(January 31, 2011) Leonard Susskind gives a lecture on string theory and particle physics that focuses on the geometry of a black hole near the horizon. He describes how standard concepts from quantum physics can explain the physics that occur at this point. In the last of course of this series, Leonard Susskind continues his exploration of string theory that attempts to reconcile quantum mechanics and general relativity. In particular, the course focuses on string theory with regard to important issues in contemporary physics.