I recall reading about creating a black hole from having an area of space-time occupied by a sufficiently high enough number of high-energy photons, so as to create a black hole. I believe this has some German name, but I can't recall it at the moment. Does anybody have an opinion on this? Could, for example, 2 or more sufficiently high-energy gamma bursts "collide," creating a zone of space-time with sufficient 'effective mass,' so as to create a black hole? If so, what would happen (ie, how much of the energy would be converted into momentum, resulting in a high-speed black hole flying through the universe). If none of it is converted into momentum, doesn't this imply a preferred rest frame? Also, is there any difference between a Blackhole (made of regular matter) and a Whitehole (made of anti-matter)? It seems to me that a Blackhole violates CP symmetry, and thus a whitehole is no different from a blackhole (since all of the matter is compressed to nothingness and loses all of its properties besides charge, angular momentum and mass). If they are the same, then can you ever preserve CPT symmetry with a black hole? Attempting time reversals of various particles and forces being absorbed by the black hole (with their various carrier-virtual-particles) seems to imply CPT symmetry violation. . . Is that correct?