Light in a black hole

You can reverse the path in a convex lens and get the same effect though. Just try flipping a lens to simulate this. Light can always travel the same path in both directions, no matter the geometry (except in black holes somehow?)

Even though black holes emit massive amounts of x-rays and radio, and are very bright objects, somehow they don't emit anything because muh gravity, also Hawking said he's pretty sure event horizons can't exist because muh thermodynamics.

Haven't studied GR in a whole lot of depth but I believe the pop sci answer is correct in this case. It's not as if you are losing directions though, it's just that all possible geodesics from a given point are inevitably curved back towards the center. From what I have heard it really isn't about speed or momentum, space is curved in a way that there just isn't a path out. I don't think it is correct to say that you are losing dimensions.

>Hawking said he's pretty sure event horizons can't exist because muh thermodynamics
...You mean the guy who came up with Hawking radiation that entirely depends on there being an event horizon which can prevent pared particles from annihilating?

[Citation Needed]

Aside from Hawking radiation, black holes don't emit anything - but they can form energy accretion disks as matter is accelerated around them, and all of that which ends up on our side of the event horizon, yes, is quite bright (see also: quasars, the brightest things in the universe), but that which falls beyond said horizon is gone for good. (Or, at least, from the moderately sized ones on up, gone for longer than matter in the universe has time left to exist.)

I guess referring to some shit that came up while they were figuring out the information paradox. I think some of the models or whatever kinda made the event horizon into more a blurry boundary insted of a fixed line. But the Journalist ran with it as Hawking getting rid of the event horizon.

He is totally wrong though. Hawking doesn't doubt event horizon exists.

well yeah it's not a perfect metaphor I was just trying to help you visualize it, it's like a 4d lens that goes in all directions
here I drew a picsher

Yea, get the concept, but I dont think its totally valid. I think the direction arrows on your paths could be reversed in all of those cases.

I mean, sure, people keep saying its not the case in a BH, but I'm just trying to get a better grasp of why other than: "it just is that way it is"
From what I understand of how light works, and GR space time geometry, light path should still be reversible.

I obviously don't know enough here, but i never seem to get great answers to these questions when I have looked.

You are assuming there is time reversal symmetry. I don't know if this is a valid assumption since I haven't studied black holes in depth but remember that time is being warped as well so the intuition that you could just reverse the whole system isn't necessarily well placed.

I think they also lose energy through gravitational waves

This implies photon inside the event horizon can escape if they started closer to the edge. That's wrong. Photons can't travel outward at all.

I always had it described to me that the singularity in the black hole is infinitely small yet still shrinking. In a sense, it is still "falling" and creating an ever-deeper hole as it goes. Thus, there is an infinitely deep hole for light to "fall" into, and any light that falls into that hole after the collapse of the star can never catch that singularity that is forever falling ahead of it.

As more and more matter is trapped inside the event horizon - that cliff edge of no return - it gains more and more mass, and thus the radius grows, but the matter and energy that falls in never reaches the singularity itself.

This imagery is likely faulty as well, but I'm fairly certain, at least, that light does not circulate inside a black hole, rather, once over the event horizon, all probabilities can only go in one direction.

There's the added difficulty that time slows as you approach the event horizon, and effectively stops at its edge, where it redshifts beyond perception. It maybe then, from our perspective, nothing ever actually enters the horizon, but it'd nonetheless expand from the additional mass. And there's the other problem that gravitational effects only propagate as fast as the speed of light...

So, yeah, now I'm just confused.

> Light in a black hole
Black in a White Girl Hole.

To be honest, we really don't know. We have plenty of models that suggest certain things will happen, but it's important to remember that they are only models. The environment around and in a black hole is all but impossible to replicate and experiment on down here on Earth, and even the closet ones are thousands of light years away making them difficult to observe.

Non physicists here...

If mass distorts time, wouldn't it make more sense to say the time stops at the event horizon?

Also, if light travels at c, then relative from the light beam's perspective time slows down to a halt, right?

If both premises are correct, then what happens there? For the light time is not elapsing, but one second got stretched to infinity...

Weird stuff...

Time curvature doesn't influence light the same way it does to objects with mass as far as I know. This is why light can never gain or lose velocity in relativity.

They lose rotational energy I belive, doesn't relate.

This is very close to a paradox which has been debated, and i dont think it has been solved well.
I think some solution just said there was a duality(on the horizon and below), not very satisfying, but i guess they have some shit to back it with.

of course it does matter, hawking radiation also depends on angular momentum

Well, you can mathematically describe and predict the effect, the the resulting lorentz transformations and the like. The effect was predicted before it was ever observed, though it was previously thought that some here-to-for unknown mechanism must prevent black holes from happening, as the phenomenon itself was just too fantastical, and just raised far too many spooky issues. Nonetheless, it seems they are out there, and fundamental to the universe's formation.

i.4cdn.org/wsg/1501795046736.webm

But while you can mathematically describe the consequences of its existence, part of the problem is you can't say anything, even mathematically, about the singularity itself. Save, "yup, that's a singularity."

I haven't heard this, but i think you get hawking radiation even if you dont have angular momentum. Otherwise you could make a black hole that would never evaporate.

Relativistic angular speeds should change particle emissions.

There's literally nothing wrong with information being 'lost' inside a black hole.

That video is fucking amazing, the sound blows your mind

I think most physicist would disagree here.

It's one of the big debates about Hawking radiation - whether it results in information loss, thus violating thermal dynamics. SFAIK there's still no adequate solution, and even Hawking threw his hands up at it, though it's generally assumed said radiation still happens, only some of the details such as "cosmic censorship", or lack thereof, have yet to be worked out.

Better hope it's a thing, or those tinfoils might have been onto something when they were screaming about CERN - though I suppose we wouldn't find out until the century was out... And, yeah, all those cosmic rays hitting the atmosphere would have tossed those whole planet into a pit of no return some billions of years ago.

>Implying SERN didn't get away with it and destroyed countless worlds to conduct their experiments

/joke

I do remember reading about how a ring of black holes with overlapping event horizons, or rapidly spinning black holes, might theoretically create a temporary naked singularity, capable of emitting light.

Can't seem to find the original article, but Wikipedia seems to make reference to something related:
en.wikipedia.org/wiki/Naked_singularity#Predicted_formation

That's the plot of Steins;Gate

We just need to create a form of matter that's a gravitic dipole and pump it into a black hole until the gravity is weakened enough to see inside.

Back to your thread, Mr. Titor.

...

If a meteor passes close enough to the earth, it won't be able to escape. Same thing for black holes. And in case it wasn't obviously the black hole is a point surrounded by black. So since that black isn't the actual black hole, stuff can still happen in there. You just won't see it. Light can orbit for years (or maybe the time dilation makes it forever) inside the event horizon and doesn't necessarily need to collide with the hole itself. As for light radiating out of black holes, I think it's to conserve information or some buzz word like that.

It's too complicated to explain here, but it's basically a cosmic version of the coriolis effect. Google it.

All light cones within the event horizon of a black hole are inward-pointing. Geometry prevents there from being a direction light could travel so that it's "distance" from the center is non-decreasing.

The whole concept of time breaks down beyond the event horizon (in our current models at least.
Hawking radiation is caused by quantum interactions near the event horizon, and actually causes an information paradox. What it does is cause black holes evaporate, with the information of the radiation not having any links with the information of the contents of the black hole.

>light can travel back out, but it is red-shifted into a undetectable state by the time it crosses the event horizon
That sounds like what a distant observer would see watching something fall into a black hole, not about light escaping from inside.

>geometry inside the black hole is so curved that any light going out, would simply curve back down before it could escape the event horizon
Basically this. In GR it's all about the spacetime interval [math]ds^2 = dx^2-c^2dt^2[/math].
Interval < 0 is timelike separation (inside future/past light/causal cones), > 0 is spacelike (outside), = 0 is lightlike. Light always moves on lightlike intervals.
When you work out the spacetime interval in curved spacetime near a black hole you get the Swarszchild metric, when you set that to zero you get light paths and you end up with [math]dr=c(1-\frac{r_{S}}{r})dt[\math]. Inside the event horizon (r 0 then dr < 0.
>how is the same path the light used to get in, not valid in both directions
If dr > 0 then dt < 0. It's mathematically valid but physically it's time reversal.

why isn't it working?
dr = c(1 - r_s / r) dt

Nigga just jump up.

Now climb some monkey bars, hang upside down then kick off.

Some physicists are ok with the idea of infinitely small central singularity while others think the math is pointing to an incompleteness in understanding. The rubber sheet idea is ok most stars and planets but really doesn't help with black holes.

As far as the event horizon goes, approaching it would probably mean getting blasted with photons as the intense gravity condenses time intervals. From that perspective, photons from a wide range of times would still be around at the very edge.

It's true that an outside observer would see the object approaching the horizon slow down infinitely and redshift infinitely. Effectively each particle gets smeared across the surface of the event horizon and the horizon expands a little. Also note that instead of volume, the horizon's surface area is proportional to the overall mass.

youtube.com/watch?v=KePNhUJ2reI
PBS Space Time has the best explanation for this shit

>and even Hawking threw his hands up at it
That seems doubtful...

en.wikipedia.org/wiki/Black_hole_information_paradox#Hawking_radiation
Well, not literally, of course. He can only move so much.

Is it not more likely that the photons are being pulled in because they are particles

Event horizon is a point of infinite gravitation potential, time stops at that point, and light only ever travel zero distance.

>escape velocity
That's dictated by the classical behavior of an object slowing down before it falls back to the body in question. Light does not slow down; it just gets red-shifted.

Because the space is literally being subducted

The escape velocity is greater than the speed of light, that is what you plug into the gravitational time dilation equation to get the gamma factor, and when you put that in you get a complex number (greater than speed of light escape velocity), which is bullshit, basically read what I wrote

experiment.com/projects/xyzqnmkbtxfjlkaplvum

Not only is the light slowing down so much by gravitational lensing (REFRACTION) due to the intense gravity, but it's also being reflected back 180 degrees by gravitational lensing

>Pop-science and the internet
L0Lno fgt pls

But if you travel at c, you move from A to B is zero time (from your point of view)...

>That sounds like what a distant observer would see watching something fall into a black hole, not about light escaping from inside.
Yea, seems i have been confused sometime in the past, someone was probably talking about that, and not escaping past the horizon.

Is the lights inability to traverse both directions then related to the flip in space and time? Interpreting stuff like that from the math isn't something I can do much of.

And i heard the light cone example, but I was under the impression that the warping of the light cones should only happen to objects with mass, As light is on a fixed trajectory until it interacts.

I mean light is fixed in time btw. Obviusly it can curve due to gravity in space.

No if you travel at c that's not from your own point of view.
If you travel at c that's c relative to a stationary observer and the stationary observer sees your clock ticking at rate 0 and says you will measure 0 time for your journey.
But for you time looks normal so you measure non-zero times.

>Is the lights inability to traverse both directions then related to the flip in space and time?
Calling it a flip probably simplifies too much.
If you fall into a black hole to you time will still seem to be going forwards normally and you'll still seem to be able to move around in 3D normally. If you have a flashlight and try to signal for help, you can send photons in all directions like normal, but to a distant observer all your movement and photons would have dr/dt

It IS how it is though. You have to accept that and then try to understand it, not reject it until you understand why. It already is that way. If something is the way it is, but doesn't make sense in the context of your understanding of something else, then its the latter which lacks understanding.

Wrong.
It has to do with energy, not orbital motion.
As you attempt to escape a gravitational field or "well", you lose whatever energy you have to potential energy. The idea is that every photon, or "packet" has a specific energy. As the energy packet attempts to escape the gravitational well, it loses energy, "stretching" its wavelength. Hence Hawking Radiation. The idea that black holes are actually just red shifting the dick out of light.