[geeks] Mr Bill?

[wa2egp at att.net]

-------------- Original message ----------------------
From: Shannon Hendrix <shannon at widomaker.com>
>
> On Sep 18, 2008, at 23:55 , der Mouse wrote:
> 
> > Not very.  The mean density of matter in the galaxy is thin enough  
> > that
> > here on Earth we'd call it a pretty hard vacuum.
> 
> It's a big galaxy.  It doesn't matter how dense the galaxy is, there  
> are still a lot of them.
> 
> Our own solar system has a lot and our various moons show vivid proof  
> of just how many big ones have hit.
> 
> >> Plus, we have records of various bodies being totally obliterated,
> >
> > We do?  I'd like to hear more - this is the first I've heard of any
> > such.
> 
> Several probes have taken pictures of very thoroughly shattered moons,  
> some quite large.
> 
> At least a few appear to have been broken apart and fell back  
> together, or were split by the impacts.
> 
> I'd say that would hurt us pretty bad.
> 
> It can certainly happen.
> 
> I'm not saying it is likely, just that it can.
> 
> Besides, even a small asteroid can send us on a serious and  
> demoralizing detour without doing that much damage to the planet itself.

One theory about the moon's formation is that the earth was hit by a Mars sized object and the "splash" came together to form the moon.  From some gravitational measurements, it looks like it made from about four large denser chunks with less dense chunks (and smaller dense chunks) filling it in.  I've always wondered if it wasn't for the moon, life might not have occurred on earth.  It took a lot of hits for us.

Bob