This is a transcript of our episode “Understanding coronavirus and how germs spread.”

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Gus: You’re listening to Brains On, where we’re serious about being curious.

Brains on is supported in part by a grant from the National Science Foundation.

Molly: Gus! So glad you could make it to Brains On headquarters for today’s taping.

Gus: My pleasure!

Molly: The studio’s right this way. Yeah, this all kind of came together at the last minute so we really, really appreciate…

Bob: [coming through megaphone] Please step away from the fort.

Molly: Bob?

Gus: Um… Bob seems to have built a fort entirely out of bottles of hand sanitizer.

Bob: [coming through megaphone] You are correct! This is Fort Fastidious. It is just big enough for me and my popsicle stick collection. And a few snacks.

Gus: Can I ask why?

Bob: [coming through megaphone] Well --

Molly: Bob, we’re right here. You can put the megaphone down.

Bob: [coming through megaphone] Oh, ok. [normal voice] Well, I was reading about coronavirus and it was making me a little nervous -- well, I guess I should say a little more nervous than usual. And this just seemed like the best possible course of action.

Gus: I’m not sure that’s necessary...

Molly: Ok, Bob. We have to go to the studio and tape an episode. Maybe you should listen to it when we’re done.

Bob: If it can be accessed from inside Fort Fastidious, then sure. Um, you can’t get viruses from podcasts, right?

Molly: No Bob.

Gus: Bye, Bob.

Bob: See ya later. [through megaphone] Occupants of Brains On Headquarters -- this is a public service announcement from Fort Fastidious. Stop touching your face! Wipe down those headphones before using them! And for the love of all that is good and Purell -- please wash your hands! And then when you’re done, maybe bring me more snacks? Please?

[Brains On theme song plays]

Molly: You’re listening to Brains On! from American Public Media. I’m Molly Bloom and my co-host today is Gus from Seattle. Hi, Gus!

Gus: Hi!

Molly: So, Gus what have you heard about the coronavirus?

Gus: Well, there’s a lot of stuff that they say at school that I know isn’t true. And it’s kind of confusing overall, but I think I can tell what’s true and what’s not.

Molly: What kind of stuff are you hearing at school that you think is not true?

Gus: Well, there was this one kid who was eating grapes and they picked one out and threw it away. And I asked them why they just wasted a grape, and they said that it was a “coronavirus grape,” but I thought to myself, “Grapes can’t get the coronavirus.”

Molly: Yes.

Gus: And also some people are lying about people they know who have the coronavirus and what to do if you see someone with the coronavirus.

Molly: So you know, in Seattle as we’ve heard, there are some cases that have been confirmed there. Some schools are closing and businesses are telling people to stay home. So do you know anybody who has been told to stay home or isn’t going to work like normal?

Gus: Yeah, my friend Jack, his dad works at Microsoft and they’re telling him to work from home now because of the coronavirus.

Molly: When you hear that kind of stuff, how does that make you feel or what does that make you think about?

Gus: Sometimes it makes me nervous, but it doesn’t always make me scared or nervous or paranoid because I know that it’s not very likely that I will get sick if I do come in contact with it. So sometimes when I’m feeling scared about it, I just tell myself that and I feel kind of relaxed about it.

Molly: And the reason people are telling people to work from home or closing schools is sort of out of a lot of caution because they want people to be around as few people as possible, just in case. Not necessarily because those people are sick or know anybody who’s sick.

Gus: Yeah.

Molly: Well coronavirus has been in the news quite a bit lately, and just like so many topics, we had a lot of questions, and we know you do too.

Gus: To start off, the coronavirus that’s in the news is just one kind of coronavirus. There are a whole bunch of others, too.

Molly: Here’s a little factoid for you: Corona is the Latin word for crown! Coronaviruses look like spiky little balls.

Gus: Kind of like a crown! Hence the name!

Molly: Most people have gotten one of these viruses at some point or another. Ever have a common cold?

Gus: That’s a coronavirus!

Molly: But the coronavirus that’s in the news is a new type of coronavirus. It’s made some people pretty sick, but a lot of people have recovered just fine.

Gus: The disease it makes you sick with is called COVID-19.

Molly: Which is a technical-sounding name, but it’s really just short for Coronavirus Disease 19, for 2019 -- the year it first showed up. Producer Menaka Wilhelm’s here to give us the scoop.

Menaka: Hey Molly and Gus! I want to introduce you to someone who knows ALOT about this virus...

Apoorva: My name is Apoorva Mandavilli. I'm a journalist. And I write mostly about science. And lately, I've been writing a lot about the coronavirus outbreak.

Menaka: Apoorva has been writing about the coronavirus for the New York Times. She says the first outbreak happened in a place called Wuhan, China.

Apoorva: Well, so we found out about the virus on December 31. That's when China first let the World Health Organization know -- that's the international group that tracks outbreaks like this. And really soon after, like, within three weeks, the numbers of people infected started to climb very, very fast.

Menaka: So the virus was spreading quickly. It was new and we didn’t know a lot about it. People started to get worried. And even though this outbreak started in China, people carried the virus to new places as they traveled around the world.

Some travelers probably didn’t know they had the coronavirus — their bodies were likely fighting the virus without showing any symptoms.

And so far, most people who get sick from the coronavirus get what scientists call a mild case. Maybe they get a fever and a cough, those are common symptoms -- but they don’t have to go to the hospital. They get better just by resting at home.

But for some people, especially people over 60 years old or people who have other long-term health issues, the coronavirus can cause a really high fever and a lung infection called pneumonia. These cases are pretty dangerous, and some people who get sick like this have even died.

But remember — most people get better from the coronavirus on their own, they just drink fluids and take it easy. The hard thing about treating this virus is that there’s no specific medicine for it. Apporva says scientists are working on a vaccine, but we’ll have to wait a bit.

Apoorva: It takes time to make the vaccine, it takes time to test it in people, it takes time to figure out how much to give, when to give,

Menaka: But here’s some good news — hardly any kids have gotten sick with this coronavirus.

Apoorva: That doesn't mean they don't have the virus, it may mean, actually, that they get the virus, but their immune systems are able to fight it off. So they only get a teeny bit sick and not enough even for them to know that they're sick.

Menaka: Why aren’t kids getting as sick? No one really knows. But there are some theories. Maybe kids just pick up more new germs -- from the playground or school desks -- so their immune systems are used to fighting things off. Adult immune systems, on the other hand, might be less ready for the attack. Apoorva says it’s not uncommon for a virus to hit adults harder than kids -- that’s how chickenpox usually works.

Apoorva: Adults have other health conditions like maybe they have diabetes, or they have heart problems that make things worse for them. And also, it seems like the immune system just gets weaker as people get older. We just don't know a lot about how all of this works with this coronavirus yet, but kids definitely don't seem to be at high risk.

Menaka: Even though kids seem to handle this virus well, there are still schools that are closing. And like Gus mentioned before, some offices are telling people to work from home, and other big events have been canceled. These closings and cancellations might keep happening — the goal is to prevent a whole bunch of people from being exposed to this coronavirus all at once. The fewer people who are sick, the better doctors and nurses can take care of everyone. So lots of people are trying to help, even though there are a lot of questions about coronavirus.

Apoorva: There are a lot of really, really smart scientists figuring out the answers to all of these. And one of the very cool things with this outbreak has been how open scientists around the world have been with sharing information. So I think we'll have some answers really soon. And, you know, try not to worry, there are a lot of very smart people who are figuring it out. And in the meantime, all we can do is practice good hygiene and keep trusting in the people who know what they're doing.

Menaka: So, just like you -- scientists around the world have a lot of questions, but luckily, we’re finding answers pretty quickly too.

Molly: Excellent update Menaka.

Gus: Yeah - thanks!

Menaka: See you later Molly and Gus! Happy hand washing!

Gus: Bye!


Molly: Ok, Gus, before we go on, it’s the...

[Mystery Sound audio cue]

Molly: Here it is!

[Mystery Sound]

Molly: All right, what is your guess?

Gus: If I had to make a solid guess, I’d say… a copy machine?

Molly: Hmmm very good guess.

Gus: Maybe it was either printing or it was just scanning something because I know when that scanner thing goes back and forth it kind of makes a [scanning sound] noise.

Molly: Yeah, so it kind of sounds like a machine of some sort. Well, we’re going to hear it again and give you another chance to guess a little bit later in the show.


Gus: We’re working on an episode all about ink and we want to hear from you.

Molly: We’re asking you to grab your favorite pen and write us a poem about ink.

Gus: An ode to ink.

Molly: An ink haiku.

Gus: An ink sonnet!

Molly: An ink limerick!

Gus: Or limer-ink!

Molly: Nice one. You can send us your ink-celebrating poems at brains on dot org slash contact.

Gus: That’s where we got this question.

Nolan: My name is Nolan from Bellevue Nebraska, and my question is: How do shoelaces come untied?

Molly: We’ll have the answer to that during our Moment of Um -- and we’ll read the latest group of listener names to be added to the Brains Honor Roll.

Gus: That’s all at the end of the show. So keep listening!


Molly: You’re listening to Brains On from American Public Media. I’m Molly.

Gus: I’m Gus.

Molly: Ok, Gus, like I’m sure you’ve experienced when one person in your family gets a cold, that cold virus spreads and then all of a sudden your whole family is sick!

Gus: So how does that happen? How do viruses spread?

Kara: We can answer that!

Gus: Who said that?

Gilly: Us - Kara and Gilly! You can’t see us because we are microscopic.

Kara: We’re viruses! And we have a podcast too!

Molly: Oh geez. Does everyone have a podcast now?

Kara: Hit it, Gilly!


Kara: I’m Kara!

Gilly: And I’m Gilly. And this is...

Both: Going Viral with Kara and Gilly!

Gilly: ‘Sup Kara, how’s things?

Kara: Good - yeah. I’ve been infecting a new friend. It’s going well but I hope they don’t get sick of me.

Gilly: Uh, Kara are you trying out your stand up material on me again?

Kara: Yeah! I’m performing tomorrow night at the Snot Factory!

Gilly: Well, that joke was a little on the nose.

Kara: I’d rather be IN the nose. Eh?!

Gilly: You’re a dork but I love you.

Kara: Aw.

Gilly: So - we got some fan mail.

Kara: FAN MAIL! Ohh yeah!

Gilly: Let’s see - whoa. OK.

Kara: Is it -- what is it?

Gilly: It’s like a bunch of questions. Here - let me play them.

Asher: Hi, my name’s Asher from Los Angeles, California. How do viruses move from one person to another?

Finn and Ellis: Hi, this is Finn and Ellis and we want to know how are viruses formed?

Anna and Charlie: This is Anna and Charlie and our questions are what are viruses, how do they make people sick and are they alive?

Amelia and Isaac: Hi my name’s Amelia. And I’m Isaac. How does your body react to a virus and why?

Kara: Cute. Love it.

Gilly: Yeah. Super cute. OK -- so, here’s the QnD --

Kara: -- Quick and Dirty --

Gilly: -- On us viruses. We’re ultra-tiny, microscopic bits of genetic material. Are we living? Are we dead?

Kara: Meh - it’s not really clear.

Gilly: Kinda depends on your definition of living.

Kara: So true. What is clear though, is we need to invade a living cell to make more of ourselves.

Gilly: Exactly. And that’s where you come in, Viralinos -- our wonderful, dedicated friends of the pod.

For us to spread - we need to travel from one infected person to another. And in humans, we like to do that in viral droplets!

Kara: Viral droplets are like carpools for viruses -- but instead of SUVs and minivans -- it’s spit and boogers.

Gilly: The only way to travel.

Kara: When someone sneezes or coughs - they shoot out these little droplets of saliva or mucus full of viruses.

Gilly: Sometimes we land straight in a mouth!

Kara: GOAL!

Gilly: Or up a nose or in an eye. Your average cold or flu virus can only infect you if it gets in one of those places.

Kara: It’s mouth, nose or eye -- or kiss your infecting days goodbye!

Gilly: Right -- but after a cough most of the time we land on the floor.

Kara: Womp womp.

Gilly: Or a wall. Or a table. Whatever.

Kara: Viral droplets don’t have GPS - so it’s literally a toss-up.

Gilly: BUT - some viruses can survive several hours or even days outside a body. So say you pick up something from the floor. Or touch that table.

Kara: Ohhh. I like where this is going.

Gilly: Then we get on your hand…

Kara: Uh-huh...

Gilly: And then you take your hand…

Kara: Oh I love this part!


Kara: YUSS! We’re in!

Gilly: And you thought you were just biting your nails or picking your nose.

Kara: Or stroking your teeth for good luck.

Gilly: Kara - humans don’t do that.

Kara: I have no idea what they do, they’re so weird.

Gilly: Truth! Well, once we’re in that’s when we shine!

Kara: And by shine, she totally means we try to sneak inside one of your cells and turn it into a virus factory.

Gilly: Sometimes your body’s immune system stops us before we really spread.

Kara: Boo!

Gilly: But other times -- we make it to a cell. You have so many - it’s no biggie. We just hack it so it makes viruses.

Kara: And when that viral cell factory is totally full of new viruses - it explodes! But you know, in a fun way.

Gilly: Well, the cell dies.

Kara: Fun for us I mean.

Gilly: Right right right. It is fun! Viruses shoot out everywhere! We infect new cells and that’s how you get sick!

Kara: Yep. Then - it’s your turn to give us a ride on a viral droplet to our next destination.

Gilly: Road trip!

Kara: Hey Gilly - you know what a virus’s favorite road movie is?

Gilly: What?

Kara: Sneezy Rider!

Gilly: Please don’t put that in your stand up set. Anyway, after the break -- when bodies fight back!

Kara: Keep listening!

Kara: We wanna give a special shout out to today’s sponsors:

Both: People who don’t cover their mouths!

Gilly: They have been with us since the very first episode and, I mean this, we wouldn’t be here without them.

Kara: Whether you’re a virus planning a trip by sneeze, cough, spittle or explosive burp -- People Who Don’t Cover Their Mouths is your best bet for getting to your destination.

Gilly: They’ve got sick people around the globe who just don’t cover their face holes. So no matter where you’re headed, there's probably a person not covering their mouth to help you get there.

Kara: Get a 10 percent discount on your next trip by entering the code GOING VIRAL.

Both: Bon voyage!

Gilly: And we’re back!

Kara: So yeah, like we were saying it’s all fun and games until the human body starts fighting back.

Gilly: Uch, immune systems are the WORST.

Kara: Yeah, you humans have cells that are specifically bent on destroying us foreign invaders. And it’s hard not to take it personally.

Gilly: Seriously, like what did I ever do to you? I mean, we just want to, like, take over your cells. You have lots of them. I don’t want to say it’s greedy -- but maybe it’s a little greedy?

Kara: Your immune system has a bunch of ways of fighting back. Like when you get a fever -- that’s your body making it very unpleasant and hot for us.

Gilly: And all that extra snot makes it harder for us to attach to your cells.

Kara: And you know when you feel all tired? That’s your body focusing on getting rid of us -- I mean, hello! You don’t have endless amounts of energy. You need to pri-or-i-tize.

Gilly: And those aches? Your body is making more cells to fight us off.

Kara: So when you think about it, it’s not really us making you feel like poop. It’s your own body.

Gilly: Accurate. To be fair, if it didn’t stop us we’d take over your entire body. We’re ambitious.

Kara: In conclusion, thanks for nothing, humans!

Gilly: Alright, that’s all we have time for today.

Kara: Yeah, this is getting me all worked up. I need a break.

Gilly: Until next time, we’re gonna hang out on a door handle!

Kara: Byeeee!

Molly: You can learn more about how your immune system springs into action in our episode “How do flu vaccines work?”

Gus: Go check it out! And, Molly, lets…

Molly: Sanitize that microphone those viruses were using?

Gus: Yes.

Molly: Good idea.

[Brains On cue]

Molly: Ok Gus, are you ready to hear the Mystery Sound again?

Gus: Yes.

Molly: All right, here it is:

[Mystery sound]

Molly: Last time you thought maybe a photocopier or a scanner, do you have any new thoughts?

Gus: Well, what’s that called when… it’s an MRI, right? Where you get put into that big tube-like machine? I thought it might be something like that.

Molly: All right well, the answer is: it’s a… automatic hand sanitizer dispenser.

Gus: Ohhhh!

Molly: So it’s one of those machines where you stick your hand under and it squirts out some hand sanitizer right into your hand.

Gus: Yeah, they have those at the zoo up the hill from my house at the bird feeding exhibit.

Molly: Yeah. They are very handy to have around, especially these days when people are talking about washing their hands and keeping them very clean to stop this virus from spreading.

Molly: Like we mentioned -- the coronavirus seems to hit grown-ups harder than kids.

Gus: Yeah, and even though most people have gotten better, a virus-like this can be especially dangerous for older adults and people already dealing with other medical issues.

Molly: Right. So it’s up to all of us to stop this virus from spreading.

Gus: That’s why we’re sharing this important message from two stars of the WHF.

Molly: World Handwashing Federation!

[Wrestling music]

Hygiene Hank: Listen here Coronavirus -- Hygiene Hank has some words for you.

PJ McSuds: That’s right - and you’re gonna feel the wrath of me -- PJ McSuds. Boo yah!

Hygiene Hank: We’re gonna tag team this situation and body slam you back into oblivion pal!

PJ McSuds: We’re gonna dropkick you into the dark ages!

Hygiene Hank: We’re gonna sanitize you into smithereens!

PJ McSuds: Coronavirus -- when we’re done with you, you’ll be the one needing lots of fluids and two weeks bedrest. Boo yah!

Hygiene Hank: First off we’re gonna hit ya where it hurts -- on our hands!

PJ McSuds: That’s right, we’re gonna scrub our mitts for 20 seconds -- AT LEAST!

Hygiene Hank: And we’re gonna make sure we wash our nail beds, our knuckles and all those little nooks and crannies where cowards like you like to hide!

PJ McSuds: PJ McSuds likes to sing her ABCs to make sure she’s washing long enough. Boo yah!

Hygiene Hank: Oh yeah, that’s a jam! And Hygiene Hank likes to hum happy birthday…

PJ McSuds: Mmmhm

Hygiene Hank: -- TWICE!

PJ McSuds: Whoa -- You’re an animal Hank!

Hygiene Hank: I KNOW!

PJ McSuds: And hear this Coronavirus -- we might even use hand sanitizer on you!

Hygiene Hank: Oooh yeah. It’s gonna be the kind with at least 60 percent alcohol -- because we know that’s the kind that wipes out little nitwits like you.

PJ McSuds: But don’t you think for a minute we’re just gonna sanitize and forget about washing -- because PJ McSuds and Hygiene Hank know that handwashing is still the NUMBER ONE way to get rid of viruses -- but sometimes we can’t find a sink, so we sanitize.

Hygiene Hank: Nail on the head PJ. Nail on the head. And you know what else we’re gonna do my compadre?

PJ McSuds: Oh do I ever.

Hygiene Hank: We’re going to hit you with our famous…

Both: Power Elbow!

PJ McSuds: KA POW! That’s when we sneeze or cough -- right into our elbows!

Hank Hygiene: That way if we’re sick we don’t spread you and your puny little friends around in the air!

PJ McSuds: No way brother!

Hygiene Hank: Are we gonna wear masks PJ McSuds?

PJ: Only if we’re sick Hank. Because most masks don’t really stop viruses from getting to you.

Hygiene Hank: But they do seem to help if you’re sick and you don’t want to spread it.

PJ McSuds: But most of the time -- you can try to stay safe by standing 3 to 6 feet away from someone who might be sick.

Hygiene Hank: But PJ, I got a serious question here my friend -- what if we’re working in a hospital?

PJ McSuds: You mean, like when PJ McSuds moonlights as a nurse?

Hygiene Hank: Of course I do PJ!

PJ McSuds: Well -- if someone is sick with coronavirus and PJ McSuds is caring for them, then PJ McSuds wears... an N95 mask!

Hygiene Hank: No! Not the --

PJ McSuds: YES - the N…

Hygiene Hank: Ohhh no.

PJ McSuds: Ninety…

Hygiene Hank: Let ‘em have it compadre...

PJ McSuds: ...FIVE!

Hygiene Hank: BOOM. THERE IT IS! The gold standard for healthcare professionals.

But regular ‘ol blokes, or even super wrestlers like me -- we don’t need that. Because you know what coronavirus -- we have another way to knock you out.

PJ McSuds: That’s right, we’re gonna pin you down for the count with our famous finisher! The N-T-O-F...


Hygiene Hank: That’s where we don’t touch our face with our hands…. unless we’ve washed them…

PJ McSuds: Yeah, that’s pretty much it. Just use a tissue instead bruh.

Hygiene Hank: So watch out Coronavirus -- this is how we’re gonna protect ourselves. See you in the ring CV. And remember -- Hygiene Hank…

PJ McSuds: And PJ McSuds….

Hygiene Hank: Are bringing the smackdown to Virus Town.

PJ McSuds: Boo yah!

Molly: So, like with any sickness, it’s a great idea to keep calm and hygiene on. It’s also great to stay up to date with the latest news. But how do we know who to listen to? Gus, how do you figure out what the best information is?

Gus: Well, I basically check facts about if it really is truth or fact and I say, “Oh thanks that’s good information.” Or just say “No, I’m not going to listen to you.”

Molly: That’s good. It’s good to check your facts. So what are the places that you feel like, “Ok, I will check my fact here, and I think that’s a good place to check it.”

Gus: A good place to check your facts or to get your information is from KUOW where we are now or other news stations that have good information. I think that a bad place to get information is maybe in a place where you don’t know people very well or if you don’t know if people are telling the truth or if they’re lying. Or if you’re at school and someone says, “Hey… blah blah blah. You should totally believe it. I heard it from my parents” maybe. I don’t think that’s a good place to find information.

Molly: So you want to know where that information is coming from.

Gus: Yeah, you probably shouldn’t get your information from anywhere that you don’t know will give you the truth.

Molly: We asked JoNel Aleccia, a reporter for Kaiser Health News, to fill us in on where to get good information.

JoNel: When it comes to viruses and infections, it's best to trust people whose job it is to study these things. That often means government scientists, like those at the Centers for Disease Control and Prevention or the National Institutes for Health, or at universities all around the country. They're not always perfect, and they don't always have all the answers, but they have chosen to spend their lives making people healthy. So they are good sources of information.

You can trust news sources that depend on scientists to get their information. There are all kinds of people to turn to for answers. I mean, parents are always a really great source of information. I would ask a teacher to explain it to you.

Maybe, don't just believe what your friend said or, or something a friend's parents said. It's not rude at all to ask a question like, "Well, how do you know that?" when you hear something that you have a question about.

And so really the best advice is to trust people who have studied this information.

Molly: We have a whole series of episodes about how journalists and scientists work to find the facts -- and how to spot good information when you see it.

Gus: That four-part series is called Prove It, and you can find it on our website,, or wherever you’re listening to this right now.

Molly: Being able to sort facts from fluff is sort of like having a powerful immune system for your mind.

Gus: Totally. Gotta keep that brain healthy too!

Molly: This coronavirus is new, so it’s getting a lot of attention.

Gus: Scientists are working hard to learn more about it.

Molly: The best way to stop the spread of the virus is to practice good hygiene.

Gus: Wash your hands, cover your coughs -- and stop touching your face.

Molly: That’s it for this episode of Brains On!

Gus: Brains On! is produced by Menaka Wilhelm, Sanden Totten, Marc Sanchez and Molly Bloom.

Molly: We had production help from Elyssa Dudley, Ruby Guthrie and Kristina Lopez, and engineering help from John Miller and Robert Jacobs-Springer. Many, many thanks to John Huddleston, Katie Gostic, Phyllis Fletcher, Tracy Mumford and Anna Weggel.

Gus: Brains On is a non-profit public radio podcast. You can support the show at Now, before we go, it’s time for our Moment of Ummmmmm…..

Nolan: My question is: How do shoelaces come untied?

Kristine Gregg: So there’s two things that contribute to your shoelaces coming untied. There’s the fact that you’re swinging your leg back and forth as you take a step, and there’s also the fact that your foot is impacting the ground and that impact is shaking up the knot and causing it to loosen.

Hi! My name is Kristine Gregg and I’m an engineer who studies how things move and break. I was really excited about this question because it’s something I deal with all the time. It’s one of those fun mysteries that we find in our everyday lives.

When we ere first investigating why these shoelaces became untied, we tried a lot of things. I sat on the end of a table and I just swung my legs back and forth for an hour and I noticed that my shoelaces didn’t come untied. But I also just stood still and stamped my foot on the ground, just putting the impact and it still didn't come untied.

We noticed that my shoelaces -- when I was walking down the hallway -- it would be fine, and then suddenly in one step, boom! It would come untied very quickly so that I couldn't see it with my naked eye. So, we used a very high-speed camera so that we could look at the untying process in really slow motion. That's what helped us understand that it really is the combination of the swinging motion and the fact that we're impacting the ground.

What surprised me most is that the length of the loop or the free end in your shoelace knot can influence how quickly it becomes untied. So, if we look at your shoelace knots, you have two loops and then you have the two just single strands of the know. We call the single strands the free end. There's kind of a tug-of-war with between the loop and the free end as it goes through the knot. And if you have a really heavy -- and that's actually how we studied it, we added weights to the free end when we were swinging and impacting that knot. And we saw that if you have a really long or a heavier free end, it's going to win the tug of war with the loop much more quickly and come untied.