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Re: Cosmology

In a message dated 2/10/01 12:29:47 PM Eastern Standard Time,
JMGreen@SISNA.COM writes:

<< 1) Our galaxy is expanding -- whirling out into the Universe. And the
Universe is expanding and making our galaxy bigger in the process.

Is this correct?

No When considering the expansion of the Universe you must make a distinction
between gravitationally bound structure and unbound structure. The Structure
of our
Universe appears to as follows. There are seven levels of cosmic structure
(Varies depending on how you classify the levels)
1) Planetary systems like our own solar system. ( It appears indisputable
now that there are other planetary systems.)
2) Galaxies such as our Milky way.
3) Groups of Galaxies such as our local group.
4) Clusters measuring 10 to 20 million light years across which consist of
hundreds to thousands of galaxies.
5) Structures called clouds (Not accepted as an actual level of structure
by some) which measure 30 million light years across often linked together in
strings called filaments and spurs.
6) Super Clusters measuring 100 million light years across and contain
upwards of ten thousand Galaxies.
7) Super Cluster complexes which measure a billion light years in length.
These complexes form walls of huge voids measuring about 300 million light
years across.
All structures smaller than a cloud are gravitational bound and are not
expanding. Structures larger than clusters are undergoing expansion.

2) During the first few minutes of the existence of the Universe, it's
rate of change in size was enormous.>>

Yes, it accepted by most cosmologist that very early in the life of the
Universe it underwent a rapid and exponential expansion. This is required to
explain the relatively homogenous nature of our current universe.

What is the current rate of change in size? In reasonable units? In

The current rate of expansion based on best current data seems to be
increasing. It is accepted by some cosmologist that there is a "Cosmological
Factor " which acts a kind of anti gravity at very large distances causing
our Universe's expansion rate to be accelerating.

Bob Zannelli