Mung asks about antimatter:

You are correct. Based on our understanding of symmetry there is every reason to believe there should have been as much matter as antimatter.

But based on B Factory work we also know that there are some asymmetries between matter and antimatter. They are not "just" mirror opposites.

Clearly we do not know why we don't see an equal amount of antimatter but keep in mind that baryonic matter is the smallest, percentage wise, constituent of the universe. Basically it, we, are about as meaningful as a carbon inclusion is to a diamond. It may well be that at one point in time there were essentially equal amounts. That they annihilated each other. And what is left is just the very small asymmetry from the original. We just do not know ... YET!

DA Morgan