WEBVTT - Staring into a Black Hole 0:00:15.356 --> 0:00:23.236 Pushkin from Pushkin Industries. This is Deep Background, the show 0:00:23.316 --> 0:00:26.276 where we explored the stories behind the stories in the news. 0:00:26.716 --> 0:00:33.476 I'm Noah Feldman. The world has recently been gripped by 0:00:33.556 --> 0:00:39.716 the extraordinary and extraordinarily beautiful image of a black hole, 0:00:40.276 --> 0:00:44.676 a thing which we know allows no information or light 0:00:44.756 --> 0:00:47.796 to escape, and of which we therefore, strictly speaking, shouldn't 0:00:47.796 --> 0:00:51.036 have an image at all to make sense of this. 0:00:51.516 --> 0:00:54.116 At the level of logic, at the level of physics, 0:00:54.156 --> 0:00:57.116 and at the level of deeper meaning, we're thrilled to 0:00:57.156 --> 0:01:00.836 have with us today. Andy Strominger one of the leading 0:01:00.876 --> 0:01:04.836 theoretical physicists in the world who's made fundamental contributions to 0:01:04.916 --> 0:01:08.396 quantum gravity theory, to string theory, and has also worked 0:01:08.436 --> 0:01:11.396 extensively on black holes. Don't take my word for it 0:01:11.396 --> 0:01:13.156 that and he's the right person to talk to. He's 0:01:13.156 --> 0:01:15.396 one of every prize there is to win in the 0:01:15.436 --> 0:01:19.756 space of theoretical physics. And Andy is also a director 0:01:19.756 --> 0:01:22.156 of the Center for Fundamental Laws of Nature at Harvard. 0:01:22.476 --> 0:01:24.156 On top of that, he's also one of the co 0:01:24.276 --> 0:01:28.156 directors of the black Hole Initiative here at Harvard University 0:01:28.156 --> 0:01:30.556 where I'm speaking to Andy today. Andy, thank you so 0:01:30.676 --> 0:01:34.636 much for coming and joining great to be here. Ah. So, Andy, 0:01:34.756 --> 0:01:37.996 let's just start with the image, which is a great 0:01:38.116 --> 0:01:43.156 headline grabber and something that is extraordinarily beautiful, but which 0:01:43.196 --> 0:01:47.716 strictly speaking, isn't a classic photographic image, whatever the world 0:01:47.756 --> 0:01:50.996 may imagine. So say a word, if you will, about 0:01:51.116 --> 0:01:54.076 what we are seeing, what it is, and then from 0:01:54.076 --> 0:01:57.796 there we can move on to what it tells us. Okay, well, 0:01:58.916 --> 0:02:01.676 I'd like to back up a little bit. It was 0:02:01.716 --> 0:02:07.196 a hundred years ago that Einstein predicted with his equations 0:02:07.236 --> 0:02:10.836 that there would be black holes, and people have been 0:02:10.916 --> 0:02:13.996 arguing about them for most of the time, not believing 0:02:14.036 --> 0:02:18.276 that they exist. Einstein wrote a paper nineteen thirty eight 0:02:18.316 --> 0:02:21.956 saying black holes don't exist. Most people thought they didn't 0:02:21.996 --> 0:02:27.956 exist until probably the seventies. And how they behave, what's 0:02:28.036 --> 0:02:34.596 inside them, why they're there, has been a central debate 0:02:34.916 --> 0:02:38.276 in physics for the last one hundred years. I have 0:02:38.436 --> 0:02:43.916 spent the majority of my scientific career thinking about them, 0:02:43.956 --> 0:02:48.116 trying to understand them, along with hundreds of other people, 0:02:48.756 --> 0:02:52.596 and then all of a sudden to see it, to 0:02:52.716 --> 0:02:56.556 see a picture of it, like Wow, that thing is real, 0:02:57.396 --> 0:03:00.956 it's really it's really it's not. We're not the only 0:03:00.956 --> 0:03:03.476 ones who have that. You could be the deepest specialist 0:03:03.516 --> 0:03:06.476 and you're moved by it. I promise you that we 0:03:06.516 --> 0:03:10.476 have a bunch bore. It rocked our worlds to like 0:03:10.996 --> 0:03:13.836 see this thing that we've been talking about our whole lives. 0:03:13.836 --> 0:03:16.156 So there it is, you know, even though you knew 0:03:16.156 --> 0:03:18.436 it was there. We knew it was there. But there 0:03:18.516 --> 0:03:22.636 is a big difference between knowing something's there and seeing it. 0:03:23.076 --> 0:03:26.156 You know, maybe there was still that tidy bagging about 0:03:26.436 --> 0:03:30.676 I don't know, but it really is great to see it. 0:03:30.676 --> 0:03:32.876 It's a great thing actually to hear that from a physicist, 0:03:32.916 --> 0:03:36.796 because when non physicists like me, mere lay people, we 0:03:37.076 --> 0:03:39.356 instinctively have the feeling if we don't see something, maybe 0:03:39.356 --> 0:03:41.556 it's not there. And then the physicists tell us it's 0:03:41.596 --> 0:03:45.156 all equations, it's all logic, there are experiments that validate 0:03:45.196 --> 0:03:47.476 these things. Take it on faith, you know, like you'll 0:03:47.476 --> 0:03:49.916 never fully understand those things, but we know. And so 0:03:49.996 --> 0:03:52.356 to hear that you too, or even you like to 0:03:52.396 --> 0:03:54.116 actually see stuff as a kind of I don't know, 0:03:54.156 --> 0:03:57.196 there's like some epistemological relief to me. And hearing that, yeah, yeah, 0:03:57.836 --> 0:03:59.836 so what is it that we are in fact seeing 0:03:59.996 --> 0:04:04.396 a black hole, by definition, is a region of space 0:04:04.436 --> 0:04:07.836 and time from which no light escapes. So we're not 0:04:07.916 --> 0:04:10.996 seeing light from the black hole. What we're really seeing 0:04:11.596 --> 0:04:17.196 is light emitted by gases swirling around the black hole, 0:04:17.636 --> 0:04:20.556 things that we don't understand very well. And we're seeing 0:04:20.596 --> 0:04:23.996 the shadow of the black hole. So that dark spot 0:04:24.356 --> 0:04:26.756 in the middle of that picture, the absence in the 0:04:26.756 --> 0:04:28.436 middle of the breast, the absence in the middle of 0:04:28.436 --> 0:04:31.356 the picture is where the black hole is. One of 0:04:31.356 --> 0:04:33.396 the ways that was central too, or the main thing 0:04:33.396 --> 0:04:35.876 that was central to making this telescope able to see 0:04:35.916 --> 0:04:38.836 something so extraordinarily far away, was to turn the whole 0:04:38.836 --> 0:04:42.196 Earth into a telescope. How does that work? We get 0:04:42.236 --> 0:04:46.476 to the size of the Earth because we take about 0:04:46.516 --> 0:04:50.076 eight different telescopes located at different points around the Earth 0:04:50.556 --> 0:04:54.356 and we synchronize them and so it's of course not 0:04:54.436 --> 0:04:58.996 a complete lens covering the entire Earth, but it's still 0:04:59.956 --> 0:05:02.676 gives you a lot of resolving power if you can 0:05:02.756 --> 0:05:06.996 just grab the light at those separate points. And as 0:05:06.996 --> 0:05:09.516 an accomplishment, the creation of the image with all of 0:05:09.556 --> 0:05:17.116 its coolness is scientifically significant. Why for several reasons. First 0:05:17.116 --> 0:05:20.516 of all, it is in and of itself a spectacular 0:05:21.156 --> 0:05:25.916 technical accomplishment, one that would not have been possible ten 0:05:25.996 --> 0:05:32.276 years ago. It required many things. It required amazing improvements 0:05:32.276 --> 0:05:37.436 in the accuracy of atomic clocks, um, it required uh, 0:05:38.036 --> 0:05:43.516 bigger hard drives, bigger data processing capabilities, it recovered. I 0:05:43.516 --> 0:05:45.396 read at one point that the data was so much 0:05:45.396 --> 0:05:47.476 that it actually had to be flown from one place. Yeah, 0:05:47.476 --> 0:05:51.676 because the Internet couldn't accommodated. Right at Sheep himself, I 0:05:51.716 --> 0:05:56.116 saw lugging around these you know, discs with the you know, 0:05:56.156 --> 0:05:59.836 he would go down to Mexico, go up to the 0:05:59.836 --> 0:06:03.276 top of the mountain and lug lug it back. Of course, 0:06:03.276 --> 0:06:06.356 the whole team was working on it. But Shep is 0:06:06.396 --> 0:06:10.596 the director of is the direct and your your co 0:06:10.716 --> 0:06:14.156 director at the black the director of this event Horizon 0:06:14.236 --> 0:06:17.916 project at a great great scientist and uh, and the 0:06:17.996 --> 0:06:20.916 algorithm has also gotten some attention and deserves some attention. 0:06:20.996 --> 0:06:26.356 I take it produced by Katie Bowman, a recent post doc. Right, Yes, 0:06:26.476 --> 0:06:29.116 there were of course, the whole there's there's a big 0:06:29.236 --> 0:06:34.156 team of one hundred to two hundred people, and you know, 0:06:34.196 --> 0:06:37.716 all this kind of big science is done in a 0:06:38.236 --> 0:06:40.436 big teams and big teams now and it's it's the 0:06:40.476 --> 0:06:44.076 only way it could can be done. But number one 0:06:44.076 --> 0:06:47.916 of the big technical accomplishment. Number Two, there is the 0:06:47.956 --> 0:06:53.116 importance of having seen these objects you know, that should 0:06:53.236 --> 0:06:58.436 be shouldn't be underestimated. Number three, it's only the beginning. Um. 0:06:58.476 --> 0:07:03.516 One of the things that struck me when I saw 0:07:03.556 --> 0:07:08.316 the papers was, which I was not privy too before 0:07:08.916 --> 0:07:15.076 the the general release, was how little actual observing time 0:07:15.156 --> 0:07:19.036 they had when I first met Chapter ten fifteen years ago. 0:07:19.156 --> 0:07:21.196 This project was you know, it was it was a 0:07:21.276 --> 0:07:24.356 dark horse. It was it was not, you know, the 0:07:24.876 --> 0:07:30.756 center of astronomical efforts. Um. And it was a funny idea, 0:07:31.036 --> 0:07:33.396 but one that the more you thought about it, the 0:07:33.436 --> 0:07:35.956 more since it made Why was it Why was that 0:07:36.036 --> 0:07:39.116 just panenthetically? Why why wasn't it at the centerpiece of 0:07:39.316 --> 0:07:41.436 as you say, black hole so crucial, so important and 0:07:41.916 --> 0:07:43.796 seeing it would be a big deal, you know, because 0:07:43.836 --> 0:07:46.716 it wasn't. There many ways it could have failed, right, 0:07:47.116 --> 0:07:51.676 They had to increase their observational precision by many orders 0:07:51.716 --> 0:07:55.876 of magnitude over whatever what anybody had ever seen. What 0:07:55.916 --> 0:08:00.316 they did. It's like standing in Boston and reading the 0:08:00.436 --> 0:08:03.836 data on a quarter in Los Angeles. That is, that 0:08:04.036 --> 0:08:07.596 is the precision that they had to have to image 0:08:07.716 --> 0:08:10.236 this black hole. The general public tends to forget, I 0:08:10.236 --> 0:08:12.716 tend to forget that the funding of scientific projects is 0:08:12.756 --> 0:08:14.556 always a kind of a bet or a gamble. It's 0:08:14.556 --> 0:08:17.236 a beat, and when the odds of the success are 0:08:17.236 --> 0:08:20.716 relatively low, the funders are skeptical about putting too much 0:08:20.716 --> 0:08:24.076 money on that gamble. When people thought about it ten 0:08:24.116 --> 0:08:25.756 or fifteen years ago, did they think, well, if we 0:08:25.796 --> 0:08:28.396 get enough computing power, this is one of the things 0:08:28.436 --> 0:08:31.036 will fix. And it's a question of whether we'll ever 0:08:31.076 --> 0:08:33.276 get enough computing power, or was it rather a question 0:08:33.316 --> 0:08:36.436 of other aspects of the technical difficulty of doing it. 0:08:36.836 --> 0:08:39.276 He wasn't dismissed, and the thing was funded in it 0:08:39.636 --> 0:08:42.636 and it did happen, but it was not obvious. It 0:08:42.676 --> 0:08:45.996 was not obvious. You know, the Earth is just barely 0:08:46.036 --> 0:08:49.636 big enough to image this thing. It's also very important 0:08:49.716 --> 0:08:55.236 that the wavelength that they could access with this large 0:08:55.796 --> 0:08:59.676 collator array is one in which there isn't a lot 0:08:59.756 --> 0:09:03.756 of absorption between us and the black hole. You know 0:09:03.796 --> 0:09:06.756 that there isn't a lot of dust that blocks the 0:09:06.836 --> 0:09:10.156 light at that that wavelength. Right, So there were some 0:09:10.236 --> 0:09:14.476 coincidence that you know, Luck smiled on the project. It 0:09:14.596 --> 0:09:17.596 might not have been possible. I don't I doubt if 0:09:17.636 --> 0:09:21.276 you get cheppy, you could ask him, but I doubt 0:09:21.316 --> 0:09:25.316 he would have been certain you ten fifteen years go 0:09:25.476 --> 0:09:27.916 that it would work. But I was going on to say, 0:09:28.556 --> 0:09:31.556 they didn't get all that much observing time. Now clearly 0:09:31.596 --> 0:09:36.956 they'll get more, right, there will be better resolution, more 0:09:36.996 --> 0:09:41.836 observing time, they'll set one up out in space. So 0:09:42.276 --> 0:09:44.916 there we are entering an era. So this is the 0:09:44.956 --> 0:09:49.956 opening of that era of precision black hole astronomy. So 0:09:50.036 --> 0:09:53.236 let's talk about now what we can see and what 0:09:53.276 --> 0:09:56.676 we will see when we get more time, more observations, 0:09:56.716 --> 0:09:58.476 and the emergence of what you described as a new 0:09:58.596 --> 0:10:02.276 a new science really of precision black hole astronomy. You 0:10:02.356 --> 0:10:06.516 with some collaborators have been actually making predictions the way 0:10:06.556 --> 0:10:10.156 theoretical physicists like to do. You know, a theoretical physicist 0:10:10.596 --> 0:10:13.916 makes predictions and sometimes they can be tested in his 0:10:14.036 --> 0:10:17.156 or her lifetime. Sometimes it takes generations. In this instance, 0:10:17.156 --> 0:10:20.276 you've made a series of observational predictions the things that 0:10:20.316 --> 0:10:23.916 you expect can be picked up, and now that will 0:10:23.916 --> 0:10:26.556 turn to whether they will in fact be be picked up, 0:10:26.556 --> 0:10:29.716 which is dramatic and exciting. What kinds of predictions have 0:10:29.836 --> 0:10:33.156 you already been making and when can we expect to 0:10:33.196 --> 0:10:39.396 see results. I've been working with Alex Sasa, Delilah Gates, 0:10:39.396 --> 0:10:45.556 and Dan Coppetts, and we are very interested in what 0:10:45.716 --> 0:10:50.596 happens very near the horizon of of the black hole, 0:10:50.716 --> 0:10:54.636 right at the edge of that inner shadow, and remind people, 0:10:54.756 --> 0:10:58.756 just because it's never bad, to redefine it the event horizon. Yeah. 0:10:58.796 --> 0:11:05.156 So the event horizon is the boundary of the region 0:11:05.236 --> 0:11:10.356 of space time from which light rays connects escape. So 0:11:10.436 --> 0:11:14.156 in practical terms, it's the edge of that you're inside 0:11:14.156 --> 0:11:16.276 the event horizon, you're in the black holiness of the 0:11:16.316 --> 0:11:19.156 black hole. Yeah. Once you go inside the event horizon, 0:11:19.196 --> 0:11:22.996 you can never come out, and so your predictions relate 0:11:23.036 --> 0:11:26.076 to what's happening at that edge, right. And one of 0:11:26.076 --> 0:11:30.716 the things that we are very interesting in is that 0:11:31.996 --> 0:11:37.516 black holes can spin around like a top and it's 0:11:37.556 --> 0:11:41.316 believed that the M eighty seven, the black hole that 0:11:41.356 --> 0:11:45.996 we've just seen, is spinning at light speed or very 0:11:46.076 --> 0:11:49.756 near light speed. So there has been claims of this 0:11:49.916 --> 0:11:54.876 from other kinds of measurements in the literature, and a 0:11:54.956 --> 0:12:00.836 black hole which spins at light speed does some incredibly 0:12:00.916 --> 0:12:04.196 peculiar things. Is you get near the edge of the 0:12:04.276 --> 0:12:08.796 black hole, a long sort of funnel or wormhole forms. 0:12:08.796 --> 0:12:11.716 It's kind of like a tornado with a long spout. 0:12:12.796 --> 0:12:18.036 And as the black hole spins faster and faster, that's spout. 0:12:18.916 --> 0:12:21.876 It sounds like I'm talking about sub sides fiction stuff. 0:12:22.276 --> 0:12:24.636 But everything with respected black holes though, so go on 0:12:25.276 --> 0:12:27.436 sounds like I'm talking about sizes fiction stuff. But we 0:12:28.036 --> 0:12:32.396 maybe seeing this kind of black hole. Now the spout 0:12:32.556 --> 0:12:35.516 or the wormhole that goes to the horizon, the black 0:12:35.556 --> 0:12:42.356 hole actually becomes an infinitely long tube protruding out of 0:12:42.436 --> 0:12:46.556 the out of space doot, and that will lead to 0:12:46.956 --> 0:12:48.756 about to ask you where where the wormhole leads. But 0:12:48.796 --> 0:12:51.836 if it's infinitely long, the answer is, yeah, it leads 0:12:51.836 --> 0:12:56.076 to infinity. It goes, it leads to infinity. But before 0:12:56.116 --> 0:12:59.556 it gets infinitely long where the wormhole leads it goes 0:12:59.596 --> 0:13:02.836 into the rise of black hole, and once it crosses there, 0:13:03.276 --> 0:13:06.596 we don't know. We don't know what's inside a black hole. 0:13:06.676 --> 0:13:08.956 So the part of the wormhole is in the very 0:13:09.196 --> 0:13:11.756 edge of the wormhole is at the event horizon, right 0:13:11.876 --> 0:13:14.716 as it were, and then it extends infinitely away from 0:13:14.756 --> 0:13:18.476 the black hole and connects on to the space time 0:13:18.556 --> 0:13:22.396 that you and I live in, and that so we're 0:13:22.476 --> 0:13:25.796 seeing into what does sound like science fiction. It does 0:13:25.836 --> 0:13:28.196 sound like science fiction, but we're seeing it, you know, 0:13:28.836 --> 0:13:31.556 And how would that be seen? I mean, what would 0:13:31.556 --> 0:13:34.556 that as it were look like? We in our paper 0:13:35.476 --> 0:13:43.996 gave some very specific predictions about what the polarization of 0:13:44.036 --> 0:13:47.476 the light coming out will be. It's known that it's polarized. 0:13:48.556 --> 0:13:50.476 Not that's coming from the black hole, but the lights, sorry, 0:13:50.476 --> 0:13:53.076 the light and the halo. Yes, it's known that it's 0:13:53.196 --> 0:13:58.396 polar polarized, but the distribution hasn't been extracted from the 0:13:58.476 --> 0:14:01.236 data yet. I think they've already seen it. They have 0:14:01.396 --> 0:14:05.276 these mountains of hard drives the data they need to process, 0:14:06.076 --> 0:14:11.036 and they haven't extracted from that what the polarization is. 0:14:11.836 --> 0:14:15.596 Luck will have to shine on us for Are there 0:14:15.676 --> 0:14:19.596 measurements to be sufficient to prove what you've predicted? Yeah? Right, 0:14:19.956 --> 0:14:23.596 because they weren't there looking for what you predicted. Well, 0:14:23.636 --> 0:14:28.316 that's right, and also might not be this round might 0:14:28.396 --> 0:14:32.076 not be a precise enough measurement for our prediction to 0:14:32.196 --> 0:14:38.196 be verified or not. But I'd stress that our prediction 0:14:38.956 --> 0:14:42.636 is a prediction of the Einstein equation. It's just the 0:14:42.716 --> 0:14:48.596 Einstein equation in a very unusual circumstance, not like the 0:14:48.596 --> 0:14:52.276 predictions that Einstein made, where the effects of general relativity 0:14:52.396 --> 0:14:55.356 on the bending of light or in the Solar system 0:14:55.596 --> 0:14:59.556 they were small effects. Yes here, it's huge effect. Here 0:14:59.556 --> 0:15:04.556 it changes dramatically the nature of space and time, everything 0:15:04.556 --> 0:15:07.356 that we really have to to somebody even reimagine what 0:15:07.436 --> 0:15:09.996 we are, what we mean in ordinary language term. Yeah. 0:15:10.556 --> 0:15:14.636 So we think that if you were to go in 0:15:14.676 --> 0:15:17.756 a spaceship to near the horizon of M eighty seven, 0:15:18.356 --> 0:15:22.956 you would be forced to whirl around it. You couldn't 0:15:22.996 --> 0:15:25.516 just approach it straight on. There would be a force 0:15:25.636 --> 0:15:28.036 by the warping of space time that would drag you 0:15:28.116 --> 0:15:32.756 around like a tornado and pull you down this down 0:15:32.796 --> 0:15:36.076 the drain into the down drain at the speed of 0:15:36.156 --> 0:15:40.556 light through the wormhole. Yeah, bow the wormhole to the Yeah, 0:15:40.796 --> 0:15:42.636 and it would grab you well before you got to 0:15:42.636 --> 0:15:45.916 the event horizon. So, in practical terms, though it's outside 0:15:45.916 --> 0:15:48.436 the event horizon, you're descent into the black hole would 0:15:48.436 --> 0:15:50.956 begin a lot sooner than it. Otherwise it would be 0:15:51.876 --> 0:15:53.996 if it were really spitting all the way at the 0:15:54.036 --> 0:15:56.596 speed of light, it would grab you when you were 0:15:56.756 --> 0:16:00.156 infinitely far away from the event horizon, but suck you 0:16:00.276 --> 0:16:04.356 there in a finite amount of time by pulling you 0:16:04.436 --> 0:16:07.556 up to the speed of light. But when you say 0:16:07.636 --> 0:16:09.116 we grab you when so I'm just trying to get 0:16:09.156 --> 0:16:11.236 my mind around this and not so much succeeding when 0:16:11.276 --> 0:16:14.596 you say would grab you the reason you're infinitely far 0:16:14.636 --> 0:16:17.476 away is that sounds as though, well, we're infinitely we're 0:16:17.476 --> 0:16:20.036 at some distance less than infinitely far away from M 0:16:20.116 --> 0:16:21.876 eighty seven right now. Why doesn't it grab up? Oh, 0:16:21.916 --> 0:16:25.636 we don't know that, because we're not infinitely far away 0:16:26.396 --> 0:16:30.156 from the edge of the wormhole, and the wormhole could 0:16:30.196 --> 0:16:33.476 be infinitely long. I don't think it is. You'd have 0:16:33.516 --> 0:16:35.516 to be going absolutely at the speed of light for 0:16:35.556 --> 0:16:37.396 it to be infinitely long. But it could be very 0:16:37.476 --> 0:16:40.876 very long, and so we could be much farther away 0:16:40.916 --> 0:16:44.356 than it seems. I mean, the rest of the universe exists. 0:16:44.716 --> 0:16:47.356 The rest of the universe is not presently I take 0:16:47.396 --> 0:16:53.276 it currently captured by the wormhole right and spinning at 0:16:53.276 --> 0:16:56.196 some very rapid speed around the black hole, and on 0:16:56.276 --> 0:16:58.756 the way to the event horizon, we're not headed all 0:16:58.836 --> 0:17:01.436 headed that way, I take it right. So my question 0:17:01.516 --> 0:17:07.036 is why, Well, because we're far away week, but when 0:17:07.076 --> 0:17:10.676 you get to some critical point instance, all of a 0:17:10.716 --> 0:17:17.316 sudden it's a spinning black hole is surrounded by a 0:17:17.476 --> 0:17:21.716 science fiction region which was discovered in the sixties called 0:17:21.716 --> 0:17:26.396 the ergosphere. And life inside the ergosphere is very different 0:17:26.436 --> 0:17:30.276 than life in this room, and existence rather than life, 0:17:30.276 --> 0:17:34.476 because nothing's living once you get into the ergosphere. Anyone 0:17:34.516 --> 0:17:37.836 who enters the ergosphere, which is still outside the black holes, 0:17:38.636 --> 0:17:42.876 you you are forced to spin around in the in 0:17:42.916 --> 0:17:48.116 the tornado vortex outside the black hole, and the wormhole 0:17:48.196 --> 0:17:51.316 is a big extension of that. The wormhole is the 0:17:51.676 --> 0:17:54.276 is the vortex going Yeah, it is the vortex going 0:17:54.316 --> 0:17:57.236 down to the black hole. So we what we know 0:17:57.396 --> 0:18:00.036 really is our distance from the mouth of the wormhole, 0:18:00.396 --> 0:18:04.916 not how long the wormhole is. Now nobody thinks it's 0:18:04.916 --> 0:18:08.796 infinitely long, but it could be long enough to be 0:18:08.836 --> 0:18:13.956 in testing and long enough to make a signal. And 0:18:14.156 --> 0:18:17.956 how how will the observation of the polarization of the 0:18:18.076 --> 0:18:21.436 light that presently is visible at the edge of the 0:18:21.436 --> 0:18:24.556 black hole get you to some better understanding of the 0:18:25.076 --> 0:18:28.516 of the wormhole. Well, the worm it will verify the 0:18:28.556 --> 0:18:32.436 existence of of the wormhole, I say. And the polarization 0:18:32.556 --> 0:18:34.996 is not the only thing um. There are other things 0:18:34.996 --> 0:18:39.676 that you might try to to to measure. Now I 0:18:39.796 --> 0:18:44.156 stress it there. We're just one of and not even 0:18:44.196 --> 0:18:47.556 the most important, what of many groups who are in 0:18:47.596 --> 0:18:51.076 the vent Horizon telescope themselves are making predictions. Of course, 0:18:51.076 --> 0:18:54.876 they had to compare their their theory to the theoretical 0:18:54.876 --> 0:18:59.396 predictions to their observation to get their estimate that they 0:18:59.436 --> 0:19:03.836 published of the mass. We are especially interested in some 0:19:03.916 --> 0:19:09.076 of these novel aspects because first of all, because they're 0:19:09.316 --> 0:19:12.436 weird and interesting and they're there and we're seeing them, 0:19:12.476 --> 0:19:17.916 and also because they tie in with ideas about the 0:19:17.996 --> 0:19:21.236 quantum structure of black holes and what's inside a black 0:19:21.276 --> 0:19:24.396 hole in a very intricate way. And that question of 0:19:24.396 --> 0:19:29.916 what's inside is hugely controversial and fascinating. So the question 0:19:29.956 --> 0:19:33.956 of what's inside also philosophical, if I yeah, I venture 0:19:33.956 --> 0:19:37.756 to use that word. There are philosophical aspects to it, 0:19:38.636 --> 0:19:42.596 but there is a very sharp meaning to it because, 0:19:43.316 --> 0:19:48.556 as Stephen Hawking showed, if you wait long enough and 0:19:48.756 --> 0:19:52.796 even the you know, event Horizon team won't have this 0:19:52.956 --> 0:19:55.436 much patience. I'd be like a very very long time, 0:19:56.796 --> 0:20:05.876 the black hole will evaporate and what's inside using quantum 0:20:05.916 --> 0:20:10.556 effects will come out. And then the question is would 0:20:10.596 --> 0:20:12.476 the thing that came out, would what was inside to 0:20:12.516 --> 0:20:15.076 come out and have some information? And then there is 0:20:15.116 --> 0:20:18.836 an inside that we would ultimately see if we could 0:20:18.836 --> 0:20:24.436 wait long enough, which I think, yeah, more than billions 0:20:24.676 --> 0:20:28.116 moves it from philosophy to physics because there would because 0:20:28.116 --> 0:20:32.276 it's not an unanswerable question. Well, it's a question people 0:20:32.276 --> 0:20:34.916 could argue about. That's a separate, interesting question. What makes 0:20:34.916 --> 0:20:37.156 something a physics question as opposed to philosopher ques I 0:20:37.236 --> 0:20:40.516 was using a shorthand of imagining that physicists only like 0:20:40.636 --> 0:20:44.436 questions that, in principle could be answered. It's a question 0:20:44.476 --> 0:20:47.516 which can be answered with a goadoncan experiment when you're 0:20:47.516 --> 0:20:49.596 do in your mind? Yes, I thought, you can't get 0:20:49.596 --> 0:20:52.836 the funding to do it? Okay, right, So some people 0:20:52.836 --> 0:20:55.556 would say infinite time, Well, you don't have infinite time. 0:20:55.876 --> 0:20:59.516 Some people would say that physics is the study of 0:20:59.636 --> 0:21:03.156 questions you could answer with real experiments that could be funded. 0:21:04.476 --> 0:21:07.396 That's a pretty cramp though, view if it wouldn't cover 0:21:07.436 --> 0:21:10.356 a lot of your your earlier work, wouldn't cover wouldn't 0:21:10.356 --> 0:21:11.956 cover a lot of my work, right, And I think, 0:21:12.116 --> 0:21:13.676 to be fair, I don't think that's what most non 0:21:13.716 --> 0:21:16.236 physicists think. I think it's that would be a very 0:21:16.356 --> 0:21:19.596 hard nosed, predictive, pragmatist view, and it's not physics if 0:21:19.596 --> 0:21:21.436 I can't test it, you know, and get funding to 0:21:21.436 --> 0:21:24.076 test it. Yea. The laws of nature presumably should be 0:21:24.636 --> 0:21:27.756 resistant to being cabined by what we can fund. But 0:21:27.876 --> 0:21:31.156 what's exciting to me here is that this observation is 0:21:31.236 --> 0:21:36.116 touching the edge, possibly touching the edge of the things 0:21:36.156 --> 0:21:41.276 that bearing on the issues of people that people think 0:21:41.316 --> 0:21:44.196 about who want to understand what's really inside a black hole. 0:21:44.276 --> 0:21:48.116 So you mentioned your friend Stephen Hawking, also your collaborator 0:21:48.916 --> 0:21:51.116 who died not so long ago and with whom you 0:21:51.156 --> 0:21:52.796 did a lot of work over the years, but most 0:21:52.836 --> 0:21:55.956 recently you had been working on some pretty major projects 0:21:55.996 --> 0:21:58.556 with him, also connected to black holes. Yeah, tell us 0:21:58.556 --> 0:22:02.876 a little bit about that. Yes, Stephen, in his most 0:22:03.316 --> 0:22:08.876 famous work in the Seven Daies, showed that with an 0:22:09.156 --> 0:22:13.156 argument that is so simple and elegant that it has 0:22:13.236 --> 0:22:19.676 never been seriously questioned that when you include quantum effects, 0:22:20.596 --> 0:22:26.796 black holes are not completely black. That quantum effects allow 0:22:26.876 --> 0:22:31.156 a sort of the uncertainty principle about where the horizon 0:22:31.196 --> 0:22:35.956 of the black hole is allows a small amount of 0:22:36.036 --> 0:22:40.196 light and matter to slowly trickle out of the of 0:22:40.196 --> 0:22:44.276 a black hole a very slow rate. So those are 0:22:44.276 --> 0:22:46.796 big things, and let me try a very very lay 0:22:46.836 --> 0:22:51.316 person's attempt to make sense of that. If we imagined 0:22:52.196 --> 0:22:56.756 determinative locations and laws of physics, then nothing escapes the 0:22:56.796 --> 0:22:59.116 black hole. That's what makes it a black hole. But 0:23:00.036 --> 0:23:03.756 one of the key points of quantum theory is it 0:23:03.916 --> 0:23:09.076 precisely you can't pin down the exact location of every 0:23:09.276 --> 0:23:12.836 quantum phenomenon. And since you can't pin it down exactly, 0:23:13.196 --> 0:23:16.676 that puts enough wiggle room, if you will, into the 0:23:16.796 --> 0:23:19.876 equation that there is some information in the black hole 0:23:19.916 --> 0:23:22.636 that might be capable of being discovered. How's that for 0:23:22.676 --> 0:23:25.796 a first order? That's right. So quantum mechanics says that 0:23:25.916 --> 0:23:31.396 the horizon and the black hole must fluctuate around a 0:23:31.436 --> 0:23:34.756 little bit, according must be slightly uncertain, and so that 0:23:36.316 --> 0:23:40.116 gives just enough wiggle room for a few quantum particles 0:23:40.156 --> 0:23:44.636 to escape from inside the black hole at a slow rate, 0:23:45.036 --> 0:23:49.596 so that you began with describing Hawking's famous nineteen seventies 0:23:49.916 --> 0:23:52.796 that was forty years ago, yep. And he gave an 0:23:52.876 --> 0:23:59.996 argument that the information about how the black hole was 0:24:00.116 --> 0:24:05.636 made would not escape, would not come out with this 0:24:05.796 --> 0:24:09.596 leak of energy and particles and so on. Things would 0:24:09.636 --> 0:24:11.916 come out, but not the information about how the black 0:24:11.916 --> 0:24:16.876 black hole came to be made. He claimed, the present 0:24:17.236 --> 0:24:21.876 does not determine the future and cannot, even in principle, 0:24:22.036 --> 0:24:25.716 be used to reconstruct the past. Bad news for historians, 0:24:26.356 --> 0:24:28.636 bad news for hystories for people who like free will 0:24:28.636 --> 0:24:33.396 in the future maybe, but bad news for physicists because 0:24:33.636 --> 0:24:37.196 it's equivalent to saying there aren't absolute laws of physics, 0:24:37.596 --> 0:24:40.996 because a law of physics is supposed to predict the 0:24:41.036 --> 0:24:44.436 future from the present. It was a very simple argument, 0:24:45.516 --> 0:24:49.716 and people didn't like the conclusion. It had been questioned 0:24:49.756 --> 0:24:54.436 in many different ways, but none of the ways in 0:24:54.476 --> 0:24:58.876 which it was questioned really stuck. So a few years 0:24:58.876 --> 0:25:05.636 ago I found, while investigating other problems in physics, I 0:25:05.796 --> 0:25:10.836 came across what seemed to be an error in the 0:25:10.876 --> 0:25:18.596 original flawed assumption in his original reasoning. Moreover, the nature 0:25:19.116 --> 0:25:24.556 of the flaw suggested a research program for understanding what 0:25:24.876 --> 0:25:32.916 really did happen. And I explained this to Stephen and 0:25:33.276 --> 0:25:36.196 he was very excited about it, and I just say, 0:25:36.276 --> 0:25:38.756 this is also it's a great model of what scientific 0:25:38.756 --> 0:25:43.156 collaboration can be and isn't always You find a flaw 0:25:43.276 --> 0:25:47.396 in an important claim by another famous physicist and you 0:25:47.476 --> 0:25:51.356 call him up and you say, hey, there's a problem, 0:25:51.516 --> 0:25:54.436 and that's collegial of you, and then he responds positively, 0:25:54.436 --> 0:25:56.236