NetNews Usenet Archive 1993 #3/NN_1993_3.iso/spool/sci/astro/14280

Text File | 1993-01-22 | 3.4 KB | 71 lines

Newsgroups: sci.astro
Path: sparky!uunet!well!metares
From: [e-mail] (Tom Van Flandern)
Subject: Re: "Modeling" the Expanding Universe? (was Re: That Great Pulsar Timing Flame War)
Message-ID: <[e-mail]>
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Date: Fri, 22 Jan 1993 07:25:50 GMT
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Earlier, I wrote:

>> the solar system has about 20 orders of magnitude higher matter density
>> than the universe.  If much weaker matter densities will cause space in
>> the universe to eventually contract, why doesn't it cause space in the
>> solar system to contract now?  This does seem like an inconsistency to
>> me.

and [e-mail] (Patrick C. Mock) replied:

> This "inconsistency" is nonetheless predicted by GR and is consistent
> with the observations.

     I do not think this is true.  Einstein felt a need to invent a
"cosmological constant" (CC) in GR (a repulsive force) to prevent the
universe from collapsing.  When the cosmological redshift was discovered,
that eliminated the need for the CC.  Without the CC, the universe will
either expand forever, or eventually halt expansion and start contracting,
depending on the value of omega, the mean matter density of the universe.
In either case, the expansion *rate* must be everywhere the same, locally
or globally.  If you hypothesize that local matter density can cause local
spacetime to stop participating in the universal expansion, then local
matter density would cause local space to contract rapidly and violently
into a black hole (because it is 20 orders of magnitude stronger than
universal matter density).  It is clearly not possible to halt expansion
without starting a contraction.

> What is important here is that the observed behavior of the solar system
> is consistent with GR.  If there are new observations that contradict GR,
> I am not aware of them.

     There are none that I know of, and I doubt there ever will be.  It is
important to distinguish between observations that contradict GR, and
observations that GR cannot explain.  The four tests of GR have already
been confirmed, so observations that contradict GR would also have to
contradict previous observations.  Observations that take us beyond GR are
eagerly sought.  I do not see that the point we are discussing bears on GR,
one way or the other.  GR would still be GR if the big bang falls and
another quite different cosmology without universal expansion takes its
place.

> What seems clear to me is that you do not accept general relativity.
> Since GR is part of the foundation of big bang models, I would like to
> encourage the discussion to focus on the validity of GR.

     The big bang is based on GR, and not vice versa.  I do not accept the
big bang.  It is illogical to conclude that I therefore do not accept GR.

     There is a nice discussion of Einstein's Equation and its application
to the big bang in Wald's "Space, Time, and Gravity" (2nd ed., p. 48).  I
do not see how any of this answers my question:  why does large-scale space
with low matter density expand and later contract, while small-scale space
with high matter density does neither?  -|Tom|-

--
Tom Van Flandern / Washington, DC / [e-mail]
Meta Research was founded to foster research into ideas not otherwise
supported because they conflict with mainstream theories in Astronomy.