Is the Universe Expanding Into Nothing?

[quantumfireball]

Is our universe a 3 sphere expanding in time into nothing?

OR

i

 

[cristo]

Well, there is no real answer to your question at present. Yes, the universe could be a sphere, but it would not be expanding into anything. Note that this is not the same as saying the sphere is expanding into nothing! However, currently we think that the density of the universe is very close to the critical density; that is, the universe is flat (as opposed to open or closed).