I never understood why nothing can escape a black hole... until now!

Why nothing can ever enter a black hole in the first place (not even light). We always talk about escaping from black hole, but from a certain perspective, nothing even enters a black hole.

This video is sponsored by Ground News.

[Mahesh_Shenoy]

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?

[TankEsq]

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

[ottosonm]

I'm a huge fan and have watched many of your videos. I almost skipped this one because I *know* why nothing can escape a black hole. At 0:26 my jaw dropped. Then seeing how escape velocity is not the reason I literally slapped my forehead! I just love the deep, intuitive understanding your videos provide. Thank you!!

[davidbale]

"... 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!

[investigator]

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.

[ankitsingh]

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

[BogdanSilviuAron]

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!

[void_vale]

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?

[conorokane]

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.

[parthhooda]

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

[comicdragoon]

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 ;)

[KetilDuna]

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

[mehmetdemirci]

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??

[voodoochile]

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.

[cat_a]

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

[vvc]

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

[andrewcarr]

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.

[syiridium]

- 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)

[jmtaviation]

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

[Achrononmaster]

@17:30 a cool video segment here would be one of your paper models showing the light cones tilting so you can see the external space is indeed now in Cooper's past light cone.