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Re: infinite universe

Subject: Re: infinite universe
From: John Bailey
Date: Sat, 04 Mar 2006 15:27:45 GMT
Newsgroups: sci.astro, sci.physics
On 3 Mar 2006 21:21:59 -0800, RadicalLibertarian@xxxxxxxxxxx wrote:

>Amazing stuff.
>
>But I dont think that the $145 was a complete waste. As long as the
>null result is remembered it retains it's value.
>
I didn't mean to say it was a waste at all, just that it is an
expensive null experiment.  Michelson-Morley, which provided the null
data on which Einstein based special relativity was cheaper by two
orders of magnitude.


>I dont see why similar circles should neccesarily be located in exactly
>opposite directions. I think that this is not really being realistic.
>What they need is a massive deepsky survey, and software to look for
>correlations anywhere in the sky. Map the things that look reasonably
>similar in various parameters.

(quote)
Unfortunately this approach is complicated by the fact that the
different images will present the object at different epochs in its
evolution, at different distances, at different redshifts, with
different reddening factors, and from different perspectives. (end
quote) requoted from the reference below.

The approach is further complicated by the combinatorial mess that
results.  For every object that may have an earlier virtual image, the
analysis must consider the possibility that every suitable virtual
object is considered. In this case, suitable means the object could
have evolved from where it was a few billion years earlier to the
current apparent location.  The problem rapidly becomes one that
resembles the operations research nightmare of finding the shortest
route for a salesman, a well-known NP complete problem.  (reference:
M. R. Garey and D. S. Johnson, ?Computers and Intractability: A Guide
to the Theory of NP Completeness,"  W. H. Freeman and Company, San
Francisco, 1979.)


The above quote is from:
Circles in the Sky: Finding Topology with the Microwave Background 
Radiation by Cornish, Spergel, and Starkman 
rXiv:gr-qc/9602039 
In a multiply connected universe, many null geodesics start from the 
position of an object and reach the present observer. Thus there will 
be many images of each object, often called ghosts. Many authors have 
sought to use this fact to limit the scale of the topology by 
searching for multiple images of recognizable objects. Unfortunately 
this approach is complicated by the fact that the different images 
will present the object at different epochs in its evolution, at 
different distances, at different redshifts, with different reddening 
factors, and from different perspectives. In all but a flat geometry, 
the images will also be stretched or compressed differently. 



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