A black hole is a region of spacetime where gravity is so strong that nothing—no particles or even electromagnetic radiation such as light—can escape from it. The theory of general relativity predicts that a sufficiently compact mass can deform spacetime to form a black hole. The boundary of no escape is called the event horizon. Although it has an enormous effect on the fate and circumstances of an object crossing it, according to general relativity it has no locally detectable features. In many ways, a black hole acts like an ideal black body, as it reflects no light. Moreover, quantum field theory in curved spacetime predicts that event horizons emit Hawking radiation, with the same spectrum as a black body of a temperature inversely proportional to its mass. This temperature is on the order of billionths of a kelvin for black holes of stellar mass, making it essentially impossible to observe directly.
Objects whose gravitational fields are too strong for light to escape were first considered in the 18th century by John Michell and Pierre-Simon Laplace. The first modern solution of general relativity that would characterize a black hole was found by Karl Schwarzschild in 1916, and its interpretation as a region of space from which nothing can escape was first published by David Finkelstein in 1958. Black holes were long considered a mathematical curiosity; it was not until the 1960s that theoretical work showed they were a generic prediction of general relativity. The discovery of neutron stars by Jocelyn Bell Burnell in 1967 sparked interest in gravitationally collapsed compact objects as a possible astrophysical reality. The first black hole known as such was Cygnus X-1, identified by several researchers independently in 1971.Black holes of stellar mass form when very massive stars collapse at the end of their life cycle. After a black hole has formed, it can continue to grow by absorbing mass from its surroundings. By absorbing other stars and merging with other black holes, supermassive black holes of millions of solar masses (M☉) may form. There is consensus that supermassive black holes exist in the centers of most galaxies.
The presence of a black hole can be inferred through its interaction with other matter and with electromagnetic radiation such as visible light. Matter that falls onto a black hole can form an external accretion disk heated by friction, forming quasars, some of the brightest objects in the universe. Stars passing too close to a supermassive black hole can be shred into streamers that shine very brightly before being "swallowed." If there are other stars orbiting a black hole, their orbits can be used to determine the black hole's mass and location. Such observations can be used to exclude possible alternatives such as neutron stars. In this way, astronomers have identified numerous stellar black hole candidates in binary systems, and established that the radio source known as Sagittarius A*, at the core of the Milky Way galaxy, contains a supermassive black hole of about 4.3 million solar masses.
On 11 February 2016, the LIGO Scientific Collaboration and the Virgo collaboration announced the first direct detection of gravitational waves, which also represented the first observation of a black hole merger. As of December 2018, eleven gravitational wave events have been observed that originated from ten merging black holes (along with one binary neutron star merger). On 10 April 2019, the first direct image of a black hole and its vicinity was published, following observations made by the Event Horizon Telescope (EHT) in 2017 of the supermassive black hole in Messier 87's galactic centre. In March 2021, the EHT Collaboration presented, for the first time, a polarized-based image of the black hole which may help better reveal the forces giving rise to quasars.
As of 2021, the nearest known body thought to be a black hole is around 1500 light-years away (see List of nearest black holes). Though only a couple dozen black holes have been found so far in the Milky Way, there are thought to be hundreds of millions, most of which are solitary and do not cause emission of radiation, so would only be detectable by gravitational lensing.
Let's say Bob falls into a blackhole, and Alice is sufficiently far away that she is not falling in. She sees Bob's clock stop and his image fade away and all that. However, from Alice's perspective Bob never actually crosses the horizon. From her perspective, Bob is sitting frozen and invisible...
From what I understand about time dilation and the relativity of simultaneity; if we imagine two people near a black hole and one of them begins to approach the black hole on a trajectory that crosses the event horizon. The stationary observer will never see the moving observer enter the black...
I was wondering if someone can help explain to me what is happening in the image.
Black holes have Light paths or something
so i read here more accurate description is that within this horizon, all lightlike paths (paths that light could take) and hence all paths in the forward light cones of...
Has anyone else heard of that gravity waves may be the result of another type of supernova remains, called a Grav-Star? It seems almost to physically mimic a neuron star but stopped just shy of becoming a black hole, yet it still has enough of a gravity well to prevent light from escaping. Is...
Hello physics forum. I am not very well versed in physics, so this question could be a misfire, but I just wanted to clear this up.
I watched one of Susskinds holographic principle lectures. So I get that Bob would see Alice turn into a hot mush of energy as she approaches an event horizon...
Yesterday, I attended the following presentation by Prof. Andrea Ghez.
https://www.meetup.com/physicists/events/236886090/?gj=co2&rv=co2
In the Q&A session towards the end, there was a question she fumbled to give a proper answer.
She mentioned that as long as the mass is compressed into...
So, a black hole has infinite gravity that even light can't escape from it,
my question is,
the gravitational field of a black hole can even pull light into it,
then it means it is even faster than light, if not, light can escape from it.
Does this argument make any sense, please tell me! thanks
When somebody crosses the horizon of a black hole, the person would have the privilege to travel backwards in time (as shown in the movie 'Interstellar'). What are the possiblities of such a person to even survive after getting in a black hole, and how does he even able to travel in the past...
If you fall into a black hole, that what is closer to the singularity, will fall faster that than what is further. However, space before and after you, is falling in with you. So from each General Relativistic perspective of "you", because there would be no inertial frame to orient yourself (you...
Homework Statement
The radius Rh of a black hole is the radius of a mathematical sphere, called the event horizon, that is centered on the black hole. Information from events inside the event horizon cannot reach the outside world. According to Einstein's general theory of relativity, Rh =...
Do black holes have an internal space? Consider the diagram. Inside the negative space, a "bubble" of sealed space, matter is free to move.
https://dl.dropboxusercontent.com/u/109630018/temp/phys/blackholein.jpg
Homework Statement
The problem is to calculate the temperature of a one solar mass black hole
Homework Equations
S = \frac{8\pi^2GM^2k}{hc}
E = Mc^2
\frac{1}{T} = \frac{\partial S}{\partial U}
The Attempt at a Solution
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My first solution I pulled out an Mc^2 Which left my...
I'm very new to the understanding of Hawking Radiation. I don't know much about this theory, but I do know that Hawking radiation works on a Quantum scale. I know that with black holes this theory proposes th idea that over time black hole lose mass because of "Spontaneous appearing positive and...
I understand that the coordinate system (CS) for a distant observer Od is different than that for an observer Of who is falling radially toward the event horizon of a non-rotating black hole (BH). Using the Schwarzschild metric, I would like to understand the transformation equations that...
Just a question originating from pure curiosity.
But what would happen if we had a large ring in outer-space, akin to the ring world in the game "Halo", so massive that it's minutes from collapsing into a black hole.
If it were to uniformly gain mass on all parts of its structure, how...
If you square both sides of the gravitational time dilation function for non-rotating spherical bodies, do you not get a "time travel function" that allows you to travel back in time with a massive enough body like a black hole?
I'm just wondering if a spacecraft or any kind of matter was swallowed by a black hole , where does the debris go? I know that it will disintegrate, but even the gravity in there is very strong will there be debris left? If there is, Will it go to other dimension or what?
Thanks,
Austin
Alrighty, this is my second attempt at this thread, as my first was removed due to speculating theories so i will try to keep this short and clear.
Is it possible to apply the concept of Wave/Particle duality to explain the event horizon paradox in which a particle can cross the horizon in a...
In my thought experiment (it seems that others have asked a similar question, but I have a more specific question in my list below), we have a physicist outside the event horizon of a black hole. He has many entangled particles and sends some into the black hole.
Is / Could there be some...
I have always wondered various questions, out of which these 3 below are on the priority list including a previous topic I questioned here ofcourse without any answer to it. I am no science guy by the way, just curious!
So the questions are:
1. Can a black hole contain a wormhole inside of it...
Let's imagine say, a spaceship is going through space at 99% the speed of light. Relativity says (to my understanding) that as the spaceship increases in speed it's mass will increase and it shall also get slightly shorter. Let's assume that energy isn't a problem, should the spaceship continue...
In many vortex's, the center has low pressure, from the center of a stirring cup of tea to the centere of a hurricane or storm system. I'm trying to crudely model how this might apply to the center of a spiral galaxy. If the behavior is similar, and the center has a low pressure void...
What is the most general method of obtaining the event-horizon from the given black hole metric.
Let us consider Kerr black hole in Kerr coordinates given by
ds^2 = -\frac{\Delta-a^2sin^2\theta}{\Sigma}dv^2+2dvdr -\frac{2asin^2\theta(r^2+a^2-\Delta)}{\Sigma}dvd\chi-2asin^2\theta d\chi dr +...
Let's start off with what we know about black holes; It is formed through a colossal explosion of a star. So, I want you and your silly little friends that work in the Physics department to think about this deliberately: The Big Bang tells you that the universe was formed through a explosion...
I know this is far from what a strict obeyance to the principle of occoms razor may result in and its probably wrong. is it theoretically possible that as a star contracts to result in a black hole, the contraction does not stop when its just a point hole, but continues, expanding in a negative...
I have this crazy and goofy dream to construct an artificial black hole. Not a crude analogue, but the actual astronomical object. Would that entail using a particle accelerator to accelerate particles to huge velocities, gaining mass, and then smashing together and then turning into a black...
Hawking said that the horizon area of a black hole never decreases and illustrated that in his Hawking Are Theorem:
dA/dt ≥ 0
Does anyone know why is it like that. Why doesn't the area decrease?
How fast do we expect the hypothetical graviton to travel?
It seems that if the graviton were to mediate the gravitational force then it wouldn't be subject to the normal FTL rules otherwise black holes would have no gravitational effect on the rest of the universe.
What's the current...
Would it be possible for the universe to exist as a white hole within a black hole? I know about the whole black hole universe theory, though I never really looked into it.
Can someone help me on this: Hawking Bernstein radiation can cause a BH to evaporate. The second law of BH dynamics says that the area of the event horizon cannot decrease. Isn't this a contradiction? Also when considering the size of the event horizon, is it different depending on wheather...
Hello everybody, this is my first post to the forum. I am trying to learn concepts in physics at the moment.
According to the theory, the concentrated mass of a black hole warps space-time so much, that not even light can escape the event horizon.
I have a thought experiment. Say, half the...
first, what I know about black hole is;
It has so much mass that collapse into itself create gravity field so strong that even light can't escape.
and normally, black hole born only in giant star explosion.
but
what 'IF' normal rocky planet happen to collect mass (by asteroid, gas or...
Has anyone studied the effects of the central black holes in the galaxy's, on the rotation of the galaxy's spiral arms. When the black hole spins, do the stars in the surrounding galaxy spin in the same direction, does the speed of the spinning black hole affect the rate of rotation in the outer...
Its said there up on the universe, black hole which even can trap the whole light entering through it, exists. But if anyone, I mean any living things, trapped there...I'm confused how can they go beyond the black hole...or will be they trapped, if so what happen their bodies?
Singularity Spin Mechanics
Okay I within the last week too a look at a article about black hole spin and in this article it was said by a scientist that black hole's spin near the speed of light that are supermassive blazars I was thinking if a object is spinning wouldn't that make this...
destroy a Blackhole? !?
http://arxiv.org/abs/1304.6592
What the?
I nominate this for the most outlandish arxiv article I've seen yet lol.
I couldn't think of which forum to post this but its definitely is worth laughing about.
Does the mass of a black hole remain the same if it is not "feeding"?
If matter in a black hole keeps crushing down in size to infinity, does the mass stay the same, but the volume decreases? Isn't a black hole constantly shrinking in size? Thanks in advance for the help!
hi guys, i have an elementary question about the black hole..recently i have read in a science magazine that even the lights from other stars can not reach to the black hole ( event horizon) rather bends in other direction due to its gravitational force..now my question is if i point a light...
Hello,
New to this forum. Very fascinated with physics. Started as a fascination with waveforms, sound, acoustics, and quickly spiraled into an infinite fascination with physics in general, specially particle physics at a quantum level and general relativity at a cosmic level and nuclear...
From a GR perspective, how does the event horizon of a black hole know how to behave?
Consider a simple scenario of a shell of material outside the event horizon of a black hole, in free fall. Once the material is consumed by the black hole, the event horizon will be greater, but my...
Hi,
This is my first post and first of all I would like to thank all the contributors to this forum for the amazing amount of information provided here.
I’m not a physicist, but I like physics (although I have only a qualitative understanding of it) and I like to smash my brain on difficult and...
Thought this article may spark some interest if it works out we may gain a better understand of BH's.
http://www.sciencedaily.com/releases/2013/01/130130132324.htm
Ok I am wondering what would happen if an anti-black hole collided with a black hole of the same mass. Would they annihilate and release energy or would it become a more massive or less massive black hole?