gravity question

[andytheplumb]

i here that gravity becomes weaker the further two objects move apart. if this is rite what happend at the beginning of time when all the matter we can observe was supposed to be crushed together to the size of a pin head how did it spread out like it has?

[fo3nix]

That's something people are still trying to figure out really.

Perhaps the best model of gravity so far is known as general relativity. It describes things that are huge in size very well, and things that are very heavy (lots of mass). It has problems however when things get very heavy and very small. This is the sort of situation you are talking about.

Another theory is quantum theory, that describes things very light and very small very (very) well. So the search is on to try and combine those two, so that we can theoretically see what happens in incidents like you describe.

[Clanad]

Current views suggest that matter, space, time, and gravity all interact and are directly dependent upon each other for existence. Since there was no matter at the instant of the "Big Bang, only energy, there was no gravity. The Universe was dominated by radiation. This means that the majority of the energy is in the form of photons and other massless or nearly massless particles (like neutrinos) that move at near the speed of light. As the big bang developed in time, the temperature dropped rapidly as the Universe expanded and the average velocity of particles decreases. Only then, (about 700,000 years into the event) could the phenomena of gravity come into existence with the formation of protons and electrons into hydrogen...
(Greatly simplified dissertation, by the way)

[fo3nix]

Clanad: gravity was there far before that. As long as there's particles with mass, i.e. quarks, electrons, and maybe neutrinos, gravity will be there.

[mibn2cweus]

As we study black holes and the big bang remarkable parallels are revealed, however, these parallels possess a mirror-like inverse nature. In a black hole gravity claims defeat over matter and energy, crushing, fusing and blending them into an apparently infinite density where time and space as we know them no longer exist in a form that we can observe or measure and thereby comprehend.

Beyond the event horizon of a black hole we are left to speculate as to what might be happening to that which it has consumed. Perhaps our universe, born in the big bang, is the only window we will ever possess to observe and witness what might take place beyond the event horizon of a black hole.

Up until now there remains a region that we are as yet not privileged to explore, the realm that lies between the singularity of a black hole and the singularity from which the big bang emerged. Perhaps energy is ultimately victorious in the end and the big bang is the manifestation of its temporary triumph over gravity. Until this can be confirmed or denied it is a race against the clock, for as far as can be ascertained, only time will tell.

presses submit and braces for the customary thrashing

[Clanad]

Possibly, fo3nix, however nothing existed at 10-^43 seconds into the event except energy, with which there was no gravity... the prevailing theory that I read describes a peculiar form of energy that can suddenly push out the fabric of space. At 10-^35 to 10-^33 seconds a runaway process called "Inflation" causes a vast expansion of space filled with this energy. The inflationary period is stopped only when this energy is transformed into matter and energy as we know it. This inflationary period ceased, primarily, due to the emergence of gravitons... the theorized particle responsible for gravity. The chances of detecting the graviton are slim because gravity is a weak force, which means gravitons carry little energy. The time line for the development of any of the fundamental particles and forces after the Big Bang is debatable... at least to this point... (With thanks to Science@NASA)

[jake-the-peg]

I'd have to agree that we cannot be very confident about how gravity behaved in the very early stages of the big bang. We simply have never been able to test Newton's theory in anything like those sorts of conditions.

I like the statement that the inflationary period ceased - with the discovery of dark energy the whole question of the inflationary Universe returns to haunt us yet again - If Einstein were alive he'd be ripping his hair out

[dawkins]

.It depends Andy.

General relativity predicts a gravitational singularity where all matter and energy are squeezed into a point infinitely hot, infinitely dense and infinitely curved. General relativity breaks down at this point as all forces including gravity are unified in the singularity

quantum physics cannot allow something as certain as a singularity so there is more wriggle room. A theory of gravity at the atomic level (quantum gravity) is possibly the biggest prize in physics. It is possible that a theory of quantum gravity could lead to a much better understanding of the birth of our universe and lead to a grand unified theory (the, so called, theory of everything).

At the moment, though, very little is known about conditions in the very early universe Very little is actually known about inflation (simon singh calls inflation a hypothetical phenomenon). What we do have is a lot of speculation but we await the next big breakthrough

[jake-the-peg]

If simon Singh thinks inflation is a hypothetical phenomina he needs to talk to Alan Reis.


His team's work on supernovae showed the universe is not only expanding but the expansion is accelertating and kicked off the whole dark energy thing

That's now not during some time seconds after the big bang.

Now I know that the rate of expansion we see now is nothing like those predicted during the inflationary epoch but until there's a half decent explanation of dark energy dismissing inflation as hypothetical is rather unwarrented.

Maybe it is hypothetical or maybe Reis has given us evidence for it

[dawkins]

Jake-the -peg

Yes I agree jake. the point I was making was that in any discussion about the big bang model we must recognise that the model itself is still very much work in progress. Inflation explains many puzzles of the big bang model including the similarity of the universe in any direction and its apparent flatness and the way it grew so quickly; but inflation (the rapid expansion in the very early big bang 10-35) is still a hypothetical in physics terms (strange as that may seem). I don't think Singh was doubting inflation I think he was mearly pointing out the way science works.