Could the big bang be in a repeating cycle?
My understanding of the big bang, is that we started off with one large mass which contained all material.
This then exploded outwards and is still expanding.
Is there a point in the future where the expansion will stop and everything will start returning to one large mass and in so doing start another Big Bang? If this is the case, are we sure that our Big Bang was the first and only one, and it not part of a repeating cycle?
Astronomer Gerry Gilmore got to grips with this BIG question...
Gerry - That's a pretty big question just to sneak in like that Chris! The answer in principle is yes. We have a model, a description of cosmology and the origin of the universe in which the universe started as an infinitesimally tiny volume with a very, very large amount of energy in it indeed. This energy is actually from nothing, expanded very rapidly, much, much faster than the speed of light, for a longish time by its standards, about a millionth of a second by our standards. And that led to an universe that was incredibly stretched out and incredibly huge, and a teeny, teeny part of that original universe is what we see as our universe today.
Now that picture, when you plug it into Einstein's general relativity, provides an excellent description of all our observations, but it makes no sense at all. You have to make up all sorts of assumptions; you have to guess why numbers are the way they are. So that may be right but it's clearly not a complete description. We don't have a quantum gravity description of what really happened in those early days and so people are investigating all sorts of possibilities, even though there's no evidence, direct evidence as yet for it. One indeed, which in the jargon is called ekpyrotic, which is this idea that the universe is a repeating cyclic event and so we are on generation X of the universe.
So, as I say, there's no evidence for this but the current evidence is that the universe is accelerating its expansion and will accelerate into a universe of essentially nothing. So we've gone from intense concentration to intense cold permanent death, which is pretty dreary.
Chris - So it's blowing up and getting bigger but, the older it gets, the faster it grows?
Gerry - It's going faster rather than slower, yes. The weight of the universe ought to be slowing it down but something else is out there speeding it up. We don't know what this other stuff is. It's probably something similar to what happened in the very first instant of the universe - it's called inflation for obvious reasons. That inflation stopped, maybe this one will, maybe it'll turn round. Current lack of knowledge is that no that won't happen and bad luck, this is just all we've got. But it's quite possible, in the far future, the universe will be a much, much more interesting place than we think it will be today.