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surreptitious57 wrote:If branes exist in spacetime then it must have existed before the Big Bang otherwise it could never have happened.

Well, see Pulsar's post below, but I might have been wrong about the implication for brane-worlds, but in that model, they didn't exist in spacetime, spacetime existed on the brane.

They must be incredibly unstable if their collision results in the creation of an entire Universe.

Stability wouldn't have much to do with it, their collision simply imparts the energy.

Could dark energy therefore be the result of that collision ? That would explain why the Universe is still expanding.

Well, it looks unlikely in light of Pulsar's post. In any event, the best candidate for Dark Energy is, IMO, simply gravity.

Dark matter could be undetected matter from the collision also.

Well, in that model, dark matter is just matter that resides on the other brane, though that looks unlikely now.

If inflation falsifies this then we now know what the other ninety six per cent of the Universe is composed of.

Ummm, how? Not sure I get you.

Though other Universes shall remain immune to detection. Though if this one keeps expanding at the rate it does then local space will at some point be devoid of virtually all light because the only visible star will be the Sun. And all of this from a single physical reaction over thirteen billion years ago. It is therefore not too grand a statement to say we owe our very existence to quantum mechanics

It isn't too grand a statement anyway.

I remember watching a BBC Four documentary last year about explanations for the origins of the Universe [ the one where Lee Smolin and Roger Penrose and Neil Turok were each given a Rubik Cube to solve ] and the brane collision was one model on the table. Now with falsification someone should get a Nobel because it is that significant.

Not sure about that. The brane-worlds model was a fringe model, in reality. I liked it, because it was somewhat elegant, but there you go. The documentary was an episode of Horizon entitled What Happened Before the Big Bang, and IIRC, it was a wooden puzzle rather than a Rubik's Cube.

I think it would be very unfair for it not to go to Andrei Linde as it was he who originally suggested it.

He's certainly one of the names being mooted, but if the discovery of the CMBR is anything to go by, possibly not. Penzias and Wilson won the Nobel for that discovery and they weren't even looking for it. They thought it was pigeon shit in the antenna!

And this coming so soon after the discovery of the Higgs two years ago. Which is very unusual indeed now as the Universe does not usually give up its secrets that frequently So anyone who is a physicist or has an interest in physics is very fortunate indeed to be living in these times. I for one shall definitely be trying to learn more about it and specifically cosmology in light of this fantastic discovery

Heady days indeed.