[ExI] Expansion of the Universe

BillK pharos at gmail.com
Sat Dec 29 22:17:04 UTC 2012

On Sat, Dec 29, 2012 at 8:19 PM, Ben Zaiboc wrote:
> Maybe not necessarily.  What always occurs to me when I read about the expanding universe,
> is the possibility of something analogous to sound waves in air, applied at a hugely huger scale.
>  Maybe the universe is reverberating to the big bang, or some similar long-ago event, and we
> are currently in the expansion phase of a universal 'sound-wave'.  Maybe in a few billion years
> the galaxies will start compressing together again, then in a few billion years after that, expand
> again, etc.
> Any theoretical objections to this idea?  I've never seen it discussed.
> (Note that this is different to the 'periodic big bang' idea.
> It's much less dramatic, just a periodic change in the density of the universe, like sound waves in air).

You should always try to ground speculation on current science
knowledge. If you invent something that is purely speculative then you
might as well say God did it, as you can assume anything is possible.

The expansion of the universe seems to be driven by dark energy
(whatever that is!).

So there are three options.
1) Indefinite expansion. Dark energy carries on expanding as we see it
operating now.
This is the favourite option as there is no known reason for it to
change behaviour.
2) Big Crunch. Dark energy reverses and starts collapsing the universe
back to a point.
3) Big Rip. Dark energy gets stronger and keeps on increasing.
This scatters everything quicker and quicker.

Ethan Siegel wrote about this in 2011.
(Ethan is a professor and theoretical astrophysicist and does this
sort of thing for a living).  :)


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