WEBVTT - Listener Questions #28 0:00:07.840 --> 0:00:10.960 How can massless photons add to a black hole's might? 0:00:11.440 --> 0:00:14.280 Can you really make a singularity out of light? 0:00:15.080 --> 0:00:19.560 Organs that come in twos include the long hand, kidney, foot, 0:00:19.600 --> 0:00:23.000 and eye? But why do I only have one of 0:00:23.079 --> 0:00:25.599 some things? And what's the plural of venus? 0:00:26.079 --> 0:00:30.640 Ain't I could drifting bubble universes collide to end our 0:00:30.720 --> 0:00:34.200 cosmic show my gravity in other dimensions? 0:00:34.280 --> 0:00:34.560 Ever? 0:00:34.800 --> 0:00:38.160 Let us know whatever questions keep you up at night. 0:00:38.400 --> 0:00:40.360 Daniel and Kelly's answers will make it right. 0:00:41.040 --> 0:00:44.440 Welcome to Daniel and Kelly's Extraordinary Universe. 0:00:44.880 --> 0:01:00.880 We've done twenty eight of these. Hello, Kelly, we or Smith. 0:01:01.120 --> 0:01:04.640 I study parasites and space and whatever it is that 0:01:04.720 --> 0:01:07.160 y'all ask me when you send us emails. 0:01:07.560 --> 0:01:08.479 Hi, I'm Daniel. 0:01:08.600 --> 0:01:11.280 I'm a particle physicist, and I've answered a lot of 0:01:11.360 --> 0:01:14.360 questions from listeners, but never any about ANI. 0:01:14.560 --> 0:01:17.800 Oh no, that's Daniel. You'd be taking my questions. I 0:01:17.840 --> 0:01:21.280 am the ANI experts in this group. Thank you very much. 0:01:21.720 --> 0:01:24.040 You stick to the black holes and I stick to 0:01:24.080 --> 0:01:25.319 the biology black holes. 0:01:25.400 --> 0:01:28.680 Isn't there an obvious connection exactly? Aren't black holes a 0:01:28.760 --> 0:01:30.400 sort of physics anus? 0:01:30.760 --> 0:01:31.160 Yeah? 0:01:31.240 --> 0:01:33.440 Yes, yes, And I of the universe. 0:01:34.080 --> 0:01:37.040 All right, you stick to the ani of the cosmos. 0:01:37.200 --> 0:01:39.120 I stick to the ani of the Earth. 0:01:39.480 --> 0:01:41.600 But wait now I'm realizing it. We have it all wrong, 0:01:41.640 --> 0:01:44.120 don't we. Black holes are more like mouths, and white 0:01:44.120 --> 0:01:47.360 holes would be more like anus'es. Why because things don't 0:01:47.400 --> 0:01:48.600 come out of black holes? 0:01:48.920 --> 0:01:51.760 Oh, they go in and things go out of white holes. 0:01:51.880 --> 0:01:54.720 Well, you know yet another instance where the physicists did 0:01:54.720 --> 0:01:56.680 a poor job of naming things. 0:01:56.800 --> 0:01:57.800 Yes, there you go again. 0:01:57.840 --> 0:01:59.320 It is hard to keep the inns in the out 0:01:59.440 --> 0:02:00.240 streets and time. 0:02:00.960 --> 0:02:04.559 Yes, okay, well we have started by going off track, 0:02:04.640 --> 0:02:07.760 so let's work on getting back on track. So we 0:02:07.920 --> 0:02:11.080 are very lucky to have an audience that has so 0:02:11.240 --> 0:02:15.200 many absolutely fascinating questions, and you all send them to us. 0:02:15.480 --> 0:02:18.040 You send them to us at Questions at danieland Kelly 0:02:18.080 --> 0:02:18.560 dot org. 0:02:18.680 --> 0:02:20.640 And it's our job to break down the ins and 0:02:20.680 --> 0:02:23.359 the outs of the universe, to explain to you how 0:02:23.400 --> 0:02:27.200 it all works, to inject the whole universe into your brain. 0:02:27.560 --> 0:02:29.680 And that's what we're going to do. On today's episode. 0:02:29.680 --> 0:02:32.600 We have three warrantful questions from listeners. People who are 0:02:32.880 --> 0:02:36.120 curious about the universe, people who've been listening and thinking 0:02:36.160 --> 0:02:39.160 and there's something that doesn't quite click in their minds. 0:02:39.440 --> 0:02:42.520 We want to make that click happen for you. So 0:02:42.600 --> 0:02:44.960 if you are sitting on a question something you've never 0:02:45.040 --> 0:02:48.680 really had satisfactory explained, please don't be shy. Write to 0:02:48.760 --> 0:02:52.639 us questions at danieland Kelly dot org. We really do 0:02:52.960 --> 0:02:54.359 right back to everybody. 0:02:54.720 --> 0:02:58.840 Daniel worries back to everybody within a day. I am 0:02:58.880 --> 0:03:01.600 not quite as punk as Daniel. You'll get an answer 0:03:01.680 --> 0:03:04.799 from me in less than a week, for sure. But yeah, 0:03:04.800 --> 0:03:07.120 we write back to everybody. Some of the questions even 0:03:07.240 --> 0:03:08.000 end up on the show. 0:03:08.360 --> 0:03:10.960 I promise you that email address is not a black hole. 0:03:11.120 --> 0:03:13.240 It's more like a white hole because answers come out 0:03:13.240 --> 0:03:13.440 of it. 0:03:13.560 --> 0:03:15.720 That's right, that's right, and we are going to stretch 0:03:15.760 --> 0:03:18.360 this metaphor as far as we can, and so stick 0:03:18.360 --> 0:03:19.760 with us till the end of the show to see 0:03:19.760 --> 0:03:22.520 where we go with it. So let's start with our 0:03:22.560 --> 0:03:25.600 first question with Stephen from British Columbia. 0:03:26.160 --> 0:03:29.280 Hi, Daniel and Kelly, it's Stephen from BC Canada again 0:03:29.320 --> 0:03:32.720 with another question about our universe. In one of your 0:03:32.760 --> 0:03:35.800 past episodes, you glaze over a fact that photons can 0:03:35.840 --> 0:03:39.720 collapse into tiny black holes. My question today is about 0:03:39.760 --> 0:03:42.760 those tiny black holes. What is really going on inside 0:03:42.800 --> 0:03:45.760 a tiny black hole? How can something with no mass 0:03:46.080 --> 0:03:48.520 be able to collapse, never mind collapse into one of 0:03:48.560 --> 0:03:52.119 the most densest objects known in the universe. How can 0:03:52.120 --> 0:03:56.080 a black hole be tiny? Is there a singularity in them? 0:03:56.440 --> 0:03:57.000 How can a. 0:03:56.920 --> 0:04:01.320 Photon become a singularity inside a tiny black hole? I 0:04:01.440 --> 0:04:02.520 look forward to your answers. 0:04:02.840 --> 0:04:06.160 All right, I love this question because he's really thinking 0:04:06.200 --> 0:04:08.760 about the extremes. You know, we talk on this show 0:04:08.800 --> 0:04:12.240 about general relativity and energy density and stuff, and he's 0:04:12.280 --> 0:04:14.440 pushing it to the edge, which is what you have 0:04:14.520 --> 0:04:17.760 to do to really understand physics, to say, does this 0:04:17.800 --> 0:04:20.640 really connect in my brain? Do I understand every scenario? 0:04:20.880 --> 0:04:22.880 What about this? What about that? What about this other thing? 0:04:22.920 --> 0:04:23.599 What about this thing? 0:04:23.640 --> 0:04:24.120 I heard? 0:04:24.600 --> 0:04:28.279 So stevens out there doing physics in his mind. Congrats Steven, 0:04:28.600 --> 0:04:30.919 and I'm very excited to answer this question for you. 0:04:31.200 --> 0:04:34.440 And usually when we need to answer a physics question, 0:04:34.520 --> 0:04:37.160 it makes sense to go way back to the beginning 0:04:37.160 --> 0:04:40.080 to terms that you've heard since you were in kindergarten, 0:04:40.120 --> 0:04:42.520 because there's probably something basic about them that you don't 0:04:42.600 --> 0:04:48.560 quite understand. So Daniel, let's start with gravity. What remind 0:04:48.600 --> 0:04:49.480 us what is gravity? 0:04:50.120 --> 0:04:52.880 Yes, so Newton told us that gravity was a force 0:04:53.000 --> 0:04:56.680 between masses, but then Einstein revealed that it's actually the 0:04:56.800 --> 0:05:00.440 curvature of space time. That what we think think of 0:05:00.480 --> 0:05:03.359 its gravity is actually a pseudo force because we can't 0:05:03.440 --> 0:05:05.960 see the curvature of space time and its effect on 0:05:06.000 --> 0:05:09.560 the motion of objects, and because we can't see its effect, 0:05:09.640 --> 0:05:13.520 we attribute some mysterious force to doing that, sort of 0:05:13.560 --> 0:05:15.960 like if you're on a merry go Round and you 0:05:16.040 --> 0:05:18.480 throw a ball at somebody across the merry go round 0:05:18.480 --> 0:05:21.559 from you. It won't reach them, it'll curl to the side, 0:05:21.600 --> 0:05:23.839 and you'll think, why is that I didn't throw it 0:05:23.880 --> 0:05:26.279 to the side. So you'll come up with some pseudo 0:05:26.400 --> 0:05:29.039 force that accounts for the motion of that object, the 0:05:29.080 --> 0:05:31.920 acceleration of that object. In the same way, if you're 0:05:31.960 --> 0:05:33.880 standing on the surface of the Earth and you let 0:05:33.920 --> 0:05:37.080 go of an apple, it seems like something accelerates it 0:05:37.200 --> 0:05:40.159 towards the Earth. Really the apple is just following the 0:05:40.200 --> 0:05:43.600 curvature of space time, and you're the one accelerating against 0:05:43.720 --> 0:05:48.480 space time. So general relativity reformulates gravity as the curvature 0:05:48.560 --> 0:05:52.279 of space time that affects the motion of objects in 0:05:52.320 --> 0:05:54.479 a way that makes us think there's a force we 0:05:54.520 --> 0:05:55.480 would call gravity. 0:05:55.839 --> 0:05:57.560 Feels like that doesn't make any sense. 0:05:57.640 --> 0:05:59.599 But if Newton got it wrong, I don't feel so 0:05:59.720 --> 0:06:01.479 bad about getting it wrong too. 0:06:03.200 --> 0:06:05.279 And the crucial thing to understand in the context of 0:06:05.320 --> 0:06:08.920 this question is that the curvature of space time comes 0:06:08.960 --> 0:06:12.599 from energy density. We often think about it as mass 0:06:12.640 --> 0:06:16.039 tells space time how to bend, but it's not just mass. 0:06:16.279 --> 0:06:20.119 General relativity generalizes from beyond just mass to any kind 0:06:20.160 --> 0:06:23.599 of energy density. So, for example, if you have a 0:06:23.640 --> 0:06:27.520 bunch of photons that contribute to the energy density, and 0:06:27.560 --> 0:06:29.840 it can make it easier to have a black hole 0:06:29.920 --> 0:06:31.920 because photons have energy. 0:06:31.960 --> 0:06:37.000 Of course, okay, photons have energy. That is not a 0:06:37.040 --> 0:06:38.520 controversial statement, right. 0:06:38.520 --> 0:06:41.000 Yeah, exactly. And so like the canonical way to make 0:06:41.040 --> 0:06:43.400 a black hole is to take a big bunch of 0:06:43.440 --> 0:06:46.760 mass and squeeze it down into a tiny area. Like 0:06:46.839 --> 0:06:48.400 if you took the mass of the Earth and you 0:06:48.440 --> 0:06:50.839 squeezed it down to the volume of about a peanut, 0:06:51.360 --> 0:06:54.120 then it would become a black hole. So black holes 0:06:54.120 --> 0:06:57.279 are about energy density. Or if you took the Sun 0:06:57.320 --> 0:06:59.400 and you squeezed it down to a few kilometers, it 0:06:59.400 --> 0:07:01.960 would become a black hole. But you can also do 0:07:02.080 --> 0:07:05.760 that with just energy if you took enough light, if 0:07:05.760 --> 0:07:09.120 you focused a lot of photons in a tiny region, 0:07:09.720 --> 0:07:12.360 like you had a bunch of lasers overlapping where you 0:07:12.360 --> 0:07:14.840 had a big spherical mirror, so all the photons were 0:07:14.840 --> 0:07:17.720 in the same place. If you got enough energy density 0:07:17.800 --> 0:07:21.200 in one location at the same moment, it would curve 0:07:21.240 --> 0:07:23.559 space time enough to give you a black hole. 0:07:23.800 --> 0:07:26.240 Ooh, all right, So isn't there that there's a facility 0:07:26.240 --> 0:07:30.240 in California that's working on fusion and they're shooting a 0:07:30.240 --> 0:07:32.320 bunch of lasers at a little bit of fusion fuel. 0:07:32.760 --> 0:07:34.600 Are they going to kill us all with a black hole? 0:07:36.600 --> 0:07:40.120 That's the National Ignition Facility, and they're working on inertial 0:07:40.200 --> 0:07:43.560 confinement fusion. They take little pellets of fuel and they 0:07:43.680 --> 0:07:46.240 zap them with like one hundred and ninety six lasers. 0:07:46.240 --> 0:07:49.280 I think they are in order to implode it. Like 0:07:49.320 --> 0:07:52.600 the explosion of the shell creates an implosion which compresses 0:07:52.640 --> 0:07:55.880 the core and then ignites fusion for that little pellet. 0:07:56.040 --> 0:08:00.360 Super awesome, really cool project, but not nearly enough energy 0:08:00.400 --> 0:08:03.720 to create a black hole. In order to create this 0:08:03.840 --> 0:08:07.559 kind of energy, you'd need very high energy density, something 0:08:07.600 --> 0:08:10.960 like ten to the thirty five jewels in a region 0:08:11.120 --> 0:08:14.600 like ten to the negative fifteen meters across. You need 0:08:14.720 --> 0:08:17.320 like more energy than is put out by the Sun 0:08:17.880 --> 0:08:22.720 every second concentrated into a tiny little region. So it's 0:08:22.760 --> 0:08:26.960 a pretty big engineering problem. In principle, it's possible, which 0:08:27.000 --> 0:08:29.840 I think is the source of Stephen's question. In practice, 0:08:29.880 --> 0:08:31.840 you don't have to worry about black holes being made 0:08:31.920 --> 0:08:34.400 on the Earth by tiny, little dinky. 0:08:34.120 --> 0:08:35.080 Men made lasers. 0:08:35.320 --> 0:08:36.079 That's comforting. 0:08:39.280 --> 0:08:42.320 And so Steven's asking how can something with no mass 0:08:42.320 --> 0:08:44.920 collapse into one of the densest objects in the universe. 0:08:45.320 --> 0:08:48.960 So remember it's energy density that's collapsing here, that's creating 0:08:49.000 --> 0:08:51.840 that surface. And when you think about, like, well, what 0:08:52.000 --> 0:08:53.600 is that black hole made out of? Is there a 0:08:53.640 --> 0:08:56.640 singularity inside of it? Remember that the black hole is 0:08:56.640 --> 0:09:00.160 not made of the original matter that you put into it. 0:09:00.240 --> 0:09:02.880 Like if you drop a bunch of electrons into a 0:09:02.920 --> 0:09:05.480 tiny region to make a black hole, you don't know 0:09:05.640 --> 0:09:08.360 what the form of the matter is inside the black hole. 0:09:08.400 --> 0:09:10.560 It's not like there are a bunch of electrons still 0:09:10.600 --> 0:09:13.000 in there. The only thing you can know about the 0:09:13.040 --> 0:09:16.840 black hole is its total mass, which represents the energy 0:09:16.880 --> 0:09:20.600 that's captured inside of it, it's total charge, and it's spin. 0:09:21.240 --> 0:09:24.520 No original nature of the objects is preserved as far 0:09:24.559 --> 0:09:27.040 as we know, So if you make a black hole 0:09:27.120 --> 0:09:30.480 out of photons, it looks exactly the same as a 0:09:30.480 --> 0:09:33.440 black hole made out of neutrons or anything else that 0:09:33.480 --> 0:09:36.120 has the same total energy, charge and spin. 0:09:36.440 --> 0:09:38.400 So what happened to the electrons? Did they just get 0:09:38.440 --> 0:09:40.439 like smoohed into something unrecognizable? 0:09:40.679 --> 0:09:43.280 We don't know, right, Like general relativity tells us that 0:09:43.320 --> 0:09:45.959 they form a singularity, but that ignores all the quantum 0:09:45.960 --> 0:09:48.520 mechanical stuff we know about electrons and how they don't 0:09:48.559 --> 0:09:50.200 like to be on top of each other, and who 0:09:50.200 --> 0:09:52.240 knows what happens when you squish them down. Maybe there's 0:09:52.280 --> 0:09:55.720 things inside the electrons. Maybe the electron is a composite particle. 0:09:56.000 --> 0:09:58.680 When you smush them together that tightly, they break open 0:09:58.720 --> 0:10:01.679 and form some sort of plast of their intermediate states. 0:10:01.720 --> 0:10:03.880 Who knows, Right, we might finally know. 0:10:04.200 --> 0:10:06.480 We might finally know, but it would be hidden behind 0:10:06.480 --> 0:10:09.920 the event horizon. So the point is that, like, yes, 0:10:10.160 --> 0:10:12.920 general relativity predicts a singularity at the heart of a 0:10:12.920 --> 0:10:15.760 black hole made out of pure photons. But you can't 0:10:15.800 --> 0:10:19.040 really know, and the singularity itself is a prediction of 0:10:19.120 --> 0:10:22.680 general relativity, which ignores quantum mechanics anyway, so we think 0:10:22.679 --> 0:10:26.080 it's probably wrong. So the answer is, we have no 0:10:26.160 --> 0:10:29.360 idea what's going on inside that black hole. But in principle, 0:10:29.720 --> 0:10:32.160 that black hole is no different from a black hole 0:10:32.200 --> 0:10:35.360 you made out of electrons or cheese, or you know, 0:10:35.480 --> 0:10:37.400 the anuses of your lab. 0:10:37.240 --> 0:10:38.040 Rats or whatever. 0:10:38.160 --> 0:10:40.480 Oh great, would you pick lab rats? I feel like 0:10:40.520 --> 0:10:41.240 blue whales. 0:10:41.640 --> 0:10:43.920 Like there's if you're gonna make a black hole out 0:10:43.960 --> 0:10:46.000 of something, you gotta go go big or go home. 0:10:46.200 --> 0:10:48.520 Well, I mean, if you add up the biomass of 0:10:48.559 --> 0:10:51.200 the anuses of rats on Earth versus blue whales, what 0:10:51.240 --> 0:10:52.120 do you think is larger? 0:10:52.200 --> 0:10:52.560 Oh? 0:10:52.640 --> 0:10:53.640 Probably rats? 0:10:53.960 --> 0:10:57.360 Yeah, But what do you think the greatest anus biomass 0:10:57.400 --> 0:10:58.440 on the planet is. 0:10:58.880 --> 0:11:02.200 I bet it's could be humans, might be humans. 0:11:02.760 --> 0:11:04.640 I can't believe you're a biologist and you don't know 0:11:04.679 --> 0:11:06.560 the answer to this question off the top of your head. 0:11:06.760 --> 0:11:09.319 I'm a little embarrassed. I'm a little embarrassed. 0:11:10.800 --> 0:11:12.360 And you know, while it's out of the reach of 0:11:12.400 --> 0:11:17.079 our technology to create black holes out of photons. Currently 0:11:17.440 --> 0:11:19.480 in the future, you know, maybe if we become like 0:11:19.559 --> 0:11:22.520 a Kardashev type two civilization or whatever, we build a 0:11:22.559 --> 0:11:24.760 dice in sphere that captures all of the energy of 0:11:24.760 --> 0:11:27.319 the Sun. It is possible in the future we might 0:11:27.360 --> 0:11:30.040 be able to do it. Or maybe aliens are out 0:11:30.040 --> 0:11:32.440 there doing it right now and we could watch them 0:11:32.440 --> 0:11:34.760 doing it from afar. That could be the way that 0:11:34.800 --> 0:11:39.080 we discover the existence of aliens. Amazing, awesome, would be 0:11:39.080 --> 0:11:42.240 super cool. Please don't point those beams at us. But 0:11:42.320 --> 0:11:45.480 there's another way. It's possible that we could create these 0:11:45.480 --> 0:11:49.960 black holes. It's possible they could also exist naturally. Now 0:11:50.120 --> 0:11:54.080 there's no like natural huge laser focusing light beams. But 0:11:54.360 --> 0:11:57.600 in the very early universe, things were very hot and 0:11:57.880 --> 0:12:01.440 very dense, and there's the theory that black holes could 0:12:01.440 --> 0:12:05.360 have formed even before, like protons formed and electrons formed 0:12:05.840 --> 0:12:10.120 in that primordial soup, there was great energy density. Now, 0:12:10.120 --> 0:12:13.080 the whole universe didn't collapse quickly into a black hole 0:12:13.120 --> 0:12:16.480 because to get a black hole you need relative energy density. 0:12:16.520 --> 0:12:19.880 You need one region to be denser than another. So 0:12:19.960 --> 0:12:22.920 if the whole universe is filled with energy density, you 0:12:22.920 --> 0:12:25.360 don't get a black hole. But we also know there 0:12:25.360 --> 0:12:28.839 were little quantum fluctuations, some pockets that were more dense 0:12:28.880 --> 0:12:32.160 than others, and so this is the theory of primordial 0:12:32.240 --> 0:12:35.960 black holes, that maybe there were some regions that fluctuated 0:12:36.200 --> 0:12:39.600 enough to have enough energy density to create black holes 0:12:39.760 --> 0:12:43.000 before there was even particles made. Now we've never seen 0:12:43.040 --> 0:12:46.600 any of these, but in principle, back in the early universe, 0:12:46.840 --> 0:12:50.080 when it was radiation dominated, when most of the energy 0:12:50.120 --> 0:12:53.679 in the universe was in things like photons, then it's 0:12:53.720 --> 0:12:56.079 possible you had a pocketive space that had enough energy 0:12:56.120 --> 0:12:59.960 density just in photons to make a primordial black hole 0:13:00.360 --> 0:13:03.160 out of light. So it's possible it does exist in 0:13:03.200 --> 0:13:03.800 the universe. 0:13:05.640 --> 0:13:08.040 No, you're looking at me because it's my turn to 0:13:08.080 --> 0:13:10.360 say something. But I am still trying to figure out 0:13:10.360 --> 0:13:11.080 the anus thing. 0:13:11.679 --> 0:13:16.080 I'm so sorry. I mostly was listening, but I can't. 0:13:16.280 --> 0:13:19.640 Oh boy, all right, Well, then, since Kelly's since Kelly's 0:13:19.679 --> 0:13:23.400 been distracted, let's see if Steven's been paying attention. Steven, 0:13:23.480 --> 0:13:26.000 let us know if that answered your question or if 0:13:26.000 --> 0:13:28.400 you're just gonna file it away in the white hole 0:13:28.440 --> 0:13:29.480 in your mind. 0:13:31.040 --> 0:13:32.360 I don't know if that made any sense. 0:13:32.720 --> 0:13:33.360 I don't think so. 0:13:34.920 --> 0:13:38.640 Hi, Daniel and Kelly, it's Stephen from British Columbia. Again, 0:13:39.200 --> 0:13:42.200 thanks again for answering my question about what is going 0:13:42.200 --> 0:13:46.520 on inside tiny black holes. That explanation was super helpful. 0:14:06.520 --> 0:14:10.040 Okay, we're back and we're answering questions from listeners about 0:14:10.040 --> 0:14:12.800 black holes, about white holes, about ins and outs, about 0:14:12.800 --> 0:14:16.760 everything in the universe. We want to answer your questions 0:14:16.800 --> 0:14:20.160 because science is for everybody in the universe deserves to 0:14:20.200 --> 0:14:23.680 be understood. Up next, we have an amazing question about 0:14:23.720 --> 0:14:27.680 the human body, and it's symmetry and asymmetry from Jerry. 0:14:28.280 --> 0:14:30.400 Hey, Daniel and Kelly love the show. 0:14:30.560 --> 0:14:34.360 My left brain learns so much, but then my right 0:14:34.400 --> 0:14:38.440 brain has a question. How come there are two parts 0:14:38.480 --> 0:14:41.320 to a lot of our body. We have two eyes, 0:14:41.400 --> 0:14:44.560 we have two ears, We have two lungs, we have 0:14:44.600 --> 0:14:47.800 two kidneys, but those kidneys only lead to one bladder, 0:14:48.040 --> 0:14:50.400 and there's only one stomach, and there's only one spleen. 0:14:51.360 --> 0:14:54.240 You probably could live with one lung or one kidney, 0:14:55.000 --> 0:14:57.760 and maybe you could live with half a brain and 0:14:57.960 --> 0:15:00.720 be a politician. But why are we built this way? 0:15:00.720 --> 0:15:03.000 We have two of some things and only one of another. 0:15:03.320 --> 0:15:03.960 Love the show. 0:15:04.400 --> 0:15:06.960 Thanks, Well, I gotta be honest with you. 0:15:07.440 --> 0:15:10.160 I have had this question sitting on my stack for 0:15:10.280 --> 0:15:13.200 a few months because I just kind of wasn't really 0:15:13.280 --> 0:15:16.840 sure how how to answer this one, Like what is 0:15:16.880 --> 0:15:20.360 the answer why sometimes a human body just is the 0:15:20.400 --> 0:15:23.120 way it is? And uh and so all right, So 0:15:23.160 --> 0:15:24.520 here's what I came up with, because it is a 0:15:24.560 --> 0:15:26.840 great a good question. It's a great question. 0:15:27.000 --> 0:15:29.560 Well, let's start with the meta answer, like is there 0:15:29.600 --> 0:15:32.680 always an answer? What kind of answer do you think 0:15:32.760 --> 0:15:35.440 Jerry's looking for? Is he looking for an answer where 0:15:35.440 --> 0:15:38.920 it's like this works better than the opposite, Like there's 0:15:38.960 --> 0:15:41.280 a reason we don't have two brains and there's a 0:15:41.320 --> 0:15:44.200 reason we don't have two mouths because it would be better. 0:15:44.480 --> 0:15:46.720 Or is it satisfying just to say we don't know, 0:15:46.840 --> 0:15:49.320 this seems to work and we can't ever trace back 0:15:49.360 --> 0:15:52.120 all the details of our evolutionary history to understand why. 0:15:52.280 --> 0:15:55.320 Yes, So I tried to find an evolutionary answer, and 0:15:55.360 --> 0:15:58.480 I tried to find a mechanistic answer, and I tried 0:15:58.520 --> 0:16:01.800 to find a like stories that kind of make this 0:16:01.880 --> 0:16:03.480 make sense sort of answer. 0:16:03.760 --> 0:16:06.360 You didn't go for an Aristotilian answer. It isn't the 0:16:06.400 --> 0:16:08.720 way of humanity, to have one mouth. 0:16:08.640 --> 0:16:12.640 To have one butt, one butt but with two cheeks. 0:16:12.840 --> 0:16:15.080 What was Aristotle's theory of the anis? Was he the 0:16:15.080 --> 0:16:16.440 first one to think about the anis? 0:16:16.480 --> 0:16:19.000 You know, I didn't get as far back as Aristotle. 0:16:19.040 --> 0:16:22.160 Actually, you always got to go back to Aristotle, Kelly. 0:16:22.320 --> 0:16:25.160 He's like the original, you know, paper out of the 0:16:25.160 --> 0:16:27.200 Soviet Union that you didn't read and that came out 0:16:27.200 --> 0:16:29.400 in the nineteen seventies that totally scoops your thesis. 0:16:29.720 --> 0:16:31.280 He was the original dude to do that. 0:16:31.720 --> 0:16:34.960 Well, yes, yes, well I'm really I hope that I 0:16:34.960 --> 0:16:38.960 can still give a satisfactory answer having not read Aristotle's. 0:16:38.360 --> 0:16:42.000 Opinion on this, but you know, I will. 0:16:42.080 --> 0:16:45.800 I'll note that having things like two eyes and two 0:16:45.840 --> 0:16:48.200 lungs but only one heart and one brain is a 0:16:48.240 --> 0:16:51.360 sort of ancient state. You know, pretty much all land 0:16:51.480 --> 0:16:54.400 vertebrates have this, and land vertebrates have been around for 0:16:54.440 --> 0:16:58.920 over a three hundred million years. When you go into like, 0:16:59.000 --> 0:17:02.400 you know, the water, you find cephalopods that have three hearts. 0:17:02.600 --> 0:17:05.960 So it is possible to have three hearts. It doesn't 0:17:06.000 --> 0:17:08.359 have to be the case that you only have one heart. 0:17:08.480 --> 0:17:11.840 And on land there are worms that have multiple heart 0:17:12.240 --> 0:17:16.320 like things, but we only have one heart. It does 0:17:16.400 --> 0:17:18.520 kind of start as like two hearts and it sort 0:17:18.520 --> 0:17:23.520 of fuses together into one heart that's like symmetrical with 0:17:23.720 --> 0:17:26.879 you know, two sets of chambers on each side. So 0:17:26.920 --> 0:17:29.280 one answer is that it's ancient. This has been around 0:17:29.320 --> 0:17:32.240 for a long time. So maybe this is the best 0:17:32.280 --> 0:17:35.480 solution and that's why we've had it for three hundred 0:17:35.480 --> 0:17:37.840 million years, or maybe we're just kind of locked in 0:17:37.920 --> 0:17:39.359 at this point, and the fact that we've had it 0:17:39.400 --> 0:17:42.320 for three hundred million years just shows that this arrangement 0:17:42.359 --> 0:17:44.520 of things is sort of hard to get out of. 0:17:44.920 --> 0:17:46.880 Well, what do you mean by three hundred million years? 0:17:46.880 --> 0:17:49.480 What happened three hundred million years ago? Was that the 0:17:49.480 --> 0:17:50.440 Cambrian explosion. 0:17:50.960 --> 0:17:53.240 Well, this is when we started to get land vertebrates. 0:17:53.280 --> 0:17:55.520 So it's when like vertebrates started coming up out of 0:17:55.560 --> 0:17:57.960 the water and sort of walking around on land and 0:17:58.000 --> 0:18:00.800 breathing air as opposed to using gills to extract oxygen 0:18:00.840 --> 0:18:01.280 from the water. 0:18:01.520 --> 0:18:04.040 Okay, because fish, for example, I have two eyes and 0:18:04.080 --> 0:18:05.879 two ears and one mouth, and there's a lot of 0:18:05.880 --> 0:18:08.440 similarities there, right, so it must go back even further. 0:18:08.600 --> 0:18:10.440 There are a lot of similarities I mean, they don't 0:18:10.440 --> 0:18:12.800 have like two lungs, for example, but they do have, 0:18:12.800 --> 0:18:15.080 you know, like two gills. But yeah, so there are 0:18:15.160 --> 0:18:16.960 a lot of things that are similar. But I was 0:18:17.000 --> 0:18:19.160 trying to look for I had lungs on the brain 0:18:19.280 --> 0:18:21.040 when I was starting this, and so I was looking 0:18:21.080 --> 0:18:23.600 for things with two lungs. So I mean symmetry. If 0:18:23.600 --> 0:18:26.359 you just want to ask about symmetry, symmetry goes back 0:18:26.840 --> 0:18:29.520 even farging, Like, there's a lot of organisms that weren't 0:18:29.520 --> 0:18:32.199 necessarily symmetrical the way we are. So if you were 0:18:32.240 --> 0:18:34.960 to draw a line, you know, straight through our head 0:18:35.359 --> 0:18:38.200 that goes down like through our butts, and you fold 0:18:38.240 --> 0:18:40.359 us over more symmetrical that way. I think that's called 0:18:40.400 --> 0:18:45.320 bilateral symmetry. But there are other organisms that are radially symmetrical. 0:18:45.359 --> 0:18:46.280 I think that's what it's called. 0:18:46.320 --> 0:18:48.439 I didn't necessarily plan on going this far back, so 0:18:48.520 --> 0:18:53.240 I'm pulling this out of my uh Aristatilian hole Aristotelian hole. 0:18:53.520 --> 0:18:56.800 So being symmetrical is a thing that has been around 0:18:56.840 --> 0:18:58.320 for a long time. And there's a couple of different 0:18:58.400 --> 0:19:02.080 hypotheses for why symmetry tree is good. A couple hypotheses 0:19:02.080 --> 0:19:03.879 I came across were that, like, you know, one in 0:19:03.920 --> 0:19:07.639 our very ancient history, when we were like tubes that 0:19:07.720 --> 0:19:10.600 were symmetrical, the idea was that it was easier for 0:19:10.680 --> 0:19:14.359 us to like pull food through our tube and like 0:19:14.440 --> 0:19:17.840 extract resources from it when we were roughly symmetrical, and 0:19:17.880 --> 0:19:21.840 then when we became bilaterally symmetrical. So like imagine you 0:19:21.880 --> 0:19:25.080 have flippers, it's easier to move in a controlled manner 0:19:25.119 --> 0:19:26.760 when you're symmetrical on both sides. 0:19:26.800 --> 0:19:29.680 So it was for like locomotory purposes. Does that make sense? 0:19:29.880 --> 0:19:32.400 Yeah, some things that can totally understand why two makes 0:19:32.440 --> 0:19:35.360 sense and one doesn't. You know, like two eyes, one 0:19:35.400 --> 0:19:37.000 on each side of your head to see in both 0:19:37.040 --> 0:19:40.520 directions or to get binocular vision. Same thing for ears, 0:19:40.560 --> 0:19:43.280 same thing for flippers, same thing for legs. Right, two 0:19:43.359 --> 0:19:47.800 legs definitely seem to work better than one leg. But 0:19:47.880 --> 0:19:50.000 I guess I wonder why then you don't have two 0:19:50.119 --> 0:19:53.280 of everything? Right, Like, isn't it always better to have 0:19:53.320 --> 0:19:56.440 to Is there a sort of cost benefit analysis going 0:19:56.480 --> 0:19:59.680