Black hole Definition and 999 Threads

How Can we Find the Escape velocity of a black hole.

Hello, Theoretically any object can convert into black hole by compressing its mass below some radius( describe by Schwarzschild Radius). Suppose one of this object after becoming black hole have radius which is comparable to atoms and nucleus radius. Now my question is what will happen if we...

Is it possible, in principle, for an experiment to distinguish between an ensemble of pure states and an ensemble of mixed states? If so, how? In particular, I am thinking of an ensemble of particles whose spin has been measured, one at a time, on the "Vertical" axis. The ensemble consists of...

Consider a Maximal (negatively) charged black hole. Can it have "flavor" or weak charge? Suppose a muon collided with that hole. Would an electron be emitted? What if electron neutrinos collided with that black hole; would electron neutrinos more likely be emitted as Hawking Radiation...

if I compress a heavy body to a very small point object such that its density is almost infinity, I get a black hole. but how can a point mass be a hole? why do scientists call it a black 'hole'? what I mean is, if I were to be pushed into a black hole, will I collide with that point mass? Also...

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...

Well read a post long ago about light My questions are: If light has no mass then how can it be suck in a black hole? What exactly is redshifting? What do polarizing glasses do?

Suppose you have a source of electron antineutrinos, and you arrange your apparatus so that a billion billion billion of them collide directly with a black hole. In principle, you could measure the change in momentum and energy from that occurrence. Suppose you did that the next day. According...

So I understand that as a star begins to die, and begins fusion of H, He, C, O... it eventually reaches Fe which cannot be fused to create energy. Then the stars own gravity overcomes it's outward radiation and the star implodes, and eventually a black hole is created. How can the star's...

Hey Guys, so i was reading Hawking&Ellis a bit and still encounter always problems with the Penrose-Diagrams. Looking at the Penrose-Diagram for the rotating Kerr-Black hole (just one illustrating picture at the end) i come up the following question: Why are there TWO regions III and III ? In...

I'm a bit puzzled by the dynamics of things falling into a black hole. If I start with a test mass at infinity, it will fall freely into the black hole and reach the speed of light at the event horizon. What happens if I throw something towards the black hole? Will it already reach the speed of...

I have been pondering black holes for some time and have had trouble with the problems presented simply because there is very little we can do to study the phenomena. I have always thought of a black from the outside looking in, or basically the only way we can hope to see a black hole. However...

I have a problem with the concept of a singularity, defined as something that has a property which is infinite. Infinities do not belong in our reality, and in my opinion are just hints that our understanding of the phenomenon is incomplete or wrong. From my understanding, during the collapse...

In the view of Hawking radiation and entropy of black holes, the evaporation is continuous and at one point, there will be no singularity for the black hole. By relativity, if we reach a super massive black hole, then time would be relatively slowed down to a point that it stops (maybe?). Now...

I'm going through Kerr metric, and following the 'Relativist's toolkit' derivation of the surface gravity, I've come to a part that I don't understand. Firstly, the metric is given by...

Information that is ordered can be compacted down to a single repeating unit i,e; 110055110055110055110055 down to just 110055 and this meant that it must have been highly ordered to be compacted down this far. So could it be that matter is also highly ordered somehow and it can be compacted...

Hey guys First real thread besides my introductory thread. I'm a Danish student in what is somewhat equivalent to my junior/senior year in the american school system. That was a small attempt at school system conversion. I'm writing a project about the black hole Sgr. A* in the centre of our...

We have a large mass, and we increase it slowly- dropping in one atom at a time. Will a black hole form suddenly, or will it gradually become blacker with the addition if each atom? I assume that a mass marginally below the threshold must at least partially have the properties of a black hole...

Hey all this is my first post, Everyone knows you can't enter a black hole because you'll be stretched/turned into noodles due to the immense change in gravity over small lengths. I was reading another thread on the physics forum and happened to come across an equation which would determine if...

I see that the formula for hawking radiation is related the the formula for unruh radiation. The accelleration experienced by a body yields an unruh temperature equivalent to a black holes hawking temperature with an equivalent value of g. The unruh effect happens at all accelerations, therefore...

If a large mass of matter and anti-matter collided to form a black hole, I assume they would anihilate and you would have a black hole made of photons. Now considering the black hole as a container of photon, there must be a net pressure pushing against the confines of the gravity. The force of...

A substance of arbitrarily low density can form a black hole if there is enough of it. So I took the mean density of the universe and calculated how big it would have to be to form a black hole. It's a surprising coincidence that the swartzchild radius in light years is the exact age of the...

##E= -T^uP_u ##, where ##T^u## is the time-like killing vector associated with the Kerr Metric and ##P_u## is the 4-momentum of the particle. ##E## is the energy. Outside the ergosphere ##T^u## is time-like and inside the ergosphere it is space-like. Therefore it can be arranged within the...

I know the original schwarzschild formula for finding the radius of the black hole, but what equation can be used to find its mass if you ONLY know its radius?

I have a question about equation 10.21 in "Exact Space-times in Einstein's General Relativity" by Griffiths and Podolski. The equation is the well know standard metric for multiple extreme Reissner Nordstrom black holes. It has the below term: (1+ sigma(mi/ri)) The point ri = 0 is of course...

I just saw The Theory of Everything, which is a Hollywood biopic about Stephen Hawking. Of course the physics content had to be watered down and made to serve dramatic and thematic purposes, but a couple of historical points seemed interesting and made me wonder whether they were real: 1...

As all of us know that in a vacuum the particle antiparticle pairs or the virtual particles are created violating the law of conservation of energy. So even near an Event Horizon of a Black Hole virtual particles are formed. One of the particles gets sucked into the black hole but the other...

I've been searching over this and I don't quite get it yet. I just heard about this "z" parameter for gravitational red shifting and I thought it'd be fun to apply into the scenario of a solar-mass black hole. The equation I looked at was (1/(2GM/c^2r)^0.5) - 1 = z So, like, does the z parameter...

After reading: I wondered about the following thing - is it possible to make a story in which there is a place for a habitable planet and a black hole? (I mean, I have one idea, but it does not end up well... ;) ) I see one additional limitation: the black hole was created in a supernova, so...

Could a photon utilize quantum tunneling to escape the threshold of a black hole or the confines of the curvature of space-time? Could any particle for that matter?

Can be black hole created straight from cloud forming protostar. I mean, the region which is collapsing is so massive that pressure of radiation could not resist and the cloud is collapsing to singularity? If not, why?

Inspired by the movie Interstellar which featured a planet orbiting a rotating supermassive black hole with an extremely high time dilation factor (slowed by a factor of 60,000 relative to observers far from the black hole), I was wondering if anyone knows of an equation for time dilation of...

I found a new book on The Science of Interstellar by Kip Thorne https://www.amazon.com/dp/0393351378/?tag=pfamazon01-20 What caught my attention was a photo of John Wheeler at the black board teaching about black holes. You could see the incredible detail in each pane of the board almost like...

Hi i have a few questions about black holes. Are black holes just stars that are so big, and have so much mass that no light can escape them? Do black grow in size, or are they just an infinite small point of space?¨ Can black holes die? are they actual holes, or are they spherical? can you...

Now I know that in the general Schwarzschild metric, there is energy and angular momentum conservation, but what I'm wondering is if there is any linear momentum conservation. Let's say a particle collides with a black hole. Does the energy of that particle go solely to the rest mass and...

A number of recent threads have discussed what happens when an observer falling into a massive black hole passes the event horizon. What I would like to know is this. For a massive BH of mass M, Schwartzchild Radius Rs, how long would it take for such an observer (who, presumably crosses the...

Can an observer, freely falling into a black hole observe another black hole, falling with him, after crossing horizon? I assume one should be, as for freely falling observer nothing special happens, when he crosses horizon. But just wanted to double-check.

Is it possible for our solar system to be located inside a black hole which is our galactic centre?

What is the origin of the M-sigma relation between supermassive black hole mass and galaxy velocity dispersion?] How did the most distant quasars grow their supermassive black holes up to 109 solar masses so early in the history of the Universe?

I recently read a few articles that contradict Einstein's Singularity theorem. The idea being that black holes are wormholes to other universes; with a white hole on the other side of the black hole (Poplawski's theory). What if instead of being a portal to another universe, the Event Horizon of...

Hi all I gather a normal black hole has maximum angular velocity at the point that the event horizon is moving at The speed of light. However what would be the maximum rotational velocity for a maximally charged black hole- for example one made purely of electrons? Thanks

Yesterday I had a bizarre idea. I supposed that a black hole (which I assumed to be a sufficiently dense sphere) became our sun. I know this is completely wrong, but please humor me and see what I've done. Suppose we have a sphere sufficiently dense, so that the Schwarzschild radius, r_s, is...

on this lab worksheet i need to fill out the bottom table (the top one is already filled out). I am having trouble understanding The numbers in the first part of the chart. I know RA is right accession and DEC is declination but what I'm not understanding is why there are two different numbers...

Is this established or is it dependent on the size of the black hole? http://www.space.com/22180-neutron-stars.html Neutron stars pack their mass inside a 20-kilometer (12.4 miles) diameter. They are so dense that a single teaspoon would weigh a billion tons — assuming you somehow managed to...

I know that the schwarzschild radius is proportional to the mass. But in case of black holes the mass remains the same only the size and density changes. So does the schwarzschild radius stay same when it is the sun and when it becomes a black hole?

arXiv:1410.3881 (cross-list from gr-qc) [pdf, ps, other] Universe in a black hole with spin and torsion Nikodem J. Poplawski Comments: 10 pages Subjects: General Relativity and Quantum Cosmology (gr-qc); Cosmology and Nongalactic Astrophysics (astro-ph.CO); High Energy Physics - Theory (hep-th)...

The brains at the Perimeter Institute recently published a paper describing how our 3 dimensional universe could possibly exist as the event horizon of a 4 dimensional black hole in a 4 dimensional universe as the event horizons of black holes have one less dimension than the black hole itself...

Have theories been formed yet on how to stop a black hole?

If I were to travel towards a BH at, once again, close to c -- would I, in my frame of reference, prevent (observationally at least) the formation of a BH? In other words, can I match my speed with that of the collapsing object's light or even infalling matter (in an already formed BH) from...

Why we talk and discuss about effects on light cones by black holes though we know there is no light left after a star dies and become a black hole? there should be no light and so no light cones...