🚀 go-pugleaf

In article <1992Sep23.143830.25927@cid.aes.doe.CA> ynecgan@cid.aes.doe.CA (Greg Neill) writes:
>I have repeatedly come across
>statements similar to: "...the general expansion of the universe does
>not affect galaxy structure or clusters, since they are held together
>too firmly by gravitational forces."  Now, what the heck does this mean?
>Is space not expanding uniformly at all scales?  

Nope.

The calculations that demonstrate that the universe should expand a
uniform rate ASSUME that you have a universe whose density is uniform.
Now at large scales, this is a pretty good assmuption.  If you look
at the universe as a whole, it looks and acts a lot like a uniform
fluid, just like a air looks and acts a lot like a uniform fluid if
you don't look closely enough to see atoms.

At small scales, however, the universe is not uniform, and so you have
to throw any calculations assume that it is out the window.