Re: [asa] Cosmologists questioning the Copernican principle?

Thanks for the reply, which should provide me more material to look up
about this fascinating subject.

However, in your opinion, do you think that the New Scientist is just
indulging in journalistic hype in order to make a sensationalist
article? (It is pretty sensational nowadays to give any credance to
the idea that the earth, or at least the solar system or our galaxy
are at the centre of the universe). Interestingly, to get round the
"specialness" of the position, one of the people on the Richard
Dawkins forum proposed a "crunchie bar" model, where our "bubble" is
just one of many in a honeycomb; however given the vast size of the
void, it still appears to be a coincidence if the earth is so close to
the middle of one of the bubbles.

Iain

On Tue, Nov 25, 2008 at 1:11 PM, George Murphy <GMURPHY10@neo.rr.com> wrote:
> 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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-- 
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Non timeo sed caveo
-----------
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