Conformal Symmetry in the Sky (Oskar Klein Memorial Lecture)

Recent observations suggest the sky contains black holes whose horizons are spinning at nearly the speed of light. General relativity implies that the dynamics very near the horizon of such extreme black holes is governed by an enhanced infinite-dimensional conformal symmetry – identical to the enhanced symmetry observed near the critical points of a variety of condensed matter systems. Potential observational consequences of this symmetry are explored.