Australia is moving north by about 7 centimeters each year. It's the fastest moving continent and it moves so quickly, GPS systems have to be updated to keep pace. On this continent, you will find fascinating animals and many different ecosystems, but no active volcanoes or geysers.
You see, volcanoes don't pop up randomly. 75% of all of Earth's volcanoes are along the borders of the Pacific Ocean, in a region nicknamed the Ring of Th- fire. If you look at a map of the world's volcanoes, it matches closely to a map of the world's tectonic plates. But what exactly is a tectonic plate? And how can something as big as Australia be moving?
I'm Science Mom. I'm Math Dad. Today we're going to learn all about the structure of our planet.
Hello and a quick welcome to Pickle Obsessed watching in Minnesota, to Karis from Illinois, to Noah watching in Utah, Eleanor in Canada, and Adley, Ailyn, and Owen from West Virginia. Happy Wednesday. Happy Wednesday indeed.
Before we get started talking about plate tectonics, I want to start with the question of what is inside our planet and how do we know what's inside our planet? It's lots of rocks. I know I've dug in my backyard and it just...
sand and rocks. That's got to be what it's in. What's in there, right? Well, if we think that earth is made of the rocks, like what we can see, then we have a problem because earth is actually heavier than it should be.
So quick little example of this, just for fun, math that I have two bags here. And one of these bags has our dog's favorite chew toy. And one of them does not. And I want you to see if you can tell without looking.
So there's paper on the top of both of these, but now I'm going to hand them to you. Okay. What do you observe?
Okay, so this one is much heavier, half the weight of my dog. I do not think this is a chew toy. So this one weighs about half as much as our dog weighs, and this one is really light. That tells you something about what's inside these, right? Yeah, one of these I could take a hit to the head with, and the other one, not so much.
So let's pull out the paper real fast and reveal what's in here. In here, my bag has a nice little toy, your bag. A five pound weight.
Has a five pound weight. And you could tell by lifting up that bag, you could tell it was way heavier, right? Way heavier.
Way heavier. You're saying the earth is kind of the same way. It's heavier than we would expect it to be.
It is. Now, how can you weigh something that is floating in space, an entire planet? Well, this was done-Giant scales.
No, not giant scales. This was done back in the 1800s with a scientist who very carefully had a pendulum and measured the attraction between two- little weights. Gravity is the attraction between objects, and the heavier or the bigger something is, the more gravity it has.
And using that, this scientist was able to calculate the weight of the entire planet. And just like our bag that had a five pound weight in it, the weight of Earth was heavier than it should be. If you just dig up some rocks and weigh the rocks, Earth is heavier than those rocks. And that means there has to be something heavier inside our planet.
And they guessed probably it's iron because iron is heavy. Okay. Now that's pretty cool because you can't dig a hole that far.
At least my arms would get tired. The deepest holes that we have dug have not gone all the way through the outer layer of the earth. The outer layer of the earth is the crust.
It's called the crust. And it's just like what we walk around on. It's the rocks that you see. And if you dig a hole.
You'll keep going through more rocks, and the rocks are hard, and they are brittle, and they are solid. But you're saying that the crust comes to an end if you go far enough down. If you go deep enough.
How far? You have to go about five kilometers if you're digging through rock at the bottom of the ocean. But if you're digging through rock on land, it can be anywhere between 10 and 70 kilometers. Oh, wow. The thickness varies.
Now, how do we know this? If we haven't actually dug down to the next layer. How do we know that there is a next layer? Well, sound waves have something to do with it.
Let's pull up our first picture in our slideshow because there's a similar question that we sometimes have if we have maybe a foot that hurts. If your foot hurts really bad and you can't walk on it, you might go to the doctor and get x-rays. And those x-rays will show you what the bones inside your feet look like, but you don't have to cut open your foot to see the bones. You can see it because the x-rays travel differently through different material. And your bones are harder than the skin and the muscle around them.
And we can do the same thing with our planet. But instead of using x-rays, what we're going to use is earthquakes. Earthquakes? Yes, earthquakes.
This sounds dangerous. When earthquakes happen, there are machines called seismographs all over the world. And those seismographs are very sensitive.
They can measure an earthquake that is so small. that you and I don't feel it. And there are earthquakes happening all the time that we don't feel. They're not strong enough to actually shake our bodies or move our houses, but they are strong enough for the seismographs to detect them. And when an earthquake happens, if the earth was completely solid and it was all made of the same material, then the earthquake wave would travel all the way through to the other side.
And of course it wouldn't be quite as strong when it got to the other side of the planet. but it would travel in pretty much a straight line. If the earth just had a solid core made out of iron that was denser and heavier than the rest of it, then our earthquake wave would go through and it might bounce or move a little bit, but it would still travel all the way through. Okay.
Now here is a really cool fact. When you have earthquake waves travel through, there are two different type of waves. We call them P waves and S waves.
And we'll talk a little bit more about waves in another class, but S waves don't travel through liquid. You can kind of think of it as like they get absorbed through liquid. And it turns out the Earth has a pretty big shadow area where the S waves disappear.
And if you have an earthquake that happens right here, then you have this shadow over here where there are no S waves detected. So somehow they're being gobbled up by monsters. No, by a liquid. This is how scientists discovered that there had to be a liquid center to our planet and that they knew what size it was.
They won't travel through the liquid. Yes, because the S waves don't travel through the liquid. And with studying the types of waves and how they move, scientists were able to get a picture of the planet, just like you can get a picture of your foot when you go to a doctor and they take an x-ray.
By looking at the P waves and the S waves and how they reflect and interact, scientists discovered that we have an inner core that is made out of liquid. And sorry, I said that backwards. We have an outer core that is made out of liquid.
And then we have an inner core that is solid. And then this layer here above the core is called the mantle. And then just the outermost part is the crust?
And the very outermost part is the crust. Now, if we go to the notes, we're going to go, I think, to page 64 of the notes. I want to emphasize just the scale of this.
So this is actually the page we'll be talking about on Friday when we do our art project. But this is drawn about as close to scale as I could make it. And look how thin five kilometers is. So this thickness of that line, that is about as thick as the crust is on the oceans, under the oceans of our planet. And then when you have the continents.
They're sort of like, it's kind of like they're floating or sinking into that mantle. The crust there is thicker. But still, compared to this distance, this is not very thick.
No, it is not. It kind of reminds me of the atmosphere not being very thick either. Just a thin shape.
We use the analogy of an apple peel around an apple. Yeah, the crust is the same way. The crust is really thin. You can almost think of it as like an eggshell.
And most of our planet, if you're looking at it just by... by weight, most of our planet is the core and the mantle. The core is about the size of Mars. But remember, how many planet Marses could we fit together to make Earth?
It was six. It was six. We talked about this last class. So if the core is one Mars planet that's equal to the size of the core, then how many Mars planets make up the mantle and the crust? Well, most of the five then.
Yeah. Oh, yeah, five others. And the crust, you said, was not much at all. And the crust is very thin. So the mantle would be almost five Marses worth.
84% of the volume of our planet is the mantle. That is really, really big. So the mantle is super important.
And now if we go two pages earlier in the notes to page 61, let's label these real quick and talk about that. Oh, thank you, Math Dad. It is page 62. So this first layer at the very top, we call the crust.
And the crust is solid and brittle. And if you take a rock and you put a lot of pressure onto it or you bend it, it will break. So when we think of the earth and rock, we're usually thinking of the crust. Yes. That's all that we've ever experienced.
Has anybody ever journeyed down to the mantle? No. The deepest.
If you did, it would be like lava. Well, here's the thing. And let's go back to a big view really quick because I want to share a quick story. When I was a kid, I had a little bit of a fear of digging deep holes and thought that if people dug a hole too deep. that then it would just be like boiling lava and that lava would just shoot up like a geyser and that that's what would happen if someone dug a hole too deep and they went all the way down.
And that made me a little nervous to think about the crust being thin. This is not how it works. The mantle is solid.
Say that again. The mantle is solid. It is not liquid, but it is a plastic solid. So let's talk about liquids versus solids. Here, Math Dad, what is this?
Liquid, definitely a liquid. It is. It is water with green food coloring, and it is very liquid.
That means it can move around, and lava is also liquid, although it's more like syrup, right? If you see a lava flow coming out of a volcano, it's not running like water. It's flowing like a thick syrup.
This is a piece of saltwater taffy, two of them stuck together. So I have a little piece of candy here, saltwater taffy. I put two of them together so it would be a little bit bigger. Is this solid or liquid?
Mmm. Oh, it's solid. It's solid.
And you would like to eat it, right? How yummy taffy is. Yes. Taffy is delicious.
It is solid, but it is a plastic solid. And if I apply pressure to it, I can bend it. It's like a solid that's trying to pretend to be a liquid.
And if I pull on it slowly, I can stretch it. But watch what happens if I pull fast. If I pull fast, it can snap. So mantle is much the same way. The mantle is solid, but it's a solid that can move over time.
And when I say time, I mean a lot of time. It takes hundreds of thousands of years for hot mantle near the core to move up toward the crust, and then it will cool and start to come back down hundreds of thousands of years. So it moves very slowly, but it does move. And-Okay. plastic solid.
Let's go back to our notes real fast and finish this out. So I'm totally wrong. So the mantle is solid. Yes.
It's a plastic solid. And then we have our inner core. So that's the outer core. Oh, thank you, Math Dad. That's why she keeps me around.
Sometimes it is hard to write and talk at the same time. We have our outer core, and this is liquid. And we have our inner core, and the inner core is solid. And the reason why we know that the inner outer core is liquid and the inner core is solid is because we've essentially used earthquakes and those waves of the motion. They're kind of like sound waves almost.
We've used that like a big X-ray to see what we can't actually dig down and get our hands on because we can't we can't dig down to the center of the earth. It's way too hot. So Pickle Obsessed was asking about Jell-O because it's.
kind of trying to be solid and liquid or it's got characteristics of both i would say it's a solid yeah kind of weird it's not always as black and white as we try to paint it it's not and jello is a solid you know like a matrix that has a lot of water in it and it does behave differently depending on what stresses are put put into it so back to back to our core i want to talk just a little bit about how our core works because our core is just essential for life on earth And it actually functions kind of like a huge magnet. So do you remember when we talked about different types of energy? We talked about how a lot of our energy systems involve spinning a magnet.
Right. So if you have wind power, the wind spins turbines, which then turn a magnet and create electricity. This little handheld flashlight, if I crank the handle, I'm spinning a magnet inside. And because there is metal.
inside that magnet that's spinning, I get an electric current. Well, our core, because we think it's made out of nickel and iron, and those are magnetic elements, the core is actually creating electric currents, which then create a huge magnetic field. And I've got a picture of our magnetic field, an artistic representation of the picture in this next slide. And that looks kind of crazy. That looks like some sort of giant Spider-Man symbol or something.
But it is. And if you were looking at our planet from space, it would not look quite like this. You wouldn't see all these colors.
But the fact is there is a huge amount of radiation coming from our sun all the time. And then because our planet has these lines of magnetism going out the North Pole and in the South Pole, it creates a shield. And then that radiation pushes that shield and it ends up stretching way behind our planet. And this is the magnetic field. So this is a representation of what it would look like.
But really, these magnetic lines are invisible to our eyes. So it's actually protecting us. It is. From those.
The sun blast? What's the sun shooting at us? Solar wind is what we call it. And it's light and energy, but also some really high energy particles that over time, they would actually blow the atmosphere away.
If we didn't have a magnetic field, we would lose our atmosphere. And that's what happened to Mars. Mars at one point had a much thicker atmosphere and it had liquid water. But because it does not have a magnetic field to protect it, not one as strong as what Earth has, then...
the solar wind has taken away most of Mars's atmosphere, has blown into space. Okay, the reason that Mars doesn't have the magnetic field is because its core has cooled too much, so it doesn't have a spinning core. Yeah, it doesn't have that liquid spinning part of its core.
That's what we were talking about last time. Yeah. Kind of amazing, right? It all comes together. There are some mysteries with our magnetic pole, though, that we don't understand, and this, I think, is quite exciting, because if you go on to study geology, Maybe you could be the person to discover the answer to this.
Our magnetic field goes north to south. And to explain this, let's take a look really fast at a compass. So you guys have probably seen a compass before.
It's just a piece of metal that is magnetized. And that little red dot in the compass, that will always point north. Well, here at Math Dad, let's go back to our main view.
I have a magnet right here. And wait, I should have... You already saw the answer. Pretend like you didn't see that, Math Dad.
This magnet has a red side and a white side. And if I just hold it and dangle it, what direction will the red side face? What do you think?
So will it line up like a compass so it'll point north? If I tell you it will face north, then what direction will you expect it to face? So relative to us, north should be that way-ish.
And give it just a minute to stop rotating. But it does. It lines up facing north, which is this way. A little more that way. At any rate, I don't know.
The string might have more influence than magnets. I'm not sure. The red part is facing north.
So sunrise is in the east, sets in the west. That's where the sun sets. He's like, okay, maybe you convinced me.
A compass is more reliable. than a string with a magnet. So if you're ever lost in the woods and you have a choice between a string on a magnet and a needle that you put in water, go with the needle in water that's floating because that will be more accurate. But the principle for both of these simple demonstrations is the same.
Our magnetic field that the planet is creating has a direction to it. And anything that is magnetized, if it is truly free floating and can move however it wants, it will try to line up with the magnetic field. Will you talk one more time?
So the thing that's creating the magnetic field is the spinning of the outer core. So it's the liquid outer core. The liquid outer core is spinning. And actually, the inner core is slowly growing bigger over time. It's freezing.
It's as hot as the sun. But when we say it's freezing, we don't really mean like it's cooling down into, you know, what we would think is cold. But it's changing from liquid to solid. And at that boundary between the inner core and the outer core. When you have new iron crystals form and it's slowly getting bigger, they kick off other elements and say, get out of here.
And those other elements traveling through the inner core create a lot of heat. There's also radioactivity down in the center of the planet too. You have uranium and thorium decaying, creating heat.
It's a very hostile place. If anyone ever asked me, if they said, hey, we've built this crazy, cool, high-tech machine to go to the center of the earth, do you want to go? I would say no.
I don't care how strong you think your machine is. I'm terrified of pressures and temperatures that intense plus radioactivity. I would rather stay on the surface.
Thank you very much. Okay. Now, a compass will line up with the magnetic pole, but so will lava. And when I say lava, I mean the crystals, the iron crystals, tiny little pieces of iron inside lava. When lava is liquid and it comes out of a volcano or it oozes into the ground, you have certain little pieces of iron that will line up with the pole.
And every several hundred thousand years or so, North and South Pole switch places. Whoa. So the North Pole switches around and is where the South Pole is now.
And this has happened hundreds of times in Earth's history. So is that what we're seeing along the side? This is a timeline?
This is a timeline from present at the top down to when the dinosaurs were roaming the Earth at the bottom. And looking at rocks and studying rocks, we can see that every so often North and South Poles switch places. And this is a mystery right now in science.
They call it the magnetic pole reversal, and we are not sure why it happens. We don't know how long it takes, and we're not sure when it's happening, what will happen to the magnetic field. Here's one possibility with a simulation that NASA did where they think that during the reversal, you'd actually have multiple north and south poles.
Navigations would go crazy as we were figuring this out, and we don't even know how long it takes. Some scientists think that some reversals have been really short and happened just within a year or two. Others think that they were long and took 10,000 years to happen.
There's a lot we don't know about this. It's a cool and crazy phenomenon. It seems like it would be pretty dangerous because the magnetic field is protecting the Earth. We don't think the magnetic field would disappear completely while it was reversing, but it could definitely be a problem.
All right. I noticed something weird here. Big black region.
So black is the orientation that we're currently in? Yes. Black is when the North Pole is at our current North Pole.
White is when the North Pole moves around and is at the South Pole. So there was this big region of time? Where it didn't change at all for a really long time.
And then in recent history, it's, you know, every 500,000 years or so, it's flipping back and forth. So if you search magnetic pole reversal, you'll see a lot of articles saying, oh, it could happen anytime. But really, we have no idea.
If we're entering one of these periods, then it's not going to happen for a long time. Well, I know a cool fact about the North Pole. It turns out there's not just one North Pole.
We have two different ways of kind of measuring North, and they don't necessarily align. So typically we think of geographic North. So the Earth is spinning. If we were to stick a stick through the center of the Earth and the ball rotating around that stick. So that's our geographic.
North Pole and South Pole, but the magnetic North Pole is different. So it's different and even moving, right? It does move.
Maybe not a ton or not really fast, but over time it's just moving places. So it's close to the actual North Pole, right? It is close to the actual North Pole, but in the past, just the past 50 years even, we've seen the magnetic pole wobble around a little bit.
It moves around. It doesn't stay in the exact same place. It's really weird to think of. Pulled still, but your compass is moving.
Now let's talk a little bit about plate tectonics. And maybe real quick, let's head to our notes on page 62 again and just review those layers again real quick. So in the center of the earth, we have a solid inner core.
We have a liquid outer core. And the spinning motion of that liquid outer core creates an incredibly strong magnetic field that encircles the entire planet. And then we have the mantle. And the mantle is moving very slowly.
Hot pots, hot spots near the core rise up and get to the crust and they cool and then descend back down. And the whole entire thing can do this cycle, just like a hot water heated up will turn over in a bowl of water. Same thing can happen with our mantle, but it takes hundreds of thousands of years. The crust that is on top can move because the mantle is moving. That causes pieces of the crust to move as well.
And we have several different types of boundaries that happen when different pieces of crust push against each other. So they can come together. We call that converging or convergent plates.
They can pull apart. We call that diverging. Or they can slide past each other. We call that transforming.
So Math Dad. with Oreos just for fun. If I have an Oreo and I have two pieces of the Oreo that are sliding apart, what type of plate boundary is that?
Delicious. It would be delicious if you were to eat it. It's divergent because they're going apart.
It is. It's divergent. What if I have two boundaries, two plate boundaries, where one of them is coming over the top of the other one? And I know this is hard to see.
That's convergent. That's convergent. And how about if I have two that are sliding past each other? Transversal, would you call that? Transform.
Transform. So a quick example. One of the most famous transform faults is the San Andreas fault in California. And what do we have associated with the San Andreas fault? Earthquakes.
Yes. From time to time, there are earthquakes. Because as those two plates are pushing against each other, there's a lot of friction.
They kind of get stuck for a while, but the motion is still there. And then when they move all of a sudden, that creates an earthquake. The chat's telling me I should eat some Oreos. No Oreos yet, Math Dad. After class.
Okay, I'll be patient. And then for convergent boundaries, we have two different types. Let's take a look real quick in the notes.
If you have a thin ocean plate meeting a thick continental plate, the ocean plate will dive underneath the continental plate. And then pieces of it might start to melt a little bit and you'll get volcanoes. And a great example of this is the Cascades. So from Vancouver Island all the way down to California, we have a subduction zone.
That means one continental plate, or I mean, sorry, one oceanic plate is going underneath another plate. And Mount Rainier, Mount St. Helens, Mount Hood, all of those volcanoes, some of them not active, some of them active, are formed by that subduction zone. But if, and with... the Indian plate and the Eurasian plate, when they collide, they're both continental plates. Ah, so they're not going to go underneath each other?
Yeah, so they're not going to go like this. They're just going to push together, and they're creating really high mountains, the highest mountains in the world, the Himalayas. Yeah. Okay, that is really cool, and you've got me so hungry. Science Mom, I can only think about Oreos now.
Well. Before we get to Oreos, I want to talk about tectonic plates for just a tiny little bit longer. Mimi in the chat, pay attention and you'll get a treat.
Let's pull up the slideshow again. And I want to talk real quick about these plate tectonics because... Well, just a sec.
Before you get into that, we said that there were three layers. What's the difference or the relationship between the crust and these tectonic plates? So the pieces of the crust...
Are the plates. Are the plates. They are the tectonic plates, but it's not just the crust.
It's actually a little bit of a layer of mantle underneath it too. They're kind of stuck together and we call that the tectonic plate. Gotcha.
Now it's hard to appreciate just how big these are unless you look at a view of the world from like a, from a spherical view. So the Pacific plate is almost as big as like half of the world. If you're looking at it from this point of view, it's enormous. North American plate is another plate that is incredibly large, the Eurasian plate and the Antarctic plate, but there are several others. We have them listed all here in the notes.
Hopefully, you will color them on your own to learn them a little bit better. That Pacific plate, is that the one that's in light blue there? Light blue.
That's the one with the ring of fire around it, is that right? This is the one with the ring of fire around it. But here we have this boundary between the Himalayan plate and this big Eurasian plate.
This is where the Himalayas form. And if you think to yourself, okay, what are the biggest mountains in the world? They're going to all be along plate boundaries.
The Himalayas, the Andes, the Cascades, the Sierra Nevadas, the Rockies are kind of an outlier. But most mountain ranges, really big ones, happen along plate boundaries. Isn't that kind of cool? Oh, that is cool. All right.
We are ready now for our Where in the World mystery. And then we've got poll questions for you guys. Are you ready, Math Dad? I'm ready. Let's do this.
So this where in the world mystery has to do with Australia. And I'm just going to tell it to you real quick and see if you can. Oh, no. I just gave you a hint, Matt. That was a huge change.
There's only like two cities in Australia. OK, I don't know. Science mom totally messed up the hint, you guys, because I was trying to do too many things at once getting my pictures.
So where in the world do people play rugby, listen to opera, and is there a deadly spider? Is it Australia? What city in Australia do you think? Oh, my goodness. Well, that's all you're going to give me?
Yep, that's all I'm giving you because I spoiled it already with the big hit. So you just have to guess. I'm going to say it's Sydney.
It's either that or Melbourne. I don't know. Sydney is correct. Okay, it is Sydney.
All right. So Sydney, Australia is our answer today's word, the world mystery, which I kind of messed up because I didn't get my pictures uploaded before class. But now you know.
It's the biggest city in Australia. It has just over 5 million people. And?
Now we're ready for poll questions. Is it a picture of the famous opera house? It is. So in the notes, there's a picture of the famous opera house.
If you've ever seen Finding Nemo, you'll also see the same imagery there. P. Sherman, 42 Wallaby Way, Sydney.
That's right. All right. Time for poll questions.
Math Dad likes to try and see if he can stump the kids in the chat, and the undefeatable science kids always win. Whatever. Before I go grab Science Puppy, I want to wish a very happy birthday to Clara, who turns six tomorrow.
Happy birthday, Clara. And to Evie, who turns 10 this Friday. Happy birthday, Evie. Hey, happy birthday indeed.
All right, you've gone to itempool.com slash science mom slash live. Our first question is, the mantle is mostly solid, mostly liquid, mostly gaseous, or only a legend? Were they paying attention today?
That is the question. We definitely covered this. I think it's really amazing that we're able to answer so many questions about the Earth, because it's just down there below where you'd think we'd be able to measure it. You'd think, yeah, we could come up with theories, but there's no way to test it.
But sure enough, we really understand it well. All right, revealing the answer. Chas says, mostly solid.
It is. It is a plastic solid. But one of the biggest misconceptions people have about the mantle is that it's liquid.
It is not liquid. No. Yeah.
I knew that. Oh, I never would have thought it was liquid. All right. Question two. 84% of Earth's volume is the core, the mantle, the crust, or marmosets.
One of those. Ooh, which accounts for most of the Earth's volume? And so volume you can think of as the amount of space something takes up, whereas mass is something different.
That's the amount of material in something, which usually corresponds to how much it weighs. So we get a different answer if we were asking about Earth's mass. All right. And polls are in. The mantle.
The mantle. Good job. That's right.
We said the mantle was like five of planet Mars. Yeah. And the core was one. And then the crust is the thinnest of all, smallest.
Nicely done. Question three. The ring of fire borders which tectonic plate? Is it the Arabian plate, the Antarctic plate, North American plate, or Pacific plate? SC has a good question.
Is the core the inner core or the outer core? And the answer is both. So when we first both the inner core and the outer core are called the core, but we distinguish we have different names for them because one is solid and one is liquid. But I wonder if that naming convention came later because it would almost make sense to just give them totally different names.
It would. But I think it was partly because of the shadow. They saw with earthquakes, and so they could measure the outer core, how big it was, and they said, okay, so we have a core in our planet. But then with better tools and better equipment, then we discovered, ah, one part of this is solid, one part's liquid. All right, let's finish and reveal.
All right. And Pacific plate, option D. Is correct.
Nicely done. Good job. Question four. How do scientists know that the... Outer core is liquid.
Thank you, Science Mom. Got to shout out to Afton, who has a birthday as well. Happy birthday, Afton. Happy birthday. Ooh, good question from Neptune36.
What's the right way to say it? Plate tectonics or tectonic plates? And it all depends on if you're talking about a specific plate.
So then it would be a tectonic plate, like the plate that Australia is on. So the plates that the... crust is made of are called tectonic plates. But the theory or the idea of there being plates that slide around and move around on a planet, that idea is called plate tectonics.
So it depends on what you're saying. Both are correct. Makes sense.
And the answer is the earthquakes, the waves pass differently through the core. And that's how we were able to tell the difference. That is right.
So you can't hear a splashing sound using sonar. And. What about drilling down? Can we drill all the way down?
No, most likely we'll be able to drill through the crust to the mantle. There's some research projects doing that. It's very expensive, but it's probably possible.
Still hasn't happened. It hasn't happened. It's probably possible. But drilling all the way to the core?
Not possible. Nope. Nope-a-dee-nope-nope.
All right. And our last question for today. Why are the Himalayas getting higher each year?
Is it because gravity pulls less on tall things? Is it that the Himalayas are on a divergent plate boundary? The Himalayas are on a convergent plate boundary? Or actually, the Himalayas are getting shorter each year? This is the one, Science Mom.
I don't think you're going to stump them, Math Dad, but I think Julia has a question that might stump you. How many times does Mars go around the sun compared to Earth? Do you remember? We talked about this yesterday on Monday. Mars takes almost two years, two Earth years to go around.
Ooh, didn't stump him. Oh, take that, Julia. And Noah has a great question.
Why did Mars's core cool down and then stop spinning? We don't really know. Well, it's a smaller planet.
It is a smaller planet, so it just didn't have as much heat as Earth did to begin with. So that's one idea. But yeah, for both Mars and Mercury, there's some interesting research that we could do if we can get more probes on the planets and do some more studies about how they cooled down and why.
It would be interesting to know. Oh, they got it right. Okay.
So the Himalayas are on a convergent plate boundary. Nicely done, you guys. Good job. Converging, coming together, and that was pushing the whole mountain range to get taller and taller. It was creating the mountain range.
Yes. That's how the Himalayas were created. Very nice. So I'm sure it's a very slow growth. Not so much a fast growth.
No, it took... a long time for the Himalayan mountains to form and other areas where you have mountains growing as well. It's a slow, slow scale. How fast are continents moving?
So continents move about as fast as your fingernails grow, actually. Well, that's really slow. It is.
It is slow. If you're watching your fingernails, you're not going to see them growing. But over time, over several weeks, there's a noticeable difference. It's very small though.
And so with a continent, it's something that is so big for it to move just a few inches a year. That might seem like it's not going to make a difference at all. But in Australia, the fastest moving continent, they actually have to update, do big updates to GPS systems fairly regularly. Because in about five or six years, all of a sudden things will be a few feet off because it's moving so quickly.
So Isaac's reminding us, victory dance. There's no escape, Math Dad. All right. All right. So what victory dance are you going to do?
I don't know. I don't have many dance moves. All right.
Oh. We will be seeing you again on Friday with our next art project. And we're going to showcase some of the great pictures that have been sent in for the bridge construction too.
So if you found some cool results with either your bridge science project or with your mason jar science project with growing the two different mason jars, send them to us. We'll have a little showcase on Friday. And we actually will be spending class time on the art project itself. Sometimes with our projects, we can just tell you what to do.
And then you. do it outside of class. But if you want to draw with us on Friday, you definitely can.
Yeah. So what do they need? Pencil and paper? Pencil and paper and something to color with.
That's it. Is there a template to print out or anything? There is.
And we'll send a link before Friday. All right. Sounds good. All right.
Work hard, grow smart, and we'll see you on Friday.