Naked Science Forum

Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: Julian Sun on 01/12/2009 21:30:04

Title: Does gravity exist in the absence of space-time?
Post by: Julian Sun on 01/12/2009 21:30:04

Julian Sun  asked the Naked Scientists:
   
HI Chris,
 
My name is Julian from South Africa. I was watching a programme about Stephen Hawking and finding a unifying theory in Physics. My question pertains to the Big Bang.

If the universe started with the Big Bang, from an exploding singularity, how could the singularity exist when the fabric of space-time had not been formed yet?

As I understand, a singularity is a point of infinite density and infinite mass which warps the fabric of space-time because of its immense gravity. I suppose my question could be summarised as by asking, does gravity exist in the absence of space-time?
 
If that question is a little too dense to answer, please let me know how statisticians work out that human beings swallow on average, 7 spiders whilst asleep during our lives?
 
Thanks
 Julian Sun

What do you think?

Title: Does gravity exist in the absence of space-time?
Post by: Mr. Scientist on 01/12/2009 22:07:10

Gravity is the presence of matter, and since matter resides as a longer-lived fluctuation of energy, it seems that matter and spacetime are in fact one thing. You cannot have therefore gravity without a vacuum - whether that specific gravity is fundamental or not.

Title: Does gravity exist in the absence of space-time?
Post by: Mr. Scientist on 01/12/2009 22:12:15

There is however something called a pure gravity solution, which is a mathematical consequence of relativity... a lot of details, but essentially, it attempts to describe a solution to a vacuum where no matter or gravity or energy exists. But among many people like me, think it's actually an indication that relativity mathematically-breaks down somewhere...

Title: Does gravity exist in the absence of space-time?
Post by: Mad Mark on 02/12/2009 01:11:18

That's probably why the singularity went bang!
That could well be the triggering point for a singularity whether it evolved out of a previous collapsing universe or came into existence from a point in the multiverse. Either way unlike singularities from collapsed stars with their event horizons our singularity at the beginning had no horizon and at that point it gave up all its information.

Title: Does gravity exist in the absence of space-time?
Post by: Mr. Scientist on 02/12/2009 01:22:57

No, the triggering point of big bang is GREATLY due to the uncrtainty principle.

Imagine all the matter in the universe. There is about 10^80 particles in the obervable universe. Imagine trying to cram eah and every one of these particles into a size smaller than a blood cell! That's still not enough.... imagine they have been crammed so tightly together that its just one tiny point of pure energy... That would mean an infinitely high-energy, but equally stressing both position and trajectory states. If you like, those particles which tried to move at the very first instant of big bang was equally due these particles trying to find new locations in respect of each other.