Stars That Go Bump in the Night Sigma Xi Distinguished Lecture Robert Mathieu University of Wisconsin-Madison The distances between the stars are vast, and until recently collisions between stars seemed highly unlikely. Now we think they happen quite frequently, particularly when binary stars encounter each other within clusters of stars, and create stars that as yet are unexplained by standard stellar physics. These events bring together two classical fields of astronomy, stellar dynamics and stellar evolution. I will introduce the audience to the basics of both, and then embark on a journey into the strange world of stellar collisions.