Latest / Daniel and Kelly’s Extraordinary Universe / Have we solved the black hole information paradox?

Transcript

Have we solved the black hole information paradox? · Daniel and Kelly’s Extraordinary Universe

• 0:08
  Speaker 1: Hey, Daniel, what's the best place in the universe to
• 0:11
  Speaker 1: hide something? Like? What do you want to hide? You know,
• 0:15
  Speaker 1: treasure or secrets anything. I guess you could tape it
• 0:18
  Speaker 1: to a rock and hide it in the asteroid belt
• 0:21
  Speaker 1: among millions of other rocks. Yeah that's pretty good. But
• 0:25
  Speaker 1: you know, technically somebody could still find it. Yeah, that's true.
• 0:28
  Speaker 1: I guess you could drop it in the sun. I
• 0:31
  Speaker 1: said hide it, not destroy it completely. All right, this
• 0:35
  Speaker 1: is pretty tricky. What if you put it into a
• 0:37
  Speaker 1: black hole? It depends can you wait like two zillion
• 0:41
  Speaker 1: years to get it back out again? But you mean
• 0:43
  Speaker 1: you can get things out of a black hole? Well,
• 0:45
  Speaker 1: you know, technically depends on the definition of out. But
• 0:48
  Speaker 1: if you want to throw a dictionary into the black hole,
• 0:52
  Speaker 1: everything comes back out except for the page that says out. Ye.
• 1:10
  Speaker 1: Hi am Jorge Immad, cartoonists and the creator of PhD Comics. Hi.
• 1:14
  Speaker 1: I'm Daniel. I'm a particle physicist, and sometimes I feel
• 1:17
  Speaker 1: like my mind has been thrown into a black hole.
• 1:20
  Speaker 1: Oh yeah, is it that nothing comes out of it?
• 1:22
  Speaker 1: That would be the case if my mind was a
• 1:24
  Speaker 1: black hole. But sometimes I feel like everything I've learned
• 1:26
  Speaker 1: has been slurped up and dropped into a black hole
• 1:29
  Speaker 1: because I can't remember any of it. It gets spaghettified.
• 1:31
  Speaker 1: And what if he eat spaghetti? What happens to spaghetti
• 1:34
  Speaker 1: when it gets spaghettified? It becomes spaghetti squared, becomes a
• 1:38
  Speaker 1: string theory maybe, but welcome to our podcast Daniel and
• 1:42
  Speaker 1: Jorge Explain the Universe, a production of I Heart Radio,
• 1:45
  Speaker 1: in which we tear our minds into little pieces of
• 1:48
  Speaker 1: spaghetti and then stretch those out into tiny little strings
• 1:51
  Speaker 1: in a vain and futile attempt to understand everything in
• 1:56
  Speaker 1: the universe. We take it all apart, we tear it
• 1:58
  Speaker 1: in a little bits, and we try to put it
• 2:00
  Speaker 1: back together in a way that we hope you can understand.
• 2:03
  Speaker 1: That's right, because it is a long and tasty universe
• 2:07
  Speaker 1: out there, with lots of mysteries and unknowns and exciting
• 2:11
  Speaker 1: things discover, and lots of different sauce options. You know. Actually,
• 2:15
  Speaker 1: I just realized they're spaghettini, right, and angel hairy pasta.
• 2:19
  Speaker 1: Although I don't know the difference. There must be a
• 2:21
  Speaker 1: whole spectrum, right, It's not like pasta is quantized. There
• 2:24
  Speaker 1: must be an infinite number of kinds of pasta. Well, eventually,
• 2:27
  Speaker 1: pasta is quantized. Everything is quantized eventually, right if you
• 2:30
  Speaker 1: get down to a single chain of pasta atoms, right,
• 2:33
  Speaker 1: nano pasta. Yeah, that's a whole new field of fabrication quarkinis.
• 2:39
  Speaker 1: But yeah, the universe is full of interesting and amazing things,
• 2:43
  Speaker 1: and none more so mysterious than black holes. That's right.
• 2:46
  Speaker 1: Black holes are these weird corners of the universe where
• 2:49
  Speaker 1: we think secrets lie. We suspect the solution to the
• 2:53
  Speaker 1: age old conflict between general relativity and quantum mechanics might
• 2:57
  Speaker 1: lie right at the heart of black holes. Of course,
• 3:00
  Speaker 1: nobody can see inside them, so it's incredibly frustrating to
• 3:04
  Speaker 1: think that the answers to some of our deepest questions
• 3:07
  Speaker 1: exist but are hidden from us. Does that drive physicist
• 3:10
  Speaker 1: bonkers to know that you know there are answers out there,
• 3:12
  Speaker 1: but maybe they're trapped in a place where they can
• 3:15
  Speaker 1: never get out. That's essentially the project of physics, right,
• 3:18
  Speaker 1: The answers are out there. The universe does contain these answers,
• 3:22
  Speaker 1: and if you can come up with the right experiment,
• 3:24
  Speaker 1: you can force the universe to reveal those truths. That's
• 3:27
  Speaker 1: basically how we accumulated all the knowledge that we do have.
• 3:31
  Speaker 1: But yeah, it's frustrating to think that there might be
• 3:33
  Speaker 1: places in the universe that nobody could ever look, where
• 3:36
  Speaker 1: information could hide forever, escaping from even our most clever
• 3:40
  Speaker 1: efforts to reveal them. You may get sound like physicists
• 3:43
  Speaker 1: are like paparazzis of the universe, Like you're trying to
• 3:46
  Speaker 1: catch the universe, you know, sunbathing in its supports or something.
• 3:51
  Speaker 1: I used to think of us as more like murder
• 3:53
  Speaker 1: mystery detectives, But yeah, paparazzi is a more positive way,
• 3:56
  Speaker 1: because the universe is beautiful. It deserves our attention. Positive. Yeah, yeah,
• 4:01
  Speaker 1: I guess they're surprised to being d universe. We're just
• 4:03
  Speaker 1: here trying to enjoy the beauty of the universe, you know,
• 4:06
  Speaker 1: and get its signature once in a while so we
• 4:08
  Speaker 1: can sell it on eBay and so to the National
• 4:10
  Speaker 1: Enquirer or Science magazine, you know, one of those two
• 4:14
  Speaker 1: whoever will take it. Is this part of the free
• 4:16
  Speaker 1: Brittany movement. I don't think there's a free universe movement
• 4:18
  Speaker 1: where they're like, hey, physicists, leave the universe alone. Keep
• 4:22
  Speaker 1: some of the mystery. You know, maybe doesn't want to
• 4:25
  Speaker 1: reveal its mysteries. You're being pushy. The mysteries are wonderful,
• 4:29
  Speaker 1: but the incredible part of this journey of physics is
• 4:32
  Speaker 1: that the truth is always more amazing and bonkers and
• 4:35
  Speaker 1: beautiful than we even possibly imagined, and so it's always
• 4:39
  Speaker 1: worth trying to dig into it and figure out what
• 4:41
  Speaker 1: the truth is. And so recently we've taken pictures of
• 4:44
  Speaker 1: black holes. You sort of know where they are, you
• 4:46
  Speaker 1: can see them gravitationally, and now we know what they
• 4:49
  Speaker 1: actually look like. But they still remain a pretty big mystery,
• 4:53
  Speaker 1: maybe even the biggest mystery we have in the universe, right,
• 4:56
  Speaker 1: that's right, And new mysteries keep popping up. You know.
• 4:58
  Speaker 1: Originally people were like, wow, our black holes real, and
• 5:01
  Speaker 1: then we discovered that they are actually out there and
• 5:03
  Speaker 1: that was kind of mind blowing. But then more questions
• 5:06
  Speaker 1: arose about them, and more questions and more questions, and
• 5:08
  Speaker 1: they're just like an endless playground for theorists to think
• 5:12
  Speaker 1: about what the universe means and and how it behaves
• 5:15
  Speaker 1: in really strange circumstances, and so they're continual source of
• 5:18
  Speaker 1: mystery and also opportunities to learn things about the universe,
• 5:22
  Speaker 1: because that's what mysteries are. They are ways for us
• 5:24
  Speaker 1: to unravel a thread and figure something out, right, because
• 5:28
  Speaker 1: I guess anything that happens in the universe tells us
• 5:30
  Speaker 1: a little bit about how the universe works, especially the
• 5:34
  Speaker 1: really extreme situations like black holes. Yeah, because we think
• 5:37
  Speaker 1: that the universe follows rules right there. There are physical
• 5:40
  Speaker 1: laws and everything in the universe always has to obey them.
• 5:44
  Speaker 1: Why that is is like a deep and fun question
• 5:47
  Speaker 1: in the philosophy of science, So check out some other
• 5:49
  Speaker 1: philosophy podcast for that. But the goal of physics is
• 5:52
  Speaker 1: to take advantage of that fact and say, let's find
• 5:54
  Speaker 1: opportunities where the things that happened reveal what the rules
• 5:57
  Speaker 1: must have been. You make It's not like we should
• 6:00
  Speaker 1: named the podcast Daniel to Daniel and Jorge Exposed the Universe.
• 6:04
  Speaker 1: That sounds a bit too risk, ay, And we're trying
• 6:07
  Speaker 1: to be family friendly here. So black holes are mysterious,
• 6:10
  Speaker 1: and there's sort of super extra mysterious. I feel like,
• 6:13
  Speaker 1: you know, I feel like there's not just kind of
• 6:15
  Speaker 1: the questions of what happens inside or what happens as
• 6:18
  Speaker 1: you go in, or how they can possibly exist in
• 6:21
  Speaker 1: the universe. But there's also sort of some very interesting
• 6:25
  Speaker 1: theoretical questions. Yeah, it's sort of weird that black holes
• 6:28
  Speaker 1: even exist. You know. One theory of physics say that
• 6:31
  Speaker 1: they can't exist, but they have to have certain properties,
• 6:34
  Speaker 1: and another theory of physics is that those properties are impossible.
• 6:37
  Speaker 1: So there's like a conflict at the heart of physics
• 6:40
  Speaker 1: between our idea of space and time, which is governed
• 6:44
  Speaker 1: by general relativity, and our idea of how the universe
• 6:46
  Speaker 1: works at the smallest scale, which is governed by quantum mechanics,
• 6:50
  Speaker 1: And those two disagree about what's going on inside a
• 6:52
  Speaker 1: black hole, whether black holes can live forever, and all
• 6:55
  Speaker 1: sorts of stuff, and so there are really fun mysteries there.
• 6:59
  Speaker 1: And so there's one mystery in particular that people have
• 7:01
  Speaker 1: been wondering about four decades about the stuff that goes
• 7:05
  Speaker 1: into the black hole. Yeah, and it seems like very
• 7:07
  Speaker 1: recently scientists have made some pretty um possibly interesting progress
• 7:13
  Speaker 1: towards solving one of these big mysteries. So have they been, um,
• 7:17
  Speaker 1: you know, parked outside their favorite coffee shop, you know,
• 7:19
  Speaker 1: just waiting to take those pictures the physics paparatti Exactly
• 7:24
  Speaker 1: when will that black hole finishes spa appointment. So to
• 7:27
  Speaker 1: the end the program, we'll be asking the question, have
• 7:35
  Speaker 1: we solved the black hole information paradox? I love that phrase,
• 7:40
  Speaker 1: black hole information paradox. It's got some poetry to it. Yeah,
• 7:44
  Speaker 1: it's a little too long for me. I kind of
• 7:46
  Speaker 1: struggled to get that one out. Black hole information paradox?
• 7:51
  Speaker 1: Have we solved it? That's the question? That's the question,
• 7:54
  Speaker 1: all right. So there's a paradox about black holes. It
• 7:56
  Speaker 1: involves information, and we think that maybe in their last
• 8:00
  Speaker 1: few months, maybe I physicists have solved this paradox. That's right.
• 8:03
  Speaker 1: It's a puzzle that's been outstanding for decades and to
• 8:07
  Speaker 1: one of those questions that people always thought, wow, if
• 8:10
  Speaker 1: you figure that out, then you're gonna learn something deep
• 8:12
  Speaker 1: about the universe. Or they imagine that maybe in a
• 8:15
  Speaker 1: hundred years somebody will know the answer to that. So
• 8:18
  Speaker 1: have some progress made on it to have people feel
• 8:20
  Speaker 1: like maybe they've even found the solution. It's a big deal, right,
• 8:24
  Speaker 1: And apparently recently something has happened, so people have appolished
• 8:28
  Speaker 1: the paper or they what happened? You know, there's been
• 8:31
  Speaker 1: a whole series of papers in this past year where
• 8:33
  Speaker 1: people have found a whole new way to attack this
• 8:35
  Speaker 1: problem and made what they thought was pretty exciting progress,
• 8:39
  Speaker 1: and some people even think that they may have solved it.
• 8:41
  Speaker 1: Oh interesting. They found a new method of attack, yes, exactly,
• 8:46
  Speaker 1: a new theoretical way to attack black holes, without of course,
• 8:50
  Speaker 1: actually going over there and measuring anything. All right, Well,
• 8:53
  Speaker 1: as usual, we were wondering how many people out there
• 8:55
  Speaker 1: had heard about the black hole information paradox, or that
• 8:58
  Speaker 1: they might have found a solution in for it. So
• 9:01
  Speaker 1: Daniel went out there into the wilds of the internet
• 9:03
  Speaker 1: to ask folks, what is the solution to the black
• 9:06
  Speaker 1: hole information paradox? That's right, So thanks to everybody who
• 9:10
  Speaker 1: volunteered their minds and their time. If you would like
• 9:12
  Speaker 1: to participate for a future episode, please do not be shy.
• 9:16
  Speaker 1: Right to me two questions at Daniel and Jorge dot com.
• 9:19
  Speaker 1: It's fun. Here's what people had to say. I don't
• 9:22
  Speaker 1: even know of a paradox information wise in black holes,
• 9:26
  Speaker 1: so um, I don't have the solution. I'm very sorry.
• 9:31
  Speaker 1: I believe it is that all the information is imprinted
• 9:35
  Speaker 1: on the surface like a that's what they call it,
• 9:39
  Speaker 1: a hologram. And some series actually said that how your
• 9:42
  Speaker 1: whole universe could be something like that. The paradox is
• 9:45
  Speaker 1: about what happens to information that gets sucked into a
• 9:48
  Speaker 1: black hole. I think what happens is that it gets
• 9:52
  Speaker 1: stored at the event horizon of the black hole, more
• 9:55
  Speaker 1: like black hole disinformation coles are trying to trick us. Well,
• 10:02
  Speaker 1: I guess this one refers to the fact that information
• 10:05
  Speaker 1: can get sucked into the into a black hole and
• 10:09
  Speaker 1: then you cannot get access to it anymore. Um but
• 10:13
  Speaker 1: ultimate information is just hidden in the black hole and
• 10:16
  Speaker 1: they destroyed it. So maybe the solution is that there's
• 10:21
  Speaker 1: no paradox after all. I don't think I know the
• 10:23
  Speaker 1: answer to the black hole information paradox, but I do
• 10:26
  Speaker 1: know that information can't be destroyed, so it's got to
• 10:30
  Speaker 1: be in the black hole somewhere. How that information gets extracted,
• 10:33
  Speaker 1: I'm not exactly sure. It sounds lucky. It's something to
• 10:36
  Speaker 1: do with Obviously, nothing can ever leave a black hole. Um,
• 10:41
  Speaker 1: but Hawking radiation says that, um, if left a lot
• 10:45
  Speaker 1: of nothing else goes into it, eventually they could evaporate
• 10:48
  Speaker 1: into nothing. Um that sounds pretty paradoxical to be so.
• 10:52
  Speaker 1: I had seen that a solution had been found recently
• 10:56
  Speaker 1: or in the past year or so, But apparently it's
• 10:59
  Speaker 1: something and going in leaves an imprint on the event horizon,
• 11:04
  Speaker 1: which somehow is represented in the radiation in the Hawking radiation.
• 11:10
  Speaker 1: But that kind of seems wrong because of the uh
• 11:14
  Speaker 1: no hair theorem. I mean, I think that's the gist
• 11:18
  Speaker 1: of it. I have heard of the black hole information paradox,
• 11:23
  Speaker 1: but I'm not sure exactly what it is. I believe
• 11:26
  Speaker 1: it is related to Hawkings radiation. Well, I suppose I
• 11:30
  Speaker 1: would ask why does it need to be conserved in
• 11:33
  Speaker 1: the first place? So why would it information disappearing be
• 11:38
  Speaker 1: such a problem. Perhaps it's not a problem at all,
• 11:41
  Speaker 1: especially if information seems to be created as new space
• 11:46
  Speaker 1: is created. Maybe it's not a problem that information goes
• 11:50
  Speaker 1: away when it enters a black hole. All right. Not
• 11:52
  Speaker 1: a lot of people had heard of this, you know,
• 11:54
  Speaker 1: a lot of good speculation, but yeah, no concrete answers there,
• 11:58
  Speaker 1: and some people seem to know what it is though.
• 12:01
  Speaker 1: That's pretty impressive. Yeah, well, we covered it on an
• 12:03
  Speaker 1: episode dug deep into the nature of this paradox about
• 12:06
  Speaker 1: information and black holes. Though I guess our listeners have
• 12:09
  Speaker 1: done their homework Apparently our episode didn't fall into a
• 12:12
  Speaker 1: black hole. It actually made it to people's spaghetti places.
• 12:16
  Speaker 1: It fell into people's ear holes. Yeah, all right, Daniel
• 12:19
  Speaker 1: will step us through this. Then let's start with what
• 12:21
  Speaker 1: it is first. What is the black hole information paradox.
• 12:25
  Speaker 1: This is a really fun concept because it brings together
• 12:28
  Speaker 1: these two different theories, general relativity, which tells us something
• 12:31
  Speaker 1: about black holes, and quantum mechanics, which tells us something
• 12:34
  Speaker 1: about information. So we start with general relativity because that's
• 12:38
  Speaker 1: where black holes come from. General relativity tells us, you know,
• 12:42
  Speaker 1: how space is curved in the presence of mass and
• 12:44
  Speaker 1: stuff like that, and it's sort of the genesis of
• 12:46
  Speaker 1: black holes, right there are this place in space where
• 12:49
  Speaker 1: no information can escape. Anything that falls past the event
• 12:53
  Speaker 1: horizon should be inside the event horizon forever until the
• 12:57
  Speaker 1: end of the universe. And you can't know anything out
• 13:00
  Speaker 1: what's inside the black hole other than the total mass
• 13:04
  Speaker 1: of the black hole, whether it's spinning, and whether it
• 13:07
  Speaker 1: has electric charge. Everything else is hidden from you. So
• 13:10
  Speaker 1: anything that's going on inside the black hole, you can't
• 13:13
  Speaker 1: know anything about it because that would be allowing you
• 13:15
  Speaker 1: to get information out of the black hole. This is
• 13:18
  Speaker 1: called the no hair theorem, tells you that's a very
• 13:22
  Speaker 1: limited amount of information you can have about a black hole.
• 13:25
  Speaker 1: So that means that if your friend threw a banana
• 13:27
  Speaker 1: into the black hole, you couldn't tell that it was
• 13:30
  Speaker 1: banana instead of an apple. You can only measure the
• 13:32
  Speaker 1: mass that they threw into the black hole. Right, That's
• 13:35
  Speaker 1: an interesting concept because I guess, you know, maybe we're
• 13:38
  Speaker 1: all used to the idea that black holes can sort
• 13:41
  Speaker 1: of things, and things can't get out, not even light,
• 13:44
  Speaker 1: But that also I guess applies to information itself. You know,
• 13:47
  Speaker 1: if light can't get out, then really nothing can get out,
• 13:50
  Speaker 1: not even like ones and zeros or you know, just anything. Right.
• 13:54
  Speaker 1: That's right, because we live in a physical universe and
• 13:56
  Speaker 1: information has to be represented physically. So to get information
• 14:00
  Speaker 1: from one place to another, you have to send a message,
• 14:02
  Speaker 1: which means like a particle or a wave of some
• 14:04
  Speaker 1: kind of physical thing. So if no physical thing can
• 14:07
  Speaker 1: cross that boundary, then no information can get out technically,
• 14:11
  Speaker 1: then you can gravitational waves escape a black hole. Gravitational
• 14:14
  Speaker 1: waves cannot escape a black hole, but a black hole
• 14:17
  Speaker 1: itself can create gravitational waves. But when it creates it
• 14:20
  Speaker 1: isn't it sort of like sending a signal out. Now,
• 14:22
  Speaker 1: that's just the information about the black hole itself. Like
• 14:25
  Speaker 1: you can know the mass the black hole from the outside,
• 14:28
  Speaker 1: and a gravitational wave is just a change in like
• 14:31
  Speaker 1: the location of a mass. And so you can know
• 14:34
  Speaker 1: about where a black hole is and what mass it
• 14:36
  Speaker 1: has and how it's moving, and that motion can generate
• 14:38
  Speaker 1: gravitational waves without knowing anything about what's going on inside
• 14:42
  Speaker 1: the black hole. All right, So that's a general relativity.
• 14:44
  Speaker 1: And then how does quantum mechanics figure into it. Well,
• 14:47
  Speaker 1: quantum mechanics says something really important and powerful about information.
• 14:51
  Speaker 1: It says that you can always reconstruct the past of
• 14:54
  Speaker 1: our universe based on what's going on right now. It's
• 14:58
  Speaker 1: sort of like a post addiction. It says, if you
• 15:00
  Speaker 1: could scan the universe finally enough, you could figure out
• 15:03
  Speaker 1: what has happened. It's sort of like saying, if I
• 15:06
  Speaker 1: burn a book, then you should be able to from
• 15:09
  Speaker 1: the ashes and the smoke and everything that comes out
• 15:11
  Speaker 1: of it later tell me exactly what that book was.
• 15:14
  Speaker 1: That all the information from that book is still somehow
• 15:17
  Speaker 1: imprinted in the universe, even if sort of scattered now
• 15:20
  Speaker 1: and harder to reconstruct, right does it kind of related
• 15:23
  Speaker 1: to that idea that we've talked about before, which is
• 15:25
  Speaker 1: the idea of cost and effect. Like if a particle
• 15:28
  Speaker 1: does this and it affects another particle, and that particle
• 15:31
  Speaker 1: affects another particle, you can always backtrack kind of what happened.
• 15:34
  Speaker 1: That information is not lost, like what one particle does
• 15:37
  Speaker 1: to another particle they remember, right, yeah, exactly. That information
• 15:41
  Speaker 1: is not lost. And our present state of the universe
• 15:43
  Speaker 1: is unique, right, it maps back to a single past.
• 15:46
  Speaker 1: You can't have two different pasts that produce the same
• 15:49
  Speaker 1: present because then you wouldn't be able to tell which
• 15:52
  Speaker 1: was which. And so you have all the information you
• 15:54
  Speaker 1: need in the present to reconstruct the past. And this
• 15:57
  Speaker 1: is a really deep and powerful important thing and quantum
• 16:00
  Speaker 1: mechanics like that's at the basis of quantum mechanics. It's
• 16:03
  Speaker 1: called unitarity. And if we didn't have it, if it
• 16:06
  Speaker 1: wasn't true, then we would have to question like quantum
• 16:09
  Speaker 1: mechanics itself and come up with another theory. So it's
• 16:11
  Speaker 1: like something every physicist out there believes is true about
• 16:15
  Speaker 1: the universe. The information is not lost because when you
• 16:18
  Speaker 1: think clancal mechanics is pretty real. We think it's pretty real.
• 16:21
  Speaker 1: We've tested it pretty well. We tested all day every
• 16:24
  Speaker 1: day at the Large Hadron Collider and in lots of
• 16:26
  Speaker 1: other different ways, so we're pretty sure it's true. Although,
• 16:30
  Speaker 1: you know, black holes are an extreme situation, so maybe
• 16:33
  Speaker 1: something gets broken. You never know. That's kind of where
• 16:36
  Speaker 1: the paradox part comes in, right, there's a paradox about
• 16:40
  Speaker 1: what happens between these two concepts of the universe inside
• 16:43
  Speaker 1: of a black hole exactly, because you might ask, well,
• 16:46
  Speaker 1: what happens to the information about my banana if I
• 16:49
  Speaker 1: throw my banana into the black hole and now it's
• 16:52
  Speaker 1: inside the black hole and I can't learn anything about it,
• 16:54
  Speaker 1: where is that information? Well, general relativity says black holes
• 16:58
  Speaker 1: live forever, and so that's a problem. The information is
• 17:01
  Speaker 1: still inside a black hole. It was just sort of
• 17:04
  Speaker 1: stuck there. And that's okay, except that we don't think
• 17:08
  Speaker 1: that black holes live forever. We think, thanks to Hawking radiation,
• 17:12
  Speaker 1: that black holes are not actually black. They give off
• 17:14
  Speaker 1: a little bit of radiation, they glow a tiny little bit,
• 17:18
  Speaker 1: and when they do that, they lose their mask because
• 17:21
  Speaker 1: they're giving off energy, So they get smaller and smaller
• 17:24
  Speaker 1: as it's called black hole evaporation, and eventually they disappear.
• 17:28
  Speaker 1: And so if your information about your banana was inside
• 17:31
  Speaker 1: the black hole and then the black hole evaporates, where's
• 17:34
  Speaker 1: the information? Did it disappear from the universe, you know?
• 17:38
  Speaker 1: Or did it somehow get leaked out in the Hawking radiation?
• 17:41
  Speaker 1: Is there a smell of banana once a black hole evaporations?
• 17:45
  Speaker 1: Is it in the air now? Stephen Hawking did a
• 17:48
  Speaker 1: really careful and sort of famous calculation where he showed
• 17:51
  Speaker 1: that the radiation itself has no information about anything inside
• 17:55
  Speaker 1: the black hole, only about the mass of the black hole.
• 17:57
  Speaker 1: So like, you can't tell what was inside the black
• 18:00
  Speaker 1: hole based on the Hawking radiation. So that's sort of
• 18:03
  Speaker 1: a mystery. Like the black hole disappears and the Hawking
• 18:06
  Speaker 1: radiation has just basically noise in it, So like, where
• 18:09
  Speaker 1: is the pattern for my banana? And that's the paradox
• 18:13
  Speaker 1: I see. The paradox is that it seems like information
• 18:16
  Speaker 1: hits the end of the road in a black hole,
• 18:19
  Speaker 1: whereas quantum mechanics would have you believed that it never
• 18:22
  Speaker 1: ends exactly, So somebody must be wrong, right, If information
• 18:26
  Speaker 1: is lost, then quantum mechanics is wrong, and that really
• 18:30
  Speaker 1: weakens the foundations of physics. If the information somehow escapes,
• 18:34
  Speaker 1: then that violens general relativity. Right, that's like information leaving
• 18:38
  Speaker 1: a black hole. How can that possibly happen? So it's
• 18:41
  Speaker 1: a super fascinating like sort of test bed to crash
• 18:43
  Speaker 1: these two theories together and say, well, you know, it's
• 18:46
  Speaker 1: like a cage match. Two theories go in and only
• 18:48
  Speaker 1: one comes out, and it depends on what happens next. Right, Yes, exactly,
• 18:53
  Speaker 1: it depends on what happens. No, No, I really have
• 18:56
  Speaker 1: a headache now. It feels like the Grandfather paradox, Like
• 18:59
  Speaker 1: if you put two theories into the black hole, but
• 19:02
  Speaker 1: only one of them can come out, but then the
• 19:04
  Speaker 1: black hole evaporates. What happens one of them is left
• 19:07
  Speaker 1: eating spaghetti? Yeah, the the Avengers movie maybe, And our
• 19:13
  Speaker 1: podcast episode about this, we talked about a few possible solutions.
• 19:16
  Speaker 1: You know. Hawking himself famously said that he thought information
• 19:19
  Speaker 1: was lost, that it just disappeared from the universe. But
• 19:22
  Speaker 1: most physicists don't believe that. Most physicists think that must
• 19:25
  Speaker 1: be wrong. That information is not lost. We just have
• 19:28
  Speaker 1: to figure out how it leaks out and So the
• 19:31
  Speaker 1: most popular theory until last year, until this recent progress
• 19:34
  Speaker 1: was made, was that maybe somehow there is information in
• 19:38
  Speaker 1: the Hawking radiation because the black hole surface is not
• 19:41
  Speaker 1: entirely smooth, like when you throw your banana onto the
• 19:44
  Speaker 1: black hole, maybe it gets like stretched out over the
• 19:47
  Speaker 1: event horizon but doesn't actually make a perfect sphere, and
• 19:50
  Speaker 1: that those little wiggles in the event horizons somehow contain
• 19:53
  Speaker 1: the information and influence the Hawking radiation. That was sort
• 19:56
  Speaker 1: of the direction people were going until recently interest ing.
• 20:01
  Speaker 1: So maybe you figure it out. Who comes out of
• 20:03
  Speaker 1: the cage? All right, Well, let's get into what this
• 20:07
  Speaker 1: potential solution is to the black hole information paradox and
• 20:11
  Speaker 1: most important, what does it mean. But first, let's take
• 20:13
  Speaker 1: a quick break. All right, we're talking about the black
• 20:28
  Speaker 1: hole information paradox and a potential solution to this paradox. Now, Daniel,
• 20:34
  Speaker 1: I guess maybe I'm having some trouble understanding why it's
• 20:37
  Speaker 1: a paradox, Like, you know, why can it be that,
• 20:41
  Speaker 1: for example, quantum mechanics does allow energy to always be
• 20:45
  Speaker 1: preserved except at a black hole, which is sort at
• 20:48
  Speaker 1: the end of the line, Do you know what I mean? Like,
• 20:50
  Speaker 1: why does it need to work everywhere and all the time. Well,
• 20:53
  Speaker 1: it really only means something if it works everywhere. You know,
• 20:56
  Speaker 1: momentum conservation is always meaningful if it's always conserved. You
• 20:59
  Speaker 1: know You're rules in your household are only meaningful if
• 21:01
  Speaker 1: your kids always follow them. Otherwise you know, what do
• 21:04
  Speaker 1: they even mean? So this is a bed robed principle
• 21:07
  Speaker 1: of quantum mechanics, and to have an exception at black
• 21:10
  Speaker 1: holes means there might be an exception somewhere else. And
• 21:12
  Speaker 1: basically it means it's not a foundational principle of quantum
• 21:15
  Speaker 1: mechanics that like information can disappear, stuff can be deleted
• 21:18
  Speaker 1: from the universe and you can have no record of
• 21:21
  Speaker 1: it ever having existed. That would just be a pretty
• 21:24
  Speaker 1: different universe from the one we thought we lived in.
• 21:26
  Speaker 1: Would be a catastrophe. We just have to figure out
• 21:28
  Speaker 1: some new theory that accommodates that, and a lot of
• 21:31
  Speaker 1: the assumptions we've been making would be wrong. So that's
• 21:34
  Speaker 1: kind of cool. That's like we say on this podcast
• 21:36
  Speaker 1: all the time, it would be awesome to knock down
• 21:39
  Speaker 1: a basic tenant of physics and discover something new. It's
• 21:42
  Speaker 1: just that that's a pretty big tenant, and so we're
• 21:45
  Speaker 1: pretty skeptical. You're pretty skeptical that there might be exceptions exactly.
• 21:50
  Speaker 1: I mean, it goes right back to the shorting or equation.
• 21:52
  Speaker 1: You know, the shorting or equation is unitary. It says
• 21:55
  Speaker 1: that probability is conserved. If you have a certain amount
• 21:57
  Speaker 1: of probability, it has to go somewhere, It doesn't just disappear.
• 22:01
  Speaker 1: And so that would be kind of weird but also fascinating,
• 22:04
  Speaker 1: like that would be a really interesting place to live,
• 22:06
  Speaker 1: and it wouldn't be the first time in the history
• 22:08
  Speaker 1: of physics that the universe was totally different in a
• 22:10
  Speaker 1: really basic way than the one we imagine. So we're
• 22:13
  Speaker 1: definitely keeping our minds open to that, but considering other
• 22:16
  Speaker 1: possibilities also, Right, all right, well, you say, one potential
• 22:20
  Speaker 1: solution is that maybe the black hole is sort of
• 22:23
  Speaker 1: leaking information when it evaporates like that somehow the evaporating
• 22:27
  Speaker 1: particles somehow carry away some of the information about the
• 22:30
  Speaker 1: black hole. That seems like a pretty good solution. But
• 22:33
  Speaker 1: what's the problem with that idea. Problem with that idea
• 22:36
  Speaker 1: of the event horizon not actually being smooth is that
• 22:39
  Speaker 1: then the information doesn't really go into the black hole.
• 22:42
  Speaker 1: It's just like stuck on the outside of the event
• 22:44
  Speaker 1: horizon so that it can radiate out, but then it
• 22:47
  Speaker 1: doesn't actually go into the black hole. So then you
• 22:49
  Speaker 1: need this like weird firewall, this like region where nothing
• 22:53
  Speaker 1: can actually go. Then like what's actually in the black hole? Right? Nothing?
• 22:58
  Speaker 1: That's sort of weird and require is this really strange
• 23:01
  Speaker 1: boundary that people can't really make sense of. The Other
• 23:04
  Speaker 1: problem with that is that it's hard to reconcile because
• 23:06
  Speaker 1: remember there's two ways to think about things falling into
• 23:09
  Speaker 1: a black hole. One from the outside when you're watching,
• 23:12
  Speaker 1: and you can never actually see the thing fall in
• 23:14
  Speaker 1: because of the gravitational time dilation. It takes infinite time
• 23:18
  Speaker 1: to fall in. You never actually see it fall in.
• 23:20
  Speaker 1: But the other point of view is from the point
• 23:22
  Speaker 1: of view of the thing falling in, and that just
• 23:24
  Speaker 1: passes right through the event horizon and heads to the singularity.
• 23:27
  Speaker 1: So it doesn't really make sense from the point of
• 23:29
  Speaker 1: view of the thing falling in for things to be
• 23:32
  Speaker 1: stuck on the event horizon. So it's not really a
• 23:35
  Speaker 1: workable solution, all right, I guess I mean trouble understanding
• 23:39
  Speaker 1: why exactly are you saying that you can have when
• 23:42
  Speaker 1: it evaporates, it can be sort of both coming out
• 23:46
  Speaker 1: and coming in at the same time. That's weird. Well,
• 23:48
  Speaker 1: it either needs to fall into the black hole or not, right,
• 23:51
  Speaker 1: And if it's information is encoded on the outside of
• 23:54
  Speaker 1: the event horizon, that means it hasn't really fallen into
• 23:57
  Speaker 1: the black hole. It's something like we're preventing it from
• 24:00
  Speaker 1: falling into the black hole. So then you need this
• 24:02
  Speaker 1: other thing, this firewall, preventing it. But we don't understand
• 24:06
  Speaker 1: what that would be or why that would be, and
• 24:08
  Speaker 1: it contradicts our view that you can fall into a
• 24:10
  Speaker 1: black hole from the point of view of the thing
• 24:12
  Speaker 1: falling in. So you need some whole other like idea
• 24:15
  Speaker 1: of what a black hole is to make that work.
• 24:17
  Speaker 1: So is this whole idea of evaporation theoretical or something
• 24:21
  Speaker 1: we understand thoroughly. Evaporation is not something we understand thoroughly,
• 24:25
  Speaker 1: and it is theoretical. Like, nobody's ever actually seen Hawking radiation,
• 24:30
  Speaker 1: So we say that black holes are not totally black,
• 24:32
  Speaker 1: but we've never actually seen one radiate anything. So this
• 24:35
  Speaker 1: is purely theoretical, and you know, it's an approximation like
• 24:39
  Speaker 1: Hawking did these calculations, but we don't really have a
• 24:41
  Speaker 1: theory to back them up. Like we have general relativity,
• 24:44
  Speaker 1: we have quantum mechanics, we don't have a theory of
• 24:47
  Speaker 1: quantum gravity when the combines the two, and that's really
• 24:50
  Speaker 1: what you need when things get both really really small
• 24:53
  Speaker 1: and really powerful gravitationally. Currently, we can do quantum mechanics
• 24:57
  Speaker 1: by ignoring gravity because gravity is very very small for
• 25:00
  Speaker 1: little particles that are affected by quantum mechanics. And when
• 25:03
  Speaker 1: we do gravity calculations we can ignore quantum mechanics because
• 25:06
  Speaker 1: quantum mechanical effects are small for the kinds of things
• 25:09
  Speaker 1: where we do get gravity calculations that are pretty big.
• 25:11
  Speaker 1: So inside black holes, we think you need a new
• 25:14
  Speaker 1: theory quantum gravity. Stephen Hawking didn't have this theory, but
• 25:17
  Speaker 1: it is sort of like a hand wavy calculation where
• 25:20
  Speaker 1: added a little bit of quantum mechanics to gravity, and
• 25:22
  Speaker 1: he came up with this calculation. But no, we've never
• 25:25
  Speaker 1: seen Hawking radiation, so we don't know that it's actually real.
• 25:28
  Speaker 1: I see. So when you say that the large Hadron
• 25:31
  Speaker 1: collider is producing black holes, but not to worry about it,
• 25:33
  Speaker 1: because they just evaporate. That's are you're saying. That's just
• 25:38
  Speaker 1: a big maybe there because Stephen Hawking sort of fudgeted. Yeah,
• 25:42
  Speaker 1: but the other half of that calculation that it would
• 25:44
  Speaker 1: be producing black holes relies on the same calculation. So
• 25:47
  Speaker 1: if we're producing them, then they are also evaporating. Oh,
• 25:50
  Speaker 1: I see, all right, so maybe it's not producing black holes.
• 25:54
  Speaker 1: I see, yeah, exactly. All right, Well then so that
• 25:57
  Speaker 1: doesn't work the idea that information can can leak out
• 26:00
  Speaker 1: through Hawking radiation. But now there's maybe a new theory
• 26:04
  Speaker 1: that could explain this paradox of what happens to the
• 26:06
  Speaker 1: information that goes into the black hole. And the approach
• 26:09
  Speaker 1: here is to add more quantum mechanics to the calculation,
• 26:12
  Speaker 1: to think, like, let's make this more quantum mechanical. Let's
• 26:14
  Speaker 1: add another concept and maybe they'll give us some insight.
• 26:18
  Speaker 1: And one that's been really appealing for getting information from
• 26:21
  Speaker 1: one place to the other is the idea of quantum entanglement.
• 26:24
  Speaker 1: We talk about this on the podcast, that two particles,
• 26:27
  Speaker 1: if they have a shared history, can have their fates intertwined.
• 26:30
  Speaker 1: Like if you have a particle with no spin and
• 26:32
  Speaker 1: it makes two particles that do have spin then those
• 26:35
  Speaker 1: spins have to be opposite in order to balance. Right,
• 26:37
  Speaker 1: you start out with zero spin have to end up
• 26:39
  Speaker 1: with zero spin. Quantum mechanics says that those two particles,
• 26:42
  Speaker 1: whether they're spin up or down, is not actually determined
• 26:45
  Speaker 1: until you measure one of them, So they're entangled even
• 26:48
  Speaker 1: if they're far away from each other in the universe.
• 26:51
  Speaker 1: So if one is created on Earth and the other
• 26:53
  Speaker 1: one is now sent out into space and they're kilometers apart,
• 26:56
  Speaker 1: and when you measure one of them, it determines the
• 26:58
  Speaker 1: spin at the other because they have to be opposite.
• 27:01
  Speaker 1: So that's cool because it feels sort of like a
• 27:03
  Speaker 1: way to get information from one place to another without
• 27:07
  Speaker 1: actually sending a message, right. It feels sort of like
• 27:10
  Speaker 1: this non local information transfer that you might want to
• 27:13
  Speaker 1: get information out of a black hole. Oh, I see,
• 27:16
  Speaker 1: So is the idea that then when something falls into
• 27:18
  Speaker 1: the black hole, it's actually entangled with something else outside
• 27:21
  Speaker 1: of it. Exactly. That's sort of the basis of the idea.
• 27:24
  Speaker 1: Before we dig into a little bit more, I just
• 27:26
  Speaker 1: want to add a caveat that for quantum entanglement, you
• 27:28
  Speaker 1: can't actually use entanglement to send information. You need also
• 27:33
  Speaker 1: some other sort of mechanism. And a lot of people
• 27:35
  Speaker 1: think that quantum entanglement is a way to send information
• 27:38
  Speaker 1: faster than the speed of light. But you can't do that.
• 27:40
  Speaker 1: But there is an important way that we need to
• 27:42
  Speaker 1: think about entanglement in order to attack this black hole
• 27:45
  Speaker 1: information paradox problem, and that's the Hawking radiation. Remember, Hawking
• 27:49
  Speaker 1: radiation is created when you have a particle antiparticle pair
• 27:52
  Speaker 1: created just outside the event horizon. One of them falls
• 27:55
  Speaker 1: in idea, another one flies out, which is the Hawking radiation.
• 27:58
  Speaker 1: If those two were created together, then they are entangled.
• 28:02
  Speaker 1: So now this Hawking radiation is somehow entangled with the
• 28:04
  Speaker 1: particle inside the black hole. And that's fascinating because it
• 28:09
  Speaker 1: tells you that, like maybe there's information there. Somehow, the
• 28:12
  Speaker 1: Hawking radiation has information about what's inside the black hole.
• 28:16
  Speaker 1: It's like at the moment of creation, it puts a
• 28:19
  Speaker 1: little bit of information into the black hole, but it
• 28:21
  Speaker 1: also takes away some information with it in the evaporation. Yeah,
• 28:25
  Speaker 1: and it doesn't contradict Hawking calculation. It says, look by itself,
• 28:29
  Speaker 1: the Hawking radiation, these particles that fly on from the
• 28:31
  Speaker 1: black hole, they don't have any information. You can't look
• 28:34
  Speaker 1: at them and tell what was inside the black hole,
• 28:36
  Speaker 1: but there might be some correlations there. There might be
• 28:39
  Speaker 1: some relationships between the Hawking radiation and what is inside
• 28:43
  Speaker 1: the black hole. And you can't tell what's inside the
• 28:46
  Speaker 1: black hole just by looking at the Hawking radiation, but
• 28:48
  Speaker 1: might be hidden in there. It's sort of like encrypted, right.
• 28:52
  Speaker 1: It's like if somebody can see how the computer represents
• 28:54
  Speaker 1: your password, but they don't actually know what your password is. Right,
• 28:57
  Speaker 1: they can just see those little dots on the screen
• 29:00
  Speaker 1: your pathwords in there, but you can't see it. So
• 29:03
  Speaker 1: maybe this information is in the Hawking radiation. It is
• 29:06
  Speaker 1: just sort of like encrypted by quantum entanglement. Interesting, but
• 29:10
  Speaker 1: that applies to the particle that gets evaporated and that
• 29:13
  Speaker 1: comes out. But what about my banana that I threw in?
• 29:15
  Speaker 1: What happens to my banana information? Oh, that's a good question.
• 29:19
  Speaker 1: What happens to your banana information? Well, your banana has
• 29:21
  Speaker 1: a quantum history, and so it is entangled with you,
• 29:25
  Speaker 1: who threw it in, and so it's much harder to
• 29:27
  Speaker 1: talk about quantum mechanics and macroscopic objects like bananas. But
• 29:31
  Speaker 1: in principle, your banana is entangled with you, and so
• 29:34
  Speaker 1: even if you throw it into the black hole, it's
• 29:36
  Speaker 1: information is still connected to you somehow, Like I still
• 29:40
  Speaker 1: remember the banana. Is what you're saying exactly, you are
• 29:43
  Speaker 1: the hawking radiation. In that case, my dear memories of
• 29:47
  Speaker 1: that banana are somehow still preserving the information about in
• 29:52
  Speaker 1: the years. Is that true? Is that kind of what
• 29:54
  Speaker 1: this new solution is about. It's just that you know,
• 29:57
  Speaker 1: everything is entangled with each other and so you never
• 29:59
  Speaker 1: really lo is it when it goes into the black hole?
• 30:01
  Speaker 1: Is that the basic outline of the solution. That's not
• 30:03
  Speaker 1: the solution. It's another way to look at the problem
• 30:06
  Speaker 1: because it doesn't actually solve the problem. It just sort
• 30:08
  Speaker 1: of restates it. But it restates in a way that
• 30:10
  Speaker 1: we then can attack. And here's why it's not actually
• 30:13
  Speaker 1: a solution to the problem. Think about what happens as
• 30:15
  Speaker 1: the black hole evaporates. As the black hole gets smaller
• 30:18
  Speaker 1: and smaller, you have all this hawking radiation that was
• 30:20
  Speaker 1: created entangled with stuff inside the black hole. But now
• 30:24
  Speaker 1: the black hole is disappearing, So where is that entanglement going.
• 30:27
  Speaker 1: Then the hawking radiation is like entangled with something that
• 30:30
  Speaker 1: has disappeared, and so you sort of have the same problem, right,
• 30:34
  Speaker 1: it's just sort of stated in a different way. So
• 30:37
  Speaker 1: what we need is a way to figure out how
• 30:39
  Speaker 1: entanglement for a black hole can start at zero, and
• 30:42
  Speaker 1: then during the black hole's lifetime it can grow. As
• 30:45
  Speaker 1: it's evaporating, it's giving off Hawking radiation, which is now
• 30:48
  Speaker 1: getting entangled with the stuff inside of it somehow. Then
• 30:51
  Speaker 1: that entanglement has to get back down to zero. All
• 30:54
  Speaker 1: those entanglements have to get broken or somehow resolved before
• 30:58
  Speaker 1: the black hole evaporates. So that's this newer way of
• 31:01
  Speaker 1: looking at the problem. This way that one of Hawking students,
• 31:03
  Speaker 1: Don Page came up with, and that's sort of the
• 31:05
  Speaker 1: crevice that these new groups attacked in order trying to
• 31:08
  Speaker 1: figure out what's going on. Oh I see it is
• 31:11
  Speaker 1: that like I'm entangled to my banana. I remember it fondly.
• 31:15
  Speaker 1: I remember the curvature and the just how many spots
• 31:18
  Speaker 1: and how sweet it was, Oh banana, I eat eu well.
• 31:21
  Speaker 1: And so then the banana goes into the black hole.
• 31:24
  Speaker 1: Inside the black hole, it gets entangled with particles being evaporated,
• 31:28
  Speaker 1: which means that the you know, evaporating particle that comes
• 31:31
  Speaker 1: out is somehow entangled to the banana which was entangled
• 31:35
  Speaker 1: to me. Yeah, Or more directly, if you throw it
• 31:38
  Speaker 1: into the black hole, you are still entangled with that banana.
• 31:41
  Speaker 1: You don't need hawking radiation for that. But then your
• 31:43
  Speaker 1: information about the bananas somehow in the black hole, right,
• 31:47
  Speaker 1: and then as the black hole is evaporating, you wonder,
• 31:50
  Speaker 1: like what happens to that entanglement? Instead of thinking about
• 31:53
  Speaker 1: like this information stuck inside the black hole, think about
• 31:56
  Speaker 1: in terms of the entanglement, how can I be entangled
• 31:58
  Speaker 1: with something which is then just appearing. Where does that
• 32:01
  Speaker 1: entanglement go? Does the entanglement and gets passed onto the
• 32:05
  Speaker 1: evaporating particle? Is that the idea? That's the question, right,
• 32:08
  Speaker 1: how do you somehow go from having entanglement to getting
• 32:11
  Speaker 1: zero entanglement? Like, the black hole is definitely creating entangled
• 32:15
  Speaker 1: pairs because things are falling into the black hole and
• 32:17
  Speaker 1: they are entangled with whatever they came from hawking radiation
• 32:21
  Speaker 1: or Jorge throwing a banana, And the question is then
• 32:24
  Speaker 1: how do you get a black hole to break those
• 32:26
  Speaker 1: entanglements somehow? All right, so then it's somehow preserved and
• 32:30
  Speaker 1: so what's been the progress in the last year. So
• 32:33
  Speaker 1: a bunch of smart young theories attack this problem and
• 32:36
  Speaker 1: they came up with a new way to do this calculation. See,
• 32:38
  Speaker 1: the problem is that nobody knows even how to calculate
• 32:41
  Speaker 1: this entanglement. Like we say, entanglement has a start from
• 32:44
  Speaker 1: zero for a black hole, that it has to grow,
• 32:46
  Speaker 1: that it has to come back down to zero. Problem is,
• 32:48
  Speaker 1: we don't have a theory of quantum gravity, so we
• 32:50
  Speaker 1: don't understand how to calculate entanglement, which is a quantum concept,
• 32:54
  Speaker 1: in the environment of a black hole, which is a
• 32:56
  Speaker 1: gravitational concept. So until now, nobody even knew like how
• 32:59
  Speaker 1: do we calculate this thing. We know it has to
• 33:01
  Speaker 1: start a zero, go up and come down, but we
• 33:03
  Speaker 1: don't know how to calculate it. So what they did
• 33:05
  Speaker 1: is they came up with a clever new approach theoretically
• 33:07
  Speaker 1: to do this calculation. And if you read their papers,
• 33:10
  Speaker 1: it's like a bunch of crazy mathematical tricks they do.
• 33:14
  Speaker 1: They take the problem, they transform into something else and
• 33:16
  Speaker 1: they apply this tool and they put in wormholes and
• 33:18
  Speaker 1: they do this calculation. It's like a real like tourtive
• 33:22
  Speaker 1: force of mathematical tricks. And what they've done is they
• 33:26
  Speaker 1: figured out a way to sort of calculate the entanglement
• 33:29
  Speaker 1: of this black hole over its lifetime. And in their calculation,
• 33:33
  Speaker 1: they see the entanglement going up, peeking, and then coming
• 33:37
  Speaker 1: back down. Interesting, what do you mean they put in
• 33:39
  Speaker 1: some wormholes. You can just do that. You can sprinkle
• 33:41
  Speaker 1: in some wormholes. Yeah, exactly. They use wormholes as just
• 33:46
  Speaker 1: a sort of a way to do these calculations. You know,
• 33:49
  Speaker 1: sometimes you attack a math problem, you don't know how
• 33:51
  Speaker 1: to do it, so you transform it into something else.
• 33:54
  Speaker 1: And so what they did is they transformed the problem
• 33:56
  Speaker 1: from one kind of problem into another one where they
• 33:58
  Speaker 1: could use wormholes that they knew how to calculate. I
• 34:01
  Speaker 1: don't know how to integrate this thing, but I'll transform
• 34:03
  Speaker 1: into this other thing that I do know how to integrate.
• 34:05
  Speaker 1: There's a lot of details there about how they did
• 34:07
  Speaker 1: this calculation. For example, nobody knows how to calculate entanglement
• 34:12
  Speaker 1: in four dimensional space with gravity. So they did two things.
• 34:15
  Speaker 1: When they said, well, let's just take it down a
• 34:17
  Speaker 1: couple of notches and think about, you know, two dimensional
• 34:20
  Speaker 1: black holes instead of four dimensional black holes. Does that
• 34:23
  Speaker 1: mean that you have to assume that there are wormholes
• 34:25
  Speaker 1: inside of the black hole. These wormholes are more of
• 34:28
  Speaker 1: a mathematical trick than actual physical wormholes. But in a
• 34:31
  Speaker 1: minute we could talk about what the solution means and
• 34:33
  Speaker 1: whether they're actually are wormholes connecting the inside of the
• 34:37
  Speaker 1: black hole to the outside. But for now, just think
• 34:39
  Speaker 1: of a sort of a mathematical trick that they did
• 34:41
  Speaker 1: in order to get to a number. And the thing
• 34:44
  Speaker 1: to understand about this calculation is like, they don't understand
• 34:48
  Speaker 1: how the information is getting out. It's not like they
• 34:50
  Speaker 1: found some mechanism where they're like, oh, look, here's some
• 34:52
  Speaker 1: little holes in the event horizon. They just figured out
• 34:54
  Speaker 1: a way to do this calculation and it has the
• 34:56
  Speaker 1: shape they expected to have. If black holes are leaking information,
• 35:01
  Speaker 1: that doesn't mean they know how it's happening. It's like
• 35:03
  Speaker 1: if you see your fridge temperature is rising, you don't
• 35:06
  Speaker 1: necessarily know where the leak is in your fridge. You
• 35:08
  Speaker 1: just know that somehow somewhere heat is getting in. I see.
• 35:13
  Speaker 1: The solution also sort of supposes that black holes are
• 35:16
  Speaker 1: not perfectly smooth inside. Right, there's some crazy interpretation of
• 35:21
  Speaker 1: these calculations, and I say interpretation, because these calculations are
• 35:24
  Speaker 1: their mathematical and how they relate to physicality is complicated,
• 35:28
  Speaker 1: and the cosmologist I talked to really disagree about whether
• 35:31
  Speaker 1: you can make any physical interpretation about like what's happening,
• 35:35
  Speaker 1: because sometimes this information exists in this sort of abstract
• 35:38
  Speaker 1: space we call Hilbert space for quantum mechanics, not in
• 35:41
  Speaker 1: a physical space, but there is sort of a cartoon
• 35:44
  Speaker 1: picture that you can draw to try to get an
• 35:46
  Speaker 1: understanding of what's going on, and it involves really crazy
• 35:50
  Speaker 1: things like perhaps inside the black hole, it's not actually
• 35:53
  Speaker 1: all black hole. Maybe there's like an island inside the
• 35:57
  Speaker 1: black hole where radiation can fall, and it's sort of
• 36:02
  Speaker 1: no longer part of the black hole. It's part of
• 36:04
  Speaker 1: this like quantum radiation island. It's physically inside the black hole.
• 36:09
  Speaker 1: But now the black hole, instead of being like a sphere,
• 36:11
  Speaker 1: is sort of like a shell. You know, it has
• 36:13
  Speaker 1: like a hollow core, and that hollow core is not
• 36:16
  Speaker 1: black holy anymore. What Yeah, Well, how can a black
• 36:21
  Speaker 1: hole not be a black hole? Inside of a black hole,
• 36:24
  Speaker 1: it's a double decker, it's like multilayer. So the idea
• 36:27
  Speaker 1: is that like it's just like a normal classical black
• 36:29
  Speaker 1: hole in the shell part, but then the core of
• 36:32
  Speaker 1: it has this other weird quantum gravity thing going on
• 36:35
  Speaker 1: that we don't yet understand. But we think that maybe
• 36:37
  Speaker 1: stuff inside the black hole is like falling into this
• 36:41
  Speaker 1: quantum island, and that quantum island is entangled with the
• 36:45
  Speaker 1: stuff that has come out, and so this is how
• 36:47
  Speaker 1: things can like sort of leave the black hole without
• 36:50
  Speaker 1: passing through the classical event horizon. Again, people disagree about
• 36:53
  Speaker 1: whether this is like a cartoon picture just for sort
• 36:56
  Speaker 1: of understanding the calculations, or what's really going on inside
• 36:59
  Speaker 1: a black hole. All right, well, let's get into what
• 37:02
  Speaker 1: this potential solution might actually mean, like have we actually
• 37:06
  Speaker 1: solved the paradox or are we still a long ways away?
• 37:10
  Speaker 1: But first let's take a quick break. All right, Daniel,
• 37:26
  Speaker 1: it sounds like maybe they have a new way to attack,
• 37:30
  Speaker 1: finding a potential solution to a potentially imaginary, not quite
• 37:35
  Speaker 1: sure paradox about black holes. Right, Did I get that right? Yeah?
• 37:39
  Speaker 1: I think you did. There's enough qualifiers there. You know,
• 37:42
  Speaker 1: this is exciting because people for a long time thought
• 37:45
  Speaker 1: we wouldn't make progress on this for decades until we
• 37:48
  Speaker 1: came up with a theory of quantum gravity. How can
• 37:50
  Speaker 1: we even calculate the level of the entanglement of the
• 37:52
  Speaker 1: inside of the black hole and the outside of the
• 37:54
  Speaker 1: black hole if we can't do quantum gravity calculations. So
• 37:58
  Speaker 1: this is exciting, but it's not exactly like a full answer, right.
• 38:01
  Speaker 1: It's sort of like we were able to without coming
• 38:04
  Speaker 1: up with the theory quantum gravity. We still don't have one.
• 38:06
  Speaker 1: We were able to do this one calculation, and that
• 38:10
  Speaker 1: calculation says something amazing. It says that the entanglement decreases,
• 38:14
  Speaker 1: and it's a special moment halfway through the lifetime of
• 38:18
  Speaker 1: a black hole when the entanglement just starts to drop.
• 38:21
  Speaker 1: It's like the midlife crisis of a black hole. And
• 38:24
  Speaker 1: that suggests if this calculation is correct, then it means
• 38:27
  Speaker 1: what we think. It means that information does leak out
• 38:31
  Speaker 1: of black holes. The things you throw into a black
• 38:33
  Speaker 1: hole are not lost forever. That's when the black hole
• 38:35
  Speaker 1: gets desperate and absorbs a Ferrari or something and expensive
• 38:39
  Speaker 1: sports car or something. Yeah, where it leaks out of
• 38:42
  Speaker 1: Ferrari right exactly. It's been hoarding its stuff for all
• 38:45
  Speaker 1: of its lifetime and then it decides, oh my God,
• 38:47
  Speaker 1: I gotta spend all this mass before I evaporate, and
• 38:50
  Speaker 1: it starts leaking up bananas and Ferrari's and everything. I
• 38:52
  Speaker 1: guess this idea that black holes have a lifespan depend
• 38:56
  Speaker 1: on the idea that black holes at some point stop
• 39:00
  Speaker 1: eating stuff, right, Like, you have to starve a black
• 39:02
  Speaker 1: hole for it to disappear. Oh, absolutely, yeah. This is
• 39:06
  Speaker 1: only the case of an isolated black hole. If you
• 39:08
  Speaker 1: kept feeding a black hole, it would just keep growing.
• 39:11
  Speaker 1: This is what would happen if you had a really
• 39:12
  Speaker 1: big black hole and then you left it totally isolated.
• 39:15
  Speaker 1: General relativity says it will sit there forever. Quantum mechanical
• 39:19
  Speaker 1: modifications to general relativity by Stephen Hawking say no, actually,
• 39:23
  Speaker 1: they will radiate a little bit, leak out mass, and
• 39:26
  Speaker 1: eventually disappear and evaporate in a blinding flash of light
• 39:30
  Speaker 1: at the very end. Because the evaporation happens more quickly
• 39:33
  Speaker 1: for small black holes, so you get more evaporation near
• 39:36
  Speaker 1: the end of the life So the beginning of the
• 39:38
  Speaker 1: life cycle like a little bit. But then as the
• 39:40
  Speaker 1: black hole shrinks and shrinks, it gets brighter and brighter,
• 39:43
  Speaker 1: all right, So then this potential solution says that maybe
• 39:46
  Speaker 1: information is not completely destroyed. It sounds like the idea said,
• 39:49
  Speaker 1: you throw a banana in. The banana SML falls into
• 39:53
  Speaker 1: a pocket of non black holiness inside of the black hole,
• 39:57
  Speaker 1: in which it could get maybe entangled with a particle
• 40:00
  Speaker 1: that's evaporating from the black hole. Therefore, then the evaporating
• 40:03
  Speaker 1: particle it still carries a little bit of the banana
• 40:06
  Speaker 1: with it, Yeah, exactly. And they don't really have an
• 40:09
  Speaker 1: understanding at all for how this information leaks out, Like
• 40:12
  Speaker 1: as you say, the banana falls in, it's entangled with
• 40:14
  Speaker 1: you somehow. That banana's information then moves from the pure
• 40:19
  Speaker 1: black hole state into this weird quantum island, and so
• 40:22
  Speaker 1: it's not really counted as part of the black hole anymore.
• 40:25
  Speaker 1: And then as the black hole is evaporating, is a
• 40:28
  Speaker 1: shell now and it's just basically shrinks down to surround
• 40:31
  Speaker 1: this quantum island and then disappears, and so then all
• 40:33
  Speaker 1: that information is still there. Again, cosmologists are really hesitant
• 40:37
  Speaker 1: to like tie the location of this information with anything physical,
• 40:41
  Speaker 1: So there are some really tricky questions here, and so
• 40:44
  Speaker 1: I reached out to one of the theorists who is
• 40:45
  Speaker 1: actively working on these problems and has been involved in
• 40:48
  Speaker 1: some of this recent progress. Professor Netta inglehearted m I
• 40:51
  Speaker 1: t to tell us a little bit more about it. Netta,
• 40:54
  Speaker 1: thank you very much for joining us pleasure, thank you
• 40:57
  Speaker 1: for having me. So. My first question is I think
• 40:59
  Speaker 1: we've I think at a mental picture, if possible, of
• 41:02
  Speaker 1: what happens when halfway through the life of the black
• 41:06
  Speaker 1: hole the entropy suddenly starts to decrease. Your papers talk
• 41:10
  Speaker 1: about this quantum extremal surface that divides the black hole
• 41:14
  Speaker 1: into these two regions. Can you tell us a little
• 41:16
  Speaker 1: bit about this surface, how it appears, and then what
• 41:19
  Speaker 1: the two regions are like. Is it possible to get
• 41:21
  Speaker 1: a mental picture? I can certainly try. So let me
• 41:25
  Speaker 1: maybe say a few words about what a quantum extremal
• 41:29
  Speaker 1: surface is and what what maybe starting with what we
• 41:31
  Speaker 1: mean by an extremal surface to begin with, So, why
• 41:35
  Speaker 1: does an extremal surface why do we call it an
• 41:37
  Speaker 1: extremal surface. So an extremal surface is a surface whose
• 41:42
  Speaker 1: area doesn't change when you jiggle it a little bit.
• 41:47
  Speaker 1: So if you slightly, ever so slightly modify the location
• 41:51
  Speaker 1: of the surface just a little bit, then the area
• 41:54
  Speaker 1: of the surface does not change. Now, where does this
• 41:57
  Speaker 1: quantum bit come in. What is that quantum extreme more surface. Well,
• 42:01
  Speaker 1: it's a little bit like a quantum corrected area. So
• 42:05
  Speaker 1: what is the quantum corrected area like the area plus
• 42:08
  Speaker 1: a contribution from from quantum fields, a contribution from the
• 42:13
  Speaker 1: entropy of of quantum fields that are just living in
• 42:17
  Speaker 1: your universe, and a quantum extremal surface is kind of
• 42:21
  Speaker 1: what it sounds like. It means that the sum of
• 42:24
  Speaker 1: the area of the surface with the entropy of of
• 42:28
  Speaker 1: quantum fields, this quantum contribution to the area's count corrected
• 42:32
  Speaker 1: area doesn't change when you slightly jiggle the location of
• 42:36
  Speaker 1: this surface. So that's the sort of definition of a
• 42:40
  Speaker 1: quantum extremal surface. And so indeed, in the black hole
• 42:44
  Speaker 1: information paradox and the recent developments, what we have found
• 42:49
  Speaker 1: is that the difference between extrememal and quantum extreme all
• 42:54
  Speaker 1: is exactly what it takes two allow us to see
• 42:58
  Speaker 1: the signature of information conservation. It is this critical difference
• 43:02
  Speaker 1: between whether the area can be increasing even though the
• 43:06
  Speaker 1: overall quantum corrective area is not. That is this this
• 43:10
  Speaker 1: critical and new ingredient in a very frazy new developments
• 43:15
  Speaker 1: over the past two years that have been some sense
• 43:18
  Speaker 1: in a renaissance in the in the black hole information paradox.
• 43:22
  Speaker 1: Can we think of this as a physical surface or
• 43:24
  Speaker 1: is this sort of like an intellectual dividing point for
• 43:27
  Speaker 1: using New Year calculations? Is that a real physical thing
• 43:30
  Speaker 1: where the space is different inside and outside the surface.
• 43:33
  Speaker 1: It's a real physical surface in the sisse that it
• 43:35
  Speaker 1: lives in spacetime. It's physical in another way, which is
• 43:38
  Speaker 1: also nice, and that if you had a family of
• 43:41
  Speaker 1: observers who were sitting closely spaced along the surface, and
• 43:45
  Speaker 1: they were able to each of them could measure what
• 43:49
  Speaker 1: light rays are doing at the surface. So, in other words,
• 43:51
  Speaker 1: if you had a ball and he had observers all
• 43:53
  Speaker 1: around the ball, and each one of them measured in
• 43:55
  Speaker 1: their own the own little small neighborhood, whether light rays
• 43:59
  Speaker 1: are expanding or away from the ball or contracting, and
• 44:02
  Speaker 1: you put all those observations together, you would be able
• 44:05
  Speaker 1: to tell this is a quantum extremal surface. So this
• 44:08
  Speaker 1: is something which is in principle observable the location of
• 44:12
  Speaker 1: that surface. Of course, we expect that if you're seeing
• 44:15
  Speaker 1: a quantum extremal surface, it is already too late to
• 44:19
  Speaker 1: communicate that to someone who is standing outside of the
• 44:22
  Speaker 1: black hole. So then, how does this quantum extremeal surface
• 44:25
  Speaker 1: help us understand the decrease in entanglement of the black
• 44:29
  Speaker 1: hole the interior of the black hole, with the Hawking
• 44:32
  Speaker 1: rediation already produced in the first half of the black
• 44:34
  Speaker 1: hole's lifetime, does it break that entanglement or do later
• 44:38
  Speaker 1: particles now get entangled with earlier particles? How does the
• 44:41
  Speaker 1: entanglement actually decrease? That's an excellent question. How do we
• 44:45
  Speaker 1: actually understand the way in which information gets out? I
• 44:49
  Speaker 1: think this is what you're really asking, how do we
• 44:51
  Speaker 1: actually understand the entanglement entropy? And the fact of the
• 44:55
  Speaker 1: matter is that we now have two ways of computing
• 44:58
  Speaker 1: the entanglement entropy of hawk mediation, either Hawking's original calculation,
• 45:03
  Speaker 1: which tells you that you have information loss, or the
• 45:06
  Speaker 1: quantum extremal surface prescription, which keeps you information conservation. The
• 45:10
  Speaker 1: quantum extremal surface prescription has some grounding in the holographic correspondence.
• 45:16
  Speaker 1: It has derivations coming from the holographic correspondence, which is
• 45:20
  Speaker 1: very well motivated, but nevertheless still like conjecture, And in particular,
• 45:25
  Speaker 1: when I say that not thinking that it might be wrong,
• 45:28
  Speaker 1: but thinking that we don't have a derivation of it,
• 45:32
  Speaker 1: and so it is difficult to put on the same
• 45:35
  Speaker 1: footing Hawkings calculation and the quantum extremal surface prescription and
• 45:39
  Speaker 1: simply ask where did Hawking go wrong? Because right now
• 45:42
  Speaker 1: we have two completely different calculations of the same thing
• 45:46
  Speaker 1: that don't talk to each other, and we don't know
• 45:49
  Speaker 1: how to poured over those insights from the quantum extremal
• 45:52
  Speaker 1: surface prescription into the same model that Hawking was working with.
• 45:57
  Speaker 1: Now I say we don't know how to do that,
• 45:59
  Speaker 1: but I should also say that's a very active area
• 46:02
  Speaker 1: of investigation. So given how quickly thinks have moved in
• 46:06
  Speaker 1: the past couple of years, I expect that our ignorance
• 46:09
  Speaker 1: of this is not going to last much longer. All right,
• 46:11
  Speaker 1: So do you have like a cartoony picture in your
• 46:14
  Speaker 1: mind of you know, what's happening to these particles? You know,
• 46:17
  Speaker 1: I understand it's not easy to transport your calculation from
• 46:21
  Speaker 1: one regime into this this sort of picture that we
• 46:25
  Speaker 1: have in our heads. But what picture do you have
• 46:27
  Speaker 1: in your mind when you think about where the information
• 46:29
  Speaker 1: is going? Where the information is going is complicated, but
• 46:33
  Speaker 1: I can tell you what my opinion is on what's
• 46:38
  Speaker 1: missing from say, Hawking circulation that's included in the quantum
• 46:42
  Speaker 1: extremal surface calculation. And I should preface this by saying
• 46:45
  Speaker 1: that this is a wild speculation that is not at
• 46:48
  Speaker 1: all currently back by anything that I have derived or done,
• 46:52
  Speaker 1: which is that there's a very beautiful paper by Harlowe
• 46:56
  Speaker 1: and Hayden in which they discussed how complicated it is
• 47:00
  Speaker 1: to decode the Hawking radiation, and then the assumption that
• 47:04
  Speaker 1: Hawking radiation it does sort of purify itself, so at
• 47:07
  Speaker 1: the end the information is conserved in the process. Then
• 47:12
  Speaker 1: it's still i would say, exponentially difficult in terms of
• 47:16
  Speaker 1: computational complexity to decode the Hawking radiation, to understand exactly
• 47:23
  Speaker 1: to see unitarities exponentially complicated. We might speculate that Hawking
• 47:28
  Speaker 1: calculation in some sense did not include those exponentially complicated
• 47:34
  Speaker 1: operations exponentially complicated information. When you look at Hawking calculation,
• 47:39
  Speaker 1: do you see the team missed anything? Now, so then
• 47:42
  Speaker 1: there's a question, how would we see this exponential complexity,
• 47:45
  Speaker 1: where is it hiding? How did Hawking miss it? In
• 47:49
  Speaker 1: all honesty, that's very much an open area of research
• 47:52
  Speaker 1: right now, we just don't know. All right, Well, thanks
• 47:54
  Speaker 1: very much for sharing your thinking about this really fun
• 47:57
  Speaker 1: and fascinating puzzle about these corner of the universe. Really
• 48:01
  Speaker 1: appreciate your time. So that was my fun conversation with
• 48:04
  Speaker 1: Nada Englehart, who tried to help us get a mental
• 48:07
  Speaker 1: picture of what's going on. And it's sort of amazing
• 48:10
  Speaker 1: because it means basically quantum mechanics was right. It means that, yeah,
• 48:14
  Speaker 1: information is not destroyed. It's there. It will not disappear
• 48:17
  Speaker 1: from the universe, even if it has to like hide
• 48:19
  Speaker 1: in some little weird quantum island at the core of
• 48:22
  Speaker 1: a black hole. It will persist, right, I guess the
• 48:25
  Speaker 1: question is could you decode that information? Like if you,
• 48:28
  Speaker 1: you know, trillions of years from now in the future,
• 48:30
  Speaker 1: someone looking at our black holes evaporating, could they like,
• 48:33
  Speaker 1: you know, make up, Oh there's more banana there. That's
• 48:36
  Speaker 1: the question, you know, can you decode this information that
• 48:39
  Speaker 1: was the subject of this fun TV show called Dev's
• 48:42
  Speaker 1: you know that basically built on this whole concept that
• 48:45
  Speaker 1: couldn't you take a scan of the Earth now and
• 48:48
  Speaker 1: use that to reconstruct history? Could you know, see Jesus
• 48:51
  Speaker 1: on the cross or important historical events just based on
• 48:54
  Speaker 1: you know where air molecules are today, and in principle
• 48:58
  Speaker 1: if possible, but in practice it would require knowing the
• 49:01
  Speaker 1: quantum state of all of these particles so you could
• 49:03
  Speaker 1: properly get them back in time, and that would be
• 49:06
  Speaker 1: essentially impossible even with a quantum computer, but in principle
• 49:10
  Speaker 1: it is possible. And so if this information does leak
• 49:13
  Speaker 1: out of black holes in terms of Hawking radiation, then
• 49:16
  Speaker 1: in principle you could decoded. And the physicist actually did
• 49:19
  Speaker 1: a really fun sort of thought experiment to how you
• 49:21
  Speaker 1: could make that work That involves like weird informational wormholes. Oh,
• 49:26
  Speaker 1: great sprinkle and more wormholes? Why not? The way they
• 49:30
  Speaker 1: think you might be able to do it is to
• 49:32
  Speaker 1: run a simulation of a black hole on a quantum computer.
• 49:37
  Speaker 1: To take a quantum computer which can represent these quantum
• 49:40
  Speaker 1: states fairly naturally, and run a simulation of the black
• 49:43
  Speaker 1: hole and compare the Hawking radiation you get from the
• 49:45
  Speaker 1: real black hole to the simulated ones. So then if
• 49:48
  Speaker 1: you find a simulated black hole that has the same
• 49:50
  Speaker 1: pattern of radiation as you're a real one, then you
• 49:53
  Speaker 1: can peer inside of it and see this must have
• 49:56
  Speaker 1: been what was inside the black hole. What, but would
• 50:00
  Speaker 1: have to match like every particle that comes out of it, Yeah, exactly,
• 50:03
  Speaker 1: It would be tricky. But if you do that, then
• 50:06
  Speaker 1: something really weird happens. In their calculations, they suggest that
• 50:10
  Speaker 1: a wormhole is essentially created between the real black hole
• 50:14
  Speaker 1: and the simulated black hole in your quantum computer. What
• 50:19
  Speaker 1: it's like an informational black hole, like a virtual black hole. Yeah,
• 50:24
  Speaker 1: because then that information is now being revealed from the
• 50:27
  Speaker 1: core of the black hole, a real black hole, to
• 50:30
  Speaker 1: the one in your simulation in your quantum computer. And
• 50:33
  Speaker 1: so there's like, how does that information get from there
• 50:36
  Speaker 1: to there? It's this weird non local effect, and so
• 50:39
  Speaker 1: non local information transfer can really only be done by wormholes,
• 50:43
  Speaker 1: which connect different places in space and time. So like,
• 50:46
  Speaker 1: that's pretty weird. If you run a program which creates
• 50:48
  Speaker 1: a wormhole between your computer and a real black hole,
• 50:52
  Speaker 1: whoa creates like a little bookatiny channel or something between
• 50:56
  Speaker 1: the two. All right, well, I guess the big question
• 51:01
  Speaker 1: is what does this mean? Does this mean that we've
• 51:02
  Speaker 1: solved or we think we may have solved this kind
• 51:06
  Speaker 1: of like conflict between quantum mechanics and general relativity or
• 51:10
  Speaker 1: does this sort of side step that conflict. It sort
• 51:13
  Speaker 1: of sidesteps the conflict, right, it doesn't really get to solution.
• 51:16
  Speaker 1: The solution would be a full theory of quantum gravity,
• 51:19
  Speaker 1: one that tells us what happens really small distances and
• 51:23
  Speaker 1: powerful gravity, which is not something that's easy to test,
• 51:26
  Speaker 1: right because small distances you only have little particles, and
• 51:29
  Speaker 1: little particles have very small amounts of mass and gravity
• 51:32
  Speaker 1: super duper weak, so we can't really do gravity experiments
• 51:36
  Speaker 1: with tiny particles, so it's pretty rare we get to
• 51:38
  Speaker 1: even explore this regime experimentally to like see what happens,
• 51:41
  Speaker 1: which is why black holes in their interiors are such
• 51:44
  Speaker 1: a valuable test. Ben So we think we need like
• 51:47
  Speaker 1: a theory of quantum gravity to really resolve this. And
• 51:50
  Speaker 1: the fascinating thing about making progress like this on a
• 51:53
  Speaker 1: big question is that it's a bit disappointing and exhilarating.
• 51:57
  Speaker 1: Like it's disappointing because people fought you need a quantum
• 52:01
  Speaker 1: gravity to answer this question, So now answering it without
• 52:05
  Speaker 1: the getting the theory quantum gravity is sort of like,
• 52:07
  Speaker 1: oh darn, you know, we thought maybe this was like
• 52:10
  Speaker 1: a thread we could pull on to reveal the truth
• 52:13
  Speaker 1: theory of quantum gravity. Instead, we only sort of like,
• 52:16
  Speaker 1: you know, pull the thread and got the end of
• 52:18
  Speaker 1: the thread. We didn't really like get the whole thing
• 52:20
  Speaker 1: to unravel. Basically, physicists are never happy. You find a solution,
• 52:24
  Speaker 1: you're happy and unhappy, And you don't find a solution,
• 52:27
  Speaker 1: you're happy and unhappy. We're in a superposition of happy
• 52:30
  Speaker 1: and unhappy at all entangled happiness there. And also remember
• 52:35
  Speaker 1: that not everybody really believes in this solution. There are
• 52:39
  Speaker 1: folks out there that are just like, no, there's too
• 52:41
  Speaker 1: many mathematical tricks there. I don't really buy it. It's
• 52:44
  Speaker 1: sort of a little bit controversial still, and you know,
• 52:47
  Speaker 1: there's reasons to be skeptical. Like to do this calculation,
• 52:51
  Speaker 1: they did this weird trick where they said, I don't
• 52:54
  Speaker 1: know how to do a calculation in four dimensional space
• 52:57
  Speaker 1: with gravity, but I can do a similar calculation on
• 53:00
  Speaker 1: a three dimensional space that has no gravity. And there's
• 53:04
  Speaker 1: this famous result in physics from about twenty five years
• 53:07
  Speaker 1: ago showing that those two calculations should be the same.
• 53:10
  Speaker 1: You take a four dimensional space that has gravity in it,
• 53:13
  Speaker 1: and you should be able to instead get all the
• 53:15
  Speaker 1: information about that space just by looking at like a
• 53:17
  Speaker 1: three D surface around that four D space, And in
• 53:20
  Speaker 1: the three D surface there is no gravity, there's just
• 53:22
  Speaker 1: quantum mechanics. So they did their calculation on this like
• 53:26
  Speaker 1: three D surface, not in the actual gravity of a
• 53:29
  Speaker 1: black hole. And so some people feel like maybe that's cheating.
• 53:33
  Speaker 1: Other people feel like, know that connection is real. It's
• 53:36
  Speaker 1: a mathematical trick, but it's real and it's reflective of
• 53:39
  Speaker 1: the way our universe works. So there's still sort of
• 53:41
  Speaker 1: a lot of controversy about whether this will hold up.
• 53:44
  Speaker 1: Just throw all those physics into the black hole and
• 53:46
  Speaker 1: then them doke it out. Yeah, and you know, we
• 53:49
  Speaker 1: have the East Coast versus the West coast. There's two
• 53:52
  Speaker 1: different calculations, two different strategies for doing this calculation that
• 53:56
  Speaker 1: got dissimilar results, and so that's sort of reassuring, but
• 54:00
  Speaker 1: it's also sort of fun because you get like East
• 54:01
  Speaker 1: Coast versus West Coast. Who wraps better? They're all wrapped
• 54:06
  Speaker 1: it up inside a black hole. All right, Well, it
• 54:09
  Speaker 1: sounds like maybe stay tuned. It seems like there's some
• 54:12
  Speaker 1: interesting progress that's been made, but not everyone is convinced
• 54:16
  Speaker 1: about this new approach. That's right, and my personal hope
• 54:19
  Speaker 1: is that we do eventually get to do experiments near
• 54:21
  Speaker 1: black hole. All this, the theoretical calculation is fun and
• 54:24
  Speaker 1: it tells us what question is to ask, but we
• 54:27
  Speaker 1: never really know the answer until we actually get to
• 54:29
  Speaker 1: go do experiments near a black hole or maybe even
• 54:32
  Speaker 1: in a black hole. Until then, we just have to
• 54:35
  Speaker 1: smell the banana in the air and remember it and
• 54:39
  Speaker 1: remember and remember both our dearly departed lunch. All right, well,
• 54:44
  Speaker 1: we hope you enjoyed that. Thanks for joining us, see
• 54:48
  Speaker 1: you next time. Thanks for listening, and remember that Daniel
• 54:58
  Speaker 1: and Jorge explained. The unit Verse is a production of
• 55:01
  Speaker 1: I Heart Radio or more podcast from my heart Radio.
• 55:04
  Speaker 1: Visit the I Heart Radio Apple Apple Podcasts, or wherever
• 55:08
  Speaker 1: you listen to your favorite shows. H