Singularities are predictions of Albert Einstein’s general theory of relativity. According to this theory, clumps of matter or energy curve the space-time fabric toward themselves, and this curvature induces the force of gravity. Most physicists don’t believe, however, that Einstein’s theory says much about what really happens at these points. The singularities are expected to vanish in a more fundamental theory of gravity that Einstein’s space-time picture merely approximates—a theory of quantum gravity. But as physicists take steps toward that truer and more complete theory by merging general relativity and quantum physics, singularities are proving hard to erase.