On Oct 18, 2012, at 8:07 PM, David Roberson <[email protected]> wrote:

> In light of the fact that a galaxy is geometrically immense, I have long 
> wondered why most of those seen through telescopes are so well formed.

This is quite easy to find out. Just running simulations and see what Newton 
wants from the Galaxy evolution. Galaxy evolution is quite easy to simulate, 
because Newton's law of gravity is so simple.

Short answer is that spiral galaxies are formed in collisions of smaller 
elliptical protogalaxies. The collisions will drive the starformation, when 
clouds are disturbed and stardust is compressing into large stars. And as 
galactic interactions are violent, they will happen fast, in few billion years. 
Milky way is approximately 10 billion years old, so the formation of the large 
spiral galaxy happened in just few billion years. 

However, spiral galaxies are not stable structures and eventually Milky way 
will deform into shapeless elliptical galaxy that is reddening when star 
formation rate diminishes and old red and yellow stars are becoming dominant. 
However as two spiral giants Andromeda and Milky way are colliding in not too 
distant future, there will be lots of star and planet formation and hence 
things will get bright again. However with this scale of collision and merging 
end result will be mostly large and shapeles elliptical galaxy with twin core.

Personally I would speculate that we need to alter big bang theory quite a lot 
although the age of univese is properly calculated. It is verified with so many 
distinct ways and all dating methods are pointing into same point of origin. My 
idea would be that expanding cosmos is gravitationally balanced, i.e. it is 
finite although it has no borders, similarly to that of Earth's surface. As 
cosmos is gravitationally balanced, we do not need to worry how cosmos can 
expand, because the expansion of cosmos is indifferent from gravity or energy 
density. Therefore cosmos also appears as flat in cosmic microwave background. 
I hope that Planck satellite data will verify that cosmos is indeed flat and 
hence it will disprove inflation hypothesis and naïve dynamic models of cosmos. 
This model of gravitationally balanced cosmos will solve almost all current 
major problems in Big Bang model. 

—Jouni

Ps. Jed, thanks for correcting me. I had and still have horrible head ache due 
to cold. Therefore my English was worse than usually.

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