Re: [asa] Cosmologists questioning the Copernican principle?

Much of the puzzlement that theoretical cosmologists express these days in
connection with the accelerating expansion of the universe is due to a
takeover of the field by physicists whose background is in nuclear &
particle physics & quantum field theory rather than general relativity. It
may in fact be that the acceleration has nothing to do with quantum vacuum
energy but is rather the result of a small but nonzero cosmological constant
which is in fact a fundamental constant of nature, a possibility allowed by
traditional general relativity. (& of course the old story of Einstein
introducing it for the wrong reason & then saying it was his "greatest
blunder" will be trotted out - but so what? Maybe he was wrong - as a
number of respected GRT folks always insisted.)

This still leaves unanswered the question of how the huge quantum vacuum
energy which would lead to a huge cosmological constant gets suppressed.
But we already know that somehow a fraction (10^120 - 1)/(10^120) of it is
suppressed, so it's not a big stretch to say that all of it is. & it's
likely that the cosmological "constant" isn't really constant, but it's
better to start with an estimate that's off by a factor of oirder unity than
by one that's off by a factor of ~120%.

Shalom
George
http://home.neo.rr.com/scitheologyglm
----- Original Message -----
From: "Iain Strachan" <igd.strachan@gmail.com>
To: "ASA" <asa@calvin.edu>
Sent: Tuesday, November 25, 2008 3:50 AM
Subject: [asa] Cosmologists questioning the Copernican principle?

>I was quite surprised to see the following New Scientist article:
>
> http://www.newscientist.com/article/mg20026821.200-is-earth-at-the-heart-of-a-giant-cosmic-void.html?full=true
>
> The gist of the argument is as follows. Dark energy has been proposed
> as an explanation of the apparent accelerating expansion of the
> universe (as illustrated by distant type 1A supernovae being fainter
> than expected). However (as I understand it from the article) the
> theoretical predictions of the quantity of Dark energy are out by 120
> orders of magnitude, implying an incredible degree of fine tuning.
>
> The alternative (for which the article describes potential experiments
> to test the theory) is to propose that the earth is in the centre of
> an enormous cosmological "void" ( comparatively sparsely populated
> region of space) surrounded by denser material. It should be noted
> that this "void" contains most of the observable universe! This would
> violate the Copernican principle of the earth being in no special
> place in the cosmos, but would exhibit isotropy ( universe appears the
> same in all directions - uniformity of the Cosmic Microwave Background
> Radiation), while requiring the earth to be near the centre (thus
> violating the homogeneity assumption - the structure of the universe
> varies with distance from the centre). One quote from the article
> seems to sum it up well; we live in a very improbable universe, and
> the new proposal trades one improbability (Dark Energy) for another
> (Earth near the centre).
>
> I would have thought that Young Earth Creationists would be very
> excited about this. However, I emailed a former colleague who is a
> YEC & he was less than excited; the article had been passed round
> creationist circles, but there was not much comment. He felt that the
> New Scientist article, as always, was too hyped up. (However, there
> are also positive discussions of it on the Richard Dawkins website as
> well).
>
> I'm not a cosmologist, but it appears to me that to invoke some
> mysterious form of energy, the nature of which we don't know, and
> state that it comprises around three-quarters of the material in the
> universe, in order to explain some observations that don't fit with
> the standard model seems a little like a desperate fix and just shows
> how little we really know. Perhaps some cosmologists on the list can
> explain if there is other, independent evidence for the existence of
> dark energy. Otherwise to invoke something we know nothing about to
> explain observations we can't otherwise explain seems about on a par
> with the Intelligent Design argument (which I think is a cop-out).
>
> What do others think? I know the New Scientist is given to hype. Is
> this just another case of it?
>
>
> Iain
> --
> -----------
> Non timeo sed caveo
>
> -----------
>
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Received on Tue Nov 25 08:12:21 2008