Burn a secret diary and physics says a powerful enough computer could reconstruct every word from the ash and smoke. Drop that diary into a black hole and the answer becomes the black hole information paradox, a head-on collision between quantum mechanics and general relativity. This episode explains unitarity, why quantum evolution must be reversible, and how Stephen Hawking's 1970s calculation of thermal radiation from evaporating black holes seemed to destroy information forever.

We cover the no-hair theorem, the 1997 encyclopedia bet between Hawking, Kip Thorne, and John Preskill, Don Page's entanglement entropy argument and the Page curve, Samir Mathur's fuzzballs, the 2012 firewall paradox born from the monogamy of entanglement, Hawking, Perry, and Strominger's soft hair proposal, and the holographic principle and AdS/CFT corresponden ...