Re: Gravity and levity

[Reposted without spam block in with some additions to the text.]
In article <[EMAIL PROTECTED]>, Ulf Torkelsson
<[EMAIL PROTECTED]> wrote:

>>Suppose, for a start that the universe is made up by a series of globs,
>>each limited in size by the GR estimate GM/(c^2 r). Then this formula
>>would also act on the globs attracting to each other. It means that no
>>matter what the glob density is, the universe cannot be homogenous.

>>So this perhaps suggest that in such a case there should be another force
>>"levity" that counteracts gravity. This might be a an Einstein
>>cosmological constant or something or some other force. But this force
>>should be so that in the very large of the universe, the estimate GM/(c^2
>>r) is properly counteracted.

>  In the last paragraph here you reason the same way as Einstein did
>when he introduced his cosmological constant.  Gravity is always
>attractive, so in order to get a static universe he was forced to
>introduce the cosmological constant to counteract gravity on large
>distance scales.  If you do not assume that the universe is static
>the cosmological constant is no longer necessary, and we can for
>instance get an expanding universe in which the expansion is
>gradually slowing down due to the effect of gravity.

The reason that I end up with the gravitational constant perhaps in
combination with other expanding "levity" forces is that I experiment with
the idea of a universe that is stable over time in terms of size, but with
a lot of "cosmological convection".

>  If we keep
>the cosmological constant, but allow the universe to change
>over time, it turns out that the static solution is unstable, and any
>perturbation will either cause it to contract or expand.  The
>interesting thing here is that the expansion can eventually become
>exponential if we do have a cosmological constant.

Suppose I experiment with a glob universe with essentially homogenous
overall large scale density. Then the formula GM/(c^2 r) sets the size
limit of each glob. Our glob, by your estimate, would roughly be the size
of the currently observed universe. But this would not work with many
globs interacting, so GM/(c^2 r) would need some levity counteracting on
that very large scale level.

Within each glob, like our currently observed universe (which might be the
only glob there is), there must be some levity force that explains the
expansion of the visible matter. This is another force at different length
scale it seems. Big Bang theories says that this force is the result of
the Big Bang.

Those ideas would not be needed if there is only one Big Bang created
universe, evolving as fast as one assumes now. But I have vague memory
that some such models also need a cosmological constant or such.

I am not sure whether it should be a cosmological constant: If you say
that a cosmological constant may cause solution instability and even
exponential behavior in that respect, that sounds as the wrong way to go.
So perhaps one should experiment with other types of levity forces. But I
do not know what these forces might be.

I do not recall exactly how the cosmological constant is put into the
Einstein-Hilbert equation: If it is just a constant, perhaps one should
experiment with a more dynamic components, like if the universe becomes
too large, this constant diminishes.

One radical way that comes to my mind is to assume that lit matter has a
weak levity force, say somehow created by the QM effects going on in it.
Then lit matter would have a weak outwards force not present in dark
matter, and the universe would start to convect.

The funny thing is that such GR extensions might easily be generated: The
Einstein-Hilbert equation is produced by a metric variation in a certain
Lagrangian, which is the sum of the Ricci scalar curvature and some other
components associated with the observables. If this Lagrangian is extended
to a GRQM wave theory, one might speculate that these observables are
replaced by wave function, and observables operators operating onto them.

In such a setup there might be new components that relative the original
Einstein-Hilbert GR equation behave as dynamically varying cosmological
constant-like additions. In order to produce such new component additions
empirically, one probably needs better observational inputs from the real
universe. The other method would be, Einstein-like, to find a very
appealing mathematical formula that later turns out to be a very good
description of the observed universe, but that seems to be hard.

But the interesting conclusion is that on this very large scale, perhaps
the Einstein-Hilbert GR equation is incomplete and needs some
modifications. I was somewhat sceptical to that idea before these
discussions: I thought the remaining part would only be to describe how GR
and QM behave together in a black hole.

(As for the comments you had that mainly Newtonian physics regulate the
behavior of galaxies, I noticed the similarity of pictures of hurricanes
from the above with those of spiral galaxies. Hurricanes get their
rotational energy from the Earth's rotation and their energy from the heat
of the sun. I am not sure whther it means something, but a comparison with
galaxies might be interesting.)

  Hans Aberg