[ExI] Expansion of the Universe
bbenzai at yahoo.com
Sun Dec 30 18:05:45 UTC 2012
Anders Sandberg <anders at aleph.se> wrote:
> On 2012-12-29 21:19, 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.
> > Any theoretical objections to this idea? I've
> never seen it discussed.
> You are essentially arguing that the large-scale metric is
> dominated by
> the Weyl part of the the metric tensor (gravitational waves)
> and that
> the universe is not isotropic. I think some people have
> looked at it,
> since the standard models are isotropic, but there is *no*
> evidence for
> very large scale anisotropy. The closest things are hints
> that there
> might exist some weird twists and axiality to large-scale
> spacetime, but
> I have not seen any follow-up from the original claims.
> What you suggest is very very large scale isotropy, so that
> wavelengths are large enough not to be visible to us right
> now. I don't
> have enough "feel" for the Friedman equations to tell how
> this would
> play out. But I suspect the isotropic and homogeneous
> expansion would
> swamp the waves: they become more dominant in collapsing
> universes, so I suspect the opposite would be true for an
Thanks, Anders, that's the kind of answer I was looking for (even though I didn't really understand it!).
So there are sound theoretical reasons (pun intended) why this idea is a non-starter. OK, that's good enough for me.
More information about the extropy-chat