A black hole is a volume from which photons, or any matter, can not escape. More formally, the coordinate speed of light at the event horizon - the boundary of a black hole - is zero, as measured by a sufficiently separated observer.

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Interpretation of black hole area

I'm studying properties of Kerr spacetimes and a lot of fuss is made about area of BH. It is defined to be integral of area element on event horizon $r=r_+$, $t=const.$ where $r_+$ is radial ...
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What happens to quantum fluctuations near the schwarzschild radius?

I was reading about Feynman Diagrams and have gotten the impression that particle/anti-particle pairs are created fairly often given a large space. The surface area of a sphere with a radius equal to ...
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What is the difference between Reissner-Nordstrom (RN) black hole and dyonic black hole?

A RN black hole is a black hole with electric charge, and a dyonic black hole with both electric charge and magnetic charge. My Questions: Is the above statement correct? Is the charges the unique ...
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How will the Milky Way / Andromeda combined galaxy appear in 4 billion years?

In 4 billion years, do we we have an idea of what the combined Milky Way and Andromeda galaxy pairing will look like? In particular, will the presumed black hole at the centre of our galaxy, (and I ...
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Mass and Schwarzschild Radius [duplicate]

Do free massless particles have a Schwarzschild radius? I'm curious about the mass in the equation for the Schwarzschild radius. I know that you can calculate a Schwarzschild radius for any massive ...
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Is a black hole's mass uniformly distributed?

If you were to fly around a black hole, would the gravitational pull be uniform and centered on the singularity, regardless of your relative location? If yes, how can this be consistent with models ...
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Short Gamma Ray Bursts from black hole mergers

I have read in passing that short gamma ray bursts can be caused by the merger of 2 black holes in a binary system. I have Googled but can't seem to find any good sources describing the phenomenon ...
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What is the binding energy of a black hole?

As the particles which constitute a black hole collapse they become tightly bound. I assume this means a lot of energy would be required to liberate a particle from that bound state. Is it a finite ...
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Why we don't see time dilation in stars orbiting black hole?

We have images of stars orbiting black holes or black holes destroying near stars, but why do we see the stars moving normally? I mean, if time dilation does exist, shouldn't we see that stars slow ...
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Why do physicists trust black hole physics?

Based on popular accounts of modern physics and black holes (articles, video lectures), I have come to understand the following: Black holes are predicted by General Relativity, a classical theory ...
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Do the stellar remnant in a black hole have spatial extent? [duplicate]

I am not talking about event horizons. I am talking about the actual remnant of stellar collapse. Is it just a point, hence the problem with the singularity? Or does it have a finite volume that we ...
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Are black holes eternal?

The question might sound very easy - Hawking radiation, however I was pondering that as you get closer and closer to a black hole, time dilates exponentially where the surface of the black hole is ...
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Is the event horizon of black holes visibly sharp, or blurry?

As you come in closer to a black hole, how do you see the event horizon? Is it always like a clear-cut surface? Or it only looks clear-cut from a distance, but as you come closer to the black hole, ...
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Theoretical relativity of black hole and antimatter [closed]

(Theoretically), can black holes be considered antimatter that just cancels its equivalent mass and goes back to neutral stage? Note: Be kind I am not a physicist .
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How can an infinitesimally small object rotate?

How is it possible for an object like a black hole or electron to spin since they are made up of no other components? If my understanding is correct, an electron is an elementary particle which means ...
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How can we detect a black hole accurately?

I know there are many ways in detecting a black hole, but there are odds against them too. So I wanted to know a accurate method to detect a black hole. Here are the known methods to me and the odds ...
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Can we see the photon sphere from outside? [duplicate]

This question came to my mind when i saw the movie interstellar. In the movie there is a scene with a black hole and a sphere of light around it, what i assume to be the photon sphere. You can see it ...
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Do all stars Turn into Black Holes? [duplicate]

If all stars turn into black Holes one day, in far future, what will happen to Earth if Sun becomes a Black Hole.
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Definition of event horizon - Gravity around blackholes [closed]

Put simpler: A black hole is surrounded by a 'sphere' where, to an outside observer. the speed of light is (near) zero. What is the radius of that 'sphere' (for a non-rotating black hole) and how ...
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Possible paradox with black holes and time dilation [duplicate]

I am by no means an expert in the realm of physics. I do from time to time, try to understand the concepts of modern physics and their applications. I came across this video that I am currently ...
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How does a Black hole attract light? [duplicate]

Please no hate for lack of knowledge: I am somewhat fascinated with the subject of black holes. However, I do not understand a concept which is constantly attributed with black holes: that a black ...
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How long can a particle survive inside of the horizon of a black hole?

By examining the causal structure of a Schwarzschild black hole, one can see that a particle in region II is unable to escape to $r=\infty$. Such diagrams do not show, however, how long a particle ...
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How does one correctly interpret the behavior of the heat capacity of a charged black hole?

Note: Although I have a provided an "answer" to the question, I did not resolve all the questions in this post satisfactorily. I invite anyone willing and able to provide a better answer, which I ...
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global transformations in 3d gravity

I am currently working on proper and improper gauge transformations in 3d gravity and btz black holes. (because I have seen it defined with many different ways I will just say that with "proper"and ...
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Are temperature and chemical potential of a black hole independent quantities?

I am a bit confused about the independent parameters in a charged black hole in AdS spaces. From equation (63) of this lecture notes we see that the temperature (T) of the black hole has chemical ...
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Black Hole Growth

When a black hole increases in size by engulfing matter, does this matter fall into the event horizon or does it just rotate around the accretion disk? EDIT: Clarified the beginning of the question. ...
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Do black holes violate the uncertainty principle?

If black holes have mass but no size, does that imply zero uncertainty in position? If so, what does that imply for uncertainty in momentum?
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Connection between Black Hole Firewalls and Hawking Radiation

In a previous post, I asked what constitutes a black hole firewall--namely, what is a possible mathematical description of the firewall. Now I have a new question, which is based around this guest ...
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Problem with black holes?

I understand that black holes are formed when supermassive stars (>10 times the size of our Sun) die. When they die, their cores continue to shrink. I have read that eventually the core reaches a ...
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What constitutes a blackhole firewall?

I understand that, to break the entanglement of two particles of Hawking radiation and therefore preserve monogamy of entanglement, there should be a firewall around the event horizon. This firewall ...
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Why don't electrons collaspe into black holes? [duplicate]

An electron has a mass of $9.10938291(40) \times 10^{−31} kg$. It also has a volume of $0 m^3$. This would imply it has infinite density. Shouldn't that make it collapse into a black hole? Why doesn't ...
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Can we observe a star collapse into a black hole? [duplicate]

Let's say that I happen by a star that has just burned out and is collasping into a black hole. I seat at infinity to watch it as a Schwarzschild observer. Will I ever see the black hole collapse into ...
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Size of black hole so large that I could pass event horizon without dying from tidal forces?

Were I to fall towards a typical black hole, the tidal forces would rip me apart well before I got to the event horizon. However, if a black hole were big enough, I could enter the event horizon ...
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Free-fall path into a black hole in Kruskal Coordinates

If an object at t=0 begins to free-fall into a black hole from X in Kruskal coordinates (https://en.wikipedia.org/wiki/Kruskal%E2%80%93Szekeres_coordinates), what does its path on the Kruskal-Szekeres ...
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Would infinite material cause a black hole?

If you have an infinite amount of any material(That doesn't have a critical mass to have nuclear reactions), would this matter form massive black holes that condense into an infinite black hole? Two ...
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Rigorous Proof of General Relativity's Non-renormalizability?

The answer to this question and the comments on it implies that general relativity has not been rigorously shown to be non-renormalizable for all loop diagrams -- only shown for two loops. However, ...
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How is the first law of black hole thermodynamics formulated for a non-vacuum solution with event horizon?

How is the first law of black hole thermodynamics formulated for a non-vacuum solution with event horizon?
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Black Hole surface area at Schwarzschild radius is half?

I have been interested in black holes for some time, and am still trying to wrap my head around some of their more obscure properties. Now I know that the Schwarzschild radius is $r= ...
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Any interesting implications of a holographic black hole in a holographic universe?

Bear with me; I don't have a background in physics, nor am I sure I even understand the things I'm talking about. I recently read that math/physics for a holographic black hole could be applied to ...
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Help me calculate the Euclidean action of a gravitating system!

I recently read Gibbons and Hawking's paper Action integrals and partition functions in quantum gravity, Phys. Rev. D 15 (1977) 2752. I am interested in repeating their calculations. It is fairly ...
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If a super massive black hole captures a very small black hole, would the smaller black hole be immune to spaghettification?

I think to answer this question we would have to fully understand the nature of black holes. It seems to me that the smaller black hole could have a lower density than the larger one. In this case the ...
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Does the uncertainty principle affect event horizons? [duplicate]

I was thinking about black holes. For a simple black hole the event horizon is given by a distance of 2 times mass (energy) of the black hole. (2m). But according to quantum mechanics, if you try to ...
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Wave equation on Schwarzschild background

I am trying to follow the solution of the wave equation for a scalar field on Schwarzschild background from http://batteringram.org/science/gr/scalar_wave.pdf. I have a problem on page 2 where they ...
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How can a singularity have infinite density? [duplicate]

I've heard many times that black holes have infinite density at their center, but I've also heard astronomers quote mass estimates for black holes. How could the singularity have infinite density if ...
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Path of light as it travels between two black holes

What would happen to light passing through a narrow space between the event horizons of two equal-mass black holes? Would it deviate or follow a straight path?
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Can tachyons escape the gravitational pull of a black hole?

Anything that crosses the event horizon of a black hole cannot escape the pull since it has crossed the Schwarzschild radius and thus, the escape velocity is greater than the speed of light, and since ...
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Is there any good literature about conceptual designs of Quantum (Micro-) Black Holes Machines?

I did some research and found this book: Quantum Black Holes, 2014 http://link.springer.com/book/10.1007/978-3-642-38939-9 It seems good for a repetition of current status of (Quantum) Black Hole ...
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What is the radius of the event horizon?

I know that the Schwarzschild radius is given by $$r~=~\frac{2GM}{c^{2}}.\tag{1}$$ However, If we had the metric $$ds^2~=~−A(r,t)dt^2+\frac{dr^2}{B(r,t)}+r^2(dθ^2+\sin^2{θ}dϕ^2),\tag{2}$$ where ...
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How to derive the Schwarzschild radius? [duplicate]

I know that the Schwarzschild radius is given by $$r=\frac{2GM}{c^{2}}.$$ but I never seen a derivation for this equation. 1- Does anyone know how to derive this equation from general relativity? ...
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The age of black holes

I have a very small understanding of space-time however I have been watching some interviews and reading articles featuring theoretical physicist Kip Thorne and I have a few questions that I hope can ...