Black hole Definition and 999 Threads

I find a very interesting site that shows us what it would be like to travel to a black hole or a neutron star. https://apod.nasa.gov/htmltest/rjn_bht.html Have fun !

I'm just a layman here, who enjoys science and astronomy. I was reading about the temperatures of the cores of black holes being extremely cold, and how time at the singularity...progresses super, super slowly. But this is only as measured from an outside observer's perspective (such as from a...

I hear people say that even light cannot escape from black hole.So how big is this black hole?Why gravitational pull is very high? Does it have any escape velocity like Earth have?

If 2 black holes have event horizons slightly overlapping,can they ever be separated "theoretically" into 2 separate event horizons given we can apply extremely high forces to pull them apart or will it keep stretching and overlapping even if they are pulled apart?

I've heard some explanations of the Black Hole firewall involving broken entanglement releasing energy that frankly I don't understand, but I have another way to think about it and I'd like to know if its even approximately correct. As I'm getting closer and closer to the Event Horizon time...

Hello, Here's an interesting question inspired by a homework probem (not mine), we know that circular orbit (for scjwarzchild black hole) exist only if L ≥ sqrt3 c Rsch=Lisco . Where does this inequality come from? do you have a lecture which can help me to understand? Thanks

So the title pretty much sums it up. I'm having a heated discussion on this topic with a friend so yes/no at the end would be nice :wink:

I am unable to find any paper or book on Kerr-Bolt solution. I need to know its derivation. Please if anyone can suggest some material on it? I will be very thankful.

I saw a video of a talk by Susskind discussing his ER = EPR idea. This post isn't actually about that talk, except that it got me thinking about wormholes. Without exotic means, I understand that it is basically impossible to have a traversible wormhole connecting two distant points in space...

https://www.sciencedaily.com/releases/2017/12/171206131946.htm A team of astronomers, including two from MIT, has detected the most distant supermassive black hole ever observed. The black hole sits in the center of an ultrabright quasar, the light of which was emitted just 690 million years...

I have to 'question' the logic asked in the 'title question' asked in this artical: https://newatlas.com/most-distant-supermassive-black-hole/52508/?utm_source=Gizmag+Subscribers&utm_campaign=2151ebbb0d-UA-2235360-4&utm_medium=email&utm_term=0_65b67362bd-2151ebbb0d-91583997 It seems to me that...

This question pertains to a Sci-Fi story I am writing, using the concept of a black hole and Hawking radiation which is developed as an energy source, and I'd like to get some technical details worked out. My understanding is that an extremely small black hole will very quickly cease to exist...

Hi, what would happen if you took 1 cubic meter of matter from pulsar into empty space what would happen does the matter will expand since there is no more strong gravity does will it explode ? would like to know your answers

Many diagrams show light cones tipping over when closer to a black hole singularity, such that emitted light can have a downwards (negative time) component in the distant observer coordinate frame. e.g this diagram: or this one: or this one: However, other diagrams show that the light...

Suppose life would evolve on a planet near a black hole, like the water planet on Interstellar. And just like on Earth, they eventually discover a theory of relativity and also how to send a rocket away from planet/black hole and back. Could they take advantage of the huge time dilation between...

As I read in May, approximately 8 candidates existed as candidates for black hole mergers. http://www.ligo.org/news.php This is no more written in this link. Are these other candidates already excluded? Are there any papers intended about these candidates?

At the event horizon for a black hole is R=2GM/C^2 This means that, as a star collapses, it gets more dense until this limit is reached. Assuming a consistent density (just an approximation as I know this will not really be the case), the Mass will reduce proportionally to the cube of R, but...

In a thread a decade ago https://www.physicsforums.com/threads/how-to-survive-in-a-black-hole-myth-debunked.170829/, there was a discussion about the paper https://arxiv.org/abs/0705.1029v1, in which the authors discuss the way to maximize one's survival (proper) time after passing the event...

I've read some articles about Hawking radiation, The holographic principle and obviously I'm well aware of the law of conservation of energy. Is there any research up to date that points toward a possible answer? Is Hawking radiation really a thing? Is it possible for matter/anything to actually...

I have been told the speed of light is constant and does not waiver. This would make sense as light has no mass I am aware of. Pictures taken during a solar eclipse seem to prove gravity bends light. Could it be however that the light is not bent, only the time/space light is traveling through...

On November 15, 2017, LIGO Scientific Collaboration announced the observation of another binary black hole coalescence. The gravitational waves were observed by the twin LIGO detectors on June 8, 2017. This is the lightest black hole binary observed so far, with component masses 12 and 7 times...

Homework Statement It is my idea so I hope there is no problem in assignment. How long takes small black hole to eat an ordinary star, if the black hole sit in the center of star? Homework Equations We probably should suppose that star is ideal fluid (incompressible). (1) ##\frac{dm}{dt}=A\rho...

As I understand it, if you were to inject lots of dark energy into the molten core of a planet, the planet would inflate like a bubble over time until the forces of dark energy and gravity were in balance or until the bubble popped. If you were to inject dark energy into the interior of a black...

Dear all, I am currently doing a project about the light trajectory near Schwarzschild black hole. I wrote down a couple of differential equation and I have created a C++ program hoping to solve the orbit of light. However, the program results turn out to be quite weird. The differential...

Is it not true that solutions of the EFE are stationary, in 4 dimensions? If so, it seems that the solution describing a black hole merger would be intractably complex. Are current descriptions analytical solutions, or numerical?

Hello, layman here, I have a simple question, could you please clear this up for me? Whenever I read about the information paradox, it always appears to me that it is automatically assumed that quantum fluctuations / virtual particle pairs are predictably random. Which leads to the loss of...

When replying to this thread: https://www.physicsforums.com/threads/the-nasa-zero-gravity-flight.927136/ I became uncertain of my understanding of the physics after the plane starts to descend. What I imagine happens is that your forward velocity would remain constant and you would be...

Feel free to correct anything I state here. I'm trying my best to understand some rather complex (for me) ideas about time dilation. So if I understand correctly, increasing velocity compresses time, causing you to exist more slowly relative to anyone not moving at that velocity. Similarly, the...

Unfortunately I didn't find a thread discussing this issue. First I will sketch the standard argument that one should not use the rocket engine and try to accelerate away from the singularity. Then I will try to identify the problematic part of this argument and ask for your comments. 1) For...

Cosmic rays are overwhelmingly positively charged. Hence, whatever is emitting them must be building up an enormous negative charge. So should we expect to see highly charged Reissner-Nordstrom black holes out there? Perhaps even near extremality?

I am wondering if there is some type of matter in the core of the Black Hole. Is it possible to compute the distance from the surface of the Black Hole Core to the Event Horizon? Oh that would be fun to calculate.

If you are observing a particle enter a black hole, you watch its proper time go to zero at the event horizon as it is 'frozen' there from your frame of reference. What happens in your reference frame as the black hole evaporates? While you can't illuminate where the particle is from your frame...

Hello! If energy bends spacetime, then an object moving at high velocity will bend spacetime a lot around it due to its really big kinetic energy. It follows, that an object can become a black hole at extremely high enough velocities. But, since velocity is relative, we can find an observer for...

I know this is some kind of exercise problem, but it isnot widely discussed in general general relativity textbook. Sorry to post it here. I want to calculate the mass and entropy of non-rotating BTZ black hole using Euclidean method. When I calculate the Euclidean action, I always get an...

Can someone explain to me why there must be a real/meaningful space inside of a black hole? I have been autodidactically working on understanding the mathematical concepts that general relativity is based on, so I've never had anyone to ask questions to (until it occurred to me to find a forum...

Sorry, I'm not sure what is the more appropriate word to use: shape or form. Let's to the question: How do we know what the shape of a given black hole is? I mean, how do we know whether it is spherical or whatever other form it has? Specifically, where do we look on the equations to get this...

Since in the beginning of the universe all matter was concentrated in a ridiculously small space, how didn't the whole universe just ended up as a huge black hole right after the gravitational force appeared? Only solution I can think of is that space itself was expanding faster than matter...

I read recently that no information comes out of a black hole. Doesn’t the mass information exit a Black hole with ease? Say I am orbiting a black hole and looking away. If while looking away the black hole gobbled up another star I could tell immediately that something had changed inside the...

Hello all, To my knowledge, there are still a lot of questions regarding the specifics of black hole formation. My question is in regards to formation time. I've read that the actual formation takes "less than a second" according to the equations. Does anyone know where time shows up in the...

At one point I read there was the concern that a black hole could lose bits of information. Then a theory arose that showed that all the bits in a black hole were to be found on the surface of the black hole. Thus if there were let's say 1000 particles in a black hole each of which could be...

I have come across the following multi-explanations of how Hawking radiation/evaporation of a black hole happens: Particle/anti-particle story: particle/antiparticle pair creation from vacuum near the event get torn apart - one going into black hole, the other away; in some of these...

What occupies the space between a black hole's event horizon and the singularity? Stuff hurtling to the singularity? Vacuum?

I was reading about the latest black hole merger discovered by LIGO. https://www.ligo.caltech.edu/news/ligo20170601 The article states that the deflection of the arms over 4km was 1×10^-18 meters for an event 3 billion light years (ly) away. If I assume that gravitational waves follow the...

A couple of points I need clarification on. Objects outside of the event horizon feel the pull of the black hole - so the closer the object is to the event horizon but still outside of it the more pull the object feels to be sucked into the event horizon? Is that the correct view? As far...

Having trouble with understanding this equation and its theory.

So there will be a few hypothetical in the original story here, but in the end ill wrap it up with what I believe are facts. My question, how does Einstien’s theory of relativity interact with consciousness? Let’s say I have a twin, he becomes a farmer and I become an astronaut. I go to space...

Reading the post below on event horizon of a black hole (BH) got me thinking about the photon sphere of the BH. We all know light will travel around this photon sphere and how light from a source would completely travel back to it's source if one could see it real time, we all know this from...

I didnt understand a concept in black holes,So I ll try to make a vısualization to the process to explain my ideas properly. Let's suppose we have a star with mass ##6M_ο##.We know that this star will turn to black hole,So Let's come to the end of the life of the star.It will explode as...

Hello, I would really like a book like Susskind's "An Introduction To Black Holes, Information And The String Theory Revolution: The Holographic Universe" but not so condensed. If you have anything to suggest please do so. Also, if you know of any book that contains any part of the above book in...

General relativity passes test at Milky Way’s central black hole by Ken Croswell For the first time, astronomers use stars orbiting a supermassive black hole to test Einstein's general theory of relativity, finding no sign of a fifth fundamental force. Links: John Batchelor Show...