Black holes Definition and 1000 Threads

Hello, I was wondering a thing or two about black holes, now I'm not any kind of physicist or hobby astronomer for that. But can a black hole consume infinite amounts of, let's say gamma rays without increasing in mass or any other effect? However gamma rays haven no mass since they are pure...

So I've got a question that I can't seem to figure out. If the accretion efficiency of a black hole is L=εM(dot)c2 with ε=0.1 I have to set this to the Eddington luminosity which is Ledd = 4πcGMmp/σT to find the maximum rate at which a black hole can accrete by. I found that κ=mp/σT so I...

When the sun is beginning to collapse will it get smaller and denser?

I was watching Neil deGrasse Tyson video, in which he describes a scenario of colliding black holes. He mentions that when two black holes collide, there is a huge distortion of the space time between those two black holes as each of their even horizons intersect (i.e. each black hole has passed...

The title says it all. Do static black holes really exist, or do the ones we know about seem to be spinning? ISTM unlikely that there could be any non-rotating black holes, but I don't really know, hence the question. Do we have the means to determine with any certainty what the answer is?

Why are black holes black even though light(photons) has no mass? Gravity shouldn't affect it.

How can two Black holes fusion and consist a supermassive Black Hole ?!

Any comments on the following description from Kip Thorne, BLACK HOLES AND TIME WARPS, 1994, Box 10.1 would be appreciated. It seems odd to me that at some given curvature, gravity would become self sustaining...if that is what he is saying. We have previously discussed in these forums that...

Hi, I'm at high school at the moment and i have gotten really interested in black holes and the way they work as i have been reading books from Stephen Hawking. So we know that black holes absorb matter and photons by the pull of gravity. And we also know that it emmits radiation. But because...

1st post here - new to the forums - sorry if this is a stupid question.I was thinking, if the universe is approximately 98% hydrogen, you would think the matter a black hole consumes would be mostly hydrogen. So you have a black hole, it's consuming a ton of hydrogen, squeezing and condensing...

if black hole crash they unite to one b.h here, how can this two crash?? universe has a lot of dimension so i think it is hard to and when they crash, crash with only singularity??

Is the center of a black hole essentially a pole, or a "point at infinity"? I always thought about this in my complex analysis class because one variable complex functions are 4 dimensional, which could translate into space-time. Black holes have to have infinite density in their center, too...

I have a question about the paper: C. G. . Callan, R. C. Myers and M. J. Perry, “Black Holes In String Theory,” Nucl. Phys. B 311, 673 (1989). I have attached the relevant section. I am having trouble using equations (2.1) and (2.4) to derive (2.5) and (2.6). When I do the calculation...

Any decent papers/articles on black holes, their formation, dynamics, etc? Moderate amount of maths and derivations involved would be great!

1) First we shall define to exist, relative to an observer, to mean that "the object in question lies in the observer's past light cone" 2) We define a black hole to be an "area of sufficiently compressed mass such that an event horizon of non-zero radius exists" 3) Next we make the...

How can we know anything about black holes if nothing, not even information can escape the event horizon? If we can know the mass and gravity of a black hole it is because some information is being sent by the black hole, but how can this be possible if nothing, not even light, can escape...

So I found this article(albeit rather dated) questioning they physical existence of Black Holes and what really struck me were some of the comments by physicists Jose M Pecina-Cruz who may or may not be on physicsforums but nevertheless, this is what he had to say about it: So there is also a...

1. Three ships approach a 'black hole'. One ship continuously accelerates at a constant rate to keep itself stationary relative to the 'black hole'. One ship cuts off its engines and free-falls. The last ship accelerates away from the hovering ship and steadily increases its acceleration at an...

What percentage of stars become black holes? I tried to find this information through Google searching and the only thing I could find was a statement that said less that 1 in 1,000 stars in our Milky Way galaxy have enough mAss to become a black hole.

Hi, As I understand virtual particle pairs can be created outside of the event horizon of a black hole. I understand that they result from Vacuum Fluctuations. What creates these vacuum fluctuations? ***A side note: I hope I'm not violating any rules of the physics forums by creating two...

This paper, Constraints on primordial black holes as dark matter candidates from capture by neutron stars - http://arxiv.org/abs/1301.4984, appears to just about seal the coffin on primordial black holes as dark matter candidates. It does an admirable job summarizing the mass constraints on...

Hey all! Two things came to my mind about black holes, and I hope some of you can help me out :) 1. Say you have a non rotating, chargeless black hole of a certain size. Its radius will be R. If you go through the black hole, from your perspective then time will be fine, right? Then that...

Hello dbmorpher here, I am an avid Halo fan, and in the lore the ability to go faster than light is from the http://halo.wikia.com/wiki/Shaw-Fujikawa_Translight_Engine I wanted to know if miniature black holes and hawking radiation would be able to rip a hole in space-time. If not what are...

Why is it that the smaller a black hole is, the more Hawking radiation it emits? It seems counterintuitive to me. I would think that a larger black hole with a larger surface area would trap more antiparticles from virtual particle antiparticle pairs, hence emitting more Hawking radiation.

If a black hole is a stellar structure that has collapsed on itself to a singularity does that mean it has no size? But is so defined by its mass and schwarzschild radius? Cheers

Some astronomers detected flashes of x-ray in the cosmos. They say it can only be possible because matters temperature increases to million degrees to radiate into x-rays, and only objects entering into black hole could radiate x-rays in whole cosmos. How can you detected x-ray radiation from...

Hello, I want to understand how black holes are formed. I don't have any idea of basic astronomy. Can anybody please guide me to a resource centre which gives the basic idea of astronomy. Thanks and regards, -- Shounak

Hello everybody, I was watching a documentary about black holes the other day and I noticed something odd. General Relativity is said to break down when you apply the mathematics on a singularity. In this case, the center of the black hole. The radius of a singularity would be 0. Now there...

Black holes can pull photons in although they move at the speed of light. So, does this means that black holes pull space-time in faster than light and if so, why can space-time "travel" faster than light?

A lot of scientific literature states that black holes 'grow' in size (which I think is equivalent to saying 'grow their Schwarzschild radius or event horizon'). They apparently do so by consuming external matter that falls into them. However, any matter that does fall toward a black hole...

Just a quick question, that I'm not completely clear about; Quantum tunnelling allows particles to overcome barriers that they classically shouldn't be able to overcome, my question is simply, do/can particles escape a black hole after passing the event horizon due to tunnelling? If not, why...

how can black holes bend time if time bending is impossible ?

So are all black holes infinitely small, which is what they call the singularity point? I'm talking about the actual distance the matter of a black hole takes up. Does a super massive black hole have the same physical size as any other black hole(which i guess would be infinitely small) and just...

. http://en.wikipedia.org/wiki/Black_hole and we know that when object travels near the speed of light it gains infinite mass, so does it means that it becomes a black hole?

I wad thinking since black holes are so dense ... lights speed would get slow significantly , so isn't it that if you are at light speed ( 3 x 10^8 m/s ) then you might come out of a black hole ? Its the same concept we learn in 10 grade ! Am i right ?

Hi, my first post here! Galaxies outside the observable universe (that we can't see their light) can affect us with their gravity? If the answer is no, we can say that gravity information travels at the speed of light. So, in a black hole how gravity information from an object inside...

Hi, I am interested in the issue of frame dragging used in a number of galactic rotation models. However, I wanted to first make sure that I have a better understanding the relativistic implications of frame dragging. While the issue of galactic rotation is not the subject of this thread, it is...

I had an exchange with Lubos Motl about this topic, in the comments here. Very briefly, there is a 2004 paper in which the author (Kjell Rosquist) considers the old idea that the electron is actually a spinning, charged (i.e. Kerr-Newman) micro black hole. Using a purely classical model for...

A quick novice question. What sort of shape would project a holographic reality (Kind of like water spraying from the inside walls of a sphere) from the boundaries of the universe and at the same time contain drains (black holes) that feed the shower?

Is there a temperature that black holes cease to emit non-zero mass particles.

so, when it comes to EM or strong force or weak force, you cannot tell the difference it some object exists inside a black hole or if it does not. nothing from that object gets out from behind the event horizon. except for gravity. if a black hole swallows up a massive star, the gravitational...

Theoretically; As any mass approaching the core of a black hole, then would the tidal force difference effect the quantum level and rip apart matter? Also at the very centre of a black hole would gravity cease to exert its force since in any direction the "pull" would be equal?

First, a question. I assume that a photon can be captured into a stable orbit around a black hole. It seems it would just be a function of the radius of the event horizon and the velocity of the photon (always c I know but the vector is the important part). Where would this stable orbit be in...

A comparison of a large star and a black hole: Both have identical masses. Correct me if I'm wrong but gravitationally, they would be the same because we assume that the gravitational force acts from the center of mass. So here's the question: If both the black hole and the star have the...

Scientists say that in mathematical terms in singularity all the math breaks down and you get infinity. But how come this be if the black hole formed from a star that had huge but still limited amount of matter/fuel in it, and that limited amount just got highly compressed. And if there even is...

According to General Relativity, do gravitational waves penetrate black holes? My gut feeling says "no, if gravitational wave goes under event horizon, it won't re-emerge", but I'm not an expert...

I recently saw a video where it was stated that black holes may have an inner 2nd event horizon where beyond it is trapped light and energy! I have searched the web for an explanation pertinent to this hypothesis but found nothing. Can anyone shed some light (if possible)?

Plain old Newtonian mechanics is time-reversal invariant, i.e. if you view a recording of some events played backwards, it would still appear to be following the same physical laws (gravity attraction law in particular). This type of "time reversal" is exactly equivalent to just turning every...

from a layperson's perspective - if a supermassive black hole is more massive than a million suns then why is it cold? An answer in plain english is truly appreciated for the layperson like me.

A stellar mass black hole is around 10 solar masses, and some stars can be much massive than this. And doesn't a black hole have more gravity than anything in the universe? Does more mass necessarily mean more gravity? If a star is more massive, how can a black hole siphon off material from it...