Re: Effect of a lumpy universe

This is an interesting question.  However, gravity is not strong enough to 
pull galaxies or group of galaxies into a 'little crunch'.  The only place 
where gravity is strong enough to overcome local motions is when an object 
is within the event horizon of a Black Hole. You can think of that as 
being a 'little crunch'.  Everything inside the Black Hole looses 
communication with the outside universe.  Supermassive Black Holes do 
exist in the center of galaxies having masses of billion times the mass of 
the sun.  But the diameter of the event horizon is still only a few 
billion km--very small compared to the size of a galaxy.

I am not a cosmologist and if you need more information, the above website 
includes a  'Ask an Astronomer' link. [note added by MadSci Admin: there is 
actually an astronomy section to MadSci, so questions can be addressed to them.]