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View Full Version : might our universe be a 4-sphere?



dodecahedron
2009-Feb-11, 09:44 PM
Been reading about how the universe is a sphere, a saddle shape and may be flat but is there any evidence that says our universe isn't a hypersphere?

IsaacKuo
2009-Feb-12, 02:01 PM
When you read about the universe being a "sphere", they do mean the surface of a "hypersphere". Just as the surface of a 3-d sphere is 2 dimensional, the surface of a 4-d hypersphere would be 3 dimensional.

agingjb
2009-Feb-12, 02:49 PM
They do indeed mean the boundary of the hypersphere. If the universe is a hypersphere, then it's very big one since there isn't, I'm told, any detectable curvature in the bit we can see.

I suppose the best argument is that if space started out finite, then the hypersphere (S3) is a good a guess as any for the topology of the whole thing if, as seems reasonable, it remained finite.

S3 also has properties only shared by the circle (S1) and S7.

mugaliens
2009-Feb-14, 09:38 PM
Been reading about how the universe is a sphere, a saddle shape and may be flat but is there any evidence that says our universe isn't a hypersphere?

You mean like a tesseract (http://en.wikipedia.org/wiki/Tesseract)?

dodecahedron
2009-Feb-16, 05:44 PM
You mean like a tesseract (http://en.wikipedia.org/wiki/Tesseract)?

B-b-but a tesseract isn't round.