Hans Christian von Baeyer
Chancellor Professor of Physics
College of William and Mary
Hans Christian von Baeyer began his talk with the rather engaging and provocative comment that "There is no such thing as time . . . Past is memory . . . future is fantasy." As for the present, that is a point in the mathematical sense. An abstraction of something that cannot be measured. Time does not exist, because past, future, and particularly present, do not exist.
From this beginning, however, von Baeyer delved into the way that physics perceives time, and in particular looks at the way that thermodynamics, special relativity, general relativity, quantum mechanics and quantum gravity all indicate that time is an arrow that cannot be turned back. Time may move faster and slower in certain spaces as a result of gravity or motion but, despite some fantastic claims to the contrary, it cannot be reversed.
The question and answer session that followed von Baeyer's talk raised many interesting questions regarding theoretical physics and the reversal of time's arrow. Wormholes, time machines, and other potentially revolutionary concepts were brought up by audience members seeking a way around the irreversibilty posited by von Baeyer. As von Baeyer countered, however, relativity did allow for a certain kind of time machine - one in which a rapidly moving subject experienced the passage of time at a slower rate than other subjects at relative rest. Thus, the rapidly moving subject would seem to speed forward into the future. The possibility of travel into the past, however, remains in the realm of science fiction authors.