Riding in the car: Motion sickness and optical illusions (Road trip pt. 5)

[RADIO TUNING] [MUSIC PLAYING]

GABRIELLA HOPPER: You're listening to Brains On, where we're serious about being curious.

[THEME SONG] Buckled in the back seat near and far. It's a Brains On road trip in the car.

GABRIELLA HOPPER: I'm Gabriella Hopper.

MOLLY BLOOM: And I'm Molly Bloom. This is our road trip series and we're about to take a pit stop.

GABRIELLA HOPPER: Ah, feels good to stretch after all that driving.

MOLLY BLOOM: I think my foot is asleep. I think both my feet are asleep. Is that even possible? And I'm covered in crumbs. Snacking on the road is messy business.

GABRIELLA HOPPER: Hold that thought. And instead, check out that view. Isn't it eyetastic?

MOLLY BLOOM: Eyetastic? I don't think that's a word.

GABRIELLA HOPPER: Fantastic for the eye. Eyetastic. It's totally a word.

MOLLY BLOOM: OK, then. But yeah, it's like we're on top of the world up here. Echo. Echo.

GABRIELLA HOPPER: Reflective sound waves. Sound waves. Sound waves. Glad you pulled over, Molly. This is worth the stop. Should we motor on?

MOLLY BLOOM: Yeah. Let me just take the keys out of my pocket. And-- hold on. Where are the keys?

GABRIELLA HOPPER: Your pocket. Right?

MOLLY BLOOM: Wrong. Oh, no. I see them through the window. They're still in the car.

GABRIELLA HOPPER: We're locked out? I don't want to be stranded here until-- it's getting really dark. Suddenly I'm starving and so thirsty. I'm not going to make it.

MOLLY BLOOM: OK, hold on. I think Sanden lives in that valley below. And he has a spare key. Don't panic.

[PHONE RINGING]

SANDEN TOTTEN: Mollinator. What's up? How's the drive going?

MOLLY BLOOM: Oh, awesome, until I left the keys in the car and locked us out. Can you bring us the spare? We're on that mountain road with the awesome view.

SANDEN TOTTEN: Oh, I know the one. It's totally eyetastic.

MOLLY BLOOM: Where do you guys pick up these words?

SANDEN TOTTEN: Actually, I'm really glad you called. Bob's over at my place, and he insisted on showing me his used Popsicle stick collection.

BOB: Should we look at the cherry-stained ones next, or grape?

MOLLY BLOOM: Eww.

SANDEN TOTTEN: Tell me about it. Anyway, hold tight. We'll be right there in a bit. All right. Bye. Put away your gross sticks, Bob. We're going to save Molly and Gabriella. Hit it, theme song.

[THEME SONG PLAYING]

BOB: You think my Popsicle sticks are gross?

[CAR DRIVING]

BOB: These mountain roads sure are windy.

SANDEN TOTTEN: Yeah, they're fun to drive. Hey, check this out. Swoosh.

BOB: Oh, boy. I'm not feeling great.

SANDEN TOTTEN: Oh, sorry. I'll slow down. You get carsick, Bob?

BOB: I get everything sick. Carsick, seasick, rocking chair sick. It's been a rough life.

SANDEN TOTTEN: Yikes. But that reminds me. I think we got a question about this recently. Can you fire up my voicemail?

BOB: Sure.

JOHN: Hi, my name is John. And I live in Littleton, Colorado. I want to know why we feel sick if we read or look at pictures in the car. Thank you.

ADAM: Hi, Brains On. I'm Adam from Riyadh, Saudi Arabia. My question is, why do the passengers get carsick, but not the driver?

BOB: Yeah, why do some people get carsick?

SANDEN TOTTEN: Oh, I can answer this one. I studied this for our roller coaster episode. It has to do with your eyes, your ears, and your body.

BOB: My ears? I don't see how they're involved.

SANDEN TOTTEN: Well, technically, it has to do with something called the vestibular system. It's this series of tiny tubes in your inner ear. These tubes are filled with a liquid that sloshes around when you move. There are also microscopic hairs lining these tubes. And when that liquid sloshes, it bends these hairs, which in turn sends a signal to your brain telling you, hey, we're moving.

BOB: I thought the only thing in my ears was earwax.

SANDEN TOTTEN: But that's only one way your brain knows you're moving. You also rely on your eyes, which can tell you if the things around you are standing still or if they're whizzing by. And your body, it plays a role too, by letting you know if it's sensing movement.

BOB: I am certainly sensing these hairpin turns. Oh.

SANDEN TOTTEN: Oh, sorry dude. Part of what's going on is that your three systems, your eyes, your ears, and your body, they're kind of getting out of sync with each other. So your inner ears, they're sloshing with all these twists and turns. And your body is sensing some of that movement from the road.

But your eyes, they might be looking at the dashboard or the radio and thinking, hey, everything around me is staying still. So I'm not moving. And that's kind of confusing for your body. That's kind of also why it's not a good idea to read or watch videos in the car if you're already feeling kind of queasy.

BOB: I should try staring at the scenery passing by instead. Hey, eyes. Look. We are moving.

SANDEN TOTTEN: But that can be a problem too, Bob. Sorry. You see, sometimes you can see that you're moving by looking out the window seeing the scenery go by. But what if the road is smooth and straight, kind of like it just started to be right now? Your body and your inner ear, they can't really sense that movement. Now they think you're sitting still, but your eyes, they're tracking all the scenery going by. So again, things might get kind of out of sync.

BOB: Oh, great. I'm getting even sicker.

SANDEN TOTTEN: Some people are more prone to this than others. Basically, whenever your different systems are out of whack though, your stomach gets unhappy. And this is kind of cool. Get this. Some researchers think that that queasy, nauseous, stomach-churning feeling is your brain reacting as if it were poisoned.

See, before cars, if our various systems were out of sync, it was usually because we ate something bad that threw our body for a loop. So some researchers think you get nauseous when you're carsick because your brain thinks it needs to throw up some poison. Isn't that an interesting idea, Bob? Bob?

BOB: Would you mind pulling over? My body, ears, and eyes are fighting. I don't feel so good.

[CAR PULLING OVER]

[KIDS YELLING] Brains On!

GABRIELLA HOPPER: You're listening to Brains On. I'm Gabriella Hopper.

MOLLY BLOOM: And I'm Molly Bloom. Say, while we're stuck here, Gabriella, I want to make some announcements.

GABRIELLA HOPPER: Why not? Nothing else to do. This is part 5 in the Brains On road trip series. Check out past episodes for the science of engines, monster trucks, and more.

MOLLY BLOOM: And if you like Brains On, why not tell a friend about the show?

GABRIELLA HOPPER: We love it when you help spread the word. And don't forget to send us your pick for our next debate. Which do you think is cooler-- deep sea or outer space? And why? Send your best arguments to hello@brainson.org.

GABRIELLA HOPPER: And stay tuned to the end for the honor roll when we'll give a shout out to all the kids who feel our show with drawings, questions, and mystery sounds.

MOLLY BLOOM: Speaking of which, I have a surprise. I didn't lock the mystery sound in the car.

[MYSTERIOUS NOISE]

GABRIELLA HOPPER [WHISPERING]: Mystery sound.

MOLLY BLOOM: Here it is.

[MYSTERY SOUND]

MOLLY BLOOM: Any guesses?

GABRIELLA HOPPER: Actually, I think, you know how when you put your penny in and then you crank the thing and then the smushed penny comes out?

MOLLY BLOOM: Yes, I know exactly what you're talking about. So you think it's the penny smusher machine?

GABRIELLA HOPPER: Yeah, because I know the cranking sound.

MOLLY BLOOM: OK. Let's hear it one more time before we find out the answer.

[MYSTERY SOUND]

MOLLY BLOOM: Here's the answer.

NEAL: I'm Neal [INAUDIBLE] from Park Ridge, Illinois. That was the sound of me releasing my seat belt slowly in a car.

MOLLY BLOOM: So there was cranking, but it was connected to a seat belt.

GABRIELLA HOPPER: Oh, wow.

MOLLY BLOOM: That was a really loud seatbelt.

GABRIELLA HOPPER: I thought for sure I had that.

MOLLY BLOOM: I know. It was a good guess. It was definitely a good guess. I want to know what kind of seat belt that was.

GABRIELLA HOPPER: Yeah.

MOLLY BLOOM: Let's find out. The penny smusher seatbelt.

(SINGING) Ba ba ba ba ba ba ba ba ba Brains On.

GABRIELLA HOPPER: OK. So that passed a little time, but where's Sanden and Bob?

MOLLY BLOOM: I don't know, but they better get here soon. Even this amazing view is starting to bore me.

SANDEN TOTTEN: Feeling better, Bob?

BOB: Oh, yes. Much better. Thanks for letting me drive.

SANDEN TOTTEN: No problem. For some reason, being in control of a vehicle seems to reduce motion sickness. From what I've read, scientists are still trying to figure out why exactly that is. But lucky for you, it worked.

BOB: Plus, these roads are fun. Weeh.

SANDEN TOTTEN: Hey Bob, do you mind if I check a few more messages?

BOB: Oh, be my guest.

SARAH: Hi, Brains On. I'm Sarah from Tulsa, Oklahoma. My question is, when you are riding in a car, a car that's far away looks like it's going slow, but when it drives past you it looks like it's going really fast. Why do your eyes see it like that?

SANDEN TOTTEN: I never thought about that.

BOB: It's true. Look at that car down in the valley below us. It looks like it's just crawling along, but I bet it's going 60 miles an hour.

SANDEN TOTTEN: Hey, I know a guy who could totally answer this one. He's a neuroscientist at the University of Southern California.

IRVING BIEDERMAN: Hey, Irving Biederman here.

SANDEN TOTTEN: Hey, Irving. I was hoping you could help us with a question. Why do cars far away look like they're going slow, but cars near you look like they're just zipping by?

IRVING BIEDERMAN: Good question. The further away something is, the smaller. It's called visual angle. So if you hold out your thumb at arm's length, it will cover about 1/180 of your visual field, your horizontal visual field. Going from left to right, there are about 180 degrees. And your thumb at arm's length is about one degree of that.

SANDEN TOTTEN: All right. Doing that now. My thumb blocks just a tiny bit of what I see.

IRVING BIEDERMAN: So if you're holding out your thumb and you're in a room and you look at an opposite wall, your thumb may cover about one foot. But if you look at, let's say, a car that's five miles away, your thumb may cover, oh, it's possibly a half mile or 3/4 of a mile.

SANDEN TOTTEN: Yeah, if I look far away, I can block out that whole farm in the distance with just my thumb.

IRVING BIEDERMAN: So your thumb will be covering, let's say, a half mile distance. So it may take, oh, 15, 20 seconds for the car to move through that width of your thumb. But if it's right close to you, the car, let's say it's 10 feet away moving at the same speed, let's say 30 miles an hour, it will cover your thumb's distance, it may be a tenth of a second.

SANDEN TOTTEN: Oh, that's interesting.

IRVING BIEDERMAN: So psychologically, the speed of something is not in terms of its actual velocity, but how much of the visual angle a object covers in a given length of time. So that's why things that are far away seem to move slower than things that are up close.

SANDEN TOTTEN: So that explains why a plane high above seems to be moving slow even though it's actually flying way faster than a car. It's taking longer to move through your field of vision. I get it. Oh, and so you're sort of tricked into thinking it's moving slower. And that's why things nearby, they take up a lot of your field of vision so it's easy for them to pass right through, making you think they're going fast. You kind of perceive them as fast.

IRVING BIEDERMAN: That's exactly it. That's actually the core concept. It's not the absolute length or distance that something travels in terms of ground truth. It's how much of our visual field does an object cover in a given amount of time.

SANDEN TOTTEN: Very cool. Well, thanks for breaking it down, Irving. Have a good one.

IRVING BIEDERMAN: Well, it's been great talking to you. Have a good day. And remember, drive safely.

BOB: Will do.

SANDEN TOTTEN: Oh, check it out. Another message just came in.

CLYDE: Hi, Brains On. My name is Clyde. And I'm from Irvine, California. My question is, why do roller coasters feel faster than cars?

BOB: Do you have someone you can call about that one, too?

SANDEN TOTTEN: Yeah, of course. You don't have a physics professor saved on your phone? Who do you call when you have a physics emergency in the middle of the night?

BOB: You think I'm weird.

MICHAEL DENTON: Hello, this is Michael Denton. What's up?

SANDEN TOTTEN: Yo, Michael. He teaches physics and astronomy at the University of California, Irvine, Bob. Hey, I had another physics emergency I thought you could help with. Why do roller coasters feel faster than cars? I mean, you're going fast in both cases. So what gives?

MICHAEL DENTON: So the bottom line is, what we feel most often as speed is actually acceleration.

SANDEN TOTTEN: Acceleration. That's the sense of speeding up. Right? Or is there more to it?

MICHAEL DENTON: In physics we use acceleration for any change. Right? In normal discussion people use acceleration and deceleration, usually, just for speeding up and slowing down. We usually don't use the word when we turn. We say, we're turning, not, we're accelerating.

You don't say, accelerate left here. You say, turn left here. But in physics we use acceleration for any change, in either our speed or our direction. And that's what roller coasters take a lot of advantage of.

SANDEN TOTTEN: OK. So if we change directions, we call that an acceleration. Got it.

MICHAEL DENTON: So when you're in your car doing 60, 70, even 80 miles an hour, the only accelerations you're feeling are the little bumps in the road. So if you're on a smooth road going a constant speed, you don't really feel anything.

BOB: Hey, that's like how when we were driving on smooth roads before. My body didn't realize we were moving. It felt to me like I was sitting still because we weren't accelerating.

MICHAEL DENTON: Yep. Roller coasters are designed to make you feel acceleration. They have sharp turns. They have loops. They go up and down. Any change in our direction of motion is a change in our velocity. And that's what an acceleration is. And that's what our body is designed to detect. So that's really the fundamental difference between the roller coaster experience and the driving in the car.

SANDEN TOTTEN: So it has to do with the twists and turns of a coaster. So the car probably feels more like a roller coaster when we change direction a lot or go up and down hills, like when we were on that windy road back there and Bob got kind of sick.

BOB: He doesn't need to know about that.

SANDEN TOTTEN: OK. So it has to do with how often we accelerate. So if the car is going straight and at a steady speed for a long time, our bodies will just kind of get used to that and think they're sitting still.

MICHAEL DENTON: Yeah, that's right. The other slight one, of course, is that there's usually wind in a roller coaster. And wind is another form of acceleration. Even if you're moving at a constant speed through the air, every time you hit new air you're speeding it up and it's hitting your body and speeding up. So if you're in a convertible, it'll feel a little bit more like a roller coaster. You get a little more wind in your face.

SANDEN TOTTEN: Hey, so while we've got you, I was wondering, can you explain how seatbelts keep you from getting hurt when a car stops suddenly?

MICHAEL DENTON: Without a seatbelt, you generally would fly forward and hit something hard like the dashboard or the windshield or something, and stop very suddenly and would feel a greater force.

BOB: Right. Because of inertia.

MICHAEL DENTON: Yes, it's very much connected to inertia because inertia is the physics concept that basically says an object in motion stays in motion unless a force acts on it, or an object at rest stays at rest unless a force acts on it.

SANDEN TOTTEN: Wow. You knew that, Bob? Good on you.

BOB: Inertia is why I always buckle up.

MICHAEL DENTON: So once the car stops, if you were not wearing any seatbelt, the immediate thing is for you to stay in motion. And then what you're going to do is you will eventually stop, usually by hitting something hard, whether it's the dashboard or going through the windshield and hitting the ground.

What the seatbelt does is it provides some control over how your motion changes. When the car stops, instead of you just continuing to move and fly forward, the seat belt keeps you in the seat. The seat has a cushion to it. And your whole ability to stop is in a much more controlled way.

SANDEN TOTTEN: Cool stuff. Hey, I think we're pulling up to our destination. So we got to go. But thanks again, Michael Denton. Have a good day.

MICHAEL DENTON: OK. You too.

[CAR STOPPING]

MOLLY BLOOM: Sanden. Bob. You made it.

GABRIELLA HOPPER: Thank goodness. I was about to start eating pine cones for sustenance.

SANDEN TOTTEN: Never fear. We are here.

BOB: Wow. This view is eyetastic.

MOLLY BLOOM: You know what? I am so glad to see you, I'm going to let that slide. Now where's the spare key?

SANDEN TOTTEN: It's right-- Oh, man. Molly, you're not going to believe this, but--

GABRIELLA HOPPER: You don't have it?

SANDEN TOTTEN: I was just so excited to get away from Bob's Popsicle stick collection that--

MOLLY BLOOM: You came all this way without the key?

BOB: You guys.

GABRIELLA HOPPER: We're doomed. I know it.

SANDEN TOTTEN: Hold on. Hold on. I can drive back.

BOB: Hey?

MOLLY BLOOM: Hope you've got room because you're taking all of us. We are not waiting on this mountain one minute longer.

SANDEN TOTTEN: But my back seat is full of junk. I mean, I can't just leave it on the side of the road. I don't know where I'm gonna put it.

BOB: Did you then try the back door? Sometimes those get left open. Look.

MOLLY BLOOM: Wait. That door was unlocked?

GABRIELLA HOPPER: The whole time?

BOB: Well, yeah. I guess.

SANDEN TOTTEN: Bob, your keen perception saved the day. Way to go, pal.

BOB: I saved the day?

GABRIELLA HOPPER: High five up top, Bob. You're my hero.

BOB: I am? I'm the hero! Super Bob!

[CELEBRATION MUSIC PLAYING]

MOLLY BLOOM: Way to go, Bob. I am ready to wrap this road trip up. Gabriella, let's jam.

GABRIELLA HOPPER: Finally. See you guys back at Brains On headquarters.

[THEME MUSIC PLAYING]

BOB: Don't you think a hero deserves a reward? We could stop for Popsicles on the way home. I've been meaning to add a watermelon stick to my collection.

SANDEN TOTTEN: You know what, Bob? Let's do it. Let's get some Popsicles. My treat. You can even have my stick when I'm done with it.

BOB: OK. Then you have to get mango with the habit. Yippee.

[CAR DRIVING OFF]

GABRIELLA HOPPER: People get carsick when their eyes and their inner ears get mixed signals about how they're moving.

MOLLY BLOOM: Roller coasters feel faster than cars because they quickly change speed and direction.

GABRIELLA HOPPER: Cars in the distance look like they are going slowly because they have to cross a greater distance to pass through your field of vision. Cars up close only have to travel a little ways to do that.

MOLLY BLOOM: And now we're going to travel a significant distance all around the world as we read the most recent group to be added to the Brain's honor roll.

[LISTING HONOR ROLL]

MOLLY BLOOM: That's it for this episode of Brains On and our road trip. We had engineering help this week from Corey Schreppel, Roger Smith, and Johnny Vince Evans. And a massive, huge thanks to Eric Wrangham and Carolyn Hopper.

If you're a fan of Brains On, it would mean a lot to us if you took a minute to leave us a review in Apple Podcasts. It really helps other kids and parents find out about the show. Thanks for coming along on this road trip with us, and--

GABRIELLA HOPPER: Thanks for listening.