All Questions
61
questions
2
votes
1
answer
161
views
When you are in a gravitational field, do object far away get physically closer to you as you get closer to the mass?
An observer A is close to a black hole and an observer B one light year away. They are both remaining at constant radial distance from the black hole. A is at 2 Rs away from the center of the black ...
- 171
1
vote
2
answers
110
views
If Hawking radiation is observer dependent then is the mass of a black hole too?
I have read this question (in the comments):
Late response, but the energy really comes from the gravitational field, which exists outside the event horiz0n and in space. This field is what lets us ...
- 29k
1
vote
0
answers
101
views
Relating Minkowski and Schwarzschild
In the article https://arxiv.org/abs/gr-qc/0309072 the author finds a link between Minkowski coordinates of a freely falling observer and Schwarzschild coordinates. He makes use of a Galilean ...
- 127
2
votes
2
answers
245
views
What is the perceived shape of a non-spinning black hole as it is approached at high velocities?
The question and answer at What is the shape of a black hole? states that an event horizon " is indeed a sphere." But if it is approached at high velocity, does the traveler calculate that ...
- 480
1
vote
2
answers
2k
views
How much Earth time passes over a 1000 lightyear journey?
Ok, so I'm writing a sci-fi novel featuring a lot of interstellar travel. I was wondering how much time would pass, from an Earth-based perspective, if I were to travel 1000 lightyears from Earth, and ...
- 1,552
0
votes
1
answer
99
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How does a black hole's surface area transform relativistically? [duplicate]
Perhaps a bit of a strange question. I know the traditional way of finding a black hole's surface area is through the Schwarzschild radius,
$$
r_{\rm{Schwarzschild}}=\frac{2GM}{c^2}
$$
however, that ...
- 48
0
votes
1
answer
83
views
If the Earth is placed between three spinning black holes, Will time on Earth slow down? Will we live longer?
Just randomly thought of placing the Earth equidistant from 3 spinning black holes. Will time on the Earth slow down? Will we age slower? Assuming that the Earth is not past the event horizon yet the ...
- 9
8
votes
4
answers
1k
views
A small black hole asymptotically approaches a big black hole's event horizon. Will it seem to be frozen there, or will it seem to merge?
On this site, there are currently two scenarios described:
two black holes merge in a finite time
in any sensible meaning of the term merge the two black holes do indeed merge in a finite, and very ...
- 29k
6
votes
2
answers
750
views
Can a Kerr black hole be viewed as a Schwarzschild black hole by changing the frame of reference?
In a local universe empty of any matter except a Kerr black hole and an observer, that observer is spinning at the same rate as the black hole and observes it from a great distance directly above its ...
- 643
-1
votes
1
answer
69
views
Black holes by blueshifted light
If you can make black holes out of light you can make black holes out of light that is emmited from the moving frame and concentrated into one spot and that would not have enough energy to form a ...
1
vote
0
answers
64
views
Objects A and B fall into a black hole. B is released 1s after A. How do A and B see each other's trajectories? Esp. when crossing the event horizon?
Imagine we have three observers, A, B and C, all standing on a platform hovering just outside the event horizon of an ideal Schwarzschild black hole$^1$. At time $t=0$, as measured from the platform, ...
- 1,246
-1
votes
1
answer
252
views
Race to the singularity, who wins, the photon or the neutrino?
There are a lot of questions and answers about speed falling into a black hole, none of them answer my question. Most of them only talk about speeds outside the event horizon. The only relevant answer'...
- 29k
1
vote
1
answer
69
views
Conditions for Schwarzschild Metric to be applicable
The Wikipedia article regarding the two-body problem in General Relativity states that the Schwarzschild metric "corresponds to the external gravitational field of a stationary, uncharged, non-...
- 2,712
14
votes
6
answers
4k
views
What do black holes spin relative to?
What do black holes spin relative to?In other words, what is black hole spin measured in relation to?
Spinning black holes are different from non-spinning black holes. For instance, they have ...
- 657
2
votes
1
answer
171
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Do black holes present a contradiction in our understanding of GR? Or... what happens to the observer after infinity? [closed]
There have been some lengthy discussions, here and here (among others), about whether, to the distant observer, black holes form in a finite time or an object falls into a black hole in a finite time. ...
- 204