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Interesting quote from Hawking.

A couple of nitpicky questions, since it sounded like he was handwaving...

"The answer is that, in quantum theory, particles can be created out of energy in the form of particle/antiparticle pairs. "

I was under the impression that the lifetime of the particle/antiparticle pairs was inversely related to their mass.

IF I remembered that correctly,
AND IF it applies in this context,

...how does such a massive universe have such a long lifetime?

"In the case of a universe that is approximately uniform in space, one can show that this negative gravitational energy exactly cancels the positive energy represented by the matter. So the total energy of the universe is zero."

This sounds like hand waving. How 'uniform' is 'approximately enough' uniform for the cancellation to be exact?

Did the uniformity of the Universe change since the big bang, due to inflation?

And (just to be annoying) what happens if the uniformity of the Universe exceeds the threshold for the cancellation of negative and positive energy? Do you get an analogy to the "time traveler shooting his own grandfather" paradox?

And two more questions, in the vain hopes of getting someone to post a picture of Lisa Randall:

1) Are these predictions affected at all by the number of extra dimensions predicted in various string theories (as certain dimensions are "rolled up" into really, really, tiny volumes)?

2) Why did inflation (apparently) only affect the specific macroscopic dimensions we see now, and not the others?

Full Disclosure: Yes,I'm procrastinating on my exercise again. Buhler?....Buhler?

Cheers!

Did the uniformity of the Universe change since the big bang, due to inflation? Chirality of the universe indicates that uniformity was broken early on, just after dimension space and dimension time first manifested and that manifesting is likely waht caused the energy necessary for the inflation period. Inflation didn't end abruptly, but tapered off rapidly by an inverse square rule once an 'event horizon' was reached (kind of like a reversed black hole).

1) Are these predictions affected at all by the number of extra dimensions predicted in various string theories (as certain dimensions are "rolled up" into really, really, tiny volumes)? If you read Randall's book (Warped Passages) you will find info on this rolled up dimension effect that may be detectable when the LHC comes on line. Basically, if the indication of KK particles (Kaluza Klein particles) pans out it will be a strong indicator of extra dimensions.

2) Why did inflation (apparently) only affect the specific macroscopic dimensions we see now, and not the others? At least two dimensions, both of which are experienced on macroscopic and microscopic levels, were 'effected' by the inflation period (three, four, or five variables of those two dimensions) ... space and time became intertwined and energy was bound in space and time as subatomic particles, manifesting as particles and as the quantum field in which all of space and time exist now.