All Questions
303
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Energy of the gravitational field within a sphere of radius $R$ in the Schwarzschild metric
The Landau-Lifshitz energy-momentum pseudotensor $t^{μν}$ is defined by
$$16πt^{μν}
= -2G^{μν} - g^{-1} \left[ -g \left( g^{μν}g^{αβ} - g^{μα}g^{νβ} \right) \right]_{,αβ}$$
where $g=\text{det}[g^{μν}]...
- 366
1
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0
answers
50
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Does gravity accelerate you towards the geodesic of light between you and the mass?
If there's a planet far away, you will accelerate straight towards it due to gravity. If you place a Schwarzschild black hole right in the middle between you and the planet (the distance between the ...
- 171
4
votes
1
answer
197
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Binary black hole merging condition
Assuming two black holes with the same rest mass $m$ collid coming from infinity with velocity $v$ and impact parameter $b$. Lets ignore spin at first. For which values of $v$ and $b$ would these ...
- 41
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2
answers
83
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How could I calculate the time it will take for light and mass to go towards a black hole and come back, to and from constant radial distances?
If you have a "perfect mirror" and a "perfect trampoline" at some constant distance outside a black hole's event horizon:
a) How would a shell observer at some distance farther ...
- 171
4
votes
1
answer
169
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How are objects inside a black hole affected by the gravity of objects outside the black hole?
There are many Q&As about whether something inside a black hole can escape the event horizon if another massive object gets close enough to pull it out. I realize the answer (I think universally ...
- 450
5
votes
2
answers
805
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Are light rays always bent in any gravitational field, or just in a strong one like a black hole?
This is a follow-up question after this one:
Yes, the curvature is enough to bend lasers. In fact, there is an interesting feature in Schwarzschild spacetime that might answer your question well. ...
- 29k
7
votes
3
answers
1k
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What would the collapse of a neutron star into a black hole look like from the center?
I have read this question (unfortunately this mentions supernova and not black hole):
If it it the latter, then the instabilities that lead to the collapse of a neutron star would begin near the ...
- 29k
1
vote
1
answer
156
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Can a single black hole emit gravitational waves and evaporate?
I have read this:
Yes, single neutron stars can emit gravitational waves if they have sufficient asymmetries.
For some background, an object symmetric about its axis of rotation does not produce ...
- 29k
1
vote
1
answer
63
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Definition of surface gravity via the non-affine geodesic equation
I have found a discrepancy in the way different sources define surface gravity (or derive) via the non-affine geodesic equation satisfied by the a Killing vector $\xi$ on a Killing Horizon (KH), up to ...
- 1,989
1
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0
answers
51
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Newtonian approximation for the tidal forces at the event horizon of a black hole
I'm currently working on a problem where I have to calculate the tidal forces a person experiences if their feet touches the Schwartzschild radius and their head is $1.8m$ elevated above the ...
2
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0
answers
61
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How much of an observer's field of view will be black upon crossing an event horizon? [closed]
The aberration of light will cause an observer to still see a black hole as "distant" when the event horizon is crossed.
This means that if the observer looks directly toward the center of ...
34
votes
8
answers
9k
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Why does Roy Kerr claim that the Kerr black hole does not contain a singularity?
In a preprint posted on the arXiv, Roy Kerr claims that there is a widespread misunderstanding related to the singularity inside the black hole that bears his name.
Can anyone explain his argument in ...
- 2,136
4
votes
1
answer
843
views
How are white holes described as outgoing spacetime and still have attractive gravity?
White holes are described by the time reversed Schwarzschild metric. A test particle which is gravitationally attracted to the black hole's event horizon in the Schwarzschild metric is also ...
- 476
0
votes
1
answer
54
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Examples of black hole analogues
After spending some time looking for different means and mediums to model blackholes, I came across sonic holes which are modeled through Bose-Einstein-Condensates.
However I have not been able to ...
- 166
0
votes
4
answers
244
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Can Schwarzschild acceleration be written in exact form as a function of position and velocity vector?
For the special case of only one massive point-shaped or spherically symmetric non-rotating body and a small "test mass" body under general relativity the movement of that small body is ...
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