Re: Another sort of expansion?
From: Stuart (bigdakine_at_aol.com)
Date: 02/18/05
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Date: 18 Feb 2005 12:33:44 -0800
Jo Schaper wrote:
> Since we are all reading our March Scientific American magazine, may
I
> direct the group to the article on the Big Bang?
>
> The authors are talking about the expansion of space, not matter,
from a
> densely filled space to a sparsely filled one. Their analogy is to
tape
> paper pictures of galaxies on balloons. The balloons expand, but the
> galaxies do not.
Sounds like Standard BB Cosmology; I haven't seen the article however.
Keep in mind that on the scale of galaxies, the hubble expansion is
tiny. It doesn't become appreciable until you're looking on the scale
of megaparsecs (Mpcs).
Now that paper should also have talked about a parameter called Omega.
IF Omega is > 1, the universe expands forever, less than one the
universe will eventually contract.
For objects like galaxies Omega < 1, they won't expand with the Hubble
flow.
I beleive this is true for galactic clusters, and structres as large as
the Virgo attractor.
>
> I am not the smartest turnip on the truck, but can someone explain to
me
> where the fundamental difference is between so called 'empty space'
and
> so called dense space or matter?
Empty space lacks the gravipotential energy of matter endowed space.
I'm having trouble cogitating on the
> concept that space and distance may be expanding, but that matter
stays
> the same size (trapped, as I think I understand, by gravitation).
Yes. Weird. Ain't it?
>
> This is at the same time of having survived an education where matter
> was treated as little more than congealed energy--that is, at the
sub-
> atomic level, 'space' between protons, neutrons, electrons, and the
> other 23 flavors of little charges and forces can be proportionally
very
> huge, and matter, in one sense, is considered just patterned energy
> vibrating very fast to create the illusion of solidity.
>
> Unlike some savants around here, I freely admit this concept of
> 'differential speeds of expansion' and the 'non-expansion of matter'
> coexisiting with an expanding universe causes me trouble.
Clumps of matter act as speed bumps for the Hubble expansion.
>
> Or, do the cosmological physicists mean something else by the word
> 'expansion' than 'increase in linear or volumetric distance'?
No it pretty means what your think it is. Each Pc of space increases,
on average, in lenght by ~70km/yr. So in nearly matterless less space,
lets suppose the distance between two chunks of matter is 100Mpcs. THen
the distance between these chunks increases every years by 70x100x10^6
or
7 billion km.
The farther apart two objects are, the greater the distance increase
per year. This results in the famed redshift.
Stuart
> Jo
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