Henrik Latter University of Cambridge Fine-scale structure in Saturn's rings Wednesday 28th March 14:05-14:55pm, Eastern Avenue Lecture Theatre. The rings of Saturn are composed of trillions of icy boulders ranging in size from a few centimetres to a few metres. These particles undergo, on average, several very gentle collisions per orbit. In fact, their average impact velocity is barely 2 mm/s! But these seemingly innocuous interactions, when allied with gravity, can have considerable collective effects. Over relatively short time-scales they sculpt the disk into irregular radial patterns. This talk presents an introduction to the physics of planetary rings and concentrates on the theory of fine-scale structure formation. In particular, emphasis is placed on the difficult modelling issues thrown up by a 'gas' of infrequently colliding inelastic particles. We find that a planetary ring is in a unique regime which hydrodynamical models cannot adequately capture.