John F. Hawley is Professor of Astronomy at the University of Virginia. His research interests include black holes, accretion disks, and large-scale numerical modeling of astrophysical systems. He was the 1993 recipient of the Helen B. Warner Prize from the American Astronomical Society for his contributions to accretion disk theory and numerical simulations. He has taught an introductory course in cosmology for undergraduates at the University of Virginia since 1989. Katherine A. Holcomb received a Ph.D. in physics from the University of Texas at Austin. She has worked on numerical sim...