Well, this question has come up before among a circle of my friends, sitting around being contemplative late on a Saturday night. Of course, none of us knew the actual answer, but that didn't stop us from giving the matter some thought.

The view we settled on in that discussion went like this:

Space itself is infinite, but the matter in it is not. So when we talk of "the universe," are we talking about space, the matter in it, or both? That's the first thing to settle. We decided that it's both, since "the universe" is defined as everything that exists.

So then we decided that when people talk about "the expanding universe," it's really a misnomer, or maybe a convenient shorthand, for the concept of "the expanding of finite matter into an infinite space."

Which makes sense when taken together with the Big Bang theory (if one accepts it): all the matter that exists started in one place, and bang, it started expanding outward into the infinite empty space... and it is still expanding outward.

I have even heard a theory that states, at some point, all the matter will stop expanding and start falling in on itself again, leading to another Big Bang. Which further suggests that we may not be in the middle of the "first" Big Bang, but that it's a zillion-year-long cyclical event that may have already happened many, many times.

I think it's just tough for us little finite creatures to really understand the concept of infinite space. I mean, everything we deal with has edges to it. There is a place where an object stops, and something else starts. So, it's sort of natural for us to wonder, "What is beyond the edge of space?"

But if space is truly infinite, it doesn't stop or start, it has no edges. It is EVERYTHING... and that means it doesn't expand. Which is just totally alien to our everyday frame of reference.

Phew. Thinking is good exercise.
Thanks for the opportunity, Kat.

Thanks for your thoughts forester.

Your conclusions seems to be the more popular consensus among people who have put this problem to thought. But the paradoxes bug me.

I'm not truly sure how you would call something infinite 'everything' because infinity connotes that it is incomplete. I don't see how you can reconcile the idea of a totality of all things existing when existence simply has no end. The very idea behind the concept 'totality' is that it is within closed borders; a complete system.

Likewise, infinity would not only deduce infinite space but infinite probability. Meaning, in an infinite number of time in infinite space, every possibility will inevitably happen at some point (See also infinite monkey theorem). No concept or idea is excluded from being true because an exclusion of a single digit would of course negate the concept of infinity (all possible outcomes). So, inevitably, does this mean that the outcome that space is finite is true at some point in time in some point in space? Does this also mean that the outcome that existence doesn't exist at all become true? Like I said, the paradoxes bug me.

Maybe I'm just trying to understand with my primitive mind the intangible concept of infinity. Who knows; after all, for one to truly know infinity, it would take a brain infinitely large wouldn't it?

Children were encouraged to develop strict discipline and a high regard for sharing. When a girl picked her first berries and dug her first roots, they were given away to an elder so she would share her future success.
Native American Quotes Mourning Dove Salish

And while I stood there I saw more than I can tell and I understood more than I saw; for I was seeing in a sacred manner the shapes of all things in the spirit, and the shape of all shapes as they must live together like one being.---Black Elk


The Yardbirds-Shapes of things
The Yardbirds-Shapes of things

Strangely enough, this cropped up on another board I post on (BC). There's an article in New Scientist about the possibility of consciousness arising spontaneously through quantum fluctuations - the full article is here:

Spooks in space - cosmology - 17 August 2007 - New Scientist Space

What I find interesting is that it's atheist scientists discussing this possibility, which on the face of it seems just as weird and supernatural as a deity existing.

The basic idea is this: virtual particles pop in and out of existence all the time. In theory, there's nothing to stop a rock, a small office table or a conscious entity popping into existence - although the more complex the structure, the longer the timescale required. 13 billion years is far too short a time for the spontaneous emergence of a conscious entity to be likely, but in an ever-expanding universe that goes on for ever, such entities will eventually occur, and will probably be the *only* form of matter that exists in the universe after all the protons have decayed 10[sup]32[/sup] or so years from now.

The discussion on BC is here - I don't know if it's considered bad form to post links to another forum, but BC and DtT are on good terms and share the same server, so I hope so - but mods, please feel free to remove this link and accept my apologies if it isn't appropriate:

BC Forums

Incidentally, to answer your specific point about what the universe can expand into, the Kabbalah (mystical Judaism) has the interesting concept of "tzimtzum", meaning contraction.

It works like this: in the beginning, there was only God. No room for anything else, so to bring the rest of creation into existence, God contracted a tiny part of him/her/itself to produce a void, no bigger than a mustard seed.

This tiny seed then grew, so that everything that was, is and will be in the universe was contained within that tiny, expanding seed.

God lies outside this seed - our universe - in the Ain Soph Aur (the limitless boundless light).