>Date: Wed, 25 Apr 2001 14:04:18 -0600

"Grant" wrote:

>This is a question from my 10 year old homeschooler.  "Could dark 
>matter be the missing anti matter?

That is a good idea, Grant and "homeschooler", and many physicists
have mused about anti-matter in the universe.  But, it is
unlikely that the dark matter is anti-matter.  Anti-matter does
indeed exist -- it can be created on earth in the lab and
also can exist in outer space.  But, when anti-matter collides
with matter, an annihilation occurs and radiation is emitted.

Now, if we are right about dark matter, there is a *huge*
amount of it in the unverse -- much more than ordinary matter.
It exists in spheroid "halos" in the centers of galaxies and
stretches out beyond the outskirts of the galaxies.  If this
were anti-matter, it would annihilate with all of the ordinary
matter and would have done so long ago.

But, what dark matter is, we don't know...

Michael Scott Armel
Center for Particle Astrophysics