(March 7, 2011) Leonard Susskind gives a lecture on string theory and particle physics that dives into the idea of cosmic horizons as well as the relationship between ultraviolet and infrared light. 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. This course was originally presented in Stanford's Continuing Studies program. Leonard Susskind is the Felix Bloch Professor of Physics at Stanford University. Stanford University: www.stanford.edu/ Stanford Continuing Studies Program: csp.stanford.edu/ Stanford University Channel on YouTube: www.youtube.com/stanford