Science Friday - Diets, Crowd Physics, Snowflake Citizen Science. January 4, 2019, Part 1

Episode Date: January 4, 2019

Earlier this week, hundreds of thousands of revelers huddled together under the pouring rain in Times Square for an annual tradition: to watch the New Year’s ball drop. But once the clock struck midnight, the song was sung, and the loved ones were kissed, all anyone wanted to do was get out of there. The problem? How does a mass of 100,000 people move out of a few square blocks in midtown Manhattan? Luckily, scientists are studying this type of problem. Stanford University professor Nicholas Ouellette joins Ira to discuss the weird world of crowd movement. From low-carb, high protein, calorie counting, there are all sorts of diets that claim to help you lose weight. But how do all of these guidelines affect our metabolism and bodies? A study out in the British Medical Journal found that a reduction in carbohydrates increased energy expenditures. Endocrinologist David Ludwig, an author on that study, talks about the role carbohydrates, fats, and proteins play in regulating our metabolism and how we might rethink our calorie counting. Plus: Lake Tahoe scientists are enlisting local citizens to better understand winter storms. Capital Public Radio's Ezra David Romero joins Ira in the latest edition of The State Of Science. And FiveThirtyEight's Maggie Koerth-Baker tells Ira about China's Chang'e-4 mission and other top science stories in this week's News Round-up.   Subscribe to this podcast. Plus, to stay updated on all things science, sign up for Science Friday's newsletters.

This is Science Friday. I'm Ira Flato. Later in the hour, keto, paleo, Mediterranean. How do these diets affect your metabolism? But first, a moon goddess and a jade rabbit are now actively exploring the far side of the moon. China's latest moon lander and rover, both named after previous Chinese moon missions. They made history touching down this week in the Van Carman Crater, part of the moon's oldest, deepest basin. And it's a technical feat that marks a new frontier in space exploration and Chinese exploration. Here to talk about it and more selected short subjects in science is my guest, Maggie Kerth Baker, senior science reporter at 538.com. Welcome back, Maggie. Hi, thanks for having me.

Let's go to that first story, the China's moon landing on the far side of the moon. Yeah, so this is the first human spacecraft to land on the part of the moon that we can't see from Earth. It's not technically the first human spacecraft to hit that part of the moon. That would be Ranger 4, but that doesn't really count because it crashed there unintentionally after a system failure in 1962, and we didn't get any data from it. So this is the first intentional landing on the far side of the moon. We've heard, of course, Pink Floyd call it the dark side of the moon, but it's not really dark. No, it's not.

In fact, you could argue that the side we see is sort of the dark side, because one of the things that makes these two sides different is that the side of the moon that we see most of the time has these really big, smooth, dark patches, the face of the man in the moon, right? The other side is a lot more pockmarked, a lot more lumpy, and a lot paler all over. And that seems to be because when these ancient asteroid impacts were sort of shaping what we see on the moon today, they unleashed these lava flows on the side of the moon that faces us. So those lava flows smoothed over the land around and darkened these patches. But it's not totally clear why the same thing didn't happen on the far side.

And that's one of the things that Chengi is hopefully going to tell us more about. If it's on the other side of the moon, and I've had people ask me this question, how do we get signals back through the moon to the earth? That's going to be an interesting thing. I know one of the things that they're doing research on over there is radio astronomy research, because it's actually a good place to do that because the mass of the moon sort of blocks a lot of the chatter that we produce just living around here on Earth. So getting things back is a bit of a challenge, but it is possible. And we'll be able to hopefully do some radio astronomy work we can't do from here or from the other side.

Don't the Chinese have a satellite going around the moon? It's sort of a relay station. for these landers. Yep, exactly. They relay the stuff back there. Second story, President Trump finally has a science advisor. Yes. Two years in.

Yep. Yeah. So for the first time since President Trump took office in January of 2017, the Office of Science and Technology Policy has a director. It's going to be meteorologist Kevin Drogamire. Yes, Kelvin, just like the temperature scale. He's got one of those really nice names that line up with his job. He is a former vice president of research at the University of Oklahoma.

And he's been active in research policy at the national level for years. He used to serve on an oversight body for the National Science Foundation. His research is kind of coming from storm prediction, which is this big specialty down in Oklahoma for obvious reasons. He's one of the first people to show how Doppler radar could be used to predict storm formation, for instance. So all the times that you see meteorologists on TV using Doppler radar to tell you when a storm is, is likely to become a big deal in your area, that's kind of coming out of research from people like Kelvin Drogomier. So he's not a climate denier, then?

Well, so we don't know. There's a lot we don't know about his positions on climate change. The scientists that have been big climate activists in the past that have been pretty positive about him, but it's not really clear exactly what his position on this is. Science magazine found a speech that he gave in 2014. where he kind of gave this confusing space in the middle, you know, essentially saying that observation show us the planet is warming, evidence says it's human caused, but also we don't know everything,

and the planet could probably get kicked really hard and recover. So it's kind of, it kind of seems like he sort of plays a middle line there. Yeah, well, we'll find out. Hopefully he'll come on the show. Talk to us about it. Yeah. We can talk them into it. Your third story today is about where all our used plastic is going.

Yeah, so about this time last year, you probably remember that China announced it would stop taking in so much of our discarded plastic. And this was the country that had been taking about half of the world's recycled plastic and paper. But in the last year, they have cut those imports by 94%. So the UK released a report this week that was showing what was happening to their plastic waste. And what's happening to their plastic waste is a lot of what's happening to the waste from the U.S. as well, it seems. And a lot of it's going to Malaysia. So both the BBC and LA Times are reporting that that country's taking in some of what China is rejecting. And also that it's taking in so much more than it was prepared to handle.

So there's a lot of the plastic waste that we send for recycling that's now getting burned or landfilled in Malaysia. Any solution to that? Well, it's kind of a complex thing. So you would think that plastic is worth something that we'd know we'd want to. recycle it and there'd be like a cash benefit to that. But that sort of harkens back to this other problem. So American recycling used to require that you clear these big personal hurdles. You know, we used to have to wash everything. We used to have to sort everything. And now a lot of us are encouraged to just dump it all in a single bin like trash. So our paper and our plastic,

they're more contaminated than is allowable under U.S. recycling standards. And those standards now exist in China, too. And there's this extra cost with sorting and cleaning. So this plastic that China is rejecting and Malaysia is accepting and in many cases burning is contaminated stuff that we couldn't process here. So it's too dirty. It's the wrong kind of plastic. And what experts say would help solve the problem is to get Americans back to a less convenient way of recycling, you know, spending more time washing those recyclables and sorting them instead of having just one big bin. And on a local level, there are a number of cities that have started banning plastic straws, right?

Yeah, that's definitely a thing. Cities in at least five states have laws that have passed or that are on the table. D.C. passed a law, the entire state of California. What's interesting about this is that it's all really based around those plastic straws. And it's not really clear how big of a difference that's going to make in terms of our volume of plastic use. Because this is going to come as a shock. We use a lot of plastic. And straws are kind of a tiny, you know, kind of a tiny.

tiny subset of that. But it's a beginning, right? It's an awareness. It's a beginning. And I think one of the things it does is also sort of show the complications, though, because one thing that's been pointed out is that, you know, we use plastic for a reason. And part of that is things like disabled people need those plastic straws for basic quality of life and survival. And band, like across the board bands end up affecting them in ways we don't expect.

All right. We'll keep following that. And we'll keep following you. Maggie, thank you for taking. to be with us today. Yeah, thank you so much for having me. Happy New Year. Maggie Kerth Baker, senior science reporter at 538.com. Now it's time to check in on the state of science. This is KERNO. St. Louis Public Radio News. Iowa Public Radio News. These are local science stories of national significance and whether or not your holidays had a coating of white to them,

you know that predicting a winter storm, predicting it can be challenging. Researchers have a lot to learn about what goes on in the heart of a snowstorms clouds. And there are a couple of ways to find out. One of them involves flying through the clouds. Another approach is trying to study the results of these storms, the snowflakes themselves. And that's what a snowflake school project aims to do and list a team of students to capture and photograph snowflakes. Joining me now to talk about the project is Ezra David Romero, an environment reporter

at Capitol Public Radio in Sacramento, California. He recently reported on the project. Welcome back. Hey, thanks for having me again. So tell us the point of this project. Well, the whole idea is that when an airplane goes up into the clouds, they can only get data from wherever that plane goes in that moment. But scientists at the Desert Research Institute in Reno want to expand that. They want data points from across the Sierra Nevada when a storm comes through.

So then they can get the information out to weather forecasters and ski resorts. and places like that to give them a bit more accurate information about what the snow looks like and the trends they're seeing. So they're training kids to do this, then? Collect the data. Yeah, they're out about something like between 15 and 19 schools this year. What they do is you have to have a smartphone, and lots of students do, and they give you a rubber band. And in the rubber band is an embedded magnifying glass, and you put that around your phone to line up with your camera. They give you a piece of felt on plastic, and you've got.

put that out in the snow until it's really cold. And when it snows, snowflakes fall onto it, and then you go out and you take a picture of it, and you upload it to an app. And then the scientists take that and collect all those pictures. And so there are students across the region doing that, as well as just citizen scientists across the Tahoe region in California and Nevada. So what kind of data are they looking for? What data do the researchers want to get from this project?

They want to see what kinds of snowflakes are falling, and by the type of snowflake, the way it looks, what kind of crystals have hooked up together on it can give them information about whether that storm was really wet, whether that storm was really cold, and what happened when that snowflake fell. Basically, every snowflake that falls throughout a storm tells a story, and that story is shown by how it looks. And so they look at that snowflake and analyze that snowflake to see all that data. And when they look at that data over a region, they can get a sense of what's going on in that storm. And maybe even predict future storms and what will happen in the future in that area. Did you try to snap some snowflakes yourself? I did. I met with a bunch of kids in Reno, and we learned how to use it on salt at first because it wasn't snowing.

And then the researchers and I went up near the Tahoe area and got some snow ourselves and snapped some pictures. and our photos were, our snowflakes were a bit broken because we had it just snowed. Oh, so it's kind of tricky then. You've got to get the hang of it and figure out how to do it. Exactly. They say the best time is to go out when it's snowing and have the snow fall organically onto the piece of felt. And then that way the snowflake won't be broken. Yeah, just you're imitating a very famous photographer who went out and collected snowflakes that way.

Thank you, Dezzer. And good luck to you on your snow hunting. Hey, thank you so much. Ezra David Romero, Environment Reporter at Capitol Public Radio in Sacramento. You can read his story about the snowflakes project on our website at Science Friday.com. After the break, you've heard about all these diets that keyed out of Mediterranean, the paleo, but what do they mean for your metabolism? Should you be worrying more about your metabolism than the actual calories and things?

Well, we're going to talk about it with David Ludwig. He's at Harvard. You know him. He's a very famous guy talking about nutrition. We'll be right back after this break. This is Science Friday. I'm Ira Flato. If you've made dieting, part of your New Year's resolutions,

you are facing a challenge. Which diet to pick? The paleo. The keto, the Mediterranean. Seems like a new one comes by every day. And some of the diets count calories. Some of them count carbs. In a recent study in the British Medical Journal,

scientists tested out the low-carb idea in nearly two-hundred. hundred patients. Excuse me. And they saw that reducing carbohydrates did have an effect in increasing metabolisms, which metabolism, which the researchers said was crucial. So why is metabolism so important in studying diets? Just one of the many questions we all have about dieting, including what about caffeine

and artificial sweeteners? And should we rethink our idea of the calorie count? Do you have questions about carbs, fats? What do you eat, affects your metabolism. Our number is 844-8255-844-Sight-Talk, or you can tweet us at SciFRI. My next guest is here to walk us through it all. David Ludwig is an author on the BMJ study. He's also Professor of Nutrition at Harvard University,

co-director of the New Balance Foundation, Obesity Prevention Center at Boston Children's Hospital. Welcome back. Dr. Ludwig. Great to be with you this first week. of the new year. Yeah, that's when everybody did their resolutions, right? Exactly. There's so much confusion when it comes to dieting. Is the public justified in being confused? Well, of course. I mean, there's, you know, I've said that dieting isn't, nutrition isn't rocket science, it's actually more complicated because you think of diet and nutritionists including

hundreds, if not thousands of different individual factors, you know, carbohydrates, protein and fat we've heard about fiber, but the hundreds of vitamins and minerals and other components of our food, the gut microbiome, and the many different ways that these compounds interact with our hormones, our metabolism, even the expression of our genes. And we haven't even gotten to human behavior yet, which is why it's so difficult for one diet study to ever answer every question. In your study, you found that lowering carbs and replacing them with fats actually, in increased metabolism. Can you explain the mechanism and why increased metabolism is important? Yeah. Well, the standard approach to weight control considers all calories or alike. Just eat

less and move more. We've heard it a thousand times. Of course, the food industry loves this message because it means that 100 calories from junk food is theoretically no more fattening than 100 calories from Brussels sprouts. The problem is when you restrict calories, the body fights back in predictable ways. Hunger increases, metabolism slows down, and that's why most diets ultimately fail. But according to another way of thinking, the processed carbohydrates that flooded our diet during the low fat years have driven up insulin levels programming the body to gain weight. But by cutting bad processed carbs, we might be able to speed up metabolism, making it easier to keep the weight off. And that's exactly what we tested. We looked at 164 people

adults who are at least overweight brought their weight down by about 10%, so their body would be under some stress, their metabolism would be slowing down. And then we randomly assigned them to low, moderate, or high carbohydrate diets, 20, 40, or 60% carbohydrate. We adjusted their calories to keep their weight the same. After about five months, we found that people on the low carbohydrate diet, their metabolism was running about 200 or 250 calories a day faster than people on the high carbohydrate diet. So if that difference were maintained over the long term, it could give a serious boost to our ability to maintain weight loss for the long term.

So actually your body was burning more. Yeah, burning more, the same, the type of calories that you eat may affect the number of calories you burn. And if this is true, then simply considering all calories or a light misses an important lever, an important tool that we can use to help us succeed with long-term weight loss. Now, a lot of times when people cut the carbs, they add fat. Does adding fat, is that counterintuitive to what you've learned? That's what we did in our study, although I want to emphasize that even our low-carbohydrate

diet didn't eliminate all carbohydrates. It really just eliminated the processed carbohydrates. Those are the ones that digest the fastest. White bread, white rice, potato products, sugar. These digest quickly and raise insulin the most. One advantage of fats, especially the healthy fats that we know about nuts and nut butters, full fat dairy, avocado, olive oil, even dark chocolate, that they don't raise blood sugar or insulin in all.

And for that reason, they're very satiating. I mean, just do a quick mind experience. think about bread and butter. Most people would say between the two, butter is the healthier, is the tastier component. But which is it easier to binge on? People would have no trouble sitting down and eating three, four, five slices of bread. But imagine eating a quarter stick of butter. I mean, after the first bite or two, you would just be intensely satiated. In fact, most binge foods tend to be mainly carbohydrates. And so the idea then is to eat. eat well. In other words, I hear what you're saying, don't count the calories, just count the

kinds of food you're eating. You know, to be thinking that the body wants to control its weight, that's why we didn't have an obesity epidemic for most of human history, even for populations that had plenty of food around and weren't working in the fields 12, 14 hours a day. The body is designed to regulate weight, just like it regulates body temperature and breathing. But there's something that happened in the last 30 or 40 years that seems to be driving that body weight set point up for much of the population. And according to one way of thinking, the process carbohydrates are an important part of it. Not the whole story, and certainly not the whole story for everybody.

But it's really one of the most likely explanations for why this obesity epidemic kicked off just as we got onto the low-fat diet crates. There were a couple of popular studies out this week that said the Mediterranean diet is still the most preferred diet. What is your reaction to that? Well, first, there's no one Mediterranean diet. You know, what people ate in Italy or Greece was different from Lebanon or Spain. But one component that's typically considered throughout the Mediterranean diet is, well, there are several. One is a focus on whole foods.

So the carbohydrates that are eaten are natural and slower digesting, fruits, vegetables, minimally processed grains, and there's typically more fat. Olive oil is almost worshipped in many parts of the Mediterranean. Let's go to the phones. 844-724-8255. Let's see what we got it. Let's go to Jordan in Wallach, California. Hi, Jordan.

Hi, it's Willis, California. I'm sorry. No problem. So my comment is that your guest has been talking about how if these things were sustained, it could be great for weight loss, but the science shows that 0.8%, that's less than 1% of people that start a diet, have kept that weight off five years after they started. And we also know that yo-yo dieting, losing a lot of weight and then gaining it back and then losing a lot of weight and gaining it back is incredibly bad for your heart and otherwise bad for your health. So my question is, if the science shows that dieting doesn't work, period, and we know that it's unhealthy, why are we still encouraging people to go through this? All right. Let's get a question, Dr. Yeah, great, great question. I love that question. It's how we define dieting. And in fact, what the caller is saying is perfectly consistent with the findings of our BMJ study, that if you focus on cutting back calories, you know, that's been the, you know, sort of the holy grail of weight loss over the last half century of focusing on eating less, moving more, just getting a negative calorie balance, you'll, of course, lose weight loss. for a while, but the body fights back against that.

So our study, and not just this study, but many other lines of research suggest that the quality of our foods make more of a difference over the long term than the quantity. If you get the quality right, you know, in other words, if you control blood sugar, hormones, you calm chronic inflammation and insulin resistance, then the body has a better chance to find a healthy weight naturally on its own. It's just like, you know, breathing. You don't think about breathing. You can hold your breath.

You can speed up your breath or slow it down. But ultimately, your body takes over naturally. Body weight could be the same thing. It's over a longer period of time. But there are control systems in the brain and organs throughout the body that are designed to do that. We've got to figure out what has mucked up this mechanism and restore conditions that will help the body succeed without that struggle. Let's go to the phones to Miles in Portland, Oregon. Hi, Miles. Hi.

Go ahead. Well, I've been hearing a lot lately about the benefits of reducing the number of hours in which you can eat during a day where you would only eat within an eight-hour period and you'd have 16 hours in which to digest, I suppose. I'm wondering what your research or your experience might say about that as a beneficial diet for everyone. Yeah, this is intermittent fasting, and it's very popular, and I think it's a great tool for some people, but it's a two-edged sword. I mean, let's just look around. Many people have difficulty just going, driving in the car for a half hour without eating. We're constantly snacking. And according to this other way of thinking, it's called the carbohydrate insulin model that we tested in our B.

MJ study, that hunger is being driven by the swings in blood sugar and insulin levels. So, yes, fasting can be very helpful to metabolism, but the first thing we need to do is eat a type of diet that's going to calm down those swings, help fat cells calm down. And once that happens, people will be able to fast more easily. But if you just take a person on a standard, low-quality diet, they're going to struggle just, just going from lunch to dinner without eating, let alone these more elaborate kinds of fasts. You touched on a couple of points I want to make before we run out of time. How does our diet affect inflammation?

Because physicians always, researchers are always talking about one of the great villains in our health is inflammation in our body and our blood vessel, things like that. Does the diet affect that? Absolutely. We know that obesity is a big contributor, but there's nothing. specifically wrong with having some extra fat in the body, it's when that fat becomes inflamed. When the immune response floods into fat cells, the fat cells get inflamed and release a whole series of compounds that produce inflammation throughout the body and other organs, even in the

brain. And that sets the stage for the classic chronic complications, such as diabetes, heart disease, maybe even Alzheimer's. Independent of weight, we can adjust, we can calm inflammation down, and it's sort of twin troublemaker insulin resistance by the quality of what we're eating. We know that high-quality fats, slow digesting carbohydrates, the right amount of protein, lots of natural, unprocessed foods, tend to do that. Okay, let's go to the phones to Connecticut. Melissa in Connecticut.

Hi, Melissa. Hi, thanks so much for taking it. my call. I am overweight. I have type 2 diabetes, and I am a vegetarian. So many people have recommended to me a low carbohydrate diet, but when I look into them, they never really seem very accessible to vegetarians. They seem to focus more on, you know, having a higher protein, which is usually like the lean proteins, like chicken breasts and things like that. So I just wanted to know what you would recommend for somebody like me. All right, let me just remind everybody that this is Science Friday from WNYC Studios.

Right. Well, that's a great question. And unfortunately, there's a lot of misunderstanding leading to unnecessary polarization with the vegetarian and vegan community for ethical reasons, tending to favor low-fat diets and then the low-carbohydrate group tending to favor a more animal product-based diet. but that conflict doesn't have to occur in the modern food environment. You can eat low-fat with a lot of animal products, dry chicken breast and low-fat dairy and egg whites,

or you can eat a rich high-fat diet, which is mostly plant or entirely plant-based, with foods like nuts and nut-butters, olive oil, rich sauces and spreads, dark chocolate. So in terms of diabetes, you know, I can't make any specific recommendations for you, but diabetes is, by definition, carbohydrate intolerance. It means the body can't manage, metabolize the carbohydrates from a meal. So for people with that condition or severe insulin resistance, which is closely related, I think low carbohydrate diets, which could be plant-based, as we just discussed, are especially appealing.

One last question before we go has to do with coffee. There are studies that are showing that coffee is good for you, And not just caffeinated coffee. Something in coffee, right? Yeah, it doesn't seem to be the caffeine per se because the protection quite consistently is seen once you get above one or two cups of coffee with decaf or with regular. So why is that? One explanation is that for people eating a typical American diet, very low in quality, very few protective plant substances, antioxidants, phytochemicals, these things that calm inflammation, that for people on that diet,

coffee becomes their main source of these plant protective substances. And so we don't know yet what would happen with people eating a very high-quality diet, whether you'd get additional protection. But I think we can all feel pretty good, you know, as long as you don't have any side effects from the caffeine. With drinking two or three cups a day. Two or three cups. What is the protection you're talking about?

The most striking and consistent protection is against type 2 diabetes. and there are some other chronic diseases that seem to be benefited as well. You seem to be saying don't go on a temporary diet to lose weight, but basically a lifetime of changing your eating habits. Well, that's the word diet in its original, I think it was Greek, means a way of life. And I think that our research suggests that a focus on food quality rather than calories and quantity

may get you there more slowly, but it'll keep you there over long term. We certainly need more research, and everybody's different, and one size isn't going to fit all, but this is an exciting time to be in nutrition research, and I look forward to discussing this with you

more through the use. No, I'm very happy to have you on. I'm actually going to ask you to stay through the break here because there are so many people have so many questions. For example, a tweet from Melissa, can genetic testing help with knowing I've got less than a minute to go.

I'm going to read the tweets. We'll answer them after the break where your origins are and can help with what you are designed to eat. Another tweet says, what about bloating? Why does this happen even when we eat quality foods? And Chris says, why do some people crave carbs so much, so much more than others that have always preferred a high-protein diet, low in sweets, and weight has never been an issue.

Well, get to those tweets after the break, talking with David Ludwig from over the air, who's the author of a British Medical Journal Study. He's Professor of Nutrition at Harvard University. Our number 844-8255 will be right back after the break, so stay with us. This is Science Friday. I'm Ira Flato. We're talking with David Ludwig.

He is a professor at Harvard and an expert in nutrition. We're talking about the dieting that people are going through. So what is your recommendation? In a few minutes I have left, Dr. Ludwig. What is your recommendation for people who say, I've got to change my way of eating. I want to lose weight, but I want to keep it in a plan that lasts me for a lifetime. Right. Well, I think the focus, keep the focus on quality over quantity.

I think we now really clearly understand that when you go on a conventional low-calorie diet, hunger goes up. That's the very first thing that happens. And hunger isn't a fleeting feeling. It's a primal biological signal that your body wants calories. And even if you could ignore it, which most people can't even for one day, your body would fight back in other ways with slowing metabolism. We need to figure out how to eat that doesn't exacerbate this body pushback.

In that battle between mind and metabolism, metabolism tends to win. So this is the big debate. Does the relative amounts of protein, fat, and carbohydrate, or other aspects of the way, of our diet matter there. I think my opinion is that the processed carbs are the main problem here. They drive up insulin. Insulin, you can call it the miracle growth for your fat cells. It programs your fat cells to store extra calories.

It may be a subtle effect, but over weeks, months, and years, I think there's a plausible case to be made that that's underlying a good part of the obesity epidemic. So we can focus on cutting back the process. that flooded our diet during the low-fat years, white bread, white rice, potato products, added sugar. Replace that with unprocessed carbohydrates, whole fruits and, you know, minimally processed grains the way that grandparents used to eat it. And not fear fat. Fat is, it makes food tasty, and it slows down digestion, doesn't raise insulin. So in my view, fat should be encouraged,

not feared in a weight loss plan. Sound very much like that. Michael Pollan. You know, eat with your grandmother ate and shop on the outside aisles of the grocery store. Sounds good. Dave Ludwig, Professor of Nutrition at Harvard University and co-director of the New Balance Foundation Obesity Prevention Center at Boston Children's Hospital. Have a happy New Year, and thank you to have to be with us today. Great to be with you. Earlier this week, hundreds of thousands of revelers huddled together in the pouring rain in Times Square for an annual tradition to watch New Year's ball drop.

Yeah. But once the clock struck midnight, the song was sung, loved ones were kissed, and all anybody wanted to do was they get out of there. Problem is, how do you get thousands of people to safely move out of a crowded few square blocks of Midtown Manhattan? Well, this is actually something that scientists study. Researchers reported in the journal Science that a crowd of people at the starting line of a marathon moves sort of like a wave, adhering to a basic principle of physics. So can understanding that fluid dynamics of crowd movement help us to get the, well, get to the exit door a little bit faster than the next guy? Here to explain it all is Dr. Nicholas Willett, Associate Professor of Civil and Environmental Engineering at Stanford.

He's the author of a Perspectives article in the journal Science discussing the recent research. Welcome to Science Friday. Thanks for having me on the program. Let me start with a most obvious question. Why do scientists want to study the way crowds move? That's a great question. And one of the things I really like about working in this area is that there's not just one answer to that. And there's lots of different communities of scientists who are all interested in this question.

From the standpoint of human cards in particular, there are fundamental questions we want to understand about how, say, to design spaces. so that people can use them effectively. You mentioned clearing out Times Square. You might want to think about how you might design stadiums or big venues like that so that people can easily get in and out. And then we'd also like to prevent possible crowd disasters. We all hear stories about crowd panic when people get trampled. That's clearly a bad thing.

There's a hope that by understanding at a more fundamental level how human crowds behave, we may be able to prevent that kind of situation. So how did the authors on this study do different? What did they do differently from other studies of crowd movement? Well, they took advantage in a really clever way of what you might call a natural experiment about how crowds behave. So as you said, they went to the start of a marathon to do this work. And so I'm not a marathon runner myself, but reading the paper, what they did was

So marathons clearly have a lot of people running, and this was a Chicago Marathon, so it's a major event. There's lots and lots and lots of people involved in it, and you can't just let everyone start running at once. That would cause complete chaos. So what happens is that you organize the participants, based to some degree on how fast you expect them to run, and you let them go in segments. So a group at the front gets to go first, then you move up the people behind them, they get to run, and so on and so on. And what the authors of this piece found was that that event where the race organizers said, okay, the next cluster of people gets to move to the front. They told the people at the front of that cluster, now it's time to move forward.

But the information that it was time to move wound up, they observed that it propagated back through the crowd as a wave, in much the way you might expect a surface wave on a lake to move when you drop a rock in it. That's interesting. So people can be treated when you look at a large mass of them as large particles that we study as waves would move, drops of water, lots of drops of water? That's the idea here. It's clearly not the same in detail, but the overall picture of how you might want to think about the crowd, that's the idea in this paper. And it represents something of a new approach in studying the broad field of collective movements of animals and humans. In that instead of thinking about how to talk about the crowd as if it's made up of people and saying what each individual person does, the new part here is to say, okay, that crowd, that itself is a thing.

That thing has properties. And by studying how the whole crowd responds to an external stimulus, we can understand those properties. and make a good physics-based model for how it's going to behave. No, you don't study people. You study insects and birds and animals. That's right. Is it correct? You have a little setup in your laboratory of midges that fly around?

A five-foot plastic cube, basically a home for how many midges are in there? Oh, I've never counted them all. Thousands? Probably. We're interested primarily in what happens when they swarm together, and our swarming events have something like 50 to 100 midges in them. So they swarm, and do they swarm like birds? Do they swarm like schools of fish?

Is it the same kind of action? So the one answer to that is that nobody really knows if all these kinds of animal groups move in similar ways. The major difference between the swarms we study in the lab and what you might see in, say, a flock of birds or a school of fish, is that the swarm isn't going anywhere. So flock of birds is definitely moving in some direction. But these kinds of swarms, you see these in, say, the late afternoon, if you're walking around outside, sort of a ball of bugs floating in the air in front of you. It's always right at head height when you're biking through and smacks into your face. Right, right, right.

I know what you're talking about. Yeah. Yeah. Can you learn how people then? Anything, is this applicable to how people move in the swarms or groups? We think so. The idea behind all of this is that there's only so many things that can happen in the world. The laws of physics are very constraining.

And so by studying some kinds of collective behavior and understanding how you would model that, that framework that you develop should be applicable to many other kinds of groups, of animal groups as well. In much the same way, the analogy I like to make is that when you think about how, say, materials work, So different kinds of solids, different kinds of liquids. They're all different in detail, and solids are not liquids or not gases, but they're all recognizable and understandable as materials. And you kind of understand how to describe the behavior of all of them

in some kind of unified framework. If a crowd is moving and you have a large crowd of people moving, can you treat that, let's say it's 100,000 people in the end of the marathon or some people in the ballpark and see them do the wave or something like that. Can you treat them as like statistically, you know, as particles or ping pong balls or something else like that? Absolutely. That's any physicist looking at this, that's the first thing you would think of doing. Because that's ultimately what we've been very successful doing for the past 100 years or so in treating things like gases and liquids.

We know they're made of molecules. We know how to do the statistics of the molecules and average over them to say something about the typical properties of a whole lot of them together. The wrinkle in animal behavior comes that in the fact that animals are not like molecules, and that makes the problem much, much, much more difficult. Molecules have the nice feature that essentially they move randomly, in a very precise sense, that means we know how to do the averaging. But animals and people are not quite random enough to do that in some sense. So what happens then is that the details of how they move become much more important.

And there's various laws of physics that aren't quite obeyed in the same way that make that problem much, much more challenging. Yeah, because the people in that crowd in Times Square, they want to get out of there. I mean, they're motivated to go someplace, but random molecules are just moving randomly. Right. So you have to find a way of modeling that the difference. So I guess you have to split the hairs, right? You have to go somewhere between the statistical model and somewhere between knowing how people or animals act in a certain direction or motivation and find the middle someplace.

That's right. And that's the approach that people have taken over the years with a fair amount of success in trying to do this. So the kind of gold standard model for collective movement of animal groups is what technically gets called agent-based model. but really you can think about it as thinking about the crowd really or the flock as being made of individuals. And what you do then is you take each individual and you give it some rules. You say, okay, typically for a flock or a crowd, the rules are something along the lines of don't get too far from everybody else. Don't bang into them, so don't get too close. And if you're not too far and not too close, then try to go in the same direction as everybody around you.

And that will maintain some kind of smooth. motion. And if you put that all, sorry. I'm sorry, go ahead. If you put that all together on the computer and you simulate that kind of model, you get a result that looks qualitatively really, really nice, and so nice that this kind of model has been used in the computer graphics industry, in CGI and movies, and in video games for 20 or 30 years now. This is Science Friday from WNIC Studios. Amira Plato talking about modeling crowds with Nicholas Willett. associate professor of civil and environmental engineering at Stanford University. You are civil engineer.

I imagine you engineer or civil engineers. They model buildings and highways and things. Do you use the kind of information you learn about crowds and constructing things? Not in construction per se, but I think there are a lot of really exciting ideas or ways that engineers are thinking about using this kind of of paradigm, these kinds of models in the future for engineering projects. So I live, I'm at Stanford, so I live in Silicon Valley, home of self-driving cars these days.

So it's very likely that in the fairly near future, we're going to have a lot of autonomous cars running around on the highways and on the roads. And the most basic thing that you'd want to have happen in that situation is the cars don't run into each other. Yeah, that is, yeah. Yeah, that's typically not a good thing. That's sort of at a fundamental level exactly what the kinds of animal groups are good at doing. The difference though in how engineers have traditionally made that kind of system work and how animals do it is a question of who's in charge and where the control, if you will, comes from.

So if you think about a normal engineered system, we like to know where everything is going. We like to have someone in charge who knows all the information and can give specific instructions to all the individuals. That's in some sense how the air traffic control network works. You have people sitting there, they know where all the airplanes are, and they make sure that everything works smoothly. Now, birds say, or even human crowds, that's not the way it works. No one's in charge. No one's telling each individual bird in a flock what to do,

and yet the whole system functions really, really well. Birds look at what's nearby, their local neighborhood of other birds near them. They do something. They behave in some way. And the whole system works really, really smoothly. There's then interest in taking that kind of idea and applying it to something like self-driving cars or swarms of drones to achieve the same kind of robust, well-controlled fault-tolerant system without any kind of pinch points that may lead to failure. But those animals must have a way of one animal, the lead animal or whatever animals leading them to communicate with the rest of the other animals, which way to go? Well, typically we actually think that there is no lead animal.

Uh-huh. So that the properties of the group, the fact that the group is there and functions is what we tend to, what we call an emergent phenomenon from all of the little local interactions. And that's like, if you think about a really big flock, you know, thousands of birds say you can't, a single bird cannot see across the entire flock. It has no idea what's happening on the other side. And yet the whole thing functions as a unit. Yeah, and it's like watching those school of fish just turn on a dollar. time altogether. So there's something called an emergent.

Submergent knowledge in the flock or the school. Yeah, and people talk about swarm intelligence and things like that, that the group has some kind of emergent intelligence, reaction to its environment, and some kind of coherent way that is not top-down control, but rather just comes out from all the little local interactions happening together. And we don't know what that is. We don't exactly know how to do that, no. But we'd like to because we're talking about swarms of bots or, you know, cars moving

on the highway. Exactly. Exactly. And one of the things that this field has discovered over the years that I think is very robust at this point that we all agree on is that one of the cool things is that it doesn't take much individual intelligence or complexity of the individual units in that flock or swarm in order for the whole group to do something complicated. Fascinating. So that's a, yeah, that's really nice from the standpoint of robotics, say.

So you could design a whole lot of simple, relatively stupid robots where the ability to accomplish a complicated task comes from getting them together rather than having to build each one with a whole lot of processing power. I read the Michael Crichton novel about that. Yes. Thank you. Dr. Nicholas Willett Associate Professor of Civil Environmental Engineering at Stanford University. Have a happy new year.

Happy New Year to you as well. Charles Berkwist is our director, senior producer Christopher and Taliatta, and our producers are Alexa Lim, Christy Taylor, and Katie Feather. We had technical engineering help from Rich Kim Sarah Fishman and Kevin Wolfe. And, you know, you know how to reach us. We're all over the place on Facebook, Twitter, Instagram, and your speakers. Even if you miss something, your speaker, ask it to play Science Friday. And get the latest episode right there.

So every day now is Science Friday. Happy New Year, everybody. I'm Ira Flato in New York.