Black holes Definition and 1000 Threads

so, i love physics, and the more i look the more it seems our understanding of things are wrong. no planet #9, but now a mysterious planet-nine, dark energy, etc etc. so my question probably lies in theory, but getting close to applied physics. planet-nine, from what i have seen, the...

If stars have finite mass, gravity, and density, why does a black hole have infinite density, mass, and gravity and why doesn't it attract everything around it with such infinite gravity? Also, with infinite density, why are black holes all different sizes?

Do laws of physics apply below the event horizon? It appears as if black holes had such gravity as to have an escapr velocity higher than c, which means that things are pulled inwards at higher speeds than the speed of light. Or am I overlooking something?

I'm not a physicist so I am very igorant on this subject. From I know time gets slower and slower as you approach a black hole and an outside observer would never actually see matter being gobbled up. But I have read about stars get observed getting eaten away. How is this possible? And how do...

In my quote above from the thread https://www.physicsforums.com/threads/ultimate-fate-of-the-universe.898640/ I omitted consideration of dark matter because so very little is known about it. I am hoping someone here at the PF might be able to discuss the following questions. QUESTIONS Assume...

I know that a black hole it's a singularity, but its event horizon gets bigger the more mass/energy you throw in. I thought that like dark matter interacts gravitationally with regular matter , it would interact with black holes, eventually falling , increasing the mass of the black hole and...

Hey, was trying to think of what the safest possible place in existence would be and got to thinking of a planet surrounded by 6 black holes of equal size. Say the black holes met around this planet at the precious same time and are held in equilibrium, is there any particular reason that a...

I recently was watching a television show and something has lodged in my brain. They claim that as something approaches a black hole, it swirls in thru the accretion disk and speeds up to at times close to light speed before entering. They also claimed that it leaves an impression or image of...

What happens to the information about the objects falling into the black hole? Are their states somehow contained in the Hawking Radiation, and if so, how? Or is the information scrambled as it passes the EH?

PeterDonis submitted a new PF Insights post The Schwarzschild Geometry: Part 4 Continue reading the Original PF Insights Post.

AFAIK, scientists do not believe in the singularity, one way out of the singularity is quantum gravity, but as we have no testable theory of quantum gravity what do scientists think a black hole is?

can string theory reproduce hawking radiation in non-extremel black holes in 4D? i.e physically realistic black holes. do they exactly match hawking's calculations? what is the interpretation of hawking radiation in string theory?

So let's say an astronaut was being sucked into a black hole and was able to escape spaghettification and all the death a black hole brings. Since black holes bend space-time itself, the astronaut would experience a differen't time zone than an outside observer (time is relative). The astronaut...

I was asked if black holes are white today. I answered no, they're perfectly black to fit with classical physics since it's a high school kid who asked. It did get me thinking about Hawking radiation though and I haven't been able to find an answer to my question online. Is Hawking radiation...

PeterDonis submitted a new PF Insights post The Schwarzschild Geometry: Part 3 Continue reading the Original PF Insights Post.

Is a black hole a hole? What I mean by that, the word hole implies a structure that is shall we say like a plug hole in a sink. But a B/H is the result of an imploding star so surely it would be spherical. So really we are talking about black spheres which make much more sense in my head, also...

PeterDonis submitted a new PF Insights post The Schwarzschild Geometry: Part 2 Continue reading the Original PF Insights Post.

PeterDonis submitted a new PF Insights post The Schwarzschild Geometry: Part 1 Continue reading the Original PF Insights Post.

Hi. (I'm sorry for my poor English.) I'm looking for a good book on General Relativity, specially on Black Holes and Graviational Waves. I got Schultz book once ago, but it has a fuzzy notation and does not deal with the math as I suppose to. I know the basics of Differential Geometry, Topology...

Hi there! This has been on my mind for a while now, maybe someone here can help me understand. First of all, non-rotating black hole is an idealized concept, right? Why the term then? Other objects are not normally referred to as rotating stars, rotating planets, etc... And the main question...

Hello all, Is this a thing? I understand that a theory of quantum gravity is necessary to explain the physics at the core of a black hole, but it seems a black hole is the only environment energetic and dense enough to ignite a mass-energy feedback loop where colliding photons release the...

A PBH is a hypothetical type of black hole that is formed not by the gravitational collapse of a large star but by the extreme density of matter present during the universe's early expansion. It has been proposed that dark mater is made up of primordial black holes. One theory proposes that...

I'm referring to the black hole itself, not some object falling in it.Thanks.

I am trained in aeronatical engineering, spent a number of year supporting sounding rockets in the exploration of the Upper Atmosphere. Retired 16 years ago. Am interested in General Relativity and Quantum physics. Looking to explore and understanding of entropy... Black holes... Etc.

Recently I was reading Stephen Hawking's brilliant book "A Brief History of Time" and I believe I can recall him writing multiple paragraphs about falling into a black hole. I think I remember him saying that if you were to fall in all of time begins to collapse and the singularity will always...

The theory of cosmology assumes that the universe has been created from a single point by one big bang event. This theory implies processes which exceed the speed of light. <<Mentor note: This post has been edited to remove some content.>>

Can black holes convert dark matter into matter and vice versa? Presumably, a black hole can gain its mass from eating normal matter, or dark matter, or light. Then, it will eventually evaporate into Hawking radiation. I guess the Hawking radiation should include light as well as both matter...

I find this article hard to believe can there be so many Black Holes in one galaxy, if there are, why are there not many mergers recorded by Ligo. https://www.sciencedaily.com/releases/2016/09/160907215155.htm Computer simulations of a spherical collection of stars known as 'NGC 6101' reveal...

The event horizon of a black hole appears to be plastered with 'afterimages' of everything that ever fell into it. (Because gravitational time dilation makes every such object appear to stop at the event horizon.) Now, suppose an event horizon is 'full' as defined by the Pauli exclusion...

First, what are these 'particles' that appear with their negative mass counterpart and suddenly disappear very quickly and why do they do that? Now, I know the positive mass ones are allowed to escape the event horizon while the negative mass doesn't, thus fall into the black hole, but how does...

There's lots of other questions on the forum about 2 black holes, but I think this is different - and I can't get my head around which outcome is consistent with GR. Black holes here are simplistic - non-rotating and let's assume with a tiny accretion disk; just enough grains of matter to allow...

Hi PF Is there a way to see if a spin foam contains a black hole?

Is there a mathematical proof for the existence of black hole.

Hello :) Before I get to my topic I want to adress that I am new to this website and wish to apologize if my thread is incorrectly placed. I am interested in black holes and lately I have been trying to find some math which lays the basis for a black hole firewall. Sadly I haven't been able...

So having considered the classical depiction of a black hole resembling a whirlpool, my thought process is that a black hole must be a 3-d phenomenon. Therefore I can not see how a event horizon/swirlpool model could be plausible unless the centre of a black hole was spinning and literally was...

I know that I'm most galaxies black holes live in the center. I'm wondering if this is true for Galaxy clusters. Are there black holes in the center of galaxy clusters?

GUT's violate baryon number b/c baryon conservation is an emergent phenomenon second law of thermodynamics clearly applies to macroscopic systems, and are the result of the many ways in which atoms of macroscopic systems can be arranged. what if second law of thermodynamics though is just...

I am not sure if this is true, if it is can these black holes be the dark matter we have been searching for. https://www.sciencedaily.com/releases/2016/06/160622144930.htm Date: June 22, 2016 Source: Rochester Institute of Technology Summary: Astronomers have presented one of the most complete...

Dear All Gravitinos, It seems that the current string theory and loop gravity's explanation for the micro-states of black holes are all quantum mechanical and have no classic correspondence. I, in this day's arxiv, post a pure classic interpretation for this question, titled "Black...

What happens when charged particles fall into a black hole? Say like N electrons fall in, giving the black hole a net charge of -N. Since light cannot escape the event horizon, I imagine electric fields cannot either, since they are mediated by photons. So is that charge effectively lost until...

Greetings, There seems to be a supposition in astronomy that charged black holes are uncommon. Is this assertion well supported? According to a paper I found by Briet and Hobill, if you look at gravitational lensing alone charged black holes look just like regular black holes, but with a mass...

widely reported in the news is a second observation of 2 black holes gravitational waves. also reported are its implications Science World Report-Jun 15, 2016 Astronomers have reportedly started to think that dark matter could be made up of primordial black holes. According to Alexander...

It seems by this paper that there are more black holes than expected, so what is the expected density of black holes in the nearby universe? arXiv:1606.04996 (cross-list from gr-qc) [pdf, other] Constraining modified theories of gravity with gravitational wave stochastic background Andrea...

Hello every one . Simple question , What happens to the ended spacetime fabric in the singularity poing of the black hole if the black hole starts to move in spacetime ? Would the dead spacetime fabric at that point return to the regular shape of space time fabric ? ( as we know spacetime at...

What has a higher density? Black Holes or Singularities? I looked online and all I saw was that they both have infinite densities.

Once, someone had asked two interesting (though absolutely hypothetical) questions: 1) What should happen during the collision of two BHs, one consisting of matter (BH+) and the other consisting of antimatter (BH-)? Should they form a larger BH or should they be annihilated? My personal...

Yesterday I came across this article about speed limit on the growth of complexity in quantum gravity, that I found interesting: Theoretical results suggest a precise speed limit on the growth of complexity in quantum gravity, set by fundamental laws and saturated by black holes. The article...

Since the thread In LIGO’s pulse, how much comes from BH merging/ inspiraling where I questioned the late ‘ringdown’ part of the LIGO signal, scientists have pointed out that the main pre-merging signal could indicate various types of binary compact objects, including gravastars of similar mass...

I would like a discussion to quantify just how much mass is ejected at the poles (including the mass equivalence of the photons) when jets form. In quasars the black hole presumably reaches over a Billion solar masses, where the mass is proportionate to the mass of the galaxy and is also related...

Intriguing and informative story on gravity wave detection. Are gravastars an alternative to black holes? Is it possible the there are NO black holes? The collapse of mass into a ball of energy that presses out and stabilizes the incoming mass is a thought provoking alternative to the common...