[ladams]

A minor correction: anti-matter is actually regular matter. We understand it quite well, and are even able to create anti-atoms in the lab. On the other hand, dark matter is much more poorly understood: essentially the only evidence we have for its existence are observations of "weird" gravitational effects in the universe.

[hwayne]

Also we have pretty strong evidence that, at least in the observable part of the universe, almost all visible matter is regular matter.