Darren New <dne### [at] sanrrcom> wrote:

> And at what distance do you start slowing down?
>
> If you take the Earth and condense it down to a black hole, then stop a
> particle in orbit 100 miles above where the surface used to be, the particle
> will accelerate towards the black hole, right? But to avoid crossing the
> event horizon, it must logically decelerate, as seen from the POV of someone
> in orbit (say).  You wouldn't stop at the original altitude of the surface,
> but you would stop before you get to the event horizon, so in this case,
> gravity must be causing you to decelerate.  Yes?

Here's a couple plots to show the scales involved in your question.  For the
earth, the Schwarzschild radius is about 9mm.  If you start from 1m, I've
attached plots showing what an external observer sees and what the dead guy
sees.  (The units of time are meters, so you need to divide that by c to get
time.)  I'm not sure it's correct to think of it as deceleration since that's
really a notion we have from flat space-time.  For this case, space-time is
infinitely warped, so even though it may appear that you decelerate to an
outside observer, in fact you accelerate all the way to the center.  You can
also see here that the event horizon means nothing to the guy passing through
it.

 - Ricky

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