Re: How can Dark Matter be composed of WIMPS?

Stan - you make a very good point. After all, we infer the presence of
dark matter from its gravitational effects, and we certainly don't see
a lot of unaccounted-for gravitational effects in our solar system.

But something you may not realize is that most of our galaxy (and indeed
most of the universe), is empty space, with no stars or solar systems.
So there is lots of room for the dark matter to hide. Here is
an example:

Most of the stuff we can see in the solar system is no further
away than about 50 AU from the Sun.
(1 AU=150 million km=the distance from the earth to the Sun).
The nearest star is about 200000 AU away. So the volume of space
in the solar system, compared to the 'empty' volume between us
and the next star, is very small. The empty space is 
(200000/50)^3 = 6.4x10^10 times bigger! (Wow!)

There are two places where there is observational evidence for
dark matter: in the far outer reaches (the 'halo') of spiral
galaxies like ours, and in the space between galaxies located in galaxy
clusters. Since our solar system isn't located in either of these
environments, the fact that we don't see dark matter in our neighborhood
doesn't mean it isn't elsewhere.

Pauline