Antimatter and Matter in the Universe

Richard Dawkins: Why do we call some things matter and some things antimatter? How do we know if you find a new particle whether you should call it a matter particle or an antimatter particle? He says for every kind of particle that we know about there's another one that can't exist in the universe. And so this is something that the universe can do, like a feature of the universe, but it's not something that exists very often.