Daniel and Jorge Explain the UniverseWhat would happen if you jumped into a hole that went through the center of the Earth and out the other side?
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Hey Daniel, what's your favorite part of a pizza?
Oh? I'm all about the crust. The crust makes the pizza.
Your crust guy? Huh, Well, it turned out that's just like a planet. All the interesting stuff in a planet like ours happens on the crust. That's where the good stuff is, right.
You know that totally makes sense because I can't count the number of times I've burnt my tongue on the hot lava of tomato sauce on pizza.
It's like a molten core all that.
Cheese exactly exactly, and you always want to bite it before it's cooled off and turned into a nice place to live. You know, you're always got to get in there. But you know, you're right. The crust is very important, and you know that's where you hold the pizza. That's where we hold onto our planet. So it's it's a big deal.
Yeah, what about what about the cheese stuff crust? It's like a crust in a crust.
Yeah, what is the what is the geological analogy of cheese stuff crust? Right? That's like underwater, that's like a sub subterranean lakes or something of cheese.
Yeah, well, I'm like those intolerant So.
Hi, I'm Orge and I'm Daniel.
Welcome to our podcast, Pizzas in the Universe.
Daniel and Jorge explain what makes a pizza a pizza.
And what doesn't make a pizza. We have no idea.
We do have some idea based on my deep expertise of being a particle physicist. I'm here to expound on what's a pizza and what's not a pizza?
Now, Welcome to our podcast Daniel and Jorge Explain the Universe, a production of iHeartRadio in.
Which we find topics here, there, everywhere and break them down so that you can understand them while you enjoy your pizza.
That's right. We're also the authors of the book We Have No Idea, which you can find in bookstores and online.
Or just borrow from your grandma because she read it and she loved it.
She loved it. She told us.
Are you in touch with everybody's grandma?
Hey, I'm in touch with the cosmic grandma, like the you know, like the idea.
I'm imagining all of a sudden, imagining some like you know, underground Internet Grandma network that you've typed into.
It's just a giant book club.
Basically, can you mobilize them in emergencies to do something important?
Oh? Yes, there's I have a big red button here.
It says raise Grandma army.
Yeah, somebody's hungry quick, somebody hasn't had.
Lunch, somebody's looking thin. Cook cook.
But now today we're going to not talk about something that's out there in the universe and mystery. But today we're going to focus on a question very near us and actually underneath you.
That's right. Today we're going to talk about where we all live, the place that you call home.
Today's topic is what's inside the Earth or what is the Earth made out of? We live on it, we walk on it, we run in it, we swim in it. But how many people know what this giant ball that we're riding around space on is made out of.
Yeah, it's a special place. I mean, as far as we know so far, it's host to all life that we've ever seen. Right, everything anybody has ever touched or tasted has been on Earth. So it's an important place.
You know.
It's the spaceship we are riding through the universe on. And there's a lot going on, right, you can't just ignore it, especially for those of us living in California. You know, we're wondering about like earthquakes and all sorts of crazy stuff, So it's important to know what's going on inside the Earth.
Yeah, magnetic fields and having them move around and shielding us from cosmic rays it's all because of what's going on inside.
Mm hmmm, you know, continental drift and super volcanoes and all sorts of stuff. If the Earth was just a quiet lump of rock, it wouldn't be quite so exciting to live on. Yeah.
And lava, of course, lava.
Who doesn't love a lava?
Who doesn't love a lava lamp?
You know, I was teaching ones and I usually like to open my class with asking people for random questions, you know, get them warmed up. Hey, he's got a totally random question, right, And somebody once asked me, what does lava taste like? That is a good random question.
I said pain, Pure pain tastes like pain, tastes like charred tongue.
No, I said pineapples. It tastes like pineapples?
Does it? Was that with authority?
I have no idea what lava tastes like. No, in like the bill a second between lava like scorching your tongue. It probably you It just tastes like a rock, right, It's just probably like licking a rock. Salty, salty, exactly metallic. Yeah, So people out there, do not do this investigation, Do not approach lava, Do not play with lava. Do not lick lava. I probably doesn't taste like pineapple maybe in Hawaii.
Actually, And so we got into this question a little bit, Daniel, because we were wondering, we were thinking about ideas with this for an episode, and we were wondering, what would happen if you dug a hole through the entire Earth and jumped into it? Right, that's a that's a pretty weird question.
Yeah, And you know, this is the kind of thing you see in science fiction all the time, you know, journey to the center of the Earth. And I was watching gravity falls and they have the bottomless pit, you know, they jump in and fall forever. And so it's a trope that you see a lot of times. You know, people wonder like can you get into the center of the Earth, And so it's fun. It's also a fun physics question I asked in my freshman physics class sometimes, like what would happen if you drill the hole all the way through the Earth and then jumped inside, you know, from the point of view of like gravitation.
Yeah, but you know, I'm an engineer, so I kind of got hung up on the question of how you even make that hole or could you have a tunnel that goes through the center of the earth, And which led us to the question what is inside the earth? What's going on? What would you drill a hole through?
Yeah?
Exactly? Is it hard or easy? Do you have to like dig down one hundred meters and then you know it's just like a big pile of soft stuff or is it like diamond down there, or you know, is impossible to dig into? Yeah, this is pretty interesting stuff.
Yeah, so we might get to that question of what would happen if you jumped through a hole that goes through the entire earth? But today's episode we'll talk about the earlier question, which is what is the earth made out of?
That's right, we'll take you on a tour from the very top all the way to the very center of the earth.
Yeah, And as usual, we were wondering how many of you out there know the answer to this question? How many people know what inside the earth? And so Daniel went out there as usual, out into the street and as people, random strangers what they thought was inside the earth.
Here's what people had to say, Is the Earth just one big rock? Or is it more complex? Under our feet?
There are more complex features below our feet.
All right, so like the mantle, core crusso metal sphere, messal sphere or something like that.
Oh, you know a lot.
No, I know there's it's not just a big rock, but yeah, I don't know the components of what's inside there.
Well, I think there's like different layers of rocks.
But that's it, Okay, like different but just different layers and different just different components to make of the earth.
It's not just one big.
Rock, Okay, it's like layers and like there's like dirt, rock, gravel, like all that stuff.
And they're like.
For some reason, like my mind went to like minecraft.
So then like.
It's like there's there should be like lava and areeah, a.
Crust is like made out of like different minerals, like different rocks, and.
Well around the earth the first layers the crust. Then there's soft, softer, more hot rock, and there are two layers of magma at the center of the core of the earth.
Well, it sounds like most people just sort of guess that they just made out of rock and dirt and some lava.
Yeah, a lot of people know there's like rock and dirt and gravel. And I love the people who refer to Minecraft as their their reference. But you know, there's there's some evidence there, Like, you know, Minecraft is a little bit educational. You dig down deep enough in Minecraft and you get to Magma, So yeah, good job Minecraft.
Yeah, and zombies, And that's all that's all I know about Minecraft is there are zombies.
Also. Minecraft, you know, says that the universe is pixelated, and I'm pretty sure they get that right. Also, so you know, the physics of Minecraft is really pretty.
Solid, interesting, just maybe a few orders of magnitude exactly.
They need a few more bits, you know, it's not an eight bit universe we live in.
Well, there's the idea that we maybe we are all in a video game, right.
That's true. Yeah, we could certainly be in a simulation. My kids watched Ready Player one last week and they looked at it and they were like, whoa, that's pretty cool. He can almost live inside that game. And then you could see the idea being formed in their minds. Wait, what if we're inside the.
Game right now? Really? Whoa?
And they weren't even stoned. I promise they weren't even stone They came up with that question totally.
Oh well, that's a that's a topic of a podcast we already recorded, is are we living in a video game? But today's we're going to focus on what's in what's in the earth. So take us through, Daniel. If we start where we are now sitting or standing or writing on and we go down, what do we hit first?
Well, the thing to remember is that the Earth is huge, right, So it seems like almost flat because the curvature is so small. That's just because the Earth is enormous, right, And so remember as we take our tour down to the center of the Earth, the scale of things from us all the way down to the center is thousands of kilometers, right. So that amazes me already when I learned that the crust, this part that we stand on, you know, the part that's like rock and whatever, that's only like fifty kilometers thick, and it varies under the ocean, it's even thinner in the top of a mount Everest, of course it's thicker. But it's like a tiny little shell. It's like an eggshell around a yolk. And that's the part that we live on.
Wait, what do you mean, so the first layer underneath our feet is called the crust. Is that this is the official physics name. The crust.
That's the official physics slash pizza name. Yeah, it's the crust. It's where you grab onto the planet from. You know, what could you have instead of a crust, Well, if you were like on Jupiter, for example, Jupiter doesn't have a crust. It has like a metallic hydrogen core and then like helium rain and then like you know, liquid hydrogen oceans, and you know, there's no like firm place you can really land. There's no rock on Jupiter. Oh, we're pretty lucky to be a rocky planet that has some crust to it.
Yeah, Jupiter is just kind of like a big blob of wet stuff.
It's like a sun that never took off right. And and you know, earlier in Earth, in the life of Earth, when it was really really young, it was just basically a ball of magma, and so the surface was all you know, hot molten rock. There was no cold crust to walk on. Wait to Earth and so the Earth yeah, very very early on.
Oh, we form from but I thought we formed from like bits of stuff out there in space. How did it turn into a big ball of lava?
Yeah, so we did form from big from bits of stuff. Right, Let's rewind a few billion years, and you have like a huge cloud of gas and dust, right and rubble, and that's all left over from other stars that have that you know, had you know, billions of years to burn and then explode and spew their stuff into space, and gravity gradually gathers it back together. And then gravity made the Sun and it gathered all the extra bits together into the planets. And the gravitational pressure, right, the collision between the stuff and the pressure pulling this stuff together, that's what creates a lot of the heat. Also, there's when you have a really hot stuff inside the Earth and you have things like uranium and all sorts of other stuff emitting radiation, so it makes the Earth hot. Right. The gravitational pressure and the radiation from the core made the young Earth very very nasty and hot and wet, so no place you can go for a nice walk.
It's being squeezed down into it. But okay, so the first layer is this thing you call the crust, and it's made out of just like rocks, like the same rocks we see on the surface.
Yeah, I mean it is the surface, right, and it goes down about you know, thirty five kilometers, fifty kilometers depends on exactly where you are. And people have tried I love this. People have tried to dig through the crust right to see like how far could we go? How deep could we dig? You know? And the Russians actually have won that race back when there was a Soviet Union. They dug a shaft which was I think twelve kilometers down. So it's like, you know, maybe a third or a fourth of the way through the crust.
The idea, it was almost like a pin prick. They didn't really get through the crust.
Yeah, and you know, all of these things, these little holes we're talking about the size of the crust, even like the peak of Mount Everest, all these things are tiny features compared to the size of the Earth. As you're saying, it's like a pin prick. And remember, if you held the Earth in your hand, none of the features on the Earth would even be recognizable. They might not even be observable. You could probably run your thumb over the Earth and not even tell where Mount Everest was.
Wow, it would be like a it would look shiny, like a shiny marble.
Yeah, shiny, slightly wet marble exactly, so, and the outer layer is this crust which is only you know, thirty to fifty kilometers thick, So it's really pretty then.
So we would see like just regular dirt and rocks and stuff for fifty kilometers. That's a lot. I mean, that's like.
From yeah, I know. And it's this conflict in scales, right, Like fifty kilometers seems like a lot, and we try to dig through it and it's too far, right, and so on one hand, it feels like a lot. On the other hand, it's a tiny, little fraction. But this is the kind of thing you discover when you are exploring physics and space and the universe, right, all these conflict and scales, Like the Earth is huge, but actually it's tiny compared to the Sun, which is huge, which is actually tiny compared to the galaxy. Right, some of the things I love about physics.
Yeah, and it meanly like you can drive fifty kilometers in your car in less than an hour, but if you try to dig fifty kilometers down it would take you a little bit longer.
Yeah, I don't even know how they did it. This hole that they dug in the Soviet Union, that's twelve kilometers deep. It's only like twenty something centimeters wide, right, so they have to have like a crazy drill bit. And you know, they probably had.
Really long extension cord, like a twelve k extension cord, you know what I mean.
Probably they had like Christmas lights and everything. They were using every extension cord in the Probably.
They were in the Soviet Union. That's why they went broke. They're like, everybody, don't use any electronics, give us your cord.
And Russia hold rills you. I don't even know what that means. Yeah, exactly.
So.
Yeah, so the crust is fifty kilometers thick. We've only barely pricked the like the outer bits of it, right, the deepest mines hardly scratch the surface. And it's a tiny fraction of the size of the Earth.
Wow, it's just like a little X eggshell.
Really mm hmmmm exactly. It's like if you ordered a pizza and the crust was like almost invisible, like you could just barely grab it before you got the tomato sauce.
Right, Oh, it'd be like a I hate it when they cut pieces and squares because then you get pieces without crust.
You hate that that's the best way to cut pizza. What are you talking about.
No, then you don't get any crust. I thought you were a crustman.
Oh yeah, but you have crust on the bottom. I mean that's what the crust is for to hold up the pizza. The part of the crust without tomato and cheese is wasted to dry.
I thought, okay, well that'll be another episode Daniel horri argue.
But pizza.
Okay. So let's say you dig through fifty kilometers down and you break through the crust. What do you what do you find?
Then you get to something they call the mantle, and the mantle is basically rocks that are being squeezed really hard, you know, by the gravitational pressure by the crust on top of it, and they're like not fluid, but not exactly solid. It's like a bunch of rocks that are rubbed together really hard, and and they can slide around a little bit.
Wait, what do you mean fluid? They're like like grain, So sand is fluid or like really the rocks themselves to form and flow.
I think it's a little bit of both. I think it's a little bit like the way glaciers flow right. You hear about glaciers like flowing across the surface of the earth and carving out mountains, right, But then you go visit a glacier and it's just a big piece of ice and you're like, how is this thing flowing? Right? Well, it flows very slowly, you know, like like glass flows or something like that.
See, if you went up to it and touched it, it would look feel solid, but over time it would be deforming mm hm.
And you know, I think there's elements of it that are more liquid and elements elements of it that are more solid. Right. That's why we have magma that creeps up through holes in the crust and turns into lava when it spews out in volcanoes. By the way, huge internet debate over whether what to call magma and what to call lava?
Is there? Really that's what you mean? People are you? You mean? People are you in the internet over things that are not that important?
Someone on the Internet was wrong. I can't go to sleep. It's magma when it's still underground, and as soon as it comes above ground then you call it lava. So if you say that a volcano spews out magma, you're gonna go like a thousand pe people online telling you you're wrong, that's actually lava, or you say that the lava underground.
Yeah, well, let's be sure here to not anger anyone on the internet.
That's not the point of this podcast is to annoy people and piss them off.
So the dismantle, this kind of liquid rock is super thick, you were telling me earlier.
Yeah, it's like almost three thousand kilometers thick. So it's a huge chunk of the earth. Right, It's much much thicker than the crust. So if you were to somehow be able to dig all the way through the crust, right, which seems almost impossible, you'd get to the mantle, and the mantle is like, is really thick. So that's a huge part of the drilling. If you wanted to get down to the center of the earth.
You'd be like drilling from Florida to California.
Yeah, but it'd be super hot and super high pressure the whole time. Right, So it's not just like a nice drive across country, right, it's really difficult environment.
You need a lot of extension core for your air conditioning.
Right, And it's because the mantle is not actually solid that we have earthquakes and tectonic activities and mountains and stuff like that.
Oh, it's always shifting and moving mm hmmm.
Yeah. You can sort of think of the crust as broken into pieces that are floating in slow motion on top of this, you know, semi liquid, semi solid mantle magma business.
Right.
Oh, they slide around and bang into each other, and all the interesting stuff that happens on the surface is because of that action.
I see, because you're saying it's like the crust is pretty solid, so we are kind of like floating icebergs kind of right, So that the crust is solid, but the rocks underneath is fluid. And so when you move these like solid pieces, that's when you get the crunching and the earthquakes.
And it's pretty thick, which is good because you wouldn't want to drive, you know, an entire tectonic plate through something like you know, as thin as water, and things get pretty crazy. This mantle is really thick. It's like ten to the ten times thicker than tar, right, not something that you can easily sluice through.
Like denser.
Yeah, they have some measure of thickness, you know. The viscosity. Basically, it's more viscous than tar by factor of ten to the ten.
Oh, I see, I see viscous. Okay, it's not.
If you had a bowl of it. How long would it take a drop to form and drop out? Actually, that's fascinating. Have you seen this experiment, the tar pitch experiment.
Yeah, yeah, it's like something so thick it just hangs there for a long time.
Yeah. It takes like, you know, two decades for a drop to form and fall. And they've been doing the experiment for like, I don't know, eighty years or something, and in eighty years they had like four drops fall, and every time one is about to fall, everybody's like super excited about it. Anyway, this stuff is much thicker. We take billions of years for a single drop to form.
Oh so, let's say so if we're digging our tunnel through the center of the earth, we would dig a tunnel and we'll be safe. We wouldn't move, would it, like with the tunnel close in on itself or something.
Well, there's a lot a lot of pressure, right, Yeah, it's really thick. You're right, so it might hold itself up. But there's also a huge amount of pressure. Right, there's tons and tons and tons of stuff bearing down, So I think that that tunnel would have to be really strong to survive. And that's my bone with like all those movies about journey to the Center of the Earth, I'm like, where's all the stuff? You know? It always seems to be like fluffy empty space, like they're just like digging through styrofoam peanuts or something.
But in reality, if you dug a truck tunnel, like the walls would cave in really quickly because it's unders so much pressure.
Right, Yeah, you need some super material to stabilize the walls. Yeah, adam antium probably.
All right, let's keep digging down, but first let's take a quick break.
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All right, so we're digging through to the center of the Earth, and we passed the crust and we passed the mantle. We're now about three thousand kilometers into the earth, and then we things change right after the mantle. Now we hit a new layer, which is called the liquid outer core.
Yeah, exactly. And you might wonder, like, why do they give these things different names? Is the Earth really just continuous? And this is just like scientists putting labels on stuff, because scientists love putting labels on stuff.
Oh, like, is there a boundary? Really? Like it does? Do things suddenly change when you keep digging?
They kind of do? Yeah, there really are surface is there? Right? Like things do change. The mantle really is different from the crust, and the crust and the mantle is really also different from this from this core, both the liquid outer core and then the solid inner core. There really is a change there, which is fascinating. Right, Why isn't it continuous? Why isn't it smooth? Why are there these edges? But there are? And so you get to this place where it's like liquid rock, you know, it's like molten metal and rock it's like incredible.
Because it's so hot and un there's so much pressure that basically all the rocks melt, right and you get lava.
Yeah, that's right. And remember magma, I mean magma, magma, magma. Dude, there's no lava that and so really hot and really dense, and so you got this liquid metal and all sorts of rock and other stuff mixing around in there.
Right, it's like super duper dense.
Right. Yeah, it's ten thousand kilograms per cubic meter percuber.
Oh, I see ten thousand, So it's like five tons or so in a in a suitcase size.
Yeah, well you have a ubic meter size suitcase.
Wow.
I really don't want to travel with you, man, I just it's only a cubic meter. I think you could probably fit your whole family into a cubic meter. Man. No, yes, definitely. That cubic meter is a lot. Anyway, it's pretty dense down there, it's pretty hot, it's pretty nasty, but that's important. Right. If it wasn't liquid down there, then you couldn't get all sorts of interesting stuff happening, like magnetic fields.
Oh, that this is where the magnetic field comes from. It's this liquid molten core, but it's really a layer, right, because we're still not down to the core.
That's right. This is the liquid outer core. And we don't really understand that there's a magnetic field very well. And for those of you interested in that, we have a whole awesome podcast episode just about the magnetic field. But a critical thing for having a magnetic field is having a conducting fluid, so a fluid that can conduct electricity and move around. And so we think that like currents in this inner bits, inner liquid bit to the Earth are what provides the basically the motion for the magnetic field of the Earth.
Oh, it acts like a giant, like a giant solenoid kind of right, like a giant.
It's like a like a giant electromagnet. You know, there's currents and they're spinning and that generates a magnetic field, which causes more currents, which causes more spinning, which causes more magnetic fields called the dynamo. It's pretty cool.
Wow, it's like a it's like we do have it. It's like we have an engine in the middle of the Earth.
Yeah, we do exactly, and it's a geological sized engine, right, I mean building something that big would be incredible. Right. This is these are structures that are powered and that are operating and are bigger than anything humans have ever constructed. Right, so we should definitely be in all of them. Wow.
Okay, and then if we if you make it through and it's and again it's just like rock. But what does that mean? Rock like a iron or metal like everything is just kind of mixed in there.
So it's mostly iron, and there's a bunch of magnesium mixed in there also, and then there's you just some rocks which you know, silicate rocks and this kind of stuff. And remember where all this comes from. Right, where does all this iron come from? It comes from the heart of a burning star? Right, All of this was created in fusion inside a star somewhere else billions of years ago, which was then flung through space and gathered back together. You know, the Earth doesn't make any of these metals. There's no fusion happening here. So everything that the Earth is made out of, that you and me are made out of, had to be formed somewhere else and then exploded through space.
Wow, there was an event sometime ago that created a whole earth full of these metals.
Yeah, exactly, and yeah, huge quantities. Right, It's not like you got too a spoonful of iron here, like you have enormous amounts. And it's it's not also a coincidence that it's iron, it's not random. Iron is the point where fusion stops being energetically favorable. Right. It's the point in a star where squeezing things together to make something heavier stops releasing energy and then costs energy to make things heavier. So iron is sort of the natural endpoint for fusion inside stars, which is why you find so much of it.
Right, And so you that's why most rocky planets out there would be made out of iron.
Right. I'm not sure about that, but I think there must be a lot of iron out there and rocky planets.
Yeah.
Okay. So we're now about almost six thousand kilometers into our tunnel to the center of the Earth, and we.
Bring enough snacks you did you pack one cubic meters?
No, No, we're just going for a daniel. We're just going. We're holding our hunger here.
It's like a diet trip. On the weight trip to the center of the Earth.
We're hoping there's a McDonald's down there at the center.
Actually to spoil the surprise, if you do make it to the center of the Earth, your weight does drop to zero.
Oh interesting, interesting teaser. So that we are, we're down, and we we duck through the mantle. We swam through the molten outer core. So here's here's where the tunnel idea would collapse, right, because you couldn't. It's like it's liquid magma down there, right.
Yeah, it's totally liquid metal. So you can't just dig a tunnel, right, It's like digging a tunnel through the ocean. Right, you get something to support it, and that's something would have to be super strong and resistant to heat. So I don't even know what you could make it out of.
You have to be like a diamond diamonds earthship, yeah, something like something like that.
You have to construct a diamond tunnel as you go or something. I mean, this is already implausible, but it sounds possible. But they did it in movies. What do you mean that was in Minecraft? You can dig the cent of the Earth, so obviously.
So so there, let's say you're swimming through this magma for another two thousand kilometers and then then you'll hit You'll hit it like a surface, right if you keep going down to the center.
Yeah, you hit a surface, right, And and what you hit is this solid inner core which is mostly iron and nickel. And it's basically just a huge ball of metal, right, And then you might ask like why is it solid? Right? And it's solid because of all the incredible pressure it's squeezing it down, right, And and it's also it's interesting to me that it's almost the size of the moon. It's like three hours the size of the moon. Is this just like ball of metal in the center of the Earth?
Oh wait, why is it metal? Why isn't it like like at some point of rocks, if you put them under pressure, they'll melt into magma. But at some point, if you keep pressing them, they'll actually solidify.
Yeah, exactly, they'll solidify. And you know the Earth is cooling, right. The Earth was hot and nasty when it was borne, and it's been cooling because space is cold, and eventually it's gonna you know, cool down even more. And so the scent it's cooling sort of from the center out. I guess you could imagine, right, like this center is it's solid and this solid inner core is growing right as the liquid part is sort of falling, the falling to the center, and it's growing by I think like a millimeter or two every year. Wow, So we got time.
We got time before Earth freezes over, is what you're saying exactly exactly.
You've got time to finish that novel you've been working on or whatever before the core of the Earth solidifies.
But it's important because then it's sort of game over for life on Earth, right, because then we wouldn't have a magnetic field.
Yes, we need a magnetic field to survive because without a magnetic field, we wouldn't be protected from space weather and space radiation and stuff like that. But you know, it's going to be a long time before the magnetic field stops because the center of the Earth freezes. But you know, it has happened, like on Mars. We think Mars used to have a magnetic field. We think it used to have all sorts of interesting stuff going on inside, but now it's basically just a dead rock, right, wow, And it doesn't have a magnetic field anymore, and we don't think it has a whole a lot of stuff going on on the inside though you know, we're not one hundred percent sure. Wow, but yeah, that could be the future of the Earth. But you know, by then maybe we will have left the Earth and explore the universe or developed ways to make artificial magnetic fields or something else. Crazy.
All right, So that's that's at the center of the Earth. It's a ball the size of the moon made out of metal, really thick and hot and solid metal. That's it is it? Is it like that all the way to the very center of the Earth.
We think so, yeah, And we think it's just one big ball of metal. And in fact, some people for a while thought that maybe that ball of metal was just one big crystal. Right, you know how metals can form crystals. The'se like regular lattices of atoms that line up, And for a while people thought it might just be like a huge crystal. But now they're not so sure.
They downgraded their diamond rating on the Earth.
That's right, And we had to go change our insurance policy because the new appraiser said it wasn't worth.
As much we have.
Sure, Hey, we like it, we love the Earth. It doesn't matter.
I love you anyway, baby, It's not worth as much, I guess it's.
Worth everything to me. Man, it's our home. Yeah, exactly. So that's at the center of the earth. But remember, you know, we haven't a visit these places. All this stuff we've learned, we've learned sort of indirectly.
Yeah, that's the amazing thing. And so let's get into that. But let's take a quick break.
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All right, so now we're going to get to the question of what happens if you jump through hole down through the middle of the earth. But first, I really want to know how we know all this stuff, Daniel, Like, if we haven't been able to drill down that deep, how do we know what's all the way down to the center of the earth.
It's really an impressive triumph of science, right science. We're desperate to know the answer to a question, and sometimes you can't see directly like you'd love to, right, So you have to look indirectly. You have to look for clues, and we look for ways to figure out what's going on inside. And we have a whole bunch of them, and then we try to make sure they all tell us the same story. And my favorite one is the way we look at the inside of the earth is by looking at the impact from earthquakes. We use earthquakes the way you might like tap on the wall of your house to figure out like is it hollow or is there a stud there? You can tell sort of what's behind the wall by listening to how the sound moves through it.
Oh, I've heard of that. Like, if there's an earthquake that happens in one part of the world, then you check with everybody else around the world to see how that wave propagated.
That's right, because the wave from the earthquake. Right, Earthquakes are these huge events and they cause a shockwave through the earth, and that shockwave travels at different speed different kinds of stuff. Right, So you can build a model and you can say, all, right, well, if the earth was all water, how fast would the shockwave arrive in Hawaii or arrive in Russia? If the worth if the earth was all you know, rock, how how fast would it move? Right?
And they bounce when they when it changes a medium, right, like a wave, some of some of some of your wave will bounce back if it goes from like air to water, or one type of rock to another type of rock, And so that's another way they can they can tell where these transitions between different kinds of earth are.
Yeah, you get all sorts of interesting reflections. Just like when light hits the window. Most of it goes through, but some of it bounces off, Right, You can use a window sometimes like a mirror in the same way as you were saying. Every time a wave goes through a transition a boundary from one kind of material to another, part of it reflects, so they can see these reflections. That's how we know that there really are transitions there. Is that every time there's an earthquake, the wave travels around the mantle, but it also reflects off the mantle interface with the core, and then sometimes it goes even deeper and then it reflects off the inner core. So we can tell that there really are layers there from these reflections, and we can get estimates for their density based on how fast they're moving.
We know that that's what the Earth looks like because if it was made in any other way. If it looked like any other way inside, we would see these waves come out differently.
That's right. It's sort of like a big ultrasound. Right. The way ultrasound works to see like a baby inside the mom without cutting her open obviously, is it sends these tiny little shock waves ultrasound meaning a higher frequency than you can hear into your body, and it listens to how they come back, and based on the speed and etc. It tells where the stuff is and where the stuff isn't. So basically earthquakes are a way to ultrasound the earth.
That's amazing.
Those guys are the only ones who celebrate when it's an earthquake. They're like, yeah, huge earthquake. We get a new picture of the inside of the Earth.
We get to tell the earth as a boy or a girl, Oh my god.
Or neither. Yeah, exactly what the quins?
What?
Yeah? And so that's really that's the primary way we know about it. And to do that you have to build models, right, and so you say, well, maybe the earth, the Earth is this, in which case we would see the reflections looking like that, and then you compare what you predict to what you observe and the tweak and tune, and this tells us a lot about what we know about the inside of the Earth without ever going there.
Wow, that's pretty cool.
Go science, man, science, you are awesome.
Yeah, buy yourself a pizza, a real pizza, not one with pineapples on it.
And you know, we have some direct evidence, like we have dug down pretty far to see what the crust is made out of. And you know, sometimes things do crack open and magma comes out from the earth and turns into lava, and we can sample that and see what it is, right, And we can look at rock outcroppings, you know, places where like the crust has been lifted up so we could see what used to be underneath stuff like that.
Wow. But it's pretty amazing that basically the Earth is not a big ball of rock, right, Like it's this kind of active, moving, squishy, dynamic ball of stuff.
Yeah. Yeah, it's there's a lot of stuff going on, right, It's not just a rock. If it was just a rock, then life on Earth would be very different, maybe impossible, right, without the magnetic field to protect us in our atmosphere. So we should be grateful that there's a huge engine humming under our feet that all this stuff is happening, you know. And I wonder something I was trying to figure out but couldn't is like when we first became aware of this, you know, because as humans, you know, we know we live on the surface, but like a thousand, two thousand years ago, people must have had a very primitive understanding of what the Earth was made out of.
Hm, well, they probably thought what I thought, which is just a giant rock, right.
Yeah, And people, I think, like more than one hundred years ago, were able to make density measurements of the Earth. Right they know the size of the Earth, they know, you know, how big it is, and you can figure out, you know, with the strength of the gravitational force, and from that you can figure out with the mass the Earth is, and that tells you, like what's the average density. So, like more than one hundred years ago, we were able to measure the average density of the Earth and discover that it was more dense on average than it was in the surface, which suggested that like something denser was going on under our feet. But that was really the first clue.
Wow, cool, all right, So that's that's what the Earth is made out of. It's a thin crust on top of a fluid rock, on top of a giant layer of magma two thousand kilometers thick, and then down to a little crystal diamond ball the size of the moon.
Iron nickel, iron, yeah, right, yeah, you can. You can advertise it on the internet it's a crystal diamond, and then you know they'll be disappointed when you send them just an iron nickel ball.
But sure, go ahead, we'll call it like an iPhone. You know, it's a metallic.
Nickel exactly, exactly right.
So okay, let's get down then to what we set out to answer, which is what would happen if you jump down a hole through the earth. Well, we're already stablished it's impossible to dig that hole.
Yeah, So let's imagine it's possible that aliens come and have some super digging technology and some super tunnel technology, and we can actually make that hole all the way through the Earth and out the other side, right through the very center.
And hold it open because you know, the magma wants to flow in, the liquid rock wants to crush it in, and that that core in the middle doesn't really want it's so dense it doesn't want to get drilled through.
Right, Yeah, exactly. So you need a lot of legal paperwork before you can jump into this hole. But let's assume that we figured out all the physics and all the law aspects of it, and that we're ready to jump. Right before we do that, we want to do some science. Okay.
So there's a hole, there's a tunnel going through the center of the Earth out to the other side. Okay, and what happened? What happens if you jump into it?
Yeah, So it's really fascinating because you have to think about the force of gravity. So you're on the surface of the Earth. The whole earth is pulling you towards the center of the earth, right, because the whole earth is a smaller radius than you do. Right, every little bit of it is pulling it. But you can think about you can treat it gravitationally as if it was just like a particle at the center of the Earth that was pulling on you, because it's all under your feet. But once you jump into that hole, then some parts of the Earth are no longer on the inside. Some of them are on the outside. So imagine you're like halfway down this hole.
Like, let's say you're a kilometer down falling eating your snack. Now there's a whole bunch of earth, the Earth above you, that's now pulling you back.
Right. Actually, the earth above you, on average doesn't have any effect on you. The stuff that's just above you, yeah, that's pulling on you. But there's like this kilometer thick shell of earth, right, and the stuff that's on the other side is pulling on you, and the stuff that's above you is pulling on you. All cancels out. So if you're inside a shell, then all the gravitational forces cancel out. What yeah, yeah, I mean, imagine, for example, what happens when you get to the center, right, What happens when you get to the center. Is there any gravity there?
No, because at every point, every little bit of the Earth is pulling you equally in all.
Directions, exactly. And that's true for any shell that you're on the inside of. So if you're halfway down the Earth, then you only feel the gravitational force of the part of the Earth that's closer to the center than you are, right, a sphere of that radius. The stuff that's above you, you don't.
Feel like, let's say we're digging the tunnel, and we only get halfway there, and we stop and we stand there on the bottom of that hole. You're saying, I would weigh half as much like I could jump. It would feel like were standing on the Moon. As you're digging down, you would you would start to feel weightless.
Yes, exactly. So as you so you jump into this hole. Right just before you jump, you're feeling the full grave vitational force of the Earth. And as you go down, the gravitational force starts to go down, and it goes down linearly, so that when you get to zero, when you get to the center, there's no force on you anymore, Which makes sense as you were saying, because you're pulled in every direction.
Wow. So if you open, like if you drill through, you're falling through and you get to the center, you would be floating around in space just like Earth.
No, because you'd have you'd have a huge velocity, right, have been pulled down from a bunch of stuff, so you have a huge amount of velocity, and you'd shoot right through the center. Right the center would be your highest speed. It's like on a roller coaster. You start at the top right and it rolls you down a hill. When the bottom of the hill right then you're going really really fast.
If there's no friction, you would just keep going, yeah, because you've been falling all this time exactly.
Unless it's like a party down there and people hanging out and ready to catch you. You just shoot right through the center of the earth, and then gravity would start to slow you down again on your way through the other side of the tunnel.
Right it would. Now it's pulling you back.
Holding you back, it's slowing you down, and it's just enough gravity to slow you down so that you would emerge from the tunnel on the other side and then just stop.
With the same speed that you had just when you jumped in.
Yeah, which is zero right. So assuming that the tunnel on the other side comes out at exactly the same elevation, right, then you would come right out of the tunnel and you just sort of like hover right above the tunnel for a second before falling back down again. And if you didn't do anything, you would just sort of go back and forth, oscillating back and forth through the earth forever.
Whoa up and down, up and down. Have you calculated how long would take you to do that take that trip.
I've not done that calculation.
Actually leave it as homework for the listener.
But you have to be careful because if you jump, if your elevation you're distance from the center of the Earth when you jump is less than the elevation where you're going to come out on the other side, then you're not going to make it. Right. If you start on a death valley and you want to come out the Mount Everest, you're not gonna make to the top of Mount Everest, right.
You're just going to fall back down into the hole.
Yeah, exactly, exactly. But if the Earth was a perfect sphere and you jumped on the one side, then you would come out the other side at exactly the same height above the surface.
But if you slow yourself down and you stopped at the core, then you would be weightless and you'd be floating there.
Yeah, exactly, because the Earth's gravity would be pulling on you from every direction simultaneously, which is like having no gravity. Whoa, And that'd be a pretty awesome moment, right, It'd be like at the center of the Earth, the entire Earth around you, right, that would be Yeah, I hope you're not calustaphobic.
It'd be pretty hard to climb back out right, that's kind of the problem.
Yeah, that would be a very long climb. Oh my gosh. Wow, I hope somebody built the ladder, all right.
Well that that's that's what the Earth is made out of. And if you drop a pizza down a hole that goes through the center of Earth, it would just come right back to you, right eventually.
Yeah, Or you could deliver pizza to the other side of the Earth just by dropping through that hole and it would just like come on out the other side and float there.
For a second while somebody would grab it.
A totally realistic way. I bet Elon Musk is working on that pizzas.
And the bonus is it would be warm because it would heat up on the way. You could you could dump it in frozen and it would come out and nice and toasty.
This is a great business opportunity. I hope the lawyers just scribbling this down as you're talking.
All right, Well, thanks for joining us. I hope that that wasn't too hardcore for you guys out there.
I hope we didn't get too crusty on you, all.
Right, Thanks for joining us. See you next time.
Thanks for tuning in. If you still have a question after listening to all these explanations, please drop us a line. We'd love to hear from you. You can find us at Facebook, Twitter, and Instagram at Daniel and Jorge That's one Word, or email us at Feedback at Daniel and Jorge dot com. Thanks for listening and remember that Dan. Daniel and Jorge Explain the Universe is a production of iHeartRadio. For more podcasts from iHeartRadio, visit the iHeartRadio app, Apple Podcasts, or wherever you listen to your favorite shows. When you pop a piece of cheese into your mouth, you're probably not thinking about the environmental impact. But the people in the dairy industry are. That's why they're working hard every day to find new ways to reduce waste, conserve natural resources, and drive down greenhouse gas emissions. How is us dairy tackling greenhouse gases? Many farms use anaerobic digestors to turn the methane from manure into renewable energy that can power farms, towns, and electric cars. Visit you as dairy dot COM's Last Sustainability to learn more.
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