1 00:00:08,640 --> 00:00:11,760 Speaker 1: Hey, Katie, have you ever been to Las Vegas? I 2 00:00:12,160 --> 00:00:16,400 Speaker 1: have once, and so what did you think about America's 3 00:00:16,480 --> 00:00:17,880 Speaker 1: favorite adult playground? 4 00:00:18,200 --> 00:00:20,880 Speaker 2: Well, I can't really tell you. 5 00:00:21,600 --> 00:00:24,280 Speaker 1: Is that because it was so much fun you remember nothing? 6 00:00:24,560 --> 00:00:27,880 Speaker 2: I mean, it is a bit of an information black hole. 7 00:00:28,120 --> 00:00:29,640 Speaker 1: You mean, like you don't want to talk about it. 8 00:00:29,680 --> 00:00:31,960 Speaker 1: Like what happens in Vegas stays in Vegas. 9 00:00:32,320 --> 00:00:36,120 Speaker 2: It is a singular experience for sure. 10 00:00:36,520 --> 00:00:39,480 Speaker 1: All right, we'll leave that past. The Katie event arrived. 11 00:00:41,760 --> 00:00:43,599 Speaker 2: Like they're just handing out margarite? 12 00:00:43,720 --> 00:00:55,480 Speaker 3: Is there? What am I supposed to say? 13 00:01:00,840 --> 00:01:00,960 Speaker 4: Hi? 14 00:01:01,200 --> 00:01:04,560 Speaker 1: I'm Daniel. I'm a particle physicist and a professor at 15 00:01:04,760 --> 00:01:08,680 Speaker 1: UC Irvine, and I have definitely been to Vegas. 16 00:01:08,920 --> 00:01:12,840 Speaker 2: I am Katie Golden, I am made out of particles. 17 00:01:13,319 --> 00:01:19,319 Speaker 2: I host a podcast about animals, and I mostly liked 18 00:01:19,360 --> 00:01:23,640 Speaker 2: the food from Las Vegas, not so much the casinos. 19 00:01:23,800 --> 00:01:27,080 Speaker 1: I recently went to Vegas with my thirteen year old daughter, 20 00:01:27,160 --> 00:01:30,760 Speaker 1: which was quite an experience to see it through her eyes. 21 00:01:30,959 --> 00:01:33,400 Speaker 1: Definitely a place to go at least once. 22 00:01:33,800 --> 00:01:37,959 Speaker 2: It is a fascinating city. I regret that I have 23 00:01:38,040 --> 00:01:40,920 Speaker 2: not been there since they have put the giant orban. 24 00:01:41,480 --> 00:01:43,600 Speaker 1: Yeah, the orb is cool. There's definitely a lot of 25 00:01:43,600 --> 00:01:46,000 Speaker 1: stuff you can do even if you're not eighteen or 26 00:01:46,040 --> 00:01:49,080 Speaker 1: twenty one plus, though some of the stuff she wanted 27 00:01:49,080 --> 00:01:52,160 Speaker 1: to do, like drive tanks through the desert and shoot 28 00:01:52,200 --> 00:01:55,360 Speaker 1: automatic weapons were definitely age restricted. 29 00:01:55,560 --> 00:01:59,000 Speaker 2: Yeah, I have a friend who I think shot guns 30 00:01:59,040 --> 00:02:02,120 Speaker 2: from a helicopter in Vegas. There's a lot of things 31 00:02:02,160 --> 00:02:02,640 Speaker 2: you can do. 32 00:02:02,880 --> 00:02:06,240 Speaker 1: There's all sorts of crazy stuff you can do in Vegas, 33 00:02:06,440 --> 00:02:08,920 Speaker 1: stuff that helps you understand who you are and who 34 00:02:09,040 --> 00:02:12,760 Speaker 1: you aren't. And Welcome to the podcast Daniel and Jorge 35 00:02:12,840 --> 00:02:15,120 Speaker 1: Explain the Universe, in which we try to explain to 36 00:02:15,160 --> 00:02:18,320 Speaker 1: you what the universe is and what the universe isn't. 37 00:02:18,600 --> 00:02:21,000 Speaker 1: We try to pull back the curtain and help you 38 00:02:21,240 --> 00:02:24,840 Speaker 1: understand what's going on out there in the deepest, darkest 39 00:02:24,960 --> 00:02:25,720 Speaker 1: regions of. 40 00:02:25,680 --> 00:02:27,880 Speaker 2: Space, such as Las Vegas. 41 00:02:30,240 --> 00:02:33,000 Speaker 1: There is no Vegas casino yet called the black Hole, 42 00:02:33,160 --> 00:02:35,760 Speaker 1: but I am assuming one it will eventually open up. 43 00:02:35,840 --> 00:02:39,840 Speaker 2: That is a missed opportunity, or like a mini golf 44 00:02:39,840 --> 00:02:41,239 Speaker 2: course called the black. 45 00:02:40,919 --> 00:02:43,880 Speaker 1: Holes that just sucks in all the balls. Well, on 46 00:02:43,919 --> 00:02:46,680 Speaker 1: this podcast, we do try to explain to you black 47 00:02:46,680 --> 00:02:49,959 Speaker 1: holes and also how everything works on the smallest scales 48 00:02:50,000 --> 00:02:52,800 Speaker 1: because we don't just want to describe the universe to you. 49 00:02:52,919 --> 00:02:55,359 Speaker 1: We want to explain it. We want you to get 50 00:02:55,360 --> 00:02:59,400 Speaker 1: an understanding, a microscopic picture of how everything around you 51 00:02:59,520 --> 00:03:02,120 Speaker 1: actually works. We want to dive deep into the very 52 00:03:02,200 --> 00:03:05,480 Speaker 1: nature of reality and come out with a bottom up 53 00:03:05,639 --> 00:03:09,520 Speaker 1: understanding of how the universe actually works. My friend Jorge 54 00:03:09,560 --> 00:03:11,440 Speaker 1: can't be here today, but I'm very glad to be 55 00:03:11,560 --> 00:03:14,840 Speaker 1: joined by one of our regular co hosts. Thanks Katie 56 00:03:14,880 --> 00:03:17,320 Speaker 1: for joining us on this black Hole of an episode. 57 00:03:17,520 --> 00:03:20,680 Speaker 2: I am excited because no matter how many times you 58 00:03:20,720 --> 00:03:24,200 Speaker 2: explain to me what a black hole is, I still 59 00:03:24,280 --> 00:03:28,200 Speaker 2: feel like I cannot wrap my head around it. So surely, 60 00:03:28,480 --> 00:03:32,000 Speaker 2: surely this will be the episode where I understand black holes. 61 00:03:32,240 --> 00:03:34,600 Speaker 1: Well, I would say there's probably nobody out there who 62 00:03:34,680 --> 00:03:39,760 Speaker 1: fully deeply understands black holes, because to fully deeply understand something, 63 00:03:39,800 --> 00:03:43,280 Speaker 1: I think we need a particle level explanation for it. 64 00:03:43,400 --> 00:03:45,160 Speaker 1: You know, we need to be able to moot up 65 00:03:45,160 --> 00:03:47,760 Speaker 1: from the tiniest little bits and say, here's what's really 66 00:03:47,800 --> 00:03:50,240 Speaker 1: happening at the smallest scales when you get sucked into 67 00:03:50,280 --> 00:03:53,320 Speaker 1: a black hole or when photons try to escape. And 68 00:03:53,360 --> 00:03:55,960 Speaker 1: the reason I say that nobody understands them is that 69 00:03:56,000 --> 00:03:59,800 Speaker 1: we do not have a particle level understanding of black 70 00:03:59,840 --> 00:04:02,160 Speaker 1: hole holes. The way, for example, we can understand what 71 00:04:02,240 --> 00:04:05,520 Speaker 1: happens when photons go through glass, They interact with the atoms, 72 00:04:05,520 --> 00:04:07,480 Speaker 1: the electrons and all that stuff in there, and it 73 00:04:07,560 --> 00:04:09,920 Speaker 1: bends their path, and we have some way to tell 74 00:04:09,960 --> 00:04:13,320 Speaker 1: a story microscopically if what's happening to those photons and 75 00:04:13,600 --> 00:04:17,440 Speaker 1: related to what we see actually macroscopically, we can't do 76 00:04:17,560 --> 00:04:21,120 Speaker 1: that for black holes because we don't understand particles and gravity. 77 00:04:21,400 --> 00:04:24,040 Speaker 1: We have no theory of quantum gravity that tells us 78 00:04:24,320 --> 00:04:27,960 Speaker 1: what happens to particles when they feel gravity, and that's 79 00:04:27,960 --> 00:04:31,279 Speaker 1: what black holes are all about. Gravity. So we don't 80 00:04:31,320 --> 00:04:35,360 Speaker 1: have this sort of deep down, microscopic understanding of black holes. 81 00:04:35,400 --> 00:04:38,680 Speaker 1: So probably nobody understands, but that doesn't stop us from 82 00:04:38,720 --> 00:04:41,000 Speaker 1: asking questions and from trying to grapple with what we 83 00:04:41,200 --> 00:04:44,599 Speaker 1: have learned about black holes. Then, on this podcast, we 84 00:04:44,720 --> 00:04:47,359 Speaker 1: encourage everybody to think deeply about the universe and to 85 00:04:47,400 --> 00:04:49,920 Speaker 1: try to fit these ideas into their heads, to ask 86 00:04:49,960 --> 00:04:53,080 Speaker 1: themselves questions to see does this make sense to you? 87 00:04:53,320 --> 00:04:55,240 Speaker 1: Is it possible for you to grapple with what we 88 00:04:55,320 --> 00:04:57,680 Speaker 1: do and do not know about black holes. 89 00:04:58,040 --> 00:05:02,760 Speaker 2: The problem, Daniel is I have a finite number of neurons, 90 00:05:03,600 --> 00:05:08,200 Speaker 2: a finite sort of number of synaptic pathways in my brain, 91 00:05:08,680 --> 00:05:11,320 Speaker 2: and it is very difficult for those little guys to 92 00:05:12,560 --> 00:05:16,280 Speaker 2: understand all we know about black holes and what we 93 00:05:16,360 --> 00:05:19,560 Speaker 2: don't know about black holes. If we were somehow able 94 00:05:19,680 --> 00:05:22,800 Speaker 2: to measure everything about a black hole, do you think 95 00:05:22,839 --> 00:05:25,599 Speaker 2: we could even fully understand it? As humans? 96 00:05:25,920 --> 00:05:28,839 Speaker 1: It's a deep question in philosophy, like are we even 97 00:05:29,040 --> 00:05:33,080 Speaker 1: capable of describing the universe in our minds? Can we 98 00:05:33,200 --> 00:05:35,839 Speaker 1: understand the universe? And not a question I know the 99 00:05:35,920 --> 00:05:39,840 Speaker 1: answer to or I think anybody knows the answer to. Amazingly, 100 00:05:40,120 --> 00:05:42,880 Speaker 1: so far we have been able to do it, to 101 00:05:43,320 --> 00:05:46,880 Speaker 1: write these little mathematical models, tell ourselves these little stories 102 00:05:46,880 --> 00:05:49,520 Speaker 1: in our minds, and use them to explain everything that 103 00:05:49,560 --> 00:05:53,920 Speaker 1: we see and everything we experience, everything our experiments tell us. 104 00:05:54,680 --> 00:05:57,320 Speaker 1: Is it possible for us to understand them? The smartest 105 00:05:57,400 --> 00:05:59,920 Speaker 1: human I don't know. I think there probably is a 106 00:06:00,360 --> 00:06:03,359 Speaker 1: limit to how smart the smartest human is, and so 107 00:06:03,400 --> 00:06:05,680 Speaker 1: it might be that the universe it's just more complex 108 00:06:05,720 --> 00:06:08,320 Speaker 1: than that, and that no human, regardless of how smart 109 00:06:08,360 --> 00:06:11,000 Speaker 1: they are, could ever understand it. But you know, we've 110 00:06:11,000 --> 00:06:13,719 Speaker 1: been making a lot of progress in recent years asking 111 00:06:13,800 --> 00:06:16,680 Speaker 1: and answering questions about the deepest nature of the universe 112 00:06:16,760 --> 00:06:19,560 Speaker 1: and about black holes. So I'm kind of bullish on 113 00:06:19,640 --> 00:06:23,800 Speaker 1: the possibility for some humans someday to understand it. And 114 00:06:24,040 --> 00:06:26,839 Speaker 1: that's not just limited to like the Albert Einsteins of 115 00:06:26,920 --> 00:06:29,760 Speaker 1: the world. I think it's possible for basically everybody out 116 00:06:29,800 --> 00:06:33,080 Speaker 1: there to get some kind of intuitive grasp or how 117 00:06:33,240 --> 00:06:36,320 Speaker 1: black holes work. One thing I love about hearing from 118 00:06:36,360 --> 00:06:39,400 Speaker 1: listeners to the podcast is that it's been teaching them 119 00:06:39,440 --> 00:06:42,440 Speaker 1: to think like a physicist, you know, like, what does 120 00:06:42,480 --> 00:06:45,440 Speaker 1: that mean? To think like a physicist? It means to 121 00:06:45,600 --> 00:06:48,480 Speaker 1: try to understand the world around you, to tell yourself stories, 122 00:06:48,480 --> 00:06:51,960 Speaker 1: to ask yourself questions, to say, do I understand how 123 00:06:52,000 --> 00:06:54,880 Speaker 1: this works? To put these models in your head and 124 00:06:54,960 --> 00:06:56,920 Speaker 1: like turn them around and say, well, if that's true, 125 00:06:57,040 --> 00:06:58,839 Speaker 1: doesn't it mean this or how does this connect with 126 00:06:58,880 --> 00:07:02,520 Speaker 1: this other thing I do understand? And that's especially important 127 00:07:02,560 --> 00:07:05,640 Speaker 1: for weird things like black holes. So we get lots 128 00:07:05,680 --> 00:07:08,600 Speaker 1: of questions from listeners who're doing just that. Wh we're 129 00:07:08,640 --> 00:07:11,480 Speaker 1: trying to think like a physicist about black holes? To 130 00:07:11,520 --> 00:07:15,480 Speaker 1: try to incorporate it into the mathematical stories in their minds. 131 00:07:15,840 --> 00:07:20,480 Speaker 2: This podcast is Daniel's secret weapon of trying to convert 132 00:07:20,640 --> 00:07:25,360 Speaker 2: everyone into physicists. We are onto you, Daniel. You are 133 00:07:25,400 --> 00:07:28,960 Speaker 2: trying to create an army of physicists. There are so 134 00:07:29,120 --> 00:07:33,160 Speaker 2: many questions that I have about black holes. It's hard 135 00:07:33,160 --> 00:07:36,000 Speaker 2: for me to even think about how to phrase my 136 00:07:36,160 --> 00:07:40,440 Speaker 2: confusion about black holes into a question. So just being 137 00:07:40,520 --> 00:07:46,200 Speaker 2: able to ask a distinct, coherent question about black holes, 138 00:07:46,240 --> 00:07:47,240 Speaker 2: I think is impressive. 139 00:07:48,400 --> 00:07:50,680 Speaker 1: I mean, your question about black holes is like black holes, 140 00:07:50,880 --> 00:07:51,920 Speaker 1: what's the deal with that? 141 00:07:52,440 --> 00:07:56,760 Speaker 2: Yeah? My question is like, huh what. 142 00:07:57,400 --> 00:07:59,560 Speaker 1: That's the first step, right, is to be confused, and 143 00:07:59,560 --> 00:08:01,880 Speaker 1: then the second second step is to try to weave 144 00:08:01,920 --> 00:08:04,560 Speaker 1: together a few bits of information and say, like, what 145 00:08:04,720 --> 00:08:07,320 Speaker 1: parts specifically of the story don't make sense to me? 146 00:08:07,360 --> 00:08:09,400 Speaker 1: Which parts do I need to understand better in order 147 00:08:09,400 --> 00:08:11,920 Speaker 1: to have something in my mind that does work where 148 00:08:11,920 --> 00:08:14,560 Speaker 1: the understanding does click. Because what I'd love is for 149 00:08:14,600 --> 00:08:16,680 Speaker 1: people to have that moment where they're like, oh, I 150 00:08:16,760 --> 00:08:19,200 Speaker 1: get it. This connects with that thing, and now it 151 00:08:19,360 --> 00:08:21,920 Speaker 1: kind of makes sense to me, even though it's pretty 152 00:08:21,920 --> 00:08:23,640 Speaker 1: weird and a lot of people out there are trying 153 00:08:23,640 --> 00:08:26,040 Speaker 1: to do that, and many of them have run into 154 00:08:26,080 --> 00:08:29,280 Speaker 1: the same stumbling block. And so today on the podcast, 155 00:08:29,320 --> 00:08:32,040 Speaker 1: I want to answer a very common question that we 156 00:08:32,160 --> 00:08:41,800 Speaker 1: get about black holes. Can gravity escape a black hole? 157 00:08:42,360 --> 00:08:44,960 Speaker 2: I feel like I'm going crossside just trying to think 158 00:08:44,960 --> 00:08:45,840 Speaker 2: about this question. 159 00:08:46,000 --> 00:08:48,520 Speaker 1: I love this question because it reveals that people are 160 00:08:48,520 --> 00:08:51,880 Speaker 1: being physicists. They're thinking about what a black hole is, 161 00:08:51,960 --> 00:08:54,840 Speaker 1: how everything gets sucked into it, how nothing can escape. 162 00:08:55,200 --> 00:08:57,280 Speaker 1: But they're also thinking, hold on a second, we feel 163 00:08:57,320 --> 00:09:00,840 Speaker 1: gravity from a black hole. How's that possible? How can 164 00:09:00,880 --> 00:09:04,120 Speaker 1: the gravity get out of the black hole? And right there, 165 00:09:04,360 --> 00:09:07,240 Speaker 1: that's being a physicist, that's saying I was told this, 166 00:09:07,520 --> 00:09:09,760 Speaker 1: But there's also that how do I make this and 167 00:09:09,800 --> 00:09:12,080 Speaker 1: that work together? How do I put it together in 168 00:09:12,200 --> 00:09:14,480 Speaker 1: my head to tell a story that makes sense. 169 00:09:15,080 --> 00:09:18,280 Speaker 2: So what you're asking us to do is to listen 170 00:09:18,320 --> 00:09:21,240 Speaker 2: to what you're saying and then go hold on, Daniel, 171 00:09:21,679 --> 00:09:24,640 Speaker 2: you just said this. Are you lying to us? 172 00:09:27,120 --> 00:09:30,960 Speaker 1: Everybody's doing their best, nobody's lying to anybody. But in 173 00:09:31,000 --> 00:09:33,560 Speaker 1: the end, learning is a very personal experience, and an 174 00:09:33,559 --> 00:09:35,920 Speaker 1: explanation that makes sense to one person doesn't work for 175 00:09:36,160 --> 00:09:38,440 Speaker 1: somebody else. So that's why in this podcast, we often 176 00:09:38,480 --> 00:09:41,839 Speaker 1: try two or three different analogies or explanations or ways 177 00:09:41,880 --> 00:09:44,920 Speaker 1: to communicate an idea, and that's what you're here for, Katie, 178 00:09:44,960 --> 00:09:47,760 Speaker 1: also to make sure that what I'm saying makes sense 179 00:09:47,920 --> 00:09:48,280 Speaker 1: to you. 180 00:09:48,480 --> 00:09:51,719 Speaker 2: My method of learning is definitely food based metaphors. I'm 181 00:09:51,800 --> 00:09:52,840 Speaker 2: very food motivated. 182 00:09:53,120 --> 00:09:54,760 Speaker 1: Is your appetite something like a black hole? 183 00:09:55,000 --> 00:09:57,480 Speaker 2: It's something like that. Yeah, one could say I'm a 184 00:09:57,480 --> 00:10:00,439 Speaker 2: bit of a black hole, but yeah, I mean, it's 185 00:10:00,480 --> 00:10:04,200 Speaker 2: a very interesting question because it's hard for me to 186 00:10:04,280 --> 00:10:07,520 Speaker 2: think of gravity as like a thing, right, like a 187 00:10:07,559 --> 00:10:12,920 Speaker 2: thing that can escape something. Gravity to me is like, well, 188 00:10:13,040 --> 00:10:17,280 Speaker 2: I don't even know exactly what gravity is. I remember 189 00:10:17,360 --> 00:10:21,960 Speaker 2: from previous podcasts the things that you've taught me about gravity, 190 00:10:22,000 --> 00:10:26,120 Speaker 2: but it is so hard for me to conceptualize gravity 191 00:10:26,200 --> 00:10:28,360 Speaker 2: because it feels like it is like a kind of 192 00:10:28,440 --> 00:10:33,760 Speaker 2: thing woven into like the universe, that is not necessarily like, 193 00:10:34,360 --> 00:10:37,920 Speaker 2: you know, a physical matter thing, but it has everything 194 00:10:37,960 --> 00:10:41,000 Speaker 2: to do with physics. So it's it's a very confusing 195 00:10:41,600 --> 00:10:45,240 Speaker 2: kind of concept. And then you add to that the 196 00:10:45,320 --> 00:10:49,600 Speaker 2: black hole, which itself is quite confusing, and so this 197 00:10:49,760 --> 00:10:52,800 Speaker 2: question feels no pun intended, but very heavy. 198 00:10:52,960 --> 00:10:55,200 Speaker 1: Exactly well, you put your finger on. Really the concepts 199 00:10:55,200 --> 00:10:57,560 Speaker 1: here that are entertangled. You know, what do we know 200 00:10:57,640 --> 00:11:02,319 Speaker 1: about gravity? How is gravitation information communicated? Like? How is 201 00:11:02,360 --> 00:11:05,439 Speaker 1: it that you are feeling gravity from the sun even 202 00:11:05,480 --> 00:11:07,840 Speaker 1: though the Sun is super dup far away and not 203 00:11:08,080 --> 00:11:12,040 Speaker 1: touching you. Does that count as information you're getting from 204 00:11:12,040 --> 00:11:14,920 Speaker 1: the sun? What kind of stuff is captured by a 205 00:11:14,960 --> 00:11:17,600 Speaker 1: black hole? And what isn't captured by a black hole? 206 00:11:17,720 --> 00:11:20,679 Speaker 1: Is that information? How does that all work? You know? 207 00:11:20,720 --> 00:11:23,160 Speaker 1: Do you need to pass little particles back and forth 208 00:11:23,200 --> 00:11:25,679 Speaker 1: in order to feel gravity or what. So. One of 209 00:11:25,720 --> 00:11:27,920 Speaker 1: the reasons I love this question is that it combines 210 00:11:28,040 --> 00:11:32,240 Speaker 1: all of these fun, interesting, fascinating and difficult questions together, 211 00:11:32,320 --> 00:11:34,040 Speaker 1: and going through it I think is really helpful to 212 00:11:34,080 --> 00:11:36,400 Speaker 1: clarify for people what a black hole is and what 213 00:11:36,440 --> 00:11:39,520 Speaker 1: a black hole isn't and how physicists think about it. 214 00:11:39,559 --> 00:11:42,079 Speaker 1: But before we hear about how physicists think about it, 215 00:11:42,120 --> 00:11:44,679 Speaker 1: I wanted to hear what everybody else out there was 216 00:11:44,720 --> 00:11:46,960 Speaker 1: thinking about it. So we have a nice little team 217 00:11:46,960 --> 00:11:50,360 Speaker 1: of volunteers who answer questions for the podcast before we 218 00:11:50,400 --> 00:11:53,560 Speaker 1: dig into them. Helps me understand what people are thinking 219 00:11:53,800 --> 00:11:57,199 Speaker 1: and helps you calibrate your thoughts against the other listeners. 220 00:11:57,520 --> 00:12:00,560 Speaker 1: So thanks very much to everybody who participates. You want 221 00:12:00,559 --> 00:12:03,160 Speaker 1: to jump in for a future episode, we would love, love, 222 00:12:03,600 --> 00:12:06,600 Speaker 1: love to have your voice on the team. Right to me. 223 00:12:06,679 --> 00:12:11,160 Speaker 1: Two questions at Danielandjorge dot com, So think about it 224 00:12:11,160 --> 00:12:13,720 Speaker 1: for a moment before you hear these answers. Do you 225 00:12:13,760 --> 00:12:17,800 Speaker 1: think gravity can escape a black hole? Here's what people 226 00:12:17,840 --> 00:12:18,400 Speaker 1: had to say. 227 00:12:18,720 --> 00:12:21,840 Speaker 5: I feel like, since it kind of depends on the 228 00:12:21,840 --> 00:12:26,120 Speaker 5: mass of an object, it just moves with that object, 229 00:12:26,480 --> 00:12:29,880 Speaker 5: so it would be dependent on the object being able 230 00:12:29,880 --> 00:12:30,920 Speaker 5: to escape the black hole. 231 00:12:31,280 --> 00:12:34,000 Speaker 6: It really matters what we think of as gravity. If 232 00:12:34,000 --> 00:12:38,000 Speaker 6: you think it's gravito gravitons, like with the quantum theories, 233 00:12:38,760 --> 00:12:41,760 Speaker 6: then I guess it escapes. I think, yeah, gravity can 234 00:12:41,960 --> 00:12:45,280 Speaker 6: escape black holes, otherwise I wouldn't be stucking everything in. 235 00:12:45,559 --> 00:12:50,640 Speaker 7: Gravity is a distortion in space time, So I would 236 00:12:50,720 --> 00:12:56,400 Speaker 7: say that gravity itself cannot escape. Actually it's being created 237 00:12:56,440 --> 00:12:59,600 Speaker 7: by the black hole itself. But if we are talking 238 00:12:59,600 --> 00:13:03,640 Speaker 7: about gravitational waves, I believe it can escape a black 239 00:13:03,640 --> 00:13:07,559 Speaker 7: hole if it is outside the event horizon. I even 240 00:13:07,640 --> 00:13:12,760 Speaker 7: think that gravitational waves were discovered by watching collisions of 241 00:13:12,880 --> 00:13:16,839 Speaker 7: black holes and stuff like that. So my guess is yes, 242 00:13:17,360 --> 00:13:21,360 Speaker 7: under the right circumstances, gravitational waves should be able to 243 00:13:21,440 --> 00:13:22,280 Speaker 7: escape a black hole. 244 00:13:22,880 --> 00:13:24,800 Speaker 4: I can't even wrap my head around the question. 245 00:13:25,200 --> 00:13:27,160 Speaker 5: I didn't even know those words could go together. 246 00:13:27,880 --> 00:13:31,040 Speaker 4: I guess it can escape, because isn't that kind of 247 00:13:31,040 --> 00:13:32,560 Speaker 4: what gravitational waves are. 248 00:13:33,160 --> 00:13:38,679 Speaker 2: I love all of the references to gravitational waves because 249 00:13:38,800 --> 00:13:40,560 Speaker 2: we did an episode on that recently. 250 00:13:40,880 --> 00:13:44,040 Speaker 1: We did absolutely an episode on gravitational waves, and that's 251 00:13:44,080 --> 00:13:47,120 Speaker 1: going to turn out to be crucial in understanding what 252 00:13:47,280 --> 00:13:51,559 Speaker 1: is gravitational information and what is not, what is trapped 253 00:13:51,600 --> 00:13:54,400 Speaker 1: within the black hole, and what is not trapped within 254 00:13:54,440 --> 00:13:57,840 Speaker 1: the black hole. Absolutely, so, gravitational waves are a really 255 00:13:57,840 --> 00:13:59,400 Speaker 1: helpful way to think about that. 256 00:13:59,559 --> 00:14:05,640 Speaker 2: I get the root of this question. Is this seeming paradox, right, 257 00:14:05,880 --> 00:14:08,520 Speaker 2: the idea that nothing can escape from a black hole, 258 00:14:09,000 --> 00:14:12,600 Speaker 2: and yet we do know about black holes, We get 259 00:14:12,720 --> 00:14:16,959 Speaker 2: information about black holes, But how can we receive any 260 00:14:17,000 --> 00:14:20,960 Speaker 2: information about a black hole if it is something that 261 00:14:21,080 --> 00:14:24,480 Speaker 2: is all consuming and nothing can escape it? 262 00:14:24,840 --> 00:14:28,720 Speaker 1: Boom Exactly, Adie, you were officially a physicist because you 263 00:14:28,800 --> 00:14:32,520 Speaker 1: are putting together those two ideas that you understand and saying, 264 00:14:32,560 --> 00:14:34,760 Speaker 1: how can these two things be compatible. How can we 265 00:14:34,760 --> 00:14:39,280 Speaker 1: weave them together into a singular understanding of black holes? 266 00:14:39,320 --> 00:14:40,760 Speaker 1: And what it's going to take is a little bit 267 00:14:40,800 --> 00:14:43,080 Speaker 1: of a refinement of the idea of what a black 268 00:14:43,080 --> 00:14:45,800 Speaker 1: hole is and what a black hole isn't to make 269 00:14:45,840 --> 00:14:47,440 Speaker 1: this all work together in your head. 270 00:14:47,520 --> 00:14:49,680 Speaker 2: Well, now that you have proclaimed I am a physicist, 271 00:14:49,760 --> 00:14:52,120 Speaker 2: I am just gonna waltz into like the hard drung 272 00:14:52,240 --> 00:14:56,880 Speaker 2: collider and be like physicists coming through. Let's smash some particles. 273 00:14:56,960 --> 00:14:57,320 Speaker 3: Guys. 274 00:14:57,680 --> 00:15:00,440 Speaker 1: That's right, you have officially a PhD in podcast physics 275 00:15:00,800 --> 00:15:03,360 Speaker 1: from the Daniel and Jorge University. 276 00:15:04,080 --> 00:15:07,080 Speaker 2: Worth its weight in gold. So yes, I would love 277 00:15:07,200 --> 00:15:12,160 Speaker 2: some clarification on what a black hole is. You know, 278 00:15:12,320 --> 00:15:17,000 Speaker 2: I know it's a big, sucky thing. I understand that 279 00:15:17,400 --> 00:15:23,320 Speaker 2: it has something to do with just an incredible density 280 00:15:24,120 --> 00:15:30,760 Speaker 2: of matter, and furthermore that gravity is very much a 281 00:15:30,800 --> 00:15:33,560 Speaker 2: defining characteristic of a black hole. 282 00:15:33,760 --> 00:15:35,400 Speaker 1: Then let's make sure we know what it is we're 283 00:15:35,440 --> 00:15:39,080 Speaker 1: talking about. So a black hole is a region of 284 00:15:39,240 --> 00:15:43,920 Speaker 1: space where the curvature of space is so powerful that 285 00:15:44,000 --> 00:15:48,800 Speaker 1: nothing that's inside that region can escape to outside, and 286 00:15:48,840 --> 00:15:51,480 Speaker 1: that region is defined by this threshold, not really like 287 00:15:51,520 --> 00:15:54,200 Speaker 1: a barrier, not like a physical wall. There's not got 288 00:15:54,200 --> 00:15:57,360 Speaker 1: a dotted line somebody draws in space that says beyond 289 00:15:57,400 --> 00:16:00,680 Speaker 1: this point, if you pass, then you will ever escape. 290 00:16:00,720 --> 00:16:03,200 Speaker 1: You'll be trapped within that region forever. 291 00:16:03,440 --> 00:16:06,600 Speaker 2: Someone's got to put a sign up, a warning, you know, warning, 292 00:16:06,680 --> 00:16:10,360 Speaker 2: do not pass this region. You will be spaghettified into 293 00:16:10,400 --> 00:16:13,160 Speaker 2: a black hole. But I mean, when you say space 294 00:16:13,280 --> 00:16:16,240 Speaker 2: is curved, you know, this is definitely a concept I've 295 00:16:16,280 --> 00:16:19,760 Speaker 2: been introduced to before, but it's still something that I 296 00:16:19,840 --> 00:16:24,160 Speaker 2: struggle to understand because when I think of curvature, right, 297 00:16:24,200 --> 00:16:27,160 Speaker 2: I think of like a physical object that is warped, 298 00:16:27,800 --> 00:16:30,160 Speaker 2: or like say, I think of fabric and I feel like, 299 00:16:30,480 --> 00:16:33,000 Speaker 2: you know, I think of pulling down on the fabric 300 00:16:33,040 --> 00:16:35,160 Speaker 2: and then they're being sort of a curvature and things 301 00:16:35,200 --> 00:16:39,000 Speaker 2: falling into it, and then that's how I think about gravity. 302 00:16:39,520 --> 00:16:43,520 Speaker 2: But I believe that is not really exactly the correct 303 00:16:44,040 --> 00:16:46,800 Speaker 2: understanding of it. Space is not like a piece of 304 00:16:46,800 --> 00:16:50,040 Speaker 2: fabric that you pull on and things fall into that 305 00:16:50,080 --> 00:16:54,080 Speaker 2: sort of like dip. But what exactly does curvature mean 306 00:16:54,280 --> 00:16:55,320 Speaker 2: in terms of space? 307 00:16:55,760 --> 00:16:58,040 Speaker 1: Yeah? Good, It's important to think about in terms of 308 00:16:58,080 --> 00:17:00,840 Speaker 1: curvature because I think a lot of people think about 309 00:17:00,840 --> 00:17:03,440 Speaker 1: black holes in sort of a Newtonian way, where gravity 310 00:17:03,520 --> 00:17:06,040 Speaker 1: is a force and the force of gravity is so 311 00:17:06,040 --> 00:17:09,120 Speaker 1: strong that it's sucking stuff up right, And that cartoon 312 00:17:09,160 --> 00:17:11,680 Speaker 1: model of a black hole breaks down very quickly because 313 00:17:11,680 --> 00:17:14,160 Speaker 1: it can't explain to you, like, well, why does light 314 00:17:14,240 --> 00:17:16,520 Speaker 1: get trapped by a black hole? Why can't a photon 315 00:17:16,920 --> 00:17:20,879 Speaker 1: not leave a black hole? Because the Newtonian picture of gravity, 316 00:17:21,160 --> 00:17:24,159 Speaker 1: gravity is a force between objects with mass, and photons 317 00:17:24,200 --> 00:17:26,480 Speaker 1: have no mass, so they should feel no gravity, and 318 00:17:26,520 --> 00:17:28,919 Speaker 1: so they should be able to escape. In order to 319 00:17:28,960 --> 00:17:31,760 Speaker 1: have an understanding of what black holes are, you really 320 00:17:31,800 --> 00:17:35,600 Speaker 1: have to move your thinking of gravity is from this 321 00:17:35,760 --> 00:17:40,760 Speaker 1: idea of forces between objects with mass to an apparent 322 00:17:40,880 --> 00:17:43,399 Speaker 1: force something that actually results from, as you say, the 323 00:17:43,480 --> 00:17:46,679 Speaker 1: curvature of space itself. So what do we mean by 324 00:17:46,720 --> 00:17:49,560 Speaker 1: the curvature of space itself? Means that space has a 325 00:17:49,720 --> 00:17:53,400 Speaker 1: characteristic to it that's invisible, something you can't see when 326 00:17:53,480 --> 00:17:55,639 Speaker 1: you look at it. You look at some chunk of 327 00:17:55,680 --> 00:17:58,800 Speaker 1: space and you can't tell whether or not it's curved. 328 00:17:59,000 --> 00:18:01,919 Speaker 1: But if you shine a laser beam through it, it 329 00:18:01,960 --> 00:18:04,320 Speaker 1: will either go in a straight line or it will not. 330 00:18:04,520 --> 00:18:06,440 Speaker 1: It will curve, it will bend. This way, or will 331 00:18:06,480 --> 00:18:10,320 Speaker 1: bend that way, because space has this additional, weird property 332 00:18:10,359 --> 00:18:13,119 Speaker 1: that Newton never imagined. And on the smaller scale, what 333 00:18:13,200 --> 00:18:16,880 Speaker 1: it means is that the relative distances between two points 334 00:18:16,960 --> 00:18:19,800 Speaker 1: can get changed. So when we say that like space 335 00:18:19,880 --> 00:18:22,439 Speaker 1: is curved or space is bent, it means that you 336 00:18:22,440 --> 00:18:25,440 Speaker 1: can take two locations in space, you can effectively make 337 00:18:25,440 --> 00:18:28,160 Speaker 1: them closer together, or you can make them further apart. 338 00:18:28,359 --> 00:18:30,879 Speaker 1: And what that does is it changes the path that 339 00:18:30,960 --> 00:18:33,400 Speaker 1: light will take through that space, because light always takes 340 00:18:33,400 --> 00:18:37,199 Speaker 1: the shortest path between two points. Now you're changing what 341 00:18:37,280 --> 00:18:40,240 Speaker 1: the relative distances are between two points, and so you're 342 00:18:40,320 --> 00:18:43,280 Speaker 1: changing the path that light will take. But I think 343 00:18:43,320 --> 00:18:45,119 Speaker 1: the most intuitive way to think about it is that 344 00:18:45,160 --> 00:18:47,840 Speaker 1: like space has this additional bit to it, this characteristic 345 00:18:48,280 --> 00:18:50,679 Speaker 1: so when a photon is passing through it, basically the 346 00:18:50,720 --> 00:18:54,160 Speaker 1: space tells the photon where to go, doesn't just pass 347 00:18:54,240 --> 00:18:54,960 Speaker 1: through blindly. 348 00:18:55,200 --> 00:18:58,800 Speaker 2: It's so interesting because I think the reason it's such 349 00:18:58,800 --> 00:19:03,719 Speaker 2: a difficult concept is that as humans we deal with 350 00:19:03,720 --> 00:19:09,520 Speaker 2: physics all the time, but we can observe Newtonian physics. 351 00:19:09,560 --> 00:19:13,040 Speaker 2: We can observe that type of physics, So it's I 352 00:19:13,040 --> 00:19:16,400 Speaker 2: think easier to think of particles when even like particles 353 00:19:16,400 --> 00:19:19,239 Speaker 2: that you can't observe with the naked eye when they 354 00:19:19,240 --> 00:19:22,879 Speaker 2: are behaving according to forces, because we can on the 355 00:19:22,920 --> 00:19:26,280 Speaker 2: more macro level observe forces. You can see a ball 356 00:19:26,359 --> 00:19:29,160 Speaker 2: knocking into a ball, you can see something fall down 357 00:19:29,200 --> 00:19:32,399 Speaker 2: a hole. But with gravity, even though yes, it's true, 358 00:19:32,480 --> 00:19:35,080 Speaker 2: we can observe gravity. We see it all the time, 359 00:19:35,240 --> 00:19:37,280 Speaker 2: right because you know, you jump up, you fall down. 360 00:19:37,760 --> 00:19:40,280 Speaker 2: It's one of the main problems that we have to 361 00:19:40,400 --> 00:19:44,119 Speaker 2: encounter as a physical being in the world, and yet 362 00:19:44,200 --> 00:19:49,720 Speaker 2: we can't actually see or kind of experience this like 363 00:19:50,119 --> 00:19:55,200 Speaker 2: secret framework behind gravity, which is that what you described, 364 00:19:55,280 --> 00:19:58,959 Speaker 2: like the relative distance between two things like becoming shorter 365 00:19:59,520 --> 00:20:04,119 Speaker 2: and like the actual like you know, space like reality 366 00:20:04,240 --> 00:20:07,439 Speaker 2: sort of warping in a way. It's like so easy 367 00:20:07,480 --> 00:20:10,359 Speaker 2: to fall into that trap of thinking of it in 368 00:20:10,480 --> 00:20:13,280 Speaker 2: terms of the type of physics that we see and 369 00:20:13,320 --> 00:20:13,920 Speaker 2: we observe. 370 00:20:14,160 --> 00:20:18,280 Speaker 1: It's confusing precisely because it's invisible. You can't see this 371 00:20:18,359 --> 00:20:21,199 Speaker 1: curvature of space. You can only see its effect, and 372 00:20:21,240 --> 00:20:24,159 Speaker 1: the effect of the curvature of space looks in almost 373 00:20:24,240 --> 00:20:27,280 Speaker 1: every case as if there was a force there. It 374 00:20:27,359 --> 00:20:30,760 Speaker 1: looks like there is this force we call gravity that's 375 00:20:30,800 --> 00:20:34,119 Speaker 1: pulling on things, when really things are just following the 376 00:20:34,160 --> 00:20:37,720 Speaker 1: curvature of space. The shape of space itself is changing 377 00:20:37,760 --> 00:20:41,200 Speaker 1: the direction in which things move. And if you can't 378 00:20:41,280 --> 00:20:43,600 Speaker 1: see space doing it, it's like a bunch of stage 379 00:20:43,600 --> 00:20:47,000 Speaker 1: hands wearing black nudging stuff. Then you imagine that there's 380 00:20:47,000 --> 00:20:49,240 Speaker 1: a force there. And so that's why we call gravity 381 00:20:49,320 --> 00:20:51,639 Speaker 1: and a parent force. It's not an actual force the 382 00:20:51,680 --> 00:20:54,800 Speaker 1: way like electromagnetism is, or the weak force or the 383 00:20:54,840 --> 00:20:58,240 Speaker 1: strong force. It's just the effect of the invisible curvature 384 00:20:58,400 --> 00:20:59,080 Speaker 1: of space. 385 00:20:59,480 --> 00:21:02,840 Speaker 2: So I hop down from let's say a safe height 386 00:21:03,440 --> 00:21:07,119 Speaker 2: and land on the ground. I am not really getting 387 00:21:07,480 --> 00:21:11,400 Speaker 2: sucked into the ground, because this is an effect of gravity, right, 388 00:21:11,440 --> 00:21:15,840 Speaker 2: The gravity of Earth is affecting me, and so I'm 389 00:21:15,880 --> 00:21:18,920 Speaker 2: not really getting sucked to the ground, but I am 390 00:21:19,520 --> 00:21:23,640 Speaker 2: like sort of just following where space is curving. 391 00:21:24,000 --> 00:21:27,000 Speaker 1: Yeah, that's a great example. Let's walk through it in 392 00:21:27,040 --> 00:21:30,240 Speaker 1: the sort of Newtonian intuitive picture, and then let's move 393 00:21:30,280 --> 00:21:33,360 Speaker 1: over to the Einstein space curvature picture. You'll find that 394 00:21:33,440 --> 00:21:36,320 Speaker 1: it's a very different story about exactly the same thing. 395 00:21:36,920 --> 00:21:39,199 Speaker 1: So in the Newtonian way of thinking, where gravity is 396 00:21:39,200 --> 00:21:42,040 Speaker 1: a force, you are standing on a chair, and you 397 00:21:42,119 --> 00:21:44,240 Speaker 1: imagine that there's a force of gravity pulling you down, 398 00:21:44,440 --> 00:21:46,120 Speaker 1: and there's a force of the chair pulling you up, 399 00:21:46,160 --> 00:21:48,480 Speaker 1: and when you stand on the chair, all forces are balanced, 400 00:21:48,480 --> 00:21:51,000 Speaker 1: so you're not going anywhere. You jump off the chair 401 00:21:51,080 --> 00:21:52,960 Speaker 1: and then you fall down because all you have is 402 00:21:52,960 --> 00:21:55,479 Speaker 1: the force of gravity pulling you down. There's nothing pushing 403 00:21:55,520 --> 00:21:58,359 Speaker 1: you up until you hit the surface of the Earth, 404 00:21:58,440 --> 00:21:59,639 Speaker 1: right in the surace of the Earth, and it's now 405 00:21:59,680 --> 00:22:03,040 Speaker 1: pushing back up on you, and so the forces are 406 00:22:03,080 --> 00:22:05,720 Speaker 1: now balanced and you're not moving anymore. Cool. So that's 407 00:22:05,760 --> 00:22:10,160 Speaker 1: the Newtonian picture. Einstein says, actually that's all wrong, that jerk. 408 00:22:11,520 --> 00:22:13,840 Speaker 1: There is no force of gravity, and that when you're falling, 409 00:22:13,880 --> 00:22:16,680 Speaker 1: when you jump off that chair, what's happening is you're 410 00:22:16,720 --> 00:22:20,200 Speaker 1: following the curvature of the Earth. You're in free fall. 411 00:22:20,480 --> 00:22:23,320 Speaker 1: There is no force on you at all. And in fact, 412 00:22:23,640 --> 00:22:26,160 Speaker 1: if you are carrying a little accelerometer with you, something 413 00:22:26,200 --> 00:22:29,120 Speaker 1: which can measure whether you're accelerating, essentially if there's any 414 00:22:29,160 --> 00:22:31,600 Speaker 1: force on you. Example of an accelerometer is just like 415 00:22:32,040 --> 00:22:34,080 Speaker 1: a ball in a box, Like is the ball pushed 416 00:22:34,080 --> 00:22:36,960 Speaker 1: towards one side or the other? Where Like a bowling 417 00:22:37,000 --> 00:22:39,320 Speaker 1: ball in a truck will tell you whether you're breaking 418 00:22:39,440 --> 00:22:41,920 Speaker 1: or accelerating. If you jump off that chair and you're 419 00:22:41,920 --> 00:22:44,479 Speaker 1: holding an accelerometer, you can do this experiment. You will 420 00:22:44,560 --> 00:22:48,200 Speaker 1: not measure any acceleration. You will not measure anything because 421 00:22:48,240 --> 00:22:51,520 Speaker 1: in that case, you are not accelerating. Einstein says that 422 00:22:51,560 --> 00:22:54,720 Speaker 1: you're actually accelerating when you're standing on the chair. That 423 00:22:54,800 --> 00:22:57,800 Speaker 1: what you're doing there is you're accelerating against the curvature 424 00:22:57,920 --> 00:23:00,760 Speaker 1: of the Earth. And also when you're standing on the earth, 425 00:23:00,880 --> 00:23:04,200 Speaker 1: you're accelerating upwards against your natural path, which would be 426 00:23:04,240 --> 00:23:08,080 Speaker 1: following the curvature of gravity towards the center of the Earth. 427 00:23:08,200 --> 00:23:13,520 Speaker 2: The chair is essentially blocking where you should go naturally 428 00:23:13,600 --> 00:23:17,120 Speaker 2: go by following where space is telling you to go. 429 00:23:17,359 --> 00:23:19,560 Speaker 1: Exactly, if you jump off the chair, you're in free fall. 430 00:23:19,600 --> 00:23:22,040 Speaker 1: You're not accelerating at all. You see people who are 431 00:23:22,040 --> 00:23:25,639 Speaker 1: still on their chairs as accelerating upwards against the natural 432 00:23:25,680 --> 00:23:27,399 Speaker 1: direction gravity wants to take you. 433 00:23:27,760 --> 00:23:31,960 Speaker 2: So, if I'm holding something like a feather, say, and 434 00:23:32,000 --> 00:23:35,560 Speaker 2: I jump off a chair, the feather goes slower than me. 435 00:23:36,240 --> 00:23:40,120 Speaker 2: Is the only reason that happens because of wind resistance. 436 00:23:40,440 --> 00:23:43,240 Speaker 1: Yeah, in that case, it's the air is accelerating the 437 00:23:43,280 --> 00:23:46,800 Speaker 1: feather up. It's preventing the feather from following the curvature 438 00:23:46,800 --> 00:23:50,159 Speaker 1: of space. The air itself is pushing on the feather. 439 00:23:50,200 --> 00:23:55,200 Speaker 2: And that's why an ant can survive really high falls, 440 00:23:55,240 --> 00:23:58,040 Speaker 2: whereas a person could not. Even though the ant seems 441 00:23:58,119 --> 00:24:03,080 Speaker 2: much more structurally delicate than a human because it's so small, 442 00:24:03,520 --> 00:24:07,560 Speaker 2: The air is basically like this huge you know resistance, 443 00:24:07,600 --> 00:24:11,359 Speaker 2: this huge force that is, you know, blocking the ant 444 00:24:11,840 --> 00:24:15,439 Speaker 2: from I guess following the curvature of space. 445 00:24:15,880 --> 00:24:16,040 Speaker 7: Yeah. 446 00:24:16,080 --> 00:24:18,439 Speaker 1: I think there's also something there about the structure of 447 00:24:18,560 --> 00:24:21,120 Speaker 1: ants when they land, but I'm not a biologist. 448 00:24:21,400 --> 00:24:25,119 Speaker 2: They just stick the dismount amazingly. If you zoom in 449 00:24:25,200 --> 00:24:28,320 Speaker 2: on an ant, it does a little summrsalt, lands, and 450 00:24:28,400 --> 00:24:29,480 Speaker 2: then takes a little bow. 451 00:24:29,920 --> 00:24:32,439 Speaker 1: So this picture of gravity is this curvature in space 452 00:24:32,560 --> 00:24:34,760 Speaker 1: rather than a force, gives us a new way to 453 00:24:34,800 --> 00:24:37,680 Speaker 1: think about a black hole. It's not a very dense 454 00:24:37,800 --> 00:24:40,959 Speaker 1: mass that has very strong sucking gravity because of all 455 00:24:41,040 --> 00:24:43,080 Speaker 1: the mass in it. It's a region of space where 456 00:24:43,119 --> 00:24:46,200 Speaker 1: the curvature is such that there is no path outwards, 457 00:24:46,560 --> 00:24:50,280 Speaker 1: where every direction is towards the center of the black hole. 458 00:24:50,640 --> 00:24:53,480 Speaker 1: Anything that's flying along is going to follow the curvature 459 00:24:53,520 --> 00:24:57,080 Speaker 1: of space, including photons. Photons in Einstein's gravity can be 460 00:24:57,200 --> 00:25:01,000 Speaker 1: bent because they follow the curvature of space, not because 461 00:25:01,000 --> 00:25:04,040 Speaker 1: of this Newtonian force between masses. So if Hodan that 462 00:25:04,119 --> 00:25:06,480 Speaker 1: goes past the event horizon is trapped by the structure 463 00:25:06,520 --> 00:25:09,760 Speaker 1: of space itself, because every path forward now takes it 464 00:25:09,840 --> 00:25:12,680 Speaker 1: towards the center of the black hole. And that's where 465 00:25:12,680 --> 00:25:15,640 Speaker 1: this apparent mental paradox comes from that you mentioned earlier. 466 00:25:16,160 --> 00:25:19,680 Speaker 1: If a black hole traps everything, if everything is encapsulated 467 00:25:19,720 --> 00:25:22,240 Speaker 1: inside the black hole because of the structure of space, 468 00:25:22,600 --> 00:25:24,600 Speaker 1: then how is it possible for us to even know 469 00:25:24,720 --> 00:25:28,600 Speaker 1: about it? How's that gravitational information leaving this trash can 470 00:25:28,760 --> 00:25:29,520 Speaker 1: of space time. 471 00:25:29,800 --> 00:25:33,120 Speaker 2: I do want to hear about sort of this idea 472 00:25:33,840 --> 00:25:38,680 Speaker 2: of information not being able to escape a black hole, 473 00:25:38,720 --> 00:25:41,720 Speaker 2: because that just it sounds weird, right to like say 474 00:25:41,760 --> 00:25:46,119 Speaker 2: like information is trapped somewhere, because when we think about information, 475 00:25:46,560 --> 00:25:49,000 Speaker 2: you know, it's like, wait, so I can't use Google 476 00:25:49,119 --> 00:25:51,560 Speaker 2: in a black hole? What does that mean? But maybe 477 00:25:51,560 --> 00:25:54,680 Speaker 2: we should take a quick break before we do that, 478 00:25:55,600 --> 00:25:59,240 Speaker 2: digest the curvature of the space. See, I need food 479 00:25:59,280 --> 00:26:02,720 Speaker 2: metaphors for me to learn and then when we get back, 480 00:26:02,800 --> 00:26:05,560 Speaker 2: I would love to learn more about what it really 481 00:26:05,680 --> 00:26:22,399 Speaker 2: means to say that information cannot escape. All right, So 482 00:26:22,760 --> 00:26:26,040 Speaker 2: I think I'm starting to get a grasp on this 483 00:26:26,200 --> 00:26:31,160 Speaker 2: idea of gravity being sort of a curvature of space, 484 00:26:32,200 --> 00:26:36,160 Speaker 2: not a force. But I do want to hear more 485 00:26:36,280 --> 00:26:42,600 Speaker 2: about what it means when information can't escape a black hole, because, like, again, 486 00:26:42,680 --> 00:26:45,320 Speaker 2: when I think of information, I'm like, well, I'm looking 487 00:26:45,400 --> 00:26:49,280 Speaker 2: on Wikipedia about how ants can stick the dismount. What 488 00:26:49,320 --> 00:26:52,280 Speaker 2: does it mean when information cannot escape a black hole? 489 00:26:52,440 --> 00:26:54,240 Speaker 1: Well, fortunately, if you fall into a black hole, you 490 00:26:54,320 --> 00:26:58,560 Speaker 1: can still access Wikipedia because information can go into Wikipedia. 491 00:26:58,640 --> 00:27:02,000 Speaker 1: You can't request specific page because we can't hear from you, 492 00:27:02,080 --> 00:27:04,199 Speaker 1: but we can send you information. We could just like 493 00:27:04,640 --> 00:27:07,600 Speaker 1: randomly send you Wikipedia pages even after you've. 494 00:27:07,440 --> 00:27:11,000 Speaker 2: Fallen in I would like to get some Netflix and 495 00:27:11,040 --> 00:27:13,760 Speaker 2: stuff if I'm in a black hole, because it seems 496 00:27:14,200 --> 00:27:16,919 Speaker 2: if I'm still alive, it seems really kind of like 497 00:27:17,800 --> 00:27:19,560 Speaker 2: a lot of time I'm going to spend in there. 498 00:27:19,600 --> 00:27:21,280 Speaker 2: I need some entertainment, you know what. 499 00:27:21,320 --> 00:27:24,439 Speaker 1: I think maybe nobody does. What everybody should do is 500 00:27:24,520 --> 00:27:26,880 Speaker 1: prepare their Like, if I fall into a black hole, 501 00:27:26,920 --> 00:27:29,440 Speaker 1: what Netflix shows. Should you beam to me the way 502 00:27:29,480 --> 00:27:32,840 Speaker 1: people like you know, prepare a will other end of 503 00:27:32,880 --> 00:27:35,240 Speaker 1: life information? Like, I'd like to know this about people 504 00:27:35,280 --> 00:27:37,359 Speaker 1: in my life, so I know what to beam to them, right. 505 00:27:37,400 --> 00:27:41,119 Speaker 2: Yeah, exactly, I need to start working on a list. 506 00:27:41,480 --> 00:27:44,840 Speaker 2: But yeah, so information can't escape a black hole? What 507 00:27:45,000 --> 00:27:48,000 Speaker 2: is going on there? And what do we mean by information? 508 00:27:48,119 --> 00:27:50,639 Speaker 1: Really? Yeah? Great? And here's where we need to zoom 509 00:27:50,680 --> 00:27:53,520 Speaker 1: back down again to the particle level when we talk 510 00:27:53,560 --> 00:27:56,760 Speaker 1: about information, Like, imagine that you are inside the black 511 00:27:56,800 --> 00:27:59,680 Speaker 1: hole and you want to request a Wikipedia page about something, 512 00:28:00,000 --> 00:28:02,959 Speaker 1: make a Sioux fla, and you want a recipe or something. 513 00:28:03,119 --> 00:28:05,600 Speaker 1: In order to request that information, you have to send 514 00:28:05,640 --> 00:28:09,280 Speaker 1: something physical outside of the black hole. The way information 515 00:28:09,440 --> 00:28:12,280 Speaker 1: works is that it's transmitted physically. The way you are 516 00:28:12,320 --> 00:28:16,760 Speaker 1: hearing this podcast right now is wiggles in electrons or 517 00:28:16,840 --> 00:28:20,719 Speaker 1: photons being beamed across the Earth. All information is transmitted 518 00:28:20,960 --> 00:28:23,439 Speaker 1: as particles or some kind of a wave. And so 519 00:28:23,600 --> 00:28:26,720 Speaker 1: if particles cannot escape a black hole, then you cannot 520 00:28:26,720 --> 00:28:29,320 Speaker 1: send information outside the black hole because to send that 521 00:28:29,359 --> 00:28:34,120 Speaker 1: information would require sending something physical, a photon, an electron, 522 00:28:34,280 --> 00:28:37,960 Speaker 1: something outside of the black hole. So that's where this 523 00:28:38,040 --> 00:28:40,720 Speaker 1: idea comes from that no information can leave a black 524 00:28:40,760 --> 00:28:43,719 Speaker 1: hole because no thing can leave a black hole, and 525 00:28:43,800 --> 00:28:47,280 Speaker 1: you need things to transmit information. Information in the end 526 00:28:47,480 --> 00:28:48,280 Speaker 1: is physical. 527 00:28:48,480 --> 00:28:51,000 Speaker 2: So I cannot order a pizza from a black hole, 528 00:28:51,120 --> 00:28:53,440 Speaker 2: which seems a little scary. 529 00:28:53,760 --> 00:28:56,080 Speaker 1: So get your pizza order in before you fall into 530 00:28:56,120 --> 00:28:57,760 Speaker 1: the black hole. That's the key. It's just a little 531 00:28:57,760 --> 00:28:58,360 Speaker 1: bit of planning. 532 00:28:58,600 --> 00:29:00,920 Speaker 2: I am writing it in sort of my black hole 533 00:29:01,200 --> 00:29:05,160 Speaker 2: instruction list, that please send pizza into the black hole. 534 00:29:05,200 --> 00:29:07,600 Speaker 2: Should I go in there. 535 00:29:07,560 --> 00:29:09,800 Speaker 1: I think you should ask for spaghetti, actually, because everything 536 00:29:09,840 --> 00:29:12,040 Speaker 1: we send in is getting spaghettified anyway, so you might 537 00:29:12,080 --> 00:29:13,320 Speaker 1: as well start with spaghetti. 538 00:29:13,600 --> 00:29:15,840 Speaker 2: You are what you eat, especially in a black hole, 539 00:29:15,880 --> 00:29:16,920 Speaker 2: if you're eating spaghetti. 540 00:29:17,080 --> 00:29:20,320 Speaker 1: But let's get specific about what we mean by information, 541 00:29:20,400 --> 00:29:22,640 Speaker 1: because this is the crux of the issue. This is 542 00:29:22,680 --> 00:29:25,200 Speaker 1: how we're going to understand later why you can feel 543 00:29:25,240 --> 00:29:27,960 Speaker 1: gravity from outside a black hole, but you can't order 544 00:29:28,040 --> 00:29:30,640 Speaker 1: pizza from within the black hole. And what we mean 545 00:29:30,720 --> 00:29:34,840 Speaker 1: by information is sort of like an update, a change 546 00:29:34,960 --> 00:29:38,920 Speaker 1: of state, so you're communicating something is different, Like if 547 00:29:39,000 --> 00:29:41,000 Speaker 1: Katie and I are across the room from each other, 548 00:29:41,120 --> 00:29:44,240 Speaker 1: she can send me information by like shooting photons at 549 00:29:44,280 --> 00:29:47,520 Speaker 1: me right. For example, if she doesn't shoot any photons 550 00:29:47,560 --> 00:29:50,000 Speaker 1: at me, I can assume like, Okay, Katie's still there. 551 00:29:50,040 --> 00:29:52,120 Speaker 1: I haven't heard from her in a while. But if 552 00:29:52,160 --> 00:29:54,640 Speaker 1: I want any new information from Katie, if you want 553 00:29:54,640 --> 00:29:58,240 Speaker 1: any updates on her situation, she wants to warn me 554 00:29:58,280 --> 00:30:00,320 Speaker 1: about something, or tell me about the pizza she wants, 555 00:30:00,400 --> 00:30:02,880 Speaker 1: or change her list of Netflix shows she wants to watch, 556 00:30:03,040 --> 00:30:05,440 Speaker 1: then she would need to send me some information, some 557 00:30:05,480 --> 00:30:08,640 Speaker 1: electrons or some photons. So information is sort of like 558 00:30:08,680 --> 00:30:10,600 Speaker 1: an update. It's like something new that. 559 00:30:10,560 --> 00:30:13,840 Speaker 2: You're learning, right, So it kind of makes me think 560 00:30:13,880 --> 00:30:19,280 Speaker 2: of like, uh, you know, the basis behind things like computers. 561 00:30:19,840 --> 00:30:23,400 Speaker 2: You have to have little on off things and you know, 562 00:30:23,480 --> 00:30:26,120 Speaker 2: this is a system inside of a computer like a 563 00:30:26,240 --> 00:30:30,240 Speaker 2: zero one an on or and off, and that change 564 00:30:30,640 --> 00:30:34,200 Speaker 2: from off to on is a sort of bit of 565 00:30:34,320 --> 00:30:38,280 Speaker 2: information that can be expanded into of course, the complexity 566 00:30:38,360 --> 00:30:41,040 Speaker 2: of computer. It's the same thing I think with you know, 567 00:30:41,440 --> 00:30:44,960 Speaker 2: in terms of the brain, where you have either a 568 00:30:45,400 --> 00:30:47,960 Speaker 2: synapse has fired or it has not, there's a little 569 00:30:48,040 --> 00:30:51,800 Speaker 2: more complexity because it's it's a large biological process. So 570 00:30:51,920 --> 00:30:55,400 Speaker 2: you have, you know, some states that are somewhat in between, 571 00:30:55,440 --> 00:30:59,320 Speaker 2: you know. But essentially it's like this on off state. 572 00:30:59,480 --> 00:31:02,080 Speaker 2: You need to you be able to clearly have an 573 00:31:02,200 --> 00:31:05,680 Speaker 2: off position and an on position and have that reach 574 00:31:05,840 --> 00:31:09,040 Speaker 2: from one you know, like be able you know, even 575 00:31:09,080 --> 00:31:14,520 Speaker 2: with like say a neuron, you are shooting neurotransmitters from 576 00:31:14,560 --> 00:31:17,200 Speaker 2: one end of a neuron to the other end of 577 00:31:17,280 --> 00:31:20,680 Speaker 2: another neuron. So it's like it's very much like in 578 00:31:20,800 --> 00:31:24,680 Speaker 2: our day to day life we experience this concept of 579 00:31:24,800 --> 00:31:26,280 Speaker 2: information exactly. 580 00:31:26,280 --> 00:31:28,720 Speaker 1: And so you could also think about information from the 581 00:31:28,760 --> 00:31:32,520 Speaker 1: sense of like affecting the future. Information is something that 582 00:31:32,640 --> 00:31:35,760 Speaker 1: somebody in the future can use to make a decision. 583 00:31:35,920 --> 00:31:38,280 Speaker 1: Like if I could tell you what the Powerball winning 584 00:31:38,360 --> 00:31:41,840 Speaker 1: numbers are, you can be a billionaire tomorrow because you 585 00:31:41,840 --> 00:31:44,280 Speaker 1: would know exactly what numbers to put in. So if 586 00:31:44,320 --> 00:31:46,720 Speaker 1: I have information, I can send it to somebody and 587 00:31:46,760 --> 00:31:48,800 Speaker 1: they can use that to make a decision. It can 588 00:31:48,880 --> 00:31:51,880 Speaker 1: like change the future if I am sending them information. 589 00:31:52,560 --> 00:31:55,360 Speaker 1: This is closely connected with another concept we've talked about 590 00:31:55,400 --> 00:31:58,520 Speaker 1: on the podcast a lot, which is this causal link, right, 591 00:31:58,600 --> 00:32:02,760 Speaker 1: like causes and effects how they can be connected. Because 592 00:32:02,760 --> 00:32:05,880 Speaker 1: there's already a limit to how you can affect the 593 00:32:05,880 --> 00:32:09,360 Speaker 1: future in the universe. Like, for example, I can't change 594 00:32:09,440 --> 00:32:13,360 Speaker 1: the future in Andromeda tomorrow. Andromeda is so many light 595 00:32:13,440 --> 00:32:16,640 Speaker 1: years away that any information I send to Andromeda will 596 00:32:16,640 --> 00:32:20,239 Speaker 1: not arrive for millions of years, and so nothing I 597 00:32:20,360 --> 00:32:24,760 Speaker 1: do today can get any information to Andromeda by tomorrow. 598 00:32:24,880 --> 00:32:28,720 Speaker 2: So we cannot get a pizza from or to Andromeda 599 00:32:29,440 --> 00:32:30,280 Speaker 2: anytime soon. 600 00:32:31,040 --> 00:32:34,480 Speaker 1: That's right. We can't even tell Andromeda about what kind 601 00:32:34,480 --> 00:32:37,520 Speaker 1: of pizzas they should order, which in principle could travel 602 00:32:37,560 --> 00:32:41,320 Speaker 1: at the maximum speed of information, which is light speed. 603 00:32:41,840 --> 00:32:44,440 Speaker 1: And so we have this concept we call a light cone, 604 00:32:44,920 --> 00:32:48,080 Speaker 1: which tells you where in the universe your information can reach. 605 00:32:48,560 --> 00:32:51,520 Speaker 1: You can send signals, you can turn on flashing lights, 606 00:32:51,760 --> 00:32:54,560 Speaker 1: but people outside your light cone will not see it, 607 00:32:55,120 --> 00:32:57,600 Speaker 1: and so the light cone expands as time goes on. 608 00:32:57,960 --> 00:33:01,600 Speaker 1: You send a flare. Now that information propagates through the 609 00:33:01,720 --> 00:33:04,760 Speaker 1: universe and eventually will reach the edges of the universe. 610 00:33:04,840 --> 00:33:08,360 Speaker 1: Your light cone is expanding in time from every moment. 611 00:33:08,640 --> 00:33:11,120 Speaker 1: But there is a limitation there, right, There are already 612 00:33:11,200 --> 00:33:15,400 Speaker 1: parts of the universe that your information cannot reach at 613 00:33:15,400 --> 00:33:18,600 Speaker 1: an arbitrary time, So there's a limit to the information. 614 00:33:18,840 --> 00:33:21,840 Speaker 1: You can't send any information to people outside your light cone. 615 00:33:21,960 --> 00:33:24,320 Speaker 2: I don't know if this is a pretty rudimentary question, 616 00:33:24,400 --> 00:33:30,080 Speaker 2: but from Earth, right, we can't see every star in existence, 617 00:33:30,200 --> 00:33:33,400 Speaker 2: can we? Or are we able to see, like get 618 00:33:33,560 --> 00:33:37,080 Speaker 2: light information from every star in existence? From Earth? 619 00:33:37,240 --> 00:33:39,640 Speaker 1: We can't because the universe is not old enough. Right, 620 00:33:39,640 --> 00:33:42,320 Speaker 1: The universe is finite age, So there are some stars 621 00:33:42,360 --> 00:33:44,840 Speaker 1: that are so distant that light from them has not 622 00:33:45,000 --> 00:33:47,720 Speaker 1: had time to arrive here. Plus you've got a factor 623 00:33:47,760 --> 00:33:50,520 Speaker 1: in the expansion or the universe. It gets much more complicated. 624 00:33:50,720 --> 00:33:53,480 Speaker 1: But no, there definitely starts who have sent photons towards 625 00:33:53,560 --> 00:33:55,400 Speaker 1: us but have not yet arrived. 626 00:33:55,520 --> 00:33:59,520 Speaker 2: So it is a matter of timing where because like 627 00:33:59,560 --> 00:34:02,440 Speaker 2: all this stars that we see right now, like that 628 00:34:02,600 --> 00:34:06,920 Speaker 2: information is really old, that light information that we're receiving now, 629 00:34:07,080 --> 00:34:07,840 Speaker 2: that's exactly right. 630 00:34:07,920 --> 00:34:10,160 Speaker 1: Yeah, that information is very old, and it's a matter 631 00:34:10,239 --> 00:34:13,280 Speaker 1: of timing. And if space was simple, space was always flat, 632 00:34:13,320 --> 00:34:16,000 Speaker 1: if there was no curvature, photons always traveled in a 633 00:34:16,040 --> 00:34:18,160 Speaker 1: straight direction and at the speed of light, then the 634 00:34:18,200 --> 00:34:21,239 Speaker 1: only limit to information would be timing. But the curvature 635 00:34:21,280 --> 00:34:24,799 Speaker 1: of space changes things. And in curved space, your light 636 00:34:24,880 --> 00:34:27,440 Speaker 1: cone is not a simple cone. It gets bent, it 637 00:34:27,440 --> 00:34:30,320 Speaker 1: gets distorted. Near a black hole or anywhere where space 638 00:34:30,360 --> 00:34:33,440 Speaker 1: is curved. Your light cone gets twisted because it changes 639 00:34:33,760 --> 00:34:36,680 Speaker 1: where photons go. Right, you send out a flash of light. 640 00:34:36,960 --> 00:34:39,200 Speaker 1: Now they're going in some directions, not in other directions. 641 00:34:39,200 --> 00:34:41,439 Speaker 1: They get twisted, they get bent. Once you pass over 642 00:34:41,480 --> 00:34:44,560 Speaker 1: the event horizon, your light cone is now just pointed 643 00:34:44,640 --> 00:34:47,919 Speaker 1: towards the center of the singularity. Any flare you set off, 644 00:34:48,280 --> 00:34:51,600 Speaker 1: all photons are going to end up going towards the singularity. 645 00:34:51,920 --> 00:34:54,320 Speaker 1: So your light cone is now sort of trapped behind 646 00:34:54,520 --> 00:34:57,439 Speaker 1: this barrier. And that's what we mean when we say 647 00:34:57,520 --> 00:35:00,760 Speaker 1: information cannot escape a black hole. I mean that nobody 648 00:35:00,760 --> 00:35:03,840 Speaker 1: passed that threshold can ever send you a photon that 649 00:35:04,000 --> 00:35:04,919 Speaker 1: arrives to you. 650 00:35:05,080 --> 00:35:08,640 Speaker 2: If a photon approaches a black hole but doesn't pass 651 00:35:08,760 --> 00:35:11,959 Speaker 2: the event horizon, can its light cones still get bent, 652 00:35:12,400 --> 00:35:14,799 Speaker 2: but not fall into the black hole. 653 00:35:14,880 --> 00:35:17,120 Speaker 1: Oh yeah. In fact, there's a region near black holes 654 00:35:17,160 --> 00:35:20,440 Speaker 1: where photons can orbit. They can get trapped and forever 655 00:35:20,560 --> 00:35:23,600 Speaker 1: loop around a black hole, which is pretty cool, or 656 00:35:23,640 --> 00:35:26,160 Speaker 1: they can do other weird things like pass around the 657 00:35:26,200 --> 00:35:28,160 Speaker 1: backside of a black hole and then come back. So 658 00:35:28,200 --> 00:35:30,120 Speaker 1: you can shoot it like a laser beam just above 659 00:35:30,120 --> 00:35:32,520 Speaker 1: a black hole and kind of come around the backside 660 00:35:32,560 --> 00:35:35,319 Speaker 1: and zap you in the eyeball from below the black hole. 661 00:35:36,000 --> 00:35:37,600 Speaker 2: It's like a laser boomerang. 662 00:35:37,760 --> 00:35:40,320 Speaker 1: So the key thing to understand there is that information 663 00:35:40,480 --> 00:35:44,360 Speaker 1: is about changes of state, how things change, getting updates 664 00:35:44,400 --> 00:35:47,520 Speaker 1: about what's going on, decisions that are made, new facts 665 00:35:47,520 --> 00:35:51,040 Speaker 1: that arise. Information is about changes of state. 666 00:35:51,320 --> 00:35:56,879 Speaker 2: So with gravity, Now, I thought that we had talked 667 00:35:56,920 --> 00:36:00,480 Speaker 2: about a previous episode about how with gravity there is 668 00:36:00,520 --> 00:36:04,799 Speaker 2: a phenomenon known as gravitational waves, which would indicate that 669 00:36:04,840 --> 00:36:09,080 Speaker 2: gravity can change. Right, you can have changes in gravity. 670 00:36:09,239 --> 00:36:12,840 Speaker 2: So why would it be considered that gravity is not 671 00:36:13,320 --> 00:36:14,680 Speaker 2: a form of information. 672 00:36:15,160 --> 00:36:19,080 Speaker 1: Yes, great example, So gravitational wave is a great example 673 00:36:19,160 --> 00:36:22,960 Speaker 1: of gravity changing. Right. We talked about gravity in terms 674 00:36:23,040 --> 00:36:25,560 Speaker 1: of the curvature of space. So imagine space has some 675 00:36:25,760 --> 00:36:28,520 Speaker 1: curvature because of the arrangements of masses in it. So 676 00:36:28,560 --> 00:36:30,760 Speaker 1: space has that curvature, and that curvature is just fixed, 677 00:36:30,800 --> 00:36:34,080 Speaker 1: it's constant. Right. Now, take one of those masses, the 678 00:36:34,120 --> 00:36:37,239 Speaker 1: Sun maybe, and wiggle it. You put your finger on it, 679 00:36:37,280 --> 00:36:39,479 Speaker 1: you shake it back and forth. If you wiggle the Sun, 680 00:36:39,520 --> 00:36:42,440 Speaker 1: you're changing where the mass is. You're changing how space 681 00:36:42,600 --> 00:36:44,520 Speaker 1: is bent. So what's happening to there is the curvature 682 00:36:44,560 --> 00:36:46,239 Speaker 1: is changing. You're moving the Sun to the left, and 683 00:36:46,280 --> 00:36:47,799 Speaker 1: you're moving it to the right, and you're moving it 684 00:36:47,800 --> 00:36:49,439 Speaker 1: to the left again, you're moving it to the right, 685 00:36:49,560 --> 00:36:53,640 Speaker 1: and that's information and that information propagates out at the 686 00:36:53,680 --> 00:36:56,200 Speaker 1: speed of light. And so if you're far away from 687 00:36:56,200 --> 00:36:58,759 Speaker 1: the Sun when somebody's wiggling it, you don't feel those 688 00:36:58,880 --> 00:37:02,439 Speaker 1: changes instantly. It takes time for that information to get 689 00:37:02,440 --> 00:37:05,880 Speaker 1: to you. So Katie wiggles the Sun. Eight minutes later, 690 00:37:06,040 --> 00:37:09,080 Speaker 1: I feel the gravity on Earth shaking a little bit. 691 00:37:09,400 --> 00:37:11,400 Speaker 1: It gets stronger, it gets weaker, it gets stronger, it 692 00:37:11,400 --> 00:37:15,879 Speaker 1: gets weaker. That's a gravitational wave. That's information moving through 693 00:37:15,880 --> 00:37:18,840 Speaker 1: the gravitational field. So I think that's sort of a 694 00:37:18,840 --> 00:37:21,080 Speaker 1: long answer to your question, which is can you send 695 00:37:21,120 --> 00:37:23,600 Speaker 1: information through gravity? And the answer is yes, And that's 696 00:37:23,600 --> 00:37:27,560 Speaker 1: what gravitational waves are. There's information sent through the gravitational field. 697 00:37:27,880 --> 00:37:31,360 Speaker 1: The crucial thing is that that's all about a change 698 00:37:31,440 --> 00:37:35,200 Speaker 1: in the gravitational field. There's no information being propagated when 699 00:37:35,200 --> 00:37:37,879 Speaker 1: the sun is static. The field is not changing. There's 700 00:37:37,880 --> 00:37:40,640 Speaker 1: no information there. When you move the sun, when you've 701 00:37:40,680 --> 00:37:43,239 Speaker 1: wiggled it, that's sending information. 702 00:37:43,800 --> 00:37:49,920 Speaker 2: So Earth has gravity, obviously, but when the Earth moves, 703 00:37:50,320 --> 00:37:53,760 Speaker 2: you're getting some change in gravity, and so you're getting 704 00:37:53,840 --> 00:37:57,600 Speaker 2: gravitational waves. And so that change of the Earth moving 705 00:37:58,440 --> 00:38:03,360 Speaker 2: is sending out information in terms of the change in gravity. 706 00:38:03,560 --> 00:38:06,480 Speaker 1: Absolutely, And when the Earth orbits the Sun, because it's 707 00:38:06,480 --> 00:38:10,320 Speaker 1: effectively moving through space and changing the Earth's gravitational field, 708 00:38:10,600 --> 00:38:14,680 Speaker 1: we are generating gravitational waves. Our orbit around the Sun 709 00:38:14,800 --> 00:38:18,840 Speaker 1: generates gravitational waves, and it actually contributes to the decay 710 00:38:18,960 --> 00:38:23,040 Speaker 1: of Earth's orbit because gravitational waves contain energy, so we're 711 00:38:23,160 --> 00:38:26,040 Speaker 1: radiating away some of our energy every time we go 712 00:38:26,080 --> 00:38:27,800 Speaker 1: around the Sun. You just did an episode about this 713 00:38:27,840 --> 00:38:30,160 Speaker 1: about how stable is the Earth's orbit, and it turns 714 00:38:30,160 --> 00:38:32,880 Speaker 1: out that's a very very small effect in terms of 715 00:38:32,920 --> 00:38:35,719 Speaker 1: the stability of the Earth's orbit. But in principle, yes, 716 00:38:36,040 --> 00:38:39,480 Speaker 1: we are generating gravitational waves which contain information, and if 717 00:38:39,520 --> 00:38:42,760 Speaker 1: you had a sensitive enough gravitational wave detector, you could 718 00:38:42,760 --> 00:38:45,520 Speaker 1: pick up those wiggles in space time that are telling 719 00:38:45,600 --> 00:38:47,600 Speaker 1: you about how the Earth is moving. 720 00:38:47,960 --> 00:38:52,279 Speaker 2: So gravity can convey information. It can be considered a 721 00:38:52,320 --> 00:38:55,880 Speaker 2: form of information if it is a change in the gravity. 722 00:38:56,200 --> 00:38:59,680 Speaker 2: So with a black hole, why aren't we seeing a 723 00:38:59,760 --> 00:39:02,719 Speaker 2: chain in gravity, because I would assume if we're not 724 00:39:02,760 --> 00:39:06,719 Speaker 2: getting gravitational information from a black hole, that would mean 725 00:39:07,120 --> 00:39:10,560 Speaker 2: that there is not a change in the gravity of 726 00:39:10,600 --> 00:39:11,279 Speaker 2: a black hole. 727 00:39:11,520 --> 00:39:13,359 Speaker 1: Yes, exactly, and so now I think we have all 728 00:39:13,400 --> 00:39:15,880 Speaker 1: the pieces in place to try to answer this question, 729 00:39:16,400 --> 00:39:19,240 Speaker 1: which is a black hole does of course have gravity, 730 00:39:19,400 --> 00:39:22,640 Speaker 1: and you can feel its gravity from a distance. You 731 00:39:22,719 --> 00:39:24,759 Speaker 1: are a light year from a black hole, you will 732 00:39:24,800 --> 00:39:29,120 Speaker 1: feel its gravity. But what you can't feel are changes 733 00:39:29,160 --> 00:39:32,400 Speaker 1: to its gravity. So if there's something going on inside 734 00:39:32,480 --> 00:39:35,720 Speaker 1: the event horizon, Katie's in there and she's doing a dance, 735 00:39:36,120 --> 00:39:39,280 Speaker 1: or she's rearranging her living room or whatever, you can't 736 00:39:39,320 --> 00:39:42,800 Speaker 1: get that kind of information. If you change the configuration 737 00:39:43,000 --> 00:39:46,440 Speaker 1: of the masses inside the black hole, in principle, that 738 00:39:46,520 --> 00:39:50,760 Speaker 1: generates gravitational waves, but those are trapped within the event horizon. 739 00:39:51,200 --> 00:39:54,000 Speaker 1: So nothing that's happening within the event horizon is generating 740 00:39:54,080 --> 00:39:57,960 Speaker 1: any gravitational information that's escaping. All you're feeling is the 741 00:39:58,000 --> 00:40:01,319 Speaker 1: static field of the black hole, the one that was 742 00:40:01,360 --> 00:40:04,120 Speaker 1: created when it was formed. So you have a black 743 00:40:04,120 --> 00:40:07,279 Speaker 1: hole and it has a static gravitational field. Nothing is 744 00:40:07,360 --> 00:40:11,360 Speaker 1: changing and anything that happens inside the event horizon is 745 00:40:11,440 --> 00:40:14,520 Speaker 1: going to generate gravitational waves, but they don't leave the 746 00:40:14,600 --> 00:40:18,360 Speaker 1: black hole. So you can have gravity outside the black 747 00:40:18,360 --> 00:40:21,799 Speaker 1: hole from its original formation without knowing what's going on 748 00:40:21,920 --> 00:40:26,000 Speaker 1: later inside the event horizon, without getting any information from 749 00:40:26,120 --> 00:40:29,600 Speaker 1: inside the event horizon. The only information you have is 750 00:40:29,640 --> 00:40:32,480 Speaker 1: the existence of the black hole from when it was created, 751 00:40:32,600 --> 00:40:35,839 Speaker 1: which is not information from inside the event horizon. Another 752 00:40:35,880 --> 00:40:38,359 Speaker 1: way to think about it is you create the black hole, 753 00:40:38,560 --> 00:40:42,680 Speaker 1: you're then freezing that gravitational field. Nothing that happens pas 754 00:40:42,719 --> 00:40:46,440 Speaker 1: the event horizon can then change the gravitational field outside 755 00:40:46,520 --> 00:40:49,040 Speaker 1: the black hole. Now, that's all if the black hole 756 00:40:49,120 --> 00:40:52,080 Speaker 1: is not moving and so it has a static, unchanging 757 00:40:52,239 --> 00:40:55,279 Speaker 1: gravitational field. If you wiggle a black hole or if 758 00:40:55,320 --> 00:40:59,280 Speaker 1: black holes merge, that motion creates ripples in the gravitational field, 759 00:40:59,400 --> 00:41:01,760 Speaker 1: just like a d when the Sun or the Earth moves. 760 00:41:01,880 --> 00:41:05,400 Speaker 1: But that's motion of the event horizon. It's not information 761 00:41:05,520 --> 00:41:09,120 Speaker 1: from inside the event horizon about what's going on within it. 762 00:41:09,239 --> 00:41:11,400 Speaker 1: Another way to say it is that from the outside 763 00:41:11,480 --> 00:41:14,440 Speaker 1: you can see if the black hole is wiggling, but 764 00:41:14,520 --> 00:41:17,520 Speaker 1: that's not information from inside the event horizon. You can't 765 00:41:17,560 --> 00:41:20,680 Speaker 1: tell if things inside are wiggling, only if the whole 766 00:41:20,760 --> 00:41:21,800 Speaker 1: thing is moving. 767 00:41:22,000 --> 00:41:25,120 Speaker 2: I mean that's interesting because it's like, I suspect this 768 00:41:25,200 --> 00:41:27,680 Speaker 2: might be the wrong way to conceptualize it, but in 769 00:41:27,719 --> 00:41:31,040 Speaker 2: my head, I'm thinking of sort of a Russian nesting doll, 770 00:41:31,400 --> 00:41:34,560 Speaker 2: where it's like the black hole is the main one, 771 00:41:34,840 --> 00:41:39,439 Speaker 2: the main sort of gravitational field, and inside you could 772 00:41:39,440 --> 00:41:42,440 Speaker 2: have like the little tiny doll dancing around doing stuff, 773 00:41:42,440 --> 00:41:45,360 Speaker 2: but none of that is reaching outside of this nesting 774 00:41:45,640 --> 00:41:50,239 Speaker 2: doll because like the bigger one is essentially this like 775 00:41:50,360 --> 00:41:56,719 Speaker 2: static large gravitational field, and nothing is getting outside of it. 776 00:41:56,800 --> 00:41:58,640 Speaker 1: Yeah, I think that's a great way to think about it. 777 00:41:58,960 --> 00:42:01,920 Speaker 1: Another useful thing to think through is how a black 778 00:42:01,920 --> 00:42:04,719 Speaker 1: hole gets formed, the moment in which a black hole 779 00:42:04,840 --> 00:42:07,399 Speaker 1: is created. I think that can really help people crystallize 780 00:42:07,520 --> 00:42:10,560 Speaker 1: how that information is propagated through the universe and why 781 00:42:10,719 --> 00:42:14,440 Speaker 1: no more information is ever sent out from that object. 782 00:42:14,520 --> 00:42:17,600 Speaker 2: All right, let's take a quick break as I mentally 783 00:42:17,680 --> 00:42:21,240 Speaker 2: prepare my mind to be blown. I'll lay out a tarp, 784 00:42:21,480 --> 00:42:24,240 Speaker 2: and then when we get back, please tell me how 785 00:42:24,360 --> 00:42:40,480 Speaker 2: a black hole is created. All right, So I'm officially 786 00:42:40,560 --> 00:42:45,960 Speaker 2: ready for my brain to explode from the information of 787 00:42:46,400 --> 00:42:48,520 Speaker 2: how a black hole is formed. 788 00:42:48,640 --> 00:42:49,919 Speaker 1: So all you have to do to form a black 789 00:42:49,960 --> 00:42:53,400 Speaker 1: hole is just order enough pizzas. Really, that's all it takes. Okay, 790 00:42:55,120 --> 00:42:56,799 Speaker 1: So we know that there are black holes out there 791 00:42:56,800 --> 00:42:59,560 Speaker 1: in the universe and that they are created, right, they're 792 00:42:59,560 --> 00:43:02,080 Speaker 1: a black holes that have not existed since the beginning 793 00:43:02,080 --> 00:43:04,680 Speaker 1: of the universe. So there has to be some moment 794 00:43:04,760 --> 00:43:06,880 Speaker 1: when there wasn't a black hole and when there is 795 00:43:06,920 --> 00:43:09,319 Speaker 1: a black hole. And I think the thinking through that 796 00:43:09,440 --> 00:43:12,719 Speaker 1: moment really can help people understand what we're talking about 797 00:43:12,719 --> 00:43:14,319 Speaker 1: when we say a black hole, what it means for 798 00:43:14,360 --> 00:43:16,759 Speaker 1: information to be trapped within it. And so there's lots 799 00:43:16,800 --> 00:43:18,440 Speaker 1: of ways that a black hole can be made in 800 00:43:18,480 --> 00:43:20,480 Speaker 1: the universe, But let's try to think about like the 801 00:43:20,520 --> 00:43:24,480 Speaker 1: simplest possible configuration and in general relativity, one very frequently 802 00:43:24,560 --> 00:43:27,560 Speaker 1: used example is like a sphere of rocks. Imagine you 803 00:43:27,600 --> 00:43:30,000 Speaker 1: have like tiny little bits of dust or pebbles, and 804 00:43:30,000 --> 00:43:33,040 Speaker 1: you have a perfectly symmetrical sphere of it. Okay, and 805 00:43:33,080 --> 00:43:35,520 Speaker 1: now gravity is pulling it and so it's collapsing. It's 806 00:43:35,560 --> 00:43:38,080 Speaker 1: going to pull towards itself and get denser and denser 807 00:43:38,120 --> 00:43:39,879 Speaker 1: and denser. Now, how do you make a black hole. 808 00:43:39,920 --> 00:43:42,200 Speaker 1: You make a black hole by having enough stuff in 809 00:43:42,239 --> 00:43:45,920 Speaker 1: a small enough space. It's all about the density of matter. 810 00:43:46,280 --> 00:43:47,920 Speaker 1: You could take the Earth and squeeze it into a 811 00:43:47,960 --> 00:43:49,960 Speaker 1: peanut to get a black hole. You could take the 812 00:43:50,000 --> 00:43:53,040 Speaker 1: Sun and squeeze it into like a three kilometer wide object. 813 00:43:53,120 --> 00:43:55,080 Speaker 1: To get a black hole. You could take a huge 814 00:43:55,080 --> 00:43:57,279 Speaker 1: blob of stuff and squeeze it. The point is to 815 00:43:57,280 --> 00:43:59,840 Speaker 1: get high enough density. So now you have this hollow 816 00:44:00,120 --> 00:44:03,319 Speaker 1: fear of pebbles. Right, everything's like the same distance from 817 00:44:03,360 --> 00:44:06,799 Speaker 1: the center, and it's collapsing slowly. At some point it's 818 00:44:06,840 --> 00:44:09,160 Speaker 1: going to be dense enough to pass this threshold and 819 00:44:09,200 --> 00:44:11,240 Speaker 1: become a black hole. It's going to be a moment 820 00:44:11,280 --> 00:44:14,400 Speaker 1: before it passes that threshold where it's just like a 821 00:44:14,480 --> 00:44:16,880 Speaker 1: sphere of stuff that has gravity, and then a moment 822 00:44:17,000 --> 00:44:20,120 Speaker 1: after passes that threshold, now it's a black hole. 823 00:44:20,440 --> 00:44:25,600 Speaker 2: How does the incredible density cause Essentially, what I'm imagining 824 00:44:25,719 --> 00:44:30,440 Speaker 2: is like pinching the curvature of space such that everything 825 00:44:30,520 --> 00:44:34,800 Speaker 2: is going towards that point, Like, how does density cause 826 00:44:34,880 --> 00:44:35,640 Speaker 2: that to happen? 827 00:44:35,840 --> 00:44:38,040 Speaker 1: We talked about how gravity is actually just the curvature 828 00:44:38,040 --> 00:44:40,399 Speaker 1: of space. We didn't talk about how you make that 829 00:44:40,440 --> 00:44:43,640 Speaker 1: curvature why bits of space are curved here or not 830 00:44:43,760 --> 00:44:47,320 Speaker 1: curved there. So the missing piece is density energy density. 831 00:44:47,760 --> 00:44:49,560 Speaker 1: If you have a chunk of space with a lot 832 00:44:49,600 --> 00:44:52,960 Speaker 1: of energy in it, be it mass or photons or 833 00:44:53,000 --> 00:44:56,600 Speaker 1: any kind of energy, then that space gets curved. So 834 00:44:56,640 --> 00:45:00,840 Speaker 1: the simplest version of general relativity is mass tells space 835 00:45:00,880 --> 00:45:04,200 Speaker 1: how to bend. Space tells mass how to move, and 836 00:45:04,239 --> 00:45:06,759 Speaker 1: so it's that first bit that mass tells space how 837 00:45:06,800 --> 00:45:09,479 Speaker 1: to bend. The more energy density, usually in the form 838 00:45:09,520 --> 00:45:12,040 Speaker 1: of mass, that you pile into a little chunk of space, 839 00:45:12,120 --> 00:45:16,000 Speaker 1: the more curvature you get. When you cross past some threshold, 840 00:45:16,320 --> 00:45:19,600 Speaker 1: then you have so much curvature that nothing can escape anymore. 841 00:45:19,680 --> 00:45:21,640 Speaker 1: So that's the moment you become a black hole. So 842 00:45:21,719 --> 00:45:24,200 Speaker 1: you take this sphere of dust again, it's a hollow sphere. 843 00:45:24,200 --> 00:45:26,640 Speaker 1: It's not filled on the center. If it's really really big, 844 00:45:26,680 --> 00:45:28,359 Speaker 1: then you have a lot of empty space. Also, you're 845 00:45:28,360 --> 00:45:31,239 Speaker 1: including density is very very low, you don't have a 846 00:45:31,280 --> 00:45:34,760 Speaker 1: black hole. As you collapse it, the radius gets smaller 847 00:45:34,760 --> 00:45:37,000 Speaker 1: and smaller. All the bits get closer and closer together. 848 00:45:37,120 --> 00:45:40,800 Speaker 1: Eventually you pass over the short siled radius, the radius 849 00:45:40,800 --> 00:45:43,839 Speaker 1: of an event horizon for that amount of stuff, and 850 00:45:43,880 --> 00:45:46,759 Speaker 1: then you have enough density that there's enough curvature that 851 00:45:46,800 --> 00:45:47,839 Speaker 1: you've got a black hole. 852 00:45:48,120 --> 00:45:51,800 Speaker 2: So mass which we can observe is sort of tied 853 00:45:51,880 --> 00:45:57,280 Speaker 2: to this hidden world of gravity which we cannot see. 854 00:45:57,880 --> 00:46:00,359 Speaker 2: We can feel the effects of, but we cannot see 855 00:46:00,360 --> 00:46:03,520 Speaker 2: the curvature of space. But that curvature of space has 856 00:46:03,640 --> 00:46:09,400 Speaker 2: direct connections to all the mass that we can directly observe. 857 00:46:09,719 --> 00:46:13,279 Speaker 1: Yeah, that's exactly right. And remember that's not just mass. 858 00:46:13,400 --> 00:46:16,759 Speaker 1: Right in Newton's physics, it's just mass, but in Einstein's 859 00:46:16,760 --> 00:46:20,320 Speaker 1: relativity it's energy density. That's why photons and other massless 860 00:46:20,360 --> 00:46:23,440 Speaker 1: things can actually contribute to the curvature of space. You 861 00:46:23,480 --> 00:46:26,720 Speaker 1: can actually just make a black hole by overlapping powerful 862 00:46:26,800 --> 00:46:30,920 Speaker 1: laser beams. Pure photons can make a black hole in theory. 863 00:46:31,200 --> 00:46:33,239 Speaker 2: Okay, how do you know that, Daniel, or are you 864 00:46:33,320 --> 00:46:35,680 Speaker 2: working on that? Are you doing that? 865 00:46:35,960 --> 00:46:38,560 Speaker 1: I can either deny nor confirm those experiments. 866 00:46:38,719 --> 00:46:44,719 Speaker 2: That's incredible that just through light, if you cram enough 867 00:46:44,840 --> 00:46:48,160 Speaker 2: light into a small enough area, not only are you 868 00:46:48,200 --> 00:46:50,719 Speaker 2: going to like blow out your retinas, you're going to 869 00:46:50,800 --> 00:46:52,000 Speaker 2: create a black hole. 870 00:46:52,320 --> 00:46:55,000 Speaker 1: So now let's go back to our collapsing sphere of 871 00:46:55,040 --> 00:46:58,960 Speaker 1: pebbles or dust or rocks or whatever. What happens when 872 00:46:58,960 --> 00:47:01,840 Speaker 1: it creates a black hole? What is changing in space 873 00:47:02,000 --> 00:47:04,319 Speaker 1: the moment before it creates a black hole? What do 874 00:47:04,400 --> 00:47:06,200 Speaker 1: you have? What you have gravity? 875 00:47:06,400 --> 00:47:06,560 Speaker 2: Right? 876 00:47:06,920 --> 00:47:08,759 Speaker 1: If somebody is going to shoot a photon or a 877 00:47:08,760 --> 00:47:11,719 Speaker 1: particle near it, it's going to be bending space and 878 00:47:11,760 --> 00:47:13,920 Speaker 1: it's going to affect the path of that stuff. Right, 879 00:47:13,920 --> 00:47:16,919 Speaker 1: You're going to feel the effective force of gravity from 880 00:47:16,960 --> 00:47:19,440 Speaker 1: this sphere of rocks, right, because it has mass, it's 881 00:47:19,480 --> 00:47:22,279 Speaker 1: curving space. It's giving you that effect. No big deal, 882 00:47:22,320 --> 00:47:25,400 Speaker 1: no surprise there. What happens when it crosses that threshold 883 00:47:25,440 --> 00:47:29,200 Speaker 1: and becomes a black hole? Well, nothing changes from that 884 00:47:29,280 --> 00:47:32,440 Speaker 1: point of view, right, because the mass hasn't changed, the 885 00:47:32,520 --> 00:47:35,239 Speaker 1: overall energy hasn't changed. So if you're in the outside, 886 00:47:35,760 --> 00:47:40,080 Speaker 1: when this sphere becomes a black hole, nothing changes gravitationally, 887 00:47:40,120 --> 00:47:43,480 Speaker 1: the gravitational field is still the same. And that makes sense, right. 888 00:47:43,560 --> 00:47:46,200 Speaker 1: It's not like the gravity disappears when the thing becomes 889 00:47:46,200 --> 00:47:49,440 Speaker 1: a black hole. It changes from a big sphere of 890 00:47:49,520 --> 00:47:51,440 Speaker 1: dust to a black hole. But if it has the 891 00:47:51,440 --> 00:47:54,160 Speaker 1: same mass, it has the same gravity as before it 892 00:47:54,239 --> 00:47:55,160 Speaker 1: became a black hole. 893 00:47:55,320 --> 00:47:59,480 Speaker 2: Okay, so you have this amount of gravity that just 894 00:47:59,600 --> 00:48:02,760 Speaker 2: before sure the black hole is created, and then once 895 00:48:02,880 --> 00:48:06,920 Speaker 2: the black hole happens, that gravity is the same. So 896 00:48:07,000 --> 00:48:10,520 Speaker 2: can you not add any more gravity to a black hole? 897 00:48:10,560 --> 00:48:13,400 Speaker 2: Like you cannot, Like say, you put more stuff into 898 00:48:13,440 --> 00:48:16,680 Speaker 2: a black hole, you put more particles into that black hole, 899 00:48:16,719 --> 00:48:19,560 Speaker 2: you shoot some lasers. There's no more gravity that you 900 00:48:19,600 --> 00:48:20,239 Speaker 2: can add to that. 901 00:48:20,440 --> 00:48:23,040 Speaker 1: That's a great question, actually really illustrates this point very nicely. 902 00:48:23,360 --> 00:48:26,120 Speaker 1: Absolutely you can. Right, if you shoot a laser into 903 00:48:26,120 --> 00:48:27,759 Speaker 1: the black hole, or you throw a more mast in 904 00:48:27,800 --> 00:48:30,560 Speaker 1: the black hole, you are going to increase its gravity, 905 00:48:30,960 --> 00:48:34,160 Speaker 1: and that information will propagate outwards. Right, you add to 906 00:48:34,200 --> 00:48:36,200 Speaker 1: a black hole, you add to its gravity. You can 907 00:48:36,280 --> 00:48:39,760 Speaker 1: feel more gravity now somewhere else. That information will propagate 908 00:48:39,760 --> 00:48:43,720 Speaker 1: outwards as a gravitational waves, a change in the gravitational 909 00:48:43,800 --> 00:48:47,400 Speaker 1: field of the black hole. But that's external, right, that's 910 00:48:47,440 --> 00:48:50,760 Speaker 1: not information coming from within the black hole. That stuff 911 00:48:50,760 --> 00:48:53,000 Speaker 1: you're adding from the outside. If you have just a 912 00:48:53,000 --> 00:48:55,560 Speaker 1: black hole and it's collapsed and you're not changing its 913 00:48:55,600 --> 00:48:58,960 Speaker 1: gravitational field, then what does it mean for information to 914 00:48:59,040 --> 00:49:01,880 Speaker 1: not be able to aesc if you're still feeling its gravity? 915 00:49:02,280 --> 00:49:04,560 Speaker 1: What that means, is that anything that's happening to that 916 00:49:04,719 --> 00:49:08,280 Speaker 1: stuff that fell into the black hole, you can't tell. Basically, 917 00:49:08,320 --> 00:49:11,759 Speaker 1: the gravitation field is just frozen from that stuff. If 918 00:49:11,800 --> 00:49:14,040 Speaker 1: that stuff goes in and does a funny dance or 919 00:49:14,080 --> 00:49:18,160 Speaker 1: becomes a singularity, or becomes a quantum fuzzball, or does whatever, 920 00:49:18,760 --> 00:49:21,240 Speaker 1: you can't ever see. It can't ever tell you anything 921 00:49:21,280 --> 00:49:24,240 Speaker 1: about it. You can't ever learn anything about the configuration 922 00:49:24,480 --> 00:49:27,720 Speaker 1: of the mass within the event horizon. The gravitational field 923 00:49:27,760 --> 00:49:31,360 Speaker 1: of that stuff still exists, but it's now frozen in time. 924 00:49:31,719 --> 00:49:34,279 Speaker 1: You will get no more updates. If you take that 925 00:49:34,320 --> 00:49:37,080 Speaker 1: stuff inside the black hole and wiggle it around, generating 926 00:49:37,120 --> 00:49:40,439 Speaker 1: a bunch of gravitational waves within the event horizon, those 927 00:49:40,480 --> 00:49:44,040 Speaker 1: waves are trapped within the event horizon. Outside you will 928 00:49:44,080 --> 00:49:47,399 Speaker 1: still see the same exact gravitational field. And that's why 929 00:49:47,440 --> 00:49:50,600 Speaker 1: we made the distinction earlier about information being about updates, 930 00:49:51,000 --> 00:49:53,880 Speaker 1: because that gravitational field can be static. There's no information 931 00:49:54,000 --> 00:49:57,120 Speaker 1: escaping from within the black hole. It's just sort of 932 00:49:57,160 --> 00:50:00,279 Speaker 1: like think about the event horizon itself as having that 933 00:50:00,360 --> 00:50:03,840 Speaker 1: gravity or the last information you got about this stuff 934 00:50:03,920 --> 00:50:06,640 Speaker 1: was just before it falls into the black hole. It's 935 00:50:06,800 --> 00:50:11,359 Speaker 1: that gravitational field. You're feeling no updates, no information means 936 00:50:11,360 --> 00:50:13,640 Speaker 1: that gravitational field is effectively frozen. 937 00:50:13,880 --> 00:50:16,640 Speaker 2: So would it be fair to say that we can 938 00:50:17,120 --> 00:50:21,839 Speaker 2: get information from the existence of a black hole, and 939 00:50:21,920 --> 00:50:26,000 Speaker 2: we can get information by shooting information into a black 940 00:50:26,040 --> 00:50:30,239 Speaker 2: hole and then that sort of changing the characteristics of 941 00:50:30,239 --> 00:50:33,600 Speaker 2: the black hole. But we cannot get any information from 942 00:50:33,640 --> 00:50:37,240 Speaker 2: anything that is already inside of the black hole. 943 00:50:37,160 --> 00:50:41,640 Speaker 1: Exactly, because that would require communicating something physically. Right, if 944 00:50:41,680 --> 00:50:44,200 Speaker 1: you wanted to send information from within the black hole, 945 00:50:44,520 --> 00:50:47,560 Speaker 1: you'd need to like take a bowling ball and wiggle it, 946 00:50:47,640 --> 00:50:50,759 Speaker 1: which would generate gravitational waves. But I can't feel that 947 00:50:50,800 --> 00:50:53,320 Speaker 1: from the outside. What I feel is the gravitational field 948 00:50:53,360 --> 00:50:55,799 Speaker 1: of the stuff the moment it became a black hole. 949 00:50:55,880 --> 00:50:58,400 Speaker 1: That's when it got frozen in time. All the gravitational 950 00:50:58,440 --> 00:51:01,759 Speaker 1: waves generated inside of it, an updates to that gravitational 951 00:51:01,800 --> 00:51:04,239 Speaker 1: field are now trapped the same way that like if 952 00:51:04,239 --> 00:51:06,800 Speaker 1: you shoot photons or if you shoot electrons. Right, I remember, 953 00:51:06,840 --> 00:51:10,400 Speaker 1: information is physical. None of that physical information. 954 00:51:10,000 --> 00:51:12,640 Speaker 2: Can leave all right, But now hear me out. If 955 00:51:12,640 --> 00:51:15,800 Speaker 2: you had a really long string and you were sitting 956 00:51:15,840 --> 00:51:19,719 Speaker 2: here on Earth with a dixie cup attached to your end, 957 00:51:20,280 --> 00:51:22,719 Speaker 2: and I'm all the way in a black hole with 958 00:51:22,840 --> 00:51:25,799 Speaker 2: that string and a dixie cup on my end. No, 959 00:51:26,080 --> 00:51:30,680 Speaker 2: I cannot communicate any information to you, even if somehow 960 00:51:30,719 --> 00:51:34,200 Speaker 2: that string was strong enough to survive the black hole. 961 00:51:34,400 --> 00:51:34,600 Speaker 7: Right. 962 00:51:34,640 --> 00:51:37,359 Speaker 1: Well, there, you're creating a new paradox because there is 963 00:51:37,440 --> 00:51:40,279 Speaker 1: no string strong enough to survive the black hole. Right 964 00:51:40,560 --> 00:51:43,440 Speaker 1: Because as you zoom in microscopically to that string, it's 965 00:51:43,480 --> 00:51:47,239 Speaker 1: really just a bunch of particles transmitting information to each 966 00:51:47,280 --> 00:51:51,920 Speaker 1: other using electrons or using photons, and those photons cannot 967 00:51:52,040 --> 00:51:54,960 Speaker 1: escape the black hole. But you know, electrons and photons 968 00:51:55,000 --> 00:51:57,960 Speaker 1: are a great way to think about this information. Also, 969 00:51:58,560 --> 00:52:00,480 Speaker 1: like say you take an electron and you just have 970 00:52:00,480 --> 00:52:03,719 Speaker 1: an electron in space. Electron has an electric field, right, 971 00:52:04,000 --> 00:52:06,600 Speaker 1: a static field all through space. It gets stronger as 972 00:52:06,600 --> 00:52:09,759 Speaker 1: you're closer to it, and weaker as you get further away. Now, 973 00:52:09,760 --> 00:52:12,400 Speaker 1: what happens if you shake that electron. You shake that electron, 974 00:52:12,520 --> 00:52:15,960 Speaker 1: you're changing the electric field. And that change is a photon. 975 00:52:16,000 --> 00:52:19,960 Speaker 1: It's physical information. It's changing the field of the electron 976 00:52:20,120 --> 00:52:24,759 Speaker 1: that is transmitting the information. The static, frozen constant existence 977 00:52:24,840 --> 00:52:27,920 Speaker 1: of the field is not information, which is why stationary 978 00:52:27,960 --> 00:52:31,239 Speaker 1: electrons don't generate photons in the same way that like, 979 00:52:31,280 --> 00:52:34,320 Speaker 1: the existence of the black hole and its gravitational field 980 00:52:34,680 --> 00:52:37,080 Speaker 1: is sort of like old information from before it became 981 00:52:37,120 --> 00:52:40,040 Speaker 1: a black hole when it was created. Any new information 982 00:52:40,239 --> 00:52:43,520 Speaker 1: created within it by moving the stuff inside is not 983 00:52:43,560 --> 00:52:47,640 Speaker 1: going to be transmitted. So information gravitational waves or photons 984 00:52:47,680 --> 00:52:50,719 Speaker 1: really are about changes in the field, not about the 985 00:52:50,760 --> 00:52:52,480 Speaker 1: existence of the field itself. 986 00:52:52,800 --> 00:52:56,440 Speaker 2: So in my string and cup analogy, of course the 987 00:52:56,440 --> 00:53:00,200 Speaker 2: string would not survive. But you know, with a hypothetical string, 988 00:53:00,280 --> 00:53:02,479 Speaker 2: I could be shaken it, I could be talking into 989 00:53:02,480 --> 00:53:06,719 Speaker 2: the Dixie cup. But as soon as that information, you know, 990 00:53:07,000 --> 00:53:10,920 Speaker 2: is basically the part of the hypothetical string outside of 991 00:53:10,960 --> 00:53:15,560 Speaker 2: the event horizon is getting nothing from the string inside. 992 00:53:15,960 --> 00:53:18,080 Speaker 2: From within the event horizon. 993 00:53:17,840 --> 00:53:20,080 Speaker 1: Exactly, your string is going to be dangling towards the 994 00:53:20,120 --> 00:53:22,600 Speaker 1: center of the black hole. All the information you create 995 00:53:22,960 --> 00:53:25,319 Speaker 1: is going to get funneled towards the center of the 996 00:53:25,320 --> 00:53:25,920 Speaker 1: black hole. 997 00:53:26,239 --> 00:53:30,080 Speaker 2: Wow. Well, I'm gonna really emphasize that if I am 998 00:53:30,080 --> 00:53:35,120 Speaker 2: in a black hole. Pepperoni pizza is good. Also, do 999 00:53:35,160 --> 00:53:40,239 Speaker 2: a nice carbonara, just keep them common for eternity. I 1000 00:53:40,280 --> 00:53:42,440 Speaker 2: suppose that sounds good. 1001 00:53:42,480 --> 00:53:44,919 Speaker 1: It's good to get that information now before you fall 1002 00:53:44,920 --> 00:53:45,759 Speaker 1: into the black hole. 1003 00:53:45,960 --> 00:53:49,280 Speaker 2: Right could happen any day. We are sponsored by black 1004 00:53:49,280 --> 00:53:53,400 Speaker 2: Hole Insurance. Make sure to set up your affares before 1005 00:53:53,440 --> 00:53:56,120 Speaker 2: you get sucked into a black hole, or should I say, 1006 00:53:56,200 --> 00:53:59,400 Speaker 2: not sucked into a black hole, but follow the curvature 1007 00:53:59,440 --> 00:54:01,520 Speaker 2: of space into a black hole. 1008 00:54:01,600 --> 00:54:05,040 Speaker 1: So you should think about black holes as barriers to information. 1009 00:54:05,200 --> 00:54:07,200 Speaker 1: But I hope this podcast has helped you understand a 1010 00:54:07,200 --> 00:54:10,759 Speaker 1: little bit more what that means, what information really is, 1011 00:54:11,239 --> 00:54:15,200 Speaker 1: because what's inside a black hole can affect what's outside 1012 00:54:15,200 --> 00:54:18,080 Speaker 1: a black hole. The creation of the black hole itself 1013 00:54:18,360 --> 00:54:21,640 Speaker 1: affects space time near the black hole. But sort of 1014 00:54:21,640 --> 00:54:24,280 Speaker 1: in a simplified way. We can only know a few 1015 00:54:24,360 --> 00:54:26,200 Speaker 1: things about the black hole. We can know it's mass, 1016 00:54:26,200 --> 00:54:28,200 Speaker 1: we can know it's charge, we can know its spin. 1017 00:54:28,640 --> 00:54:31,560 Speaker 1: Anything else that happens within the black hole can't change 1018 00:54:31,560 --> 00:54:35,400 Speaker 1: what's happening on the outside. The changes behind the barrier, 1019 00:54:35,680 --> 00:54:38,439 Speaker 1: wiggles and rearrangements of the stuff within the black hole 1020 00:54:38,520 --> 00:54:42,279 Speaker 1: can't influence things on the outside. So I think the 1021 00:54:42,320 --> 00:54:45,640 Speaker 1: crucial concept there is that information really is about changing 1022 00:54:45,680 --> 00:54:49,160 Speaker 1: the internal arrangements. That's what you're prevented from knowing not 1023 00:54:49,239 --> 00:54:51,319 Speaker 1: the existence of the black hole, but what's going on 1024 00:54:51,600 --> 00:54:52,359 Speaker 1: inside of it. 1025 00:54:52,600 --> 00:54:56,360 Speaker 2: So I could be inside of the black hole, drunk 1026 00:54:56,360 --> 00:55:00,800 Speaker 2: off of Martini's, standing on the black hole jack table 1027 00:55:01,120 --> 00:55:05,359 Speaker 2: and screaming out the lyrics to a Katie Perry song, 1028 00:55:05,600 --> 00:55:06,959 Speaker 2: and no one would ever know. 1029 00:55:07,160 --> 00:55:09,800 Speaker 1: Only people within the black hole and closer to the center. 1030 00:55:10,480 --> 00:55:13,480 Speaker 1: But hopefully what happens inside a black hole stays inside 1031 00:55:13,480 --> 00:55:14,040 Speaker 1: a black hole. 1032 00:55:14,200 --> 00:55:18,160 Speaker 2: Yeah, well that's good information to know, because I know 1033 00:55:18,360 --> 00:55:21,080 Speaker 2: now where I'm going to do my next Vegas trip 1034 00:55:21,960 --> 00:55:23,520 Speaker 2: and it's not in Vegas. 1035 00:55:23,280 --> 00:55:25,640 Speaker 1: All right. Well, I want everybody out there to keep 1036 00:55:25,719 --> 00:55:28,960 Speaker 1: thinking like a physicist, trying to bring pieces of understanding 1037 00:55:29,000 --> 00:55:32,040 Speaker 1: together and weave them into a deeper, more profound model 1038 00:55:32,080 --> 00:55:34,879 Speaker 1: in your head about how the universe works, how these 1039 00:55:34,920 --> 00:55:38,520 Speaker 1: things all interact, and when things don't jive together, when 1040 00:55:38,560 --> 00:55:40,239 Speaker 1: they don't make sense to you, or when you feel 1041 00:55:40,239 --> 00:55:42,960 Speaker 1: like you have hit upon a contradition right to us, 1042 00:55:43,080 --> 00:55:46,800 Speaker 1: we will help you figure it out. Questions at Danielanjorge 1043 00:55:46,920 --> 00:55:50,320 Speaker 1: dot com. Our goal is to turn everybody into a physicist. 1044 00:55:50,680 --> 00:55:53,560 Speaker 2: You and your army of physicists. What are you planning? 1045 00:55:53,760 --> 00:55:56,640 Speaker 1: I can neither confirm nor deny our plan. Thanks very 1046 00:55:56,719 --> 00:55:59,360 Speaker 1: much Katie for joining me on this path towards the 1047 00:55:59,400 --> 00:56:03,040 Speaker 1: center of understanding following the curvature of explanations. 1048 00:56:03,280 --> 00:56:05,680 Speaker 2: Thank you for all the information. I'm glad we're not 1049 00:56:05,800 --> 00:56:08,680 Speaker 2: broadcasting from a black hole where nobody would. 1050 00:56:08,560 --> 00:56:11,359 Speaker 1: Know, and thanks everybody for listening. Tune in next time. 1051 00:56:12,320 --> 00:56:14,280 Speaker 4: Hey, this is Joege from the podcast and I'm super 1052 00:56:14,280 --> 00:56:17,320 Speaker 4: excited to announce that my new book, Oliver's Great Big Universe, 1053 00:56:17,480 --> 00:56:20,400 Speaker 4: is out now. It has humor, cartoons, a fun story, 1054 00:56:20,440 --> 00:56:23,160 Speaker 4: and lots of awesome signs, and it's perfect for kids 1055 00:56:23,160 --> 00:56:25,120 Speaker 4: that are into science, but also kids who are not 1056 00:56:25,200 --> 00:56:28,080 Speaker 4: into science yet. There are chapters about black holes the 1057 00:56:28,120 --> 00:56:30,680 Speaker 4: planet's dark energy, but at the heart of it is 1058 00:56:30,680 --> 00:56:33,160 Speaker 4: a story about friendship and figuring out your place in 1059 00:56:33,200 --> 00:56:34,839 Speaker 4: the world, so please check it out. You can get 1060 00:56:34,840 --> 00:56:38,319 Speaker 4: it in stores, online, and at Great Big Universe dot net. 1061 00:56:46,239 --> 00:56:49,040 Speaker 1: Thanks for listening, and remember that Daniel and Jorge explain 1062 00:56:49,120 --> 00:56:53,120 Speaker 1: the universe is a productive of iHeartRadio. For more podcasts 1063 00:56:53,120 --> 00:56:57,040 Speaker 1: from my Heart Radio, visit the iHeartRadio app, Apple Podcasts, 1064 00:56:57,200 --> 00:57:10,680 Speaker 1: or wherever you listen to your favorite