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Become an Explorer and seek out unforgettable places 0:01:48.400 --> 0:01:51.840 while enjoying rewards everywhere you travel. Cards issued by JP 0:01:51.920 --> 0:01:55.920 Morgan Chase Bank NA Member FDIC subject to credit approval Offer, 0:01:56.000 --> 0:01:57.800 subject to change. Terms apply. 0:02:05.840 --> 0:02:09.280 Hey Danian, what do you think makes black holes so interesting? 0:02:09.760 --> 0:02:09.960 You know? 0:02:10.080 --> 0:02:13.840 I think the mystery, the finality of it, the weirdness 0:02:13.960 --> 0:02:14.200 of it. 0:02:14.320 --> 0:02:18.040 For sure, they're like a magnet for fascination. 0:02:19.919 --> 0:02:25.440 They absolutely are for curiosity, for investigation, for dedication. 0:02:25.960 --> 0:02:28.960 And it's not just physicists. Everyone seems to have questions 0:02:28.960 --> 0:02:29.760 about black holes. 0:02:29.880 --> 0:02:32.560 Yeah, they seem to be sort of mentally magnetic. 0:02:34.600 --> 0:02:37.880 So black holes attract matter and also questions. 0:02:39.639 --> 0:02:43.720 They definitely attract questions. They seem to repel understanding. 0:02:43.440 --> 0:02:44.960 Or they just repel physicists. 0:02:47.080 --> 0:02:49.480 I'm pretty sure they'd be happy to suck me right in. 0:02:50.000 --> 0:02:52.520 I don't think I want to go down that rabbit hole. 0:03:07.880 --> 0:03:08.040 Hi. 0:03:08.040 --> 0:03:10.720 I am Hora May Cartoons, an author of Oliver's Great 0:03:10.760 --> 0:03:11.480 Big Universe. 0:03:11.680 --> 0:03:14.399 Hi. I'm Daniel. I'm a particle physicist and a professor 0:03:14.720 --> 0:03:18.440 at UC Irvine, and I desperately want to know what's 0:03:18.520 --> 0:03:19.360 inside those. 0:03:19.200 --> 0:03:22.800 Black holes, if there's even an inside. Right do we 0:03:22.880 --> 0:03:24.519 know that they have an inside? 0:03:24.560 --> 0:03:28.320 We don't really know anything beyond the event horizon at all. 0:03:28.760 --> 0:03:31.200 In some sense, the interior of a black hole could 0:03:31.240 --> 0:03:32.800 be like another universe. 0:03:33.440 --> 0:03:36.600 Whoa like We could be living inside of a black 0:03:36.600 --> 0:03:38.240 hole right now? Is that possible? 0:03:40.200 --> 0:03:42.080 I think that gives me a mental black hole even 0:03:42.080 --> 0:03:42.680 thinking about it. 0:03:45.000 --> 0:03:47.640 Hi, suckered you write in, But anyways, welcome to our podcast, 0:03:47.720 --> 0:03:51.720 Daniel and Jorge Explain the Universe, a production of iHeartRadio. 0:03:51.360 --> 0:03:53.560 In which we try our best not to give you 0:03:53.600 --> 0:03:57.600 a headache while we contemplate the deepest secrets of the universe. 0:03:57.920 --> 0:04:00.600 We want to understand everything that's out there, from the 0:04:00.640 --> 0:04:04.720 tiniest little bits to the hugest swirling black holes and 0:04:04.800 --> 0:04:08.040 everything in between, because we think that it's possible somehow 0:04:08.080 --> 0:04:10.800 to make sense of it all, to understand it, to 0:04:10.880 --> 0:04:13.160 predict it, and to explain all of it to you. 0:04:13.440 --> 0:04:15.760 Yeah, that's right. We try to be the advil or 0:04:15.840 --> 0:04:18.320 tile and all to your understanding of the universe, not 0:04:18.360 --> 0:04:20.719 give you a headache about how amazing things are, but 0:04:20.839 --> 0:04:24.599 rather try to ease the pain of trying to wrap 0:04:24.640 --> 0:04:27.200 your mind around this amazing cost mooves we live in. 0:04:27.560 --> 0:04:32.200 I think it was as your prescription for physics. 0:04:32.680 --> 0:04:34.679 Well, everybody out there is going to need like another 0:04:34.720 --> 0:04:37.080 kind of health insurance now physics health insurance. 0:04:38.680 --> 0:04:42.400 The physicists have special health insurance for you know, headaches 0:04:42.480 --> 0:04:43.840 and mind bending. 0:04:44.160 --> 0:04:46.200 We're going to help you cover the cost of understanding 0:04:46.240 --> 0:04:50.560 the universe because while physics has made lots of progress 0:04:50.640 --> 0:04:53.159 in understanding the way the universe works, there are still 0:04:53.360 --> 0:04:57.080 huge gaps in our knowledge. In fact, we're pretty sure 0:04:57.120 --> 0:05:00.040 there's more that we don't understand than that we do, 0:05:00.680 --> 0:05:03.520 and a lot of those mysteries might have answers waiting 0:05:03.560 --> 0:05:06.680 for us beyond the curtain of the event horizon. 0:05:06.960 --> 0:05:10.039 Yeah, as we've talked about, we only know about five 0:05:10.080 --> 0:05:12.560 percent of the whole universe. The rest, the other ninety 0:05:12.560 --> 0:05:15.039 five percent is a complete mystery. And even within the 0:05:15.040 --> 0:05:17.039 five percent that we think we know, there are still 0:05:17.240 --> 0:05:21.320 huge holes in our understanding of how things work and 0:05:21.400 --> 0:05:23.400 what can happen out there in the universe. 0:05:23.480 --> 0:05:25.640 The best way to unravel some of the open mysteries 0:05:25.880 --> 0:05:29.120 is to embrace the unknown, is to dive into our 0:05:29.240 --> 0:05:32.719 ignorance and try to reveal something new about the universe. 0:05:33.200 --> 0:05:36.360 Often this happens at the extreme points of the universe, 0:05:36.720 --> 0:05:39.640 places where things are super duper hot, or super duper dense, 0:05:40.120 --> 0:05:43.960 or super duper crazy, because it's that those places that 0:05:44.040 --> 0:05:47.680 our understanding breaks down. That's one reason why black holes 0:05:47.720 --> 0:05:51.160 are so attractive to physicists, because they are where our 0:05:51.240 --> 0:05:53.120 current theories have to break. 0:05:53.680 --> 0:05:55.880 Yeah, it seems like there's no place in the universe 0:05:55.880 --> 0:05:59.400 that is more extreme or mysterious than a black hole. 0:05:59.640 --> 0:06:02.039 We have so many questions about that. Everyone has questions 0:06:02.040 --> 0:06:04.200 about it. It seems that it attracts not just mass 0:06:04.240 --> 0:06:06.080 and energy, but also curiosity. 0:06:06.839 --> 0:06:10.000 It does absolutely. I don't know if it sucks in curiosity, 0:06:10.080 --> 0:06:13.599 or it's radiating curiosity, or how the whole curiosity field works. 0:06:13.600 --> 0:06:17.200 Talking talking radiation of curiosity exactly. 0:06:17.480 --> 0:06:20.680 Maybe it's consuming anti curiosity while radiating. 0:06:20.279 --> 0:06:25.480 Curiosity anti curiosity. Oh, that's an interesting concept, but what 0:06:25.600 --> 0:06:25.920 is that? 0:06:26.240 --> 0:06:27.960 I don't know. That's what we're trying to generate on 0:06:28.000 --> 0:06:31.159 this podcast. We're trying to satisfy everybody's curiosity or are 0:06:31.200 --> 0:06:33.320 we just trying to stoke it. I'm not even sure anymore. 0:06:34.160 --> 0:06:38.120 Yeah, it sounds like you're trying to annihilate people curiosity. 0:06:39.279 --> 0:06:42.120 No, I guess we're trying to generate anti confusion particles. 0:06:42.400 --> 0:06:42.880 How about that? 0:06:42.920 --> 0:06:48.600 Oh, there you go, rock Ons, get a Tino's exactly, 0:06:49.000 --> 0:06:51.440 the AHA particles, that's what we're after. 0:06:52.520 --> 0:06:54.640 Yeah, I want to be one with the AHA field. 0:06:55.400 --> 0:06:58.159 But there are still very basic questions about how black 0:06:58.160 --> 0:07:00.479 holes work, what it means to be near black hole, 0:07:00.520 --> 0:07:02.960 what you would experience, what you might measure with your 0:07:03.000 --> 0:07:06.160 devices near a black hole. We've talked about the massive 0:07:06.160 --> 0:07:08.440 black holes, we talked about the charge of black holes, 0:07:08.440 --> 0:07:11.160 we talked about the spin of black holes. But there 0:07:11.200 --> 0:07:13.880 are still even more basic things we can think about 0:07:14.080 --> 0:07:15.360 when it comes to black holes. 0:07:15.560 --> 0:07:17.800 So today on the podcast, we'll be tackling the question 0:07:23.160 --> 0:07:27.000 do black holes have magnetic fields? 0:07:27.040 --> 0:07:27.120 Like? 0:07:27.200 --> 0:07:31.160 Are they attractive or repulsive? Do they have raised or not? 0:07:32.720 --> 0:07:35.400 Can you use black holes to find lost wedding rings 0:07:35.400 --> 0:07:38.000 on the beach? I knew there was a practical application 0:07:38.040 --> 0:07:39.120 of my research somewhere. 0:07:39.200 --> 0:07:41.960 Could you use it to detect your wedding ring on 0:07:42.240 --> 0:07:44.040 the beach when in it just swallow up the whole beach? 0:07:46.000 --> 0:07:47.600 Then you'd have a good excuse for why you lost 0:07:47.640 --> 0:07:50.800 your wedding ring there was a black hole on the beach. 0:07:51.600 --> 0:07:53.960 Yeah, and you would technically know where it is. It's 0:07:53.960 --> 0:07:56.760 inside the black hole. You just you know you can't 0:07:56.760 --> 0:07:58.000 get it ever. 0:07:58.200 --> 0:08:01.440 Yeah, exactly. No number of explaining on's is going to 0:08:01.440 --> 0:08:02.680 get you out of that jam. 0:08:02.840 --> 0:08:05.400 Yeah, but yeah, it's an interesting question. Do black holes 0:08:05.440 --> 0:08:08.160 have magnetic field? And I know we've did a whole 0:08:08.200 --> 0:08:12.120 episode on whether black holes have a charge, right, Yeah, 0:08:12.160 --> 0:08:14.520 and so this is different, this is more about the 0:08:15.080 --> 0:08:15.840 magnetic field. 0:08:16.080 --> 0:08:18.040 Yeah, we did one on charge, we did another one 0:08:18.120 --> 0:08:20.760 on spin. There's not that much stuff you can actually 0:08:20.840 --> 0:08:23.360 know about black holes, and we know so little, so 0:08:23.440 --> 0:08:25.360 I'm always excited to talk more about it. 0:08:25.480 --> 0:08:27.880 Then we do a whole episode on the hairiness of 0:08:27.920 --> 0:08:28.520 a black hole. 0:08:29.640 --> 0:08:33.800 That's true, their lack of hairiness actually their smooth shavenness. 0:08:34.679 --> 0:08:38.800 Yeah. Well, this is an interesting question, and so as usual, 0:08:38.880 --> 0:08:41.280 we were wondering how many people out there had thought 0:08:41.320 --> 0:08:44.960 about whether black holes have magnetic fields, and if they do, 0:08:45.240 --> 0:08:46.800 what do they look like or feel like. 0:08:47.679 --> 0:08:49.959 I think it's possible that they do. 0:08:50.240 --> 0:08:53.760 I think if I'm not too sure exactly after rationale 0:08:53.800 --> 0:08:57.120 it's but somehow I feel like it might be possible 0:08:57.120 --> 0:08:58.800 for black holes to have magnetic fields. 0:08:59.000 --> 0:09:02.160 I think they do if from the spiraling matter that's 0:09:02.200 --> 0:09:05.800 been consumed by the black hole. Whether or not they 0:09:05.800 --> 0:09:08.720 are magnetic in their core, whatever their core is, if 0:09:08.720 --> 0:09:10.520 you can have a call in a black hole, I 0:09:10.520 --> 0:09:12.520 don't know, but by virtue of the whole of the 0:09:12.520 --> 0:09:15.440 object that's wholy, yes. 0:09:15.960 --> 0:09:18.160 I do not believe so, only because I do not 0:09:18.200 --> 0:09:21.240 believe there are any charged particles within a black hole. However, 0:09:21.520 --> 0:09:23.800 since we do see jets coming from black holes at times, 0:09:23.840 --> 0:09:25.280 that could be totally wrong about that. 0:09:25.520 --> 0:09:28.400 I don't really know, but if I had to guess, 0:09:28.600 --> 0:09:30.840 I think they would like something to do with the 0:09:31.040 --> 0:09:36.559 hawking radiation being magnetized somehow, or so. 0:09:35.840 --> 0:09:38.760 The black hole itself beyond the event horizon. 0:09:38.760 --> 0:09:41.160 I don't think we can know that, but the area 0:09:41.240 --> 0:09:43.880 around the black hole where the Acresian disk is probably 0:09:43.880 --> 0:09:44.920 can have a magnetic field. 0:09:45.320 --> 0:09:49.240 Black Holes have mass, and they have spin, and I 0:09:49.280 --> 0:09:52.440 believe they have a charge. So if something has a charge, 0:09:52.480 --> 0:09:55.240 it should also have a magnetic field. Probably a little 0:09:55.280 --> 0:09:55.959 squirrely with. 0:09:56.000 --> 0:09:59.880 The amount of gravitational forces going on, but going with 0:09:59.880 --> 0:10:00.400 the yes. 0:10:01.200 --> 0:10:03.440 Yes, I'm pretty sure black holes have magnetic fields because 0:10:03.800 --> 0:10:06.679 whenever a particle let's charged enters it, the electric charge 0:10:06.720 --> 0:10:08.920 is conserved. So I guess a black hole would need 0:10:08.960 --> 0:10:10.880 to have that magnetic field that the particle had. 0:10:11.600 --> 0:10:13.600 I have no idea that. 0:10:13.720 --> 0:10:16.560 As a wild guest, I would say yes, they have 0:10:16.720 --> 0:10:19.560 probably vacuumed app some magnetic vibes along the way. 0:10:20.440 --> 0:10:23.520 Black holes do have magnetic fields. I'm pretty sure that 0:10:23.600 --> 0:10:27.120 the Beatles wrote a song about it. Magnetic field forever. 0:10:28.280 --> 0:10:30.640 If a black hole is churning around, does it create 0:10:30.679 --> 0:10:33.880 a magnetic field? Is there a north pole to a 0:10:33.880 --> 0:10:38.920 black hole? I wonder if magnetism can escape gravity or 0:10:39.000 --> 0:10:39.760 is immune to it. 0:10:40.360 --> 0:10:43.240 I think magnetize are neutron stars with a magnetic charge. 0:10:43.320 --> 0:10:46.120 I'm not sure about a black hole. Maybe if it's 0:10:46.160 --> 0:10:47.720 spinning and has an electric charge. 0:10:48.800 --> 0:10:50.760 I think that if a black hole a bunch of 0:10:51.400 --> 0:10:54.040 large stuff with a magnetic field, and the black hole 0:10:54.080 --> 0:10:57.439 would get a magnetic field. I'm gonna say yes, because 0:10:57.679 --> 0:11:00.560 there's one other three things that have that black present 0:11:00.640 --> 0:11:03.880 so that we can measure, but I forget one of them. 0:11:04.520 --> 0:11:07.400 So there are spin, there, mass, and electromagnetic force. So 0:11:07.440 --> 0:11:08.120 I'm gonna say yes. 0:11:08.600 --> 0:11:12.560 All right, interesting answers from a lot of magnetic people. 0:11:14.120 --> 0:11:15.800 Yeah, you could tell a lot of people had not 0:11:15.920 --> 0:11:18.800 thought about this question at all. They seem to sort 0:11:18.840 --> 0:11:20.240 of come up with their answers on the fly. 0:11:21.040 --> 0:11:23.040 Yeah, it's kind of a polarizing question. 0:11:25.080 --> 0:11:27.640 People either retracted or repelled by it. Yeah. 0:11:28.160 --> 0:11:30.240 Yeah, Well it seemed to attract definitely a lot of 0:11:30.240 --> 0:11:33.360 ideas about what's going on in the black hole, and 0:11:33.440 --> 0:11:36.480 so let's dive right into it. Daniel take us through 0:11:36.520 --> 0:11:39.880 the basics of black holes and how they relate to electromagnetism. 0:11:40.280 --> 0:11:43.720 So fundamentally, we don't really know what black holes are 0:11:43.760 --> 0:11:46.720 in our actual universe, like the physical things that are 0:11:46.720 --> 0:11:49.960 at the center of the galaxy, or they have really 0:11:50.000 --> 0:11:53.040 dense stuff orbiting them really closely. We're not really sure 0:11:53.080 --> 0:11:56.319 what those things are, but we do have a concept 0:11:56.360 --> 0:11:59.439 in our theory. General relativity predicts a kind of black 0:11:59.480 --> 0:12:02.520 hole that we know. Again, general relativity can't be right, 0:12:02.760 --> 0:12:05.920 so this theoretical object can't actually align with what's out 0:12:05.920 --> 0:12:07.760 there in the universe, but it gives us something to 0:12:07.800 --> 0:12:11.480 dig into, something that play with. And because general relativity 0:12:11.480 --> 0:12:14.720 tells us that gravity is not a force between objects 0:12:14.760 --> 0:12:17.960 the way Newton described it, but instead a curvature of 0:12:18.000 --> 0:12:20.960 space time, there's something weird that can happen when you 0:12:21.000 --> 0:12:25.200 get enough mass, enough energy density actually together in one place, 0:12:25.559 --> 0:12:28.080 which is that space can curve so much that the 0:12:28.120 --> 0:12:31.800 inside is essentially cut off from the outside. There's a 0:12:31.840 --> 0:12:34.840 place beyond which space is curved so that it only 0:12:34.880 --> 0:12:38.880 points towards the center of the black hole, meaning any 0:12:38.880 --> 0:12:42.040 object that falls past that event horizon will always end 0:12:42.120 --> 0:12:45.000 up at the center of the black hole. And so 0:12:45.080 --> 0:12:47.480 this is the basic concept of a black hole, sort 0:12:47.480 --> 0:12:51.840 of extreme space time curvature that generates this event horizon 0:12:52.200 --> 0:12:53.520 past which nothing can. 0:12:53.520 --> 0:12:55.800 Escape, right right, Because I feel like that's always. One 0:12:55.840 --> 0:12:58.120 of the carriats we have to point out is that 0:12:58.160 --> 0:13:00.640 the bending of space time, right, it's not just sort 0:13:00.640 --> 0:13:03.199 of space, it's also sort of like what happens in 0:13:03.240 --> 0:13:03.720 the future. 0:13:03.960 --> 0:13:07.800 There are definitely time related effects. Also, mass bends space 0:13:07.880 --> 0:13:11.000 and creates this event horizon, it also bends time. So 0:13:11.160 --> 0:13:14.000 you are near a black hole, for example, a distant observer, 0:13:14.120 --> 0:13:17.600 we'll see your clock go more slowly, and near black holes, 0:13:17.640 --> 0:13:20.319 space and time are very confusing, and in fact, the 0:13:20.320 --> 0:13:23.480 whole concept of space time is easier to understand in 0:13:23.520 --> 0:13:26.920 special relativity when you have flat space. In general relativity, 0:13:27.120 --> 0:13:29.680 which direction is space and which direction is time becomes 0:13:29.800 --> 0:13:33.040 very very confusing, and in some cases it's not even clear. 0:13:33.800 --> 0:13:37.800 And so, as you said, it's something that physics predicts 0:13:38.320 --> 0:13:40.560 is happening out there in the universe because we see 0:13:40.600 --> 0:13:42.600 around us and it seems like, you know, the Sun 0:13:42.679 --> 0:13:45.160 is bending space around and the Earth is bending space around, 0:13:45.160 --> 0:13:47.679 and we're bending space around us. But if you take 0:13:47.679 --> 0:13:50.319 it to an extreme, it predicts something called a black hole. 0:13:50.920 --> 0:13:53.320 Yeah, and a lot of people imagine a black hole 0:13:53.400 --> 0:13:56.880 in a sort of Newtonian way. They think, oh, gravity 0:13:56.960 --> 0:13:59.600 is so strong that you have to go faster than 0:13:59.600 --> 0:14:02.240 the speed of light in order to escape it. But 0:14:02.320 --> 0:14:04.880 it's not a question of forces, it's not a question 0:14:04.960 --> 0:14:08.040 of a velocity. It's not a Newtonian picture at all. 0:14:08.080 --> 0:14:10.840 It really tells you that the story of how gravity 0:14:10.880 --> 0:14:14.000 works is very, very different. That you're literally trapped inside 0:14:14.080 --> 0:14:17.640 this event horizon. No amount of velocity, no force can 0:14:17.679 --> 0:14:21.200 ever escape it because the shape of space itself has changed. 0:14:21.920 --> 0:14:24.560 And so if you imagine space is this like emptiness 0:14:24.600 --> 0:14:27.320 in which things float, then you need a new idea. 0:14:27.480 --> 0:14:29.640 General relativity tells us we could describe it as this 0:14:29.760 --> 0:14:33.080 sort of stuff with curvature to it, that we're moving 0:14:33.200 --> 0:14:36.640 through that curvature, and that curvature is not sitting inside 0:14:36.680 --> 0:14:39.320 some like deeper, larger space that you might be tempted 0:14:39.360 --> 0:14:42.160 to imagine. That's all there is, and we are trapped 0:14:42.160 --> 0:14:44.600 inside of it and there's nothing on the outside of 0:14:44.600 --> 0:14:45.520 it as far as we know. 0:14:46.280 --> 0:14:49.280 Right, right, and as usual, we also have to give 0:14:49.280 --> 0:14:52.960 the cavet that black holes are technically theoretical, right, Like 0:14:53.040 --> 0:14:55.520 we've seen things that sort of behave like black holes, 0:14:55.520 --> 0:14:58.000 but we haven't sort of been in front of one 0:14:58.400 --> 0:15:00.040 or touched it, right, that's right. 0:15:00.240 --> 0:15:03.360 And what we're describing is a prediction of general relativity, 0:15:03.720 --> 0:15:06.800 which we know to be very accurate in most circumstances, 0:15:07.120 --> 0:15:10.400 except we expect it to break down when things get 0:15:10.480 --> 0:15:14.520 very very intense and very very small. And so, for example, 0:15:14.560 --> 0:15:16.960 general relativity predicts that at the heart of one of 0:15:16.960 --> 0:15:20.360 these black holes is a singularity, a point of infinite density. 0:15:20.640 --> 0:15:23.240 This runaway gravity just goes on forever, and you get 0:15:23.280 --> 0:15:26.120 infinite curvature at the heart of the black hole. But 0:15:26.160 --> 0:15:28.800 we don't think that that's really happening because we know 0:15:28.880 --> 0:15:31.760 that that's in conflict with quantum mechanics. And so real 0:15:31.800 --> 0:15:33.960 black holes, if they exist out there in the universe, 0:15:34.240 --> 0:15:38.080 can't align perfectly with this theoretical description of a general 0:15:38.120 --> 0:15:40.920 relativity black hole. There has to be some quantum fuzziness 0:15:40.960 --> 0:15:43.320 to it, some other version of a black hole. And 0:15:43.600 --> 0:15:46.480 we talked recently on the podcast how quantum black holes 0:15:46.560 --> 0:15:50.560 probably radiate. They're not perfectly black due to Hawking radiation, 0:15:50.920 --> 0:15:52.600 and there must be other changes we need to make 0:15:52.640 --> 0:15:55.320 from this general relativity picture of a black hole to 0:15:55.440 --> 0:15:58.560 a realistic quantum gravity black hole that we don't even 0:15:58.600 --> 0:16:01.400 know how to describe. And you're right that the things 0:16:01.440 --> 0:16:03.520 we've seen out there in the universe, at the heart 0:16:03.560 --> 0:16:06.560 of our galaxy, etc. We're not even sure if they 0:16:06.600 --> 0:16:10.040 actually are black holes, because we've not technically observed an 0:16:10.040 --> 0:16:13.360 event horizon. All we've seen is that there are very 0:16:13.400 --> 0:16:17.680 dense objects, very massive, very small, very compact, and so 0:16:17.720 --> 0:16:20.360 we suspect that they are black holes, but they could 0:16:20.440 --> 0:16:24.040 be something else. These days, there are quantum gravity inspired 0:16:24.080 --> 0:16:28.200 ideas for other things that could fit the data. Fuzzballs 0:16:28.360 --> 0:16:31.680 or dark stars, etc. Yeah, all kinds of fun names. 0:16:31.880 --> 0:16:34.000 I wonder if we should maybe start calling black holes 0:16:34.040 --> 0:16:36.280 and not black holes then maybe or. 0:16:36.280 --> 0:16:38.920 Maybe just black holes with a question mark black holes 0:16:39.360 --> 0:16:43.320 really dark objects rdos. 0:16:44.080 --> 0:16:46.400 All right, So then a big concept in a black 0:16:46.440 --> 0:16:49.920 hole is this idea of an event horizon. Now is 0:16:50.000 --> 0:16:53.200 the idea of an event horizon also dependent on relativity 0:16:53.200 --> 0:16:57.280 and quantum mechanics playing nicely with each other, or does 0:16:57.680 --> 0:17:00.000 relativity only break down at the center of a black 0:17:00.920 --> 0:17:05.320 like the edge of a black holes safe to talk about. 0:17:06.720 --> 0:17:08.360 The edge of a black hole is really only something 0:17:08.400 --> 0:17:10.560 we can talk about in general relativity. We don't know 0:17:10.600 --> 0:17:13.720 how quantum mechanics will modify that. It might make it 0:17:13.760 --> 0:17:17.320 so that there are no event horizons. These fuzzballs. For example, 0:17:17.400 --> 0:17:21.200 compact states of strings do not have event horizons at all, 0:17:21.560 --> 0:17:23.560 So it could be that there are no event horizons 0:17:23.640 --> 0:17:25.959 in the universe. So if we want to talk about this, 0:17:26.160 --> 0:17:28.000 really the only thing we can do is talk about 0:17:28.080 --> 0:17:31.640 what general relativity predicts, even though we're not exactly sure 0:17:31.760 --> 0:17:32.280 it's real. 0:17:33.440 --> 0:17:35.320 So then how do you define the event horizon? 0:17:35.320 --> 0:17:38.320 Then? Well, in general relativity, the event horizon is the 0:17:38.359 --> 0:17:41.880 point past which no information can escape, and that's something 0:17:41.920 --> 0:17:44.480 we can calculate in general relativity, and it depends on 0:17:44.800 --> 0:17:47.520 the mass of the object, also whether it's spinning, whether 0:17:47.560 --> 0:17:49.320 it has charged these kinds of things. 0:17:50.560 --> 0:17:53.480 And it's kind of a very special point in a 0:17:53.600 --> 0:17:56.360 black hole because that's the point at which not even 0:17:56.400 --> 0:17:57.800 information can escape. 0:17:57.520 --> 0:17:58.760 Right, Yeah, that's right. 0:17:59.080 --> 0:18:01.440 So sort of is the things we can know about 0:18:01.440 --> 0:18:02.080 the black hole. 0:18:02.560 --> 0:18:05.199 Yeah, you can't know anything that's going on inside the 0:18:05.240 --> 0:18:08.080 black hole, but you can measure some things about the 0:18:08.119 --> 0:18:10.600 black hole, like we know, for example, obviously you can 0:18:10.640 --> 0:18:13.320 measure the black hole's mass, you can measure its gravitational 0:18:13.359 --> 0:18:16.840 effects on things nearby. If you fly near a black hole, 0:18:16.920 --> 0:18:19.359 you're going to be drawn towards it because space is 0:18:19.520 --> 0:18:22.959 curved so the effect of the black hole exists outside 0:18:23.000 --> 0:18:24.840 the event horizon. You can sort of think of it 0:18:25.080 --> 0:18:28.680 as the event horizon itself having a property. The event 0:18:28.720 --> 0:18:31.760 horizon is there, it summarizes all the stuff that's inside 0:18:31.800 --> 0:18:33.840 of it. The mass of the event horizon or the 0:18:33.840 --> 0:18:37.639 black hole itself, affects space outside the event horizon. So 0:18:37.680 --> 0:18:39.680 you can definitely know that about the black hole, and 0:18:39.720 --> 0:18:42.040 you can know a couple of other details as well. 0:18:42.800 --> 0:18:45.880 Like the spin and also the charge of a black hole. 0:18:45.960 --> 0:18:48.679 Right, yeah, that's right. Those are the three things that 0:18:48.760 --> 0:18:51.720 general relativity says we can know about the black hole. 0:18:52.119 --> 0:18:54.720 That a black hole can also be spinning, right, Things 0:18:54.720 --> 0:18:57.960 that fall into a black hole, if they have angular momentum, 0:18:57.960 --> 0:19:01.040 they have to keep having angular momentum because in our universe, 0:19:01.040 --> 0:19:04.480 angular momentum is conserved. We're pretty sure. Same thing with 0:19:04.560 --> 0:19:08.520 electric charge. The universe strictly preserves electric charge. We've never 0:19:08.560 --> 0:19:12.000 seen that violated. You can create plus and minus particles together, 0:19:12.280 --> 0:19:14.919 but the overall charge of the universe has to be 0:19:14.960 --> 0:19:17.920 the same. And so if you drop an electron into 0:19:17.960 --> 0:19:20.240 a black hole, then the black hole has to have 0:19:20.280 --> 0:19:23.040 that charge because it can't just disappear from the universe. 0:19:23.480 --> 0:19:26.280 So mass, spin, and charge are the things you can 0:19:26.359 --> 0:19:29.480 know about a black hole from the outside. You can't 0:19:29.520 --> 0:19:32.199 know like the arrangement of charges or masses or spins 0:19:32.280 --> 0:19:35.239 or whatever inside the event horizon, but you don't have 0:19:35.320 --> 0:19:37.480 to in order to know the total mass or the 0:19:37.520 --> 0:19:40.160 total charge or the total spin from the outside. 0:19:40.880 --> 0:19:42.399 Can you tell if that black hole has a headache 0:19:42.480 --> 0:19:42.840 or something? 0:19:45.600 --> 0:19:47.880 Do black holes wear mood rings? I wish they did? 0:19:48.119 --> 0:19:48.720 Always black? 0:19:48.920 --> 0:19:53.280 Does that mean do they wear engagement rings? Well, you 0:19:53.320 --> 0:19:57.520 said charge, and I'm wondering. You know, that's the electromagnetic charge, 0:19:57.560 --> 0:19:59.440 but we also talk about it in this podcast. But 0:19:59.600 --> 0:20:02.720 other of charge in the universe, from the weak fours 0:20:02.760 --> 0:20:06.199 and the strong force. Can you know those other charges 0:20:06.240 --> 0:20:08.520 about a black hole? Can you know the color of 0:20:08.560 --> 0:20:09.160 a black hole? 0:20:09.560 --> 0:20:12.920 The color charges are really fun and tricky concept. It's 0:20:12.920 --> 0:20:15.879 not something we really understand very well because objects that 0:20:15.920 --> 0:20:18.520