Re: A partial black hole?

On 29 veebr, 22:48, Erik Max Francis <m...@xxxxxxxxxxx> wrote:
sigidu...@xxxxxxxxx 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 blueshift, 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 redshift and trap EM radiation. Which effect would
dominate? (Or is it even possible to say?)

Causes redshift 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 redshift
takes place. From the frame of a hypothetical observer at the
singularity, things get infinitely blueshifted, 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.


.

Relevant Pages

  • Re: A partial black hole?
    ... -- If two black holes merge, what would a hypothetical observer inside ... Singularity A, can your course be shaped to fall into Sing B? ... Before crossing event horizon? ... Whether the black hole has a ring singularity ...
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  • Re: A partial black hole?
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  • Re: Inside a black hole
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