All Questions
Tagged with black-holes causality
107
questions
4
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3
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318
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When can information escape from a black hole through a warp bubble-like spacetime?
It is well known that nothing can escape a black hole, including gravitational radiation. Many questions have been asked here about this topic, such as:
Can gravitational waves escape a black hole?
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- 4,080
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votes
1
answer
337
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What would happen if a black hole disappeared? [closed]
Imagine if a black hole disappeared. Would spacetime act like a rubber band and propel objects that used to be caught in its gravitational field outwards - i.e. some kind of space time explosion? How ...
- 131
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vote
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85
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How to describe ‘when’ a black hole actually is? [closed]
If I look at any point in space I can think of it as being in the future because it takes me time to travel there. I can go there and an observer can watch me go there.
When I look at a black hole I ...
- 740
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93
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Outer Apparent Horizon is a Null Hypersurface
Let $(N,h)$ be a 4 dimensional spacetime, $M$ be some spacelike hypersurface in $N$ and $S$ be some closed hypersurface in $M$. Let $K$ be some null normal field on $S$. This is the standard set up ...
- 111
2
votes
0
answers
34
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How can black holes emit detectable magnetic fields and gravity if nothing can escape the event horizon? [duplicate]
How can black holes emit detectable magnetic fields and gravity if nothing can escape the event horizon?
- 439
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answer
496
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Can gravitational waves escape a black hole? [duplicate]
I know that one of the defining features of a black hole is that all matter, including light, cannot escape a black hole. I was wondering if gravitational waves can. If this is true perhaps we could ...
- 290
2
votes
1
answer
176
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Near a white hole, what do lightcones look like?
In the vicinity of a Schwarzchild black hole, spacetime looks like this (at least according to a quick google search). Here, the centre of the black hole is supposed to be at $x=0$ and the event ...
- 77
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votes
1
answer
68
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Black hole, ingoing light-like and causality
In Kruskal-Szekerers coordinates, for example, I've noticed that ingoing light-like trajectories, in the interval $ 0<r<r_s$, are decreasing in time $t$ so they travel in the past for an ...
- 496
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votes
1
answer
64
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Schwarzschild radius violation?
I have a puzzling question concerning the crossing of the Schwarzschild boundary. If a person (lets say in some large robust spaceship) flys quickly between 2 super-massive rotating black holes within ...
4
votes
1
answer
395
views
Penrose diagram for two black holes
There are well-known Penrose diagrams for black holes:
And for collapsing star:
Diagram for collapsing star is obtained by joining two Penrose diagrams:
Is it possible to join diagrams for two ...
- 5,717
0
votes
3
answers
274
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Escape Velocity, Misattribution, and Black Holes
Escape velocity is the ballistic speed required to escape from a gravitational field to infinity, ignoring any third body dynamics. The operative word here being ballistic, meaning unpowered.
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- 136
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vote
2
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207
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Another form of Black Hole Information Paradox?
Consider the Penrose Diagram of Collapsing Gravitational matter :
Any radial light ray (say P) originating from $\mathscr{I}^{-}$ is bound to end up in the Black Hole. The ...
- 648
0
votes
0
answers
216
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What kind of causality would be broken if black hole singularities would be real?
In his article "The Universe as a Whole" 1, physicist Dennis Sciama said
We therefore face a crisis in theoretical physics. Either classical general relativity breaks down, or effectively ...
- 2,472
1
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2
answers
288
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Can you fall into a black hole, and then back out again?
There is a innumerable number of questions on this site about black hole event horizons, the possibility of falling in and back out again, but none of them answer my question specifically.
I have read ...
- 29k
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votes
1
answer
168
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What is a naked singularity?
What is a naked singularity? Would a naked singularity be one that that the event horizon is so small that it is the same size as the singularity? what could make one that small?
- 2,706