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Old December 14th 18, 10:55 AM posted to sci.astro
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Default gravity, Hubble, negative mass and Dr. Farnes

Thomas 'PointedEars' Lahn
wrote:
Thomas 'PointedEars' Lahn


I would not call *that* a “phase transition”.


Your opinion! Citations showing otherwise please.

[Likewise, “isotropic” (Ancient Greek: “isos” + “tropikos”: “equal when
turning”) means “the same in every direction”.. What you described is
meant by the word “homogeneous” (Ancient Greek: “homogenes”: “of the
same family/kind”) instead.]


I am aware of what isotropic and homogeneous mean. The standard cosmological
model uses that assumption.


But on large scales our universe *is* assumed to be homogeneous (*and*
isotropic).


Otherwise the FLRW metric would not be valid within that standard model.

This assumption is based on the fact that, in all directions, we observe
less galaxies the farther we look,


That is just wrong.

precisely as if our universe would be
homogeneous and the inverse square law for the intensity of electromagnetic
radiation, extinction, and the distance–redshift relationship would apply
(which so far have only been confirmed).


I have no argument with that. You’ve only introduced that to rebut an idea I didn’t
state.

The FLRW metric assumes a uniform density in an expanding Universe.
The model is a dust model. It predates the discovery of large
scale structure. (Voids and Filaments) Noting that the Universe is isotropic and
homogeneous only on large scales is a “fix” that reinforces the original dust model
idea. I have no problem with that as long as one realizes that it effectively hides the
local significance of Voids and Filaments.


So my idea was to begin my monologue prior to the development of these density differences.

It was also my intention that the growth of Matter structures and the growth of
the Voids are concurrent.


While voids *are* growing, "matter structures" *in general* do NOT, because
galaxies on "short" distances and objects in galaxies are gravitationally bound.


Mattter structures grow by gravitational collapse of existing matter. Voids grow
by either the introduction of new spacetime or the expansion of existing spacetime.
You’ve introduced an objection to a conjecture I did not make.

(Standard models accept only gravitational collapse.)


Simply untrue. The current standard model of cosmology (ΛCDM) *predicts* a
universe whose expansion is accelerating, because that is precisely what has
been observed in 1998 (the Nobel Prize in Physics 2011 was awarded for the
discovery) [1].


I know that. Again, you’ve misinterpreted what I wrote. Matter Structure growth is assumed
to be the result of gravitational collapse.

But that expansion is not affecting the formation of moons, planets, stars,
galaxies, and galaxy clusters, for the reason given above.


Again, I know. I never wrote that. You’ve introduced an objection to a statement I never made.


That each is dependent upon the other for perpetuating
the overall structure we see today.


This statement is almost vacuous. But if interpreted in your favor,
precisely this connection *is* made by ΛCDM.


It is the lambda cold dark matter model that I’m reinterpreting. I’m saying that
we should not look for exotic matter. We should instead be taking what we know
to be real and re-thinking our notions of how they can interact.



That is the low density Voids and the high density filaments.



It is known that expanding space time metrics will push Matter.


No, that is only your misconception.


Then you reject the conclusions of W. Israel? Of Humitaka Sato? And
others? You should explore the literature.

[ex falso quodlibet


Ultimately what I’m arguing (and you’re misinterpreting) is that a model
based on gravitational potentials with more/less values spread across
the Universe cannot be valid. Or at least not complete!
The fact that Voids expand should be reason
enough to at least modify that idea. GR says (and I accept, so you know and
don’t attempt another reinterpretation) that curved space in the presence
of matter is the reason for gravitational attraction. Voids are also curved
space...in the opposite sense! Do we really need to look for Dark Matter?

The Einstein-deSitter spacetime was valid for the early Universe (within the FLRW
metric) it’s still valid when applied only to the Voids. Our Universe can be modeled
as having two distinct spacetime regimes that produce the large scale structure
we see today.

Brad