Antimatter has long fascinated and confounded cosmologists. Everything we know about this mysterious stuff places it on an equal footing with matter. Antiparticles possess the same mass, are created and destroyed in the same ways, undergo the same interactions, and otherwise represent seemingly perfect—and yet opposite—copies of their particle counterparts. It is the fact that these substances are so precisely alike that makes it so hard for us to understand why there is so much more of one than the other in our universe today.
