[Lonesome in Massachussets]

There may be other universes, but by "the universe" astronomers and physicists mean all the matter (and the space it occupies) that we will ever be able to see, know about or communicate with. According to our current understanding of the laws of nature, if other universes exist there is no way for light, or anything else, to travel from them to us, or any part of our universe, or we to them.

It is a consequence of the theory of General Relativity that our Universe is finite, but it does not exclude the possibility of other universes.

[dinoparty]

This makes more sense, explained this way.

[agere_contra]

but it does not exclude the possibility of other universes.

Any such "other" universes would have to be strictly orthogonal to our own (no interaction allowed). If you can in any way sense or detect another universe then it's not another universe, it's more of this one.

Which means that there can be no provable nor useful science about "other universes". Any observation of another universe is - by definition - not an observation of another universe.

We should probably stop throwing these loose Star-Trek tropes around IMO. "Parallel Universes", "Alternate Universes" etc - they're fine if you're a lazy SciFi writer and want a quick plot line about evil Spock or a leather-clad Intendant Kira (Freepers will know the DS9 episode I mean!) but they're appalling science.

[scrabblehack]

Hmmm...this seems to not be news. Bonanos, Stanek, et al.'s estimate is 61 km per second per million parsecs.

http://csep10.phys.utk.edu/astr162/lect/cosmology/hubble_constant.html

has it between 50 and 100.

There's an interesting essay by Isaac Asimov -- "The Proton-Reckoner" -- published in 1966 -- Hubble's constant was thought to lie between 75 and 175. Asimov takes the lower limit of 75 and calculates an observable universe of radius equal to 13 billion light years. A value of 50 would indicate an observable universe equal to 20 billion light years.

[MHGinTN]

Actually, GR sort of does exclude other universes. It works like this: the laws of our universe are 'balanced' (defined) by the conditions of our universe, thus our particular space and time are fundamental to the definitions of the laws, but prior to the big bang there is no space and time, so ours is the only universe of reality related to space and time ... IOW, it is impossible to experiment or produce data to verify the existence of other universes. Now if you mean to say branes instead of 'other universes' you may have a point there.