The Physics and Astronomy Colloquium, held jointly with the Carnegie Mellon University Physics Department, provides an opportunity for all faculty and students to hear invited lectures and discuss problems of current interest to members of the Physics and Astronomy Department. The talks are intended for faculty and students from all areas, and thereby constitute a unifying element for the department. Also, talks of even broader interest are occasionally presented. The weekly one-hour Monday colloquium lectures are generally evenly split between the University of Pittsburgh and Carnegie Mellon University throughout the course of the academic year. Registered students must make a short, 1-paragraph summary of at least 10 colloquium lectures to receive credit.