The fate of the Universe - big rip, then big crunch?

[DavidGahan]

I envision the Universe to be like a stellar sized star. When it expands, it explodes into a supernova, then collapses/contract into a black hole singularity. Since the Universe rate of expansion is accelerating, would it rip apart, and then contract into a singularity, just like the star?

 

[n1person]

Perhaps the main issue with this sort of logic is that, unlike an exploding star, current theories do not envision a sort of large "explosion" like impulse for why the universe is accelerating. It is, instead, the effect of dark energy (which can be viewed many ways, one of which is an intrinsic property of volume/space) where the "force" of the expansion is always present. So there isn't necessarily going to be a "crunch" per say because the force of the expansion will continue what is it doing continuously. The force of gravity will not increase as the universe expands.

Your model sort of relates to an idea of a de-accelerating universe, where there was a "big rip" type event (the big bang) and it will eventually contract (big crunch). This view is not supported by observations.

So, in summary, star: big impulse, no continuous force/driver for expansion, universe: continuous expansion force.

 

[bcrowell]

I envision the Universe to be like a stellar sized star. When it expands, it explodes into a supernova, then collapses/contract into a black hole singularity. Since the Universe rate of expansion is accelerating, would it rip apart, and then contract into a singularity, just like the star?

This doesn't make much sense. If you spell out your reasoning more, we might be able to help you get past some confusion about the big bang and cosmological models.

 

[bapowell]

Your model sort of relates to an idea of a de-accelerating universe, where there was a "big rip" type event (the big bang) and it will eventually contract (big crunch). This view is not supported by observations.

I think you've misspoken. The Big Rip is the hypothesized end state of a universe that undergoes 'super'-acceleration -- acceleration described by an equation of state w < -1. In this scenario, the energy density of the universe grows with time (rather than remaining constant as it does in dark energy models) with the result that there is 'run away' acceleration -- eventually on all length scales. When the density grows to the point where homogeneity is achieved even on small scales -- like solar systems, people, atoms -- even these bound structures are pulled apart by the expansion. The Big Rip is not like the Big Bang -- it is a future singularity. It also may not eventually contract, that is a model dependent statement.

With respect to observations, this view is still in agreement with the latest constraints on w and dw/dz, the variation of w wrt redshift.

 

[AG Systems]

I heard that many galaxies are heading toward a 'known' black hole. This might affect everything of what we think of the Universe...
Sorry, correct me if I'm wrong, I'm new here...

 

[bapowell]

I heard that many galaxies are heading toward a 'known' black hole. This might affect everything of what we think of the Universe...
Sorry, correct me if I'm wrong, I'm new here...

Welcome AG Systems. Are you referring to the Great Attractor? Or perhaps the more recent discovery of the 'dark flow'? As far as I know, neither of these involve black holes; the Great Attractor is most probably a supercluster, and the cause of the 'dark flow' is currently unknown, and the finding itself is controversial. However, even if galaxies were heading towards a known black hole, I doubt this would effect everything of what we think of the universe -- which is a pretty grand statement, and since all the physics involved is quite well understood.