Now, this idea seems a bit weird (to me and I think to you as well) because if nothing ever passes the event horizon, how can there ever be a black hole in the first place? My friendly cosmologist's answer boiled down to this: the black hole itself is only ever an approximation. To my mind the resolution to the black hole information paradox lies along this line of reasoning and not in any specifics of string theory. Presumably, from the clock's perspective all those billions of years of radiation will appear in the split-second before 12:00, so it won't come out looking much like a clock any more. Since our clock will still not have passed the event horizon by the time this happens, it must eventually escape - although presumably the Hawking radiation interacts with it on the way out. (At this point I want to note in passing that any "real" black hole will emit Hawking radiation until it eventually evaporates away to nothing. (I believe the "no hair theorem" provides the justification for this.) He also said that the black-hole-with-an-essentially-undetectable-object-just-outside-its-event-horizon is a very good approximation to a black hole of a slightly larger mass. I had the opportunity to chat to a cosmologist about this subject a few months ago, and what he said was that this red-shifting towards undetectability happens very quickly. Nevertheless, as you say, it is always possible in principle to detect the clock, because it never passes the event horizon. Eventually it will get to the point where we'd have to wait billions of years in between photons. Because of this red shift, and because we can only ever see photons emitted by the clock before it struck twelve, it will rapidly become very hard to detect. The light from the clock will also slow down, becoming red-shifted quite rapidly towards the radio end of the spectrum. In fact its hands will asymptotically approach a certain time, which we might as well call 12:00. What we notice as the clock approaches the event horizon is that it slows down compared to our clock. We will stand a long way from the black hole and watch the clock fall in. By "classical" I mean a black-hole solution to Einstein's equations, which we imagine not to emit Hawking radiation (for now). I will attempt to describe the situation as best I can, to the best of my knowledge.įirst, let's imagine a classical black hole. It is true that, from an outside perspective, nothing can ever pass the event horizon. If observers see objects slowly fade and slowly disappear as they approach the event horizon would that mean that over time the event horizon would be "lumpy" with objects invisible, but not passed through? We should be able to detect the "lumpiness" should we not through? ![]() Again, please keep thinking from an observers point of view. OK - just an edit based on responses so far. Why would it slowly fade and if it would how long would this fading take? If it is going to red shift at some point would the red shifting not slow down to a standstill? This question has been bugging me for years! I am getting ready for the response of the object would slowly fade. If I was able to train the telescope onto the black hole for millions of years would I still see the rock at the edge of the event horizon? ![]() I have it focused on the black hole and watch as a large rock approaches the event horizon.Īm I correct in saying that from my far-away-position the rock would freeze outside the event horizon and would never pass it? If this is the case how can a black hole ever consume any material, let alone grow to millions of solar masses. In my thought experiment I am in a spaceship with a powerful telescope that can detect light at a wide range of wavelengths. If this is the case how can anything ever fall into a black hole. ![]() This is also the point I understand that according to Einstein time dilation will be infinite for a far-away-observer. The event horizon of a black hole is where gravity is such that not even light can escape.
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