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The space far
from a black hole is kind of boring. It has no distinguishing features
besides the degree to which it is bent, and this bending, is no different
than that of an ordinary star of the same mass. In fact there is a "no
hair" theorem that guarantees black holes to be virtually featureless
when viewed from far away. All the bumps and wriggles of the matter from
which they were formed are smoothed out as the matter contracts, so that the
final shape of the horizon is always perfectly smooth and round. Near the
event horizon, things are more interesting. To a distant observer, events
near the horizon appear to slow down. If you drop a clock into a black hole
it appears to tick more and more slowly as it approaches the event horizon.
Time actually appears to stop right at the horizon. The clock's motion
towards the black hole also slows down and to a distant observer it takes
literally forever to fall through. If you are unfortunate enough to be
falling with the clock, time appears to progress normally. You fall through
the horizon in a relatively short time, and once you are past it, you get
sucked to the singularity at the center in a millionth of a second (for a
solar mass black hole). Time and space interchange roles, and you can no more
avoid falling to the center than you can avoid moving from the present into
the future. The only 100% reliable way to detect the presence of a black hole
is to fall through the horizon and verify that it is literally impossible to
stop moving towards the center. Of course your discovery won't do your career
much good: there would be no way to publish your results.
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