Black hole Definition and 999 Threads

Is there time inside of a black hole?

Hi, I am not too sure where to post this. I am studying for my astrophysics final and I came across this question which is pretty easy ( I think) but I can't seem to find the answer... S2 is observed to be one of the brightest stars orbiting the black hole at the center of Milky Way. It has...

So I have a question about Sagittarius A*, which more and more astrophysicists are certain is a supermassive Black Hole. But now for the evidence part: 1. An alternative model for this object was proposed http://journalofcosmology.com/RobetsonLeiter.pdf published 4 years ago. So is there any...

(Correct me if you think I'm wrong in anyway, I am open to new ideas.) A black hole is created when a planetary mass has its atoms completely cave in on its self. This creates a massive amount of gravity, one so massive that it even attracts photons (light). So does this mean that a black hole...

Hello, if you could help, I will be glad. I am studying the Einsteins-Rosen bridge (a matematically solution of the black hole) and I thought that the Einsteins-Rosen bridge was what we found making the Schwarzschild metric a change in kruskal coordinates. But reading an scientific article it...

Suppose a black hole travels at something like v = 0.999999999c relative to some observer. Does the black hole's event horizon becomes length contracted, thus appearing to turn into a black disk?

Hello, I am interested in surface gravity of Kerr black hole it means, I need to find killing vector for Kerr which is null on outer horizont. Is it true? How should I do that? I guess it could be some linear combination of vecotrs ∂/∂t and ∂/∂\phi. So can I looking for that this way...

Since light has no MASS... Then how does a black hole absorb light?

Here is my basic question: Lets say we have a massless charged shell with charge q and radius R. Is there some R where a black hole is formed? I haven't work this out with the EFE, but the calculations I've done are relativistic (GEM equations instead of EFE, for simplicity). I found that...

I have a question pertaining to objects falling through the event horizon of a black hole. It is my understanding that due to the immence gravity of a black hole and the way gravity affects the flow of time, that from the point of view of an observer at a safe distance from a black hole...

Lets say we have a couple objects, one very close to a black hole, one a little farther out and then one a good distance away. Would the one very close to the black hole see the other ones time moving much quicker than their own time? How about just as they are going to hit the event horizon...

Requested info for a sci-fi short story I'm writing: You are approaching the event horizon of a supermassive (10 billion Solar masses) Schwartzchild black hole in a magical spaceship which is capable of violating the laws of physics. You have not been free falling but lowering into the hole...

Hi, I've heard and read that if someone was to fall towards a black hole, say feet first, they would undergo spaghettification at a certain distance, as the gravity at their feet would be much greater than the gravity at their head, and their body wouldn't be able to reisist the pulling effect...

Imagine a spinning skater. She pulls her arms in a little and spins faster. She brings her arms all the way into her chest, and spins really fast, and then bam! she rockets up into the sky. Seven years ago, computer simulations revealed a configuration of two spinning black holes that merged in...

I think I am wrong in what I am about to say so I someone could explain relatively simply where I went wrong I would be thankful... When light travels towards a black hole it's wavelength increases it's frequency and decreases it's wavelength due to the increase in energy. Because a black hole...

The FAQ states: "In our universe, we observe that space is not a vacuum, and tidal forces are nearly zero on cosmological distance scales (because the universe is homogeneous on these scales). " We observe Dark Energy. How do we know this accelerated recession of distant galaxies, which is...

First off I couldn't decide whether to enter my question in the relativity section or this one, so if I'm in the wrong place my apologies. Anyway I have a question or perhaps a hole in my understanding. I was wondering if there is a density point at which anything becomes a black hole. Now I...

Hi, does anyone know how much of the universes's iron or carbon has been made in supernovae that formed black holes? Is it 5, 10, 50 % of the iron currently pressent here? And, if se, do we have any idea how much of the average stars content gets traped in the BH versus the mass of the...

Hi, I think I have several misconceptions about the theoretical framework of black holes, I'm just not sure where my intuition (or, lack of) goes wrong. So sorry if this sounds really stupid, any help is appreciated. The scenario that I find confusing is what Alice sees when she throws Bob into...

I was thinking about how a black hole evaporates and the firewall idea. If after Page time a firewall forms around the black hole, does that mean that the energy/mass, and entropy cannot increase anymore? The energy of the black hole is essentially supposed to be in the singularity, right? I...

I thought this was cool, wasn't able to find a paper on it, but didn't look "super hard", and won't pay for it. Apparently, a gravitational lensing has lined up so perfectly that we were able to measure the black hole's spin. They have it at "half the speed of light" (??!)...

Assume that there exist two people, person A and person B. Person B is falling into a black hole. I understand that due to relativity and time dilation, person A will have to spend an infinite amount of time to watch person B cross the event horizon. Person B will appear to move at a slower...

I know several raytraycing results for static Schwarzschild black holes, but I have never seen something similar for collapse models like Oppenheimer-Snyder or Vaidya. Are there reliable raytraycing results showing the effect on light rays from far distant light emitters observed by (far...

In a Kerr Black Hole there exists a region called the Ergosphere. It is between the Event Horizon and a spheriod called the Static Limit. The Event Horizon can be simplified to: ##\Delta## = 0. The Static Limit can be simplified to: ##g_{tt}## = 0. They yield two separate spheres...

Homework Statement How do you find the Angular Momentum, J, if you are given the Angular Velocity, ω of a Kerr Black Hole. Homework Equations J = I*ω ##I = mass*r^2## Event Horizon: ##r_+ = M + (M^2 − (J/mass/c)^2)^{1/2}## Static Limit and the Ergosphere: ##r_0 = M + (M^2 −...

Suppose Alcubierre warp drives or some alternative form of warp drive is possible. Then surely a warp drive could enter the event horizon of a black hole, observe the interior, and exit the horizon, returning with information from within the black hole. What about black holes never visited by a...

In another thread we determined that the proper total force acting on an orbiting object in the Schwarzschild metric, is given by: ##f_{total} = \frac{Mm}{r^2\sqrt{1-2M/r}} - \frac{mv^2}{r}\left(\frac{1-3M/r}{(1 - v^2)\sqrt{1-M/r}}\right)## One interesting aspect of the equation is that when...

If light approaches a black hole will it accelerate? I think this question ties in with whether light has mass or not. Does light have mass? It seems accepted that light has momentum, but this is not consistent with saying that photons are mass-less (momentum=mass*volume). Could someone clear...

Hey all, I was wondering if the singularity at the bottom of a black hole is similar to what the universe would be like before the big bang, i.e. heaps of mass/energy concentrated into a tiny point. To me I always think of black holes as sinkholes dotted throughout the universe which are...

Would it be possible for a black hole to carve a trail of information on two dimensional space in the holographic universe? Could the black hole, acting as a conduit between the macro and micro universe, due to its properties at the singularity (at the plank scale) carve the the information...

If the amount of hidden information inside a black hole, depends on the size of the hole, one would expect from general principles, that the black hole would have a temperature, and would glow like a piece of hot metal. But that was impossible, because as everyone knew, nothing could get out of...

Hello everyone. As far as I know, even lights can not escape from black hole once the light reaches to even horizon as lights carry momentum hence energy. Now, what I wonder is, how fast do black holes swallow light or, if you will, other objects? I guess it cannot be faster than the speed of...

Hey, so I've been wondering about this question for a while and was wondering if anyone could support the Big Bang theory in this respect or anything else. Just wondering if anyone has an answer that might aid me in understanding this, thanks.

Hello. I was reading through Black holes and what happen when information falls inside the black hole. The intellectual battle between Susskind and Hawking...I also heard through the lectures on Susskind describing what is information. (a) Bits (b) A single photon (c) The n number of...

Here's the best of my understanding of the official explanation of what happens when O' fall in a black hole. eternal black hole For an outside observer O, O' slow down more and more as you approach the event horizon, at the event horizon time seems to completely stop. In the reference frame...

As you guys probably know, as an objects speed increases, so does its mass. I was wondering if a black hole could be induced by speeding up a neutron star or some other massive object with high density to high speeds? Also, what is the equation that explains this phenomena? Also, if this is...

Hi. I was wondering about this. In the "Star Trek" movie of 2009, the destruction of the planet Vulcan is shown, by a black hole being formed in its core. I'm curious: supposing you had some means to create, or collapse part of the planet to form, a black hole in its core, what would, according...

Hello? I have a doubt about black holes energy.I am curious about that.What is the Black Holes energy? Thanks for Help

In the big crunch scenario, matter would clump together faster and faster, could a blob of this matter form a black hole, even if it had the necessary energy to maintain fusion or if it had no energy to burn up the matter? If the big crunch were to happen, and a single blob of mass existed at...

I asked a question recently about orbiting black holes. Thanks for the answers. So if I'm correct in my thinking, long before the event horizons of orbiting black holes become close to each other, the two accretion disks get mightily disrupted and much of the mass of the two disks would fall...

A recent APOD page discussed jets ejected from black holes. It said, "Recent evidence indicates that these jets are composed not only electrons and protons, but also the nuclei of heavy elements such as iron and nickel." What is thought to be the mechanism of production of these heavy nuclei?

In the "closed" Friedmann model, there is a Big Bang in the past and Big Collapse in the future. Big Bang singularity is something different than a Black Hole singularity. Now my question: is the Big Collapse singularity mathematically equivalent to a Black Hole (localized) singularity, or is...

Homework Statement Astronomers believe that there is a massive black hole at the center of the Milky Way galaxy. What evidence is there for that? A group of astronomers have observed a star "S2" in a 15.2-year orbit around the center of the galaxy. They measured the period of revolution T =...

Hi, two questions A) If a black hole travels into a wormhole would it collapse the wormhole? B) If a wormhole travels through another wormhole what would happen? Thanks for any help.

Can a black hole be a portal to another dimension?

I've read that there's a point in a black hole where matter is infinitely dense. There is zero volume but infinite density. How is it possible for something to have zero volume but have an infinite density at the same time?

I've never fully understood how anything can actually fall into a black hole without the black hole evaporating first. Since time dilates exponentially as I fall into a black hole, a point will come where a few seconds for me will be millions of years in the outside world...trillions in fact...

Homework Statement This is the original problem for part 1 A) Suppose that a black hole of mass M accretes mass at a rate ##\dot{M}##. Further suppose that accretion of mass Δm leads to the radiation of energy ##\Delta E= \eta Δmc^2##, for some effeciency of energy conversion, ##\eta##. What...

Homework Statement Suppose that a black hole of mass M accretes mass at a rate ##\dot{M}##. Further suppose that accretion of mass Δm leads to the radiation of energy ##\Delta E= \eta Δmc^2##, for some effeciency of energy conversion, ##\eta##. What is the luminosity of emitted radiation in...

If a distant observer were to observe a large cube made of strong material approach a black hole, what would he see? ISTM that if one of the faces of the cube were to be the nearest approaching portion, he would see the four edges of the face become shorter and curved, and he would see the...