Black holes are regions of space where gravity is so strong that nothing, not even light, can escape! No longer confined to the imaginations of science-fiction writers and theoretical physicists, black holes have recently been discovered in large numbers by observational astronomers. Learn about the remarkable properties of these bizarre objects from Dr. Alex Filippenko (University of California, Berkeley), one of the finest explainers in the field of astronomy. Recorded May 19, 2010.