Event horizon Definition and 308 Threads

Black hole drive in the film "Event Horizon" Cheesy movie, right? A lot of fun though. For those who don't know, there is a starship in the film called the Event Horizon, which utilizes an artificial black hole drive/engine in order to allow it to fold space, although it's probably more...

I recently saw a video where it was stated that black holes may have an inner 2nd event horizon where beyond it is trapped light and energy! I have searched the web for an explanation pertinent to this hypothesis but found nothing. Can anyone shed some light (if possible)?

Cosmo calculators and tabulators a primarily about the PAST expansion history and they give learners hands-on understanding by being able to vary the model parameters and see change. That's good. I sometimes notice a difference here at PF between how posters with mainly verbal understanding...

Varying coordinate systems in GR has given me a new perspective that may help to resolve a problem that has been nagging at me ever since I began working with GR. In every problem I've ever dealt with, a complex mathematical result describes an impossible scenario, something that cannot occur...

Is there an event horizon beyond the visible universe where the laws of physics kind of get cut off, a limitation to the reach of gravity. I ask this because if space is expanding there must be a point that if light left Earth it could never come back because the return distance is expanding...

hi, I am not a physicist so sorry if this is a stupid question, its just curiosity. how thick is the light like event horizon of a schwarzschild black hole, for instance, what the closest distance scale that an infalling photon and an escaping photon be, and whatI is "inbetween"? I've heard...

In the book "The Black Hole War" by Leonard Susskind, he states that a person can live past the event horizon (to a certain point, of course) in a massive black hole because "the horizon of the larger black hole would be so large that it would almost appear flat. Near the horizon, the...

I'm curious - once an object passes the event horizon the image of that object remains on the event horizon only to become more redshifted rather than dissipating. two questions: 1) why does the image remain if the light stops traveling? if the light cannot travel to the observer, than there...

Hey guys this is my first post so I hope this doesn't come out stupid since I only know slightly more than a layman. Recently I have been trying to wrap my mind around what happens inside an event horizon. Specifally I have been confused with the matter which resided inside the schwarzchild...

Hi, I've heard a fair bit about the event horizon of a black hole. What exactly is the event horizon? Thanks,

Good morning. I am wondering what is the nature of virtual particle production beyond the event horizon of a black hole. When a particle-antiparticle pair is created from the vacuum, it takes time for them to attract electromagnetically and annihilate; but since the event horizon separates...

In class, our instructor talked about a pecularity of black holes. When virtual particles come into existence for an instant at the event horizon, sometimes one is trapped by the black hole, while the other is able to escape. My question is, what determines the rate at which particles are...

I'm not sure why the other thread was locked, unless you're banning questions? I'll ask it in as clear a way as possible. When an observer approaches an event horizon to one plank length away one of two things must happen: 1). Any observers previously falling towards the black hole...

Is it true that massive observers travel with c when passing an event horizion? I know that light cones get tilted at the event horizon. But every observers travels at light speed there? thanks in advance

When classically deriving the Schwarzschild radius of a black hole, the kinetic energy of an outgoing particle (moving at the impossible-to-achieve maximum of the speed of light) is equated with the gravitational potential of the black hole at that point. \frac{1}{2}mc^2 = \frac{GMm}{r}...

It is said nothing can escape the Event Horizon, not even light. How about an entangled pair that is inside the event horizon and outside it. Would they still be entangled such that they still form correlations?

It is often said that passing the event horizon for a large black hole is basically a non event as the size of the tidal acceleration at the event horizon depends on the mass of the black hole. But let's consider something else; what happens to the stars in front of a free falling observer...

As I currently understand it from the point of view of an observer falling into a black hole it takes a finite time to cross the event horizon and reach the singularity. From the point of view of a far away observer the person falling into the black hole never actually crosses the event horizon...

A clock falling towards the event horizon of a black hole would appear slowed down to the point of being frozen in time (or almost). But I'd like to understand properly what happens to the length contraction experienced by an observer falling together with that clock. Would he experience...

In the popular physics books that I enjoy reading, black holes are described as containing a singularity of zero volume that contains 100% of the mass. I can't envision this, since 100% of the spacetime inside the event horizon would then be empty space except for virtual particles. Is this...

Are there any known metrics in which black holes do not have the Schwarzschild radius? Specifically, I'm interested in whether it's possible for a black hole to have an event horizon which is not of the form: constant * mass.

If the postulated Higgs field has a non-zero vacuum expectation, shouldn't the typical black hole be ingesting Higgs particles at an alarming rate?

Ok, although I had hoped to avoid having to ask a stupid question, it seems as though I'm just too dense to figure this one out on my own. Generally I can, with the help of Google, and the combined wisdom of the internet, deduce an answer. But either Google, the internet, or my brain has failed...

From a far away observer, thing falling into a BH takes infinite time to cross the horizon. At the same time, the horizon radius is proportional to BH's mass. But if we never really see any energy fall into a BH, how did it acquire a horizon in the first place as seem from outside? i.e. What...

I understand why you would be ripped apart if you enter a black hole, but I don't understand the fact that if the black hole is large enough, You would not be ripped apart if you passed the event horizon. And, some black holes you would be ripped apart outside of the event horizon? Can...

What would you see if you were on an aircraft near it that could hypothetically survive? Would you see light frozen in time, but technically gone? By that I mean would you just see an afterimage of it even though technically it's gone? Or Would you see light just vanish into the black...

I've got two questions here 1a What is the definition of an event horizon of black hole? In Carroll, he defines an event horizon as a boundary of causal past of future null infinitiy. What is the physical interpretation of that? 1b What is the difference between event horizon and Killing...

So, I remember once watching a lecture series on relativity. In one of the lectures which discussed black holes, the lecturer spoke of what it would be like to actually fall into the black hole. Of course, he did the whole talk about the outside observer seeing the person falling in slowing to a...

In every animated depiction of a Black Hole, we are lead to believe that the Event Horizon forms along the Equitorial Plane of the Black Hole. Is this true, or can the Event Horizon form anywhere around the Black Hole?

As I understand it, time (as seen by a distant observer) near event horizon of BH slows to "zero". It makes me wonder how long (as seen by a distant observer) it takes for matter to fall to the event horizon. I would guess this would be calculated via some appropriate integral (I am not...

Can a freely floating observer do an experiment that tells him when he is crossing the event horizon?

Consider a double slit experiment at the event horizon of a black hole, with 1 slit on each side of the horizon, one observer inside and 1 outside, inside observer should observe interference by equivalence principle, whereas outside one should not, since the photons can't enter the second slit...

hello, what does exactly mean geometrically that time and space switch roles at the event horizon of a nonrotating black hole?. I understand that the - for time becomes a + and the + for space becomes -, but how to interpret it geometrically? also I want to know if after the event horizon...

does anyone actually know what happens when something reaches the event horizon?

It takes an infinite amount of time for any particle to cross the event horizon of a black hole, from our point of view as an outside observer. Which means that since the big bang, not a single particle has ever crossed the event horizon of a black hole. They just come closer and closer to it...

Hello, I know that time dilates while approaching the event horizon of a black hole, but explanations failed to make me understand HOW MUCH of each phenomena causes this as an object approaches the EH. On the one hand there is photon delay due to gravity acceleration approaching the speed of...

Don't know where I picked it up, but something indicated to me that inside R_eh = 2GM/c^2 lies a black hole whose R_bh = GM/c^2. And that at R_bh lies the energy singularity. And that at R_eh there is not an energy singularity, but only an end to communication with the world outside. I...

Perhaps you know the question what the captain of a spaceship trapped inside the black hole event horizon shall do in order to maximize the time left to being sucked into the singularity. I know the following idea (and I used to believe it over years :-) The geodesic equation of...

I'm having no end of trouble with this seemingly simple problem: Homework Statement What's the minimum mass of a black hole for which you could survive a fall through the event horizon without being ripped to shreds? Why would you be ripped to shreds for smaller black holes? Homework...

Homework Statement Show that a black hole's event horizon will never shrink due to a Penrose process. Homework Equations M_{ir}^2 =\frac{1}{2}(M^2 + \sqrt{M^4-J^2}) The Attempt at a Solution It is easy to show that the irreducible mass will never decrease, and I know of a result that...

Consider an electron traveling through space at 99% of the speed of light. It passes within the event horizon of a black hole. We know that it can not escape. This implies something to me and I am wondering if it is correct: Since it does not come out, that means that the acceleration by the...

Sorry for what may be very basic and unscientific questions, I'm a brand new poster! Regarding black holes: It is my understanding (please correct me if I am wrong) that if an astronaut were to approach and enter the event horizon of the black hole, those watching from the outside would...

as "tidal gravitational forces" ripple outward, does that not change the curvature of space, making the region around the black hole very dynamic? so wouldn't the event horizon not be a sphere, but rather a wavy dynamic structure? because the "measured gravity" at a specific radius out at any...

Cosmologists seem to refer interchangeably both to a big-bang origin just beyond the limit of present observation, and to an observational horizon where the rate of expansion of the universe exceeds the speed of light. The notion that looking out in space entails looking back in time gives...

Has anyone ever considered the outer event horizon of a point particle (classical electron perhaps...)? Does it make sense to consider it Kerr and charged because of spin? Is it comparable with a Planck length? I know we would need a quantum gravity to deal with it, I'm just curious to see what...

Homework Statement Compute the horizon of the universe as a function of \Omegam in a flat universe with both matter and a cosmological constant but no radiation. Homework Equations Event horizon distance r = a(t)c \int_0^tcdt'/a(t') The Attempt at a Solution No idea how I'm...

Kevin Brown http://www.mathpages.com/rr/s6-04/6-04.htm gives the acceleration of particle in the Schwarzschild metric as measured in terms of the proper time of the particle as: \frac{d^2 r}{d\tau^2} = -\frac{m}{r^2} Does this not cause a problem for those that assert Schwarzschild...

I have recently finished "Gravity from the Ground Up: An Introductory Guide to Gravity and General Relativity". Great book, but I am confused about the behavior of time at the event horizon of a black hole. I spent some time looking at existing threads on this site, but was unable to find...

Hi! There's got to be something wrong with the following method to take photographs of the area inside a supermassive black hole, but I can't figure it out. 1. Lower your spacecraft to just outside the event horizon. 2. Extend a uniform steel bar with cameras embedded in it...

Reading "Exploring Black Holes" I find that a particle following a geodesic towards a black hole always reaches the speed of light c when crossing the "event horizon" regardless of the reduced circumference that the particle begins at (1mm or 10 million light years). This would also...