Stoney’s British Pub
3007 Concord Pike
University of Pennsylvania
“Friction: The Surprising Unsolved Science Behind Earthquakes & Tire Treads”
Friction occupies a strange place in science and engineering. If we learn about friction in school, we are taught a simple equation that is hundreds of years old, which tells us friction between two objects only depends on the material(s) and how hard those two objects are pressed together. This is, ﬂatly, far from the truth, and can often be wrong by a factor of two or more. In engineering, that simple equation is still used, but designers are careful to avoid relying on it too much. In geophysics, where the study of two tectonic plates sliding past one another (earthquakes) is of great importance, more complex descriptions of friction have been developed, but they are also imperfect, and do not give an underlying explanation of why there is friction. In this talk I will discuss the history of research on the topic (from da Vinci to today), including strange and new behaviors of friction discovered in the last decade, such as frictional memory, and the plethora of questions that are still unanswered.