Warp <war### [at] tagpovrayorg> wrote:
> > I guess it will rather be that as the black hole evaporates, the EH will shrink
> > as you said, but the "victim" will still seem to "stick" to it.
>
>   Why? Exactly how does that happen?

Suppose for argument's sake that the BH just suddenly happens to shrinks to half
its mass.

What happens to the EH? Simple: It recedes. A BH with less mass has a smaller
Schwartzschild radius.

What happens to the gravity well? Simple, too: Its slope gets less dramatic
where the EH used to be. Still catastrophic where the EH is *now*.

What happens to the point where the victim was "hanging out"?

Now this gets a bit more tricky. I'll present two approaches that sound
plausible to me; both would come to the conclusion I presented, and I guess
actually both would happen at the same time:

(a)

What does a "gravity well" mean? Well, it's distorted spacetime. I imagine it as
"compressed". So let's for the sake of argument use a very simplistic image;
say, a BH would just influence a radius double its EH radius, and the space
between that distorted linearly.

So let's assume that the "victim" has fallen 99% along this slope (he has had
enough time to do that), so he's just 1% of the EH radius away from the EH,
when all of a sudden the black hole goes on a diet: Pop! here goes the EH
radius to, say, half its diameter.

Space further away gets "un-distorted" - actually all the space up to the old EH
radius. But that's only the part up to 50% along the old slope. The remaining
50% are still "downhill", with our victim still on this slope. 98% along it,
actually. So 2% of the new EH radius away from the new EH.

So for practical purposes, he has almost exactly moved along with the receding
EH.

Note that in reality, the distortion close to the EH would be much stronger than
further away, and the "un-distortion" effect would be much weaker for areas very
close to the EH than for areas further away.

(b)

What would happen if the EH would suddenly recede and spacetime getting somewhat
"un-distorted", and our victim would *not* follow the EH?

Well, in that case, from an outside observer his wristwatch would speed up
again. But then what? Remember what the poor old sod was busy with when we left
him hanging at the edge of the EH? Right: Falling straigt towards the black
hole! So what will he do now in his newly recovered spare time? Um... continue
falling I guess...

So if the receding EH would also recede from our poor sod, he'd *very* quickly
catch up with it...


I guess both effects will happen, and they will combine. So there's reason
enough to believe that even as the EH recedes, that guy will still keep hugging
it, bound in eternal love... ("Oh darling, why can't this moment last forever!")

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