As blumfeld0 has already said, a topic (first posted by SF) that has come up on another thread deserves a thread of its own. A controversial, just-published paper which asserts that black holes never form is generating substantial interest within the astrophysics community. The standard view is that after a supernova explosion, the core of a sufficiently massive star collapses and forms a black hole. Because of inifinite gravitational time dilation, an observer who hovers above the collapsing core never see a black hole form, but an observer that who sits on the "surface" of the collapsing core rapidly finds herself inside a black hole. Also, an astronaut who takes a trip towards such a collapsing core can cross the event horizon of a black hole in a finite amount of proper time. This new paper says that, due to Hawking radiation, NO observer finds himself inside the event horizon of a black hole. I expect the dust will settle on this issue within a couple of years, but things might be settled: in a substantially shorter period of time; in a substantially longer period of time, if a fully quantum theory of gravity is needed to decide what happens. blumfeld0 has given links.