Black Holes from Colliders and Cosmic Rays

A startling prediction of many phenomenological scenarios with large extra dimensions is that TeV-scale collisions may produce microscopic black holes in cosmic rays and at colliders. The fact that no such cosmic ray events have yet been observed places the best current lower bounds on the scale of higher-dimensional gravity, with 5 or more extra dimensions. I review the current status of these bounds, and the prospects for improving them over the next few years at the Pierre Auger Observatory and the LHC.