Science Questions

Could the big bang be in a repeating cycle?

Mon, 16th May 2016

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Bob asked:

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...Big Bang

Gerry - Thatís 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 itís clearly not a complete description. We donít have a quantum gravity description of what really happened in those early days and so people are investigating all sorts of possibilities, even though thereís 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, thereís 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 weíve gone from intense concentration to intense cold permanent death, which is pretty dreary.

Chris - So itís blowing up and getting bigger but, the older it gets, the faster it grows?

Gerry - Itís 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 donít know what this other stuff is. Itís probably something similar to what happened in the very first instant of the universe - itís called inflation for obvious reasons. That inflation stopped, maybe this one will, maybe itíll turn round. Current lack of knowledge is that no that wonít happen and bad luck, this is just all weíve got. But itís quite possible, in the far future, the universe will be a much, much more interesting place than we think it will be today.



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I think the notion of a Big Bang is incorrect. I think our Universe is part of an ongoing process. It's the Big Ongoing.

Our visible Universe is a larger version of what is represented by the blue lines in the following.

'Supermassive Black Holes Transport Matter into Cosmic Voids, Astronomers Say'

At the scale of our Universe the energy referred to above is dark energy. A Universal black hole is powering our visible Universe causing the galaxy clusters to accelerate away from us. stacyjones, Thu, 5th May 2016

Einstein's General Relativity predicted that gravity should slow the expansion of the universe. Whether gravity would actually reverse the expansion of the universe depends on the average density of the universe.

Many scientists (including Einstein) considered that a cyclic universe was possible.

However, the discovery of Dark Energy suggests that the expansion of the universe is accelerating, not decelerating. So Einstein's view of a gravity-driven cyclic universe now seems less likely.

But there are several other (more modern) hypotheses that may result in a cyclic universe, including speculation about the possibility of additional unseen dimensions.

See: evan_au, Fri, 6th May 2016

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