidean 4-space having the same distance R from a fixed point P0 forms a hypersurface known as a 3-sphere. The hyper-volume of the enclosed space is:

    \mathbf V = 2 \pi^2 R^3

This is part of the Robertson-Walker metric in General relativity where R is substituted by function R(t) with t meaning the cosmological age of the universe. Growing or shrinking R with time means expanding or collapsing universe, depending on the mass density inside.

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I'm just wondering if you can expound further on this idea of the universe being a four-dimensional hypersphere, because I've never heard that theory before.

Poid said:

I'm just wondering if you can expound further on this idea of the universe being a four-dimensional hypersphere, because I've never heard that theory before.

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deCypher said:

Everything is getting stretched further apart.  I don't think it really makes sense to ask what the Universe is expanding into because there is no space outside of the Universe by definition.

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fireworks_god said:

You notice, then, the apparent contradiction between the idea that the Universe is expanding or stretching and the idea that there is no "space" beyond the Universe?

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What doesn't have an apparant contradiction, with regards to normal logic, in physics these days?
Somethings gotta give..

Fraggin said:

Poid said:

I'm just wondering if you can expound further on this idea of the universe being a four-dimensional hypersphere, because I've never heard that theory before.

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From the point of origin of the big bang, the frame of reference upon the universe would be four dimensional hyperspace. Think about it.

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