/sci/ - Science & Math

>>11120154
elivaders violate th law of physic

an elivader drops down which in turn will trhust you down but instead you should be moving upwards since th elivdaer is falling and not you,

this violate pfysic

you fall down with the vaer bu the vider should be knokcing you up bcause the elivder gos down and you go up

look a this diagream

[]
that is th eolviat

[o] that is you in the elivator

[] when th elevator go down

o
[]
you are no on upt of the eilviartor

which means that you are on top and it is down below you

hllow?

hllow!?
hellow!?

of couese this violates the laws of fycjis

the elivator gos down and you aren't gonng down thogh bso the eleivator goes down faster han you and the gravity pulls you down at a separate speed beause they lever l pully pull th eviliator down and you stay put but gravity pulls you down but up because the elivoatrr is movning down fastr han yo are due expain thot dumb erh uhA? vader no polllel?

>>11120157
Not an argument.

>>11120154
>At a black hole's event horizon, time dilation becomes infinite. Relativity shows this.

Source on this?

>>11120167
https://www.google.com/search?q=black+hole+infinite+time+dilation

>>11120168
It's called spacetime for a reason

The effects a black hole has on space, it also has on time

Also to answer OP's question: no one knows. Stephen Hawking was working on literally this question before he died. His last paper was a VERY short mini-essay about how nothing ever actually enters a black hole from our reference, it just gets stuck to the outside and forms a kind of hologram that keeps all of its information encoded forever.

/rant on
gravity compresses 3d space so hard it converts it into 2d space. The event horizon of a black hole is a portion of our universe converted to 2d space that is shaped like a hollow ball. The surface of the ball is the plane of this 2d universe.

Where's the part of the rant that gets super crazy. Time and space are linked. Our universe is 3 spatial dimensions and 1 temporal dimension. Just as you convert 3d space into 2d with extreme gravity, you convert 1d time into 0d time and time becomes non-existant.

Now if a 2d universe can be created by compressing space of a 3d universe, how do you create a 3d universe, such as our own? Simply by creating a black hole in space where there are 4 spatial dimensions. What if reality has 4 spatial dimensions, and what we see as our universe is really the event horizon of a black hole in 4d space? Also, would this imply that 4d space also has 2d time? 4 dimensional objects are already impossible for humans to wrap our heads around, but how could you even explain 2 dimensional time?
/rant off

>>11120179
>gravity compresses 3d space so hard it converts it into 2d space. The event horizon of a black hole is a portion of our universe converted to 2d space that is shaped like a hollow ball. The surface of the ball is the plane of this 2d universe.

This doesn't make sense. There is shit inside the event horizon. It can move inwards, it just can't move outwards. So it's more like 2.5 dimensions.

Basically there's many more dimensions above what we understand currently and it's not a question worth asking if you want an answer until we develop M and String theory further

>>11120154
>Given this, how is it possible that we, in our current perspective, observe black holes to exist?
We have never 100% observed a black hole to exist, and such a thing is not possible with our technology.

Hypothetically with proper technologies, gravitational waves or such it's still possible to traverse into the interior and build things there out of scalar matter.

>>11120191
>It's possible to do magic with magic

einstein predicted black holes as a theoretical object but said that since the rotational speed of a body increases exponentially as its radius shrinks, a black hole would be impossible (it would shrink to a certain point, spin to near-c & angular momentum would explode it outwards, balancing it against its own gravity)

maybe he's right

>>11120154
We have observed the accretion disk of a black hole, it has been OBSERVED.

>>11120205
Saturn has an accretion disk. An accretion disk doesn't mean there's a black hole.
Anyway, you didn't answer the OP.

>>11120207
The fucking size of the observed accretion disk suggests a black hole.

>>11120208
Lots of things we see 50 AU away "suggest" black holes.

>>11120168
Best I could find is

Any object approaching the horizon from the observer's side appears to slow down and never quite pass through the horizon, with its image becoming more and more redshifted as time elapses. This means that the wavelength of the light emitted from the object is getting longer as the object moves away from the observer.

But this has never been verified yet, only theorized with our current models of gravity (General Relativity).

>>11120200
>maybe he's right
we have an actual picture of a black hole you know

>>11120210
Probably because a lot of them are?

>>11120213
>we have an actual picture of a black hole you know
We actually don't.

>>11120212
Here is an interesting point.

What if you took a rod 100,000KM long and threw it head-first at a supermassive black hole (supermassive so the tidal forces wouldn't damage it.)
The first atomic layer of the rod hits the event horizon and freezes. Now what happens to the other 99.999999% of the rod?
It all hits mostly the same spot. How do all of those atoms stack up on each other? Do they push each other apart? Obviously not, because they are frozen in time. Does the entire rod instantly become frozen in time, without shrinking onto the surface of the black hole?

>>11120213
we have an artistic interpretation of a black hole but the artist just so happens to be a neural network

>>11120193
If we can build artificial black holes in the lab why can't we build inside a black hole in the real world?

>>11120243
We can't build artificial black holes.

>>11120225
What if a human were somehow able to survive a trip to the event horizon. Would they technically live on to to the end of the universe before finally succumbing to the gravitational force?

>>11120267
As you floated toward the horizon you would see the universe start to speed up, faster and faster. Right when you touched, the entire future of time would pass in a flash.

>>11120154
On a side note, what would an orbiting gravimeter read? The gravity field of the matter stuck on the horizon, or the one of whatever is inside?

Umm scitards

Explain this: if a spider can kill 100 humans with an amount of venom which costs 1 fly worth of energy to create, WHY DOESN'T EVERY CREATURE EVOLVE VENOM?

>>11120331
The stuff on the horizon would become perfectly flattened/hologramized against the black hole's surface, down to a one-atom thickness
But that shell of atoms would exert separate gravity I think|

It's also interesting to note that the gravity around a rotating black hole is rotational (the spacetime itself rotates.) It's called frame dragging

>>11120253
It's all over the news this last week also if you just Google sonic black holes, trapped acoustic phonons are a scalar

>>11120359
"acoustic black holes" (aka dumb holes) are not the black holes that we're talking about. They are an entirely different thing and also not really black holes. If you unplugged one it would let everything out. It also doesn't really contain light, it just puts it in a refractory medium and then contains that medium with acoustics.

It's a bit like shining a light between two mirrors and saying "Look, light cannot escape! I've made a black hole!"

>>11120373
It should produce observables that way if that's what a natural black hole does

>>11120232
A neural network is not a brain and one wasn’t used to make the first image of a black hole, which was done well before 2019 using better methods.

Black holes will very likely be replaced by some well-behaved objects when a sound quantum gravity theory is developed.

Anyway, some 10 years ago or so, there were articles on the so-called pre-Hawking radiation which indeed modeled the situation where a black hole started forming, but never really completed this process. So what appears to us as a black hole, isn't literally one really.

Black holes are fake news and the earth is flat. More news at bush did 9/11

>>11120154
it literally dilates itself

>>11120557
Quantum gravity is fanfiction with zero experimental validation.

>>11120154
>That means from any external perspective, it takes an infinite amount of time for an object to fall into the black hole. So, the object never actually gets eaten (from our perspective.)

Well, to other objects on an event horizon, the event horizon DOES form

So only people on an event horizon can see an event horizon

Therefore we are on an event horizon

>>11120633
High IQ post.

>>11120154
If time dilation becomes infinte for an object at the event horizon then it EFFECTIVELY drops out of the Universe; it EFFECTIVELY doesn't exist anymore.

>>11120887
It does exist, it's just frozen in time. It still exerts gravity for example.

>>11120154
>given hawking radiation seems to indicate all black holes will eventually dissolve in a finite amount of time, how can a black hole EVER exist?
Perhaps there is a Limit to it's effective mass beyond which it wraps spacetime around itself and effectively removes itself from the Universe -- perhaps to another Universe, either one that already exists, or perhaps that's the start of another Universe.

>>11120888
If it's """ frozen in time """ then it EFFECTIVELY doesn't exist.
How do you sense something for which no time passes? Rhetorical question, you don't.

>>11120154
>this shit again
fuck off

>>11120896
Because it distorts spacetime. Also, you can totally observe it through normal means. Remember, it never actually goes into the black hole. It isn't physically joined with the event horizon, it's one planck-length (or whatever the minimum distance is) above the event horizon. You could bounce a photon off it

>>11120905
>Because it distorts spacetime.
Uh-huh.
>Also, you can totally observe it through normal means.
{citation needed}
>Remember, it never actually goes into the black hole.
{citation needed}
>It isn't physically joined with the event horizon, it's one planck-length (or whatever the minimum distance is) above the event horizon. You could bounce a photon off it
{citation needed}
See, the problem with your troll-astrophysics here is that the mass of the singularity in question would never increase, ever, and we've already observed the gravitational effects of massive singularities. Therefore your whole """ idea """ (it's not even a theory) is a non-starter.
I'm not even a physicist and I can see that. You're really going to have to try harder to troll /sci/, OP.

>>11120925
>>Remember, it never actually goes into the black hole.
>{citation needed}

Time dilation becomes infinite near the black hole. From our reference point nothing ever enters a black hole, just gets frozen a planck-length above the surface

>>11120925
>See, the problem with your troll-astrophysics here is that the mass of the singularity in question would never increase, ever, and we've already observed the gravitational effects of massive singularities.

We have never conclusively observed an event horizon, or anything close. We know of very dense objects that people guess are black holes but don't actually know.

>>11120935
>We have never conclusively observed an event horizon, or anything close. We know of very dense objects that people guess are black holes but don't actually know.
Then this whole """ discussion """ is just hand-waving on the order of science fiction writing.
>>11120929
>Time dilation becomes infinite near the black hole. From our reference point nothing ever enters a black hole, just gets frozen a planck-length above the surface
Again: {citation needed}
Also: See above response to >>11120935

Between the two of you, you both manage to cancel each other out and make the entire subject moot and it all becomes science-fiction-esque wild theories.
Are at least one of you prospective fiction authors trying to work out the """ physics """ for some story you're trying to write? That would explain all this nonsense.

>>11120950
Everything in that post is true. We don't actually know anything is a black hole, and according to our understanding of physics, black holes should not exist.

>>11120955
But they do therefore none of the ideas presented in this thread can be considered valid.
Therefore: </thread>

>>11120959
>But they do
There is no actual hard evidence of a black hole's existence.

>>11120154
I haven't read all the answers but it looks like nearly all crackpots or well-meaning undergrad freshmen so let me give you a non pseud answer:

In the frame of the matter falling into the black hole, it does NOT take an infinite amount of time to cross the horizon. In fact, classically (i.e. general relativity without quantum mechanics) the matter falling in does not notice anything special about the horizon at all.

The time dilation is happening for bodies that are hovering near the horizon. The acceleration needed to stay a fixed distance from the black hole gets stronger and stronger as you approach it. So something hovering is accelerating very strongly, hence the time dilation.

Something in free fall going across the horizon is not accelerating, so there is not this time dilation effect.

>>11120179
Interesting thought. That would explain inflationary expansion through mass acquisition of the 5d black hole.
While suckling in mass, more particles end up on the event horizon or at least pass through. We would observe that.
Nevertheless, the idea is interesting.

>>11120987
>In the frame of the matter falling into the black hole, it does NOT take an infinite amount of time to cross the horizon
The OP says this. The OP asks why we (in OUR frame) observe black holes to exist, because from OUR frame, they should only be forming in an infinite amount of time from now.

>Something in free fall going across the horizon is not accelerating, so there is not this time dilation effect.
I have no idea what you're trying to say here. Space time is bent and eventually torn near the black hole, so yes, time dilation occurs regardless of whether or not you're accelerating near it.

>>11120987
You say that like op didn't disclaim that his reasoning only works for the external observer.

>>11121005
you could also explain away dark matter as matter that's outside the event horizon of a 4d black hole that's influencing gravity in on our 3d universe

Why exactly wasn't the singularity (from which came the Big Bang) just a black hole that never exploded? Why would it ever explode?

>>11121012
>>11121013

So then what exactly is the problem? I thought OP was trying to understand how an event horizon can physically form. The light that reaches us is not the same thing as the matter falling in.

>>11121012
>Space time is bent and eventually torn near the black hole

No, there is no 'tearing' at the event horizon, it is a perfectly finite curvature, and locally an object in free fall is as if it is in an inertial frame.

It actually takes the longest amount of proper time between any two spacetime points on its trajectory, so no there is no time dilation.

>>11121033
>So then what exactly is the problem? I thought OP was trying to understand how an event horizon can physically form.

I don't think you understand at all.
Black holes should not exist from our reference point. Since we are not inside the event horizon, it should take an infinite amount of time for a black hole to form (since it would take infinite time, from our perspective, for an event horizon to eat anything.)

From our perspective, when a star collapses in on itself, and it starts to become a black hole (as is alleged to happen) then it should take infinite time for the black hole to begin to form. But even then, paradoxically, due to hawking radiation it should dissolve before it forms (since hawking radiation will dissolve all black holes in a finite amount of time, yet it takes an infinite amount of time for a black hole to form)

>>11121037
Well, whatever the semantics of how you consider a non-light-escapable spacetime distortion should be called, it exists around a black hole and it dilates time infinitely. This is a basic part of relativity, Einstein commented on it himself.

>>11121038
Our perspective is not the same thing as the light reaching us. You need to understand this, this is the error you are making. It is true the light emitted from a body takes longer and longer to reach us as it approaches the black hole. But we can calculate precisely when it enters in any coordinate system.

>>11121043
It's not semantics, it is the difference between accelerating and non-accelerating, as I said in my post

>>11121048
>It is true the light emitted from a body takes longer and longer to reach us as it approaches the black hole. But we can calculate precisely when it enters in any coordinate system.
What? You can't calculate it all except to say that it will occur in an infinite amount of time from now.

>>11121052
No. You can calculate the trajectory for an object falling into the black hole, and calculate the finite proper time to fall in, in any coordinate system.

>>11120277
Leaving you with what? The answer always leads to one thing: the void. Like cold is without heat and darkness without light, the void, the absence of universe, is the ultimate stage. The purest non-existence conceivable. Even the act of imagining such a “place” is impossible.

https://arxiv.org/pdf/1601.00921v1.pdf

According to Stephen Hawking, everything that falls into a black hole gets imprinted onto the event horizon in the form of a "hologram". This contains all of the information about the object.

>>11120628
Touché. Consider me educated

>>11121063
>You can calculate the trajectory for an object falling into the black hole, and calculate the finite proper time to fall in, in any coordinate system.

That's nice, but it would still take an infinite time to us, aka you and me, the people who are not in black holes. And yet we seem to observe black holes (allegedly) which should not exist, since we have not yet arrived at an infinite amount of time from now.

>>11121080
We would not see a person fall in the black hole, true. But we would also not see a person hovering near the even horizon frozen. Is that what is bothering you?

The light gets more and more redshifted and less energetic, so even if in principle light would still be coming to us forever, the wavelength has been stretched well past the limits of any radio telescope, so we would not see it.

But again my main point is you are misunderstanding how time works in general relativity. Light reaching us is not a measure of physical time. Coordinate systems are not a measure of physical time. The only things that are physical are things like proper time and spacetime intervals.

>>11121102
It's not about seeing anything, it's about the fact that it literally would not occur from our perspective, and so black holes shouldn't exist (from our timeframe.)

The only people for whom black holes should exist are people who are, themselves, in an area of infinite time dilation (which can only be created by a black hole, which shouldn't exist for us... so... a paradoxical issue)

>>11121107
what if were in a black hole

or a simulation

>>11121102
>Light reaching us is not a measure of physical time
Time dilation is a measure of physical time, and at the event horizon it becomes infinite. So your comments about light do not make sense. This isn't about observation, it's about what's actually happening (namely: a black hole never forms, let alone eats anything, in a finite amount of time from our non-blackholed reference point)

>>11121107
Okay I'll stop discussing here. I'm not sure if the way you are using "perspective" is entirely clear to you yourself.

>>11121115
I think it's for the best, because you don't seem capable of understanding physics. Maybe you're black, or a hole.

>>11121117
what if we're all black holes

>>11121117
https://www.youtube.com/watch?v=oc1zGRUPztc

>>11121117
I have published papers using general relativity in Phys Rev D and have graded for a general relativity class at research level university.

>>11121114
Again, there is a difference between acceleration and not accelerating. That's what you aren't understanding. We don't assign a physical number "time dilation" at each point in spacetime.

>>11121125
>Again, there is a difference between acceleration and not accelerating. That's what you aren't understanding.
Yes, I really have no idea what you're trying to say here. Time dilation is time dilation. It doesn't matter if the object is moving up, down, left, right. It doesn't matter if it only does half an A-press. It doesn't matter if it does a somersault. It does EVERYTHING more slowly from the external perspective, and once it reaches infinite time dilation (at the event horizon) EVERY perspective besides the event horizon perspective becomes an external perspective, since infinite time dilation does not occur anywhere else besides an event horizon. So, unless you are on an event horizon, an event horizon never forms in a finite amount of time. And you can't be on an event horizon, because they don't form in finite without an event horizon.

>>11121137
>And you can't be on an event horizon, because they don't form in finite without an event horizon.
don't form in finite time*

>>11121137
>Time dilation is time dilation.
No you are simply wrong. The proper time depends on motion. That's the whole idea behind the twin paradox. One twin accelerates and experiences time dilation relative to the other twin that does not accelerate.

Show me the equation where you see time dilation at the event horizon. It will involve an object which is staying the same coordinate distance from the horizon, that object is *accelerating.* The acceleration is important.

>>11121149
>Show me the equation where you see time dilation at the event horizon
Why do objects which are not accelerating appear to slow down when approaching the event horizon, if not for time dilation?

>>11121118
Black hole hairs*
https://arxiv.org/pdf/1601.00921v1.pdf

>>11121165
Imagine a stationary non-accelerating observer sense light pulses at equal rates. If I am accelerating away from that observer, I receive the pulses at ever increasing rates.

This is just a sketch of a classical situation, but it is actually quite similar to what is going on with the black hole horizon.

Look up "rindler coordinates" which are a description of observers which are uniformly accelerating in special relativity. These observers also have a horizon which non accelerating objects slip past, beyond which they never receive any signals.

>>11120154
>Given this, how is it possible that we, in our current perspective, observe black holes to exist? How does a collapsing star ever form an event horizon when it should take an infinite amount of time for this to occur?
Pretty shocked nobody has mentioned this:
If you have compressing matter of more or less uniform density, you can imagine the Schwarzschild radius for the whole object as an imaginary sphere of fixed radius inside the compressing body. When the boundary of the compressing body enters within that radius, an event horizon is formed. This happens in finite external time. The material at the very boundary is questionable as to whether it passes inside in a finite time, but think about the material in the interior of the boundary: it was already within the schwarzschild radius when the threshold was reached, and the threshold is reached in finite time since time dilation does not become infinite until an event horizon is formed, so it must be inside a black hole proper.
You might ask why the threshold is reached for the whole body before the threshold is reached for some component section of the body: this is because Schwarzschild radius scales linearly with mass, while radius of a sphere of uniform density scales with the cube root of mass. Since the Schwarzschild radius grows faster than the containing radius as you consider more mass, the Schwarzschild radius for the whole mass is reached before that of any component part (assuming roughly uniform density)

>>11121226
>The material at the very boundary is questionable as to whether it passes inside in a finite time, but think about the material in the interior of the boundary: it was already within the schwarzschild radius when the threshold was reached, and the threshold is reached in finite time since time dilation does not become infinite until an event horizon is formed, so it must be inside a black hole proper.
It feels like this is just obfuscating the issue to try to hide that the material doesn't actually become an event horizon in finite time.
Also, even if you take it that black holes can form in finite time, how can they grow in finite time?

>>11120890
document.querySelector("#blackhole-123").remove()
If it becomes another universe then our garbage collector needs work, or it is still reachable

>>11120188

>>11121451
You're seeing a dense object with an accretion disk. It could be anything short of a black hole.

>>11121463
>observe matter acting how it's predicted to act near a black hole
>all measurements of the object's gravitational effect on other objects consistent with a black hole mass object

It acts like a black hole, it affects other objects like a black hole, it's more than likely a black hole.

>>11121485
Matter near a black hole acts the same way it acts near any dense object. It orbits and goes in.

>black holers
stopper reading

>black holers
stopped reading

>>11121226
Are you saying that if OP is right all black holes have the same size?
I'd say we should see it grow, since the energy-momentum content in that region observably increases.

>>11121588
He wasn't saying that at all

>>11120154
Well, we can't observe anything beyond the event horizon so existence of black holes is kinda inferred. Also, in GR, simultaneity is local so it is both valid to say that matter has not fallen into the black hole and that all matter has fallen into it for an observer on Earth. Now, if you observe that a black has already evaporated then you won't see any matter falling into it so you could only say that it already did.

>>11120154
Not sure what all these plebs are on about. But your answer is very simple.

The object would simply fall into the black hole normally, no magic. Time dilation only affects those in an extraordinary frame of reference (like travelling at, or close to, the speed of light), making it seem like everyone OUTSIDE of their frame of reference is experiencing time faster. The time dilation does not affect an external observer.

If a piece of matter travels at the speed of light, they experience no time. They would see the event horizon, then suddenly be destroyed from their perspective.

>>11121750
>If a piece of matter travels at the speed of light, they experience no time.
Matter can't travel at the speed of light and saying that something moving at the speed of light experiences no time is incorrect because you can't define an inertial frame of reference for anything moving at the speed of light.

>>11121756
>you can't define an inertial frame of reference for anything moving at the speed of light

This sounds like some arse-pulling

>>11121758
>>11121756
Is it that you can't define it because the matter would not be experiencing time?

>>11121760
You can't define it because in an inertial frame of reference the object is at rest but special relativity is based on the postulate that massless particles move at the speed of light in all inertial frames of references.

>>11121765
And why wouldn't light be moving at the speed of light in an object moving at the speed of light?

>>11121771
If something travels at the speed of light then it travels at the speed of light in all reference frames which means there is no frame where it is at rest.

>>11121750
You have no clue what you're talking about, even less than some of the other plebs

>>11121773
>>11121774
I was not aware of the whole "photons have no frame of reference" thing. Don't freak out. The explanation of why it is the case is circular, so I have difficulty understanding the reasoning behind that assumption.

>>11121750
>>11121774
Let me change a bit of that, the object is not moving at the speed of light.

>>11121463
>what is spectrometry
No it cant be anything short of a blackhole you absolute cretin. At best you could argue whatever it is behaves as a black hole which would make you a pedantic idiot.

>>11121784
It's not circular, photons have no frame of reference simply because they can't be at rest.
>>11121786
If an object is falling into black hole they will not notice anything when they cross the event horizon and nobody knows what happens when they hit the singularity.

>>11121796
Hey man, thanks for taking the time to explain this. I really do appreciate that.

>>11120154
Answer is the event horizon isn't static.
The black hole has radius r1 at time t1 before it eats the object and r2>r1 at t2 after. The event horizon only reaches r2 once the object is fully consumed so time dilation is finite at r2 and photons can still escape from r2 and reach the external observer in finite time up until t2.
The observer watching for infinite time will see the black hole just finish consuming the object.

>>11121451
I WANT TO BELIEVE.

>>11121029
nothing exploded during the big bang. space expanded into itself. yeah the name is shite.

What if higher dimensions existed before their lower counter parts and we are inside the 3rd last iteration, counting down into the 2nd last?

Doesn't that make sense? Chaos and the highest dimension are the same thing, which in turn devolved, thanks to singularities simplifying spacetime.

>>11121588
No, not at all. Again, the whole reaches threshold before the parts, so a larger clump of matter of roughly uniform density doesn't have to be compressed as much to reach threshold than a smaller clump.

>>11121911
How did space expand? Space should not be able to escape the gravity well either.

>>11122293
>Space should not be able to escape the gravity well either.
This sentence makes no sense.

>>11122297
Why would spacetime be able to spontaneously un-deform from its position within the the primordial singularity?

>>11122299
"Spontaneously" implies that the singularity existed for some time and we don't know that. We only know that the space has been constantly expanding since the Planch epoch and we don't even know what was before that.

>>11122310
Presumably the singularity existed (for a while) somewhere in the range of half the period of the existence of our universe (which most likely is part of a colossal periodic function)

>>11120177
Where can you read this essay?

>>11122848
>>11121073

>>11120154
It dialates RELATIVE to the observer.

If you observed something falling in then you cant ever see it fall in.

If you were the one falling in. Time flows like normal to you so you yourself would observe you crossing.

Relativity

>>11122987
Yes, that's what the OP says. The trouble is that we (the observers, who are not falling in) observe black holes to exist, when they should not (since from our perspective they shouldn't have formed yet.)

>>11121773
For something at c, that something is at rest and everything else is also at c.

>>11121796
>they can't be at rest
Isnt a photon eternally at rest from its own reference frame, while everything else seems to be at c?

>>11123281
>Isnt a photon eternally at rest from its own reference frame, while everything else seems to be at c?
No, photons just don't experience time at all.
They have no lifespan from their perspective

>>11123284
That's exactly what I said, though. They are ETERNALLY (timelessly) at REST (unmoving). They are simply a strand connecting two points in spacetime. It is us who observe them to seemingly move because we do experience time, they do not.
Again, how are photons not always at rest from their own inertial frame of reference?

>>11123292
Photons can never be at rest, ever. It's a law.

>>11123298
They are the only thing truly at rest, like everything that appears to us to move at c. Everything under c is subjected to relativity, the passage of time and the vastness of space. Things at c do not experience time, they don't move. They are at rest. You're the one subjected to motion. A photon is a line between two points that exists eternally.

>>11123321
This is nonsense.

>>11123333
Excuse me? You're saying that two mutually exclusive sentences are simultaneously true:
>Objects at c experience no time
>Objects at c possess absolute motion and thus experience time.
They cannot both be true. Special relativity tells us that objects at c:
>Experience no time due to infinite time dilation
>Experience no space due to infinite length contraction
>Are always an inert frame of reference
The conclusion is obvious. Objects at c are the only things truly at rest. They share the privileged reference frame of being inert and always avoid problems with the relativity of simultaneity, agreeing on every observation.

>>11123350
I stopped reading your posts because you don't know what you're talking about. Photons can't be stationary.

>>11123350
Lmao, the whole shtick of STR is that massless objects always travel at c in vacuum in all inertial reference frames, this obviously cant be true in a photon rest frame, therefore the notion only reminds you of your own assumptions. Stop being stupid.

>>11123355
You're suggesting they accelerate/decelerate by implying they don't have inertial reference frames, right? You either believe in SR along with time dilation and length contraction or you believe that photons actually 'move'. I understand the concept of spacetime is counterintuitive but denying SR because 'you don't get it' isn't valid.

>>11123358
How do you define an object at rest without invoking Newton's "absolute space" which is incompatible with modern physics? Objects at c are the absolute inertial FoR. It's much more correct to say that everything at c is literally motionless and the apparent passage of time is a macroscopic phenomenon experienced by massive particles, which have a different speed relative to c.

>>11120277
Wouldn't you disintegrate from being exposed to 100 trillion years of starlight at once?

>>11123370
>It's much more correct to say that everything at c is literally motionless and the apparent passage of time is a macroscopic phenomenon experienced by massive particles, which have a different speed relative to c.

no it isn't much more correct to say that, that entire sentence is you fellating yourself with your undergraduate physics degree

>>11123411
No, of course, you're right. Why present a counter argument? Let's all just crap all over special relativity.
From this point onwards, objects at c do experience time and space, they can accelerate and decelerate, if they appear to be at constant motion, it is exclusively due to external unseen forces, and absolute space and/or luminiferous aether are back on the menu in order to provide a reference for objects "at rest", which was what started all this. Are you going to tell me next that relativity is a jewish science?
Enjoy your optimum theories, your electric universe threads, feeding Tooker his kool aid, flat Earth cosmologies and endless IQ and "evolutionary advantage" threads.

>>11123442
could you tell me why you behave like this? it reeks of mental illness

are you made to feel mentally inferior in your day to day life? maybe your boss humiliates you and so you invent this persona in private where you're an epic physics genius?

>>11123449
No one here is an epic physics genius. How would you respond to people who cannot for the life of them pick up a book and explain why you're wrong and instead just fling insults at you other than derisive commentary? What do *you* get from acting this way, where when confronted with two mutually exclusive options you say both are true and insult anyone who attempts to tell you otherwise?

>>11120154

Actually, particles with mass are forbidden from having intervals of zero. Therefore, time does pass. However, by the time you cross the event horizon, time and space switch roles. Time becomes spacelike and space become timelike. You can move backwards and forwards in time, but space becomes linear and you always advance closer and closer to the singularity while doing so.

The amount of bullshit in this thread is amazing. It's almost like you guys don't understand basic general relativity but chose to comment anyway

>>11123494
>You can move backwards and forwards in time
No, when something crosses the horizon its trajectory is still timelike.

Your comment has a seed of truth in it which is why it is worse than complete nonsense. Someone reading this thread can't distinguish between your post and someone who actually knows what they are talking about. But what you said sounds cool. So they will repeat it in the next thread like this, altering it a little. It's like a bad game of telephone where the message gets stupider and stupider each time it's repeated.

>>11120154
Here’s a fun rule of thumb: if you’ve come to a conclusion that runs contrary to all of modern physics. You’re probably fucking wrong.

>>11123736
Hmm, nyes.
The earth must be the center of the universe

>>11120154
I can answer this anon.
>At a black hole's event horizon, time dilation becomes infinite. Relativity shows this.
true
>That means from any external perspective, it takes an infinite amount of time for an object to fall into the black hole.
also true
>So, the object never actually gets eaten (from our perspective.)
absolutely true
>Given this, how is it possible that we, in our current perspective, observe black holes to exist?
here is what is happening. We are not ever observing a black hole directly.
>How does a collapsing star ever form an event horizon when it should take an infinite amount of time for this to occur?
the event horizon can form in a finite amount of time. the time it take for ADDITIONAL matter to enter the black hole is infinite.
>given hawking radiation seems to indicate all black holes will eventually dissolve in a finite amount of time, how can a black hole EVER exist?
see above

>>11123785
Nope. Please just don't comment

>>11123788
>t absolutely assblasted
quite down, brainlet

>>11123785
>the event horizon can form in a finite amount of time. the time it take for ADDITIONAL matter to enter the black hole is infinite
If this was the case all black holes would be microscopic and would instantly evaporate due to hawking radiation.

>>11123805
wrong again kiddo.
as they lose mass due to hr they are still surrounded by more mass that hasnt yet accreted into the black hole. it has to make it thru all the mass until it finally dissolves

>>11123827
Hawking radiation only exists under certain untested assumptions of a quantum gravity theory. This is neither tested nor consensus. We don't know if it happens.

>>11123770
>infinite mass
>infinite density
>infinite time dilation

yea these are realistic things that could exist lol

>>11126509
no, but asymptotic limits are

>>11120157
kek

>>11121070
Not really, void exists all around us. Im sitting in it right now.

Void is by definition unobservable and unreal. Unreal is basically a synonym. That which does not exist.

Also once time ends, whatever is left is not void. Its only void if there is literally nothing left

Wouldn’t the people approaching the event horizon, just die of old age immediately, instead of seeing the universe speed up?

>>11126995
The people approaching the horizon would fall in.

>>11120191
As with most warp drives, time travel plots, etc., this involves negative energy densities and thus is scientifically worthless. GR places no restrictions on spacetime curvature; it just says the curvature follows the stress-energy tensor. By itself, it doesn't put restrictions on the stress-energy tensor. Those conditions come from other theories. So if you want to make something crazy happen in your GR model, it's always possible as long as you're willing to have impossible shit like negative energy happen inside your stress-energy tensor.

>>11126995
From their perspective they would just fall right in normally.
From anyone else's perspective they would flatten against the event horizon and remain there forever

>>11127047
>perspective
We went over this already didn't we? If you mean perspective as in the light you receive, you are correct it will take longer and longer to reach us. But there is no difference in perspective in terms of the physics.

>>11120154
einstein was a fraud. if that was true then there would be no black hole. it would seem to be covered in stuff and look like a giant perfectly round astroid / planetoid thats so massive it warps space significantly which has always been seen around a "black hole" . contrary to msm bullshit we have multiple pictures of a black hole. there is nothing in the middle. these things could in some cases be billions of years old and despite wandering have absorbed nothing?!?!

time dilation would on exist for a object moving super fast according to einsteins stuff. for any one not being sucked in the person or object being sucked in vanishes.

timedilation however cannot happen and not happen at the same time. this is where eisteins bullshit occurs. 2 results have to happen and thus timedilation is debunked within einsteins own stuff. a person would think it was a eternity but every one else sees them get sucked in. so time dilation isnt real its perception... so its nothing

>>11127053
Yes there is a perspective difference. Time is dilated heavily nearer to the blackhole, and infinitely at its edge.

>>11127076
Sort of. Proper time is dilated for an observer hovering a fixed distance outside a black hole compared to the global coordinate time. The global coordinate time is not something terribly physical. A coordinate system is something we choose in order to calculate with. No matter which you choose you calculate the same thing. That's why I take issue with the word 'perspective.' It makes it sound like it is real difference, but everyone calculates the person falling into the black hole does so in finite time.

Second big point:

This whole story about time dilation of hovering trajectories is completely different from a free falling trajectory. The slowing down of the light you see is *not* related to the time dilation of a hovering body. Time dilation is not a property of the event horizon itself. It depends on the trajectory.

>>11127019
Yes, but they would perish very quickly, since they age rapidly(assuming all other deadly issues are dealt with), right?
>>11127047
From the perspective of others, would the person eternally falling seem to age? For example, wrinkles, gray hair, etc. Or would they look the same age forever to them?

>>11127111
No, where is this age very rapidly thing coming from? I've seen others on here say that too. That's not even misunderstood popscience like the infinite time dilation thing is. I think it's just a myth that gets repeated in these threads

>>11127111
>From the perspective of others, would the person eternally falling seem to age? For example, wrinkles, gray hair, etc. Or would they look the same age forever to them?
They would seem to not be moving through time. So, the exact opposite

>>11120154
time dilation becomes infinite in the coordinate system used by an external observer, you can construct other coordinate systems where this doesn't happen; this is analogous to walking through an infinite number of timezones at the north pole
trying to use this to conclude black holes can't exist is retarded

>>11127351
>time dilation becomes infinite in the coordinate system
dilate

>>11127714
how about instead of spouting buzzwords like a brainless fungus you go read about Gullstrand–Painleve coordinates and learn something new

>>11126536
Show me a picture of an object that exist that has a asymptotic limit

>>11120154
The other day I prepped a slide. Forgot what it was, I didn’t use staining. Anyways in DF I realized how they could theorized this. I think I use a pass blue diffuser. You could see stars, nebulas, galaxies but most all blackholes. Black holes I assume are substantiated by theories of diffraction limits. As to the nature of black holes one can only truly theorize. But not necessarily prove until we send some vessel. But from our space location they could be a phenomena sort of like a mirage a turn in space caused by the nature of gasses. There are limitations. But a diffraction limit. As to how we surpass it who knows? Super resolution has recently become a real thing. And as that expands perhaps the nature of space as well. Since telescopes and microscopes share similar qualities. People are always trying to surpass it. They have their theories. Or don’t talk about it because it has economic value. The idea is we are limited by light and wavelength. Some wavelengths are harmful to us. Anyways but perhaps there is a second diffraction limit with another physical law. Even though diffraction limit is defined as space visible distance between two points. Or the limit at which you can see two close points as two and not one. I think it’s common opinion that it set the limit of the visible. The idea is there is something there but you can’t see beyond it through straight conventional engineering.

>>11120179
Turtles all the way up? That's bullshit but I believe it

>>11120225
the rod gets smushed into a 2D disk that starts redshifting

>>11129870
hawking says it would get compressed down to an atomic stack of photons that he calls "hairs"

https://arxiv.org/pdf/1601.00921v1.pdf

>>11120225
>The first atomic layer of the rod hits the event horizon and freezes.
It passes through the horizon

>Now what happens to the other 99.999999% of the rod?
It passes through the horizon

>>11129873
>atomic stack of photons
Yeah I'm sure you fully understood that paper...

>>11129913
Not to us.

>>11129916
Yes to us. I have explained this previously in the thread

>>11129921

>>11129929
Serious question, why do you think you are right and I am wrong? Do you know what a Schwarzschild metric is?

>>11129934
(Heavy's voice) NO!

>>11121226
Thank you very much for the only actual answer in this bogus thread.

>>11127111
>Yes, but they would perish very quickly, since they age rapidly
What? No. A person who falls in, to an outside observer, seems to hover just above the event horizon, completely frozen and inanimate, and they sinply become dimmer, redder, and darker until they are indistinguishable from the environment.

>>11120167
Anon watched interstellar once

Hold on, this is a very important shitpost.
So what you’re saying is... I could use black holes to send text messages to the past?

>>11130455
Season 3 when?

>>11130455
I'd send a message down her black hole, if you know what I mean.

>>11130306
I'm sorry but he is not correct when he says "The material at the very boundary is questionable as to whether it passes inside in a finite time." I am an actual publishing physicist, and it is not questionable at all if you have taken a general relativity 101 course. It passes through in a finite time, period.

>>11131603
>argument from authority
This doesn't work in anonymous image forums, Anon-kun.
Either explain or shut it.

>>11131629
>explain

This is me
>>11127096

>>11131633
Seems like you're wrong:
https://www.researchgate.net/post/Can_black_hole_singularities_even_form_in_finite_time
This is an open issue.

>>11131672
Notice how he says "if I understand correctly"? He doesn't. That's why he's asking a question.

Do you know what a metric is? I can tell you how to do a simple calculation (that appears in every textbook) to show that a radial trajectory falling in does so in finite proper time.

>>11131681
Yes. Go ahead.

>>11131681
>proper time
We're not talking about proper time here...
Of course it passes through in finite proper time. The question here is regarding an outside observer, not a clock following the worldline of something falling inside.

>>11131696
Ignoring the angular part and using natural units the Schwartzschild metric is
[math]-\left(1-\frac{2M}{r}\right)dt^2+\left(1-\frac{2M}{r}\right)^{-1}dr^2[/math]
If you are hovering with no change in r, this implies there is indeed a time dilation factor [math]1-2M/r[\math] with respect to the coordinate time t. And this time dilation factor blows up at the horizon [math]r=2M[\math].

But this divergence is just due to the fact that you have to accelerate more and more to stay at fixed r as you get close to the horizon. If you are freely falling, or otherwise moving in, then the positive [math]dr^2[\math] term will come in too.

cont..

>>11131710
Of course we are talking about proper time. The coordinate time is not physical. I can choose any coordinates I want. It is not some difference of "perspective." Any observer can choose any coordinates no matter where you are.

This is a basic thing to understand about general relativity, so if you are stuck on this point there's no point writing up the rest of the calculation.

>>11120332

>>11120154
1) Its only infinite using certain coordinate systems
2) Not every photon crosses an event horizon
3) They are on the very fringe of current understanding

>>11131744
The whole point of the OP is asking about external time. And, having learned GR 101, you should know that the time coordinate of the Schwarzschild metric corresponds to the proper time of an infinitely distant observer (or, to a good approximation, proper time of a sufficiently distant observer). You'll probably want to go off on the technicality that coordinate time of an event from a nonlocal perspective isn't as physically meaningful as the proper time, but again this is missing the point of the OP. OP is asking whether, in any meaningful sense, event horizons can form in finite external time, not infalling time.

>>11131982
My proper time out at infinity is physical. I can measure it with a clock. The light I receive out at infinity from an observer falling through the horizon is physical. It is what I observe. And yes I never see them fall through the horizon, because of course no light beyond the horizon can reach me (btw, this has nothing to do with infinite time dilation factors, try calculating the rate at which you receive pulses).

The Schwartzchild coordinate time is not physical. Out at infinity I have no direct access to what's going on at the horizon at a spatially different location. Out at infinity, I can slice up 4d spacetime into different spatial slices in all sorts of ways, and none of them are more closely related to me as an observer as any other. My clock only measures at the location I am out at infinity.

>>11120157

henlo yes this is dado?
can i buy plutonium or energy drinks please?

>>11132024
stop LARPing

>>11131744
>"published physicist" so dense, his Schwarzschild radius lies outside his body

Is there even a meaningful difference for a distant observer between a black hole and an "almost" block hole? To me, OPs question seem to be of a kind that stems from an intuitive understanding of space and time with an absolute time or something.

>>11133769
I guess you'd be able to detect heavily redshifted light from the almost-black-hole

>>11120154
This isn't how black holes work, you clearly have no fucking idea what you're talking about. An Event Horizon forms through gravity, it's just the boundary at which the escape velocity of an object is greater than the speed of light. From an observer's point of view, an object that falls through the Event Horizon becomes increasingly red-shifted and then fades completely. Event Horizon doesn't stop time or any magical bullshit like that, you obviously don't know a rat's ass about how light works.

Holy shit, fucking teenagers thinking they understand astro physics, it's so fucking grating.

>>11135417
>From an observer's point of view, an object that falls through the Event Horizon becomes increasingly red-shifted and then fades completely
wrong

>>11135418
it's not wrong

https://www.youtube.com/watch?v=mht-1c4wc0Q&list=PLsPUh22kYmNBl4h0i4mI5zDflExXJMo_x&t=0s

>>11129800
>Turtles all the way up?
What if it's more than turtles up there?
We have space and time. What if there are more fundamental elements other than just space/time that we can't even fathom because they don't exist for us?

2 spacial + 0 temporal
3 spacial + 1 temporal + 0 ???
4 spacial + 2 temporal + 1 ??? + 0 ???
5 spacial + 3 temporal + 2 ??? + 1 ??? + 0 ???

How far up do you have to go till one of those question marks becomes something really weird like dimensions of pure consciousness and thought?

>>11120154

Regarding the life of a BH
t = mc^2/L where M is the mass of the BH, c is the speed of light and L is the hawking luminosity. BH's can form from Neutron stars that exceed 3 stellar masses or significantly huge stars. They appropriate mass through accretion. Though they loose mass they also gain, but assuming their current mass is all converted the time scale is mass dependant and for Super massive black holes the lifetime exceeds the current estimate for the lifetime of the universe.

Put some numbers in and answer your own question.

Also Black holes are a misnomer as the radius is really the event horizon, black holes have no size being a singularity (i.e divide by zero) . They defy the laws of Physics.

>>11135417
You didn't even read a few posts in the thread before writing this nonsense.

>>11135858
Both things you claim aren't part of current theories. Hawking radiation is a consequence of quantum corrections to GR we have no idea about whether they are accurate or not.
Same is true for what's inside the event horizon. Don't act like it's settled science.

>>11135945

I know Hawking radiation is a result of quantum corrections, I didn't fancy getting into Heisenberg uncertainty principle (assuming that was overcomplicating things). Since Quantum theory itself is a 'It works, we don't know how, but it does' answer from Physicists in general we can't be certain really.

I also know it's not settled, everything we know are best theories, which are based on observations and conjectures, not "Hey what if...". Theories change when we make new discoveries, I know what we know is not absolute. It's bound to change.

It was just a general idea/approximation for the chaps question.

>>11136002
>I didn't fancy getting into Heisenberg uncertainty principle
The jig is up my friend. We all know you have no clue what you're talking about

>>11120154
separate the 2 entities.

>>11136034
You're right in saying I've no clue what I'm on about. Frankly I have no clue with Physics whatsoever..

My lecturer explained it as uncertainty in energy, ∆E∆t=ℏ/2
Some elements are ejected from the black hole at the boundary of the event horizon due to quantum tunnelling (or something like that I probably misinterpreted?), hence the 'Hawking' radiation.

Sorry fella I'm just going of what I was taught in class and I probably misheard half. I do trust my lecturer as he is an astrophysicist and part of the team who caught a glimpse of two merging black holes (Grav waves). He is hand 'wavey' though so there are doubts!

Care to elaborate on what you may know? I'm not baiting you I'm genuinely interested, always open to learn! (Or try to..)

>>11136157
Your lecturer was telling you an incorrect pop-science explanation. Some people try to explain to laymen that there are virtual particles that can exist for a brief time, and one falls into the black hole, and the other escapes. This is really terribly misleading, and you should just forget it.

Hawking radiation is difficult to understand, you have to understand quantum field theory for it to make any sense. I'm a physics phd student and do understand Hawking radiation for an eternal black hole. But for an actual changing black hole that forms and evaporates there are all sorts of open questions.

>>11136174
That's pretty much the explanation he gave followed by 'something like that'. He is hand wavey and I took it with a grain of salt. Like I say it's what I was taught I can say I get it.

I can't say I know more beyond what I've been shown and my uni is pretty shit having given half a unit of introductory QM, I'll add it to the reading list I may never get round to looking at.. Good luck with the PHD anon!

>>11136190
Can't say I get it*

>>11120154
>Given this, how is it possible that we, in our current perspective, observe black holes to exist?

When he event horizon first comes into existence, it already has some volume. Then it expands to consume various things around it.

Also, it is possible for the mass of objects outside the event horizon to contribute to the overall mass of the system, thus making the event horizon larger and being consumed. Things inside the event horizon are actually traveling backwards in time - but in a way that can never affect the past of our universe.

>>11136244
What you're saying makes no sense whatsoever. It can only expand by consuming things, and you are saying it consumes things by expanding. This is circular logic. It has to consume first, and it can't consume.

>>11136244
>Things inside the event horizon are actually traveling backwards in time
i've seen a lot of extremely stupid people say very stupid things authoritatively on /sci/, but this is probably the worst

>>11120154
Thinking infinity is a number is stupid.

>>11120154
Time is just fabric of the universe.

Black hole is obviously place, where this thing ends.

Welcome to the end of time.

You are literally saying it takes no time there until finish of universe.

>>11136258
thinking infinite things don't exist because you're a puny human who can't comprehend it is more stupid

>>11136251
I hate to say it, but that post and this thread is exactly why an anonymous unmoderated message board doesn't work for discussing science.

>>11120179
It's literally a 4D convolution head calculating matrix out of our 4D reality in this simulation.

>>11120191
Literally universe runs out of time while you are there for nanosecond, if infinite.

>>11136250
> Totally misstates what I said
> What you're saying makes no sense whatsoever.

>>11136251
That is what it means for a time cone to be inverted. You can't escape the event horizon because merely standing still equals moving faster then light. So what happens when light, moving at light speed, enters the event horizon?

>11136282
retarded LARPer

post hidden

1. The size of an event horizon is determined by the black hole's mass.

2. A black hole's mass includes the mass of things not yet inside the event horizon.

T. An object NEAR the event horizon can cause the event horizon to expand, thus being consumed.

>>11136305
>2. A black hole's mass includes the mass of things not yet inside the event horizon.
no, retard

>T. An object NEAR the event horizon can cause the event horizon to expand, thus being consumed.
no, retard

>>11136269
As it is obvious, by all the shit you're telling about black holes, it's no longery dynamic system once it's infinite.

>>11136308

How much of the Sun's mass is outside of an event horizon? All of it. But it still counts as the "mass of the sun."

Imagine a planet orbiting a binary star system. To calculate the planet's orbit, you would simply add the mass of the two stars, and that would give you the gravity affecting the planet. It is the same with mass in close orbit around a black hole.

>>11136335
retard

>>11136356
>retard
Retard.

>>11126866
>Also once time ends, whatever is left is not void
How do you know this?

>>11120157
This is the funniest response I’ve ever read to anything.

>>11120154
>can a black hole EVER exist? (since the time it takes for a black hole to form should be infinite, which is less than the time it takes for them to dissolve.)

The event horizon comes into existence with mass already inside it.

>>11138950
that's not how it works

Maybe:

1) Matter becomes compressed asymptotically close against the event horizon
2) Quantum fluctuations insert some of the matter into the black hole

And similarly, right before a black hole *forms*, like the instant before the schwarzschild radius is reached, a few particles fluctuate into the center mass of the "black hole candidate" and it collapses into an event horizon

>>11138952
>that's not how it works

You have a better theory? Or just blind contrarian?

>>11138986
what you're saying violates causality lol
its wrong, no need to explain further