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From: ethan@utastro.UUCP
Newsgroups: net.physics
Subject: big banging
Message-ID: <246@utastro.UUCP>
Date: Mon, 7-May-84 08:58:49 EDT
Article-I.D.: utastro.246
Posted: Mon May  7 08:58:49 1984
Date-Received: Fri, 11-May-84 07:29:30 EDT
Organization: UTexas Astronomy Dept., Austin, Texas
Lines: 68

[It was a dark and stormy night.  Suddenly a bug rang out!!!!!]

This article is a reply to two questions by Jerry Aguirre and a reply
by Doug Gwyn.  First the questions:

>>1 - Is there any thing besides red shift to indicate that
	    the universe is receding from us?
	
>>2 - Have any alternate theories been proposed to account
	    for the red shift?

Now the first answer:

>1 - No, there is nothing other than the Hubble effect to indicate that
>distant objects are receding from us at a speed proportional to their
>distance from us, and then only if the assumption is made that the
>observed red shift is a Doppler effect.
>
The "assumption" that the observed red shift is a Doppler effect is just
the assumption that physics as we know it locally applies globally to the 
universe.  Probably not a bad assumption inasmuch as the spectral lines of 
distant objects are understandable in terms of familiar physics.

>2 - Yes, alternative explanations of the Hubble effect have been
>proposed.  Please note that the Hubble effect is predicted for the
>DeSitter cosmological model, which is the natural solution for the
>Einstein-Schr"odinger field equations.  The nice thing about this
>cosmology is that it describes a static universe (no expansion in any
>real sense) obeying the "perfect cosmological principle" (i.e. the
>universe looks the same (on a large scale) everywhere AND everywhen).

The DeSitter cosmological model has the property that two nearby particles,
separated by a spacelike interval and traveling along geodesics, will
exponentially diverge from one another.  This is as real an expansion
as you could possibly want.  This expansion is the reason that a Hubble effect
will appear in a DeSitter cosmology.  The "static" nature of the DeSitter model
is an illusion caused by an inappropriate set of coordinates introduced
by DeSitter.  The perfect cosmological principle is an attractive
suggestion.  However the discovery of quasars (indicating that the
universe used to contain a whole class of conspicuous objects that no longer
are common) and the blackbody background (indicating a earlier phase
of the universe's existence in which radiation and matter had a much greater
mean density) made it seem highly unlikely.  Whether or not the singularity
at the beginning of the universe (the big bang) has any real meaning is
open to question.  Presumably quantum effects (which would be important
during the first 10^^-43 seconds of the big bang) remove the singularity.

>Down with the Big Bang! 

Down with monday mornings! ( See. Anyone can talk like this :-) )

>Down with blindly applying General Relativity
>in domains where we know the field equations are wrong!  
 
We have every reason to believe that after the first 10^-43 seconds of
the universe's history we are on safe ground.  In any case the standard
model of the universe's early history does a bang-up job of predicting
the primordial abundances of elements.  Primordial nucleosynthesis
happens at an age of about 3 and a fraction minutes.


                     "Just another Cosmic Cowboy"
                         
                         Ethan Vishniac
                         {ut-sally,ut-ngp,kpno}!utastro!ethan
                         Department of Astronomy
                         University of Texas
                         Austin, Texas 78712