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Speaker 1: Hey, Daniel, what's the best place in the universe to

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Speaker 1: hide something? Like? What do you want to hide? You know,

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Speaker 1: treasure or secrets anything. I guess you could tape it

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Speaker 1: to a rock and hide it in the asteroid belt

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Speaker 1: among millions of other rocks. Yeah that's pretty good. But

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Speaker 1: you know, technically somebody could still find it. Yeah, that's true.

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Speaker 1: I guess you could drop it in the sun. I

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Speaker 1: said hide it, not destroy it completely. All right, this

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Speaker 1: is pretty tricky. What if you put it into a

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Speaker 1: black hole? It depends can you wait like two zillion

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Speaker 1: years to get it back out again? But you mean

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Speaker 1: you can get things out of a black hole? Well,

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Speaker 1: you know, technically depends on the definition of out. But

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Speaker 1: if you want to throw a dictionary into the black hole,

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Speaker 1: everything comes back out except for the page that says out. Ye.

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Speaker 1: Hi am Jorge Immad, cartoonists and the creator of PhD Comics. Hi.

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Speaker 1: I'm Daniel. I'm a particle physicist, and sometimes I feel

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Speaker 1: like my mind has been thrown into a black hole.

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Speaker 1: Oh yeah, is it that nothing comes out of it?

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Speaker 1: That would be the case if my mind was a

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Speaker 1: black hole. But sometimes I feel like everything I've learned

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Speaker 1: has been slurped up and dropped into a black hole

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Speaker 1: because I can't remember any of it. It gets spaghettified.

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Speaker 1: And what if he eat spaghetti? What happens to spaghetti

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Speaker 1: when it gets spaghettified? It becomes spaghetti squared, becomes a

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Speaker 1: string theory maybe, but welcome to our podcast Daniel and

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Speaker 1: Jorge Explain the Universe, a production of I Heart Radio,

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Speaker 1: in which we tear our minds into little pieces of

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Speaker 1: spaghetti and then stretch those out into tiny little strings

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Speaker 1: in a vain and futile attempt to understand everything in

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Speaker 1: the universe. We take it all apart, we tear it

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Speaker 1: in a little bits, and we try to put it

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Speaker 1: back together in a way that we hope you can understand.

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Speaker 1: That's right, because it is a long and tasty universe

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Speaker 1: out there, with lots of mysteries and unknowns and exciting

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Speaker 1: things discover, and lots of different sauce options. You know. Actually,

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Speaker 1: I just realized they're spaghettini, right, and angel hairy pasta.

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Speaker 1: Although I don't know the difference. There must be a

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Speaker 1: whole spectrum, right, It's not like pasta is quantized. There

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Speaker 1: must be an infinite number of kinds of pasta. Well, eventually,

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Speaker 1: pasta is quantized. Everything is quantized eventually, right if you

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Speaker 1: get down to a single chain of pasta atoms, right,

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Speaker 1: nano pasta. Yeah, that's a whole new field of fabrication quarkinis.

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Speaker 1: But yeah, the universe is full of interesting and amazing things,

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Speaker 1: and none more so mysterious than black holes. That's right.

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Speaker 1: Black holes are these weird corners of the universe where

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Speaker 1: we think secrets lie. We suspect the solution to the

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Speaker 1: age old conflict between general relativity and quantum mechanics might

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Speaker 1: lie right at the heart of black holes. Of course,

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Speaker 1: nobody can see inside them, so it's incredibly frustrating to

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Speaker 1: think that the answers to some of our deepest questions

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Speaker 1: exist but are hidden from us. Does that drive physicist

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Speaker 1: bonkers to know that you know there are answers out there,

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Speaker 1: but maybe they're trapped in a place where they can

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Speaker 1: never get out. That's essentially the project of physics, right,

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Speaker 1: The answers are out there. The universe does contain these answers,

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Speaker 1: and if you can come up with the right experiment,

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Speaker 1: you can force the universe to reveal those truths. That's

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Speaker 1: basically how we accumulated all the knowledge that we do have.

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Speaker 1: But yeah, it's frustrating to think that there might be

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Speaker 1: places in the universe that nobody could ever look, where

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Speaker 1: information could hide forever, escaping from even our most clever

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Speaker 1: efforts to reveal them. You may get sound like physicists

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Speaker 1: are like paparazzis of the universe, Like you're trying to

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Speaker 1: catch the universe, you know, sunbathing in its supports or something.

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Speaker 1: I used to think of us as more like murder

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Speaker 1: mystery detectives, But yeah, paparazzi is a more positive way,

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Speaker 1: because the universe is beautiful. It deserves our attention. Positive. Yeah, yeah,

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Speaker 1: I guess they're surprised to being d universe. We're just

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Speaker 1: here trying to enjoy the beauty of the universe, you know,

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Speaker 1: and get its signature once in a while so we

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Speaker 1: can sell it on eBay and so to the National

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Speaker 1: Enquirer or Science magazine, you know, one of those two

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Speaker 1: whoever will take it. Is this part of the free

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Speaker 1: Brittany movement. I don't think there's a free universe movement

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Speaker 1: where they're like, hey, physicists, leave the universe alone. Keep

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Speaker 1: some of the mystery. You know, maybe doesn't want to

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Speaker 1: reveal its mysteries. You're being pushy. The mysteries are wonderful,

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Speaker 1: but the incredible part of this journey of physics is

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Speaker 1: that the truth is always more amazing and bonkers and

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Speaker 1: beautiful than we even possibly imagined, and so it's always

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Speaker 1: worth trying to dig into it and figure out what

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Speaker 1: the truth is. And so recently we've taken pictures of

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Speaker 1: black holes. You sort of know where they are, you

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Speaker 1: can see them gravitationally, and now we know what they

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Speaker 1: actually look like. But they still remain a pretty big mystery,

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Speaker 1: maybe even the biggest mystery we have in the universe, right,

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Speaker 1: that's right, And new mysteries keep popping up. You know.

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Speaker 1: Originally people were like, wow, our black holes real, and

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Speaker 1: then we discovered that they are actually out there and

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Speaker 1: that was kind of mind blowing. But then more questions

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Speaker 1: arose about them, and more questions and more questions, and

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Speaker 1: they're just like an endless playground for theorists to think

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Speaker 1: about what the universe means and and how it behaves

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Speaker 1: in really strange circumstances, and so they're continual source of

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Speaker 1: mystery and also opportunities to learn things about the universe,

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Speaker 1: because that's what mysteries are. They are ways for us

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Speaker 1: to unravel a thread and figure something out, right, because

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Speaker 1: I guess anything that happens in the universe tells us

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Speaker 1: a little bit about how the universe works, especially the

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Speaker 1: really extreme situations like black holes. Yeah, because we think

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Speaker 1: that the universe follows rules right there. There are physical

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Speaker 1: laws and everything in the universe always has to obey them.

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Speaker 1: Why that is is like a deep and fun question

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Speaker 1: in the philosophy of science, So check out some other

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Speaker 1: philosophy podcast for that. But the goal of physics is

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Speaker 1: to take advantage of that fact and say, let's find

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Speaker 1: opportunities where the things that happened reveal what the rules

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Speaker 1: must have been. You make It's not like we should

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Speaker 1: named the podcast Daniel to Daniel and Jorge Exposed the Universe.

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Speaker 1: That sounds a bit too risk, ay, And we're trying

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Speaker 1: to be family friendly here. So black holes are mysterious,

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Speaker 1: and there's sort of super extra mysterious. I feel like,

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Speaker 1: you know, I feel like there's not just kind of

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Speaker 1: the questions of what happens inside or what happens as

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Speaker 1: you go in, or how they can possibly exist in

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Speaker 1: the universe. But there's also sort of some very interesting

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Speaker 1: theoretical questions. Yeah, it's sort of weird that black holes

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Speaker 1: even exist. You know. One theory of physics say that

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Speaker 1: they can't exist, but they have to have certain properties,

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Speaker 1: and another theory of physics is that those properties are impossible.

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Speaker 1: So there's like a conflict at the heart of physics

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Speaker 1: between our idea of space and time, which is governed

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Speaker 1: by general relativity, and our idea of how the universe

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Speaker 1: works at the smallest scale, which is governed by quantum mechanics,

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Speaker 1: And those two disagree about what's going on inside a

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Speaker 1: black hole, whether black holes can live forever, and all

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Speaker 1: sorts of stuff, and so there are really fun mysteries there.

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Speaker 1: And so there's one mystery in particular that people have

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Speaker 1: been wondering about four decades about the stuff that goes

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Speaker 1: into the black hole. Yeah, and it seems like very

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Speaker 1: recently scientists have made some pretty um possibly interesting progress

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Speaker 1: towards solving one of these big mysteries. So have they been, um,

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Speaker 1: you know, parked outside their favorite coffee shop, you know,

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Speaker 1: just waiting to take those pictures the physics paparatti Exactly

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Speaker 1: when will that black hole finishes spa appointment. So to

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Speaker 1: the end the program, we'll be asking the question, have

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Speaker 1: we solved the black hole information paradox? I love that phrase,

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Speaker 1: black hole information paradox. It's got some poetry to it. Yeah,

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Speaker 1: it's a little too long for me. I kind of

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Speaker 1: struggled to get that one out. Black hole information paradox?

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Speaker 1: Have we solved it? That's the question? That's the question,

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Speaker 1: all right. So there's a paradox about black holes. It

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Speaker 1: involves information, and we think that maybe in their last

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Speaker 1: few months, maybe I physicists have solved this paradox. That's right.

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Speaker 1: It's a puzzle that's been outstanding for decades and to

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Speaker 1: one of those questions that people always thought, wow, if

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Speaker 1: you figure that out, then you're gonna learn something deep

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Speaker 1: about the universe. Or they imagine that maybe in a

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Speaker 1: hundred years somebody will know the answer to that. So

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Speaker 1: have some progress made on it to have people feel

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Speaker 1: like maybe they've even found the solution. It's a big deal, right,

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Speaker 1: And apparently recently something has happened, so people have appolished

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Speaker 1: the paper or they what happened? You know, there's been

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Speaker 1: a whole series of papers in this past year where

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Speaker 1: people have found a whole new way to attack this

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Speaker 1: problem and made what they thought was pretty exciting progress,

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Speaker 1: and some people even think that they may have solved it.

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Speaker 1: Oh interesting. They found a new method of attack, yes, exactly,

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Speaker 1: a new theoretical way to attack black holes, without of course,

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Speaker 1: actually going over there and measuring anything. All right, Well,

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Speaker 1: as usual, we were wondering how many people out there

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Speaker 1: had heard about the black hole information paradox, or that

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Speaker 1: they might have found a solution in for it. So

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Speaker 1: Daniel went out there into the wilds of the internet

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Speaker 1: to ask folks, what is the solution to the black

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Speaker 1: hole information paradox? That's right, So thanks to everybody who

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Speaker 1: volunteered their minds and their time. If you would like

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Speaker 1: to participate for a future episode, please do not be shy.

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Speaker 1: Right to me two questions at Daniel and Jorge dot com.

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Speaker 1: It's fun. Here's what people had to say. I don't

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Speaker 1: even know of a paradox information wise in black holes,

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Speaker 1: so um, I don't have the solution. I'm very sorry.

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Speaker 1: I believe it is that all the information is imprinted

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Speaker 1: on the surface like a that's what they call it,

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Speaker 1: a hologram. And some series actually said that how your

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Speaker 1: whole universe could be something like that. The paradox is

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Speaker 1: about what happens to information that gets sucked into a

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Speaker 1: black hole. I think what happens is that it gets

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Speaker 1: stored at the event horizon of the black hole, more

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Speaker 1: like black hole disinformation coles are trying to trick us. Well,

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Speaker 1: I guess this one refers to the fact that information

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Speaker 1: can get sucked into the into a black hole and

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Speaker 1: then you cannot get access to it anymore. Um but

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Speaker 1: ultimate information is just hidden in the black hole and

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Speaker 1: they destroyed it. So maybe the solution is that there's

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Speaker 1: no paradox after all. I don't think I know the

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Speaker 1: answer to the black hole information paradox, but I do

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Speaker 1: know that information can't be destroyed, so it's got to

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Speaker 1: be in the black hole somewhere. How that information gets extracted,

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Speaker 1: I'm not exactly sure. It sounds lucky. It's something to

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Speaker 1: do with Obviously, nothing can ever leave a black hole. Um,

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Speaker 1: but Hawking radiation says that, um, if left a lot

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Speaker 1: of nothing else goes into it, eventually they could evaporate

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Speaker 1: into nothing. Um that sounds pretty paradoxical to be so.

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Speaker 1: I had seen that a solution had been found recently

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Speaker 1: or in the past year or so, But apparently it's

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Speaker 1: something and going in leaves an imprint on the event horizon,

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Speaker 1: which somehow is represented in the radiation in the Hawking radiation.

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Speaker 1: But that kind of seems wrong because of the uh

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Speaker 1: no hair theorem. I mean, I think that's the gist

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Speaker 1: of it. I have heard of the black hole information paradox,

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Speaker 1: but I'm not sure exactly what it is. I believe

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Speaker 1: it is related to Hawkings radiation. Well, I suppose I

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Speaker 1: would ask why does it need to be conserved in

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Speaker 1: the first place? So why would it information disappearing be

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Speaker 1: such a problem. Perhaps it's not a problem at all,

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Speaker 1: especially if information seems to be created as new space

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Speaker 1: is created. Maybe it's not a problem that information goes

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Speaker 1: away when it enters a black hole. All right. Not

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Speaker 1: a lot of people had heard of this, you know,

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Speaker 1: a lot of good speculation, but yeah, no concrete answers there,

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Speaker 1: and some people seem to know what it is though.

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Speaker 1: That's pretty impressive. Yeah, well, we covered it on an

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Speaker 1: episode dug deep into the nature of this paradox about

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Speaker 1: information and black holes. Though I guess our listeners have

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Speaker 1: done their homework Apparently our episode didn't fall into a

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Speaker 1: black hole. It actually made it to people's spaghetti places.

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Speaker 1: It fell into people's ear holes. Yeah, all right, Daniel

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Speaker 1: will step us through this. Then let's start with what

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Speaker 1: it is first. What is the black hole information paradox.

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Speaker 1: This is a really fun concept because it brings together

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Speaker 1: these two different theories, general relativity, which tells us something

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Speaker 1: about black holes, and quantum mechanics, which tells us something

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Speaker 1: about information. So we start with general relativity because that's

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Speaker 1: where black holes come from. General relativity tells us, you know,

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Speaker 1: how space is curved in the presence of mass and

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Speaker 1: stuff like that, and it's sort of the genesis of

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Speaker 1: black holes, right there are this place in space where

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Speaker 1: no information can escape. Anything that falls past the event

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Speaker 1: horizon should be inside the event horizon forever until the

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Speaker 1: end of the universe. And you can't know anything out

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Speaker 1: what's inside the black hole other than the total mass

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Speaker 1: of the black hole, whether it's spinning, and whether it

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Speaker 1: has electric charge. Everything else is hidden from you. So

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Speaker 1: anything that's going on inside the black hole, you can't

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Speaker 1: know anything about it because that would be allowing you

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Speaker 1: to get information out of the black hole. This is

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Speaker 1: called the no hair theorem, tells you that's a very

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Speaker 1: limited amount of information you can have about a black hole.

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Speaker 1: So that means that if your friend threw a banana

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Speaker 1: into the black hole, you couldn't tell that it was

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Speaker 1: banana instead of an apple. You can only measure the

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Speaker 1: mass that they threw into the black hole. Right, That's

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Speaker 1: an interesting concept because I guess, you know, maybe we're

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Speaker 1: all used to the idea that black holes can sort

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Speaker 1: of things, and things can't get out, not even light,

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Speaker 1: But that also I guess applies to information itself. You know,

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Speaker 1: if light can't get out, then really nothing can get out,

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Speaker 1: not even like ones and zeros or you know, just anything. Right.

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Speaker 1: That's right, because we live in a physical universe and

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Speaker 1: information has to be represented physically. So to get information

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Speaker 1: from one place to another, you have to send a message,

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Speaker 1: which means like a particle or a wave of some

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Speaker 1: kind of physical thing. So if no physical thing can

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Speaker 1: cross that boundary, then no information can get out technically,

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Speaker 1: then you can gravitational waves escape a black hole. Gravitational

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Speaker 1: waves cannot escape a black hole, but a black hole

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Speaker 1: itself can create gravitational waves. But when it creates it

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Speaker 1: isn't it sort of like sending a signal out. Now,

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Speaker 1: that's just the information about the black hole itself. Like

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Speaker 1: you can know the mass the black hole from the outside,

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Speaker 1: and a gravitational wave is just a change in like

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Speaker 1: the location of a mass. And so you can know

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Speaker 1: about where a black hole is and what mass it

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Speaker 1: has and how it's moving, and that motion can generate

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Speaker 1: gravitational waves without knowing anything about what's going on inside

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Speaker 1: the black hole. All right, So that's a general relativity.

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Speaker 1: And then how does quantum mechanics figure into it. Well,

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Speaker 1: quantum mechanics says something really important and powerful about information.

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Speaker 1: It says that you can always reconstruct the past of

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Speaker 1: our universe based on what's going on right now. It's

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Speaker 1: sort of like a post addiction. It says, if you

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Speaker 1: could scan the universe finally enough, you could figure out

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Speaker 1: what has happened. It's sort of like saying, if I

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Speaker 1: burn a book, then you should be able to from

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Speaker 1: the ashes and the smoke and everything that comes out

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Speaker 1: of it later tell me exactly what that book was.

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Speaker 1: That all the information from that book is still somehow

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Speaker 1: imprinted in the universe, even if sort of scattered now

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Speaker 1: and harder to reconstruct, right does it kind of related

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Speaker 1: to that idea that we've talked about before, which is

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Speaker 1: the idea of cost and effect. Like if a particle

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Speaker 1: does this and it affects another particle, and that particle

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Speaker 1: affects another particle, you can always backtrack kind of what happened.

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Speaker 1: That information is not lost, like what one particle does

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Speaker 1: to another particle they remember, right, yeah, exactly. That information

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Speaker 1: is not lost. And our present state of the universe

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Speaker 1: is unique, right, it maps back to a single past.

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Speaker 1: You can't have two different pasts that produce the same

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Speaker 1: present because then you wouldn't be able to tell which

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Speaker 1: was which. And so you have all the information you

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Speaker 1: need in the present to reconstruct the past. And this

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Speaker 1: is a really deep and powerful important thing and quantum

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Speaker 1: mechanics like that's at the basis of quantum mechanics. It's

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Speaker 1: called unitarity. And if we didn't have it, if it

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Speaker 1: wasn't true, then we would have to question like quantum

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Speaker 1: mechanics itself and come up with another theory. So it's

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Speaker 1: like something every physicist out there believes is true about

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Speaker 1: the universe. The information is not lost because when you

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Speaker 1: think clancal mechanics is pretty real. We think it's pretty real.

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Speaker 1: We've tested it pretty well. We tested all day every

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Speaker 1: day at the Large Hadron Collider and in lots of

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Speaker 1: other different ways, so we're pretty sure it's true. Although,

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Speaker 1: you know, black holes are an extreme situation, so maybe

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Speaker 1: something gets broken. You never know. That's kind of where

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Speaker 1: the paradox part comes in, right, there's a paradox about

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Speaker 1: what happens between these two concepts of the universe inside

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Speaker 1: of a black hole exactly, because you might ask, well,

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Speaker 1: what happens to the information about my banana if I

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Speaker 1: throw my banana into the black hole and now it's

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Speaker 1: inside the black hole and I can't learn anything about it,

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Speaker 1: where is that information? Well, general relativity says black holes

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Speaker 1: live forever, and so that's a problem. The information is

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Speaker 1: still inside a black hole. It was just sort of

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Speaker 1: stuck there. And that's okay, except that we don't think

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Speaker 1: that black holes live forever. We think, thanks to Hawking radiation,

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Speaker 1: that black holes are not actually black. They give off

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Speaker 1: a little bit of radiation, they glow a tiny little bit,

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Speaker 1: and when they do that, they lose their mask because

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Speaker 1: they're giving off energy, So they get smaller and smaller

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Speaker 1: as it's called black hole evaporation, and eventually they disappear.

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Speaker 1: And so if your information about your banana was inside

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Speaker 1: the black hole and then the black hole evaporates, where's

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Speaker 1: the information? Did it disappear from the universe, you know?

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Speaker 1: Or did it somehow get leaked out in the Hawking radiation?

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Speaker 1: Is there a smell of banana once a black hole evaporations?

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Speaker 1: Is it in the air now? Stephen Hawking did a

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Speaker 1: really careful and sort of famous calculation where he showed

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Speaker 1: that the radiation itself has no information about anything inside

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Speaker 1: the black hole, only about the mass of the black hole.

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Speaker 1: So like, you can't tell what was inside the black

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Speaker 1: hole based on the Hawking radiation. So that's sort of

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Speaker 1: a mystery. Like the black hole disappears and the Hawking

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Speaker 1: radiation has just basically noise in it, So like, where

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Speaker 1: is the pattern for my banana? And that's the paradox

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Speaker 1: I see. The paradox is that it seems like information

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Speaker 1: hits the end of the road in a black hole,

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Speaker 1: whereas quantum mechanics would have you believed that it never

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Speaker 1: ends exactly, So somebody must be wrong, right, If information

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Speaker 1: is lost, then quantum mechanics is wrong, and that really

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Speaker 1: weakens the foundations of physics. If the information somehow escapes,

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Speaker 1: then that violens general relativity. Right, that's like information leaving

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Speaker 1: a black hole. How can that possibly happen? So it's

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Speaker 1: a super fascinating like sort of test bed to crash

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Speaker 1: these two theories together and say, well, you know, it's

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Speaker 1: like a cage match. Two theories go in and only

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Speaker 1: one comes out, and it depends on what happens next. Right, Yes, exactly,

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Speaker 1: it depends on what happens. No, No, I really have

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Speaker 1: a headache now. It feels like the Grandfather paradox, Like

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Speaker 1: if you put two theories into the black hole, but

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Speaker 1: only one of them can come out, but then the

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Speaker 1: black hole evaporates. What happens one of them is left

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Speaker 1: eating spaghetti? Yeah, the the Avengers movie maybe, And our

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Speaker 1: podcast episode about this, we talked about a few possible solutions.

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Speaker 1: You know. Hawking himself famously said that he thought information

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Speaker 1: was lost, that it just disappeared from the universe. But

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Speaker 1: most physicists don't believe that. Most physicists think that must

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Speaker 1: be wrong. That information is not lost. We just have

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Speaker 1: to figure out how it leaks out and So the

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Speaker 1: most popular theory until last year, until this recent progress

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Speaker 1: was made, was that maybe somehow there is information in

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Speaker 1: the Hawking radiation because the black hole surface is not

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Speaker 1: entirely smooth, like when you throw your banana onto the

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Speaker 1: black hole, maybe it gets like stretched out over the

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Speaker 1: event horizon but doesn't actually make a perfect sphere, and

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Speaker 1: that those little wiggles in the event horizons somehow contain

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Speaker 1: the information and influence the Hawking radiation. That was sort

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Speaker 1: of the direction people were going until recently interest ing.

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Speaker 1: So maybe you figure it out. Who comes out of

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Speaker 1: the cage? All right, Well, let's get into what this

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Speaker 1: potential solution is to the black hole information paradox and

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Speaker 1: most important, what does it mean. But first, let's take

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Speaker 1: a quick break. All right, we're talking about the black

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Speaker 1: hole information paradox and a potential solution to this paradox. Now, Daniel,

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Speaker 1: I guess maybe I'm having some trouble understanding why it's

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Speaker 1: a paradox, Like, you know, why can it be that,

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Speaker 1: for example, quantum mechanics does allow energy to always be

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Speaker 1: preserved except at a black hole, which is sort at

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Speaker 1: the end of the line, Do you know what I mean? Like,

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Speaker 1: why does it need to work everywhere and all the time. Well,

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Speaker 1: it really only means something if it works everywhere. You know,

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Speaker 1: momentum conservation is always meaningful if it's always conserved. You

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Speaker 1: know You're rules in your household are only meaningful if

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Speaker 1: your kids always follow them. Otherwise you know, what do

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Speaker 1: they even mean? So this is a bed robed principle

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Speaker 1: of quantum mechanics, and to have an exception at black

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Speaker 1: holes means there might be an exception somewhere else. And

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Speaker 1: basically it means it's not a foundational principle of quantum

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Speaker 1: mechanics that like information can disappear, stuff can be deleted

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Speaker 1: from the universe and you can have no record of

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Speaker 1: it ever having existed. That would just be a pretty

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Speaker 1: different universe from the one we thought we lived in.

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Speaker 1: Would be a catastrophe. We just have to figure out

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Speaker 1: some new theory that accommodates that, and a lot of

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Speaker 1: the assumptions we've been making would be wrong. So that's

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Speaker 1: kind of cool. That's like we say on this podcast

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Speaker 1: all the time, it would be awesome to knock down

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Speaker 1: a basic tenant of physics and discover something new. It's

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Speaker 1: just that that's a pretty big tenant, and so we're

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Speaker 1: pretty skeptical. You're pretty skeptical that there might be exceptions exactly.

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Speaker 1: I mean, it goes right back to the shorting or equation.

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Speaker 1: You know, the shorting or equation is unitary. It says

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Speaker 1: that probability is conserved. If you have a certain amount

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Speaker 1: of probability, it has to go somewhere, It doesn't just disappear.

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Speaker 1: And so that would be kind of weird but also fascinating,

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Speaker 1: like that would be a really interesting place to live,

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Speaker 1: and it wouldn't be the first time in the history

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Speaker 1: of physics that the universe was totally different in a

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Speaker 1: really basic way than the one we imagine. So we're

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Speaker 1: definitely keeping our minds open to that, but considering other

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Speaker 1: possibilities also, Right, all right, well, you say, one potential

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Speaker 1: solution is that maybe the black hole is sort of

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Speaker 1: leaking information when it evaporates like that somehow the evaporating

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Speaker 1: particles somehow carry away some of the information about the

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Speaker 1: black hole. That seems like a pretty good solution. But

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Speaker 1: what's the problem with that idea. Problem with that idea

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Speaker 1: of the event horizon not actually being smooth is that

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Speaker 1: then the information doesn't really go into the black hole.

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Speaker 1: It's just like stuck on the outside of the event

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Speaker 1: horizon so that it can radiate out, but then it

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Speaker 1: doesn't actually go into the black hole. So then you

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Speaker 1: need this like weird firewall, this like region where nothing

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Speaker 1: can actually go. Then like what's actually in the black hole? Right? Nothing?

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Speaker 1: That's sort of weird and require is this really strange

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Speaker 1: boundary that people can't really make sense of. The Other

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Speaker 1: problem with that is that it's hard to reconcile because

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Speaker 1: remember there's two ways to think about things falling into

429
00:23:09,240 --> 00:23:12,240
Speaker 1: a black hole. One from the outside when you're watching,

430
00:23:12,560 --> 00:23:14,480
Speaker 1: and you can never actually see the thing fall in

431
00:23:14,680 --> 00:23:18,000
Speaker 1: because of the gravitational time dilation. It takes infinite time

432
00:23:18,080 --> 00:23:19,960
Speaker 1: to fall in. You never actually see it fall in.

433
00:23:20,280 --> 00:23:22,440
Speaker 1: But the other point of view is from the point

434
00:23:22,440 --> 00:23:24,080
Speaker 1: of view of the thing falling in, and that just

435
00:23:24,200 --> 00:23:27,040
Speaker 1: passes right through the event horizon and heads to the singularity.

436
00:23:27,720 --> 00:23:29,440
Speaker 1: So it doesn't really make sense from the point of

437
00:23:29,520 --> 00:23:32,000
Speaker 1: view of the thing falling in for things to be

438
00:23:32,040 --> 00:23:34,920
Speaker 1: stuck on the event horizon. So it's not really a

439
00:23:35,000 --> 00:23:39,400
Speaker 1: workable solution, all right, I guess I mean trouble understanding

440
00:23:39,600 --> 00:23:42,440
Speaker 1: why exactly are you saying that you can have when

441
00:23:42,480 --> 00:23:46,080
Speaker 1: it evaporates, it can be sort of both coming out

442
00:23:46,160 --> 00:23:48,480
Speaker 1: and coming in at the same time. That's weird. Well,

443
00:23:48,520 --> 00:23:51,480
Speaker 1: it either needs to fall into the black hole or not, right,

444
00:23:51,680 --> 00:23:54,720
Speaker 1: And if it's information is encoded on the outside of

445
00:23:54,720 --> 00:23:57,119
Speaker 1: the event horizon, that means it hasn't really fallen into

446
00:23:57,200 --> 00:23:59,919
Speaker 1: the black hole. It's something like we're preventing it from

447
00:24:00,080 --> 00:24:02,159
Speaker 1: falling into the black hole. So then you need this

448
00:24:02,280 --> 00:24:05,840
Speaker 1: other thing, this firewall, preventing it. But we don't understand

449
00:24:06,080 --> 00:24:08,200
Speaker 1: what that would be or why that would be, and

450
00:24:08,280 --> 00:24:10,680
Speaker 1: it contradicts our view that you can fall into a

451
00:24:10,720 --> 00:24:12,320
Speaker 1: black hole from the point of view of the thing

452
00:24:12,440 --> 00:24:15,760
Speaker 1: falling in. So you need some whole other like idea

453
00:24:15,800 --> 00:24:17,600
Speaker 1: of what a black hole is to make that work.

454
00:24:17,960 --> 00:24:21,600
Speaker 1: So is this whole idea of evaporation theoretical or something

455
00:24:21,680 --> 00:24:25,480
Speaker 1: we understand thoroughly. Evaporation is not something we understand thoroughly,

456
00:24:25,640 --> 00:24:29,600
Speaker 1: and it is theoretical. Like, nobody's ever actually seen Hawking radiation,

457
00:24:30,040 --> 00:24:32,280
Speaker 1: So we say that black holes are not totally black,

458
00:24:32,320 --> 00:24:35,159
Speaker 1: but we've never actually seen one radiate anything. So this

459
00:24:35,359 --> 00:24:38,720
Speaker 1: is purely theoretical, and you know, it's an approximation like

460
00:24:39,000 --> 00:24:41,800
Speaker 1: Hawking did these calculations, but we don't really have a

461
00:24:41,960 --> 00:24:44,480
Speaker 1: theory to back them up. Like we have general relativity,

462
00:24:44,640 --> 00:24:47,080
Speaker 1: we have quantum mechanics, we don't have a theory of

463
00:24:47,200 --> 00:24:50,160
Speaker 1: quantum gravity when the combines the two, and that's really

464
00:24:50,240 --> 00:24:52,800
Speaker 1: what you need when things get both really really small

465
00:24:53,320 --> 00:24:57,240
Speaker 1: and really powerful gravitationally. Currently, we can do quantum mechanics

466
00:24:57,440 --> 00:25:00,520
Speaker 1: by ignoring gravity because gravity is very very small for

467
00:25:00,640 --> 00:25:03,760
Speaker 1: little particles that are affected by quantum mechanics. And when

468
00:25:03,760 --> 00:25:06,600
Speaker 1: we do gravity calculations we can ignore quantum mechanics because

469
00:25:06,680 --> 00:25:09,080
Speaker 1: quantum mechanical effects are small for the kinds of things

470
00:25:09,119 --> 00:25:11,680
Speaker 1: where we do get gravity calculations that are pretty big.

471
00:25:11,920 --> 00:25:14,120
Speaker 1: So inside black holes, we think you need a new

472
00:25:14,240 --> 00:25:17,639
Speaker 1: theory quantum gravity. Stephen Hawking didn't have this theory, but

473
00:25:17,720 --> 00:25:20,320
Speaker 1: it is sort of like a hand wavy calculation where

474
00:25:20,400 --> 00:25:22,840
Speaker 1: added a little bit of quantum mechanics to gravity, and

475
00:25:22,920 --> 00:25:25,240
Speaker 1: he came up with this calculation. But no, we've never

476
00:25:25,400 --> 00:25:28,480
Speaker 1: seen Hawking radiation, so we don't know that it's actually real.

477
00:25:28,840 --> 00:25:30,640
Speaker 1: I see. So when you say that the large Hadron

478
00:25:31,000 --> 00:25:33,760
Speaker 1: collider is producing black holes, but not to worry about it,

479
00:25:33,840 --> 00:25:38,040
Speaker 1: because they just evaporate. That's are you're saying. That's just

480
00:25:38,200 --> 00:25:42,480
Speaker 1: a big maybe there because Stephen Hawking sort of fudgeted. Yeah,

481
00:25:42,520 --> 00:25:44,440
Speaker 1: but the other half of that calculation that it would

482
00:25:44,440 --> 00:25:47,240
Speaker 1: be producing black holes relies on the same calculation. So

483
00:25:47,600 --> 00:25:50,399
Speaker 1: if we're producing them, then they are also evaporating. Oh,

484
00:25:50,480 --> 00:25:54,280
Speaker 1: I see, all right, so maybe it's not producing black holes.

485
00:25:54,400 --> 00:25:57,520
Speaker 1: I see, yeah, exactly. All right, Well then so that

486
00:25:57,600 --> 00:26:00,800
Speaker 1: doesn't work the idea that information can can leak out

487
00:26:00,880 --> 00:26:04,080
Speaker 1: through Hawking radiation. But now there's maybe a new theory

488
00:26:04,160 --> 00:26:06,480
Speaker 1: that could explain this paradox of what happens to the

489
00:26:06,560 --> 00:26:09,400
Speaker 1: information that goes into the black hole. And the approach

490
00:26:09,480 --> 00:26:12,160
Speaker 1: here is to add more quantum mechanics to the calculation,

491
00:26:12,240 --> 00:26:14,920
Speaker 1: to think, like, let's make this more quantum mechanical. Let's

492
00:26:14,960 --> 00:26:17,720
Speaker 1: add another concept and maybe they'll give us some insight.

493
00:26:18,080 --> 00:26:21,040
Speaker 1: And one that's been really appealing for getting information from

494
00:26:21,119 --> 00:26:24,359
Speaker 1: one place to the other is the idea of quantum entanglement.

495
00:26:24,760 --> 00:26:27,360
Speaker 1: We talk about this on the podcast, that two particles,

496
00:26:27,400 --> 00:26:30,480
Speaker 1: if they have a shared history, can have their fates intertwined.

497
00:26:30,840 --> 00:26:32,639
Speaker 1: Like if you have a particle with no spin and

498
00:26:32,680 --> 00:26:35,040
Speaker 1: it makes two particles that do have spin then those

499
00:26:35,040 --> 00:26:37,679
Speaker 1: spins have to be opposite in order to balance. Right,

500
00:26:37,800 --> 00:26:39,840
Speaker 1: you start out with zero spin have to end up

501
00:26:39,840 --> 00:26:42,720
Speaker 1: with zero spin. Quantum mechanics says that those two particles,

502
00:26:42,960 --> 00:26:45,440
Speaker 1: whether they're spin up or down, is not actually determined

503
00:26:45,480 --> 00:26:48,240
Speaker 1: until you measure one of them, So they're entangled even

504
00:26:48,280 --> 00:26:50,640
Speaker 1: if they're far away from each other in the universe.

505
00:26:51,040 --> 00:26:53,200
Speaker 1: So if one is created on Earth and the other

506
00:26:53,240 --> 00:26:55,959
Speaker 1: one is now sent out into space and they're kilometers apart,

507
00:26:56,280 --> 00:26:58,480
Speaker 1: and when you measure one of them, it determines the

508
00:26:58,600 --> 00:27:00,640
Speaker 1: spin at the other because they have to be opposite.

509
00:27:01,080 --> 00:27:03,280
Speaker 1: So that's cool because it feels sort of like a

510
00:27:03,400 --> 00:27:07,200
Speaker 1: way to get information from one place to another without

511
00:27:07,280 --> 00:27:10,000
Speaker 1: actually sending a message, right. It feels sort of like

512
00:27:10,359 --> 00:27:13,560
Speaker 1: this non local information transfer that you might want to

513
00:27:13,640 --> 00:27:16,280
Speaker 1: get information out of a black hole. Oh, I see,

514
00:27:16,320 --> 00:27:18,760
Speaker 1: So is the idea that then when something falls into

515
00:27:18,840 --> 00:27:21,560
Speaker 1: the black hole, it's actually entangled with something else outside

516
00:27:21,600 --> 00:27:24,119
Speaker 1: of it. Exactly. That's sort of the basis of the idea.

517
00:27:24,600 --> 00:27:26,000
Speaker 1: Before we dig into a little bit more, I just

518
00:27:26,040 --> 00:27:28,800
Speaker 1: want to add a caveat that for quantum entanglement, you

519
00:27:28,960 --> 00:27:33,119
Speaker 1: can't actually use entanglement to send information. You need also

520
00:27:33,440 --> 00:27:35,760
Speaker 1: some other sort of mechanism. And a lot of people

521
00:27:35,840 --> 00:27:38,160
Speaker 1: think that quantum entanglement is a way to send information

522
00:27:38,320 --> 00:27:40,359
Speaker 1: faster than the speed of light. But you can't do that.

523
00:27:40,920 --> 00:27:42,760
Speaker 1: But there is an important way that we need to

524
00:27:42,840 --> 00:27:45,280
Speaker 1: think about entanglement in order to attack this black hole

525
00:27:45,280 --> 00:27:49,359
Speaker 1: information paradox problem, and that's the Hawking radiation. Remember, Hawking

526
00:27:49,480 --> 00:27:52,480
Speaker 1: radiation is created when you have a particle antiparticle pair

527
00:27:52,840 --> 00:27:55,520
Speaker 1: created just outside the event horizon. One of them falls

528
00:27:55,560 --> 00:27:58,280
Speaker 1: in idea, another one flies out, which is the Hawking radiation.

529
00:27:58,760 --> 00:28:02,000
Speaker 1: If those two were created together, then they are entangled.

530
00:28:02,080 --> 00:28:04,879
Speaker 1: So now this Hawking radiation is somehow entangled with the

531
00:28:04,960 --> 00:28:08,960
Speaker 1: particle inside the black hole. And that's fascinating because it

532
00:28:09,000 --> 00:28:12,119
Speaker 1: tells you that, like maybe there's information there. Somehow, the

533
00:28:12,160 --> 00:28:15,680
Speaker 1: Hawking radiation has information about what's inside the black hole.

534
00:28:16,119 --> 00:28:19,080
Speaker 1: It's like at the moment of creation, it puts a

535
00:28:19,119 --> 00:28:21,639
Speaker 1: little bit of information into the black hole, but it

536
00:28:21,720 --> 00:28:25,640
Speaker 1: also takes away some information with it in the evaporation. Yeah,

537
00:28:25,680 --> 00:28:29,360
Speaker 1: and it doesn't contradict Hawking calculation. It says, look by itself,

538
00:28:29,440 --> 00:28:31,680
Speaker 1: the Hawking radiation, these particles that fly on from the

539
00:28:31,680 --> 00:28:33,960
Speaker 1: black hole, they don't have any information. You can't look

540
00:28:34,000 --> 00:28:36,359
Speaker 1: at them and tell what was inside the black hole,

541
00:28:36,720 --> 00:28:39,360
Speaker 1: but there might be some correlations there. There might be

542
00:28:39,520 --> 00:28:43,480
Speaker 1: some relationships between the Hawking radiation and what is inside

543
00:28:43,520 --> 00:28:46,040
Speaker 1: the black hole. And you can't tell what's inside the

544
00:28:46,080 --> 00:28:48,680
Speaker 1: black hole just by looking at the Hawking radiation, but

545
00:28:48,840 --> 00:28:51,680
Speaker 1: might be hidden in there. It's sort of like encrypted, right.

546
00:28:52,040 --> 00:28:54,440
Speaker 1: It's like if somebody can see how the computer represents

547
00:28:54,440 --> 00:28:57,640
Speaker 1: your password, but they don't actually know what your password is. Right,

548
00:28:57,880 --> 00:28:59,760
Speaker 1: they can just see those little dots on the screen

549
00:29:00,040 --> 00:29:02,800
Speaker 1: your pathwords in there, but you can't see it. So

550
00:29:03,080 --> 00:29:06,400
Speaker 1: maybe this information is in the Hawking radiation. It is

551
00:29:06,440 --> 00:29:09,960
Speaker 1: just sort of like encrypted by quantum entanglement. Interesting, but

552
00:29:10,240 --> 00:29:13,000
Speaker 1: that applies to the particle that gets evaporated and that

553
00:29:13,120 --> 00:29:15,320
Speaker 1: comes out. But what about my banana that I threw in?

554
00:29:15,600 --> 00:29:18,880
Speaker 1: What happens to my banana information? Oh, that's a good question.

555
00:29:19,120 --> 00:29:21,320
Speaker 1: What happens to your banana information? Well, your banana has

556
00:29:21,360 --> 00:29:24,520
Speaker 1: a quantum history, and so it is entangled with you,

557
00:29:25,000 --> 00:29:27,600
Speaker 1: who threw it in, and so it's much harder to

558
00:29:27,640 --> 00:29:31,440
Speaker 1: talk about quantum mechanics and macroscopic objects like bananas. But

559
00:29:31,560 --> 00:29:34,560
Speaker 1: in principle, your banana is entangled with you, and so

560
00:29:34,920 --> 00:29:36,840
Speaker 1: even if you throw it into the black hole, it's

561
00:29:36,920 --> 00:29:40,160
Speaker 1: information is still connected to you somehow, Like I still

562
00:29:40,240 --> 00:29:43,520
Speaker 1: remember the banana. Is what you're saying exactly, you are

563
00:29:43,640 --> 00:29:47,000
Speaker 1: the hawking radiation. In that case, my dear memories of

564
00:29:47,080 --> 00:29:52,160
Speaker 1: that banana are somehow still preserving the information about in

565
00:29:52,400 --> 00:29:54,400
Speaker 1: the years. Is that true? Is that kind of what

566
00:29:54,480 --> 00:29:57,000
Speaker 1: this new solution is about. It's just that you know,

567
00:29:57,160 --> 00:29:59,400
Speaker 1: everything is entangled with each other and so you never

568
00:29:59,520 --> 00:30:01,320
Speaker 1: really lo is it when it goes into the black hole?

569
00:30:01,400 --> 00:30:03,840
Speaker 1: Is that the basic outline of the solution. That's not

570
00:30:03,960 --> 00:30:06,200
Speaker 1: the solution. It's another way to look at the problem

571
00:30:06,280 --> 00:30:08,760
Speaker 1: because it doesn't actually solve the problem. It just sort

572
00:30:08,800 --> 00:30:10,520
Speaker 1: of restates it. But it restates in a way that

573
00:30:10,600 --> 00:30:13,040
Speaker 1: we then can attack. And here's why it's not actually

574
00:30:13,040 --> 00:30:15,400
Speaker 1: a solution to the problem. Think about what happens as

575
00:30:15,480 --> 00:30:18,280
Speaker 1: the black hole evaporates. As the black hole gets smaller

576
00:30:18,320 --> 00:30:20,640
Speaker 1: and smaller, you have all this hawking radiation that was

577
00:30:20,720 --> 00:30:24,120
Speaker 1: created entangled with stuff inside the black hole. But now

578
00:30:24,200 --> 00:30:27,480
Speaker 1: the black hole is disappearing, So where is that entanglement going.

579
00:30:27,960 --> 00:30:30,600
Speaker 1: Then the hawking radiation is like entangled with something that

580
00:30:30,680 --> 00:30:34,560
Speaker 1: has disappeared, and so you sort of have the same problem, right,

581
00:30:34,720 --> 00:30:37,200
Speaker 1: it's just sort of stated in a different way. So

582
00:30:37,520 --> 00:30:39,400
Speaker 1: what we need is a way to figure out how

583
00:30:39,640 --> 00:30:42,440
Speaker 1: entanglement for a black hole can start at zero, and

584
00:30:42,520 --> 00:30:45,480
Speaker 1: then during the black hole's lifetime it can grow. As

585
00:30:45,520 --> 00:30:48,440
Speaker 1: it's evaporating, it's giving off Hawking radiation, which is now

586
00:30:48,480 --> 00:30:51,560
Speaker 1: getting entangled with the stuff inside of it somehow. Then

587
00:30:51,880 --> 00:30:54,440
Speaker 1: that entanglement has to get back down to zero. All

588
00:30:54,480 --> 00:30:58,000
Speaker 1: those entanglements have to get broken or somehow resolved before

589
00:30:58,080 --> 00:31:00,920
Speaker 1: the black hole evaporates. So that's this newer way of

590
00:31:01,040 --> 00:31:03,840
Speaker 1: looking at the problem. This way that one of Hawking students,

591
00:31:03,920 --> 00:31:05,880
Speaker 1: Don Page came up with, and that's sort of the

592
00:31:05,960 --> 00:31:08,640
Speaker 1: crevice that these new groups attacked in order trying to

593
00:31:08,720 --> 00:31:11,160
Speaker 1: figure out what's going on. Oh I see it is

594
00:31:11,240 --> 00:31:14,800
Speaker 1: that like I'm entangled to my banana. I remember it fondly.

595
00:31:15,280 --> 00:31:18,120
Speaker 1: I remember the curvature and the just how many spots

596
00:31:18,160 --> 00:31:20,800
Speaker 1: and how sweet it was, Oh banana, I eat eu well.

597
00:31:21,440 --> 00:31:23,480
Speaker 1: And so then the banana goes into the black hole.

598
00:31:24,400 --> 00:31:28,360
Speaker 1: Inside the black hole, it gets entangled with particles being evaporated,

599
00:31:28,880 --> 00:31:31,920
Speaker 1: which means that the you know, evaporating particle that comes

600
00:31:31,960 --> 00:31:35,720
Speaker 1: out is somehow entangled to the banana which was entangled

601
00:31:35,800 --> 00:31:38,640
Speaker 1: to me. Yeah, Or more directly, if you throw it

602
00:31:38,720 --> 00:31:41,360
Speaker 1: into the black hole, you are still entangled with that banana.

603
00:31:41,520 --> 00:31:43,840
Speaker 1: You don't need hawking radiation for that. But then your

604
00:31:43,880 --> 00:31:46,520
Speaker 1: information about the bananas somehow in the black hole, right,

605
00:31:47,040 --> 00:31:49,960
Speaker 1: and then as the black hole is evaporating, you wonder,

606
00:31:50,080 --> 00:31:53,440
Speaker 1: like what happens to that entanglement? Instead of thinking about

607
00:31:53,480 --> 00:31:55,960
Speaker 1: like this information stuck inside the black hole, think about

608
00:31:56,000 --> 00:31:58,760
Speaker 1: in terms of the entanglement, how can I be entangled

609
00:31:58,800 --> 00:32:01,120
Speaker 1: with something which is then just appearing. Where does that

610
00:32:01,320 --> 00:32:05,120
Speaker 1: entanglement go? Does the entanglement and gets passed onto the

611
00:32:05,160 --> 00:32:08,120
Speaker 1: evaporating particle? Is that the idea? That's the question, right,

612
00:32:08,360 --> 00:32:11,600
Speaker 1: how do you somehow go from having entanglement to getting

613
00:32:11,720 --> 00:32:14,960
Speaker 1: zero entanglement? Like, the black hole is definitely creating entangled

614
00:32:15,000 --> 00:32:17,480
Speaker 1: pairs because things are falling into the black hole and

615
00:32:17,560 --> 00:32:21,400
Speaker 1: they are entangled with whatever they came from hawking radiation

616
00:32:21,520 --> 00:32:24,040
Speaker 1: or Jorge throwing a banana, And the question is then

617
00:32:24,360 --> 00:32:26,440
Speaker 1: how do you get a black hole to break those

618
00:32:26,560 --> 00:32:30,200
Speaker 1: entanglements somehow? All right, so then it's somehow preserved and

619
00:32:30,280 --> 00:32:33,080
Speaker 1: so what's been the progress in the last year. So

620
00:32:33,240 --> 00:32:36,040
Speaker 1: a bunch of smart young theories attack this problem and

621
00:32:36,160 --> 00:32:38,760
Speaker 1: they came up with a new way to do this calculation. See,

622
00:32:38,800 --> 00:32:41,720
Speaker 1: the problem is that nobody knows even how to calculate

623
00:32:41,800 --> 00:32:44,360
Speaker 1: this entanglement. Like we say, entanglement has a start from

624
00:32:44,440 --> 00:32:46,240
Speaker 1: zero for a black hole, that it has to grow,

625
00:32:46,520 --> 00:32:48,680
Speaker 1: that it has to come back down to zero. Problem is,

626
00:32:48,720 --> 00:32:50,840
Speaker 1: we don't have a theory of quantum gravity, so we

627
00:32:50,920 --> 00:32:54,520
Speaker 1: don't understand how to calculate entanglement, which is a quantum concept,

628
00:32:54,680 --> 00:32:56,440
Speaker 1: in the environment of a black hole, which is a

629
00:32:56,480 --> 00:32:59,320
Speaker 1: gravitational concept. So until now, nobody even knew like how

630
00:32:59,400 --> 00:33:01,080
Speaker 1: do we calculate this thing. We know it has to

631
00:33:01,120 --> 00:33:03,040
Speaker 1: start a zero, go up and come down, but we

632
00:33:03,080 --> 00:33:04,880
Speaker 1: don't know how to calculate it. So what they did

633
00:33:05,000 --> 00:33:07,680
Speaker 1: is they came up with a clever new approach theoretically

634
00:33:07,800 --> 00:33:10,400
Speaker 1: to do this calculation. And if you read their papers,

635
00:33:10,480 --> 00:33:13,840
Speaker 1: it's like a bunch of crazy mathematical tricks they do.

636
00:33:14,200 --> 00:33:16,360
Speaker 1: They take the problem, they transform into something else and

637
00:33:16,360 --> 00:33:18,600
Speaker 1: they apply this tool and they put in wormholes and

638
00:33:18,680 --> 00:33:22,200
Speaker 1: they do this calculation. It's like a real like tourtive

639
00:33:22,280 --> 00:33:26,040
Speaker 1: force of mathematical tricks. And what they've done is they

640
00:33:26,120 --> 00:33:29,600
Speaker 1: figured out a way to sort of calculate the entanglement

641
00:33:29,680 --> 00:33:33,480
Speaker 1: of this black hole over its lifetime. And in their calculation,

642
00:33:33,600 --> 00:33:37,080
Speaker 1: they see the entanglement going up, peeking, and then coming

643
00:33:37,160 --> 00:33:39,680
Speaker 1: back down. Interesting, what do you mean they put in

644
00:33:39,760 --> 00:33:41,760
Speaker 1: some wormholes. You can just do that. You can sprinkle

645
00:33:41,840 --> 00:33:46,800
Speaker 1: in some wormholes. Yeah, exactly. They use wormholes as just

646
00:33:46,920 --> 00:33:48,960
Speaker 1: a sort of a way to do these calculations. You know,

647
00:33:49,360 --> 00:33:51,600
Speaker 1: sometimes you attack a math problem, you don't know how

648
00:33:51,640 --> 00:33:53,680
Speaker 1: to do it, so you transform it into something else.

649
00:33:54,120 --> 00:33:56,400
Speaker 1: And so what they did is they transformed the problem

650
00:33:56,640 --> 00:33:58,920
Speaker 1: from one kind of problem into another one where they

651
00:33:58,960 --> 00:34:01,320
Speaker 1: could use wormholes that they knew how to calculate. I

652
00:34:01,320 --> 00:34:03,360
Speaker 1: don't know how to integrate this thing, but I'll transform

653
00:34:03,400 --> 00:34:05,480
Speaker 1: into this other thing that I do know how to integrate.

654
00:34:05,640 --> 00:34:07,400
Speaker 1: There's a lot of details there about how they did

655
00:34:07,440 --> 00:34:11,800
Speaker 1: this calculation. For example, nobody knows how to calculate entanglement

656
00:34:12,160 --> 00:34:15,399
Speaker 1: in four dimensional space with gravity. So they did two things.

657
00:34:15,480 --> 00:34:17,520
Speaker 1: When they said, well, let's just take it down a

658
00:34:17,600 --> 00:34:20,400
Speaker 1: couple of notches and think about, you know, two dimensional

659
00:34:20,480 --> 00:34:23,560
Speaker 1: black holes instead of four dimensional black holes. Does that

660
00:34:23,640 --> 00:34:25,840
Speaker 1: mean that you have to assume that there are wormholes

661
00:34:25,840 --> 00:34:28,400
Speaker 1: inside of the black hole. These wormholes are more of

662
00:34:28,440 --> 00:34:31,480
Speaker 1: a mathematical trick than actual physical wormholes. But in a

663
00:34:31,520 --> 00:34:33,600
Speaker 1: minute we could talk about what the solution means and

664
00:34:33,719 --> 00:34:37,000
Speaker 1: whether they're actually are wormholes connecting the inside of the

665
00:34:37,040 --> 00:34:39,319
Speaker 1: black hole to the outside. But for now, just think

666
00:34:39,360 --> 00:34:41,719
Speaker 1: of a sort of a mathematical trick that they did

667
00:34:41,960 --> 00:34:44,120
Speaker 1: in order to get to a number. And the thing

668
00:34:44,200 --> 00:34:47,560
Speaker 1: to understand about this calculation is like, they don't understand

669
00:34:48,000 --> 00:34:50,040
Speaker 1: how the information is getting out. It's not like they

670
00:34:50,080 --> 00:34:52,279
Speaker 1: found some mechanism where they're like, oh, look, here's some

671
00:34:52,360 --> 00:34:54,600
Speaker 1: little holes in the event horizon. They just figured out

672
00:34:54,640 --> 00:34:56,800
Speaker 1: a way to do this calculation and it has the

673
00:34:56,960 --> 00:35:00,920
Speaker 1: shape they expected to have. If black holes are leaking information,

674
00:35:01,280 --> 00:35:03,759
Speaker 1: that doesn't mean they know how it's happening. It's like

675
00:35:03,840 --> 00:35:06,759
Speaker 1: if you see your fridge temperature is rising, you don't

676
00:35:06,800 --> 00:35:08,800
Speaker 1: necessarily know where the leak is in your fridge. You

677
00:35:08,880 --> 00:35:12,879
Speaker 1: just know that somehow somewhere heat is getting in. I see.

678
00:35:13,040 --> 00:35:16,200
Speaker 1: The solution also sort of supposes that black holes are

679
00:35:16,280 --> 00:35:21,080
Speaker 1: not perfectly smooth inside. Right, there's some crazy interpretation of

680
00:35:21,160 --> 00:35:24,600
Speaker 1: these calculations, and I say interpretation, because these calculations are

681
00:35:24,640 --> 00:35:28,560
Speaker 1: their mathematical and how they relate to physicality is complicated,

682
00:35:28,960 --> 00:35:31,759
Speaker 1: and the cosmologist I talked to really disagree about whether

683
00:35:31,840 --> 00:35:35,240
Speaker 1: you can make any physical interpretation about like what's happening,

684
00:35:35,320 --> 00:35:38,640
Speaker 1: because sometimes this information exists in this sort of abstract

685
00:35:38,719 --> 00:35:41,440
Speaker 1: space we call Hilbert space for quantum mechanics, not in

686
00:35:41,520 --> 00:35:44,240
Speaker 1: a physical space, but there is sort of a cartoon

687
00:35:44,360 --> 00:35:46,680
Speaker 1: picture that you can draw to try to get an

688
00:35:46,760 --> 00:35:50,080
Speaker 1: understanding of what's going on, and it involves really crazy

689
00:35:50,200 --> 00:35:53,720
Speaker 1: things like perhaps inside the black hole, it's not actually

690
00:35:53,800 --> 00:35:57,640
Speaker 1: all black hole. Maybe there's like an island inside the

691
00:35:57,719 --> 00:36:02,000
Speaker 1: black hole where radiation can fall, and it's sort of

692
00:36:02,320 --> 00:36:04,480
Speaker 1: no longer part of the black hole. It's part of

693
00:36:04,520 --> 00:36:09,200
Speaker 1: this like quantum radiation island. It's physically inside the black hole.

694
00:36:09,239 --> 00:36:11,360
Speaker 1: But now the black hole, instead of being like a sphere,

695
00:36:11,840 --> 00:36:13,600
Speaker 1: is sort of like a shell. You know, it has

696
00:36:13,640 --> 00:36:16,239
Speaker 1: like a hollow core, and that hollow core is not

697
00:36:16,480 --> 00:36:21,279
Speaker 1: black holy anymore. What Yeah, Well, how can a black

698
00:36:21,320 --> 00:36:23,480
Speaker 1: hole not be a black hole? Inside of a black hole,

699
00:36:24,520 --> 00:36:27,080
Speaker 1: it's a double decker, it's like multilayer. So the idea

700
00:36:27,120 --> 00:36:29,759
Speaker 1: is that like it's just like a normal classical black

701
00:36:29,800 --> 00:36:32,080
Speaker 1: hole in the shell part, but then the core of

702
00:36:32,160 --> 00:36:34,960
Speaker 1: it has this other weird quantum gravity thing going on

703
00:36:35,080 --> 00:36:37,800
Speaker 1: that we don't yet understand. But we think that maybe

704
00:36:37,960 --> 00:36:41,040
Speaker 1: stuff inside the black hole is like falling into this

705
00:36:41,160 --> 00:36:45,120
Speaker 1: quantum island, and that quantum island is entangled with the

706
00:36:45,160 --> 00:36:47,359
Speaker 1: stuff that has come out, and so this is how

707
00:36:47,440 --> 00:36:49,960
Speaker 1: things can like sort of leave the black hole without

708
00:36:50,040 --> 00:36:53,799
Speaker 1: passing through the classical event horizon. Again, people disagree about

709
00:36:53,800 --> 00:36:56,200
Speaker 1: whether this is like a cartoon picture just for sort

710
00:36:56,200 --> 00:36:59,800
Speaker 1: of understanding the calculations, or what's really going on inside

711
00:36:59,840 --> 00:37:02,680
Speaker 1: a black hole. All right, well, let's get into what

712
00:37:02,960 --> 00:37:06,520
Speaker 1: this potential solution might actually mean, like have we actually

713
00:37:06,600 --> 00:37:10,240
Speaker 1: solved the paradox or are we still a long ways away?

714
00:37:10,560 --> 00:37:26,240
Speaker 1: But first let's take a quick break. All right, Daniel,

715
00:37:26,320 --> 00:37:30,080
Speaker 1: it sounds like maybe they have a new way to attack,

716
00:37:30,360 --> 00:37:35,319
Speaker 1: finding a potential solution to a potentially imaginary, not quite

717
00:37:35,400 --> 00:37:39,719
Speaker 1: sure paradox about black holes. Right, Did I get that right? Yeah?

718
00:37:39,760 --> 00:37:42,279
Speaker 1: I think you did. There's enough qualifiers there. You know,

719
00:37:42,360 --> 00:37:45,399
Speaker 1: this is exciting because people for a long time thought

720
00:37:45,440 --> 00:37:47,960
Speaker 1: we wouldn't make progress on this for decades until we

721
00:37:48,080 --> 00:37:50,279
Speaker 1: came up with a theory of quantum gravity. How can

722
00:37:50,360 --> 00:37:52,560
Speaker 1: we even calculate the level of the entanglement of the

723
00:37:52,640 --> 00:37:54,759
Speaker 1: inside of the black hole and the outside of the

724
00:37:54,760 --> 00:37:57,920
Speaker 1: black hole if we can't do quantum gravity calculations. So

725
00:37:58,120 --> 00:38:01,640
Speaker 1: this is exciting, but it's not exactly like a full answer, right.

726
00:38:01,680 --> 00:38:04,280
Speaker 1: It's sort of like we were able to without coming

727
00:38:04,360 --> 00:38:06,640
Speaker 1: up with the theory quantum gravity. We still don't have one.

728
00:38:06,920 --> 00:38:10,239
Speaker 1: We were able to do this one calculation, and that

729
00:38:10,360 --> 00:38:14,440
Speaker 1: calculation says something amazing. It says that the entanglement decreases,

730
00:38:14,800 --> 00:38:17,960
Speaker 1: and it's a special moment halfway through the lifetime of

731
00:38:18,040 --> 00:38:21,000
Speaker 1: a black hole when the entanglement just starts to drop.

732
00:38:21,480 --> 00:38:24,239
Speaker 1: It's like the midlife crisis of a black hole. And

733
00:38:24,719 --> 00:38:27,799
Speaker 1: that suggests if this calculation is correct, then it means

734
00:38:27,840 --> 00:38:30,960
Speaker 1: what we think. It means that information does leak out

735
00:38:31,080 --> 00:38:33,200
Speaker 1: of black holes. The things you throw into a black

736
00:38:33,239 --> 00:38:35,920
Speaker 1: hole are not lost forever. That's when the black hole

737
00:38:35,960 --> 00:38:39,640
Speaker 1: gets desperate and absorbs a Ferrari or something and expensive

738
00:38:39,640 --> 00:38:42,080
Speaker 1: sports car or something. Yeah, where it leaks out of

739
00:38:42,160 --> 00:38:45,080
Speaker 1: Ferrari right exactly. It's been hoarding its stuff for all

740
00:38:45,120 --> 00:38:47,160
Speaker 1: of its lifetime and then it decides, oh my God,

741
00:38:47,200 --> 00:38:49,960
Speaker 1: I gotta spend all this mass before I evaporate, and

742
00:38:50,080 --> 00:38:52,680
Speaker 1: it starts leaking up bananas and Ferrari's and everything. I

743
00:38:52,719 --> 00:38:55,960
Speaker 1: guess this idea that black holes have a lifespan depend

744
00:38:56,160 --> 00:38:59,960
Speaker 1: on the idea that black holes at some point stop

745
00:39:00,120 --> 00:39:02,399
Speaker 1: eating stuff, right, Like, you have to starve a black

746
00:39:02,440 --> 00:39:06,160
Speaker 1: hole for it to disappear. Oh, absolutely, yeah. This is

747
00:39:06,239 --> 00:39:08,160
Speaker 1: only the case of an isolated black hole. If you

748
00:39:08,280 --> 00:39:10,640
Speaker 1: kept feeding a black hole, it would just keep growing.

749
00:39:11,160 --> 00:39:12,640
Speaker 1: This is what would happen if you had a really

750
00:39:12,680 --> 00:39:15,160
Speaker 1: big black hole and then you left it totally isolated.

751
00:39:15,320 --> 00:39:19,120
Speaker 1: General relativity says it will sit there forever. Quantum mechanical

752
00:39:19,200 --> 00:39:23,000
Speaker 1: modifications to general relativity by Stephen Hawking say no, actually,

753
00:39:23,080 --> 00:39:26,080
Speaker 1: they will radiate a little bit, leak out mass, and

754
00:39:26,280 --> 00:39:30,279
Speaker 1: eventually disappear and evaporate in a blinding flash of light

755
00:39:30,320 --> 00:39:33,400
Speaker 1: at the very end. Because the evaporation happens more quickly

756
00:39:33,520 --> 00:39:36,440
Speaker 1: for small black holes, so you get more evaporation near

757
00:39:36,520 --> 00:39:38,480
Speaker 1: the end of the life So the beginning of the

758
00:39:38,560 --> 00:39:40,680
Speaker 1: life cycle like a little bit. But then as the

759
00:39:40,680 --> 00:39:43,480
Speaker 1: black hole shrinks and shrinks, it gets brighter and brighter,

760
00:39:43,640 --> 00:39:45,919
Speaker 1: all right, So then this potential solution says that maybe

761
00:39:46,239 --> 00:39:49,680
Speaker 1: information is not completely destroyed. It sounds like the idea said,

762
00:39:49,840 --> 00:39:53,040
Speaker 1: you throw a banana in. The banana SML falls into

763
00:39:53,200 --> 00:39:56,600
Speaker 1: a pocket of non black holiness inside of the black hole,

764
00:39:57,000 --> 00:39:59,920
Speaker 1: in which it could get maybe entangled with a particle

765
00:40:00,040 --> 00:40:03,600
Speaker 1: that's evaporating from the black hole. Therefore, then the evaporating

766
00:40:03,640 --> 00:40:06,080
Speaker 1: particle it still carries a little bit of the banana

767
00:40:06,239 --> 00:40:08,920
Speaker 1: with it, Yeah, exactly. And they don't really have an

768
00:40:09,000 --> 00:40:11,719
Speaker 1: understanding at all for how this information leaks out, Like

769
00:40:12,040 --> 00:40:14,279
Speaker 1: as you say, the banana falls in, it's entangled with

770
00:40:14,440 --> 00:40:19,120
Speaker 1: you somehow. That banana's information then moves from the pure

771
00:40:19,200 --> 00:40:22,640
Speaker 1: black hole state into this weird quantum island, and so

772
00:40:22,760 --> 00:40:25,480
Speaker 1: it's not really counted as part of the black hole anymore.

773
00:40:25,920 --> 00:40:28,239
Speaker 1: And then as the black hole is evaporating, is a

774
00:40:28,320 --> 00:40:31,240
Speaker 1: shell now and it's just basically shrinks down to surround

775
00:40:31,320 --> 00:40:33,759
Speaker 1: this quantum island and then disappears, and so then all

776
00:40:33,800 --> 00:40:37,320
Speaker 1: that information is still there. Again, cosmologists are really hesitant

777
00:40:37,360 --> 00:40:41,160
Speaker 1: to like tie the location of this information with anything physical,

778
00:40:41,600 --> 00:40:43,800
Speaker 1: So there are some really tricky questions here, and so

779
00:40:44,040 --> 00:40:45,840
Speaker 1: I reached out to one of the theorists who is

780
00:40:45,920 --> 00:40:48,360
Speaker 1: actively working on these problems and has been involved in

781
00:40:48,440 --> 00:40:51,600
Speaker 1: some of this recent progress. Professor Netta inglehearted m I

782
00:40:51,680 --> 00:40:54,240
Speaker 1: t to tell us a little bit more about it. Netta,

783
00:40:54,320 --> 00:40:57,120
Speaker 1: thank you very much for joining us pleasure, thank you

784
00:40:57,160 --> 00:40:59,680
Speaker 1: for having me. So. My first question is I think

785
00:40:59,719 --> 00:41:02,600
Speaker 1: we've I think at a mental picture, if possible, of

786
00:41:02,719 --> 00:41:06,000
Speaker 1: what happens when halfway through the life of the black

787
00:41:06,080 --> 00:41:10,520
Speaker 1: hole the entropy suddenly starts to decrease. Your papers talk

788
00:41:10,560 --> 00:41:14,399
Speaker 1: about this quantum extremal surface that divides the black hole

789
00:41:14,480 --> 00:41:16,719
Speaker 1: into these two regions. Can you tell us a little

790
00:41:16,719 --> 00:41:19,279
Speaker 1: bit about this surface, how it appears, and then what

791
00:41:19,440 --> 00:41:21,480
Speaker 1: the two regions are like. Is it possible to get

792
00:41:21,480 --> 00:41:25,160
Speaker 1: a mental picture? I can certainly try. So let me

793
00:41:25,280 --> 00:41:28,920
Speaker 1: maybe say a few words about what a quantum extremal

794
00:41:29,000 --> 00:41:31,719
Speaker 1: surface is and what what maybe starting with what we

795
00:41:31,800 --> 00:41:35,040
Speaker 1: mean by an extremal surface to begin with, So, why

796
00:41:35,080 --> 00:41:37,120
Speaker 1: does an extremal surface why do we call it an

797
00:41:37,160 --> 00:41:42,240
Speaker 1: extremal surface. So an extremal surface is a surface whose

798
00:41:42,360 --> 00:41:46,480
Speaker 1: area doesn't change when you jiggle it a little bit.

799
00:41:47,239 --> 00:41:51,520
Speaker 1: So if you slightly, ever so slightly modify the location

800
00:41:51,600 --> 00:41:54,600
Speaker 1: of the surface just a little bit, then the area

801
00:41:54,680 --> 00:41:57,480
Speaker 1: of the surface does not change. Now, where does this

802
00:41:57,600 --> 00:42:01,400
Speaker 1: quantum bit come in. What is that quantum extreme more surface. Well,

803
00:42:01,440 --> 00:42:04,759
Speaker 1: it's a little bit like a quantum corrected area. So

804
00:42:05,120 --> 00:42:08,520
Speaker 1: what is the quantum corrected area like the area plus

805
00:42:08,800 --> 00:42:13,120
Speaker 1: a contribution from from quantum fields, a contribution from the

806
00:42:13,360 --> 00:42:17,040
Speaker 1: entropy of of quantum fields that are just living in

807
00:42:17,160 --> 00:42:21,080
Speaker 1: your universe, and a quantum extremal surface is kind of

808
00:42:21,200 --> 00:42:23,960
Speaker 1: what it sounds like. It means that the sum of

809
00:42:24,120 --> 00:42:28,040
Speaker 1: the area of the surface with the entropy of of

810
00:42:28,280 --> 00:42:32,240
Speaker 1: quantum fields, this quantum contribution to the area's count corrected

811
00:42:32,320 --> 00:42:36,759
Speaker 1: area doesn't change when you slightly jiggle the location of

812
00:42:36,880 --> 00:42:40,680
Speaker 1: this surface. So that's the sort of definition of a

813
00:42:40,920 --> 00:42:44,560
Speaker 1: quantum extremal surface. And so indeed, in the black hole

814
00:42:44,640 --> 00:42:48,680
Speaker 1: information paradox and the recent developments, what we have found

815
00:42:49,360 --> 00:42:53,600
Speaker 1: is that the difference between extrememal and quantum extreme all

816
00:42:54,120 --> 00:42:58,000
Speaker 1: is exactly what it takes two allow us to see

817
00:42:58,120 --> 00:43:02,720
Speaker 1: the signature of information conservation. It is this critical difference

818
00:43:02,760 --> 00:43:06,640
Speaker 1: between whether the area can be increasing even though the

819
00:43:06,920 --> 00:43:10,520
Speaker 1: overall quantum corrective area is not. That is this this

820
00:43:10,680 --> 00:43:15,319
Speaker 1: critical and new ingredient in a very frazy new developments

821
00:43:15,360 --> 00:43:17,960
Speaker 1: over the past two years that have been some sense

822
00:43:18,080 --> 00:43:21,719
Speaker 1: in a renaissance in the in the black hole information paradox.

823
00:43:22,200 --> 00:43:24,279
Speaker 1: Can we think of this as a physical surface or

824
00:43:24,320 --> 00:43:27,600
Speaker 1: is this sort of like an intellectual dividing point for

825
00:43:27,760 --> 00:43:30,440
Speaker 1: using New Year calculations? Is that a real physical thing

826
00:43:30,480 --> 00:43:32,960
Speaker 1: where the space is different inside and outside the surface.

827
00:43:33,239 --> 00:43:35,200
Speaker 1: It's a real physical surface in the sisse that it

828
00:43:35,280 --> 00:43:38,360
Speaker 1: lives in spacetime. It's physical in another way, which is

829
00:43:38,400 --> 00:43:40,960
Speaker 1: also nice, and that if you had a family of

830
00:43:41,040 --> 00:43:45,520
Speaker 1: observers who were sitting closely spaced along the surface, and

831
00:43:45,640 --> 00:43:48,800
Speaker 1: they were able to each of them could measure what

832
00:43:49,200 --> 00:43:51,719
Speaker 1: light rays are doing at the surface. So, in other words,

833
00:43:51,760 --> 00:43:53,640
Speaker 1: if you had a ball and he had observers all

834
00:43:53,680 --> 00:43:55,440
Speaker 1: around the ball, and each one of them measured in

835
00:43:55,480 --> 00:43:59,239
Speaker 1: their own the own little small neighborhood, whether light rays

836
00:43:59,280 --> 00:44:02,360
Speaker 1: are expanding or away from the ball or contracting, and

837
00:44:02,440 --> 00:44:04,960
Speaker 1: you put all those observations together, you would be able

838
00:44:05,040 --> 00:44:08,400
Speaker 1: to tell this is a quantum extremal surface. So this

839
00:44:08,560 --> 00:44:12,080
Speaker 1: is something which is in principle observable the location of

840
00:44:12,160 --> 00:44:15,520
Speaker 1: that surface. Of course, we expect that if you're seeing

841
00:44:15,640 --> 00:44:19,040
Speaker 1: a quantum extremal surface, it is already too late to

842
00:44:19,160 --> 00:44:22,239
Speaker 1: communicate that to someone who is standing outside of the

843
00:44:22,280 --> 00:44:25,640
Speaker 1: black hole. So then, how does this quantum extremeal surface

844
00:44:25,840 --> 00:44:29,839
Speaker 1: help us understand the decrease in entanglement of the black

845
00:44:29,920 --> 00:44:32,320
Speaker 1: hole the interior of the black hole, with the Hawking

846
00:44:32,360 --> 00:44:34,520
Speaker 1: rediation already produced in the first half of the black

847
00:44:34,560 --> 00:44:38,560
Speaker 1: hole's lifetime, does it break that entanglement or do later

848
00:44:38,719 --> 00:44:41,640
Speaker 1: particles now get entangled with earlier particles? How does the

849
00:44:41,719 --> 00:44:45,400
Speaker 1: entanglement actually decrease? That's an excellent question. How do we

850
00:44:45,600 --> 00:44:49,520
Speaker 1: actually understand the way in which information gets out? I

851
00:44:49,600 --> 00:44:51,320
Speaker 1: think this is what you're really asking, how do we

852
00:44:51,360 --> 00:44:55,600
Speaker 1: actually understand the entanglement entropy? And the fact of the

853
00:44:55,680 --> 00:44:58,280
Speaker 1: matter is that we now have two ways of computing

854
00:44:58,600 --> 00:45:03,120
Speaker 1: the entanglement entropy of hawk mediation, either Hawking's original calculation,

855
00:45:03,320 --> 00:45:06,200
Speaker 1: which tells you that you have information loss, or the

856
00:45:06,280 --> 00:45:10,880
Speaker 1: quantum extremal surface prescription, which keeps you information conservation. The

857
00:45:10,960 --> 00:45:15,799
Speaker 1: quantum extremal surface prescription has some grounding in the holographic correspondence.

858
00:45:16,400 --> 00:45:20,800
Speaker 1: It has derivations coming from the holographic correspondence, which is

859
00:45:20,920 --> 00:45:25,280
Speaker 1: very well motivated, but nevertheless still like conjecture, And in particular,

860
00:45:25,480 --> 00:45:27,959
Speaker 1: when I say that not thinking that it might be wrong,

861
00:45:28,480 --> 00:45:31,400
Speaker 1: but thinking that we don't have a derivation of it,

862
00:45:32,000 --> 00:45:35,200
Speaker 1: and so it is difficult to put on the same

863
00:45:35,239 --> 00:45:39,160
Speaker 1: footing Hawkings calculation and the quantum extremal surface prescription and

864
00:45:39,239 --> 00:45:42,719
Speaker 1: simply ask where did Hawking go wrong? Because right now

865
00:45:42,840 --> 00:45:46,520
Speaker 1: we have two completely different calculations of the same thing

866
00:45:46,680 --> 00:45:49,279
Speaker 1: that don't talk to each other, and we don't know

867
00:45:49,360 --> 00:45:52,760
Speaker 1: how to poured over those insights from the quantum extremal

868
00:45:52,840 --> 00:45:57,120
Speaker 1: surface prescription into the same model that Hawking was working with.

869
00:45:57,920 --> 00:45:59,320
Speaker 1: Now I say we don't know how to do that,

870
00:45:59,480 --> 00:46:02,280
Speaker 1: but I should also say that's a very active area

871
00:46:02,520 --> 00:46:06,160
Speaker 1: of investigation. So given how quickly thinks have moved in

872
00:46:06,200 --> 00:46:09,320
Speaker 1: the past couple of years, I expect that our ignorance

873
00:46:09,360 --> 00:46:11,759
Speaker 1: of this is not going to last much longer. All right,

874
00:46:11,840 --> 00:46:14,520
Speaker 1: So do you have like a cartoony picture in your

875
00:46:14,600 --> 00:46:17,400
Speaker 1: mind of you know, what's happening to these particles? You know,

876
00:46:17,520 --> 00:46:21,359
Speaker 1: I understand it's not easy to transport your calculation from

877
00:46:21,680 --> 00:46:25,160
Speaker 1: one regime into this this sort of picture that we

878
00:46:25,200 --> 00:46:26,920
Speaker 1: have in our heads. But what picture do you have

879
00:46:27,040 --> 00:46:28,960
Speaker 1: in your mind when you think about where the information

880
00:46:29,120 --> 00:46:33,000
Speaker 1: is going? Where the information is going is complicated, but

881
00:46:33,239 --> 00:46:37,560
Speaker 1: I can tell you what my opinion is on what's

882
00:46:38,040 --> 00:46:42,680
Speaker 1: missing from say, Hawking circulation that's included in the quantum

883
00:46:42,719 --> 00:46:45,480
Speaker 1: extremal surface calculation. And I should preface this by saying

884
00:46:45,640 --> 00:46:48,600
Speaker 1: that this is a wild speculation that is not at

885
00:46:48,680 --> 00:46:52,000
Speaker 1: all currently back by anything that I have derived or done,

886
00:46:52,200 --> 00:46:56,360
Speaker 1: which is that there's a very beautiful paper by Harlowe

887
00:46:56,400 --> 00:46:59,880
Speaker 1: and Hayden in which they discussed how complicated it is

888
00:47:00,000 --> 00:47:03,680
Speaker 1: to decode the Hawking radiation, and then the assumption that

889
00:47:04,040 --> 00:47:07,960
Speaker 1: Hawking radiation it does sort of purify itself, so at

890
00:47:07,960 --> 00:47:12,200
Speaker 1: the end the information is conserved in the process. Then

891
00:47:12,480 --> 00:47:16,440
Speaker 1: it's still i would say, exponentially difficult in terms of

892
00:47:16,480 --> 00:47:22,720
Speaker 1: computational complexity to decode the Hawking radiation, to understand exactly

893
00:47:23,000 --> 00:47:28,320
Speaker 1: to see unitarities exponentially complicated. We might speculate that Hawking

894
00:47:28,480 --> 00:47:34,319
Speaker 1: calculation in some sense did not include those exponentially complicated

895
00:47:34,840 --> 00:47:39,360
Speaker 1: operations exponentially complicated information. When you look at Hawking calculation,

896
00:47:39,440 --> 00:47:42,120
Speaker 1: do you see the team missed anything? Now, so then

897
00:47:42,160 --> 00:47:45,840
Speaker 1: there's a question, how would we see this exponential complexity,

898
00:47:45,880 --> 00:47:49,680
Speaker 1: where is it hiding? How did Hawking miss it? In

899
00:47:49,800 --> 00:47:52,400
Speaker 1: all honesty, that's very much an open area of research

900
00:47:52,520 --> 00:47:54,600
Speaker 1: right now, we just don't know. All right, Well, thanks

901
00:47:54,719 --> 00:47:57,080
Speaker 1: very much for sharing your thinking about this really fun

902
00:47:57,200 --> 00:48:01,080
Speaker 1: and fascinating puzzle about these corner of the universe. Really

903
00:48:01,120 --> 00:48:04,640
Speaker 1: appreciate your time. So that was my fun conversation with

904
00:48:04,800 --> 00:48:07,440
Speaker 1: Nada Englehart, who tried to help us get a mental

905
00:48:07,560 --> 00:48:10,480
Speaker 1: picture of what's going on. And it's sort of amazing

906
00:48:10,480 --> 00:48:14,200
Speaker 1: because it means basically quantum mechanics was right. It means that, yeah,

907
00:48:14,520 --> 00:48:17,640
Speaker 1: information is not destroyed. It's there. It will not disappear

908
00:48:17,680 --> 00:48:19,839
Speaker 1: from the universe, even if it has to like hide

909
00:48:19,920 --> 00:48:22,160
Speaker 1: in some little weird quantum island at the core of

910
00:48:22,200 --> 00:48:25,239
Speaker 1: a black hole. It will persist, right, I guess the

911
00:48:25,320 --> 00:48:27,719
Speaker 1: question is could you decode that information? Like if you,

912
00:48:28,400 --> 00:48:30,320
Speaker 1: you know, trillions of years from now in the future,

913
00:48:30,480 --> 00:48:33,320
Speaker 1: someone looking at our black holes evaporating, could they like,

914
00:48:33,680 --> 00:48:36,520
Speaker 1: you know, make up, Oh there's more banana there. That's

915
00:48:36,560 --> 00:48:39,600
Speaker 1: the question, you know, can you decode this information that

916
00:48:39,719 --> 00:48:42,520
Speaker 1: was the subject of this fun TV show called Dev's

917
00:48:42,920 --> 00:48:45,120
Speaker 1: you know that basically built on this whole concept that

918
00:48:45,200 --> 00:48:47,960
Speaker 1: couldn't you take a scan of the Earth now and

919
00:48:48,160 --> 00:48:51,640
Speaker 1: use that to reconstruct history? Could you know, see Jesus

920
00:48:51,719 --> 00:48:54,640
Speaker 1: on the cross or important historical events just based on

921
00:48:54,760 --> 00:48:58,200
Speaker 1: you know where air molecules are today, and in principle

922
00:48:58,440 --> 00:49:01,200
Speaker 1: if possible, but in practice it would require knowing the

923
00:49:01,320 --> 00:49:03,960
Speaker 1: quantum state of all of these particles so you could

924
00:49:03,960 --> 00:49:05,880
Speaker 1: properly get them back in time, and that would be

925
00:49:06,320 --> 00:49:10,040
Speaker 1: essentially impossible even with a quantum computer, but in principle

926
00:49:10,239 --> 00:49:13,480
Speaker 1: it is possible. And so if this information does leak

927
00:49:13,520 --> 00:49:16,040
Speaker 1: out of black holes in terms of Hawking radiation, then

928
00:49:16,080 --> 00:49:19,440
Speaker 1: in principle you could decoded. And the physicist actually did

929
00:49:19,520 --> 00:49:21,880
Speaker 1: a really fun sort of thought experiment to how you

930
00:49:21,960 --> 00:49:26,839
Speaker 1: could make that work That involves like weird informational wormholes. Oh,

931
00:49:26,960 --> 00:49:30,759
Speaker 1: great sprinkle and more wormholes? Why not? The way they

932
00:49:30,840 --> 00:49:32,640
Speaker 1: think you might be able to do it is to

933
00:49:32,920 --> 00:49:37,440
Speaker 1: run a simulation of a black hole on a quantum computer.

934
00:49:37,600 --> 00:49:40,000
Speaker 1: To take a quantum computer which can represent these quantum

935
00:49:40,040 --> 00:49:43,120
Speaker 1: states fairly naturally, and run a simulation of the black

936
00:49:43,160 --> 00:49:45,759
Speaker 1: hole and compare the Hawking radiation you get from the

937
00:49:45,840 --> 00:49:48,799
Speaker 1: real black hole to the simulated ones. So then if

938
00:49:48,800 --> 00:49:50,920
Speaker 1: you find a simulated black hole that has the same

939
00:49:50,960 --> 00:49:53,680
Speaker 1: pattern of radiation as you're a real one, then you

940
00:49:53,760 --> 00:49:55,960
Speaker 1: can peer inside of it and see this must have

941
00:49:56,000 --> 00:50:00,239
Speaker 1: been what was inside the black hole. What, but would

942
00:50:00,239 --> 00:50:03,760
Speaker 1: have to match like every particle that comes out of it, Yeah, exactly,

943
00:50:03,840 --> 00:50:06,200
Speaker 1: It would be tricky. But if you do that, then

944
00:50:06,280 --> 00:50:10,160
Speaker 1: something really weird happens. In their calculations, they suggest that

945
00:50:10,280 --> 00:50:14,200
Speaker 1: a wormhole is essentially created between the real black hole

946
00:50:14,520 --> 00:50:18,840
Speaker 1: and the simulated black hole in your quantum computer. What

947
00:50:19,920 --> 00:50:24,279
Speaker 1: it's like an informational black hole, like a virtual black hole. Yeah,

948
00:50:24,440 --> 00:50:27,480
Speaker 1: because then that information is now being revealed from the

949
00:50:27,560 --> 00:50:30,080
Speaker 1: core of the black hole, a real black hole, to

950
00:50:30,760 --> 00:50:33,840
Speaker 1: the one in your simulation in your quantum computer. And

951
00:50:33,920 --> 00:50:36,319
Speaker 1: so there's like, how does that information get from there

952
00:50:36,360 --> 00:50:39,120
Speaker 1: to there? It's this weird non local effect, and so

953
00:50:39,680 --> 00:50:43,239
Speaker 1: non local information transfer can really only be done by wormholes,

954
00:50:43,280 --> 00:50:46,160
Speaker 1: which connect different places in space and time. So like,

955
00:50:46,440 --> 00:50:48,880
Speaker 1: that's pretty weird. If you run a program which creates

956
00:50:48,920 --> 00:50:52,120
Speaker 1: a wormhole between your computer and a real black hole,

957
00:50:52,680 --> 00:50:56,920
Speaker 1: whoa creates like a little bookatiny channel or something between

958
00:50:56,960 --> 00:51:01,120
Speaker 1: the two. All right, well, I guess the big question

959
00:51:01,200 --> 00:51:02,719
Speaker 1: is what does this mean? Does this mean that we've

960
00:51:02,880 --> 00:51:06,040
Speaker 1: solved or we think we may have solved this kind

961
00:51:06,080 --> 00:51:10,320
Speaker 1: of like conflict between quantum mechanics and general relativity or

962
00:51:10,719 --> 00:51:13,600
Speaker 1: does this sort of side step that conflict. It sort

963
00:51:13,640 --> 00:51:16,760
Speaker 1: of sidesteps the conflict, right, it doesn't really get to solution.

964
00:51:16,880 --> 00:51:19,680
Speaker 1: The solution would be a full theory of quantum gravity,

965
00:51:19,760 --> 00:51:23,200
Speaker 1: one that tells us what happens really small distances and

966
00:51:23,400 --> 00:51:26,200
Speaker 1: powerful gravity, which is not something that's easy to test,

967
00:51:26,360 --> 00:51:29,239
Speaker 1: right because small distances you only have little particles, and

968
00:51:29,320 --> 00:51:32,600
Speaker 1: little particles have very small amounts of mass and gravity

969
00:51:32,680 --> 00:51:36,000
Speaker 1: super duper weak, so we can't really do gravity experiments

970
00:51:36,040 --> 00:51:38,360
Speaker 1: with tiny particles, so it's pretty rare we get to

971
00:51:38,440 --> 00:51:41,640
Speaker 1: even explore this regime experimentally to like see what happens,

972
00:51:41,680 --> 00:51:44,640
Speaker 1: which is why black holes in their interiors are such

973
00:51:44,640 --> 00:51:47,279
Speaker 1: a valuable test. Ben So we think we need like

974
00:51:47,360 --> 00:51:50,120
Speaker 1: a theory of quantum gravity to really resolve this. And

975
00:51:50,160 --> 00:51:52,920
Speaker 1: the fascinating thing about making progress like this on a

976
00:51:53,320 --> 00:51:57,319
Speaker 1: big question is that it's a bit disappointing and exhilarating.

977
00:51:57,600 --> 00:52:01,040
Speaker 1: Like it's disappointing because people fought you need a quantum

978
00:52:01,080 --> 00:52:04,920
Speaker 1: gravity to answer this question, So now answering it without

979
00:52:05,000 --> 00:52:06,920
Speaker 1: the getting the theory quantum gravity is sort of like,

980
00:52:07,120 --> 00:52:10,480
Speaker 1: oh darn, you know, we thought maybe this was like

981
00:52:10,600 --> 00:52:13,520
Speaker 1: a thread we could pull on to reveal the truth

982
00:52:13,640 --> 00:52:16,200
Speaker 1: theory of quantum gravity. Instead, we only sort of like,

983
00:52:16,480 --> 00:52:18,080
Speaker 1: you know, pull the thread and got the end of

984
00:52:18,120 --> 00:52:20,359
Speaker 1: the thread. We didn't really like get the whole thing

985
00:52:20,440 --> 00:52:24,000
Speaker 1: to unravel. Basically, physicists are never happy. You find a solution,

986
00:52:24,040 --> 00:52:27,280
Speaker 1: you're happy and unhappy, And you don't find a solution,

987
00:52:27,360 --> 00:52:30,360
Speaker 1: you're happy and unhappy. We're in a superposition of happy

988
00:52:30,480 --> 00:52:35,400
Speaker 1: and unhappy at all entangled happiness there. And also remember

989
00:52:35,560 --> 00:52:39,000
Speaker 1: that not everybody really believes in this solution. There are

990
00:52:39,040 --> 00:52:41,120
Speaker 1: folks out there that are just like, no, there's too

991
00:52:41,200 --> 00:52:44,879
Speaker 1: many mathematical tricks there. I don't really buy it. It's

992
00:52:44,880 --> 00:52:47,759
Speaker 1: sort of a little bit controversial still, and you know,

993
00:52:47,840 --> 00:52:51,360
Speaker 1: there's reasons to be skeptical. Like to do this calculation,

994
00:52:51,480 --> 00:52:54,200
Speaker 1: they did this weird trick where they said, I don't

995
00:52:54,200 --> 00:52:57,040
Speaker 1: know how to do a calculation in four dimensional space

996
00:52:57,120 --> 00:53:00,320
Speaker 1: with gravity, but I can do a similar calculation on

997
00:53:00,480 --> 00:53:04,000
Speaker 1: a three dimensional space that has no gravity. And there's

998
00:53:04,080 --> 00:53:07,279
Speaker 1: this famous result in physics from about twenty five years

999
00:53:07,280 --> 00:53:10,160
Speaker 1: ago showing that those two calculations should be the same.

1000
00:53:10,360 --> 00:53:12,680
Speaker 1: You take a four dimensional space that has gravity in it,

1001
00:53:13,080 --> 00:53:15,080
Speaker 1: and you should be able to instead get all the

1002
00:53:15,120 --> 00:53:17,239
Speaker 1: information about that space just by looking at like a

1003
00:53:17,360 --> 00:53:20,279
Speaker 1: three D surface around that four D space, And in

1004
00:53:20,360 --> 00:53:22,600
Speaker 1: the three D surface there is no gravity, there's just

1005
00:53:22,800 --> 00:53:26,080
Speaker 1: quantum mechanics. So they did their calculation on this like

1006
00:53:26,320 --> 00:53:29,719
Speaker 1: three D surface, not in the actual gravity of a

1007
00:53:29,800 --> 00:53:33,280
Speaker 1: black hole. And so some people feel like maybe that's cheating.

1008
00:53:33,480 --> 00:53:36,239
Speaker 1: Other people feel like, know that connection is real. It's

1009
00:53:36,280 --> 00:53:38,960
Speaker 1: a mathematical trick, but it's real and it's reflective of

1010
00:53:39,000 --> 00:53:41,000
Speaker 1: the way our universe works. So there's still sort of

1011
00:53:41,000 --> 00:53:43,640
Speaker 1: a lot of controversy about whether this will hold up.

1012
00:53:44,560 --> 00:53:46,880
Speaker 1: Just throw all those physics into the black hole and

1013
00:53:46,960 --> 00:53:49,440
Speaker 1: then them doke it out. Yeah, and you know, we

1014
00:53:49,520 --> 00:53:52,319
Speaker 1: have the East Coast versus the West coast. There's two

1015
00:53:52,520 --> 00:53:56,440
Speaker 1: different calculations, two different strategies for doing this calculation that

1016
00:53:56,560 --> 00:53:59,840
Speaker 1: got dissimilar results, and so that's sort of reassuring, but

1017
00:54:00,000 --> 00:54:01,719
Speaker 1: it's also sort of fun because you get like East

1018
00:54:01,800 --> 00:54:06,960
Speaker 1: Coast versus West Coast. Who wraps better? They're all wrapped

1019
00:54:06,960 --> 00:54:09,560
Speaker 1: it up inside a black hole. All right, Well, it

1020
00:54:09,640 --> 00:54:12,160
Speaker 1: sounds like maybe stay tuned. It seems like there's some

1021
00:54:12,400 --> 00:54:15,960
Speaker 1: interesting progress that's been made, but not everyone is convinced

1022
00:54:16,000 --> 00:54:19,000
Speaker 1: about this new approach. That's right, and my personal hope

1023
00:54:19,320 --> 00:54:21,799
Speaker 1: is that we do eventually get to do experiments near

1024
00:54:21,880 --> 00:54:24,800
Speaker 1: black hole. All this, the theoretical calculation is fun and

1025
00:54:24,920 --> 00:54:27,160
Speaker 1: it tells us what question is to ask, but we

1026
00:54:27,239 --> 00:54:29,200
Speaker 1: never really know the answer until we actually get to

1027
00:54:29,239 --> 00:54:32,000
Speaker 1: go do experiments near a black hole or maybe even

1028
00:54:32,360 --> 00:54:34,600
Speaker 1: in a black hole. Until then, we just have to

1029
00:54:35,000 --> 00:54:39,080
Speaker 1: smell the banana in the air and remember it and

1030
00:54:39,280 --> 00:54:44,799
Speaker 1: remember and remember both our dearly departed lunch. All right, well,

1031
00:54:44,880 --> 00:54:48,239
Speaker 1: we hope you enjoyed that. Thanks for joining us, see

1032
00:54:48,280 --> 00:54:58,800
Speaker 1: you next time. Thanks for listening, and remember that Daniel

1033
00:54:58,840 --> 00:55:01,160
Speaker 1: and Jorge explained. The unit Verse is a production of

1034
00:55:01,280 --> 00:55:04,640
Speaker 1: I Heart Radio or more podcast from my heart Radio.

1035
00:55:04,800 --> 00:55:08,320
Speaker 1: Visit the I Heart Radio Apple Apple Podcasts, or wherever

1036
00:55:08,480 --> 00:55:12,080
Speaker 1: you listen to your favorite shows. H