Black hole Definition and 999 Threads

Hello all, Thank you for taking time to read my question. I am curious, what happens if following criteria is met; 1. Place a indestructable stopwatch inside the black hole set it to 5 second 2. Place another stop watch outside of black hole and set it to 5 second 3. Place a...

Dear All Gravitinos, It seems that the current string theory and loop gravity's explanation for the micro-states of black holes are all quantum mechanical and have no classic correspondence. I, in this day's arxiv, post a pure classic interpretation for this question, titled "Black...

What happens when charged particles fall into a black hole? Say like N electrons fall in, giving the black hole a net charge of -N. Since light cannot escape the event horizon, I imagine electric fields cannot either, since they are mediated by photons. So is that charge effectively lost until...

Hawking showed that black holes dissipate energy when virtual particles are "emitted" by black holes and therefore black holes evaporate. However it seems to me that a shrinking black hole means a decrease in entropy and thus a violation of the second law of thermodynamics; is this the case?

Hello Friends... I just need a help... I want to kno what happens to the Singularity inside the black hole when it evaporates... Help me out[emoji5] [emoji5] [emoji5]

The reason I ask is that the singularity involves a region of spacetime composed of a different order of magnitude than i suppose the region outside the singularity.

Since a black hole goes to a singularity, theoretically wouldn't added mass to that point decrease the spacetime curvature by increasing of the circumference, and then not have a loss in information.

As I understand it, the crux of the issue is: how is information preserved across the event horizon, in this case, the arrangements of subatomic particles, atoms, etc right on up through the individual parts, etc., of the creature in question. That, and the relativistic escape velocity required...

Since black holes takes matter to a singularity, theoretically could there be a hole that does the opposite? As in push everything away like negative pressure.

If time does indeed come to a stop at the event horizon, how are we even able to observe it? Wouldn't it cease to exist to someone moving through time the moment time comes to a halt on the event horizon?

The angular momentum is related to the rotation. And when a black hole has angular momentum, it is said that it is a "rotating black hole". But what does it mean? A black hole does not have a conventional surface, like a basketball. How should we interpret that angular momentum? I asked this...

What has a higher density? Black Holes or Singularities? I looked online and all I saw was that they both have infinite densities.

Not to be confused with the full 3/4D one that I was plugging a while ago . . . this HTML5 canvas/JavaScript page was inspired by an old visual aid (requires Java plugin) that I found lacking in several areas. The improvements that I have made include: Handles spinning black holes, with...

Could there be outflows associated with the poles of a universal black hole? Could the pressure associated with the black hole’s dark energy emission cause particles of matter to form and accelerate outward? Is the timeline the time and distance from the black hole? Is this the cause of dark...

I am puzzled. Please help me out. Thanks. If we cross the horizon of Schwarzschild black hole horizon, we know that r becomes to timelike. Why the fututre is direction of decreasing r rather than increasing r?

Hello, I am Andika. What is the learning way to start learn black hole thermodynamics? Any references? Thanks!

hi PF, "TIME is reversed inside the even horizon" what does it means?. My sort of opinion is that for an observor outside the event horizon,the time becomes to move slow.but inside the event horizon it does not.Is that my opinion is correct or not about time reversal?? And "the black hole...

Homework Statement Consider a 2D spacetime with: ## ds^2 = g_{tt}dt^2 + g_{tx}(dtdx + dxdt)## where: ##g_{tt} = -x## and ##g_{tx}=3## Draw a spacetime diagram showing the null geodesics, including one which passes through the origin. Then show that for a massive object, when ##x## is positive...

Now my Kerr orbit simulator is pretty much feature complete, I have started to look at producing videos . . . I have just started a channel on YouTube to accumulate some of the more interesting examples. Aside from creating the simulation, the most difficult part was to generate useful initial...

I have a simple question about Lewkowycz and Maldacena's paper http://arxiv.org/abs/1304.4926v2'][/PLAIN] http://arxiv.org/abs/1304.4926v2 In section 2, they consider the scalar field in BTZ background ground and require boundary condition of the scalar field, $\phi \sim e^{i\tau}$ . This...

[Mentors' note: split off from this thread] Do all black holes have the same density?

OK, so it's time to start a new thread. I heard many times that there exists only one black hole solution for a given mass and angular momentum, but I know already that this is not true. We all know that if we throw something into an existing black hole, its event horizon starts to ripple. So...

How is information conserved when one form of energy is converted to other? Like how a black hole's gravitational energy is used to create photon pairs near the event horizon, what happens to the information in the gravitational wavepackets (gravitons?) and how is it not lost?

A black hole evaporates through hawking radiation, what I don't get is the requirement for an energy-negative energy pair production. Since it's the black hole's gravitational energy that's responsible for the pair production, even if one of them escapes, the black hole would lose energy anyway...

Assume a spherical black hole that is eating matter from its surroundings. Then its Schwarzschild radius will increase with a speed proportional to the mass flux that enters the black hole. The question is: is this speed limited by the speed of light in vacuum c? If the event horizon is a...

This is a somewhat weird question, but here it goes: What would happen if there were only gravitons? Would some other kind of particle appear in the Universe sooner or later? Would there be any chance for mass to appear in such a Universe (assuming that the graviton is a massless particle)...

In a couple of recent threads, I have attempted, unsuccessfully, to elicit a response to the following, which is my belief about why an observer standing well off from a black hole will in fact see the black hole evaporate (over a LONG period of time, of course, so the observer has to have an...

Premise 1: From the frame of reference of the earth, observing a thing falling into a black hole (crossing the Schwarzschild radius) is impossible -> the thing is observed falling toward but never reaching the radius, i.e. the process takes an infinite amount of time. Premise 2: Observation...

What would the final velocity of an object be as it falls into a black hole? I assume you could calculate the gravitational field strength of the black hole to determine the acceleration of the object and then calculate the final velocity with the equation V(final) = gt + v(initial)

Can someone point me to the seminal (or any other) paper explicitly showing and proving the formation of singularities in black holes? I'd like to learn about the exact physical processes which occur during the collapse of a star into a black hole and how the progress of those physical...

I was wondering what is known about the speed of objects falling to the centre of a Black Hole? If a number of identical objects, initially located outside the event horizon, were propelled at varying speeds towards a black hole, would that variability be maintained as they pass through the...

I was wondering about this for awhile and I still don't understand what happens to the enormous amount of mass stored in a black hole when it dies. I understand this question is based on a conclusion that may be incorrect, but if anyone could shed some light on this, please do so.

In various explanations of the event horizon which do not invoke the existence of a firewall (thereby upholding the dictum that an observer would not notice any difference upon passing the event horizon until she looked out the window), one uses the concept of a theoretical observer passing the...

What happens to the energy that goes inside a black hole. Will it stay there or get converted into some other forms of energy. What will happen to it?

HI, I need to calculate the variance of mass released when a particle jumps down or up between energy levels inside a black hole , i don't know where to begin any advice will help thanks

If the sun disappear right now, we won't notice before 8 and something minutes due to the speed of light. The Earth will keep going it's way on it's orbit because, as everything, gravity cannot exceed light speed. The same would apply if we were orbiting à black hole. I often heard of the...

I am reading about mergers of a neutron star with a black hole and the association with GRB. While talking about the accretion disk, the paper I am reading says about the last stable circular orbit. Firstly I thought it was where the Roche limit lies, where mass transfer or matter ejection from...

If we plug the Planck mass into the Bekenstein-Hawking formula for the BH entropy, we'll get S = A/4l^2 = 4πGM^2/cħ = 4π ≈ 12.56 nat for the minimal Schwartzschild black hole. If we assume that each entropy unit is a compact area on the horizon, can we consider the minimal BH a dodecahedron...

I have a question that when the fuel of star runs out there is a imbalance is temeperature-gravity equilibrium. When it collapses to a single point where mass gets compressed so much,but shouldn't the temperature at instant increase so much that the mass could not be compressed to infinite...

Naive reading on the web says that stellar collapse is halted by quantum mechanical processes called "degenerate pressures" that arise when gravity tries to force fermions such as electrons or neutrons into the same quantum state. White dwarfs are propped up by electrons, neutron stars by...

[Mentor's note: The thread title has been edited to change the level from "A" to the more appropriate "B"] Suppose there is planet Z revolving around black hole. Astronaut from Earth go in that Planet Z and start video recording and make a DVD . Suppose they played that DVD in the computer in...

The question is as follows: suppose I throw a metal bar 1m long inside the event horizon of a supermassive black hole of 1 million solar masses. At both ends of the metal bar there is a light source. (I chose a supermassive black hole to rule out any spaghettification process: with some quick...

I've recently read a new article that said that the recent gravitational waves might have had 2 black holes in a star that gave me a question, because you need masses to move or accelerate to generate gravitational waves, what happens to the mass inside of the star? because black holes's space...

I refer to the time coordinate of an outside observer (ideally hoovering over the BH at large constant distance). Can (s)he actually see something falling into the hole within finite time, that means actually disappearing and making the Event horizon larger? If no, all the merging of black...

According to the holographic principle, It is proposed that the entire information that is kept in a 3D volume of the black hole can be represented in a 2D surface of its horizon. What if we have a drunk falling into a black hole and moves in a random walk in his inertial frame. According to the...

(1) Maybe should've messanged this, but given LIGO, the FAQ might need a light edit. It says, "Gravitational waves have never been detected directly, but the loss of energy from the Hulse-Taylor binary pulsar has been checked to high precision against GR’s predictions of the power emitted in...

light waves created inside a black hole cannot. Can gravitational waves escape from inside of black holes? in classical GR. does the answer change in string theory?

Hi Folks, Can somenone explain what "information" is with respect to black holes? I thought it was all about mass and energy from both quantum Mechanics and GR perspective. Why does "information" come into it...sounds unusual to say the least. Thanks B

This question is in context of the recent gravitational wave detection by aLigo. Apparently aLigo has detected the entire process, including the before merger, during merger, and aftermath of the completed merger. My understanding is that two black holes should not be seen to be merging in...

http://cdn4.sci-news.com/images/2016/02/image_3628-Gravitational-Waves.jpg In the above image, i can see that the event horizon of each black hole has decreased in size. Does that mean that the event horizon can shrink in the presence of another black hole?