Quote:
Originally Posted by OneArmedScissor
Ok... I just got into a long discussion with a friend of mine as to whether or not the universe is infinite or finite.
I said it was sort of a mixture of both. Like a sphere inside itself. Or something you see off in the distance, but no matter how fast you run or travel, you'll never get to it.
His argument was that the universe was infinite... That it goes forever with no ends, etc.
Basically, my whole point was that it was neither, but shared properties of each (infinite and finite). His whole argument was that, "since you can never get to the end of it, that means it's infinite." Anyways, any inputs would be appreciated!
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This is a convoluted problem as this thread implies.
1. First off, there has been a lot of "evolution" of thought regarding universe's size, BBT, etc. A lot of what has been said is from all sides.
2. Data from WMAP has been a reversal if not an overall revolution of thought of how the
universe is composed (new types of matter has been created - paradigm shift to account for it).
Said in the simplest of form, I think your answer might be closest to the truth (if there is a truth).
In the original BBT from Gamov, Bondi, et al was the presumption "everything" started
from one event (point). Implicit assumption with this was that the universe was
"closed". That there was enough matter to close the universe and eventually as Hawking
says "end in the Big Crunch". The original BBT back was finite-like.
WMAP changed all that. The data from WMAP now implies that the universe is accelerating
outward not "just" expanding. This forces a Hyperbolic geometry not Riemannian.
Another "monkey-wrench" was in late 60s - 70s when Wheeler proposed the notion of
"Bubble" universes expanding in a Multiverse, so that even if our universe were finite,
the Multiverse would be infinite. -- Beginning of his Quantum Foam idea.
From then on BBT models didn't make the assumption of finite expansion. Instead what
papers I've read talked of an arbitrary expansion. In some of the papers in the concluding remarks
were speculation of this expansion embedded whithin something else. Even Hoyle's
reinvented Steady State Theory (I got to meet him in a talk at Indiana University 1976)
before he retired spoke of such an embedding (ie, finite & infinite). I am speaking of the
period before Alan Guth's work on Cosmological Inflation (pre-1980).
So EWright is somewhat correct that BBT doesn't require finite (not any more). It just
doesn't state either way anymore. Current discussion of finite was thrown out with the
proverbial "bath-water" when Closure is no longer considered likely.
To also speculate what is "beyond the boundary" (of expansion) is on unfounded turf.
You can not really go there with any authority. So whether is even there or not is beyond
your purview. With that I kinda' go along with JA Wheeler and consider Bubble Universes, Multiverse, etc.
maddog
