Black holes Definition and 1000 Threads

This is a question inspired by the "Golf Ball" thread, which is no longer open for comments, I guess. For a black hole of constant mass, the metric external to the black hole can be written in Schwarzschild metric, which is characterized by the constant M, and the corresponding radius 2 M...

Greetings everyone! I used to be a huge big bang theory fan, but these days it strikes me as the most eloquent example of scientific conformism. I can fully understand that the only real alternative to it can be nothing else but a Big Nescio Theory, though ignorance can be very creative when one...

I've been reading up on EC theory, and the basic premise and the math behind it are all very straightforward. What I'm a little confused about is more the intuitive side of the theory, and I'm sure it stems from a very poor intuitive understanding of chirality (I do have some intuitive...

As I posted in another thread, I'm giving the caveat that I am no physicist and have only a rudimentary knowledge of math. Anyway, I am currently reading a book called "Three Roads to Quantum Gravity" by Lee Smolin. I came across a section of the book that confused me. Namely, Dr. Smolin...

Wow! Thanks to all for this great resource. Would it be possible to cast light harmlessly by spontaneously creating microscopic black holes of small enough mass? Or would you necessarily get high-frequency X and gamma radiation along with visible light?

In the picture i have included I was wondering if the same downward force (black arrows) applied in the diagrams would result in an increased pressure as the water comes up through the same size hole. I am assuming that both Diagram B and C will result in a higher pressure because of the...

I am interested in how physicists view time, and in any thought experiment (eg. anti-matters time direction, spinning black holes that may have the time dimension no longer orthogonal to the three special directions, delayed quantum eraser experiment that might permit backwards in time...

Start with an existing black hole and an event horizon radius R at time T. Say the black hole is being "fed" an infinite series of golf balls, one after the other, which are all stamped numerically such that the current golf ball external to the event horizon is 1.0 * 10^32. See linked img...

Hi everybody, Around a black hole, a test particle can experience two types precession: of its pericenter and of its angular momentum vector. I would like to know if there exist an EXACT expression for the rate at which these two precession occurs both for a Schwarzschild and a Kerr black hole...

This is the second half of the poll. Of the ten candidates in Part II, please indicate the ones you think will prove most significant for future Loop-and-allied QG research. The poll is multiple choice, and it's possible to vote for several papers. Abstracts follow in the next post. Here's a...

There are twenty candidates, and the poll is divided into Parts I and II, each with ten. The poll is multiple choice so it's possible to vote for several papers. Please indicate the ones you think will prove most significant for future Loop-and-allied QG research. Abstracts follow in the next...

General Relativity predicted existence of Black holes. The theory of general relativity predicts that a sufficiently compact mass will deform spacetime to form a black hole. But The Chandrasekhar limit is the maximum mass of a stable white dwarf star. White dwarfs with masses greater than the...

When the star stops burning because heavier elements like Iron are formed in its core. Then the gas pressure stops and as you know the gas pressure helps keep a star in equilibrium because it provides pressure against the force of gravity. So Iron does not give off energy. So what stops the star...

This seems like a question that would be in the Relativity FAQ, but I didn't see it. Briefly: I've seen the claim made that there is plenty of observational evidence for the existence of black holes. But I don't understand how, from the outside, one can tell the difference between a black hole...

I am sure this question must have been dealt with before but i can not find an answer: What came first galaxies or black holes? How did supper massive black holes become so massive? List of most massive black holes http://en.wikipedia.org/wiki/List_of_most_massive_black_holes

It is said that black holes exist and are therorized to be very very abundant throughout the universe. These black holes are said to be sucking everything up around it, including light. It is also said that the universe is ever expanding, and that expansion is accelerating. How can the universe...

I'm trying to understand the ideas in this paper at a nontechnical level: Laura Mersini-Houghton, "Backreaction of Hawking Radiation on a Gravitationally Collapsing Star I: Black Holes?," http://arxiv.org/abs/1406.1525 She says: This work investigates the backreaction of Hawking radiation on...

Black holes have long captured the public imagination and been the subject of popular culture, from Star Trek to Hollywood. They are the ultimate unknown – the blackest and most dense objects in the universe that do not even let light escape. And as if they weren’t bizarre enough to begin with...

Newtons Universal law of gravity equations are an excellent approximation when dealing with low velocities (i.e., velocities whose magnitude is much smaller than the speed of light) and when dealing with weak gravity fields (such as those found on Earth or around low-mass stars). The...

Here is what I have read: carroll, sean from eternity to here carroll, sean the particle at the end of the universe deutsch, david the fabric of reality gott, j. richard time travel in einstein's universe greene, brian the elegant universe greene, brian the fabric of the cosmos greene...

I've been reading Kip Thorne's "Black Holes and Time Warps," and it mentioned something rather counter-intuitive; apparently, when material forms an accretion disk and falls into a spinning black hole, it increases the angular momentum of it. Now, let's take a gas cloud, and put a spinning...

In How A Supernova Explodes, Scientific American, by Bethe and Brown, there is this passage. Wow 10% of the mass equivalent of the neutron star. What an amazing number. But as I see it, the number of neutrinos should equal the number of protons in the pre collapse core material (which...

The event horizon, or schwarzschild radius for a black hole with the mass of the Earth is 3 km. But according to http://hubblesite.org/reference_desk/faq/all.php.cat=exotic, objects would have to be as close as about 6.2 miles (10 km) to the black hole's center before they began spiraling in...

The way I understand Hawking radiation is that black holes decay by sucking in anti particles from the virtual particle pairs that are created right at its event horizon. I also understand that these anti particles reduce the mass of the black hole instantly when crossing the event horizon? And...

I have fundamental question about what is called the “law of conservation of energy”. We all hear about the tidal power stations which using the tidal power. The source of the tidal power came from the changes in the gravity field between the moon and the earth. Allegedly, because of the law of...

Dear all, In one of his lectures,Prof. Susskind mentioned that the event horizon "bulges" forward to meet any incoming radiation or matter; and it is a property of Einstein field equations. I have not come across any such property, and if it exists, shouldn't it belong to the Schwarzschild(or...

Hi Is someone interested in this topic ? I'd like to share my idea with you, PF people. I also designed a "reverse geometry" to illustrate this paradoxical effect. Thank you for your answer Jean-Marc

Recently I have been researching black holes, and came across the "Schwarzschild Radius". The wikipedia page on Schwarzschild radius's mentioned that the Sun has a radius of 3km. If that is so, then how can that be so, as that would mean that light cannot escape it. So when it said "3km", did...

Does quantum bounce provide a solution by which black holes could on some other side of the universe or in another universe create white holes Sent from my iPhone using Physics Forums Jim P

With this post I am hoping someone would be kind enough to lead me in the right direction. I am a layman who knows little about the actual math behind physics, nonetheless I have developed an interest in it and wish to expand my knowledge base. First question I have is if someone could...

Hello. I would like to know. Does matter when heading towards a black hole then crossing the event horizon threshold reach the speed of light? I am guessing no. It simply crosses the threshold and at a finite velocity heads toward the center of the black hole. The escape velocity of a...

Ok, so if I were to travel towards a black hole at close to c, would the event horizon become visible? Let us assume there are no stars, CMB, or any other luminous body in the universe.

Could Gravitons be causing this Black Hole turbulence? http://perimeterinstitute.ca/news/turbulent-black-holes In the article above they talk about how the Gravity around Black holes is bumpy or has Gravity turbulence. Does this discovery give any evidence to the undiscovered Graviton? Because...

Is the amount of Dark Matter in a Galaxy equal the amount of Matter consumed by all the Black Holes in that Galaxy?

It is my understanding that at the most fundamental level, a black hole is simply an object with a gravitational field so strong that there exists a sphere that lies outside the body of mass of that object from which the escape velocity is equal to the speed of light. In other words, a body of...

Is it still true that most if not all galaxies have at their center a Black Hole? And that the estimated gravity is about 10% of the total mass galaxies. And is it still true that all stars or 99 % of them are moving out and a way from the black hole. I was just wondering if these black holes...

dear sir i want to know theoritically what would happen when three black holes are near by and exert influence on each other.

by Dr. Ken Croswell Astronomers staring across the universe have spotted a startling scene: three supermassive black holes orbiting close to one another, two of them just a few hundred light-years apart. The trio, housed in a pair of colliding galaxies, may help scientists hunting for ripples...

So according to Stephen Hawking, non-penetrable event horizons don't really exist. So by the same argument the cosmic event horizon can't exist either right? Only an "apparent" horizon which may hold information from outside the visible Universe for a short while until it enters the visible...

Black hole A moves at slow velocity, and there's an Einstein light clock hovering near the event horizon. Black hole B moves at high velocity, and there's an Einstein light clock hovering near the event horizon. The black holes are identical. And the light clocks are at the same...

For my research on astrophysics for the summer, a professor gave me this assignment but I don't know where to start. The question is: What methods could be used to find the dark matter distribution around a galaxy's central black hole?

Not sure how speculative this is but thought it would be of interest- http://www.iflscience.com/space/could-supermassive-black-holes-center-galaxies-be-wormholes and the related paper- http://arxiv.org/abs/1405.1883v1 Distinguishing black holes and wormholes with orbiting hot spots by...

Bear with me, I am (not even) a chemist. This is something that bothers me for some time. The larger the black hole, the smaller the density and the smaller the tidal forces. Supermassive black holes (expected to exist in centers of galaxies) have density comparable to that of water, and I...

I am no cosmologist, just purely curious as to what the explanations and if there are explanations currently to some of my questions: If it was possible can one fly far enough around a black hole in all 360 degree angles, i assume yes one could but what the question leads to is, does it have...

If I observe two particles that are entangled enter two different black holes and wait, will there eventually be 2 entangled photons radiating out of the black holes or do the black holes take possession of the entanglement as the 2 particles enter their respective black holes and said black...

Hawking Radiation and the "Decay" of Black Holes I have been doing a lot of reading and thinking about certain quantum mechanics so that I can try and wrap my head around how it all works. However I have come upon something that I cannot find a good explanation for. I was reading about...

So, yeah. Here I am, a fledgling Undergraduate Freshman at Brigham Young University. I've been reading Brian Greene's books, and darn, do I love physics. This was the semester I decided to change my major from Mechanical Engineering to Physics-Astronomy. Well, one night, as some of this...

Has it ever been explored in science that the other side of a black hole could have caused the "Big Bang"? My thinking is that if a black hole sucks in matter and compresses this matter to a point where it can no longer contain it; would that not cause a collapse on the other end? It has been...

Hi friends, I was wondering about the following - in GR texts we always see these penrose diagrams and some line representing the horizon and all these timelike , spacelike curves and all that ... but the picture that I have of GR is just that of a smooth 4 manifold endowed with a metric . Can...

As the title says, do we have to have black holes for the universe to run? Every galaxy has a suppermasive black hole at its center. What if there were a star at the center of our galaxy? I guess it would have to be so big but that means the star would soon run out of energy and then explode...