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Marko Rauhamaa wrote: > pdorange at pas-de-pub-merci.mac.com (Pierre-Alain Dorange): > >>Near a black hole 3.7 seconds can last an infinite time... > > Which phenomenon prevents a black hole from ever forming. Yet > astronomers keep telling us they are all over the place. Astronomers have observed objects whose behaviour is entirely consistent with the existence of black holes as predicted by general relativity. > Oppenheimer and his co-authors interpreted the singularity at the > boundary of the Schwarzschild radius as indicating that this was the > boundary of a bubble in which time stopped. This is a valid point of > view for external observers, but not for infalling observers. > > Note that the "valid point of view for external observers" is the only > valid scientific point of view. The singularity being talked about there is an artifact of a particular coordinate system; the theory predicts that there is no *physical* singularity at the event horizon. It's true that we outside can't be absolutely sure that things are as predicted at the horizon itself, because any observer we sent in to check would be unable to report back. But in principle we can observe arbitrarily close to it. The observations we've made so far all fit the theory, and the theory doesn't present any obstacles to extrapolating those results to the horizon and beyond, so we accept the theory as valid. There *is* a difficulty at the very center of the hole, where there is a true singularity in the theory, so something else must happen there. But for other reasons we don't expect those effects to become important until you get very close to the singularity -- something on the order of the Planck length. -- Greg

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