Daniel and Kelly’s Extraordinary Universe - Why do planes fly?

Episode Date: December 12, 2024

Daniel and Kelly dig into the surprisingly controversial question of why airplanes stay in the air.See omnystudio.com/listener for privacy information.

This is an IHeart podcast. Why are TSA rules so confusing? You got a hood of you. I'll take it all! I'm Manny. I'm Noah. This is Devin. And we're best friends and journalists with a new podcast called No Such Thing, where we get to the bottom of questions like that.

Why are you screaming? I can't expect what to do. Now, if the rule was the same, go off on me. I deserve it. You know, lock him up. Listen to No Such Thing on the IHeart Radio app, Apple Podcasts, or wherever you get your podcasts. No such thing.

I'm Dr. Joy Hardin-Bradford, host of the Therapy for Black Girls podcast. I know how overwhelming it can feel if flying makes you anxious. In session 418 of the Therapy for Black Girls podcast, Dr. Angela Neal-Barnett and I discuss flight anxiety. What is not a norm is to allow it to prevent you from doing the things that you want to do. The things that you were meant to do. to listen to therapy for black girls on the iHeart radio app, Apple Podcasts, or wherever you get your podcast.

Hi, it's Honey German, and I'm back with season two of my podcast. Grazias, come again. We got you when it comes to the latest in music and entertainment with interviews with some of your favorite Latin artists and celebrities. You didn't have to audition? No, I didn't audition. I haven't audition in like over 25 years. Oh, wow.

That's a real G-talk right there. Oh, yeah. We'll talk about all that's viral and trending, with a little bit of cheese, and a whole lot of laughs. And of course, the great Vibras you've come to expect. Listen to the new season of Dresses Come Again on the IHeartRadio app, Apple Podcast, or wherever you get your podcast.

Every case that is a cold case that has DNA. Right now in a backlog will be identified in our lifetime. On the new podcast, America's Crime Lab, every case has a story to tell. And the DNA holds the truth. He never thought he was going to get caught. And I just looked at my computer screen. I was just like, ah, gotcha.

This technology's already solving so many cases. Listen to America's Crime Lab on the IHeart Radio app, Apple Podcasts, or wherever you get your podcasts. Our IHeart Radio Music Festival, presented by Capital One, is coming back to Las Vegas. September 19th and 20th. On your feet. Streaming live only on Hulu. Ladies and gentlemen, Brian Adams, Ed Sheeran, Fade, Chlorilla, Jelly Roll, Sean Fogarty, Lil Wayne, L.L. Cool Jay, Mariah Carey, Maroon 5, Sammy Hagar, Tate McCrae, the Offsprin, Tim McGraw.

Tickets are on sale now at AXS.com. Get your tickets today. AXS.com. They say that any technology sufficiently advanced is indistinguishable from magic. Well, there's one technology that people have... lusted after for thousands of years that we now rely on, even find routine. I'm talking, of course, about flight. It's been only a hundred years since people were able to leave the ground and fly through the air and return safely. Now it's so routine that people sleep through it. But imagine what that would seem like someone from a thousand or 10,000 years ago. It's essentially like magic. Of course, we know it's actually not. It's science, because we can understand it,

and we can break it down, we can explain it. We understand why planes fly. Right? Do we? Could we actually explain it to visiting ancestors from the deep past? Or is it still some kind of black magic, even for modern humans and the best aeronautical engineers? So today on Daniel and Kelly's extraordinary universe, we'll be asking an old question, why do planes fly? Hi, I'm Kelly Wiener-Smith, and my favorite way to travel is by train. Hi, I'm Daniel Whiteson. I'm a particle physicist, which means I have to fly around the world to get to the biggest particle accelerator. And what is your worst flight experience?

My worst flight experience is traveling with my own six-month-old baby. We had a bassinet, and we got her to sleep. in the bassinet, and we thought, oh, this is going to be great. Then the stewardess came by and said, oh, there's some turbulence. You have to take her out and put her in a seat and buckle her in. And we said, no, she's sleeping. And she said, sorry, it's the rules. And everyone around us went, oh, no.

And they were right because she screamed for the rest of the eight hour flight. Oh, no, that's horrible. I'm so sorry. When you finally get your kid asleep and something wakes them up on a plane, it's the worst. It's the worst. And everybody knew it was the worst. And we all knew there's nothing we could do. But hey, you know, them's the rules.

How about you? What's your worst traveled experience? It also involves playing with my child. She was probably about six months old around there also. And I brought a change of clothes for her. I was totally prepared for her. She was sitting on my lap and we were about to take off. And right as the plane started moving forward, she had a blowout poop on my lap.

And so it smelled horrible. But you can't get out of your seat until you reach cruising altitude. So everybody was like giving me dirty looks and covering their noses. And it took like 20 minutes before we were allowed to get out of our seats. And then, you know, I had to change her in the airplane changing room, which is like, so tiny. I thought she was going to fall off the little tray. And anyway, I brought a change of clothes for her, but I didn't assume I'd have poop on my pants. Oops.

Classic parenting mistake. Exactly. So I smelled horrible the whole flight and people kept looking at me and it wasn't a lot of fun. But them's the breaks. You got to leave the house with kids sometimes. You just got to look back of those people and say, hey, who's going to pay for your Social Security, right? Somebody's got to make the next generation. And it's me, Madame Poopie Pants.

I'll get a little, like, badge that says that. Now whenever I see a parent with a kid, I'm like, what can I carry for you? How can I help? Like, I offer to help now all the time. Yeah, exactly. And the big lesson I learned is never judge. And you never in somebody else's family. You don't know what they're going through or what they're struggling, whether how much

they slept last night, just help and smile. Yep. And kids are always at their worst because they're always the tiredest and they're not used to it. And so like, anyway, yes, don't judge. But planes are wonderful. I needed to get from place to place and I needed to get there quickly. And actually, I wouldn't have wanted to take my daughter on a long train ride for the journey that we were going on because it would have been days. But I was flying to London the other day and we had kind of talked about why do planes fly? And you said it's complicated. And while I was, you know, above the Atlantic, I thought, how complicated? How well do we understand this? I hope the answer is really well. So I'm looking forward to today's conversation. Good. Well, this question actually came to me from a listener,

Tom Johnson from Ohio, wrote to me and asked if we could explain why planes fly, because he looked into a little bit and he was kind of confused. So he wanted a clear explanation for why it is that planes stay in the air. And if you have a question that you want to ask us, we would be happy to answer them. So send us an email at questions at Daniel and Kelly.org. When I told Tom that we were going to answer his question on the pod, he said, quote, my wife is absolutely going to roll her eyes tonight when I tell her over sushi, which made me wonder, Tom is in Ohio? Where is he getting his sushi? Probably they have it flown in. So even his sushi relies on airplane wings. Yeah. And you know, I lived in Ohio for a decade or more. And I can tell you that when sushi has to fly that far,

It's not great. You're too far from the ocean at that point. You're saying nobody should fly to Ohio for sushi? No, I'd say that. I'm going to go on the record saying you shouldn't fly just to Ohio for sushi. Ohio's got other things going for it. You should have Ohio pride, you know? I know you're transplanted Virginia, but like you come from Ohio.

A good thing about Ohio, for example, is it made you. You know, I was actually born in New Jersey, which is an even harder state to defend. But I do actually love New Jersey, and I will defend. New Jersey. But, you know, Ohio was a very safe place to grow up where I grew up. And so that's fine. And I think Ohio has made the most astronauts. And so, you know, we all would make jokes about, you know, what is it about Ohio that makes you want to get as far as possible away from this planet? And I'm not sure if Ohio is still winning an astronaut production, but it was at some point. All right. Well, let's stop flying around the issue and get to the

question. I was wondering what people out there thought about how planes stay in the air, how wings work, what stories they had been told and what they understood about this question. So as usual, I went to our Bank of Volunteers to ask them, why do planes fly? If you would like to play for future episodes, please don't be shy. Write to us to Questions at Danielankelly.org. In the meantime, think about it for a moment. Why do you think planes fly? Here's what a bunch of listeners had to say.

I believe nobody really knows. I would be glad to learn otherwise. I know that I've read in my schoolbook that the air takes a longer way on the top of the wing than on the bottom of the wing and therefore we have a sort of suction going on that pulls the wing up. Planes fly because they want to

and because of the differential air pressure forces the air to take a longer path to go over the wing versus under the wing and this differential in the path length reduces the pressure on the upper surface of the wing, and that provides lift. There's some confusion surrounding the Bernoulli effect and the airflow speed over the top and bottom of the wings. There's lift, which means that the air going over the curved part of the wing takes longer

than the air going underneath the wing, so the lift is created there. It takes longer for the air to go over the top of the wing. The aerodynamics of that wing shape causes low pressure to form over the top of the wing and high pressure to form under the wing. So it wasn't it to do with Leonardo da Vinci came up with the original idea to base planes on the updraft from wings of birds? Planes fly because they can't swim. I think that light planes such as paper planes can't. contain flight just because of aerodynamics, but heavy planes need engines to generate pressure difference.

But I am not entirely sure how this works. So you have to have thrust greater than drag and lift greater than gravity. A higher pressure below and a lower pressure above. The top of the wing is curved, so the air has to travel further. I thought that planes flew because their Martian forwards caused air to flow over. air to flow over their wings and created a force that pushes up on the wings. So I think planes fly because of the way that the wind dens around the wing. Plains fly because the lift that they generate is greater than the gravitational pull.

The air has a longer way over the wing than under the wing. The top of the wing, because of its shape, it makes us. suction, so it sucks the plane up. I'm not actually completely sure why plane flies, but I know I've been in them, and they tend to do that, and I hope they continue to do so. I love that the answers were a combination of people who clearly sort of know what the answer is and like gave good answers, and then people who are hilarious. Because they can't swim made me laugh out loud. So Bravo. You know, I love that approach. You don't know the answer. Tell us a good joke. Yeah, absolutely.

That might be one of the keys to life, I think. I want to see that more of my physics exams, you know, when somebody doesn't know how to solve this quantum mechanical problem, hey, write me a good joke. I'll give you some points anyway. You would give points for humor. Sure, absolutely. I used to regularly have a question on exams that was just a random New Yorker cartoon, and then the question was write a physics-related caption for this cartoon. Oh, nice. I love that you're encouraging creativity.

I had an exam where I could get five extra credit points if I drew a parasite. And you'd think that that would be great. But I was like, I hate this because I don't even do nice stick figures. That's why I've married an artist. He takes care of all of it. But the good thing is there's a stage of parasites where they essentially just look like a circle. And so I just said, oh, there's a mediciacariusist. Done.

And I didn't get full credit. All right. So where do we start? So the beginning of the question of why planes fly goes all the way back to the right brothers in 1903. You know, the Wright brothers, they were engineers. They were not physicists. And so while the Wright brothers made a plane fly, they actually didn't understand it at the time. Like, they had no principles. They had no theory. They had no real reason to think their plane was going to fly. They just kind of made it work. And then they were showered, of course, with awards and fame and all

sorts of stuff, which led some people in the physics community to get a little bit resentful. So if they had no idea, why did they pick the design they picked? Is it because they were building on things that other people had made that maybe they understood what they were doing? And so they just sort of tinkered with that. Yeah, engineering is a lot of tinkering, right? So let's try this, let's try that. And sometimes things work.

And then later you figure out why that thing floats or why does this thing fly. And that's essentially what happened with the Wright brothers. And they won this fancy award from the Aeronautical Society. And one physicist, Colonel Fullerton, wrote in and said, quote, I think it was a mistake of the Aeronautical Society giving the rights of metal for their contribution to Aeronautical Science. I agree with their having the medal, but it should have been for what they have done. In other words, they didn't understand it. They didn't actually advance aeronautical science. They just sort of like made it work and they left open the question

of like, why does this work? I still feel like there should be a medal for the moment when you're about to like push your plane off the cliff and you're like, we don't understand what's going on, But he, ho! The Wiley Coyote Award or something. Maybe it's a subset of the Darwin Award, yeah. And this turns out to be really important politically because this is just before World War I, right? And so World War I is beginning. And we have nations trying to figure out, like, how to make planes fly, how to make them stable.

And nobody really understood, like, why some things work, how to make them better. And if you don't have, like, a model for why planes fly, it's pretty hard to improve their performance. And so just before World War I, you had all these folks in Britain and then also on the continent trying to understand the theory of flight so they could take advantage of it militarily. Okay. So the Wright brothers didn't have a theory and nobody else had a theory either. So everyone was just tinkering to see how it worked. And that it worked for the Wright brothers. Did the fact that it worked for the Wright brothers give insights into why it would work? Like, did their design work because it took advantage of some physics principle that became

obvious after the fact to the physicists? It certainly isn't obvious after the fact because people are still to this day arguing why planes fly. And it's fascinating that the divide in the field we're going to dig into this really goes back to the split that happened in World War I, where you had this sort of like mathematical battle between the scientists. You had the British trying to figure it out and you had the Germans trying to figure it out and they took different approaches. And those approaches still live on and do battle in science today, in modern aeronautical engineering. The Germans took this approach of thinking about air as a fluid flowing over the wing and analyzing the velocity and thinking about the pressure. But the British didn't

like that approach. It made some approximations that made them uncomfortable. And they liked using Newton's forces, Newton, of course, being British. And so to this day, we have two competing theories for why planes fly and how they work. It's fascinating to me that we still haven't figured this out. You're right. We had a working example about 100 years ago. And that definitely helps, right? It rules some things out. It inspires experiments. So how Having a working example is useful, but it doesn't always tell you exactly why something happens. So are these theories, which I'm sure we'll get into the details of in a second, are they different enough that that resulted in the British and the Germans having planes that had different shapes during World War I? Or do both theories sort of predict that the same plane shape is good?

Yeah, they make different predictions about what's important in the shape of the wing, which is fascinating. And I found this quote from a historian, David Bloor, who said, on the eve of the Great War, none of the British workers in the field of aerodynamics had any workable account of how an airplane could get off the ground, which, you know, makes it pretty hard to optimize the performance of your warplanes. And pretty scary to get into a warplane, on top of all the reasons that it's scary to get into a warplane. Exactly. And later on, we'll hear about Albert Einstein's personal design for an airplane, which really didn't work very well. So let's dig in. Should we start with the Germans, or should we start with the British?

So the German story is the one that most people have heard about. It's this theory of fluids and flow and Bernoulli's equations and all this kind of stuff. So we should start with air to make contact with what most people think about when they think about flight. All right. Let's do that. So the usual story for why plane flies has to do with the shape of the wing. And so aeronautical engineers call this an airfoil. It's roundy in the front and it's pointing the back.

It's sort of like a long, thin teardrop, right? And the idea that you're usually told is that the shape of this wing creates a pressure difference that you have lower pressure above the wing and higher pressure below the wing and that creates lift because higher pressure below and lower pressure above basically pushes up on the wing. And it's the shape of the wing that's crucial in creating these pressure differences, which is what creates lift. So that's the usual story for why planes fly that comes down to this particular shape.

of the wing. So you've got this curved edge moving towards the air quickly. Why does that shape not create the same amount of pressure on the top as it does on the bottom? Because that shape is like symmetrical, right? Is it because when it goes over it has more space to sort of spread out? So the shape is not actually symmetrical, right? Typically it's like flat on the bottom and more curved on the top.

And so the shape is not actually symmetrical, which is why the Bernoulli story tells you that it pushes up. Bernoulli is a guy in the 1700s who was thinking about fluid flow and mostly about like water through pipes and pressure and volume and like fluids are still something we're struggling to understand, but Bernoulli had a simplified view of it, which Euler actually came through later and proved all of his equations for him. But Bernoulli's principle tells us that faster moving fluids have lower pressure and slower moving fluids have higher pressure. So if the shape of the wing as it moves through the air, it makes the air go slower under the wing and faster above the lower, wing on this curved shape, then that'll generate lower pressure above the wing and higher pressure below the wing. And that gives you lift. And that feels easy to test, right? Because you just flip the wing over and it should do the opposite, right? Like it should send you plummeting

downwards? Yes, already you're identifying a problem with this. But before we take this explanation apart, let's do a little bit more to support it. Because you're right, it kind of is easy to test And you can do a simple test at home. You can just, like, take a piece of paper and blow air above the piece of paper. And what you see is the paper goes from being sort of droopy to being flat. So it sort of like lifts up. And so it's like a classic simple at home demonstration. What you're doing is you're increasing the velocity of the air above the paper,

which in theory lowers the air pressure above the paper, which provides lift because now the pressure is higher below the paper and lower above the paper. And, you know, this story of like the air moves faster over the paper. wing and slower below the wing is also verified in lots of other experiments like you can do these smoke tests where essentially you put a wing in a wind tunnel and instead of just blowing air over it you blow smoke over it smoke just being like a bunch of particles and you can track those particles and you can measure the velocity of the air around the wing see what happens right don't just like talk about it you know in your salons while you're smoking cigarettes or whatever actually figure it out and this is verified like wind tunnels and smoke tests tell you

us that the air does move faster over the top of the wing than below the wing. And so this seems like it all sort of comes together. But as you identified, there are some important limitations to this explanation of why planes fly. So when you get a window seat near the wing and you look out, it's easier to see. Like it's bunching up and it gets a little bit like kind of white-ish. Is that pressure forming? Like, are you sort of bunching up the air molecules to the point where they're visible or is something else happening there? Or am I imagining it? And this is like an episode of the Twilight Zone.

Nobody else sees that, Kelly. Yeah, exactly. It's just you. That was such a great episode. I love that. No, I think what's happening there is you're seeing more water vapor. There are definitely changes in the air pressure below and above the wing. And as you know, water is very sensitive to pressure, the vapor point and all this kind of stuff.

So what you're seeing there is not the air itself, but water vapor forming, which can show you just like in these smoke tests. can show you where the air is flowing. So that is pretty cool. That sounds obvious now that you say it. But I'm like, why did I ask that? But whatever, that's fine. Okay, so we decided now we're going to talk about the limitations. Has anybody flipped the wing the other way and then saw what happened?

Did that plane still fly? So planes fly upside down all the time, right? A big problem with this explanation is that it predicts that the asymmetry of the wing is crucial, right? That the curvy bit on the top compared to the flat bottom is really, important for making lift. And so it predicts if you flip that over, planes should like crash to the ground, right? That an upside down wing should have anti-lift or should have a net force downwards. But we don't see that. You know, you can fly planes upside down all the time. Everybody who's been to like an aeronautic show has seen old-fashioned planes or new planes, they can fly upside

down. So Bernoulli's equation doesn't answer this question. This can't be the complete story of why wings to provide lift because it gives the wrong explanation for upside-down planes. So you mentioned that Euler figured out all of these equations to support Bernoulli. Does it turn out that Euler's equations were missing some important factor? Because the equation said it should work, but then it doesn't work. So what was missing in the equations? Oh, yeah, great question. And this really goes to the heart of what's going on here.

There's nothing wrong with Bernoulli's equations. And I'm giving Euler credit only because Euler came along and, like, did all the math. Bernoulli had like these leaps of insight and like, oh, I think this and that and the other thing. And then Euler came along and actually like dotted all the eyes and crossed all the T's. And I think Euler would have gotten credit for these equations if he hadn't already gotten credit for like 80% of everything in mathematics. There's like so much of stuff in mathematics but like Euler just let somebody else take credit for because he's already got everything else named after him, which is amazing. So there's no problem with Bernoulli's equations,

but they're always a simplified description. Like Bernoulli's equations describe fluid flow and And they make some assumptions, like they're talking about a fluid as if it's incompressible, for example, or you're talking about it as if it's not made of microscopic particles. That's not true, right? Air is made of microscopic particles. It is compressible. That doesn't mean that the equations don't apply. It means that they apply in some limited sense. It also might just be the wrong story.

It might not provide the answer, the explanation. You know, what we're looking for is an answer to a question which is macroscopic. Like, we see the wing go through the air, the wing goes up. want to know why. That's sort of like a human question, right? It's not a mathematical question. It's not like there's a prediction and number we're trying to calculate. We want like a story that tells us why this is happening. And that's a little bit more slippery than just mathematics. It's something to do with cause and effect and understanding. And, you know, it's at the heart of science is coming up with these stories. But it's not always easy, especially when we're zooming

out from a microscopic universe to try to tell a story macroscopically. It's like economics. You know, you can ask like, why do prices go down? And well, I have this theory of inflation. I have a theory that involves prices and supply chains, whatever. And like, the theory can be correct, but it doesn't always apply because the conditions it assumes aren't always relevant. And it doesn't always answer the question that you're asking. I feel like the next time I get on a plane, I'm going to think to myself, I wish it were

simple. I wish we've really understood this. But planes tend to stay up. So that's good. So we've established that the Germans got everything wrong in World War. War I. Oh, wait, was that World War I or World War II? This is World War I we're talking about. All right. Well, they got it wrong both times. Sorry, guys.

I'm Dr. Scott Barry Kaufman, host of the Psychology Podcast. Here's a clip from an upcoming conversation about exploring human potential. I was going to schools to try to teach kids these skills, and I get eye rolling from teachers or I get students who would be like it's easier to punch someone in the face when you think about emotion regulation like you're not going to choose an adaptive strategy which is more effortful to use unless you think there's a good outcome as a result of it if it's going to be beneficial to you because it's easy to say like go you go blank yourself right it's easy it's easy to just drink the extra beer it's easy to ignore to suppress seeing a colleague who's bothering you and just like walk the other way avoidance is easier ignoring is easier denial is easier

Drinking is easier, yelling, screaming is easy. Complex problem solving, meditating, you know, takes effort. Listen to the psychology podcast on the IHeart Radio app, Apple Podcasts, or wherever you get your podcasts. Have you ever wished for a change but weren't sure how to make it? Maybe you felt stuck in a job, a place, or even a relationship. I'm Emily Tish Sussman, and on she pivots, I dive into the inspiring pivots of women who have taken big leaps in their lives and careers. I'm Gretchen Whitmer, Jody Sweeten. Monica Patton.

Elaine Welteroff. I'm Jessica Voss. And that's when I was like, I got to go. I don't know how, but that kicked off the pivot of how to make the transition. Learn how to get comfortable pivoting because your life is going to be full of them. Every episode gets real about the why behind these changes and gives you the inspiration and maybe the push to make your next pivot. Listen to these women and more on She Pivots, now on the IHeart Radio app, Apple Podcasts, or wherever you get your podcasts. The U.S. Open is here, and on my podcast, Good Game with Sarah Spain, I'm breaking down the players from rising stars to legends chasing history, the predictions, well, we see a first time winner, and the pressure.

Billy Jean King says pressure is a privilege, you know. Plus, the stories and events off the court, and of course the honey deuses, the signature cocktail of the U.S. Open. The U.S. Open has gotten to be a very fancy, wonderfully experiential sporting event. Listen, the whole aim is to be accessible and inclusive for all tennis fans, whether you play tennis or not. Tennis is full of compelling stories of late. Have you heard about Icon Venus Williams' recent wildcard bids? Or the young Canadian, Victoria Mboko, making a name for herself. How about Naomi Osaka getting back to form?

To hear this and more, listen to Good Game with Sarah Spain, an Iheart women's sports production in partnership with deep blue sports and entertainment on the IHeart Radio app, Apple Podcasts, or wherever you get your podcasts. Presented by Capital One, founding partner of I Heart Women's Sports. Culture eats strategy for breakfast. I would love for you to share your breakdown on pivoting. We feel sometimes like we're leaving a part of us behind when we enter a new space, but we're just building. On a recent episode of Culture Raises Us, I was joined by Volisha Butterfield, Media Founder, Political Strategist, and Tech Powerhouse for a powerful conversation on storytelling, impact, and the intersections of culture and leadership. I am a free black woman who worked really hard to be able to say that. I'd love for you to break down why it was so important for you to do C.

You can't win as something you didn't create. From the Obama White House to Google to the Grammys, Melicia's journey is a masterclass in shifting culture and using your voice to spark change. A very fake, capital-driven environment and society will have a lot of people tell half-truths. I'm telling you, I'm on the energy committee. Like, if the energy is not right, we're not doing it, whatever that it is. Listen to Culture raises us on the iHeart radio app, Apple Podcasts, or wherever you get your podcasts. Imagine that you're on an airplane, and all of a sudden you hear this.

Attention passengers. The pilot is having an emergency, and we need someone, anyone, to land this plane. Think you could do it? It turns out that nearly 50% of men think that they could land the plane with the help of air traffic control. And they're saying like, okay, pull this. Do this, pull that, turn this. It's just, I can do it my eyes close. I'm Mani.

I'm Noah. This is Devin. And on our new show, no such thing, we get to the bottom of questions like these. Join us as we talk to the leading expert on overconfidence. Those who lack expertise lack the expertise they need to recognize that they lack expertise. And then, as we try the whole thing out for real. Wait, what? Oh, that's the run right.

I'm looking at this thing. Listen to No Such Thing on the IHeart Radio app, Apple Podcasts, or wherever you get your podcasts. Okay, so we know that when a plane flips over, it doesn't go crash into the ground. What was he getting wrong? Bernoulli. So Bernoulli's story is very nice and it's very simple, and there's lots of it that's correct. But as you say, it doesn't explain some things. It doesn't explain why planes can fly upside down.

And it also doesn't explain something really crucial at the heart of the story, which is why is the air moving faster over the top of the wing than the bottom of the wing? Like we said the wing is asymmetric. It's curvy in the top and it's flat on the bottom. But why does that make the air go faster over the top? And you often hear this pop-side explanation, which is completely wrong, which is that it's a longer trip over the top of the wing. air has to go faster in order to, like, meet its air particle partners at the back end of the wing.

Why would it have to? Yeah, exactly. Why would it have to? It doesn't have to. It's nonsense. But you'd hear this all the time. I was taught this myself. You know, that, like, when air particles hit the front of the wing, if one goes above and one

goes below, then to meet up again at the back of the wing, the one that takes the longer route would have to go faster. And it's an example of, like, it's a compelling story, but it doesn't actually make any sense because they don't have to take the same time. It's fine. The universe doesn't like crash or implode or hit a Seg fault or something if the air particles don't meet up again. Yeah, right.

They're not like buddies. They don't have to get to the same spot at the same time. Yeah. All right. So that doesn't have to happen. So that doesn't have to happen. That's not the explanation for why air moves faster over the top. And so the Bernoulli story is sort of lacking that explanation.

Like why is there this pressure difference? And it opens this door to this question of like, well, did the speed? differences cause the pressure differences, or is it the pressure differences that are causing the speed differences? Because Bernoulli's equation doesn't give us causality. It just says lower pressure, higher speed. It doesn't say that lower pressure is caused by the higher speed.

It could also be the higher speed is caused by the lower pressure. So that tells us that we need more to the story. Bernoulli's story can't describe completely why planes fly because it doesn't tell us why planes fly upside down and it doesn't explain why we see air going faster over the top of the wing, which is something we definitely see happening. Right, so I know we're about to talk about another explanation, but does looking at birds help at all?

Because they have, you know, different kinds of wing shapes, and they've kind of figured it out over evolutionary time. This isn't going to give us the pressure answer, but does it give us some insights into, like, how these wings should be shaped? I'm getting off track, but I just looked at a picture of a bird in my office, and now I have to ask. It does, and bird wings work with similar principles to airplane wings,

except, of course, for the flapping. part. But for gliding, they do. Fascinatingly, insect wings are even more complicated. And insect flight is not something we understand like at all. It's really kind of incredible. We should do a whole other episode about why insects fly. And if you're ever feeling depressed, there are some slow-mo videos of insects trying to take off. And it is the most clumsy, amazing thing I've ever seen. It blows my mind that they ever get off the ground. And it makes my daughter laugh so hard. She pukes a little. So I knew a guy who did these experiments where they put an insect on a pin and like glued it to a pin and then they showed it videos so it was like thought

it was flying and they would like try to take videos of its wings moving to understand it. It's kind of incredible. All right. This has been an amazing tangent. I've had a lot of fun. Let's go back to World War I, which is less fun. So I think we've talked about the shortfalls in Bernoulli's explanation. Are we ready to move on to what the British folks were thinking? Yeah. So across the English channel, we had folks that are working on a completely different theory and not a completely different theory just because they disagreed scientifically with the best approach. Remember, there's a war here. And so they're not going to collaborate. They're not going to be like going to the same conferences and sharing their ideas. It's sort of like when evolution splits. You know, you get all

these weird animals off on an island and they diverge into their own crazy direction and get weird pouches for their babies or whatever. It's what happens when you work in isolation. You get competing explanations. And so we have this fascinating sort of social experiment where you like isolated two groups of scientists and asked them to solve the same problem. And they took very different approaches. So was it like allopatric speciation where they weren't encountering each other at all anymore? And that's why they come up with different theories because there was no cross talk. Or was it some Patrick speciation where the ideas could have flowed between each other, but they were still deciding to stay segregated. Was it nationalism or did they just not know,

is what I'm wondering? I think it started with nationalism, but then it developed into sort of tribal camps. And the Germans criticized the British and the British criticized the Germans. You know, even after the first war, when these guys could have gotten together and had like a global unified theory of flight, they continued working in their own direction because they were invested in it. You know, this guy's advisor told him that the German approach was nonsense and the German guy's advisor told him the British approach was schise, you know, or whatever. And so... Do you speak German? I do not speak German. I speak Danish, which is sort of Germanic a little bit.

Oh, cool. Do not speak German. Anyway, so the British, across the English channel, didn't like the German approach. They didn't like thinking about error as a fluid because they were like, this is too idealized. You can't explain what's really happening. The Germans thought, you know, ideal fluids are a fine approximation, but the British didn't like it. And, you know, anytime you're making an explanation in science, you're going to be making approximations. It's just a question of what approximations you make.

There are always shortcuts. Nobody can completely describe the full complexity of the universe in their equations. It's always a simplification. and there's an art to that, choosing the simplification that captures the essential details of what's happening in reality so you can provide a useful explanation while dismissing all the irrelevant complexities that you don't need to worry about, which is why, for example, we can talk about how a ball flies through the air and often ignore air resistance and ignore the quantum effects and ignore everything else that's happening, the tug of Jupiter on that ball, because we judiciously choose what approximations to make.

So that's what's happening here is two subjective approaches. And the British were focused not on this ideal fluid approach, but instead on using just a simple approach with Newton's law. They were just thinking about the forces. How do forces act differently on the top and the bottom based on that teardrop shape? Yeah. So the Newton's approach basically ignores the teardrop shape. And it says the shape of the wing isn't actually important. What's crucial is the angle of the wing into the wind.

So they're thinking, hey, the wing is tilted a little bit. And so as the wing is moving through the air, the wind gets bounced basically off the wind and goes down. So you have wind flowing onto the wing and you have an angle and then it bounces down. And so the wing goes up. And like anybody who's ridden in a car and put their hand out at an angle knows that you can feel lift, right? Your hand basically flies. And your hand is not a tear drop. It's not an airfoil.

It's not like carefully, germanically engineered to get lift. It's just your hand, you know, but still you can get lift. This is a simple application of Newton's theory, like action reaction. The wind gets pushed down by the angle of the wing. The aeronautical engineers call it the angle of attack. And so the wing gets pushed up, very simple. So if that's true, then you could adjust wing shape to be even better at flying by making it bend even more so that you're stopping even more air as you go. Did the British try that to prove how much better they were?

I wish you'd been around in the aeronautical society. So clear with your questions. So what you're describing is actually what you see in an airplane when you take off. If you're paying attention to the wing, modern airplanes actually have a changeable shape, right? They have these flaps and these levers, right? So they can change the shape of the wing. And during takeoff, they do just that. They push down the back of the wing.

So it's more of a curvy shape. It like grabs the air a little bit more. So you get more lift during takeoff. And then when you're flying, they make it flatter. So you're cruising, you get less lift. but you also get less drag. Drag is the force that pushes the wing backwards. So you want upwards-force lift

without as much backwards-force drag. So what you're seeing is exactly what modern airplanes do is they make it curvier when you take off to get more lift. Very cool. I was reading about programmable matter and I think one of the proposals was to have matter that responds to the environment

and makes those changes on its own without you needing to do anything. But I am glad we have more control over the process right now. I'm not ready to have us let go of that control yet. And the nice thing about this explanation is it explains why planes can fly upside down. They fly upside down because they have the right angle of attack. It doesn't matter the shape of the wing at all. It just matters that the airplane wing is at the correct angle.

So if you fly your airplane upside down, you can do it as long as the wing is angled into the air at the right angle. So does this completely explain everything? That's never how our podcast episodes end. So what is it missing? So this is a beautiful story of the limitations of science because both explanations explain something, but neither of them tell the complete story. So for example, there's a couple of things

that the British Newton's theory force explanation doesn't describe. Number one is what's going on on the top of the wing, right? This just focuses on the bottom of the wing, but we see that the pressure is lower on the top of the wing. The Newton's theory approach says all the lift comes from below, that you're getting this force from the wing, wind that's hitting it from below. But we see this lower pressure above. And it turns out, as we'll

talk about later, that it contributes maybe even more to the lift, the low pressure above the wing, than the high pressure does below the wing. And the Newton's theory cannot explain this. That's number one. And it can't explain why there's low pressure above the wing, right? Just like the other one. Yeah, exactly. Number two is that if you do these smoke studies, we see that the wing affects the flow of the air, not just below the wing. It's like the influence of the wing on the air. is larger than just the wing. Like the air begins to flow up above the wing before it hits the wing.

There's this upwash in advance of the wing and this downwash after the wing. So it's not just like you have a paddle and it's being hit by molecules and it's getting pushed up. There's a complicated interplay here between the wing and the flow around it and the air itself applying pressure on itself.

So you can't ignore the sort of fluid effects of the air if you want to completely describe what's happening. Yeah. So while you were describing all of that, I thought, oh, man, it really feels like fluid dynamic should have explained that. So maybe the German example should have worked. Why does the fluid example not work then with all of that complicated stuff happening? So the fluid example does explain some parts of it. And so where we're going to go in the end is this like weird hybrid of the British German theory in order to have the most complete explanation of why it happens. But what we're doing right now is sort of examining like the failure of the individual ones. So the German explanation, the fluid is. approach can describe the flow of the fluid around the wing. But the British approach, though it's simple and satisfying, can't describe all of this stuff. Okay. Spoiler alert. Yeah. So one thing it fails to describe is a sort of holistic flow of the air around the wing. The other is stalling. And the Newton's force approach, the only reason you're flying is the angle of attack and the greater the angle, the greater the force, right? But anybody who flies knows that if you have too great an angle,

you're going to stall. Like if your plane is pointed too far upwards, you're not going to get lift anymore. And what happens technically, what we see in wind tunnels is that if the angle of attack is too great, then as the air flows over the top of the wing, it doesn't merge smoothly with the air flowing below the wing.

And you get this weird turbulence. They call it a separation region because the air doesn't nicely reconnect. And, you know, when you're going through a fluid, turbulence is a problem. You want to minimize turbulence. And so if the angle is too large, this is like gap between the air flows as they come off the back of the wing, and they don't merge nicely. That's called the separation region between these flows, and that creates the stalling.

You lose your lift. So you can't explain that also with the Newton's explanation. You need some fluid theory to explain that. Slightly tangential. We haven't discussed propellers. Do propellers and jet engines play any role here, or is that just in like, that moves us forward and all of the uppiness? comes from the wings. Yeah, so basically engines just provide forward velocity so that the wings attack the air.

Although propellers are a subtle point because propellers have a particular shape which is related to the shape of a wing, right? Because it's converting motion in one direction to air velocity in the other direction. So the shape of a propeller is related to the shape of a wing. But for the question of why planes fly, you can think of it just like something pushy, right? The pushy bit that gets the plane moving through the air. Yeah. Okay.

So you've got the pushy bit, but we don't understand what's happening around the wings yet. So how do you move from figuring out that both the German and the British explanation are failing in some way to figuring out the answer to what's going on? Is this like where we are? We just don't know. Or are there more experiments you can do to figure it out? So what you shouldn't do is ask the world's smartest physicist Einstein to weigh in on this very practical engineering question. Well, let's find out what he had to say after the break.

I'm Dr. Scott Barry Kaufman, host of the psychology podcast. Here's a clip from an upcoming conversation about exploring human potential. I was going to schools to try to teach kids these skills, and I get eye rolling from teachers or I get students who would be like, it's easier to punch someone in the face. When you think about emotion regulation, like you're not going to choose an adaptive strategy, is more effortful to use unless you think there's a good outcome as a result of it, if it's going to be beneficial to you. Because it's easy to say, like, go you, go blank yourself, right?

It's easy. It's easy to just drink the extra beer. It's easy to ignore, to suppress, seeing a colleague who's bothering you and just, like, walk the other way. Avoidance is easier. Ignoring is easier. Denial is easier. Drinking is easier.

Yelling, screaming is easy. Complex problem solving, meditating, you know, takes effort. Listen to the psychology podcast on the IHeart Radio app, Apple Podcasts, or wherever you get your podcasts. Have you ever wished for a change but weren't sure how to make it? Maybe you felt stuck in a job, a place, or even a relationship. I'm Emily Tish Sussman, and on she pivots, I dive into the inspiring pivots of women who have taken big leaps in their lives and careers. I'm Gretchen Whitmer, Jody Sweeten. Monica Patton.

Elaine Welterah. I'm Jessica Voss. And that's when I was like, I got to go. I don't know how, but that kicked off. the pivot of how to make the transition. Learn how to get comfortable pivoting because your life is going to be full of them. Every episode gets real about the why behind these changes

and gives you the inspiration and maybe the push to make your next pivot. Listen to these women and more on She Pivots, now on the IHeart Radio app, Apple Podcasts, or wherever you get your podcasts. The U.S. Open is here. And on my podcast, Good Game with Sarah Spain, I'm breaking down the players from rising stars

to legends chasing history, the predictions, will we see a first-time winner, and the pressure? Billy Jean King says pressure is a privilege, you know. Plus, the stories and events off the court, and of course the honey deuses, the signature cocktail of the U.S. Open. The U.S. Open has gotten to be a very fancy, wonderfully experiential sporting event.

I mean, listen, the whole aim is to be accessible and inclusive for all tennis fans, whether you play tennis or not. Tennis is full of compelling stories. Have you heard about Icon Venus Williams' recent wildcard bids or the young Canadian, Victoria Mboko, making a name for herself? How about Naomi Osaka getting back to form? To hear this and more, listen to Good Game with Sarah Spain, an Iheart women's sports production in partnership with deep blue sports and entertainment

on the IHeart radio app, Apple Podcasts, or wherever you get your podcasts. Presented by Capital One, founding partner of IHeart Women's Sports. Culture eats strategy for breakfast. I would love for you to share your breakdown on pivoting. We feel sometimes like we're leaving a part of us behind when we enter a new space, but we're just building. On a recent episode of Culture Raises Us, I was joined by Volisha Butterfield, Media Founder, Political Strategist, and Tech Powerhouse for a powerful conversation on storytelling, impact, and the intersections of culture and leadership. I am a free black woman who worked really hard to be able to say that. I'd love for you to break down why it was so important for you to do C.

You can't win as something you didn't create. From the Obama White House to Google to the Grammys, Belisha's journey is a masterclass in shifting culture and using your voice to spark change. A very fake, capital-driven environment and society will have a lot of people tell half-truths. I'm telling you, I'm on the energy committee. Like, if the energy is not right, we're not doing it, whatever that it is. Listen to Culture Raises us on the IHeart Radio app, Apple Podcasts, or wherever you get your podcasts. Imagine that you're on an airplane and all of a sudden you hear this.

Attention passengers. The pilot is having an emergency and we need someone, anyone, to land this plane. Think you could do it? It turns out that nearly 50% of men think that they could land the plane with the help of air traffic control. And they're saying like, okay, pull this, do this, pull that, turn this. It's just... I can do my eyes closed. I'm Mani. I'm Noah. This is Devin.

And on our new show, No Such Thing, we get to the bottom of questions like these. Join us as we talk to the leading expert on overconfidence. Those who lack expertise lack the expertise they need to recognize that they lack expertise. And then, as we try the whole thing out for real. Wait, what? Oh, that's the run right. I'm looking at this thing. See?

Listen to No Such Thing on the I Heart Radio. app, Apple Podcasts, or wherever you get your podcasts. All right. So for most of the Daniel-led episodes, we have to walk through a what did Einstein think because he just provided so many good insights into so many things. So let's figure out what did Einstein think about this? Yeah, so Einstein, he's a smart guy. He developed relativity.

He struggled and failed to integrate quantum mechanics into it. So it's not like he solved every problem he attacked. But he was a smart guy. And, you know, he was German. And this is a relevant question for the Germans at the time. And he was interested in this. And he wrote, quote, there's a lot of obscurity surrounding these questions. And open puzzles like this, you know, they attract smart people.

Like, oh, maybe I can figure this out. Maybe there's an insight, a moment of clarity that will just untangle this whole mess. And so he thought about flight from the German point of view. And he actually designed his own wing shape, sort of a weird variation on the airfoil. So this is Einstein. Remember, he was not just a clever physicist. He worked in the patent office. And so he had seen lots of inventions.

He had a practical mind also. So he designed his own wing and he took it to a German aircraft company. And, you know, he was an esteemed famous scientist at this point. So they thought, okay, sure. So they worked with him. They collaborated with him. They built the plane and they sent it out. on a test flight. And the pilot came back and said he would never fly the thing again because

it, quote, flew like a pregnant duck. I feel like whenever a question sort of tiptoes into biology and Einstein is involved, you want to back away. So, you know, I think maybe most of us know that ducks can't get pregnant. They carry eggs, but they don't get pregnant the way we do. And also, like, you know, he married his cousin, which I think is a bad idea, also from a biological perspective. But anyway, okay, so Einstein was great at everything, but not at designing wings. Yeah, exactly. And so fast forward 50 years or so, what are people talking about today in terms of why planes fly? I went across campus here to a colleague at UC Irvine, Hatham Taha. He's a professor of aeronautical engineering here, and he studies Lyft. He works on this problem. I asked him,

what is a simple explanation for Lyft? And he said, quote, this is not settled in the aeronautical engineering community, please don't laugh. That's a direct quote. So here we are laughing. It's hilarious, you know, like these guys still haven't figured this out more than 100 years after their Wright brothers. But yet still so much money is made on flight. So it's nice to know you don't have to have everything worked out before you commercialize something. But let's not oversell it. It's not that we don't understand why planes fly. It's that we don't have a compelling, simple explanation at the sort of zoomed out level. And again, there's always a difference between like the microphysics. Can you model what's happening with individual air molecules

and the shape of the wing and come up with a simulation in which planes fly? Absolutely we can. And we do. This is why, for example, Boeing can design their airplanes on the computer and be confident that they will fly. They don't need to use wing tests anymore and build a bunch of models to experiment because we have accurate simulations for what's going on and the microphysics level. It's just that when you zoom out and now you want to tell a simple story about what's happening, there are competing ways to do that and all of them ignore some details and so none of them are completely satisfactory.

So when he says this is not settled, he doesn't mean we don't know why planes fly in a sort of microphysics point of view. He means we don't have a nice compelling one sentence explanation for why this happens the way we can, for example, like a ball flying through the air. Why does a baseball fly in a parabola? We know the answer is when you have constant acceleration,

you get parabolic motion. Simple one sentence answer. That's what we're lacking for flight. We have a very complex thing that's happening with microphysics, and it's when we're struggling to come up with a simplified explanation at the macroscopic level. Do engineers care? So if you can make a simulation on a computer that tells you everything you need to know, are engineers still interested in this question,

or has this completely moved to the realm of, like, physicists who never see the light, who are studying it in their offices? Like, yeah, do they care what the answer is anymore, or do physicists care only? Absolutely, they care because engineers want simple working models. You know, when they want to model how a plane is going to fly, they don't want to have to go back to describing every single particle. They want simple sets of equations that let them work quickly and easily. The same way, for example, we'd love to be able to predict a hurricane without modeling every single raindrop. Currently, we have the technology and we're building these incredibly powerful computers just to model wind and pressure and predict the weather.

we'd love simple equations to be able to do that, right? Rather than having to use incredibly detailed computation. And so anytime we can summarize complexity with simple math, we definitely win. So people are definitely working on this and trying to find a complete holistic approach that captures all this behavior that lets us do important engineering without simulating all of the tiny microphysical details. Absolutely. Yeah, people care.

And I want to go on record that I apologize for implying that physicists don't go outside. What is this outside thing you're talking about? I was going to ask you about that. I've heard about this, but I've been too shy to ask. You told me you've been hiking. I know that you're maybe even more extreme than I am in terms of outdoor adventures. No, I do love going outside. That's why I live in California.

It's so amazing here. Oh, the fall right now is absolutely incredible. Okay, so we've talked about a lot of different ideas, a lot of things we know and we don't know. I know the answer at the end is that it's complicated, but is there a sense? simple-ish kind of way to summarize where we are right now in our understanding. Yeah. So I think the simplest way to describe it is that both of Bernoulli and Newton's stories help, but they're both limited. And the limitation is that they're trying to tell a story in terms of like simple causes and simple effects. The air flows and it bounces off the wing or the pressure

is lower above the wing because the velocity is higher. And the real story is that the cause and effect are not so simple. There's lots of things happening here and they're interplaying together. So it's not so easy to disentangle the cause and the effect. There's a lot of things at work here, pressure and velocity and forces all in this fantastic harmony that's making the wing go up, which is why none of these simple stories are satisfactory. We can weave a slightly more complex story to explain why planes fly that involves all of these aspects sort of working together. But, you know, humans like simple stories. Ball goes down because of gravity, this kind of thing. We don't have that simple a cause and effect.

amazed by things that work so well where when you scratch the surface, we really don't understand. Like, I was talking to someone who uses deep brain stimulation to treat epilepsy. So, like, when somebody has a seizure, they're having, like, an electrical storm in their brain. And sometimes they have electrodes implanted into the center of their brain, and they essentially just get their brain zapped. And that helps. And so I reached out to an expert, and I was like, why does zapping someone's brain with electricity stop the epileptic seizure? And they're like, we don't know. Just like I am a little nervous getting onto a plane hearing, why does the plane go up? We don't know.

I also would not want to hear, why are you shocking my brain? We don't know. But in both cases, it works and it seems to work reliably. So we get by. Also, true, I think, for most pharmaceuticals, right? We're like, well, it does have this effect. We don't really understand the biochemistry of it. But, hey, keep taking it, you know?

That's right. Yes. We all muddle along. And I'm not an anti-vaxxer at all. I just mean this is sort of the way science is. You always understand science at some level. You don't always need to understand the microphysical explanation in order to make it work. And that's actually a huge gift.

Otherwise, we couldn't do anything. If we needed to understand, like, the nature of quantum gravity before we made a bowl of chicken soup, we'd never have chicken soup. We never understand the world. It's lucky that the world can be understood without knowing all the details or science would be impossible. It's lucky you can tinker with the world without understanding it. Yes, that too. So we do have a story we can tell about why planes fly. And I think the best way to think about why a wing goes up is to focus on pressure, pressure above the wing and pressure below the wing.

Fundamentally, a wing goes up because pressure grows below the wing and pressure falls above the wing. And both of these are contributed to by the Bernoulli and the Newton's story. Got it. Okay. We managed to summarize something in like three or four sentences. But we can also dig into it in a little bit more detail. You know, like why does pressure grow below the wing? Well, Newton tells us to focus on the angle of attack, right?

And that's correct. The wing goes through the air and the angle of attack pushes down in the air and the air pushes back. And this is pressure. Just like if you're scooping up snow with a snow shovel, right? This is going to be increased pressure. The snow is going to get compacted. So why does pressure form below the wing? Not that controversial. It's the angle of attack. That's crucial. And as long as you go like this and you just don't look at the top part of the wing and so I'm covering the top part of my eyes and you don't think about the top part of the wing that everything is good. But we don't understand what's happening above. Is that right? Well, above the wing, we can also think about the pressure. The Newton story can't explain what's happening, but if you think about it in terms of fluid, you can, right? So what's happening above the wing? Initially, if you just, like, shoot air above the wing, then it wants to flow straight back, which effectively creates like a vacuum underneath.

The angle of the tack working together with the shape of the wing creates this low pressure zone above the wing because the air needs to go down to flow onto that, right? So that's exactly what happens is you create this low pressure zone, which is like a vacuum. It pulls the air into it. and that's pulling the wing up. So you have low pressure above the wing created by the shape of the wing and the angle of attack,

which creates low pressure above it. And so these two effects work in harmony. You have a force from below and you have like suction from above. So wings go up not just because the air below them is pushing them up, but the air above them is sucking them up into the sky. So the Germans got the top right

and the British got the bottom right? Is that right? I feel like there's so many times where I hear that there's a debate and there's people on this side and people on that side. And five years later, the answer is almost always, oh, they were both right. It's some combination of things. But okay, cool. Yeah. And so mostly this comes from the shape of the front of the wing right now. The shape of the wing is important because you want to minimize drag. The Newton folks tell you the shape doesn't matter. All that matters is you get the force

from the bottom. But what you want is to create low pressure on the top without creating a lot of drag and without creating this turbulent zone, which gives you a stall. So that's why you have this shape. You have this shape in the front of the wing to give you this uneven pressure distribution. So you get low pressure, but not so much that you get a stall. And then you have this smooth endings so the flow comes together nicely without creating turbulence at the end. So the shape of an airfoil in the angle of the attack is optimized to give you smooth flow,

low pressure above the wing, and to minimize drag, which is important if you want to take off. I feel like the next time I get on a flight, I'm going to appreciate it all, much more, having a better sense of how this all works. But you know, in terms of coming to this explanation, the experts still are arguing about like how to summarize this. I've given you sort of a summary version of it, but I'm sure there are aeronautical engineers out there who have differing opinions and are going to write into us with their theory for why planes fly, or at least for how to describe it. Our original listener, Tom Johnson, wrote in because he saw this video from the Smithsonian Air and Space Museum that explained it in terms of just Bernoulli,

right? The Bernoulli explanation of low pressure on top. And he wasn't satisfied with this. And he wrote to me and he said, quote, I contacted the Smithsonian about this video, voicing my concerns. And I was told unequivocally that it's their policy that Bernoulli makes planes fly. I wasn't aware that physics cared about policies, but I guess I'm mistaken. That's amazing. Institutions are fantastic. Exactly. And so again, you know, while the microphysics is clear about what's happening around the wing and you can track these individual particles, we still do struggle a little bit coming up with a simple explanation. It turns out pressure is important and velocity is important and the forces are important. So none of the sort of classic simple explanations can describe everything that's happening around a wing. You need a more complex, a fuller description of what's happening to explain all the phenomena. Why planes can fly upside down, why the pressure. goes down above the wing, all this kind of stuff. So in the end, the British and the Germans have to work together.

Oh, I mean, that's better in the end. So those plain wing shapes, so I'm thinking of other instances where you've got like things moving through the air. So we've got like wind turbines and then you've got racing cars. They don't want to go up. They want to go down. So they do the whole shape in reverse. Like how has this information been used in other contexts?

Yeah, exactly. So Formula One cars, they have a wing in the back. But that wing pushes the car down so that it maintains friction because they need friction in order to go forward, right? The wheels have to get pushed onto the ground so the wheels can grab. And then when they turn the wheels, the car goes forward. If the car lifts up above the ground, then it can't move forward anymore. So they designed it in order to generate downward pressure. So they have crucially a different angle, right?

But they also think about the foil and they do really complex modeling because, you know, millions of dollars mean microseconds. and it's a difference between winning and losing. So, yeah, absolutely, they invert all of this theory in order to get a wing that can push down. And the crucial thing there is the angle of attack, right? And then wind turbines, they don't want the wind turbine to go airborne, but they want it to spin as fast as it can, which feels like maybe some of the principles we talked about today

could help that happen. Yeah, how does this plan to wind turbines? Yeah, exactly. Well, it's the same principle, essentially. You have airflow across the propeller, and you want to convert that to a sideways force, right? So you want to force up relative to the propeller. You don't want the whole propeller to fly up off the ground, right?

But you want it to spin around the axis. And so, again, the angle of attack and the shape of it ensures a force that turns it and smooth flow around it. Because you don't want turbulence at the back of your propeller blade. So each one of those is essentially just a little wing. Very cool. I'm guessing that we weren't racing cars before we had. planes. So probably the plane stuff came first. Yeah, the plane stuff came first. Cars were pretty slow until kind of recently. Like you could win big car races by driving at like 45 miles an hour

for many years. That sounds so cute now. But it's much harder to die at that speed. Why would you watch that? But it's really fun to think about how we explain the world around us and how challenging it can be to explain some things. It makes me really grateful for the times that we can find a very simple explanation and wonder like why that's possible sometimes and not other times. Is it because of the way that we think about the world? Or is it just something about the way the world works? You know, alien scientists have a better theory for why wings work because they started off from a completely different point of view mathematically or scientifically, or is everybody struggling to describe some complex behaviors? Are these things just inherently

complex or is it just our language that's making them a challenge? I wonder if part of that is there's some percent of explanations that we have that we feel good about that are actually wrong if you look at them more closely, but the stuff works anyway. Yeah. And then I wonder if some other stuff just there happens to be a metaphor that we're familiar with that makes it easier to understand. And there's just not like a ready metaphor for some of the more complicated things. Yeah.

And sometimes we accept an explanation, even though it's nonsense. Like the air has to go faster over the top of the wing to meet its partners. Like a lot of people go, oh, yeah, that makes sense. But it doesn't actually make sense. you know and fundamentally all of science is quote unquote wrong if you zoom in far enough you know everything is just an approximate description not like scientists are lying to us or we're promoting nonsense but everything is an approximation even like describe an electron as a fundamental particle yeah probably it's not probably it's made of something smaller we just haven't seen it

yet but our theory works so far we've never been able to make an experiment where it breaks And so all of science is a work in progress in that sense, not just like, do we have the best explanation for it? But, you know, how far can we push this until we see it break? And seeing it break is an opportunity, right? It's not a disaster. It's a chance to learn something deeper about the universe to come up with a more accurate description or to poke through reality to another level and see how it works underneath it all. So it's just part of the journey of science. I feel like it's a great time to be in science.

There's still so many fundamental things left to understand. at the same time as we're gaining all this new technology that allows us to address questions in different ways. We have all these new tools. Can't wait to see what we learn in the next couple decades. Yeah. And it's not just like what's inside an electron, like weird abstract fundamental stuff that you'll ever see. It's stuff right in front of you, stuff you can see with your eyes, you know, tornadoes and hurricanes and airplanes and fluid flow. All this stuff is complex and unsolved. So smart young people with energy out there, go out there, figure it out. There's lots left to do. So thank you very much to Tom Johnson for sending us this question. If you have questions

about the way the world works or why you can't understand it, please write to us to questions at danielandkelly.org. We love to hear from you. Thanks, Tom. Daniel and Kelly's extraordinary universe is produced by iHeartRadio. We would love to hear from you. We really would. We want to know what questions You have about this extraordinary universe. We want to know your thoughts on recent shows, suggestions for future shows. If you contact us, we will get back to you. We really mean it.

We answer every message. Email us at questions at danielandkelly.org. Or you can find us on social media. We have accounts on X, Instagram, Blue Sky, and on all of those platforms, you can find us at D and K Universe. Don't be shy. Write to us. Why are TSA rules so confusing?

You got a hood of you. I'll take it all! I'm Mani. I'm Noah. This is Devin. And we're best friends and journalists with a new podcast called No Such Thing, where we get to the bottom of questions like that. Why are you screaming? I can't expect what to do.

Now, if the rule was the same, go off on me. I deserve it. You know, lock him up. Listen to No Such Thing on the IHeart Radio app, Apple Podcasts, or wherever you get your podcast. No such thing. I'm Dr. Joy Harton-Bradford, host of the Therapy for Black Girls podcast. I know how overwhelming it can feel if flying makes you anxious.

In session 418 of the Therapy for Black Girls podcast, Dr. Angela Neal-Barnett and I discuss flight anxiety. What is not a norm is to allow it to prevent you from doing the things that you want to do, the things that you were meant to do. Listen to Therapy for Black Girls on the IHeart Radio app, Apple Podcasts, or wherever you get your podcast. From tips for healthy living to the latest medical breakthroughs, WebMD's Health Discovered podcast keeps you up to date on today's most important health issues. Through in-depth conversations with experts from across the health care community, WebMD reveals how today's health news will impact your life tomorrow.

It's not that people don't know that exercise is healthy, it's just that people don't know why it's healthy, and we're struggling to try to help people help themselves and each other. Listen to WebMD Health Discovered on the IHeart Radio app, or wherever you get your podcasts. It's important that we just reassure people that they're not alone, and there is help out there. The Good Stuff Podcast, season two,

takes a deep look into One Tribe Foundation, a non-profit fighting suicide in the veteran community. September is National Suicide Prevention Month, so join host Jacob and Ashley Schick as they bring you to the front lines of One Tribe's mission. One Tribe, save my life twice. Welcome to Season 2 of the Good Stuff. Listen to the Good Stuff podcast

on the Iheart Radio app, Apple Podcast, or wherever you get your podcast. Every case that is a cold case that has DNA. Right now in a backlog will be identified in our lifetime. On the new podcast, America's Crime Lab, every case has a story to tell. And the DNA holds the truth. He never thought he was going to get caught.

And I just looked at my computer screen. I was just like, ah, got you. This technology's already solving so many cases. Listen to America's Crime Lab on the IHeart Radio app, Apple Podcasts, wherever you get your podcasts. This is an IHeart podcast.