In this week's live QA, I explain why a black hole can have infinite density but not infinite gravity. Does your perception of time change due to your mass, and am I ever intimidated by the people I get to interview? 03:00 How can a singularity have infinite density and not infinite gravity? 06:02 Does your perception of time change due to your mass? 20:25 Would you feel it falling into a supermassive black hole22:00 Will we get a Grand Unified Theory in our lifetimes?