  Although implicit in the discovery of the Schwarzschild solution 40 years
earlier, the issues raised by the theory of what are now known as black holes
were so unsettling to physicists of Einstein's generation that the subject
remained in a state of semiclandestine gestation until his demise. That turning
point -- just half a century after Einstein's original foundation of relativity
theory, and just half a century ago today -- can be considered to mark the
birth of black hole theory as a subject of systematic development by physicists
of a new and less inhibited generation, whose enthusastic investigations have
revealed structures of unforeseen mathematical beauty, even though questions
about the physical significance of the concomitant singularities remain
controversial.
