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Very good arguments, Sophie. If your teacher is any sort of teacher...and a scientist, he'll think long and hard about your conversation. It should make him think and read up on the latest papers.
I won't go into the maths for the current theories...I have a hard enough time trying to follow it myself, but I'll try and explain to you one of the ideas they have now. It's called M-Theory....don't ask me what the M stands for because no one else does. Call it "magic" if you will. Anyhow, it was proposed by a physicist named Edward Witten from The Institute for Advanced Studies at Princeton University, back in the early 80's. What he proposed is that our universe, which they believe is made up of extremely tiny vibrating packets of energy, called strings (have you heard of String Theory??), is nothing more than a 4D (3 physical dimensions and 1 time dimension) surface of a much larger, multidimensional object, called a "brane" or membrane. Now, what this membrane is, so the theory goes...is a string that has stretched itself out into a flat surface, a membrane (or brane) which lies in a higher dimensional hyperspace. Now in that higher space, there are also other membranes, other universes if you will. Every now and then (probably over many trillions of years) these branes which are floating about in this higher space collide, and it is this collision which is the "Big Bang". After the collision, the branes rebound and move away from one another. Now, whilst time and space may appear to have come into existence on our own particular brane at the Big Bang, in actual fact (according to theory) what happens is that time and space merely reach a bottleneck. What in fact occurs is that time and space from the previous cycle of expansion comes to that bottleneck and then a new set of conditions occurs for the next cycle of expansion with little or no information from the previous cycle coming through to the new one (as far as we know. There maybe some informtion which slips through). There is no "Big Crunch" so to speak. At each expansion phase, the universe which forms in the brane keeps on expanding until it becomes completely smooth and homogenous in its internal structure i.e. nothing but spacetime left, not even electrons, protons or quarks!!!. Spacetime itself keeps expanding until the brane in which it sits collides again with another brane, everything becomes reset instantly and a new set of conditions arises in the brane, generating another cycle of expansion for a new universe in the brane. Hard to visualise?? Think of it like this...take two pieces of paper and bang them together, then scrunch one of them up. Then over an hour, say, gradually unfold and smooth that bit of paper out. Once you get it as smooth and flat as you can, bang the two bits of paper together again, then scrunch that piece back up. Do the same process again and again and again...indefinetly. That's a rough analogue of what happens, according to theory.
It's late and I hope I've made some sense to you (hard to think when you're tired!!!). But if you need anymore explanatory notes, just ask. Or one of the other guys might take it up...(keep it easy, hey!!).
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