Re: A partial black hole?

Erik Max Francis wrote:
> James Burns wrote:
> 
>> Consider a particle inside the event horizon, just as
>> you describe. /If nothing in the situation changes,/
>> no message will ever be able to be sent from this particle to
>> the outside world.
> 
> I think this is where the confusion lies.  Objects inside event
> horizons do not stick around; in fact, they hit the singularity
> in ~10^-5 s per solar mass of the black hole.
> 
> Anything wandering into an event horizon is rapidly and brutally
> destroyed.  Under no cir***stances can such a particle ever
> escape, even if external geometries cause the shapes of event
> horizons to move around.
> 
> To put it another way, if you have a particle in an event
> horizon at a given point, and the external geometries change
> such that that point is no longer within the event horizon of
> any black hole (though even this idea gets difficult because of
> spacetime metrics), then that original particle is long since
> destroyed.

My thanks to Erik, Tim, and Wayne for clearing up my
confusion.

My original question was a request for some theorem along the
lines of the "Black holes have no hair" theorem, but it may
be that my question is too simple for anyone to have
bothered with such a theorem.

Let me try one last time to put my question, only now in
the terms which you three have offered me: Is it provably
impossible for a light-like or time-like worldline to
cross from normal spacetime to this "rotated" spacetime
/and back again/ to normal spacetime? It's looking like
the answer is, yes, it's provably impossible.

I think the source of my confusion is Frederik Pohl's
Heechee series, part of which takes place inside the
large black hole in the center of our galaxy. In his
universe, conditions inside a black hole aren't too
different from conditions in normal space.

He adds a touch of verisimilitude by saying that the
density of a really large black hole is about that of
somewhat crowded interstellar space. I know that
density goes down as black holes get more massive, but I
never ran the numbers on this point.

Unfortunately, it looks like even a supermassive
black hole is much too small to have a believable
interstellar density.

I'm assuming a black hole radius r = 2*G*m/c^2
and treating it like the radius of a normal
Euclidean sphere in order to get my black hole density.
I get
    m^2/d^3 = 3/(32pi)*(c^3*Y/(G*Ms))^3
where
    m = mass of black hole (in solar m*****)
    d = edge of cube containing one solar mass
          (in light years)
    c = speed of light
    Y = one Earth year
    G = Gravitational constant
    Ms = one solar mass

This gives me
    m = (7.92e18)*d^1.5
or a star-to-star distance of about a tenth of
a light /day/ implies a black hole of about
36e12 solar m*****.

Wikipedia says that super massive black holes mass
between 1e5 and 1e10 solar m*****. It seems unlikeley
that the Milky Way's own super massive balck hole
would be so far out side that range. So it's
unlikely that how Pohl represented the inside
of our black hole was accurate (unless there is
even more new physics to make it work out).

http://en.wikipedia.org/wiki/Supermassive_black_hole

Jim Burns