All Questions
Tagged with black-holes time-dilation
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Can black holes fully merge, according to a distant observer? [duplicate]
According to a distant observer, an object falling into a black hole doesn't disappear behind the even horizon but rather red-shift due to time dilation.
Does the same apply to merging black holes? ...
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When it comes to getting closer to the Schwarzschild radius, how is discrete a limit?
From Keeton (2014) in Principles of Astrophysics: Using Gravity and Stellar Physics to Explore the Cosmos, Gravitational time dilation near a large, slowly rotating, nearly spherical body, such as the ...
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Is it possible that the mass of a black hole is located at the event horizon?
Due to gravitational time dilation, an object falling into a black hole appears to slow down as it approaches the horizon, never actually reaching it. If it were to somehow enter the event horizon, ...
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Time dilatation of a free falling observer [duplicate]
I have two questions about time dilation near a black hole.
(I question) The relation $d\tau^2 = (1-\frac{r_s}{r}) dt^2$ between the proper time $d\tau$ of an observer near a B.H. and the time dt ...
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Does infinite time dilation increase a photons energy to collapse to a black hole, and does it do the same for matter?
As I understand the mass of an object doesn't increase in a gravitational field according to general relativity. It just follows a geodesic, its worldline.
Now imagine a small marble falling straight ...
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Observing an event horizon while approaching one
A thought crossed my mind that I realized was hard to conceptualize so I decided to simplify the question by putting it in terms of event horizons.
If I am an observer approaching black hole "A&...
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How would time dilation near a rotating black hole differ to a non-rotating black hole?
Suppose that we have a non-rotating black hole with mass $M$. We know that the time dilation $\Delta t'$ at a distance $r$ to the center of the black hole is given by $\Delta t' = \Delta t \sqrt{1 - \...
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Time dilation for different observer in black hole metric
If I have a 2d Schwarzschild metric
$$
dS^2 = -(1-\frac{r_s}{r})dt^2 + \frac{dr^2}{1-\frac{r_s}{r}}
$$
I want to find the relation between the time of an asymptotic observer $t$ and the proper time of ...
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Photon speed for an observer at the photon sphere [closed]
I am asked to compute the orbital period of a photon, in the Scwarzschild spacetime, at the photon sphere for an observer at the same radius, $r^\star=3M$. I have computed the result, $\Delta T=6\pi M$...
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What are the effects on a stationary observer at a specific distance from a Kerr Black Hole?
A Kerr Black Hole (BH) is a spinning BH. There is an Event Horizon (EH) which is
$$r_H^\pm =\frac{r_{S} \pm \sqrt{r_{S}^2 - 4a^2}}{2},$$
where $a = \frac{J}{Mc}$ and $r_{S}$ is the Schwarzschild ...
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Is it possible for things to fall past the event horizon? [duplicate]
Everything I can find says that time dilation approaches infinity at the event horizon of a black hole. Black holes evaporate over a finite amount of time. Wouldn't this imply that somebody falling ...
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A question about Kerr black holes and Hawking radiation
It's a common myth that somoene falling into a black hole will see the entire history of the universe before they cross the event horizon.
With a Kerr black hole however, it's sort of true. The inner ...
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If time stop at Sagittarius A event horizon, can time restart the other way inside? [duplicate]
From our point of view in our Galaxy, his center, Sagittarius A, is a super massive black hole. At event horizon of this singularity, gravity stop time.
Is there any reason why time would not run in ...
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Effects of acceleration and gravity on proper time
Let's consider the effects of gravity and acceleration on proper time of an observer (yes, I want to know how the equivalence principle works).
First situation: a spaceship with rocket engine stays ...
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When two neutron stars collide to form a black hole, for how long will last the emitted signal from the very vicinity of the new formed event horizon?
When two neutron stars collide they may form a black hole which is not a supermassive black hole but it should provoke that outside its newly formed event horizon photons are emitted as a consequence ...
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