Re: A partial black hole?

On 29 veebr, 22:48, Erik Max Francis <m...@[EMAIL PROTECTED]
> wrote:
> sigidu...@[EMAIL PROTECTED]
 wrote:
> > Granted that nothing can escape an event horizon, some other questions
> > do come to mind.
>
> > -- If two black holes merge, what would a hypothetical observer inside
> > the event horizon of one of them see?  If you're falling into
> > Singularity A, can your course be shaped to fall into Sing B?
>
> I don't know.  I doubt it.
>
> > -- Spinning black holes supposedly have ring-shaped singularities.  I
> > assume there's still no way to avoid falling into the singularity?
>
> You can avoid hitting the singularity, but you still have to pass
> through it, which means you experience infinite blue****ft, which
> destroys you anyway.
>

Wait, what exactly happens to you?
And when? Before crossing event horizon? Before crossing Cauchy
horizon? Before crossing equatorial plane?

> > -- So you fall into a (very large) black hole and look inwards towards
> > the singularity.  What do you see?
>
> The incidental matter that was in front of you before you fell in (as it
> fell in too).
>
> > As the matter that creates the singularity contracts, presumably it
> > would heat up, causing it to radiate.  As its density increased
> > endlessly, so would its temperature, and the frequency of the
> > radiation emitted.  On the other hand, its intense gravitational field
> > would tend to red****ft and trap EM radiation.  Which effect would
> > dominate?  (Or is it even possible to say?)
>
> Causes red****ft according to whom?  To radially distant observers (who
> are still inside the horizon), maybe, but they're falling in too, so
> that hardly matters.  Observers outside of the black hole see nothing.
>  From the frame of the thing falling in and heating up, no red****ft
> takes place.  From the frame of a hypothetical observer at the
> singularity, things get infinitely blue****fted, but then again, there
> can be no such observer.  So it sounds like your question is ill-formed.
>
I think what was contemplated was a pair of objects which both are
falling into the same black hole,  A ahead of B. A is emitting light
(time signals) til it hits singularity.

None of the signals emitted by A after crossing singularity are
observed outside event horizon - all light emitted by A eventually
reaches singularity. But can B, while on its way down to singularity,
observe signals emitted by A?

> > Also, how would the "singularity always ahead of you" effect appear to
> > our hypothetical free-falling observer?  Would the singularity seem to
> > be everywhere at once, filling the sky?  Or would it simply be
> > unavoidable -- no matter how you fire your rocket, you end up falling
> > towards it?
>
> The singularity pretty much by definition is a place where all timelike
> and lightlike paths end.  Once a worldline hits the singularity, nothing
> more can happen.  Thus no photon can ever go from the singularity
> radially outward, even if the spacetime allowed it (which the inside of
> a black hole does not).  The singularity is not visible, even once
> inside the event horizon.
>
> > As you got closer to the singularity -- putting aside
> > spaghettification issues, at least for as long as possible -- would
> > its appearance change?
>
> You never see it, no matter what you do.  But it quickly kills you.
>