Black holes Definition and 1000 Threads

http://arxiv.org/abs/1007.1317 Black holes in an asymptotically safe gravity theory with higher derivatives Yi-Fu Cai, Damien A. Easson 22 pages, 3 figures (Submitted on 8 Jul 2010) "We present a class of spherically symmetric vacuum solutions to an asymptotically safe theory of gravity...

Do we have empirical evidence proving that black holes, rather than stars with density close to black holes, exist in our universe? To put it more clearly, are astronomers able to distinguish a black hole from a compact object with a surface gravitational redshift of, say, z=100? Of course, if...

From what I understand, black holes can generate gravity-waves in orbit with each other. But can they absorb them? Since gravity waves travel at the speed of light, I would think that they would not be able to escape BH gravitation. But since they are so massive and powerful, I wonder if they...

This may be a dumb ? , but what would happen if two black holes were coming together and when they were coming together we got a photon extremely close to their event horizons , and when the came together the photon was right on the overlap of their event horizons which way would the photon...

I'm currently writing a sci-fi/fantasy novel and although I know everything in this genre doesn't have to be technically accurate I still like to keep one foot firmly in the realm of reality and combine it with aspects of the fantastic. At the moment I'm working on a plotline that involves a...

Okay, this is me beating a dead horse, but i have a rather simple question. Is the time dilation effect described in reference to a black hole literal or figurative? for example, a man falling toward a black hole will appear to slow as he approaches the EH. This effect obviously increases...

hi i want to ask aquestion what is the biggest qatar: black hole or white dwarf or nutron star or the sun please i want to know the biggest one and then and then and the smallest one thaaaank you very much

I was wondering if someone agrees: Is it possible that on the other side of the black hole is an expanding universe? It seems an iteresting idea to me: in our universe a star collapses onto itself with an explosion, creating a black hole and on the other side a big bang happens with matter...

Are black holes a point of singularity of infinite density, approaching that point as a limit, or just really massive and really dense? Is light really being "sucked in" by the gravity and actually being attracted to the object, or is it really just following the really really steep bend in...

I am a little confused over something, so perhaps someone can tell me which one of the following statements is incorrect. (I don't know a lot about this, so forgive my ignorance). Suppose that we have a closed system of some size, and we start in a state where we have a black hole at the...

Dave Mattingly has been a frequent collaborator with Ted Jacobson (his thesis advisor). You know of Jacobson if, for example, you followed the recent discussion of "gravity as entropic force" by Erik Verlinde and others. In 1995 Jacobson derived the Einstein field equation from thermodynamics...

I read in "Simply Einstein; Relativity Demystified" that if someone were to obeserve an object falling into a black hole, they would never actually see it reach the black hole. Is this true? If so, then let's say for argument sake, we made this object an Encyclopedia and we "the universe"...

I thought this may be an isolated idea but on doing a search on the web, there seems to be a common interest in the idea that centrifugal force reverses near a black hole. Below are a couple of links- http://www.npl.washington.edu/av/altvw55.html"...

Given why black holes are what they are, it is difficult to fathom that the constant influx of matter and energy into its core would somehow eventually cause it to dissipate and disappear. Would not the addition of matter and energy simply contribute more and more to the gravity? It would seem...

I'm new to the Physics forum and thought I'd start with a couple of stupid questions. 1) How do we know that black holes are not stellar nuclei that have just collapsed to a volume less than their mass dependent Schwarzschild radius (the radius at which the speed of light is the escape...

Hm, I wonder since neutrino's have no electric charge or color charge, but do have mass, is it possible for two neutrinos to come so close together that they collapse on themselves? Although the gravitational field between just two neutrinos is extremely small, it should still be possible right...

light interferometry as described in Thorne's "black holes and time warps"? hello, maybe someone who read the book can help me with this, but i'll give all the information so that even someone who hasn't read it can understand. At page 383 and following, and at fig. 10.6 and box 10.3, Thorne...

If black holes are not real, just wondering? By the way they may or may not exist. But since some people don't believe they exist and some do, then if you DO NOT , how do you explain what happens to neutron stars that are 20 -25 the size of the sun? typo in the title, it should read: " what...

From my understanding electrons are point particles with zero volume, therefore zero radius. F = GMm / r^2 F = GMm / (0)^2 F = ∞ N. Can someone please explain?

You have two black holes of the same mass and charge widely separated in space. One was formed from matter and one from antimatter. Are there any experiments which could be conducted outside the horizons which would distinguish the two? Skippy PS Sorry if this is the wrong forum...

Are there any theories that suggest that there are smaller degenerate states than the state reached in a neutron star? For example, is there a degenerate state for quarks? For strings? (should they exist) For theories that suggest such possibilities, do they discuss what would happen to the...

Is there agreement here or are all/most of the neutrons in the same state?

While watching the Discover Channel, they mentioned a jet of gas emitting from a black hole . . . . yet they say they are so powerful that not even light can escape them. So if not even light can escape the gravity, how would "jets of gas"? As a side note, . . . I realize that most of...

Sorry if someone already asked these, but I didn't see anything that was the same. A few of my friends are in a film class and we're working on a little indie movie, and the concept of it is a micro black hole is discovered at the edges of our solar system, and we want to make it somewhat...

I have a question that's been bothering me for a couple of days, and none of my professors have been able to answer it. Two observers, Alice and Bob, are initially at rest relative to each other. Bob begins a constant acceleration. I want to be specific; let's say his acceleration is g and...

Gravitons are considered to be the mediating particles of gravitational force just as photons are considered to be the mediating particles of electromagnetic force. Both have zero rest mass. If extreme gravity of black holes does not allow photons of light to escape, why does it not do the same...

So... my first post, and bear in mind, all I know of Black Holes is what I've read of Black Hole and Penrose Effect articles on Wikipedia. (don't hate me) Would it be possible to use Black holes' Ergosphere for FTL travel? And this is all on the "if" that we, or some other race, achieved...

If Dark Matter is made of particles, then wouldn't it be possible to have clumps of it collapse into a black hole? Would there be any radiation from that collapse that we could see? Would that radiation be distinct from the formation of normal black holes? Shouldn't we be able to measure the...

I am believing that event horizons refer to where light can no longer escape the gravity of a black hole. What about everything else that moves at less than the speed of light? If a small moon winked into existence at some point further out than the event horizon with momentum that was sending...

Unlike other people, I find black holes puzzling. Let's consider some black holes of modest size, say a few solar masses: Suppose we have a smallish black hole rotating significantly (read: spinning like its angular momentum represents a large fraction of the energy equivalent of its rest mass...

How are black holes linked to worm holes, or are they the same thing, for example can you use any of them to transport through space, and if you can, would it go to a different location of the universe your in, or can it go to another universe as in another dimension?

Some black holes may actually be "Quark Stars" http://www.usatoday.com/tech/science/space/2009-12-07-quarkstar07_ST_N.htm?utm_source=feedburner&utm_medium=feed&utm_campaign=Feed%3A+UsatodaycomScienceAndSpace-TopStories+%28Tech+-+Science+and+Space+-+Top+Stories%29": excerpts below: So how...

In GR, the strength of gravity goes to infinity at singularities. But what if in nature, gravity increases up to a certain cut-off, and does not continue to increase. If the cut-off is sufficiently low, could it be gravity is not strong enough to overcome pauli exclusion principle, and...

What are black holes? A theory I have is simple, and thus must be wrong. It seems to me that black holes are just extremely dense balls of matter, not holes at all, really. Just superdense balls. So, what is the real explanation, likely involving 105 vectors and 31 dimensions?

Hi All, So I'm a current physics grad student - who's supposed to give an outreach presentation (over skype) to some 5th graders who have been learning about Black Holes. I have no problem with the technical content - but does anybody have some good ways to explain things to elementary...

Hello everyone, I have a question that bothers me quite some time now,and it would be great to get an answer. I have been reading some time now about black holes,and photons,and how black holes attract photons and different theories says it can or cannot escape the black hole,and there`s...

Do we know the magnitude of gravitational force needed to violate the Pauli exclusion principle? Also, I my research has told me that violating the principle still isn't enough to turn the fallen star into a black hole. It could still become a neutrons star, so if that is the case, what...

What does quantum physics have to say about black holes?

according to special relativity the mass of an object increases with its velocity by the lorentz factor. the lorentz faktor would be 2.3 for when traveling at 90% the speed of light. as you go faster and faster the lorentz factor increases. it would be 22.4 when traveling at 99.9% the speed of...

So I'm watching this video: http://www.youtube.com/watch?v=TSOPq9rZYcU&NR=1 So it says that nothing, even light, can escape a black hole, "except for certain Quantum Mechanic situations" or something like that. What are these Quantum Mechanic situations they are talking about? Try to...

What will happen if two black holes are coming nearby? what will be the reaction (change in behavior)?

I propose to collect here some links which may be over the head of most PF users, but which should be invaluable for SA/Ms who feel the need to quickly brush up before addressing some thorny question involving the concept of certain topics related to gtr. In this post, Useful Background...

Is it possible for a star and a black hole to rotate each other in a relatively stable way without the BH feeding on the star and if yes could that star have planets rotating around it?

Hi there, (i) What does BPS black hole mean? Under what conditions can they form and where does it come from? (ii) What is the difference between an AdS black hole and a ordinary Schwarzschild? Thanks a lot!

Today I was conversing online in a gaming community and we began talking about relativity. Eventually we started talking about the "fabric of space and time" and how the common model to represent this idea was the old 'ball on a trampoline' idea; a 2-d model. To get straight to the point, we...

Hello... If time stops at the event horizon of a black hole..which means there is no motion happening or can be observed..does that not mean that the centre of a black hole is a place of absolute rest? Could such a place of ab/rest 'move' thru the cosmos (basically a black hole which is a...

This is my first posting to PF, so I do apologise if my post does not adhere to the etiquette of the forum. I had been considering black holes recently, and I had a thought/question which I am interested to hear people's feedback on, as I have not found a lot of information specifically on...

Right, it's been a long time since I've done anything physics related, and I've never been an expert to begin with, just a level standard, but was having a bit of a chat with a friend earlier and wanted to see if what we were saying makes any sense atall? We were having a bit of an...

Hi, I have to say that I'm not sufficiently educated in physics but I'm very interested in it so please excuse my silly questions. First I'd like to ask what determines the quantity of space that the black hole occupies. Is it just the amount of matter that imploded during the super nova...

Black Holes are Singularities... or vice versa? Ok so a Singularity is a place in space time where gravity or the things used to determine gravity become infinite. So does this mean that Black Holes are types of Singularities or Black Holes have Singularities in the center, or Black Holes and...