Listener Questions #34

This is an iHeart podcast. Guaranteed human. We have launched Operation Epic Fury. Stop star being a proper country. When everyone says they're right. Who do you believe? None of us knew the depth of that relationship. If the lines are blurred. Who knew? Can you read between them? The depth of the relationship. When the story breaks. Who brings perspective? The mistake I made. If you want to understand the issues that define our times, it starts with listening. Times Radio. On your smart speaker, on digital radio, or the Times Radio app. If you get up early to walk the dog, you might wonder, why all the morning fog? Does blood rush to the head of upside down bats? Or do adaptations help deal with all of that? A spinning black hole is quite the disgrace. It breaks causality all over the place. Whatever questions keep you up at night, Daniel and Kelly's answers will help make it right. Welcome to Listener Questions number 34 on Daniel and Kelly's extraordinary universe. Hello, I'm Kelly Weedersmith. I study parasites and space and I'm excited that today we've got we've got nature, we've got weather, we've got black holes. We've got all the good stuff on the show today. Hi, I'm Daniel. I'm a particle physicist and I almost certainly don't have a goat giving birth in my backyard. Yeah, that's right. Daniel today was like, hey, Kelly, do you want to record an hour early? And I was like, well, first I have to see if my goat needs to have a bowel movement or if she's about to give birth early. We've all been there for moms. But but yeah, I and actually I think it was I think it could be both. Wow. So between every segment today, I'm going to run out and check on my goat and see how she's doing. That's right. You could all be witnesses to the miracle of life. That's right. I know. Or a goat pooping. Or good. Yeah, or both or both, probably both, because it's biology. I guess both count as the miracle of life, right? They're both important functions. That's right. You know, when you don't poop, you kind of wish you were dead, I'm guessing. So so you need both. You need both. All right. Well, that's the backdrop. But in the foreground today, we are addressing your curiosity. We are talking about questions you have about how the universe works from six year old wondering about fog on the way to school all the way to the inner horizons of spinning black holes. And I got to tell you, as of today, I am changing my strategy a little bit because my strategy has been. I take questions from listeners that I do not know the answer to. Yeah. That are hard, that I can't figure out quickly. And I put them on my list. And those are the ones that end up on the show. And now I only have questions that take me like 10 hours or more to answer on my list. And so next time someone asked me a real softball question, I'm throwing that on my list for a listener question episode, because I need some easy ones sort of like sprinkled in there because this one was a bit tough. Unsolved mysteries of biology. Yeah, I did that too. But I also mix in easier questions that I think a lot of people will be interested in the answer or that I think will be fun to joke about with you. Oh, those are all good strategies. Yeah. All right. Well, we learned from each other as much as we learned from the listeners, which is lovely. We're all learning from each other. What a great community. And today we're starting with a question from a six year old. This is a future scientist, folks, somebody who looks out in the world and wants to understand what's going on. So let's get started with our first question. Hey, Daniel and Kelly. So our son just turned six and he's starting kindergarten this year. With that, we've been getting up earlier in the mornings and he started to notice something. The gestational fog and the morning. This is such a great question. I love this question. And also I am particularly excited about fog since we moved out to a farm that has these big fields because the fog will sometimes roll across the fields. And I am really into zombie movies. And every once in a while, I'll look out and as the fog rolls across the field, I'm like, the zombies, they must be coming because it looks like the setting for a zombie movie. And then I'm a little disappointed because the zombies never come up out of the fog and I never get to use my taekwondo skills. But that's probably better. I'd be dead. So all right, Daniel, where does the fog come from? It's foggy in the morning because fog forms when air gets colder. And so at night, it gets colder because it's not as much sunshine. And so it gets foggy. That's the answer I'm aiming at a six year old. But then, of course, we can dig in deeper into the science for the rest of the listeners. Does that make sense? I guess I don't know why it getting colder should make it foggy. And I bet the six year old is also saying, give me a better answer, Daniel. This is not why I listen to DK EU. All right, fair point. Let's dig in. So what is fog anyway? Fog is water. Water can be a solid ice. It can be a liquid. That's what we usually call water, or it can be vapor. OK. That vapor is invisible and it can mix with the air. Or we sometimes say the air is holding that water. You can't see that water when it's vapor, but you can tell that it's there. Like when you go outside, the air can be humid, which feels sticky. Or if you're lucky enough to live in California, the air can feel fairly dry. Right. Or like I visited Houston recently where the air is like chewy. Yeah, yeah, I don't miss that about Houston, really. Got to be honest. Exactly. But if there's more water than the air can hold, then it condenses out and you get droplets, clouds, steam, fog, this kind of stuff. So the air is kind of like a sponge in that it can hold some water. But if you put too much into it, it's going to leak out. And so when there's more water in the air that it can hold, then you get fog or then you get rain. And that's called the dew point. The dew point is the temperature where the air is fully saturated. The relative humidity is 100 percent. It can't hold anymore. And if you go below the dew point, then you get dew where the water like precipitates out into little droplets and forms on plants and stuff. And that's what we call dew. OK, all right. So at night, it gets colder. And the reason that matters is because cold air can hold less water, right? That's right. Warmer air can hold more water and colder air can hold less water. So if you have a bunch of air and it's got some water in it and it's all fine and it can handle that much water, you're like 75 percent humidity. And as you cool that air down, it can't hold as much water. And at some point it passes the temperature where it's at 100 percent humidity. It's the temperature at which it's holding all the water that it can. Then you pass that you go even colder and it can't hold that water anymore. So it comes out of the air and it makes fog. So fundamentally, what's happening here is, as you say, how much water the air can hold depends on the temperature. And you might wonder, like, why is that? Is it related to, for example, how much salt you can dissolve into water, which also depends on temperature? Like you put salt into water, you can dissolve more salt into water when it's hot than when it's cold, right? OK, so I guess what I'm wondering is, all right, so you're outside on a particular kind of day where there's a lot of moisture in the air and it's warm. And so like what kind of warm day would result in the air holding as much water as possible? Like would a warm day always hold as much water as possible? Or does it need to have like rained recently? And now there's more water in the air and so it's holding as much water as it can. Basically, my question is, why isn't there fog every single morning? And so I'm trying to figure out the conditions that result in 100 percent water being in the air. Yeah, cool question. So why does it happen sometimes and not other times? So in order for this to happen, you need moist air. You need water to be in the air. And that's why you often see fog like near valleys or near the ocean or near lakes or after rainy days or in fall when the nights are really, really long. So it gets colder at night than it does in the summer. So you need a source of that water. So if it's rained or if you have a valley with a river or a lake or something, you need a source of that water in order to make it moist. So you ask like what kind of day is going to be like hot and moist? Something where it rained or where there's a nearby body of water to evaporate from? You need that source of water and you need to get it up into the air on that hot day. And then you need to cool it down. And the best way for that to happen is for the night to be clear. So there's good cooling because otherwise some of that heat is going to be reflected by the clouds back at the earth for there to be very light winds because winds tend to mix up the hot and the cold air and for the ground to be as cold as possible. So on a clear night with light wind and cool ground after a rainy day or near a lake, you're very likely to get fog. OK, awesome. Now let's give me. Why do I want to know about salt also? When I was reading about this, I was thinking about air being saturated by water and imagining that maybe it was similar to dissolving something into a solution. Like, you know, how you can put salt into water and then you don't see it, right? It's not visible. The same way that there can be like water in the air, but you're not looking at it, right? It's like held by the air. And so I imagined that it was similar. Maybe this is the same kind of process you can use your intuition. Turns out it's not. Oh, OK. Yeah. When you dissolve salt into water, the salt actually forms bonds with the water. It's actually a chemical solution. But water in the air is just more like a mixture of gases. You have like a mixture of air and water vapor. So it's not a great analogy. So for those people listening and thinking, you can use your intuition for salt and water to understand air and water. That's a bit of a trap. So don't go down that hole. But there is something really fascinating happening here chemically. We talked about the dew point, the temperature beyond which things precipitate out into the air. It's not actually quite so simple. What's really happening is you have condensation at every temperature and you also have evaporation at every temperature. What happens when you cross the dew point is that you have more condensation than evaporation. So above the dew point, you have more evaporation than condensation. So the air is taking in more water if you like are injecting water somehow. Then the air is gobbling that up. Whereas below the dew point, you have more condensation than evaporation. So the air is losing the water. So it's a smooth transition as you cross the dew point between being dominated by condensation and being dominated by evaporation. And this helps you understand why it's temperature dependent also because imagine the air and you have all these molecules of air and then you also have water in the air, right? But there's no bonds between the water and the air, but there are bonds between the water molecules. So you have a droplet of water in the air, like a little in one piece of fog, like a fog particle or a foggy no or whatever. It's held together by little bonds because water is polar. Remember, and so like one end of it is charged positive, one end of it is charged negative, so it can kind of stick together. So water molecules, when it's a little drop of fog, are bound together by these hydrogen bonds between the molecules. And in order to evaporate, they have to have enough energy, enough kinetic energy to evaporate. So as the temperature goes up, more of these things have enough kinetic energy to break those bonds and evaporate into the air. So that's why at higher temperatures, there's more water that can bounce around without getting stuck to other little water molecules and making little foggy no particles. So it's all about the temperature of the water, really. And of course, the temperature of the air and the water are the same because they're in equilibrium. So what do you think it is about foggy mornings that make zombies more likely to be moving around? You look a little frustrated, actually. Sorry. I pride myself in being able to prepare for almost any question you're going to ask. But wow, you totally caught me flat-footed. So here's a completely impromptu answer. The foggy no particles interact with the zombie field. And so there's a resonance between those two. And so sometimes the zombie field will get energy from the foggy no particles. And then you'll just precipitate zombies out of the quantum vacuum. Holy cow. Oh, my gosh. Also, that was complete nonsense. Obviously, but that was amazing. You used all the right words in all of the fancy ways. And, you know, I think maybe we should start doing like a supernatural sort of podcast. And then maybe we could get ahead of... Oh, what is the show that's ahead of us? Sasquatch Hunters. The Sasquatch Chronicles. Yeah, that's right. No, that's just a lesson in how easy it is to sound like you know what you're talking about if you use big fancy words, even if you're spewing gibberish. All right. Anyway, OK, so sorry. Back to the foggy no's. And OK, so so do in the morning is fog that has settled on plants and stuff. Exactly. Side note, just to like Kelly being a nature nerd. One of my favorite things in the morning is to walk through our hay fields and see all of the teeny tiny little spider webs that I always miss. But you can see them because the do has settled on them. There are literally thousands of them out there. There's this tiny little universe that you can only see in the morning when the dew makes it visible and you miss it otherwise. And it's just like when you look at the world at different scales, there's all of these things that you missed at the scale that you live. And anyway, I love walking in the morning like when you can still see what the dew makes visible and a good reason to get up early sometimes. In high school, I had to get up early for a marching band and the field was always covered in dew, which had then frozen and crunching on those frozen blades of grass that was always so satisfying. Oh, OK. I thought you were going to say you didn't like that. And so, yes, two positive stories about getting up early. I did not like getting up early for marching band. That was the one good thing about it is crunching the frozen grass. You know, it's it's satisfying the way like stepping on a frozen river and cracking that ice is also satisfying. I don't know if you feel that way. You know, I like that. I like that. Can I share one negative getting up early story? And then we really need to get back up. Should we just get back on track? Maybe we should just get back on track. Well, why don't you say it? And it's not funny enough. OK, all right. So when I was in high school, senior year of high school, I worked at a bakery at a zoo and I had to get there at five a.m. to cook the cookies before everyone got there. And one morning I was feeling super grumpy and I was like, I can't. Who in high school gets a job where you have to be there at five a.m.? Yeah, what were you thinking? What am I thinking? Right. And so I get there and this little bird lands on a fence and it starts singing this beautiful song. And I'm like, OK, all right, this is why you get here. And was there fog? I don't remember. I don't remember that. I just remember. Kelly, there has to be fog to connect to the question. And there was fog, but no zombies. And anyway, seeing this beautiful song and then out of nowhere, a raptor comes by and literally scoops the bird up and rips its neck out. And I was like, that's mornings for you. Yes, that feels a little bit more on key. And anyway, I felt so bad for that bird. That's biology for you. That's biology for you. And anyway, that felt the joy of life. Yeah, I was like, no, right. OK, that's right. This is why you don't get up in the mornings. Early birds, I don't know, they get their next rubed out. Be careful, early birds, because in the morning there's fog and the raptors can swoop down out of their hiding places in the mist. That's right. All right, so Chance, send this explanation to your six year old. And let's see if we've scratched that itch or confuse them with stories of raptors and zombies. Thank you so much for answering my questions. I think it's called the Alice Like His Birds. I don't have any more questions. Thank you. Spring is here and it's time to get out in the garden. 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OK, we're back and we're answering questions from listeners as well as giving live updates on Kelly's goat. Oh, that's staying in the show, huh? Kelly, did your goat give birth? No, not yet. Not yet. She was chewing her cud and she got up to say hi when I went out to check on her. So she is not an active labour right now. But her udders are bigger. So I think we're... Are they utterly huge? They're not utterly huge yet. But her bag has expanded, as the vet said. Well, I'm going to milk these jokes as long as I can. Amazing, amazing. And I'm going to see how many zombie references I can get in there. So this is going to be a great show. All right, well, the next question is not about goats or zombies or even vampires, but it is about bats. Oh, yes. So this is a question from Huntington. And this is also a question that involves a child. Which I love. So, yeah, and absolutely keep sending us questions that you and your kids have, or just questions your kids have. And so let's go ahead and hear the question now. Hi, Daniel and Kelly. Probably more Kelly. My son and I were reading about bats and the book said that bats have valves in their circulatory system so the blood can't rush to their heads when they are upside down and make them dizzy. My son then asked, Why don't geckos get dizzy? And wondered if geckos can get dizzy. Why don't geckos get dizzy? And wondered if geckos had something similar in their bodies to bats. I looked but couldn't find the answer and was hoping you could have out. Thank you. Boy, this is a great question. But before we understand like bats and geckos getting dizzy, like, what does it mean to get dizzy anyway? Why do humans get dizzy? What is that all about? Yeah. Yeah. So when I get a question, one of the first things that I do is I like break the question into pieces and then you have to check the premise of each part of the question. Not because you don't trust the listener, but because like, you know, one, you just want to make sure that everybody understands all the different parts of the question. So the first part of the question here is why do you get dizzy? And so what's implicit in this question here is that what makes you dizzy is the blood rushing to your head. And maybe when the blood rushes to your head, it can't get back to your heart. And so it doesn't get oxygenated or maybe it's the change in the fluid pressure in your head. But actually getting dizzy is a very complicated thing and it can be caused by a lot of different things. So I was looking at like a Mayo Clinic website and anxiety can make you dizzy. Really? Yeah, apparently. And folks who study virtual reality and who try to make those virtual reality headsets have been sort of amazed at the many different ways that humans can become dizzy when you, you know, put them in a virtual reality setup and they'll report like, oh, no, that made me dizzy. Now I kind of want to puke. You know, no, your underwater setup didn't calm me down. It made me feel like the world is spinning. And so anyway, being dizzy is a complicated thing. But let's look at two potential reasons for getting dizzy. Let's go ahead and dig into the one that's implied in the question first, which is blood rushing to your head. Blood rushing to your head makes you dizzy. I always thought it was low blood pressure that made you dizzy. Yeah, so for me, when I stand up and, you know, I have less blood in my head for a moment, that is what makes me dizzy. And I'll admit, I shared some of this question on Blue Sky. I did get some responses from people being like, blood rushing to my head doesn't get me dizzy. It's blood rushing out of my head that makes me dizzy. And so it did seem like there was a general agreement that it's the getting up that makes you dizzy, not the not the blood rushing to the head that makes you dizzy. But there were folks trying to understand how maybe blood rushing to the head could make you dizzy. And the general consensus was that maybe what's happening is that when the blood rushes to your head, you know, one, you get a pressure increase, maybe that's a bit disorienting, but two, maybe the blood is pooling in your head. And when it pulls in your head, perhaps you get low oxygen because your body is used to gravity, helping you get the blood down. And so it's less good at pumping the blood away from your head when your head is in the wrong orientation. And so maybe it's not oxygenating as well under these conditions. And so maybe under these lower oxygen conditions and this higher pressure, it's making you sort of dizzy. I see. And again, I'm not actually sure that that does cause dizziness. There was some debate about that. But the statement that was made in this book was that for bats, this isn't a problem. Even though they sleep upside down because their circulatory system has valves and these valves essentially keep the blood from pooling in the head. And so I think the idea here would be that they make it so the blood can't flow in the wrong direction and pool. And so that was the statement. And so the question was bats have these valves. Do geckos have the valves too? And I guess humans don't have these valves because humans can't be upside down for very long without their head popping or something, right? Well, OK, so the equivalent of being upside down essentially would be like being in space. So when you are in space. Pivot to something you know about. That's right. Yes. Yeah, right. I was like, I don't know the answer to that, but I know the answer to something else. So when you're in space, the fluids shift up to your head and people do report feeling dizzy and disoriented. But that is partly maybe because of fluid shifts, but also because of this other thing that we're going to talk about in a moment, which is it messes up your vestibular system also. Your what? Your system vestibular system. Hold on. That's the next thing we're going to talk about. OK. But what we do with our fluid shifts is we pee a lot. And so our body releases a lot of fluids because our body is like there's too much pressure up here. We're kind of confused about it. And so you urinate a lot. You lose a lot of the fluid. But we do think that you still have problems resulting from having too much fluid in your head. So for example, astronaut vision gets worse over time. And we think partly that's because you do have more pressure in your head because of more fluids in your head. And we think that's pressing on your eyeballs. And people also report that that there are wrinkles go away because with more fluid in their faces, it kind of presses out the wrinkles in their skin. And so but they survive. So anyway, I think you can essentially have fluids pushing up on your head and survive. Your body has ways of dealing with it. They're kind of weird, though. But bats have these special valves and now we're on to geckos. OK, but no, or do they? Oh, I see. So the first thing I do is I was like, all right, well, I'm going to look it up. Do bats have these valves? And so I did find some websites like when I just did a plain Google search that were saying like, oh, bats have these valves, blah, blah, blah. And I was like, all right, well, I'm going to find a scientific paper that talks about these valves. And I found a mention of valves in the wings that like help them with flying. But I couldn't find mention of any valves related to helping them deal with being upside down. And in fact, I even found a paper that talked about how bats sleep upside down. And they were talking about how when they sleep upside down, there is an increase in their cranial pressure because fluids shift into their brain, which would suggest they don't have these valves. And in fact, that paper did not talk about valves at all. And in fact, they talked about how if you hold bats upside down for even longer, there are heart remodels to deal with the fact that it needs to accommodate being upside down. But why can it be such a deep mystery whether or not bats have these valves? Bats are not like rare or microscopic or invisible or shifting into zombies in the morning mist. Like, why doesn't something just open up a bat carcass and look? OK, well, so here's the thing. Another valve story that I've heard a lot. And I'm going to answer your question. Just stick with me for a second. Is that giraffes have these valves also because they have these very long necks, right? Yeah. And then when their head goes down to take a drink of water, they also need to have valves to make sure that their blood isn't rushing to their head and then rushing back, right? I'm imagining some like complicated steampunk giraffe now. Energetically pumping stuff up and then pumping it back when the head turns around. This is a crazy system. Well, so the idea is that they've got these valves so that the blood like is essentially stopped from like pooling in the wrong spot. Oh, I see. And so there was an experiment that had these giraffes that they anesthetized and they held them up in the air in these braces. And then they essentially, while they were anesthetized, lifted their heads up and then put their heads down and then kept track of like where things were going. So they're like, they're like tilting these snoozing giraffes. What a hilarious experiment. Oh my gosh. I know. Amazing, right? And so then they were like monitoring changes in pressure and then like looking at like how the hearts were responding and stuff like that. And then they looked and that like, you know, where are the valves and stuff? And here it says, histological examinations revealed no valves in the carotid arteries. Although such arterial valves have been mentioned in more popular accounts such as the Encyclopedia Britannica online. Oh no. Wow. You're calling out the Encyclopedia Britannica here, Kelly. I am not. The paper is. The paper is. And so I think that there has been like this valves deal with being upside down idea that has maybe escaped into the popular imagination. Oh. Another example of a gap between scientific and popular knowledge. Maybe. And I'd love to know where this came from. And so anyway, so okay, basically what I'm saying is I watched a bunch of videos and the bet experts, when you ask them how bats managed to be upside down, they did not mention the valves. What they said was bats are so small, it doesn't matter. They have strong hearts and the distance between their heart and their head is small enough that they can just pump it and it's okay. Their hearts just get stronger if they need to. And they didn't say anything about valves. They just said they're small enough, doesn't matter. And I couldn't find any evidence of valves. This is a fascinating crossover between physics and biology actually. It's not like you can take the same biological system and just like scale it up by a thousand or scale it down by a thousand and assume it's going to operate the same way. Because like pressure and volume and surface area and mass, these things all grow differently with size. And so they'll be like totally out of whack if it gets too big or too small. So you're saying the same system, which is susceptible to getting dizzy and having blood pooling at our scale or maybe even giraffes, doesn't happen for bats. I think that is the answer. Because like the bat experts were not mentioning the valves. I couldn't find the valves in the literature. If anybody wants to write into correct me, please tell me. And then in a future listener questions episode at the beginning of the episode, I will say there is evidence of the valves and I just missed it. Send us proof of the alleged bat valve. That's right. Well, I think Daniel and I would always like to be corrected if we're wrong about something. So please let us know. Don't be shy. Write in with your well actually comments. Please do. Yes, please. Absolutely. Okay. And so another reason that we get dizzy is because we have this system in our head that helps us figure out like balance and where we are in the universe in this system. So I use the word earlier and I will for Daniel's sake avoid biology jargon from here on out after I say the word one more time. This is vestibular. Vestibular. It's in your inner ear and it's a system of tubes filled with fluid. And when you move, like when you rotate your head side to side, the fluid starts going around the tube. It's an accelerometer. It is. Yeah, it's like an accelerometer. It is an accelerometer. It is an accelerometer and your brain detects that the fluid is going around in that tube. And sometimes so like if you start spinning in place over and over and over again, that the fluid in that tube is going to start spinning and spinning and spinning and spinning. And then if you stop spinning all of a sudden, it's going to take a little while for that fluid to stop spinning. And so for a little while there, your brain still gets the message that you are spinning while your eyes are telling your brain, I am not spinning. And we think that that disconnect between what your ear is telling your brain and what your eyes are telling your brain is part of why you feel dizzy because you're getting conflicting information. And to be honest, we don't 100% understand dizziness. Has nobody done the experiment of taking a bunch of giraffes and putting them on America around and interviewing them about whether they got dizzy? That seems like that would settle the question. Yeah, we need a lot of money for that experiment probably. NSF call us. That's right. That's right. We will take your money. But it does suggest actually that if you spin in the opposite direction, that could slow the fluid down and that might be a way to help your dizziness go away faster, which is kind of a fun experiment. Interesting. Not medical advice people. Not medical advice. Kelly is never giving official medical advice. I am not that kind of doctor. If your kid is dizzy, do not spin them the other way on our advice. It's just an interesting thought experiment. That's right. That's right. And so we've got tubes that go in multiple different directions to accommodate for spinning in multiple different directions. And then we also have a system of essentially crystals that are tied to hairs. And this tells you about moving it like forward and backwards. And so if you go forward really quick, then those crystals are going to get pushed forward and they'll pull on the hairs. And that's how your body knows that like, oh, we just kind of moved forward. And that sends a message to your brain that we move forward. No, we accelerated, Kelly. We accelerated. We accelerated. Thank you. Thank you. Your ear can't tell that you're moving or that its velocity can only measure acceleration. It's like a bowling ball in the back of a truck, right? At 70 miles an hour in the highway, the bowling ball doesn't move. But if you hit the brakes, then the bowling ball rolls to the front. So even if you didn't know your velocity and you couldn't measure your acceleration in any other way, if you watch the ball, you can tell if you're accelerating in any direction. And that's what's happening in your ear. It's an accelerometer. Okay. Yes. So we've got two different kinds of accelerometers in our ears. And geckos and bats have these as well. Presumably, geckos and bats could get dizzy also if they moved too quickly and messed with these kinds of accelerometers. And so I'm guessing they have the same kinds of constraints because I did look up, do geckos, for example, also have semicircular ducts. And they do also have these kinds of semicircular canals. And so I think they could possibly also get dizzy. They've got the same system that we have. I think I might have a special mutation because I tend to get dizzy when I hear too many biological Latin names. You know, I wanted to talk to you about that because you told me that you wanted me to say things like beetle one and beetle two. And I was thinking that from now on, we're not saying muons, gluons, no fermions, no bosons. It's particle one, particle two. What's good for the goose is good for the deer. That's right. Yeah. We're going to simplify all of this from now on. Okay. So anyway, to finally answer the question, why don't geckos get dizzy? Yeah. Nobody knows. Nobody knows. That's right. Who knows? I think they might get dizzy. I think they have a similar semi-circular canal system that we have, and sometimes we get dizzy. Sloths hang upside down. And I think the answer for why they don't get dizzy is they move kind of slowly. That's an answer I found online. So maybe geckos also have to be a little careful about moving slowly sometimes. But if they're running away from a predator, maybe they do get a little bit dizzy from time to time, but they just have to deal with it like the rest of us. I don't know about this valve thing. I didn't find evidence for it, but I'm welcoming people to correct me. And thanks for this fun question. I enjoyed reading about semi-circular canals and the circulatory systems of bats and geckos. And this took me down so many different rabbit holes. Fascinating. It was a lot of fun. That's one of my favorite things about listener questions is how much we learn in digging up the answers. Absolutely. All right. Let's see if I gave a moderately satisfactory answer to Huntington and your son. Let's see how this went. So what do you think? That's pretty good. That's pretty good. It's pretty good. I wonder if I can go, okay, this is Greg's lesson I need to tell. Thank you for breaking down the question and exposing the assumptions we didn't even know we were making. I'm honestly surprised to learn that bats and giraffes don't have vowels like we had read about. I guess that is a lesson about trusting and verifying the information we read in Popsai books. I guess I shouldn't have been surprised to learn that for something we've all experienced. There is not a clear explanation for dizziness, but I still was. My son enjoyed the answers and was very satisfied with them, something that I have never been able to provide with my answers. So thanks again and keep up the great work. Another party invite. Well, here's a way to make their big day feel even more special. Create an unforgettable birthday with Etsy with original finds just for them. Like sparkly sashes and customized drink glasses, or festive balloons and streamers to make the big birthdays feel even bigger. From the personalized to the practical, we've got you covered with millions of active listings to choose from. Birthdays don't celebrate themselves. Shop at etsy.com and discover your perfect find today. E45 lotion is effective, science-backed hydration for everyday use. Light weight, fast absorbing, and trusted to do what your skin needs. No fuss, no compromise. Just soft, smooth, healthy-looking skin every day. Grab your E45 lotion now. All right, Warshak almost got out of the barn. Lottie's looking a bit uncomfortable. I'm going to be sitting with her for the hour after we're done. All right, we're back to Daniel and Kelly's extraordinary universe and the extraordinarily fun watching of Goats Kidding. In the brief interval before Kelly's goat gives birth, we're going to try to answer a complicated question about what's going on inside spinning black holes. Here's a fun question I got from Joe. Hi, Daniel and Kelly. This question is more for Daniel. I understand that the inner workings of a black hole are a mystery to us, but I heard something about a couchy manifold. It's some kind of inner horizon. And I'm wondering how these complex mathematics might be explained. Oh, this is fun. I don't think I know what a couchy manifold is. Did I say it right? Couchy, yeah. Couchy. Well, no, the answer is no, because that's not what I said. I was trying to be gentle. You're nice. I like that. We can call it couchy if you prefer to imagine sitting on a couch while understanding these things. Oh, yeah, I like sitting on a couch while understanding the universe. So what is a couch? Oh, no, I already forgot. Couchy. Couchy. So a couchy horizon is where causality breaks down. And this is going to be really surprising because we're talking about classical physics, which is famous for being deterministic, which means that like the past determines the future. You have a bunch of billiard balls. You shoot them at each other. They bounce off at some angle. They're going to do that every time because the past determines the future. There's no fuzziness. There's no randomness. We're ignoring quantum mechanics completely for this answer. Imagine we live in a universe ruled by classical physics. Usually we think, and we talked about this on the weather modeling episode, if you know everything about the universe, like where all the particles are, where they're going, their exact state of the universe, plus, you know, the rules of the universe, meaning like how things interact and how they will bounce off of each other, then you can predict the future. Right. So perfect knowledge of the current state plus perfect knowledge of the rules, you should be able to predict the future. That's causality in a nutshell. Sure. But I thought we also determined that it was also a little too complicated and we couldn't actually predict the future. But technically we should be able to, if we could, do those complicated equations. Absolutely. But yeah, okay. Absolutely. If you had perfect knowledge of the universe, which you never do, not even because of quantum mechanics, but because there's just too much information, like in the case of the weather, we don't have enough buoys out in the ocean, and we don't have enough airplanes with thermometers on them. We don't have all that information. But in principle, that's a practical problem and engineers could overcome it. The information exists and is accessible in a classical universe, which isn't our universe. So there's lots of reasons why this could never happen. But if you imagine a classical universe, it is possible in principle to have that information. It exists. And in that classical universe, because we've assumed the universe is classical and that there are rules. And if we knew those rules, then in principle, we could perfectly predict the future. Got it. Okay. That's the setup. But there are some caveats. Right. And those caveats are what we're talking about today. Caveat number one is about the speed of light. And it's not actually directly related to the chemistry horizon, but it's a good warm-up. Because what you actually need to predict the future is not all the knowledge in the universe about what's happening. Some things in the universe can't affect your immediate future. The only thing that can affect the immediate future is parts of the universe where light has had time to get here since that event. So for example, if there's an alien right now in Alpha Centauri, and they're aiming a death ray at us, and they fire the button, boom, right now, to shoot that death ray at us, it cannot affect what's going to happen right here on earth in the next millisecond. Because there isn't time for that death ray to get here. So we say in physics, it's not part of our past light cone. Our past light cone is everything that can affect the immediate future. And because there's a speed limit on information and signaling, the things that can't get here are outside of that past light cone. Okay. I understand. It still feels like there's an approximately infinite number of things we can't measure, and we've knocked a small fraction of them out. But okay, but all right, there's some things now we don't have to worry about. But of course, that death ray will eventually arrive at earth. And in a couple of million years, that alien shooting that death ray, that event, will be in the past light cone of our future. Right? So it's a time dependent thing. Our past light cone is not just a location, it's locations and times, it's events in space time. Some of those things that are outside our past light cone right now can be the past light cone of people in our future. Because aliens, if they shoot that death ray, can kill our great, great, great, great, great, great, great grandchildren. Okay, got it. So wait, what is the question that we're trying to answer then? Are we trying to answer who's going to die? Because then it seems very relevant to them. So we're trying to answer what is a Cauchy horizon. And a Cauchy horizon is a place where you cannot predict the future. Okay. All right. And they might wonder, how does that happen? What's going on? Classical physics, things are deterministic. In fact, they only depend on a subset of the universe, your past light cone. How is it possible to have in classical physics, a setup where you can't predict the future? And the answer is if you have something in your past light cone, like a singularity, which is like a breakdown of classical physics, something that's unpredictable. Okay. The short answer is that a Cauchy horizon is what happens inside a spinning black hole, where there's a singularity inside your past light cone. And a singularity is not something you can fold into your equations, because it has an infinity in it. And so it makes it impossible to predict the future. Okay. So let's dig into that a little bit more and understand why that happens. And to do that, let's remember what a black hole is anyway. A black hole in popular science is often like a thing in space that has really strong gravity and sucks everything up, right? But actually gravity is not a force. It's curvature of space time. Objects are moving to follow that curvature. And black holes are just places with really, really strong curvature, because you have a lot of mass in a small area. So the curvature gets really, really strong. And it gets so strong that you get an event horizon. And then horizon is like a dotted line in space. And anything that goes inside the event horizon will never leave the event horizon. Okay, so that means that a particle inside the event horizon, its entire future is in the event horizon. There's no place in the event horizon and no particle trajectory you can even come up with that's ever going to leave the event horizon. Okay. And the reason is fascinating, because the curvature inside the black hole is so strong that the singularity inside of the black hole is not like a location in space. Space and time get twisted. So that singularity is a location in time. You can think of it like inside the black hole, space is one directional. So the singularity is always in your future. No matter what you do, every path leads to the singularity. So the singularity is not like a place in space you can like fly by and try to avoid. It's not like the grocery store, you can go to it or you can not go to it. It's like next Tuesday. There's nothing you can do to avoid next Tuesday. It's coming. You can't pass it, you can't go around it. It's in your future. Okay, so before we were talking about being in a light cone where aliens were going to destroy us. Yeah. And there could be a singularity. And now we're talking about singularities in a black hole. Yeah. And so the connection is, so remember we're answering the question, what is a Cauchy horizon? Cauchy horizon is a place in space where predictions break down. And they break down because you have a singularity in your past light cone. It's like in your history. And singularities are infinities, you can't use them to calculate. And it's a special kind of singularity because the normal kind of singularity we're talking about, the kind that are inside vanilla black holes are not like that. They're in your future. A singularity inside a vanilla black hole can never be in your past light cone. It's always in your future. Right. It can't affect anything that's happening. It's always something that's going to happen to you. So how do you get a singularity in your past light cone so we can disrupt your predictions of the future? For that, you need a special kind of black hole. You need a rotating black hole. Black holes we've been talking about so far, just a dense point in space, curvature is really, really strong, space is bent so that the singularities in your future. But if you spin that black hole, you get a very different kind of space time structure. Something that happens in Einstein's gravity, which differentiates it from Newton's gravity, Newton says, gravity is a force, Einstein says it's a curvature. Most of the time they give the same answers, but they differ when the mass is spinning. Newton says, something that spinning has the same force as something that's not spinning. It doesn't make any difference. Like the force on the moon from the earth doesn't depend on the fact that the earth is spinning according to Newton. Einstein says, actually, gravity is curvature in response to energy. Spinning is a kind of energy. And he's got all these complicated equations, there's like 16 of them and a big tensor. So the direction matters and it causes a twist in space time itself. So it's a very complicated response to spinning. And so what it means is that inside a spinning black hole, there's two horizons. There's still the event horizon, just like a normal black hole. Once you fall in the event horizon, there's an inner horizon, that's the Cauchy horizon. The Cauchy horizon is still in your future. So you fall into the spinning black hole, then there's no way to avoid falling in even further till you get past the Cauchy horizon. Once you're inside the Cauchy horizon, then the spinning singularity at its heart is not in your future. It's a different kind of singularity. It's actually avoidable. You can like be in an orbit around that singularity. It's not just in your future. It's more like the grocery store than like next Tuesday. The problem is that that means it can be in your past. It can affect things that happen to you. You can like send out signals from the singularity, which can arrive at you and change what happens to you. But nobody knows how to calculate what signals what a singularity send out. It's an infinity. It's a breakdown. So inside the Cauchy horizon, you have this thing which can be in your past, but it's also sort of nonsense, like you don't know how to calculate it. And because of that, it means you can't predict what's going to happen. So you have a situation in the universe where you have something in your past light cone, which can affect your future. We're not talking about faster than light communication, but also you don't know how to calculate it. So you can't predict your future. It's like you were saying before, if you don't have all the initial information, if you can't describe the current state of events, you can't predict the future. Well, what if there's something that's just indescribable in your current state of events, then you can't predict the future. So the Cauchy horizon is the part of space time inside a spinning black hole where you have this singularity in your past. And so predictions are just off, like you just cannot make them. It's amazing because you think of classical physics as predictable, deterministic, like a clockwork universe. But there are places where it goes crazy. Does every black hole have a singularity in it? Every black hole has a singularity in it according to general relativity. Now, we don't think general relativity is correct. In fact, it probably breaks down at exactly this place, the singularity. So in reality, in our universe, are there places where you can't predict the future? Probably not, because all of this is probably wrong, and we need quantum gravity to describe what's going on here. And in fact, singularity is an example of why we think general relativity is probably wrong, because singularities, their very existence is in conflict with quantum mechanics. And quantum mechanics itself is actually kind of deterministic. It doesn't predict the exact outcome, but it predicts the probabilities in a very deterministic and specific way. So this would also mess up the determinism of quantum mechanical probabilities. So most physicists think, yeah, this is interesting little quirk in the calculations when you assume the universe is classical, but nobody thinks that it is. And so it's probably irrelevant to reality. But it is a fascinating little corner of general relativity, where predictions are just not possible. And that's why spinning black holes, which are probably in reality much more common than non-spinning black holes, have this two-stage structure. They have the event horizon and the Cauchy horizon. Okay, so given what you just said, if you had to guess if any of this stuff is actually going on, would you guess? 0%. Okay, got it. Okay. Yeah. All right, Joe, thank you for your curiosity about spinning black holes and inner horizons and Cauchy manifolds. Let me know if that answered your question. Wow. Well, I think I got about 80% of that. A spinning black hole with an event horizon where causality breaks down. That's fate worse than spaghettification, I think. But maybe spaghettification is the future that we can't predict with certainty. Although I think I'd be pretty certain to avoid the Cauchy horizon. Thanks a lot. Thank you, everyone, for sharing your curiosity with us. If you have a question, you'd like to send our way, send it at questions at danielnkelly.org. We would love to interact with you. Please do write to us. We're not just saying that. And we would massively appreciate it if you'd be willing to leave us a review on Spotify, Apple, whatever podcast app it is that you listen to us on. It helps other people find the show. And if you reviewed us several years ago and you're thinking that doesn't apply to me, come back, review us again for the new show. Thanks.