There are black holes in space, regions where nothing can escape, not even light. There was the Black Hole of Calcutta where Bengalis confined British troops overnight in such tight quarters that almost all of them died and none could escape. And then there is the black hole we carry around with us everyday, the black hole of what we don't know. Some things we may never know, some we may not know but may discover, and some we may know but prefer not to know so we ignore it. This is our personal black hole. How much do we actually know?