Smash: When continents collide!

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

ANNOUNCER: Brains On is supported in part by a grant from the National Science Foundation.

MAN: The Great Himalayas, the deep-sea Marianas Trench, the highest peaks, the lowest valleys, all brought to you by tectonic plates!

[DRAMATIC MUSIC]

As we speak, massive plates of earth are crashing into each other, sliding past each other, and diving under each other, creating forces strong enough to lift mountains or shake the planet. Look at them go!

AVA: Yeah, nothing's moving.

MAN: Just look closely!

MOLLY BLOOM: I don't see it.

MAN: Right there!

AVA: What?

MAN: It's just-- slow, that's all.

MOLLY BLOOM: Um--

MAN: The plates only move an inch a year. So just wait.

MOLLY BLOOM: I think we should start the show.

MAN: No. No, no, no, no. Hold on. Any second now.

AVA: Yeah, um, you keep waiting to see those tectonic plates move. We're going to do an episode. Keep listening.

MAN: Wait for it. Wait for it.

[MUSIC PLAYING]

MOLLY BLOOM: I'm Molly Bloom. And you are listening to the one and only Brains On from American Public Media. Thanks for being here. With me today is 9-year-old Ava from Baltimore, Maryland. Hi, Ava.

AVA: Hi, Molly.

MOLLY BLOOM: Today, we are talking tectonic plates.

AVA: Those are the massive, mega slabs of rock covering all of our planet's surface.

MOLLY BLOOM: And yes, they do move very slowly, about as fast as your fingernails grow.

AVA: That's pretty slow.

MOLLY BLOOM: Yeah, but these plates are super important.

AVA: In fact, the land you're on right now, no matter where you are, is sitting on a tectonic plate.

MOLLY BLOOM: Even if you're listening to Brains On in a boat on the high seas.

AVA: Like a pirate.

MAN: Arrr.

MOLLY BLOOM: Even then, under all that water, there is a place--

MAN: There is? I mean, arr, I knew that.

AVA: They're everywhere.

MOLLY BLOOM: That leads back to the question that you first sent in to us, Ava.

AVA: How did the continents form?

MOLLY BLOOM: That is a great question. A continent is a large connected landmass. And we typically say there are seven of them. Do you know them all, Ava?

AVA: Antarctica, Australia, Europe, South America, North America, Africa, and Asia.

MOLLY BLOOM: Oh, you got it. So good. So what got you thinking about this question?

AVA: My dad showed me a drawing of all the continents clumped together, which got me thinking, how did the continents form in the first place.

MOLLY BLOOM: So yeah, once upon a time, the continents were all in one supercontinent. And we call it Pangaea. So what did that look like to you when you saw those continents clumped together?

AVA: I just thought it looked really weird and different.

MOLLY BLOOM: Well, over a long time, those continents, they drifted apart thanks to tectonic plates. And we'll explain more about how they did that in just a bit. But first, we're going to tackle some questions from our listeners.

LUCILLE: Hi my name is Lucille. I'm seven years old. And I'm from Tacoma, Washington. My question is, how are mountains and mountain ranges formed?

HANNAH: Hi, my name is Hannah.

NOEL: And my name is Noel. We're from Aviano Air Base in Italy.

HANNAH: Our question is, how do earthquakes make mountains grow?

MOLLY BLOOM: Mountain ranges are actually the result of plate tectonics. How so? Let's have our favorite extreme chef explain.

[MUSIC PLAYING]

GRIFF JENKINS: Hey, everyone, celebrity chef Griff Jenkins here with my assistant Benny. You may know us from one of my many shows, like Totally Rad Pies or Mega Pudding Bars.

[MUSIC PLAYING]

BENNY: Or your old public television show Dainty Decorative Gourds With Griffin.

GRIFF JENKINS: Benny, that show's way old and totally off brand for my new, extreme persona.

BENNY: Right, sorry.

GRIFF JENKINS: Where was I? Oh, yeah, I hope you brought your parka because it's about to get super cool. We're learning about plate tectonics.

BENNY: Plates are cool. Should I get out the fine china set? The sky blue ones would look great with the new doily placemats we made together last week.

GRIFF JENKINS: Doilies? What? I don't remember making those. I think you mean that time last week we rode BMX bikes through flaming hoops of flame. Gnarly! Ha ha!

BENNY: No, these doily placemats right here. Your stitch work is really shaping up, Griff.

GRIFF JENKINS: Oh, yeah, those. Whatever. We're not talking about china plates, Benny. We're talking about the giant plates of rock covering the planet. Rock plates are extreme.

[ENGINE REVVING]

Let me show you how they work. Here, I have a giant peanut M&M I made especially for this demo. It's got peanut at the center, chocolate around that, and a hard candy coating outside.

BENNY: Wow! It's as big as a basketball. And you painted it to look like the Earth. Nice work.

GRIFF JENKINS: Ha ha, yeah, buddy. My candy decorating skills are intense.

[MUSIC PLAYING]

Now, imagine this is the Earth.

BENNY: OK, imagining.

GRIFF JENKINS: The giant peanut in the middle is the core of the planet. It's a dense ball of heavy metal, which is totally metal.

BENNY: Woo-hoo.

[MUSIC PLAYING]

GRIFF JENKINS: Now, all around that peanut center is what, Benny?

BENNY: Mm, chocolate.

GRIFF JENKINS: Exactly. [LAUGHS] Like this M&M, the Earth has a layer around its core too. We call that layer the mantle. It's so hot, it's actually an oozy, soft, rocky goo. So let's microwave this M&M to soften the chocolate, shall we, buddy?

BENNY: You got it, Griff.

[MICROWAVE BEEPING]

GRIFF JENKINS: Great. That way our peanut M&M will be more like the Earth. We have a dense core, soft, gooey middle, and the hard candy shell. Even when the chocolate mantle is very soft, the hard candy coating keeps it from spilling out. Similarly, Earth has a hard rock layer on top that keeps us all from being swallowed by hot, gooey mantle rock.

[MICROWAVE BEEPS]

BENNY: Here's your hot, giant, Earth-looking M&M, Griff.

GRIFF JENKINS: Bodacious, Benny. [CHUCKLES] Now drop it on the floor.

BENNY: What? It's so lovely.

GRIFF JENKINS: Don't worry. It's part of my extreme demonstration.

[EXPLOSION]

BENNY: OK, here goes.

[CRACKLING]

GRIFF JENKINS: OK, now check it out.

BENNY: Huh?

GRIFF JENKINS: When I pick it back up, you can see the hard candy shell is broken into lots of sections.

BENNY: It was so perfect. Now it looks like a cracked egg.

GRIFF JENKINS: Don't fret, bruh. Now it's even more like the Earth because the top layer of the Earth is called the crust. And it too is broken into cracked pieces called tectonic plates.

BENNY: Oh, wait. I get it. Those massive plates of rock you were talking about, they're like the pieces of hard candy on your giant M&M.

GRIFF JENKINS: Up top, buddy. You got it.

[MUSIC PLAYING]

So because the chocolate inside is so melty and gooey, I can actually slide pieces of this hard candy shell around a little bit, like this.

[SQUELCHING]

BENNY: Oh, the pieces of candy shell are pushing into each other. Over there, they're crunching up and forming ridges.

GRIFF JENKINS: Astounding observation!

[ROARING]

That's similar to how the tectonic plates push against each other and pile up rock to form mountains.

BENNY: Oh. Oh! And over there, when you push that bit of shell under the other one, some chocolate squirted out through a crack.

GRIFF JENKINS: That's basically how volcanoes work, Benny, my man. When one plate gets pushed under another, some of the hot magma under the Earth's crust can find a way to burst up and spill out on the surface. Mega magma explosion!

[MUSIC PLAYING]

BENNY: Oh, no, Griff. Your hands are getting covered in chocolate. Let me get you something to clean that up with.

GRIFF JENKINS: Most definitely. I don't want to get chocolate over this nice, white shirt. I keep my laundry extremely clean!

[MUSIC PLAYING]

Check it. The Earth is sort of like a melted peanut M&M, with a dense core at the center, a gooey inner layer, and a hard shell on top that's broken into giant plates. Those plates slowly slide around, pushing into and diving under each other.

BENNY: Here's a wet nap, Griff.

GRIFF JENKINS: Ooh, lavender-scented.

BENNY: Mm-hmm

GRIFF JENKINS: My favorite.

[MUSIC PLAYING]

OK, until next time, stay righteous, everyone.

[MUSIC PLAYING]

AVA: I never knew the Earth was so delicious.

MOLLY BLOOM: Right? In real life, when the hot magma from the mantle oozes up on the surface, it eventually cools down.

AVA: When it cools, it hardens to form new rocks that become part of the plates on the crust.

MOLLY BLOOM: This helps build up the crust. And fun fact, the word "tectonic" is based on the Greek word for "building."

AVA: "Tec-ton-ic," sounds like a style of electronic music.

MOLLY BLOOM: It does. We should have a mini dance party.

[MUSIC PLAYING]

Oh, anyway, that gooey mantle under the plates is always flowing, dragging the plates with it. Eventually, one plate will get pushed under another where it will be forced to slide down into the hot, gooey mantle.

AVA: Then it heats up, mixing back with the goo it came from.

MOLLY BLOOM: It's sort of like a cycle happening over millions and millions of years.

AVA: Not only do these plates make volcanoes, they also make earthquakes.

MOLLY BLOOM: Those happen when two plates slide against each other. They get stuck and build up tension.

AVA: When the tension is finally enough to break them loose again, watch out! Earthquake!

[MUSIC PLAYING]

MOLLY BLOOM: Now, let's get back to your original question about the continents, Ava.

AVA: Here to help us answer it is Kate Scharer. She's a geologist with the US Geological Survey in California. Hi, Kate.

KATE SCHARER: Hi. How are you doing?

AVA: Good. How did the continents form?

KATE SCHARER: A continent needs to have two things to happen for it to form. First is that that hot, gooey mantle comes up onto the surface, it melts, and gets squirted out in volcanic eruptions. And so that builds up the plate slowly over time. But the other thing that's kind of cool is that we also see that the lighter minerals-- those are the little fragments that make up all the rocks-- actually separate. And we get lighter ones that tend to float on the surface of the Earth, sort of like leaves and sticks do on a pond. And those tend to accumulate on the top and form the light crust that we get to walk around on today.

AVA: Are the continents still forming? Or has it just completely stopped?

KATE SCHARER: Yeah, the continents are still forming today. So we see the volcanic eruptions going on. And they've been forming for hundreds of millions of years. For example, we used to have Pangaea, where they're all clumped together. And now we see that the continents are spreading apart in some places, like America and Europe are moving farther apart from each. In other places, they're actually smashing together, like, for example, where the Himalayas are being made, where India is smashing into Eurasia.

AVA: Wow.

MOLLY BLOOM: So Pangaea, the supercontinent, how did that first get to be on our planet?

KATE SCHARER: Through plate tectonics. [LAUGHING]

MOLLY BLOOM: Hey, good answer.

KATE SCHARER: Yeah, you could think of the plates are always moving around, and so it's a little bit like bumper cars. Sometimes they just all get clumped up into the corner.

MOLLY BLOOM: So did they start there?

KATE SCHARER: So we don't know what it looked like when they first began. We can only see remnants of the original crust. So for example, if you go to the big continents, like North America or Australia, you can find continental crust that's 4 billion years old, which is pretty old.

And we know that then Pangaea formed much later, several hundred million years ago. The intervening time period, we don't know as much about what the shape of the Earth was like or the organization of the tectonic plates were. And so when you look at an image, like the configuration of Pangaea, what you're seeing is the tectonic plates, at some point, just got all clumped together on one part of the globe.

AVA: Maybe you can help us answer this question from Elsa.

ELSA: My name is Elsa from Decatur, Georgia. And my question is, why do the plates of the Earth move?

KATE SCHARER: Part of the answer is that the Earth is still really hot. All the way down in its core, deep down there, it's about 10,000 degrees, so like a pot of water boiling on the stove where you can see the water churning and spinning. And as you watch that, what you're watching is the pot of water trying to get rid of the heat from the stove and release it out into the air. The same thing is happening with the Earth where the heat from the core is trying to get out. And as it does that, it causes the mantle to flow. And also that mantle flowing causes the Earth's crust to be dragged around. And thus, you're moving the tectonic plates.

AVA: That's cool. What do you think the Earth would look like in a million years?

KATE SCHARER: That's a good question. Some of the continents will be closer together. And some of the continents will be farther apart. We might see that there's a new volcano that's been formed, along the Hawaiian chain, for example, because that's a place where the plates are moving over what we call a hotspot, where there's basically sort of a blowtorch pushing heat up out of the core and forming these new volcanoes. So as the Pacific plate moves over it, a new volcano might be formed by then.

AVA: Thanks, Kate.

KATE SCHARER: Thanks, Ava, for your questions. They're really good. You're quite a professional.

AVA: Thank you for your answers. Bye.

KATE SCHARER: [LAUGHS]

[MUSIC PLAYING]

MOLLY BLOOM: Feeling curious? We love hearing your questions.

AVA: Send them to Hello@BrainsOn.org.

MOLLY BLOOM: That's how we got this one from Cole.

COLE: Hello, my name is Cole Bryant. And I am eight years old. And I am from Indianapolis, Indiana. And my question is, why does your breath smell worse in the morning?

MOLLY BLOOM: We'll answer that question. But don't hold your breath for it. It'll come at the end of the show in our moment of Um. Plus, the latest group to join the honor roll.

AVA: Want to hang with us on social media? We're on Facebook, Instagram, and Twitter.

MOLLY BLOOM: Look for Brains_On. And if you have a moment, tell a friend about the show.

AVA: Personal recommendations help us grow. Thanks.

[MUSIC PLAYING]

MOLLY BLOOM: Today, we're talking tectonic plates with Ava. Ava, what so far has really stood out to you from this episode?

AVA: I thought it was super cool that the continents are still forming and they might look totally crazy in a million years.

MOLLY BLOOM: Yes, I agree. That is a mind blowing fact. And speaking of mind blowing, I hope you're ready because it's time for the--

[MUSIC PLAYING]

ANNOUNCER: (WHISPERING) Mystery sound.

MOLLY BLOOM: Here it is.

[BOOMING AND THUMPING NOISES]

OK, what is your guess?

AVA: I think it's a dump truck dropping things off in the dump.

MOLLY BLOOM: That is an excellent guess. Well, keep thinking about it. And we're going to have the answer in just a bit. But first, back to continents.

AVA: Since the continents are part of the tectonic plates that move, the continents too have moved a lot over millions of years.

MOLLY BLOOM: But even though these plates have been moving for millions of years, this idea is relatively new to us.

AVA: Here to explain how scientists figured all of this out is our pal John Lambert.

JOHN LAMBERT: The idea that continents can actually move is really pretty radical. I mean, just look around. The ground isn't moving. It's well, you know, solid. How on earth did scientists think up such an idea? And how did it move from a crazy notion to accepted fact? Turns out that the theory was only seriously put forward about a hundred years ago. I got in touch with Naomi Oreskes to help me tell this story.

NAOMI ORESKES: I'm Professor of the History of Science at Harvard University. The person who's generally most credited with developing the theory of continental drift is the German geophysicist Alfred Wegener.

ALFRED WEGENER: Guten tag.

[MUSIC PLAYING]

JOHN LAMBERT: Alfred Wegener was a pretty cool guy. He pioneered the use of weather balloons to study the atmosphere.

ALFRED WEGENER: I like balloons.

JOHN LAMBERT: He made the longest trek across Greenland on foot.

ALFRED WEGENER: So much walking.

JOHN LAMBERT: And he was especially interested in the paleoclimate, or understanding how the climate has changed over Earth's history.

ALFRED WEGENER: What can I say? I'm a curious man of many interests.

JOHN LAMBERT: The story goes that he dreamed up his theory of continental drift while recovering from a wound that he suffered fighting in World War I. Naomi Oreskes says that he spent his days in bed reading scientific papers about how the Earth's climate had changed. And come on, I mean, who hasn't spent a whole day in bed reading geological literature? Anybody? Anyone?

NAOMI ORESKES: And he was also looking at maps because he was trying to think about what kinds of changes could explain why you could have ice ages in the tropics or tropical plants in what are now Arctic regions.

ALFRED WEGENER: It is just so bizarre, evidence of blizzards in Bermuda, of palm trees in Antarctica. How can I make sense of this?

NAOMI ORESKES: When he was looking at these maps, he saw the obvious fact that the continents seem to fit together, that the outlines of South America and Africa were extremely similar and seemed like they would fit together.

ALFRED WEGENER: It looks a bit like a jigsaw puzzle. Hmm.

NAOMI ORESKES: He also found that there was very extensive evidence of similarities between the fossils between Africa and South America and other places on Earth.

ALFRED WEGENER: How could identical fossils of animals and plants exist across an entire ocean? It's not like fossils can build boats and sail the seas to bury themselves somewhere else. Or can they? No. No, they can't. Hmm, what a puzzle.

NAOMI ORESKES: He also saw evidence in the geological record of similarities in the rocks that had been deposited. So he began to think about this, because why would the rocks be so similar in continents that are today very far apart?

ALFRED WEGENER: If the coasts are similar and the fossils are similar and the rocks are similar--

NAOMI ORESKES: And so he began to think, well, one explanation for that could be that if these continents had previously been united, that would explain why the rocks and fossils were so similar. And then if they broke apart and they began moving across the face of the Earth, that could explain why the climates had changed, because the continents had moved, in some cases, from temperate regions to Arctic regions or vice versa.

ALFRED WEGENER: Eureka! I've got it. One supercontinent to explain them all. It's brilliant.

[MUSIC PLAYING]

MOLLY BLOOM: So Wegener proposed the idea, but he couldn't prove it. We'll hear how other scientists picked up where he left off in a minute. But first, let's go back to that mystery sound, Ava.

[BANGING AND THUMPING NOISES]

OK, before we guess again, I'm going to give you a couple of hints. The first is that it's related to tectonic plates in some way. And the second is that this is a very hard mystery sound. And it's probably not something you've necessarily heard in your everyday life. So what do you think might make that sound?

AVA: A volcano?

MOLLY BLOOM: To find out the answer, we're going to turn to Ben Holtzman, a geophysicist at Columbia University.

BEN HOLTZMAN: That sound we just heard was an earthquake in Niigata in Japan in July of 2007. It was a magnitude 6.6, recorded by a seismometer on the main island of Honshu, not very far from the earthquake itself. So you hear many little aftershocks after the main shock.

MOLLY BLOOM: So an earthquake. So now that you know that, does it kind of sound like it makes sense?

AVA: Yeah, kind of.

MOLLY BLOOM: Let's hear Ben explain a little bit more about this. He works at the Lamont-Doherty Earth Observatory where he uses seismometers to record these very small motions in the ground.

BEN HOLTZMAN: Motions that are so small that you can't even see them, let alone feel them.

MOLLY BLOOM: Maybe you've seen some of these frequency measurements graphed out. There's a scrolling piece of paper under a pen that keeps moving up and down. And you get this kind of squiggly line. That's actually a translation of data from a seismometer. And Ben can take that same data and translate it into a different kind of squiggly line, a sound wave.

BEN HOLTZMAN: Those frequencies aren't things we can actually hear. So we're taking the data from the seismometer into a program that lets us convert it into a sound by speeding it up.

MOLLY BLOOM: People do hear sounds during an earthquake, but they're not the sounds of the Earth itself moving.

BEN HOLTZMAN: Nope. If you hear anything, you'd be hearing what are called secondary sounds. The seismic waves cause other motions, like they cause grinding of the sidewalk against another piece of the sidewalk or parts of a building against another bit of building.

[BANGING]

MOLLY BLOOM: By studying earthquakes and aftershocks, Ben hopes to get a better understanding of earthquake cycles. Seismometer data can help show whether or not there is still enough pressure in the Earth for another quake. To hear more and see videos of the seismic events Ben Holtzman and his collaborator Jason Candler have recorded, head to SeismicSoundLab.org. They've done some really cool visualizations there of what earthquakes and aftershocks look like.

[JINGLE PLAYING] Ba ba, ba, ba, ba, ba, ba, ba, ba, ba, brains on.

OK, back to how we first proved plate tectonics is a thing. Remember, we just heard that this guy, Alfred Wegener, came up with the idea that the continents move. John Lambert takes it from here.

JOHN LAMBERT: No one at the time could prove that Wegener's idea was correct. But fast forward a couple of decades, past another massive World War, people began finding evidence in strange places that made continental drift go from a crazy idea to accepted fact. There are a couple of key reasons why. First up, magnetic rocks.

When rocks form, they have minerals in them that point to the magnetic North Pole, kind of like a compass. Once they harden, those minerals stay put. And geologists can measure where they are pointing. Geologists looked at rocks all over the globe and weren't quite sure what to make of what they found.

GEOLOGIST 1: As I go down through this rock layer, the direction the rocks are pointing gets all wonky. It changes. It's like the Earth's magnetic pole is wandering around the globe over time. But why would that happen?

GEOLOGIST 2: Or-- oh, oh, oh, oh, oh, oh, what-- what about this? The magnetic pole isn't moving. The continents are moving.

GEOLOGIST 3: I know, it's Santa. He moves the North Pole every few years so we don't track him down and steal all the presents. I'd totally steal the presents if I could.

GEOLOGIST 1: Um, yeah, I like the other idea. Maybe the continents move.

NAOMI ORESKES: So that was a testable hypothesis. And so the scientists went all over the world-- they went to India, China, Australia, and North America and started collecting rocks from all these different places. And they showed that the different continents had different apparent polar wandering paths.

ALFRED WEGENER: Yes, vindicated by science.

NAOMI ORESKES: And that was a really key piece of evidence that made a lot of scientists say, oh, we really need to think again about continental drift.

JOHN LAMBERT: The final piece of the puzzle fell into place when scientists discovered that the sea floor is actually spreading apart. This is happening along a mid-Atlantic mountain range. Lava oozes up and forms new land, which pushes the sea floor in opposite directions. This seafloor spreading is the driving force that actually moves tectonic plates. Scientists had finally figured it out.

NAOMI ORESKES: Now you have evidence, not just the continents are moving, but that the oceans are moving as well. And that combination was what, for most people, was the crucial thing to say, oh, yes, this is real, this is true, this is happening.

[MUSIC PLAYING]

One of the things I love about this story is that it isn't the work of just one person. Alfred Wegener played an important role because he, in a sense, began the conversation. He had an idea and he stimulated what, in the end, turned out to be a really important scientific development. But many, many people contributed to it along the way.

And so I think the story helps refute a myth that many people have about science, that science is the work of lonely geniuses, a brilliant individual all by himself, and it's all men, which it's not. So it's actually a tremendous amount of science is teamwork, it's different people approaching a question from different angles and bringing the different pieces to the puzzle. You don't have to be a genius to make an important contribution. You just have to be working and thinking and open-minded.

[MUSIC PLAYING]

AVA: The Earth is covered in massive sheets of rock called tectonic plates.

MOLLY BLOOM: These plates are floating on a layer of gooey rock called the mantle.

AVA: All seven continents are sitting on plates. And the plates move.

MOLLY BLOOM: But they move very, very slowly, about an inch a year.

AVA: Still, it's because of these plates we have volcanoes, mountains, earthquakes, oceans, and much more.

MOLLY BLOOM: That's it for this episode.

AVA: Brains On is produced by Molly Bloom, Marc Sanchez, and Sanden Totten.

MOLLY BLOOM: We had production help from Lauren Dee, John Lambert, Emily Allen, and Carol Zoll,

AVA: And engineering help from Michael Demark, Bob White, and Veronica Rodriguez.

MOLLY BLOOM: Many thanks to Eric Gringam, Lauren and Ryan Purlin, Peter Cox, Nancy Liebens, Christine Hutchins, Euan Kerr, Tracy Mumford, Ken Hudnut, and Jason Candler.

AVA: And before we go, we got to have a MOMENT of Um.

[CHORUS OF PEOPLE SAYING "UM"]

COLE: Why does your breath smell worse in the morning.

MICHAEL EGGERT: Well, I'm Dr. Michael Eggert. I teach in the dental school at the University of Alberta. I'm a periodontist, which is I deal with people who have problems with their gums. But I also teach preventative dentistry, which is how to avoid having-- among other things, how to avoid having tooth decay.

[MUSIC PLAYING]

My research is into bacteria and biofilms that bacteria make that grow in the mouth, particularly around the teeth. When we sleep, we don't produce as much saliva as we do when we're awake. So things kind of slow down in our mouth when we're sleeping.

That has implications for your mouth health in general, such as things like tooth decay, but specifically, for your question, it means that when everything slows down, the bacteria that grow in our mouths get a chance to concentrate what they do. Because normally, when we're awake and we're swallowing all the time, which we do without thinking about it, we flush things away from the mouth and keep our mouth fairly moist. And so, at that point, we don't have as much obvious bad breath as we might just after we wake up.

I wouldn't say that there are bad bacteria. It's just is that some people have more of them than others. I think that some families might have members that have more bad breath than other members. It can relate to how much saliva you produce, how much salivation you do. So if you have a dry mouth, you can have more odor.

[MUSIC PLAYING]

MOLLY BLOOM: There's nothing stinky about the latest additions to the Brain's Honor Roll. These are the kids who keep the show going with their ideas. Here are the newest honor rollees.

[LISTING HONOR ROLL]

[MUSIC PLAYING]

See you next week.

AVA: Thanks for listening. Stay righteous.

[MUSIC PLAYING]