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Posted by Hugo on August 27, 1999 23:53:43 UTC
: : : : : : : : Why does time come to a stop at the event horizon of : : : : : : : : a black hole?
: : : : : : : It does not. Time becomes the radial coordinate inside the black hole event horizon.
: : : : : : Then why would photons become more and more redshifted near the event horizon?
: : : : : It's only the photons that we observe that are red shifted and that's because space near the horizon is traveling so fast away from us. It's the same mechanism as the expansion of the universe which makes light from more distant sources more red shifted. The sources are actually traveling away from us because space at those distances is traveling away from us. If we could see far enough space would be seen to be traveling away from us at near the speed of light, just as it is near the event horizon of a black hole.
: : : : If space near the event horizon is traveling away : : : : from us at near c then the time dilation would be : : : : near infinity and therefore time would have come to : : : : a stop with respect to us as faraway observers. : : : : Wouldn't it?
: : : Time stops in the sense that we cannot observe its passage. It's time at a distance that stops. Time in the local frame does not stop.
: : Yes, but you must keep in mind that we are the faraway observers, and therefore time, for us, does come to a stop at the EH of a Black Hole. Therefore there is no way for a singularity to form, or for any matter or energy to enter the hole with respect to the time that the faraway observer (everything but the hole itself) experience, so in effect a Black Hole is a frozen star.
: A singularity can form as long as we do not observe it. You seem to be saying that a singularity can't form if we don't observe it. That likens us to God, just as the Anthropic Principle does, which says that the the world could not exist if we were not here to observe it.
Actually that's not what I was saying.
The time dilation effect near a gravitating mass is very real. If space were marked out by a set of fixed clocks, those located where gravity is strong would - to a distant observer - run slow; conversely, distant clocks would run fast when viewed by observers near the gravitating mass.
At the EH time the time dilation would be infinite and to distant observers the clocks located there would stop. This is not just an observation effect - time really does stop, - and nothing can enter the hole.
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