The visible universe is a sphere.

Therefore the universe looks like a ping pong ball.

From the inside.

But without the plastic wall/boundary.

And the boundary is painted completely and perfectly black so that you cannot see past it.

Or even see the boundary itself.

And the boundary is expanding at the speed of light.

BTW: the observable universe is bound by light speed multiplied by the age of the universe.

Sorry. No source. I just reasoned it out. Like this.

The observable universe is bound by the speed of light multiplied by the age of the universe. If the age of the universe is 15 billion years, then the observable universe is 15 billion light years. Anything at 20 billion light years cannot be seen now, because it would take 20 billion years for the light to get here. And if the universe is only 15 billion years, it would take another 5 billion years for the light to arrive. (I heard this somewhere, but cannot remember where).

If the limit of the observable universe is the same distance all around, it would be a sphere. And a ping pong ball is spherical.

Not really. There may well be parts of the universe beyond which is not observable (because the light has not had enough time to get here).

Not without some breakthrough in science and tech. When you're just below light speed, if you're hit by a grain of dust, that grain will have an unimaginably large mass. The collision would be catastrophic.

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Added on July 2, 2011, 8:50 amYou're referring to a hypersphere?

In other words, the universe might be finite but unbound. Just like we can walk forever on the surface of the earth and never find the edge, though the earth's surface area is not infinite. And if we walk far enough, we would eventually end up at where we started from.

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Added on July 2, 2011, 8:54 amThis is why we have virtual machines. So that badly behaved critters (programs) in one universe do not cause problems in other universes (VMs).

This post has been edited by dkk: Jul 2 2011, 08:54 AM

Mr A has celiac disease?