FAQs + Go to ground.news/floathead to stay fully informed and access reliable information. Subscribe through my link to get 40% off unlimited access this month only. FAQs 1) Shouldn't the speed of light be 300,000 km/s and not km/hr? Yes, sorry! 2) You mean we can't OBSERVE things entering BH, right? The title is a click bait, right? No! There are no events beyond the event horizon. So, from the perspective of an observer outside the BH, the event of something entering a black hole cannot happen. So, the last ever event is reaching the event horizon. Nothing ever happens beyond that. 3) Wait, if nothing ever enters a black hole, then how do black holes grow? How do they 'suck' stars and stuff? I am glad you asked. Imagine a star of 1 solar mass falling into a 1 solar mass black hole. From the outside perspective, we get a black hole of 1 solar mass with 1 solar mass worth of stuff almost frozen near the horizon. This creates practically the same spacetime curvature outside as a 2 solar mass blackhole and hence for all practical purposes, the black hole has grown! As the mass approaches the BH, its event horizon would grow. So, the 1 solar mass BH + 1 solar mass stuff near the event horizon will also have a larger event horizon pretty much the same as what a 2 solar mass BH would have. And there you have it, for all practical purposes, we could model this as a new BH of 2 solar mass even though nothing ever crosses the horizon! 4) So, where is all the stuff? Close to the event horizon or at the singularity? Yes. 5) What about Hawking radiation and black evaporation? That's beyond the scope of this explanation. This explanation is for static black holes. (static event horizon that always existed). Yes, these are idealised BHs. Any more questions?

@VertauePhysik

Ай бұрын

🗣️🗣️Wait so how does NASA take pictures of stars entering the black hole.Can we not think as black holes as Wormhole that bends the fabric of space time so much that you go to an another universe, my whole life of 9 years has been a lie about black holes😮. Btw thank you sir, you make this tensor calculus and general relativity so simple👏 And!! What about the swazchild radi!!!!!????!!??!!!

@classicalmechanic8914

Ай бұрын

Two way speed of light is 300,000 km/s. How do you explain quasars or blazars if one way speed of light is 300,000 km/s?

@whykoks

Ай бұрын

Would the Hawkins radiation able to travel any far from the event horizon?

@thewatcher14

Ай бұрын

:)

@se7964

Ай бұрын

This is video is so wrong. An observer’s PROPER time does not stop at the event horizon, and an observer can pass through the horizon quite readily. It only APPEARS time stops there due to light getting trapped near the horizon. A basic reading of GR textbook will tell you how to calculate how much proper time it takes to fall into a black hole - and that time is quite finite. I’d suggest watching ScienceClic’s video for a much better breakdown of the problem.

"... but Einstein..? Well Mahesh..!" Several of your videos in, I must tell you I find them immensely entertaining, and I learn so much. Many thanx for your work!

@authenticallysuperficial9874

Ай бұрын

This format is great

@nagualdesign

Ай бұрын

You learned nothing from this video since it is wrong. If you did 'learn' anything then you've been miseducated.

@DmitryTomat

22 күн бұрын

I am looking forward to the video in which Mahesh intuitively, understandably, explains how to move back in time, because the person who interviews Einstein and Newton for each of his videos probably knows this

I had to harness the power of love to solve spacetime to pause that screen on time.

@gadelavega

Ай бұрын

Unpopular opinion: such a stupid movie

@zaidbhaiboss

Ай бұрын

@@gadelavega bro thinks this is reddit

@alexejfrohlich5869

Ай бұрын

i even had to go back in time to actually read it!!!

@aschapm

Ай бұрын

.25x and precision scrubbing

@APaleDot

Ай бұрын

If you are on PC you can use the keys to go frame by frame.

A few years ago (using a different account) I had this argument with a large science channel. They proposed the idea that, theoretically, if you could go fast enough, you could get out of a black hole. But I said there was no speed that'd get you out, because once inside, every direction you choose leads to the singularity. I told them that they were actually saying (without realizing it), "You can escape a black hole by traveling back in time," which is absurd. Additionally, if you read enough about black holes, you'll eventually encounter the concept that once you cross the event horizon, space and time "flip," meaning space _becomes_ time, and time _becomes_ space. Even understanding it, that still sounds like gibberish in my head. But your animation illustrates that concept perfectly. Everything outside the event horizon is in the past, thus space and time "flipped."

@juliavixen176

Ай бұрын

That "flip" is mathematically the same thing as multiplying by the imaginary unit. It's to get past the log(0) curvature at the event horizon by using the complex logarithm instead.

@Ladeenian

Ай бұрын

Actually, it's only the radial direction into the black hole that gets swapped with time. So this means that the particles of an unlucky astronaut get accelerated into the extreme future, & arrive at the moment & location of the black hole just milliseconds before its final burst of Hawking radiation.

@rafaelgonzalez4175

Ай бұрын

Good thing you made an account to return so I can debate this theory. I'll start with Black holes. Before we get far let me say this. Not all elements are charted. Science can claim they have the protein count to determine the next element or uncharted element but it is not published and the Periodic chart is not complete. With that you have to take into consideration Life force. Our very souls. Science calls it consciousness. It is energy. Undetermined, unclassified energy. Now you have to look at the equation. Unknown energy. Unknown elements, unknown forces of a Black hole. It is easily imagined a Black hole is consuming something. It is easier to imagine, that something is not visible. It is also imaginable that, the something not visible, has not been identified. Then you can say a Black hole has an escape potential. The particle of the element that is not visible nor identifiable must still exist. All energy going toward the Black hole does not enter the Black hole. Yet the Black hole is showing that energy is going towards it. Energy builds on the outside of the Black hole. What is going in? Something has to be pulling the energy if not gravity. And it is not Gravity. Because one thing is certain, gravity has no effect on energy. Now I have to deduct time from space. Time is not relative to space. Today is today on the other side of the galaxy. The Galaxy is moving with the universe. As the Solar system is moving with the galaxy, as the earth is moving with the solar system as we are moving with the Earth. Today is today on Mars. Today is today on Mercury. Today is today in the Andromeda Galaxy. Until it becomes tomorrow.

@masonkoful

Ай бұрын

Flip or merge into one?

@kylelochlann5053

Ай бұрын

The is no physical flipping of space and time. What happens is that in a particular choice of coordinates, e.g. Schwarzschild-Droste, the temporal and radial terms in the metric switch algebraic sign.

Alright we want a 2 hour special on black holes. This left me unsatisfied 😂. Not because it wasnt good but i have more questions than answers now.

18:12 I was missing that outro so much. Even if matpat wasn't the one doing it, at least someone did.

@Mahesh_Shenoy

Ай бұрын

The legacy lives on!

Probably a stupid question, but; If, from my perspective, nothing ever enters a black hole, how can it gain mass? Or, for that matter, have mass in the first place?

@marveljustice

Ай бұрын

A doubt that's troubling me tooo.! !!

Ай бұрын

That is exactly what I was thinking when I was watching him say this.

@korakatk318

Ай бұрын

I tried looking it up but I couldn’t find a convincing answer

@timisi

Ай бұрын

Those things will be stuck at the event horizon from our outside pov. The whole thing (black hole + stuff being stuck at the event horizon) will be practically a solid sphere and from outside there will be no gravitational difference between that stuff being on the "surface" or inside the black hole, so all of those things entering from their pov will also add to the black holes mass from outside pov. Of course this geometrical approximation changes inside the black hole, but from that perspective things can enter

@nicksgmail9663

Ай бұрын

The way that I understand it is using e=mc^2. We know that mass is just energy confined in space, and binding energy makes up most of the mass. Since it can’t possibly escape the black hole, then it’s effectively contained in the space just like all the other mass/energy. So it is effectively adding to its mass by going back to what mass actually is; just energy contained in a space.

You are my favourite youtuber... You have made physics really interesting and thought driven... Kudos to you.

From our point of view, Cooper never crosses the event horizon; it will always look like he's stuck there. But the black hole itself does not exist for an infinite amount of time: because of Hawking radiation, it slowly evaporates and the event horizon slowly recedes. So we should see Cooper tracking this recession, getting closer and closer to the center, but never crossing the shrinking horizon. Eventually, the event horizon will collapse into a point, and the black hole will dissipate, and we will have never observed Cooper crossing it. With nothing holding him back, we will just see him go on his merry way to the next adventure. Now, what's wrong with this picture?

@juliavixen176

Ай бұрын

(Cooper can not see the Hawking radiation while in free-fall.) You want to know what Cooper is experiencing... so you want to use a coordinate system based on Cooper's proper time (and no one else's clock)... that means you're using Gullstrand-Painlevé Coordinates, which are continuous all the way to the physical singularly at the black hole's center of mass. Cooper will arrive in a very breif amount of time (depending on the mass of the black hole, a few fractions of a second to a few days on Cooper's own clock.) The event horizon is empty space. There is nothing there in Gullstrand-Painlevé coordinates.

@vanosaur

Ай бұрын

The question of what Cooper experiences is indeed very interesting (and I have thoughts about that), but what I was really curious about is how to resolve the contradiction I see between the assertions that, from our point of view, (a) Cooper never crosses the event horizon, and (b) the lifetime of the black hole itself is finite. This would seem to suggest that Cooper outlasts the black hole without ever having crossed its event horizon.

@knutfranke6846

Ай бұрын

​@@vanosaurAs someone else pointed out in another thread, Cooper and the black hole together have an event horizon that's slightly larger than that of the original black hole. In contrast to the original horizon, he can pass the combined event horizon in finite time.

@fuxpremier

Ай бұрын

Thanks for this. I've been saying that for years and never found a good explanation to contradict this idea. The logical conclusion is that the black hole itself can never form. Using a coordinate system relative to the black hole is irrelevant: if the black hole is never completed, this coordinate system is not in true free fall. There are no black holes, there are no singularities, the black hole is a limit behavior of spacetime that can't be reached due to quantum fluctuations. What we observe are quadi-black holes that will never complete their collapse.

@donutwindy

Ай бұрын

From our perspective I don't think we ever see anything happen. The event horizon cannot shrink from our point of view because it would take time to do so and there is no time. From our point of view there is no singularity either (whatever that actually means as matter cannot exist in a state that compact) and I would think Hawking radiation (that I have too many problems with) may only apply in coopers/black hole's frame of reference as cooper and the horizon are pretty much stuck in our frame. Now from its frame, perhaps its already 'evaporated', but I don't see how we'd ever see that. Cooper is dead but not, black hole is there but not. Makes perfect sense.

In black holes, spacetime is bent so much that all paths lead towards the center so there is no direction out.

@kylelochlann5053

Ай бұрын

All causal curves lead deeper into the interior. There are space-like that lead to the exterior.

- So, I fell into a black hole. - Well, that sucks! - No, it doesn't! Watch this cool video for a better explanation while I lurk over there on the event horizon. - Won't you cross it? - Well, it's matter of perspective... (Okay, I'm leaving)

I'm 37 years old, I am a passionate about science and physics, and I Ve saw so many videos and documentary's in my life about black holes, but this is the first time I've understand how they "work" ... And it was so simple and easy... Great job!

Great presentation, contagious enthusiasm and positivity - your videos are just perfect for fridays! Thank you for this.

Hi mahesh, so i was trying to understand this and i think i have an explanation for some of the questions in the comments but i could be wrong. If anyone wants to correct me go ahead. Heres what I understand 1. From an outside perspective his time is slowing down because of time dilation. This means that he cannot move because his time dilation is approaching infinity so his time approaches 0. 2. From his perspective time is passing normally but his length is getting contracted so everything around him is getting longer. To the point where 1 meter for him is 1/2 a meter for us then 1/4 meter for us and then keeps contracting to infinity until he reaches an asymptote. 3. If #2 is true then everything that enters a black hole reaches an asymptote in (space time) and it can never go past it. Therefore nothing really enters but its always stuck in its asymptote. But if a new particle enters a black hole it will get stuck in an asymptote that is slightly farther away than the last one so it will expand the black hole and this is how black holes grow. 4. Light does not escape because the length contraction expands faster the speed of light. This means for example that after the event horizon light will have to travel more than a lightyear in 1 year to escape. As i understand this means that light will also reach an asymptote in space time so it will remain stuck in the asymptote. 5. If the space time asymptote is true then. That means space time is not continuous in those points. Im guessing this is what people mean when they say there is a hole in the fabric of space time. 6. Also where would this hole be because if each new particle falls in a new asymptote then where is the rip in space time, is it just a lot of rips inside of it? Or does it not matter and the only one that matters is the farthestmost asymptote that is the one that starts the discontinuity from our space time. Sorry for rambling but if anyone has any thoughts on this please let me know. Edit: fixed some stuff in the comments.

@Hegonauta

Ай бұрын

Thanks for this. was about to ask how does it grow, or how do we see two black holes merge. but with your comment made me realize is just how we perceive it from our perspective

@timisi

Ай бұрын

I think there is only one rip / hole / discontinuity and it's the singularity. There are different paths towards it though (for example from every point inside the event horizon there is one individual path towards the singularity for every velocity someting has at this point)

@arturodeliz9416

Ай бұрын

@@timisioh ok, i think i understand how to fix my initial problem. My logic was if you have a small black hole and something falls in it will remain “stuck” at a certain distance from the event horizon. My guess was the middle. But lets say that black hole grows to the size of the largest black hole. Things that fall into it will never meet what fell into it when it was smaller. So i thought maybe it formed “asymptote layers” but if two particles fall at very slightly and different times, their distance would increase exponentially because of length contraction. So while the first object in the black hole is infinitely far away it is still measurably far away so it is continuous. And then there is only one discontinuity in the center. This means they do form layers but only one asymptote. Also mass increases so space time warp increases therefore event horizon increases. Is this what you mean?

@timisi

Ай бұрын

@@arturodeliz9416 I think essentially yes that's what I meant, but I didn't think about details. You talk about 2 objects entering one after onother and that they cannot meet. Why not? If they are not just projectiles rather then living things or technology with the abilitity to accelerate, I don't see a problem with meet-ups. Even the 'thing' that entered first could try to move away from the singularity - it wouldn't succeed but I think it'd still switch the geodesic / path to singularity / asymptote layer and why wouldn't it be possible to reach the one of the object entering second? Maybe I just didn't think about it for long enaugh

@timisi

Ай бұрын

@@arturodeliz9416 And I cannot imagine that physicists wouldn't call a space between two objects with infinite distance continuous (referring your 'measurably infinite distinace') so if I also state that there is only one discontinuity then those two onjects are not infinitely far away from each other and they could meet with acceleration. I have another picture in my head: Maybe you heared about the idea of white holes being connected to black holes so maybe they build a worm hole between two universes or just the idea of a pocket universe being inside a black hole. I don't want to suggest that those are the case but It gives me a new perspective on two things passing event horizon at slightly different times. Just as for outside observers Cooper slows down and never reaches the event horizon Cooper also can never reach the event horizon when already inside of it - every path gos away from it so he had to accelerate infinitley to get there again. So the inside isn't that different from the outside! The singularity is just a random point infinitely far away and it's somehow Coopers future but maybe in the outside world there i something simular too but with time and space being swapped. What I want to say is that it's not that obvious for me why two things inside the event horizon couldn't just meet each other if they wanted to and had the ability to accelerate in any direction (wich of course point to the singularity / future)

This channel never lets me down! Once again an amazing video

@b.s.7693

Ай бұрын

Rick Astley also never lets you down!

It should be 300.000 km/s in the Beginning of the Video ;-)

@Mahesh_Shenoy

Ай бұрын

Ahhh.. Damn it! Thanks for pointing it out.

@krakrikro

Ай бұрын

@@Mahesh_Shenoy No worries! Nice video as allways! You have a great way of making things, that are hard to understand, understandable! .-)

@b.s.7693

Ай бұрын

These are the mistakes every creator hates like hell...

@robertgough161

Ай бұрын

299,792,458 meters per second

@insylem

Ай бұрын

I think it was intentional to boost engagement. It's a common tactic online. Post incorrect Information and engagement goes Up

I could not stop myself by watching this video because I was asking the same questions and giving same arguments to everyone but no one was getting convinced and I was thinking why they don't understand my words.

@albertjewell1963

Ай бұрын

I think he explained everything very well. But the title of this video makes it more confusing than it needs to be. I think if it was titled "Why can't we OBSERVE anything entering a black hole in the first place", it would remove some ambiguity.

@zaidbhaiboss

Ай бұрын

@@albertjewell1963 It's not about observing. Nothing can objectively enter a black hole in your frame of reference except you :)

Thanks Mahesh, I’ve been struggling with the concept of space and time reversing inside a black hole, this was a very helpful explanation 👍

I love your channel so much that I pre liking and commenting. I already know I am going to love the video.❤

I love learning from your videos. The way you explain it is easier to understand. I love your enthusiasm when you are explaining, it’s great & refreshing.

You're a fantastic teacher. I've been hitting this material hard without formal schooling for about 6 years and you really knocked me into the next field ;)

Good job on your narrative approach to these concepts, im loving it.

@nagualdesign

Ай бұрын

You've spelled _naïve_ wrong.

This is a really nice explanation, you're easily my favourite teacher in GR, that enthusiasm is contagious :) Two things I still don't understand though, in the case of a real-world scenario: if an ouside observer 'sees' something fall into the black hole, it gets frozen in time near the event horizon, but if it's a feeding BH, it grows, so after some finite amount of time, that infalling object would be behind the event horizon from the outside perspective as the horizon would move past the point where that object was. And if Hawking radiation is real, then from the perspective of an infalling observer the BH would 'evaporate under them' as they keep approaching the event horizon, because if the BH evaporates in a finite time, it must happen before the infalling observer reaches the horizon.

@linuxp00

Ай бұрын

It's just an after image, their last photon streams keep getting redder and redder, until it's invisible, going to the radiowave spectrum. If the BH keeps growing at time, foremost we wouldn't even be able to see anyone approaching it, due to the extreme brightness of it's accretion disk, but if could filter out most of that radiation, the growth you only speed up the fade.

@Juni_Dingo

Ай бұрын

@@linuxp00 I'm not talking about seeing the object in visible light, but rather if you track it in space. Then you would know its position in relation to the center of the BH and after some time, you would find out that it should be behind the event horizon.

@christianthom5148

Ай бұрын

The mass of Cooper is enough to enlarge the EH, so at some (finite) time he will merge with the BH, even from an external perspective. The larger the mass of Cooper, the sooner it will happen, that why we "see" BH mergers or merger of BH with neutron stars quite frequently.

@linuxp00

Ай бұрын

@@Juni_Dingo I think there is a misconception given to a metaphor abuse. The image is not the object, it doesn't matter where the image is, just that it stops on the surface to an outside static frame, if you follow along the astronaut you not going to see any after image at all, so it's just an illusion.

@Juni_Dingo

Ай бұрын

@@linuxp00 But that is not what I'm talking about, not seeing the infalling object, I'm talking about tracking it in space. Not with light or whatever, you can calculate the trajectory etc etc. I'm not talking about light here. Just that the object will eventually end up inside the event horizon from the outside perspective in the case of a growing BH

A truly great video! Love your explenations :D

I might be too late to have this question answered but…what happens if Cooper has a jetpack attached to his torso, and he falls in feet first? There will be a point where his feet are below the event horizon, but the rest of him can still escape (from Cooper’s perspective). So if he lights his jetpack, will he be ripped in half? If yes, there would be seemingly no reason, no forces tearing him apart. And this can apply right down to the subatomic level…even chemical and nuclear bonds happen over some distance. So if his feet are causally disconnected from the rest of him, they can’t be physically connected either. How would he not notice this as he crosses the event horizon, even with no thrust forces involved???

Brilliant video again! You make those hard things so intuitive, it's genius to be able to do that. I wonder what's your take on this: I argue that even from the perspective of the falling person, he won't pass the horizon. Here's why: Suppose astronaut Bob throws Einsteins light clock towards the BH. When it nears the horizon the clock starts to tick slower. But light travels with the same speed in all reference frames. So for the light clock to tick slower, it must become bigger, seen from Bob. And since the clock almost stops ticking it is so big that it wraps around the BH multiple times. Now he himself jumps towards the BH to retrieve his clock, with a faster initial speed so he'll catch up. When he nears his clock he'll see it tick faster again since he enters its reference frame. But that also means it shrinks again. Like everything else that was already (almost) at the horizon. That would mean the BH appears to shrink until it becomes so small that he'll wrap around it multiple times, like his clock. This means the "singularity" inside the BH is actually the horizon but seen from a different perspective. QED 😜

@juliavixen176

Ай бұрын

The "event horizon" *is* a _coordinate singularly_ for any distant observer(s) far away from the black hole... but it's _not a physical singularly_ Spacetime is still continuously defined beyond the horizon, and when you switch to using, for example, the proper time of an inertial observer falling into the black hole (Gullstrand-Painlevé Coordinates) You can keep going all the way past the event horizon to the physical singularly at the black hole's center of mass.

@Jopie65

Ай бұрын

Yea so that's what I'm trying to argue against 😅 In special relativity the coordinate system is relative to the observer, different observers with different speeds use different coordinates to describe the same position. You have to do lorentzian transformations. Why would it be any different for a BH horizon? Or to argue in another way: When Bob throws in his clock, from his perspective it never crosses the horizon. But when he waits an extremely long time, hawking radiation evaporated the BH before the clock crossed the horizon. Since the view seen from the clock must be consistent with the view from Bob, the clock could never have crossed it, even from its view.

@user-qd2nd6hi8j

Ай бұрын

​@@Jopie65 Yeah, from clock point of view horizon shrinks to dot faster then he riched it. And this happens relatively fast(if clock survive unfrozen supernova explosion), but in outside world "trillions" of years will pass. about SR near BH -> hyperbolically accelerated reference frame/The Rindler horizon

aways wondering about "why" in physics and your channel not only explains the why, but the how, when and where too. great content. An outsider sees a Black Hole as a region in space, the insider sees the Black Hole as a region in time. Best explanation (based on current understanding) of a black hole and makes sense to average Joe such as I. your Interstellar film disclaimer pop up was really funny, although had to rewind, slow the speed and pause to get the joke.

@DASPRiD

Ай бұрын

Hint: you can use "," and "." to skip single frames backwards and forwards :)

Thank you for the video ❤

Love these videos! It's disappointing that there's so many scientific misconceptions around when things have be known for so long, your channel really helps to overcome that. Plus I loved your impression of the 'theory guy'.

In the isolated case of the "static" black hole and one "participant" (+ the observer who's resting compared to the black hole), this sounds valid, but what about a real scenario, where there is additional matter, and the event horizon is also increasing based on how much stuff is around it, and how close that stuff is. So we should be able to "see" Cooper close in on the horizon, let's say 1 cm away, and we should also be able to "see" the black hole's event horizon growing more than 1 cm in radius (from other matter getting close), both in finite times, which means that even though Cooper is technically not able to pass the horizon by himself, the horizon should be able to engulf him, making it possible to enter the black hole from the outside perspective, he just won't be able to reach the distance of the original horizon from the center, and this even looses meaning after the horizon engulfed him Also, what about the case where both Cooper and the black hole are moving towards each other from the observer's point of view to begin with? In that case the black hole should have no slowing down "issue", and should just go through Cooper like an eraser, because otherwise the observer would have to experience Cooper to basically be "pushed back" by the black hole, while he seemingly turns into a sculpture, which doesn't seem to be valid. However if he is indeed gets "ran over", then that implies, that the observer should be able to shift into a perspective where Cooper is swallowed, and back to one where he's not, since it was just a matter of perspective, thus making it possible to experience someone going into, and out of a black hole, which should be impossible So in summary, even though I though I understood it, I just got confused again :D

@MTd2

Ай бұрын

You are right.

@absolutehuman951

Ай бұрын

I think he will be pushed, not sure about the math tho

@thedeemon

Ай бұрын

Yep, it's all about perspective of particular frame of reference, and a fully static solution.

@karthikeyan020

Ай бұрын

You’re right in the first part. The black hole’s event horizon does expand based on the objects that “fall into” it. It’s why black hole’s mass depends on surface area instead of volume. If both cooper and blackhole are travelling at the same speed in opposite direction, you can simply substitute that with initial condition for cooper travelling twice the speed relative to the black hole. The black hole doesn’t repel him. But drags him with it on the opposite direction to which cooper was travelling. Like a fly that hits a bus windshield, he is dragged along.

Brilliant video...very well explained. But man its mind bending!

@Mahesh_Shenoy

Ай бұрын

Thank you!

Truly wonderful videos! Thank you

11:49 what is there to do with frequency we want the wave length right if frequency is low then wave length is high that is it should be visible ????

If nothing can enter a black hole Then how black holes grow in size or two black holes merge

@biswajitsahoo9368

Ай бұрын

@@CiaDora-us1tf but that will happen infinitely in the future....

I think one of the best compliments I can give your channel, and you.. is that you never fail to make me think. About the topic at hand but also further into the subject. Questions start arising almost from the moment you start to speak. For instance.. when falling into a black hole.. looking towards the way you came.. what would you see? Does gravity affect sight? I'm sure it will depend on the black hole to start. A massive black hole, less hectic at the event horizon might be best. Upon looking "back" would you see events evolving more quickly in relation to their distance from you? I understand something entering into the black hole will look to be stuck in time.. frozen. Not sure if I've seen reporting on the reverse? Ok, your jokes are great! Your general talks on relativity are special

@leonhardtkristensen4093

Ай бұрын

I agree with you that he makes SOME people think. One thing how can a black hole grow if nothing can get into it? How can the space man continue when his time stands still. I agree that he may not know that time stands still but it does according to these explanations. In my opinion he is so convincing that he is dangerous. There are so many other physicists not agreeing with SR and GR that it is far from sure it is true. In my opinion SR and GR is partly true but only partly. It is conveniently using what fits for it's explanation and forget the rest and also makes up fanciful ones.

@lucemiserlohn

Ай бұрын

@@leonhardtkristensen4093 No scientist worth their salt disagrees with SR and GR. Every prediction made by both theories have been observed time and time again. What is true is that GR is considered incomplete; there are edge cases in relation to quantum mechanics where GR and QM disagree on what happens, and that must be reconciled. That is not the same as GR being wrong. Space man can continue because in his reference frame, nothing unusual happens. He and the outside observer do not share the same inertial system, and thus, the same rules apply to them with different outcomes. That is the "relative" in relativity. Observations and measurements between different inertial systems disagree, they are relative to the inertial system. There is no fundamental overarching "truth".

@johnmagnotta8401

Ай бұрын

@@leonhardtkristensen4093 according to Susskind.. that's exactly how. Matter attaches to the perimeter.. increasing the perimeter. *remember I'm a KZread physicist AT BEST!* so my interpretation and words used aren't the best. Leonard susskind is a hard listen but if you're into this stuff, he has some great lectures. Don't expect nothing like this channel whose main focus is US.. susskind speaks at Stanford (if I'm correct)

@johnmagnotta8401

Ай бұрын

@@leonhardtkristensen4093 as for not agreeing.. that's science. Science isn't about what's known.. its what's provable. Trying to discredit SR & GR IS THE WORK! Every time an experiment falls by the wayside.. that's more credit to the theory! If you look at research papers.. ANYONE can put an idea forward, doesn't mean they will be accepted.. I'm trying to say.. science isn't stuck up. It WANTS to be discredited.. that's the nature of science. Every failed experiment or test is just as vital as a discovery. Without it we would still believe in witches

@leonhardtkristensen4093

Ай бұрын

@@lucemiserlohn I am in no doubt that Time keepeng slows down with speed and probably with gravity too. I have the believe that it has to do with electro magnetic movement at the atomic level. It correspond with what I know about signal delay through electronic circuits. The actual reason we will probably not know until we work out what electric and magnetic signals really are. I also believe that it is the two way motion of the EM that is involved. I believe time keeping is an oscillation at the atomic level and there fore a two way motion. I believe this is a thing that probably happens in organic bodies too so people will probably have the same time dilation as atomic clocks but I am not sure that that has been proved. By the way has any body checked light being bend around the moon? Bending around any star could also be from an atmosphere or plasma being there. It may well be the "incomplete" in SR and GR that bothers me. Also I have the feeling that if we could work out how to detect EM one way then we may well come to that there is some thing absolute. EM of cause travel at c.

Does the *APPARENT* distance of the event horizon (EH) to the BH reduce the closer you get to it? Does the classical definition of the radius of the EH assume infinite distance away from the BH? Surely light emanating from just inside the EH can still propagate some distance out before being red-shifted out of 'existence' (?), so possibly crossing the EH and seen from just outside the EH?

You are the master explainer. I love it. Thank you, sir!

It's too dark.

If nothing can enter a black hole from our perspective, how do we observe gravitational waves from black hole mergers?

@claudiaarjangi4914

Ай бұрын

@kinitpatel1866 The gravitational waves are from the spacetime outside the black hole. The spacetime outside the b.hole is being pulled by each "piece" behind/ next to it, like a treadmill. So the gravity doesn't have to "get out" of it to keep travelling away, 😁🌏☮️

With the immense gravity pulling on the cannon slightly more on the cannon than the ball.. when fired would it be possible for the ball to stay in place (move slightly) but the cannon to move backwards? Just spitballing.. or missed where the cannon is positioned or how positioned.

Was waiting from morning after i saw the community post...

I think the video title is misleading. It should be “Why can an outside viewer never observe anything entering a Black Hole”

@SodiumInteresting

Ай бұрын

Its a click bait title, I don't hold it against him as its a good video

@schlechtj1

Ай бұрын

no. nothing can enter. he didn't explain why even from Cooper's point of view he doesn't enter. black holes do not live forever in reality. they evaporate from Hawking radiation before he can fall in even though that is a very short amount of time from his perspective.

@Mahesh_Shenoy

Ай бұрын

It’s not a clickbait! From the perspective of the outside observer, there are no events beyond the event horizon! (By definition). Something entering a black hole would be an event beyond the event horizon. So, that can’t be true.

@wmpx34

Ай бұрын

It’s almost as if the title’s interpretation is….relative

@PPP-on3vl

Ай бұрын

​@Mahesh_Shenoy if space flip with time there must be many "times directions" in Black hole ?

Woah. That is a hugely widespread misunderstanding. Thanks for this reponse.

One of your best videos! loved the funny component of it.

now my only question is... how does the star becoming a black hole even look like during that process? does the infinite curvature appear at some random point within the star? many points? and then what? is there already an event horizon at that point, where? does it grow? aren't things therefore "entering" the black hole as the horizon grows? how does it become black? is it instantaneous, or is it a gradual red shift until it's not visible anymore? to our point of view, is the star inside of the black hole, or is it eternally falling onto the horizon?

@chadb9270

Ай бұрын

But, we have direct evidence of things entering into black holes on our timescale. We have black holes merging with black holes. So, something needs to be able to go through the event Horizon on our timescales because those mergers are spectacularly fast.

@Hegonauta

Ай бұрын

@@chadb9270 was just about to say this, nicely put, i love the video but was left with that doubt in mind

@henrycgs

Ай бұрын

@@chadb9270 black holes aren't really "objects", they're regions of spacetime. a black hole "falling" into another isn't like an object falling there, it's further distorting the spacetime around both of them. to us there is nothing inside the black hole, so matter doesn't actually enter either of them.

@henrycgs

Ай бұрын

@@CiaDora-us1tf yeah, like. i'm not sure, actually. if anything, this video suggests that all the matter of the star is still falling and will remain falling forever, before it reaches the horizon. now, the mystery to me is when exactly and where does the horizon actually appear.

@henrycgs

Ай бұрын

@@CiaDora-us1tf in the very middle i'm not so sure. if you go there sure, but right now, from our point if view, there isn't, it would take infinite time for something to even cross the horizon, let alone reach the center.

16:33 who would want to go to previous monday. I would go to sunday instead............if i could

Love the interactive format of this video.

a) You can see an astronaut entering a black hole. Once he is very close, the region around the black hole becomes denser the Schwarzschild radius for that region, so the Schwarzschild radius of the black hole increases. You end up seeing the black hole increasing in radius and "eating" the astronaut. This is seen observationaly in black hole and neutron star merges (the neutron star is a fat astronaut). The final black hole just increases its radius a lot and we don't even see any meaningful red shift photons at all. b) In real GR solutions, according to what we see, we do see matter exiting a black hole coming from the future: all real black holes are extremely fast spinning and, according to Kerr Solution, the ring singularity is removable (not actually proved yet), but if mass passes its ring, it will enter another universe where time is inverted, that is, it will enter a white hole. But we don't know if this is physical or not, but the solution is there.

I am ur big fan

@pradipgyawali1009

Ай бұрын

Sir I wanna know various science things but I am not getting a chance to do so. from which university have I graduated.

Great video as always😉

Hi Mahesh, when you say as an observer we do not see anything falling into a black hole because it takes forever, you mean the image of the object right ? The object itself is gone when we see its image slowing done, Is that correct?

@Mahesh_Shenoy

Ай бұрын

Both! From our perspective, there are no events beyond the event horizon. Falling into the black hole would be an event beyond the horizon!

1st comment?

@kriiistofel

Ай бұрын

Me second

@Mahesh_Shenoy

Ай бұрын

I beat you to it 6 hours ago :D

@siddharthannandhakumar6187

Ай бұрын

​​​@@Mahesh_Shenoy We'll I can't travel to the never existed past... If Blackhole is the event horizon, your premiere was the event beginning 😄. I've explained my 'Proper rest' in the other comment's reply. Kindly see it if you are seeing this.

if you were to reach the speed of light, would you freeze forever due infinte time dilation?

I tried hard to read the last line of your t-shirt, but the camera never covered it, what does it say? I am dying to know 😊

The y=1/x on your shirt really matches with the situation you have to go to infinity to see the graph touching x axis similarly as you have to wait for infinite amount of time to see the person toching the event horizon

The way I've heard it explained is that all paths lead to the singularity. There's also a theory that says you would see the singularity no matter which direction you look inside the black hole. Assuming the singularity is emitting light

@thedeemon

Ай бұрын

Even if it was emitting light, that light couldn't go "up" to you, so you won't see it even if every available direction for you indeed leads to singularity. It's like here you can move in any direction and you're still heading towards next Monday, next Monday is in your every direction yet no light can come to you from it, you can't see it.

I feel like my mind has become a black hole. But it was just blown. Awesome video, as always!

One of the greatest explanations of all time ❤🎉

If it takes an inifinite amount of time to enter a black hole (for an external observer) and we know that all black holes will evaporate in a finite time, could it be that what you would feel, when crossing an event horizon, is the final evaporation and explosion of the BL?

@schlechtj1

Ай бұрын

Yes! someone gets it!

@juliavixen176

Ай бұрын

No, if you're in inertial free-fall you will not observe any Hawking Radiation.

How do things change in rotating Kerr black hole?

Its getting better with every video :D

Hay where did you learn all these things from? Did you took a GR course? I also want to learn these things but i can't take GR course? Cam you recommend some books or material to learn GR? (Undergraduate student here)

@Mahesh_Shenoy

Ай бұрын

Checkout ‘exploring black holes’ by wheeler and ‘General relativity the theoretical minimum’ by Lenord Suskind

@pavangaonkardonigadde

Ай бұрын

@@Mahesh_Shenoy okay thanks

Amazing mind blowing explanations

Some 40 years ago, Dr Venkatavaradhan, the then director of Mumbai's famous Nehru Planetarium, gave a lecture at our college about Black Holes and the inevitable "why nothing can escape from it" story. It was new then and so very fascinating, and I have been hooked for life into topics of stars and gravitation and black holes. Great video, and thanks for the insight, but with due apologies to Einstein, I fell I will stay with old one for some more 'time' - at the edge of the horizon!

So from our perspective, one black hole will never enter the event horizon of another black hole. Meaning that they will never collide, but yet LIGO saw gravitational waves of black holes colliding. Now i am puzzled.

This is my favorite series on KZread!

Thanks, I love your videos! Does "time not tick at all" 8:38 in a literal way, meaning complete halt, at the edge of the black hole from our perspective? Or is it rather SO, SO, SO very slow that we cannot measure the rate? Meaning that it has practically stopped, from our perspective. I'm thinking that if time comes to an absolute 0 rate from whatever perspective then it must also be 0 rate from Coopers perspective. But from Coopers perspective time does not stop, so it has some rate, it is just too slow from our perspective. Am I missing something?

13:09 What does mean by the space time is pretty much flat near the black hole? even close to the event horizen. Could you please explain it?

@Mahesh_Shenoy

Ай бұрын

Meaning he couldn’t tell if he is close to a black hole or far away in deep space far from any planet/star!

@Arush1995

Ай бұрын

But near the event horizon, the diameter of the space time should be infinite! Isn't it?

astonishing, why you are making such a difficult concept/theory sooo easy to understand, ❤❤❤❤ i never thought the other perspective 😂😂😂

Hello Mahesh shenoy !!!! Today i got your video in my recommendation section and i am so happy that i clicked it Your videos are amazing interesting and unique Btw i am gonna watch every video on this channel within a week 😂😅😅 Keep making videos ❤

One question, if from "outside" nothing can enter the black hole, and a ship is not a single point, what happens to the front of the ship that crosses the event horizon from the POV of someone in the back of the ship? Does the event horizon move depending on the space time curvature of the POV?

@juliavixen176

Ай бұрын

The event horizon _is_ completely empty space. There is _nothing physical_ there. It is a mathematical coordinate singularly in the coordinate system of a _very distant observer_ located *very far away* For an observer close to the event horizon, it will always appear to be ahead of them, like a mirage that moves further away when you get closer to it. (For technical reasons I'm not explaining here.) You will never see yourself cross it. (Of course, assuming you don't die from having your atoms torn apart.)

@zekicay

Ай бұрын

@@juliavixen176 thank you for the explanation! Would it also mean that you need to accelerate and hover at the event horizon in order to see the entire future of the outside universe?

Mahesh you may try to explain with light cones visually. it may be more clear.

wow amazing explanation

So, when two black holes collide, they cannot merge together to form a single black hole; but freeze as a "double black hole" touching each other at their corresponding event horizons??

@Mahesh_Shenoy. I have always thought that if you were to travel "close enough" to a black hole you would actually see a collage of all the things that have fall in it in the past since the black hole was formed, which is what you seem to indicate by the no entry to the black hole concept, however this idea has been rebuffed in other forums, I was told that you in fact see nothing but an empty canvas. Which one is it?

Absolutely brilliant presentation, your channel is quintessential for learning physics by all of us, thank you very much. I hope to see you again on 03/12/23.😎

do photons have thrust or are they projectiles? if they are projectiles they would slow down to not be able to escape the black hole but they can't slow down so they must have thrust right?

@thedeemon

Ай бұрын

They are "projectiles", following their geodesics like other projectiles. Due to spacetime warping, their paths near a black hole might be quite weird. Like, a photon shot directly "up" from the event horizon, stays at that place.

@schlechtj1

Ай бұрын

they technically are neither because they always travel at the same speed, a force will not slow them down. but as pointed out, the flow of time around them can change. the environment around a black hole is also strange because it's stretching space also which then takes light more and more time to cross.

This is it. The notion that light is trapped because of escape velocity is wrong given that photons are massless and travel at the universal speed limit

I wonder what a space time graph of the black hole would look like. Every direction takes you to the same place right?

This is an amazing video! I love the excitement in which you share knowledge. Though, I have one lingering question after watching. If nothing can ever enter a blackhole, then how does it gain more mass? Does it all just pile up at the surface from our perspective? I know its going into the blackhole from their own perspective but as far as the rest of the universe is concerned, the blackhole should never grow in size right?

@juliavixen176

Ай бұрын

Yeah it piles up... but there's not really an "inside" that stuff needs to be inside. "Gravity" is the (global) geometric shape of 4D spacetime ... I mean... you don't need to be "inside" the Earth to contribute to how much "gravitational force*" the Moon feels in orbit. From the Moon, the ISS is contributing to the Earth's gravity while not physically touching the ground. If you're a satellite in space at the L1 Lagrange point between the Earth and Moon, each feels your gravity contributing to the mass of the Moon and Earth.

Is there any distance constraint on event horizon? Does it have any thickness? If you went in feet first, there would be a point where your head would not see your feet inside. The blood from your feet would not be able to return to your heart. You would no longer feel your feet as the nerve signals could not come out.

So if a neutron star (or a small black hole) gets absorbed by a much bigger black hole, are you saying we can never observe the event occurring even though we can measure the gravitational waves from the resulting collision?

@thedeemon

Ай бұрын

For practical purposes we can think about a surface 1 cm above the horizon. Matter can easily cross it in finite time, and after getting there become invisible for us due to red shift and so on. So practically a star can get absorbed no problem, even if mathematically we might think it gets stuck in the last mm of the way, from our perspective.

I agree with many of the other commenters.. your videos are quite informative and entertaining simultaneously. I don't find those 2 adjectives said together often. Especially with relation to relativity, general speaking, it's special :)

For outside observer gravitational time dialation is in effect only if a body is accelerated near mass

If you are correct, then distant black holes in empty space would actually glow with EM radiation, as even the red shifted light would be information dense compared to the empty space beside the black hole

Clarification: Gravity is most definitely a factor. As Einstein described, space-time is like a sheet. When thinking about a planet, star, black hole, etc, gravity is the object’s mass on the fabric of space-time. Which creates a dip on this flat sheet, shaped like an upside down cone. Smaller objects are pulled into this cone, some attain a stable orbit, while others fall straight in. That’s gravity. Black holes typically have a much larger mass than its actual size. Meaning, that it causes a huge dip in the fabric of space-time. Much bigger than say a star with the same “physical” size. It’s a massive gravitational force. We know that in a typical black hole, if you fell in, whatever atoms are closest to the black hole will feel more gravitational force than the part of your body furthest from it. You’ll be stretched thinner and thinner until you look like a spaghetti noodle that’s just a string of disconnected atoms. Which is where the term “spaghettification” comes from. Again, this is the effect of a differential on the gravitational force on the atoms that made up your body. That’s the fundamental reason that you cannot escape from a black hole. The gravitational force at and beyond the event horizon is greater than the escape velocity of the speed of light.

your videos are great. :)

Sir Please Make a Video On Hawking's Radiation too you made me more confused, is it true

Hey y'all, I just got back from the infinite future, and I gotta say, it is pretty cool watching everything fall through the EHs is a sight to behold!

How does the evaporation of a black hole (and its timeframe) fit into this?

@schlechtj1

Ай бұрын

from Cooper's point of view, since his view of time is accelerated from ours, the Hawking radiation is increasingly more intense and the black hole will explode from his point of view before he enters it.

@juliavixen176

Ай бұрын

​@@schlechtj1Cooper is in inertial free-fall and so will not see any Hawking radiation. Cooper's own view is _not_ "actually accelerated" as you said. When you use Cooper's proper time as the basis of a coordinate system, he does collide with the physical singularly at the black hole's center of mass in a very brief duration of time. The light from the rest of the universe falling in behind him will be red-shifted from tidal "spaghettification" and eventually (soon) become "frozen in time" never catching up with him.

@schlechtj1

Ай бұрын

@@juliavixen176 please explain how free fall exempts you from encountering particles traveling away from the black hole. if we can calculate how much radiation is exiting for a distant observer, that radiation is multiplied by the dilation Factor for something near the black hole.

Enjoyed that. Thanks! But these contradictions make it seem like we really don’t know and just apply our best guess 😂

Few questions. No object with mass can reach speed C so the time will not stop for it completely am I wrong? How do they merge? What happens with all the objects "frozen" outside of the black hole when it merges with another one and the event horizon extends?

@kylelochlann5053

Ай бұрын

Massless "objects" can only travel at "c". There are no frozen objects anywhere. Everything vanishes at the horizon.

Imagine Cooper's view of the rest of the universe as he approaches the event horizon. Time passes normally for him, but far away from him, time appears to be passing faster. When he is close to the event horizon, every second that passes for him equals millions of years passing for the rest of the universe. When he reaches the event horizon, time outside the black hole becomes infinitely fast and he witnesses the end of the universe. He cannot leave the black hole, because the universe outside it no longer exists from his perspective.

@notme2.o654

Ай бұрын

If Cooper sees the rest of the universe age,wouldn’t he know that in his frame of reference time has slowed down which contradicts the fact that time is passing normally for him?

@thedeemon

Ай бұрын

To enjoy this view of infinitely fast universe he must stop falling somehow and stay at the horizon exactly, which is impossible for a massive body just like it's impossible to move at light speed. If he falls down, he doesn't see the universe accelerated so much, as light struggles to catch up with him.

The better than the best explanations and clarifications I have ever got hats off to you 🙋🏻‍♂️ its really mind opening 👍🏻 all the best hope you will keep clearing other mind bending things for us 💐

awesome as always

Your t-shirt really made me realize that conic sections are love 😍

Thank you so much for this video to help Mr understand how black hold works. Would you please do a video explaining how black hole merger works? When 2 black hole merges into a bigger one, does that mean only their event horizon merges together but not inside of the black hole?

I think hawking radiation solves the two perspectives paradox. From cooper's perspective he enters the black hole but as he does he's dissolving into radiation until he'a completely gone (never reaching the center). From outside perspective he's chilling at the event horizon forever until the black hole itself radiates away and the event horizon shrinks into nothing. Idk I could be wrong.

If we abandon the Newtonian perspective, what does the gravitational gradient look like inside and surrounding a black hole? I'm confused as to why the time dilation approaches infinity at the event horizon rather than at the singularity at the center of the black hole.

I don't know what to say, but this is the best video on the internet about blackhole! ❤