Black hole Definition and 999 Threads

can a black hole be connected with the making of a time machine ?

Has there been any evidence of black holes converging? What would we expect to see , if anything?

I'm only a freshman in college, but I am always thinking about the future. I plan to earn my Bachelor's in Physics or Astrophysics, and then continue onto graduate school. I'm at Penn State University, so I plan to stay here for all of my degrees unless a better, more valuable opportunity...

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...

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...

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...

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 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...

Why the gravity around a black hole remains normal unless you get extremely close? But first: How far from Earth is there zero gravity? Gravity declines as a function of the square of the distance from a mass. Earth's gravity is less and less as one goes further away, but is never zero. A...

Hello Everyone, This is my first post, I hope I've picked the right forum for this question. Could a black hole be "pumping" space/time/matter back into the quantum foam? I guess this is asking could it compress whatever falls into it down past Plancks constant?

i was bored and my mind wandered. a question popped up and it got me interested in what others thought who are more informed than me: since black hole is a theoretical construct (and hence can be geometrically perfect), what happens at the exact center of it. with uniform (assumed) density...

[Reposted from my PF Blog.] I haven't yet had the pleasure of participating in a PF thread on this topic :wink:, although I have made at least one post that refers to it in passing. But I know there have been some in the past, such as this, so I wanted to post a quick treatment of the topic...

Black holes are usually shown as funnels. Is there one "funnel" pointing in a single direction or are there event horizons and "funnels" seen from every direction?

Hey! I'm new here and I just wanted to ask a question and maybe I'll come back here once I have started college in a week or so. :P But firstly I must say, at first I thought the confirmation question for signing up was a science question about acid and I was totally stumped. But that's PH... I...

An interesting article for ordinary people but I just wondered if it is science or pseudo science? It offers an explanation why the Universe has a beginning and has finite age. To me it suggests many Universes occurring at random, like raindrops falling randomly into an ocean of space time...

Thinking about how so much matter can be squeezed into a singularity, the answer (if I understand correctly) is that the matter just stacks upon itself down an infinitely long weird space-time well. In a sense, the last item in masks the ones below. But doesn't this impact the gravitational...

Experiment: Imagine the dalayed time quantum eraser experiment, except the pair of "idler" photons(which would normally pass onto the detectors d1,d2,d3,d4) instead fall into a black hole. Would d0 detect interference or not? It seems commonly accepted that the information of...

Are there any EXACT solutions similar to Schwarzschild or Kerr in a spacetime which is not asymptotically flat; e.g. FLRW or other cosmological metrics? I am already familiar with the "Swiss cheese" approximations.

Hello. I'm a layperson curious about physics. I've read that Quantum Gravity could eliminate the predicted singularity inside a black hole based on General Relativity. If that's true, what would happen from the frame of reference at the center of a black hole? Would that cause a tremendous...

Consider two black holes: the left one has a mass M1= 5x10^30 kg, and the right one has a mass of M2= 9x10^30 kg, and they are a distance d= 3.0x10^6 m apart. A spaceship passing between them is having engine trouble and so the captain has to park the ship somewhere where he won't get sucked...

Please excuse me for being a complete and utter pleb, my meager knowledge of Leonard Susskind's holographic principle comes from the second episode of the documentary "Through the Wormhole" [SIZE="2"](which is available online but I won't link to in case it is copyright infringement?). He...

Let's imagine a stationary black hole and a fast moving object falling into BH. Let the momentum of the falling object be enough to give an observable bump to BH, pushing it into motion. Since the object does fall into BH, by momentum preservation BH should start moving. But I don't see how...

What are the equations that shows that time slows down as you near a black hole? I'm trying to prove to a non-believer that the math is there and shows this. Thanks!

http://arxiv.org/abs/1407.0989 White hole anyone?..^^ "...intense gravity creates a horizon, but it is not an event horizon. It is locally like an horizon, but not globally. So, matter is trapped for a while, but not forever; it is called sometimes a “trapping” horizon."-CR

dear sir, i am curious to know whether black hole can be broken apart by some means?

Instead of being a force that works against gravity. Is it possible that dark energy is the pulling of everything towards the event horizon of a black hole? This would marry dark energy with gravity and replace myserious massive amount of energy with a logical source of energy/force that we know...

So as I understand it, Hawking theorized that due to the behaviour of virtual particles on the event horizon of a black hole, eventually the black hole would "evaporate" through what was coined the Hawking Radiation. But what I'm curious about is Hawking's interpretation of the event in that...

By theoretical calculations of super dense black holes show their gravity exceeding to a limit that can pull in light into the heavenly body. This means that the gravitational pull, which are actually acceleration as shown by the Relativity theory, is greater than the speed of light. So won't a...

Hi! New here. Be gentle. Kinda an idea that popped into my head a little while ago: Are the tidal forces of some black holes powerful enough to separate quark groups? Google seems to be a bit iffy on the subject.

It is confirmed that Black Holes have variations of masses. But these masses are said to be gained from the base mass from the Supernova it's born from. Another way a Black hole gained mass was that the collisions of multiple Black Holes caused it to add on to the mass of each other, such as...

Was thinking about this why is it a requirement that the center of a black hole be a singularity? If the event horizon contained all the mass of a black hole would it still not have the same effect on it's surroundings? Why could it not be similar to a a crystal where as each molecular link or...