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Speaker 1: When we set out to understand the universe, we usually

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Speaker 1: start by looking up. After all, that's where the best

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Speaker 1: views are of the glittery cosmos stretched across billions of miles.

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Speaker 1: We wonder, are we alone? Is there anyone up there

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Speaker 1: looking back at us? But what if the best way

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Speaker 1: to find answers to questions about what's up there is

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Speaker 1: actually to look down under our feet. Hi, I'm Daniel.

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Speaker 1: I'm a particle physicist and a professor at UC Irvine,

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Speaker 1: and I desperately want to know who's out there in

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Speaker 1: the universe and if they are wondering the same things

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Speaker 1: we are. And Welcome to the podcast Daniel and Horace

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Speaker 1: Explain the Universe in which we do just that, wonder

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Speaker 1: about the nature of the universe and try to explain

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Speaker 1: all of it to you. Regular listeners the podcast, know

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Speaker 1: that I am desperate to understand the nature of the universe,

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Speaker 1: how it all works, and to explain all of that

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Speaker 1: knowledge and all of that confusion to you. One of

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Speaker 1: the deepest questions we wrestle with on the pod is

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Speaker 1: not just about the universe, but kind of about ourselves.

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Speaker 1: How weird? Are we are? There more like us out

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Speaker 1: there in the universe, or are we alone? How rare

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Speaker 1: and special is the Earth anyway? Are we one of

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Speaker 1: a kind out of a trillion planets, or are we

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Speaker 1: one of many rocky balls covered in Curious Life. We're

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Speaker 1: frustratingly limited by what we can learn about distant planets,

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Speaker 1: though we're doing our best. But something we can do

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Speaker 1: right now is drill deeper into our own planet, understand

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Speaker 1: the forces that shaped it and whether those are finely

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Speaker 1: balanced in a rare way or naturally in harmony, in

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Speaker 1: a way we'll find everywhere in the universe. So today

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Speaker 1: on the podcast, we'll be answering the question what's hidden

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Speaker 1: inside planets? And to help me explore this fascinating topic,

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Speaker 1: I'm pleasing to be speaking to Professor Sabina Stanley, author

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Speaker 1: of a very recent book of that same title. All right, well,

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Speaker 1: then it's my great pleasure to introduce the podcast Professor

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Speaker 1: Sabina Stanley. She's the Bloomberg Distinguished Professor of Planetary Physics

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Speaker 1: at Johns Hopkins University, where she focuses on magnetic fields

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Speaker 1: and other geophysical elements as a means of studying the

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Speaker 1: interiors of planets, moons, and asteroids. She's an Alfred Peasloan

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Speaker 1: Research Fellow, and has also received the William Gilbert Award

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Speaker 1: of the American Geophysical Union. Sabina, Welcome to the podcast,

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Speaker 1: and thank you for coming to talk to us.

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Speaker 2: Thanks so much for having me.

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Speaker 1: So one thing we always wonder about as we look

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Speaker 1: out into the night sky is all the other planets

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Speaker 1: that are out there. Of course we can't study mnie

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Speaker 1: them up close, and so often on this podcast we've

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Speaker 1: tried to dig into what's under our feet, the mysteries

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Speaker 1: that are right here in our Earth. And so I

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Speaker 1: really enjoyed your recent book, What's Hidden Inside Planets, and

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Speaker 1: I'd love to talk to you about what's in our planet.

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Speaker 1: Could you start us off by taking us sort of

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Speaker 1: on a brief tour of like what is under our feet,

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Speaker 1: layer by layer, all the way down to the core.

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Speaker 2: Yeah, absolutely, great question.

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Speaker 3: So I think it's interesting to note that when you

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Speaker 3: start on the surface, as you go deeper and deeper,

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Speaker 3: stuff gets kind of weirder and weirder and much more

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Speaker 3: different than what we're used to on the surface.

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Speaker 2: So we start on the crust.

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Speaker 3: This is where we live, This is where all the

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Speaker 3: stuff happens that we're used to crust can vary in

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Speaker 3: thickness five about you know, five kilometers depth to almost

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Speaker 3: one hundred kilometers depth. But under that you get to

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Speaker 3: the mantle that's also still mostly rocky, the type of

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Speaker 3: rocks that are rich in magnesium and silicates, but still

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Speaker 3: what we would recognize as rocks. So about half the

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Speaker 3: radius of the Earth are those rocks. It goes down

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Speaker 3: about two thousand miles deep.

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Speaker 1: So what distinguishes then between the crust and the mantle.

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Speaker 1: Is it like how squeezed they are and how much

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Speaker 1: they flow, or is it a different kind of rock?

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Speaker 2: Great question.

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Speaker 3: Yeah, it's a little bit different kind of rock. So

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Speaker 3: essentially the crust layer of the earth. I sometimes refer

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Speaker 3: to it as like the scum of the earth. So

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Speaker 3: it's kind of like, you know, like when you're making

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Speaker 3: a soup and you're boiling your broth and you've got

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Speaker 3: all that light, floaty stuff that comes to the top.

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Speaker 3: So the stuff that's the most buoyant when you have

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Speaker 3: certain heat, thermal reactions and chemical reactions happening with rocks

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Speaker 3: near the surface, all of that percolates up to the

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Speaker 3: top and that ends up becoming the crust, and then

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Speaker 3: sort of the stuff underneath might be less scummy, less

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Speaker 3: you know, it's been less reworked, and it's sort of

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Speaker 3: more kind of pristine rock.

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Speaker 1: I see, we're going to get started very quickly with

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Speaker 1: the food analogies.

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Speaker 2: Yeah, I'm sorry, it's just going to be how it goes.

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Speaker 3: It's going to be food involved in almost every analogy

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Speaker 3: I make.

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Speaker 2: Here.

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Speaker 1: Are you a big fan of soup or you a

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Speaker 1: cook at home?

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Speaker 3: So I'm a terrible cook, but I grew up in

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Speaker 3: a restaurant family, so I've been around sort of good

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Speaker 3: food my whole life.

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Speaker 1: All right, Well, then let's do our best to at

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Speaker 1: least use tasty food analogies. I don't want any want

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Speaker 1: to think that the earth is like a disgusting bowl

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Speaker 1: of soup. Maybe it's like, you know, bubbling hot cocoa,

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Speaker 1: and this is that delicious film that forms on top.

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Speaker 2: I love that so much. You don't even know. So

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Speaker 2: that's amazing, all right.

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Speaker 1: So the crust is the sort of coolest part that

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Speaker 1: floats to the top, and underneath that it's still rock,

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Speaker 1: but it's able to flow. How do we visualize that?

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Speaker 1: I mean, it's not like liquid lava that's flowing on

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Speaker 1: the surface. This is still like solid rock, but it's flowing.

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Speaker 1: How does solid rock flow is something I've always tried

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Speaker 1: to visualize and failed.

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Speaker 2: Yeah, So the answer to that question is very slowly.

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Speaker 1: Right.

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Speaker 3: So, yes, it's solid, but it's still deformable, right, And

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Speaker 3: I think we have experience with different types of solids

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Speaker 3: in our everyday life, and that some are more deformable

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Speaker 3: than other.

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Speaker 2: Right, Like you might have clay.

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Speaker 3: Clay is solid, but you can still deform it, whereas

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Speaker 3: a metal also is kind of deformable. But then you

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Speaker 3: have some rocks that are really like a diamond, really

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Speaker 3: hard to deform. But the rocks in the mantle, they

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Speaker 3: are solid, but they can be deformed, and if they

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Speaker 3: can be deformed, then they start being influenced by the

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Speaker 3: forces like gravity such that you can get them to flow.

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Speaker 1: I see, all right, So we have the crust and

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Speaker 1: we have the mantle. Both the wiz are still really rock.

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Speaker 1: Take us down below that, right.

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Speaker 3: So then you get down about halfway through the Earth

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Speaker 3: and you suddenly hit a very big boundary, complete change

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Speaker 3: of environment. Now you're at the iron core. So the

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Speaker 3: inner half of the planet about it's mostly made of iron.

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Speaker 3: There's a little bit of nickel mixed in there, and

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Speaker 3: about ten percent of some sort of lighter elements that

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Speaker 3: we have a whole sort of platter of possibilities for,

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Speaker 3: but we don't actually know what they are. And that

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Speaker 3: makes up the core. The core has two parts to it.

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Speaker 3: The outer port is liquid. It can flow very easily,

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Speaker 3: much faster timescales than the mantle, and it's really important

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Speaker 3: for us because that's where our magnetic field is generated

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Speaker 3: in that liquid iron core. Then below that, the innermost

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Speaker 3: thirteen hundred kilometers of our planet, is a solid iron core.

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Speaker 1: And so what distinguishes then the mantle, which can flow

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Speaker 1: but is a solid not a liquid, from the outer core,

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Speaker 1: which can flow but is a liquid and not a solid, Like,

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Speaker 1: is there really a distinction here? Are we just putting

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Speaker 1: labels on things?

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Speaker 3: When we study fluid dynamics, we talk a lot about

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Speaker 3: there being a spectrum of fluids. Right, nothing's ever purely

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Speaker 3: a solid or purely a fluid. It's all about the

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Speaker 3: time scales. So the mantle, for example, if you want

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Speaker 3: to talk about how materials flow in the mantle, a

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Speaker 3: parcel at the bottom of the mantle could take hundreds

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Speaker 3: of millions of years to make it to the top

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Speaker 3: of the mantle, whereas a parcel at the bottom of

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Speaker 3: the core could take a couple of years to get

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Speaker 3: the top of the core. So it's a very different

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Speaker 3: timescale of the flow. You could actually see changes in

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Speaker 3: material in the core flowing.

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Speaker 1: But this is also like a boundary. It's not like

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Speaker 1: there's a smooth, very gradual transition. There's like a line.

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Speaker 1: You can say, this is the core and this is

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Speaker 1: the mantle.

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Speaker 3: Yeah, And that happens because mantle, rocks, and iron in

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Speaker 3: the core have very different densities, and at one time

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Speaker 3: in the past in our planet, it was mostly molten

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Speaker 3: and so the heaviest stuff, when you have a bunch

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Speaker 3: of stuff mixed together, the heaviest stuff's going to sync

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Speaker 3: to the bottom. And so that's what happened in Earth.

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Speaker 3: All the iron, most of the irons, sunk to the

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Speaker 3: center of the Earth and made.

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Speaker 1: Up the core like the big chunks in a stew

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Speaker 1: or something exactly.

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Speaker 2: Yes, I like it.

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Speaker 1: So the reason that there's a boundary there and like

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Speaker 1: a transition or rather than just like a smooth gradation

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Speaker 1: from more liquid to less liquid, that reflects like the

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Speaker 1: phase transitions and materials. Is that right, the way that

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Speaker 1: like ice turns solid at some moment and doesn't just

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Speaker 1: like gradually become more and more solid.

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Speaker 3: I would say that's more representative of what kind of

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Speaker 3: happens at the inner core outer core boundary, so where

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Speaker 3: the iron becomes solid. But above that it's more kind

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Speaker 3: of like a maybe you go with an oil and

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Speaker 3: water type thing. You've got two materials with very different

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Speaker 3: density and very different properties, so it's really hard to

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Speaker 3: mix them.

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Speaker 1: Wonderful and tell us about how we know about this.

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Speaker 1: I was reading in your book this really exciting description

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Speaker 1: of the mantle race, basically like a parallel to the

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Speaker 1: space race, but into the Earth. Tell us about our

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Speaker 1: humanity's efforts to like literally tunnel to the center of

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Speaker 1: the Earth.

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Speaker 3: Yeah, So if you imagine you want to figure what's

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Speaker 3: inside the Earth, right, your first instinct might be, hey,

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Speaker 3: why don't we dig down as far as we can

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Speaker 3: and actually sample it?

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Speaker 2: Right?

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Speaker 3: And it's a great instinct. Unfortunately, it's incredibly challenging to do.

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Speaker 3: And that's because pressure increases so fast as you go

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Speaker 3: deeper inside the planet, and so do temperatures. So as

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Speaker 3: you can imagine, humans don't like really high pressures and temperatures.

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Speaker 3: Neither does equipment, and the farthest we've been able to

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Speaker 3: dig with sort of a really concerted effort to do so, right,

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Speaker 3: Like this was something on the scale of moonshot to

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Speaker 3: the Moon in the late sixties. This is something very

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Speaker 3: similar to that, And you could get only down to

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Speaker 3: about eight miles in depth, and the radius of the

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Speaker 3: Earth you're talking about four thousand miles, so tiny, tiny

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Speaker 3: scrape of the surface by going down that deep. Equipment

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Speaker 3: does not like high pressures and temperatures.

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Speaker 1: But how do you even get eight miles deep? I mean,

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Speaker 1: I remember digging in my backyard with a shovel, wondering

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Speaker 1: how far I could get, and it's not very far.

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Speaker 1: How do you get eight miles down?

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Speaker 3: This is like high tech technology kind of stuff. It's

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Speaker 3: at the limits of what we can do for drilling

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Speaker 3: that we do now to drill for resources, et cetera.

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Speaker 3: So it's a lot of fancy equipment and challenges that

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Speaker 3: are over met that way. So we can't dig and

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Speaker 3: we can't drill, But that's okay because there are other

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Speaker 3: ways we can figure out what's going on deeper inside

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Speaker 3: the earth.

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Speaker 1: Yeah, So tell us about some of those ways you

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Speaker 1: were talking in the book about diamonds, how we can

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Speaker 1: use diamonds to give us little snapshots of what's inside

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Speaker 1: the planet.

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Speaker 3: Yeah, so you know, it would be great if we

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Speaker 3: could dig down, but would it also be great if

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Speaker 3: the stuff down there came to us. And that's really

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Speaker 3: what happens with diamonds. Diamonds are produced deeper inside the Earth,

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Speaker 3: and then they come up to the surface, usually in

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Speaker 3: volcanic vent things known as kimber like pipes and those diamonds.

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Speaker 3: You know, Jewelers love diamonds when they're as pure as possible.

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Speaker 3: Geologists love diamonds when they're as impure as possible. So

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Speaker 3: sometimes diamonds, when they form, they can enclose a little

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Speaker 3: capsule of some of the material where they formed inside them, right,

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Speaker 3: So you might get a little bit of garnet in

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Speaker 3: the diamond or a little bit of something that was

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Speaker 3: created deeper in the earth. And when it it up,

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Speaker 3: because diamonds so strong, it actually keeps the material in

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Speaker 3: its like pristine form, So you really have this like

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Speaker 3: sample from the interior of the Earth come to the

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Speaker 3: surface for us to investigate. So that's a great way

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Speaker 3: and we've used that, for example, to figure out that

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Speaker 3: there is actually water deeper inside the Earth because we've

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Speaker 3: found water inside diamond inclusions.

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Speaker 1: It's fascinating to me though, that this thing that you

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Speaker 1: make in a high pressure environment, when you bring it

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Speaker 1: up to low pressure, it doesn't explode. Is that just

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Speaker 1: because of the incredible structure of diamond?

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Speaker 2: Yeah.

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Speaker 3: When they say diamonds are forever, that's technically not true, right,

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Speaker 3: They just have a really really long lifetime before they

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Speaker 3: revert back to their carbon phase.

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Speaker 2: So yeah, it's just a great property of diamond.

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Speaker 1: So is it's sort of like you know, you put

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Speaker 1: a pan of brownies in the oven and it changes

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Speaker 1: into something else, and when you take it out, cool

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Speaker 1: it down, it doesn't revert back into batter.

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Speaker 2: That's an excellent way of thinking about it.

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Speaker 1: Yeah, okay, And so then what have we learned from

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Speaker 1: these diamond samples? Like what's inside these diamonds that we

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Speaker 1: didn't realize other than water?

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Speaker 2: Yeah? I think water is the big thing.

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Speaker 3: Sometimes it's a lot about sort of the smaller amounts

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Speaker 3: of elements that we don't know about, Right, how much

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Speaker 3: of a particular kind of silicon down there is sulfur,

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Speaker 3: down there these kinds of questions, and those all just

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Speaker 3: help us understand what the building blocks of Earth were

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Speaker 3: when Earth formed, and what the geochemistry the kind of

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Speaker 3: chemical reactions that can occur as material descends into the Earth.

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Speaker 3: That's really where we get that information. But even with diamonds, right,

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Speaker 3: we're talking about the outermost layers of the mantle, right, diamonds.

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Speaker 3: We don't get diamonds safe from the core mantle boundary

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Speaker 3: or anywhere deeper than that. So we can't use the

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Speaker 3: diamonds to learn about the deeper parts.

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Speaker 1: Is that because diamonds aren't made deeper or because diamonds

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Speaker 1: from that far down just don't make it up to

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Speaker 1: the surface.

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Speaker 3: Mostly the latter, I think also, like if you get

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Speaker 3: carbon down there, yeah, it doesn't necessarily join into making

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Speaker 3: diamond at that depth.

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Speaker 1: All right, So there aren't like huge diamonds buried deep

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Speaker 1: in the earth that we are not on Earth, not

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Speaker 1: on Earth. Well, that was my whole motivation for digging

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Speaker 1: so deeply when I was a kid, fantasizing about revealing

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Speaker 1: some you know, boulder sized diamond. All right, So diamonds

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Speaker 1: give us one sample of what else can we do?

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Speaker 1: What about gravity? What about just studying like the variation

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Speaker 1: in Earth's gravity as we you know, orbit to planate

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Speaker 1: or look around it. What does that tell us about

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Speaker 1: what's inside the Earth.

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Speaker 3: The way I like to think about it is, you know,

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Speaker 3: if you want to figure out what's going on inside

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Speaker 3: the Earth, try and make an analogy to a human body.

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Speaker 3: Right if you if you have an ache and you

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Speaker 3: go to your doctor and you're like this hurts. Hopefully

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Speaker 3: they're not. Their first kind of instinct is not to

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Speaker 3: drill a hole in you to figure that out. Right,

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Speaker 3: There are ways that they can use different fields and

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Speaker 3: different scans to figure out what's wrong with your insides,

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Speaker 3: And we can do the same thing for the inside

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Speaker 3: of the Earth. So we can scan gravity as you mentioned,

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Speaker 3: that's one, Magnetic fields is another one.

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Speaker 2: And we can also determine.

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Speaker 3: Properties of waves that travel through the Earth from earthquakes

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Speaker 3: through seismology. So we can use all these scanning techniques

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Speaker 3: to figure out what's going on deeper inside the Earth.

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Speaker 1: So what do you mean by using gravity? Is it

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Speaker 1: just like measuring the variations of gravity so that we

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Speaker 1: understand how the Earth is not a perfect sphere or

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Speaker 1: how they'rear is not homogeneous in density. What is it

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Speaker 1: we're learning?

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Speaker 2: Yeah, great question.

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Speaker 3: So, yeah, it really is the fact that both isn't

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Speaker 3: a perfect sphere and has some inhomogeneous material below it. Right,

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Speaker 3: So if you were walking around with a griviminter that

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Speaker 3: could measure gravity and it was really really good and

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Speaker 3: you walked around, you would get slightly different values everywhere

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Speaker 3: you walk, and that would be determined by the mass

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Speaker 3: directly under your feet. And so we can use that information.

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Speaker 3: We have spacecraft that orbit the Earth that measure Earth's

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Speaker 3: gravity feel to really high precision, and we can use

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Speaker 3: that to figure out what is the distribution of density

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Speaker 3: inside the Earth. And that kind of allows us to

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Speaker 3: kind of image what's going on. Where's the denser stuff

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Speaker 3: in the Earth, where's the lighter stuff? And we can

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Speaker 3: actually see things like convection cells in the mantle and

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Speaker 3: plumes of magma coming up for volcanoes, things like this.

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Speaker 1: But gravity is such a weak force. How do you

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Speaker 1: identify these variations in density with such an incredibly weak force.

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Speaker 1: They must be pretty big effects.

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Speaker 3: They aren't. They are very very tiny effect. We're just

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Speaker 3: really good at measuring them.

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Speaker 1: Emitter, you mentioned this might seem like a weird object

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Speaker 1: or listeners. But I guess, like my bathroom scale is

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Speaker 1: a gravi emitter. If I walked around the Earth with

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Speaker 1: my bathroom scale, I would measure different weights before and

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Speaker 1: after lunch, of course, but also if I didn't need anything,

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Speaker 1: or I user reference mass, then I guess I would

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Speaker 1: measure different accelerations due to gravity.

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Speaker 2: Yeah.

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Speaker 3: Absolutely, And if you are someone on the surface taking

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Speaker 3: gravity measurements, that's exactly the kind of instrument you would use. Interestingly,

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Speaker 3: once we get into orbiting around a planet like Earth

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Speaker 3: to take measurements, we use a completely different technique. We

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Speaker 3: basically use the fact that if we have a spacecraft

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Speaker 3: in orbit around the Earth, we know it's in orbit

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Speaker 3: around the Earth, and its orbital speed and altitude is

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Speaker 3: completely determined by the mass of the planet.

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Speaker 2: So we can use things.

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Speaker 3: Like two spacecraft just slightly at different locations from each

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Speaker 3: other kind of moving around, and we can use the

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Speaker 3: distance between the two spacecraft as like a proxy for

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Speaker 3: how much g is right where they are, how much

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Speaker 3: the gravity is right where they are. So that's actually

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Speaker 3: how it's done in practice with spacecraft.

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Speaker 1: Wow, that's incredible, And how sensitive are they? I mean,

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Speaker 1: like one part in a thousand, one part in a million.

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Speaker 2: Yeah, one part in a million. That's where we're getting to.

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Speaker 1: Wow, So they can really tell if I've eaten lunch.

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Speaker 1: Some spacecraft up there can tell that the mass of

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Speaker 1: the Earth has changed.

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Speaker 3: One thing they're actually used for. So the Grace satellites,

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Speaker 3: which orbited Earth for about ten years, one of their

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Speaker 3: main applications was to follow water flow on the surface,

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Speaker 3: so you could see, for example, when water was filling

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Speaker 3: reservoirs underground reservoirs in certain parts of the country or

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Speaker 3: different countries if you wanted to see are we going

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Speaker 3: to have a drought, are we in a rainstorm season,

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Speaker 3: or what's the water situation going on here?

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Speaker 2: So we can even use gravity to tract climate change.

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Speaker 1: Wow, that sounds like modern day divining rods. But you're

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Speaker 1: actually using science to find the water underground. That's incredible,

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Speaker 1: all right, So gravity's one way to do it. You

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Speaker 1: also mentioned seismic probes. These are like waves inside the earth.

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Speaker 1: How do we use that to see what's going on?

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Speaker 3: So every time there's an earthquake, it's like sort of

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Speaker 3: something kind of punched the inside of the Earth at

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Speaker 3: some point and it causes the Earth to ring. It

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Speaker 3: causes waves to travel through the interior of the Earth

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Speaker 3: and on the surface of the Earth. If we put

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Speaker 3: out a bunch of instruments that can kind of measure

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Speaker 3: the shaking, so seismographs, then we can figure out a

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Speaker 3: few things.

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Speaker 2: About the earthquake waves.

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Speaker 3: We can figure out when they arrive at different locations

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Speaker 3: around the planet, and how big the waves are, the

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Speaker 3: amplitude of the waves.

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Speaker 2: And the speed.

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Speaker 3: The timing of when the waves arrive is completely directly

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Speaker 3: related to the material properties that the waves traveled through.

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Speaker 3: So for example, we can figure out the density of

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Speaker 3: material that a wave traveled safe from. Let's say an

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Speaker 3: earthquake happens in California and the wave travels up to

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Speaker 3: Seattle in Washington. You can use that to figure out

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Speaker 3: kind of what's the material just under the surface there,

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Speaker 3: Whereas if you try to go across the globe to

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Speaker 3: another part on the other side, the waves might travel

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Speaker 3: through the entire planet and we could actually sample the

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Speaker 3: material in the.

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Speaker 2: Core for example.

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Speaker 3: So you can use all those different measurements. The more

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Speaker 3: locations you have on the Earth for these seismic measurements

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Speaker 3: to be made, the more you can kind of discern

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Speaker 3: what is the lateral structure of the.

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Speaker 2: Interior of the Earth.

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Speaker 1: And we're really talking about sound waves, right, These are

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Speaker 1: pressure waves in the rock, and so we can think

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Speaker 1: about how denser materials have sound travel faster, and less

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Speaker 1: dense materials sound travels lower. So you're measuring the density

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Speaker 1: of the material by measuring the speed of sound. But again,

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Speaker 1: these are rocks that are like pushing on each other, right,

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Speaker 1: Like sound waves through rock is a very weird thing

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Speaker 1: to think about.

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Speaker 3: Yeah, absolutely, So there are the sound waves that The

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Speaker 3: other type of wave that goes through are these sheer waves.

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Speaker 3: So those are kind of more like waves you'd experience

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Speaker 3: in a fluid, let's say, or not in fluid, sorry,

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Speaker 3: waves that you would experience if you try to kind

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Speaker 3: of bend peanut butter or something like that. Right, So

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Speaker 3: there's multiple kinds of waves, and some of them are

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Speaker 3: very diagnostic of what's going on in certain types of materials.

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Speaker 1: Well, I never thought we'd be talking about peanut butter waves,

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Speaker 1: but here we are. So when did we get this picture, Like,

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Speaker 1: what is the first technique that really gave us a

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Speaker 1: view of the inside of the earth. Was it the

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Speaker 1: seismographs or is it something else.

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Speaker 2: That's a good question.

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Speaker 3: It's not like there was a sun moment where suddenly

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Speaker 3: we had this picture of the Earth. I think we

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Speaker 3: develop our understanding to higher and higher precision as time

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Speaker 3: went on.

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Speaker 2: Right, I think early studies.

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Speaker 3: Of gravity, going back to Newton, let's say, was able

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Speaker 3: to tell us this is the mass of the Earth,

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Speaker 3: and then you could take, for example, samples of crustal

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Speaker 3: rocks and figure out what their density was and infer, hey,

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Speaker 3: there must be a lot more mass deeper in the center.

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Speaker 3: So that was kind of first order information you might

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Speaker 3: get so through both seismology. So early nineteen hundreds was

443
00:19:23,440 --> 00:19:25,880
Speaker 3: when we were doing some really great seismology figuring out

444
00:19:26,280 --> 00:19:28,560
Speaker 3: things like, oh, look we have a core. Right, that

445
00:19:28,720 --> 00:19:30,840
Speaker 3: was where the core was first discovered. The inner core

446
00:19:30,960 --> 00:19:33,440
Speaker 3: was discovered in the early nineteen hundreds. The first sort

447
00:19:33,440 --> 00:19:37,000
Speaker 3: of real profile of density through the Earth happened, I

448
00:19:37,040 --> 00:19:38,760
Speaker 3: think it was in the seventies with what was called

449
00:19:38,760 --> 00:19:42,160
Speaker 3: the Preliminary Reference Earth Model, which really used a whole

450
00:19:42,200 --> 00:19:44,080
Speaker 3: bunch of seismic data to really kind of do an

451
00:19:44,119 --> 00:19:47,160
Speaker 3: inverse problem and figure out here's what the seismic wave

452
00:19:47,200 --> 00:19:49,159
Speaker 3: speed and the density has to be at every depth

453
00:19:49,440 --> 00:19:51,280
Speaker 3: the in sort of like a won d earth. So

454
00:19:51,320 --> 00:19:54,080
Speaker 3: that was a big step forward there too. But at

455
00:19:54,119 --> 00:19:56,479
Speaker 3: the same time, gravity was being used, and so we

456
00:19:56,480 --> 00:19:58,359
Speaker 3: were getting pictures from different types.

457
00:19:58,119 --> 00:20:01,000
Speaker 1: Of information, But were the only a few hundred years

458
00:20:01,000 --> 00:20:03,240
Speaker 1: that we've had any sort of reasonable idea of what's

459
00:20:03,320 --> 00:20:05,160
Speaker 1: under our feet. And it sounds like only the last

460
00:20:05,200 --> 00:20:08,160
Speaker 1: few decades, maybe fifty years, that we've had any sort

461
00:20:08,160 --> 00:20:11,119
Speaker 1: of detailed picture of what's actually inside our own planet.

462
00:20:11,160 --> 00:20:14,160
Speaker 1: It's incredible how long we can remain ignorant about really

463
00:20:14,200 --> 00:20:16,240
Speaker 1: basic science about our own lives.

464
00:20:16,440 --> 00:20:19,840
Speaker 3: Yeah, when I talk to people, I tell them geophysics

465
00:20:20,040 --> 00:20:22,560
Speaker 3: is really modern physics because all of the stuff we're

466
00:20:22,600 --> 00:20:24,679
Speaker 3: doing now is all stuff that's happened sort of in

467
00:20:24,680 --> 00:20:27,080
Speaker 3: the last sixty seventy years. So I'd like to think

468
00:20:27,119 --> 00:20:28,840
Speaker 3: of it as a modern physics.

469
00:20:28,520 --> 00:20:32,520
Speaker 1: Approach, right, And now we've extended this frontier two other planets.

470
00:20:32,560 --> 00:20:34,800
Speaker 1: We've talked in the podcast before about the Insite mission,

471
00:20:34,840 --> 00:20:37,440
Speaker 1: and I think you worked on that measuring Mars quakes

472
00:20:37,480 --> 00:20:41,200
Speaker 1: to see what's inside Mars. Did the same principles apply there?

473
00:20:41,320 --> 00:20:44,119
Speaker 3: Yes, absolutely, So the amazing thing with the Inside mission

474
00:20:44,359 --> 00:20:47,720
Speaker 3: is brought a seismometer, and that seismometer had to be

475
00:20:47,760 --> 00:20:50,120
Speaker 3: placed onto the surface of Mars so that it could

476
00:20:50,119 --> 00:20:53,719
Speaker 3: measure the ground shaking essentially, and it worked, like it

477
00:20:53,760 --> 00:20:55,560
Speaker 3: was just amazing that it worked. But it was a

478
00:20:55,640 --> 00:20:59,240
Speaker 3: very interesting experience because for most of the mission, and

479
00:20:59,320 --> 00:21:02,639
Speaker 3: especially in the big all the Mars quakes we were

480
00:21:02,640 --> 00:21:03,879
Speaker 3: seeing were quite weak.

481
00:21:04,280 --> 00:21:05,000
Speaker 2: We were looking for.

482
00:21:04,920 --> 00:21:07,160
Speaker 3: The big one, right, We're looking for the big Mars quake,

483
00:21:07,359 --> 00:21:09,840
Speaker 3: because the bigger the quake, the more ways we'll travel

484
00:21:09,880 --> 00:21:11,960
Speaker 3: through the deeper parts of Mars. And so we really

485
00:21:11,960 --> 00:21:14,359
Speaker 3: wanted to study or I really wanted to study the core,

486
00:21:14,720 --> 00:21:16,480
Speaker 3: and for that we needed some big Mars quakes, and

487
00:21:16,520 --> 00:21:18,600
Speaker 3: they really didn't happen for the first few years, and

488
00:21:18,640 --> 00:21:21,160
Speaker 3: then right near when the mission was about to end,

489
00:21:21,240 --> 00:21:23,360
Speaker 3: we suddenly had a few. So that was really amazing

490
00:21:23,400 --> 00:21:25,160
Speaker 3: to get that data at the end. So Mars kind

491
00:21:25,160 --> 00:21:27,560
Speaker 3: of kept us hoping for a while and then finally delivered.

492
00:21:27,800 --> 00:21:30,280
Speaker 1: And before you landed on Mars with this seismometer, did

493
00:21:30,320 --> 00:21:33,560
Speaker 1: you have much reason to expect that there were Mars quakes?

494
00:21:33,720 --> 00:21:36,000
Speaker 1: Or it could be that Mars was totally silent.

495
00:21:36,160 --> 00:21:37,760
Speaker 3: I mean it could have been we didn't have any

496
00:21:37,800 --> 00:21:40,720
Speaker 3: direct evidence from Mars quakes. But my geologist friends who

497
00:21:40,760 --> 00:21:43,399
Speaker 3: are used to looking at say tectonic features on the surface,

498
00:21:43,440 --> 00:21:45,560
Speaker 3: looking at things like where are the cracks in the surface,

499
00:21:45,560 --> 00:21:47,560
Speaker 3: where are the mountains, they would have told me to

500
00:21:47,600 --> 00:21:52,040
Speaker 3: expect Mars quakes because they see movements geologically, they see

501
00:21:52,080 --> 00:21:55,040
Speaker 3: movements on the surface. But also, luckily, we kind of

502
00:21:55,040 --> 00:21:57,720
Speaker 3: have our own source of Mars quakes. In a way,

503
00:21:58,040 --> 00:22:02,120
Speaker 3: when meteors hit planet, they crash into them. They're kind

504
00:22:02,160 --> 00:22:05,400
Speaker 3: of like a hammer that's smashing into a bell, right,

505
00:22:05,600 --> 00:22:07,600
Speaker 3: And so a lot of the Mars quakes we measured

506
00:22:07,640 --> 00:22:10,119
Speaker 3: were actually caused by meteors that hit Mars as opposed

507
00:22:10,160 --> 00:22:12,520
Speaker 3: to just tectonic activity happening in the interior.

508
00:22:12,600 --> 00:22:14,800
Speaker 1: Well, it's terrifying to me or feel a little conflicted

509
00:22:14,960 --> 00:22:18,359
Speaker 1: the geologists are rooting for quakes and rooting for like

510
00:22:18,400 --> 00:22:20,880
Speaker 1: big impacts because they're like, ooh, yay data.

511
00:22:21,760 --> 00:22:23,200
Speaker 2: Yes exactly, I will.

512
00:22:23,280 --> 00:22:25,719
Speaker 3: I mean, as a funny story on the mission, we

513
00:22:25,880 --> 00:22:27,879
Speaker 3: did at one point, so the Insight mission was on

514
00:22:27,920 --> 00:22:32,280
Speaker 3: the surface when the Perseverance rover was planning to land,

515
00:22:32,520 --> 00:22:34,760
Speaker 3: and we did kind of do a calculation where if

516
00:22:34,760 --> 00:22:37,840
Speaker 3: the landing didn't go so well would be able to

517
00:22:37,880 --> 00:22:39,000
Speaker 3: detect the way from that.

518
00:22:39,160 --> 00:22:42,080
Speaker 2: Luckily that didn't happen. We had a very nice landing.

519
00:22:42,520 --> 00:22:45,119
Speaker 1: Congratulations on your landing. Too bad we didn't get some

520
00:22:45,119 --> 00:22:48,600
Speaker 1: cool data though from your explosion of your huge project.

521
00:22:48,800 --> 00:22:51,159
Speaker 1: Oh my gosh. All right, this is really fun and

522
00:22:51,200 --> 00:22:53,240
Speaker 1: I want to hear a lot more about what's going

523
00:22:53,280 --> 00:23:09,639
Speaker 1: on inside our planet. But first let's take a quick break. Okay,

524
00:23:09,640 --> 00:23:12,600
Speaker 1: we're back. We're talking to Professor Sabina Stanley, author of

525
00:23:12,640 --> 00:23:16,959
Speaker 1: the book What's Hidden Inside Planets, about what's inside our planet.

526
00:23:17,240 --> 00:23:20,399
Speaker 1: You mentioned earlier that it was amazing that insight worked.

527
00:23:20,520 --> 00:23:22,399
Speaker 1: Is that just because it's hard to land stuff on

528
00:23:22,560 --> 00:23:25,159
Speaker 1: Mars and operate a robot on another planet or was

529
00:23:25,200 --> 00:23:28,959
Speaker 1: there something particularly challenging about a seismometer on another planet.

530
00:23:29,119 --> 00:23:32,080
Speaker 3: Yeah, Inside had a lot of firsts, I would say, right,

531
00:23:32,119 --> 00:23:34,359
Speaker 3: it wasn't the first lander. We've had other landers on

532
00:23:34,359 --> 00:23:36,080
Speaker 3: the surface, but this was the first time we were

533
00:23:36,119 --> 00:23:38,560
Speaker 3: going to take equipment that was stored on top of

534
00:23:38,600 --> 00:23:41,320
Speaker 3: the lander and actually physically move it to put it

535
00:23:41,359 --> 00:23:43,280
Speaker 3: on the surface. So there were lots of ways that

536
00:23:43,320 --> 00:23:45,640
Speaker 3: could have gone wrong. Right, This lander had this arm

537
00:23:46,080 --> 00:23:48,800
Speaker 3: type device that had to pick up the seismometer on

538
00:23:48,920 --> 00:23:52,960
Speaker 3: the lander and move it onto the surface. So that required,

539
00:23:53,119 --> 00:23:54,760
Speaker 3: you know, tons of work to get that to just

540
00:23:54,840 --> 00:23:57,439
Speaker 3: work properly. Then it had to put a windshield on

541
00:23:57,520 --> 00:23:59,920
Speaker 3: top of the seismometer to make sure that we didn't

542
00:24:00,000 --> 00:24:03,120
Speaker 3: measure a bunch of wind basically because wind also shakes schismometers.

543
00:24:03,960 --> 00:24:06,760
Speaker 3: Then you know that the seismometer wasn't the only instrument

544
00:24:07,080 --> 00:24:11,560
Speaker 3: on Insight. There was also a thermal probe what we

545
00:24:11,800 --> 00:24:14,639
Speaker 3: called the mole, which was supposed to dig down about

546
00:24:14,680 --> 00:24:18,440
Speaker 3: ten meters and take temperature measurements at depth, which would

547
00:24:18,560 --> 00:24:21,320
Speaker 3: have told us about the heat flow coming out of Mars.

548
00:24:21,600 --> 00:24:23,240
Speaker 2: Again, this was going to be the first time.

549
00:24:23,040 --> 00:24:27,879
Speaker 3: Anything like this was tried, and unfortunately we couldn't get

550
00:24:27,880 --> 00:24:30,960
Speaker 3: the mole to dig deeper than about tens of centimeters.

551
00:24:31,240 --> 00:24:35,399
Speaker 3: The properties of the soils kind of a word we use,

552
00:24:35,440 --> 00:24:38,840
Speaker 3: but the properties of the sand on Mars were not

553
00:24:38,960 --> 00:24:42,640
Speaker 3: as we expected, and just the device couldn't actually use

554
00:24:42,680 --> 00:24:45,159
Speaker 3: friction to dig down deeper and deeper. So that was

555
00:24:45,200 --> 00:24:48,840
Speaker 3: a struggle and we actually the Insight engineering team that

556
00:24:49,280 --> 00:24:51,040
Speaker 3: worked on this and the scientists that worked on this,

557
00:24:51,240 --> 00:24:52,720
Speaker 3: you know, I wasn't part of this. It was just

558
00:24:52,760 --> 00:24:55,479
Speaker 3: amazing the things that they tried, and in the end

559
00:24:55,480 --> 00:24:57,199
Speaker 3: we actually did get some good science out of it.

560
00:24:57,200 --> 00:24:58,720
Speaker 2: We measured more sort of the thermal.

561
00:24:58,440 --> 00:25:00,600
Speaker 3: Properties at the upper part of the cross as opposed

562
00:25:00,640 --> 00:25:03,359
Speaker 3: to deeper down. But it was just amazing to see

563
00:25:03,560 --> 00:25:05,919
Speaker 3: how much they tried to work on doing this first

564
00:25:06,040 --> 00:25:07,960
Speaker 3: digging on here. You know, we talked about digging on

565
00:25:08,000 --> 00:25:10,560
Speaker 3: the Earth is hard. Now imagine digging on another planet

566
00:25:10,560 --> 00:25:12,399
Speaker 3: without humans, and it's even harder.

567
00:25:12,600 --> 00:25:15,000
Speaker 1: Wonderful, And then what are the plans for the future.

568
00:25:15,080 --> 00:25:18,120
Speaker 1: Is NASA planning to dig into the surfaces of any

569
00:25:18,160 --> 00:25:21,520
Speaker 1: other objects in the Solar System or put seismometers on

570
00:25:21,560 --> 00:25:22,520
Speaker 1: any other surfaces.

571
00:25:22,680 --> 00:25:25,800
Speaker 3: So I think seismometers is definitely something that's going to go.

572
00:25:25,960 --> 00:25:28,040
Speaker 3: So there is a big push right now to send

573
00:25:28,080 --> 00:25:31,000
Speaker 3: spacecraft back to the Moon so that we can better

574
00:25:31,119 --> 00:25:35,320
Speaker 3: understand our closest celestial body, let's say. And so there

575
00:25:35,359 --> 00:25:37,840
Speaker 3: is a mission that will involve putting a seismometer, putting

576
00:25:37,840 --> 00:25:40,240
Speaker 3: more seismometers on the Moon. We already have some seismometers

577
00:25:40,280 --> 00:25:42,359
Speaker 3: on the Moon that were turned off a while ago

578
00:25:42,400 --> 00:25:45,400
Speaker 3: for budgetary reasons, right, So it'll be great to get

579
00:25:45,440 --> 00:25:47,960
Speaker 3: seismology again on the Moon. But for me, the most

580
00:25:48,000 --> 00:25:51,920
Speaker 3: exciting is that an upcoming mission that's planned to go

581
00:25:52,000 --> 00:25:55,000
Speaker 3: to Titan, which is a moon of Saturn, is actually

582
00:25:55,000 --> 00:25:56,720
Speaker 3: going to have a seismometer on it as well. So

583
00:25:56,800 --> 00:25:59,000
Speaker 3: it'll be interesting to see what we can learn about

584
00:25:59,000 --> 00:26:00,399
Speaker 3: the interior of.

585
00:26:00,280 --> 00:26:02,240
Speaker 1: Titan, and what do we know right now about the

586
00:26:02,240 --> 00:26:04,960
Speaker 1: interior of Titan, And how could we know anything about

587
00:26:05,000 --> 00:26:07,199
Speaker 1: it just from like looking at a few photons that

588
00:26:07,240 --> 00:26:08,320
Speaker 1: happened to reflect off of it.

589
00:26:08,520 --> 00:26:10,800
Speaker 3: So Titan is one of my favorite places, so it's

590
00:26:10,840 --> 00:26:12,400
Speaker 3: really exciting to think about what they're going to see.

591
00:26:12,400 --> 00:26:14,399
Speaker 3: So Titan's a unique place. First of all, it's the

592
00:26:14,440 --> 00:26:17,440
Speaker 3: only other planetary body in the Solar System that has

593
00:26:17,440 --> 00:26:20,640
Speaker 3: a nitrogen based atmosphere that's thick like the Earth's right,

594
00:26:20,680 --> 00:26:24,560
Speaker 3: So earth Is atmosphere is mostly nitrogen, and the surface

595
00:26:24,560 --> 00:26:27,040
Speaker 3: pressure on Titan is about one and a half bars,

596
00:26:27,080 --> 00:26:29,160
Speaker 3: so one and a half Earth atmospheres. But the cool

597
00:26:29,160 --> 00:26:31,800
Speaker 3: thing about Titan is that it's a small planet and

598
00:26:31,840 --> 00:26:33,719
Speaker 3: so it has very little mass and so its gravity

599
00:26:33,800 --> 00:26:36,159
Speaker 3: is really low. So if you were to go to

600
00:26:36,200 --> 00:26:39,159
Speaker 3: Titan and put some cardboard on your arms and flap them,

601
00:26:39,200 --> 00:26:41,159
Speaker 3: you would be able to fly on Titan because you

602
00:26:41,160 --> 00:26:45,440
Speaker 3: have ideal buoyancy situation there. You've got thick atmosphere, low gravity,

603
00:26:45,480 --> 00:26:47,000
Speaker 3: so it's really easy to fly there.

604
00:26:47,160 --> 00:26:49,560
Speaker 1: So in contrast, like they had the helicopter on Mars,

605
00:26:49,640 --> 00:26:51,680
Speaker 1: that was a real challenge because the atmosphere was thin

606
00:26:52,240 --> 00:26:55,560
Speaker 1: and the helicopter needs atmosphere exactly exactly.

607
00:26:56,080 --> 00:26:59,040
Speaker 3: So the Dragonfly mission, which is going to Titan, should

608
00:26:59,040 --> 00:27:02,040
Speaker 3: get there in the mid twenty thirties. It is going

609
00:27:02,119 --> 00:27:04,920
Speaker 3: to involve a dual quad copter. So this thing has

610
00:27:04,960 --> 00:27:09,520
Speaker 3: basically eight rotors and this to me, because I'm Canadian,

611
00:27:09,600 --> 00:27:12,000
Speaker 3: it looks like a skidoo or a snowmobile because it

612
00:27:12,040 --> 00:27:16,080
Speaker 3: has these sled tracks underneath it. But it's basically going

613
00:27:16,119 --> 00:27:18,880
Speaker 3: to fly around land somewhere, do a bunch of science,

614
00:27:19,200 --> 00:27:22,880
Speaker 3: then take off again, look for a new location, scout somewhat,

615
00:27:23,000 --> 00:27:24,840
Speaker 3: then fly to a new location, land again. And so

616
00:27:24,880 --> 00:27:28,200
Speaker 3: it's going to be able to do ground local science

617
00:27:28,320 --> 00:27:30,760
Speaker 3: right at an individual location for a bunch of locations

618
00:27:30,800 --> 00:27:33,680
Speaker 3: over the surface. And that's really the challenge in planetary

619
00:27:33,720 --> 00:27:36,680
Speaker 3: science is this kind of combination of get lots of

620
00:27:36,760 --> 00:27:39,960
Speaker 3: data from lots of different places really locally, really close

621
00:27:39,960 --> 00:27:41,280
Speaker 3: to the surface. So that's going to be a very

622
00:27:41,320 --> 00:27:42,040
Speaker 3: exciting mission.

623
00:27:42,200 --> 00:27:43,840
Speaker 1: We'd have to ask you about that. Is that going

624
00:27:43,920 --> 00:27:45,960
Speaker 1: to be self directed? Is it going to decide on

625
00:27:46,000 --> 00:27:47,440
Speaker 1: its own where to go or is it going to

626
00:27:47,640 --> 00:27:50,639
Speaker 1: wait for signals for minutes and minutes from Earth?

627
00:27:50,840 --> 00:27:53,639
Speaker 3: Full disclosure here, I have no involvement in the Dragonfly mission.

628
00:27:53,640 --> 00:27:56,320
Speaker 3: I'm just a super fan. But my understanding is what

629
00:27:56,359 --> 00:27:58,720
Speaker 3: it's going to do is when it kind of goes

630
00:27:58,880 --> 00:27:59,880
Speaker 3: up the one time.

631
00:28:00,000 --> 00:28:01,119
Speaker 2: When it flies up one time.

632
00:28:00,960 --> 00:28:03,320
Speaker 3: It's going to survey, It's going to look around, then

633
00:28:03,359 --> 00:28:06,680
Speaker 3: it'll come back down recharge its batteries. And during that time,

634
00:28:06,720 --> 00:28:08,439
Speaker 3: when the data gets back to Earth, people are going

635
00:28:08,520 --> 00:28:11,080
Speaker 3: to look around and say, let's go here, right that

636
00:28:11,160 --> 00:28:13,040
Speaker 3: place over there looks kind of interesting. So it'll be

637
00:28:13,080 --> 00:28:16,159
Speaker 3: a combination. Some of the in time flight stuff is

638
00:28:16,200 --> 00:28:19,159
Speaker 3: going to have to be done by the spacecraft by itself,

639
00:28:19,160 --> 00:28:21,080
Speaker 3: but when it comes to making decisions about where to

640
00:28:21,119 --> 00:28:23,280
Speaker 3: go next in terms of big steps, that's going to

641
00:28:23,320 --> 00:28:24,280
Speaker 3: be done by the people.

642
00:28:24,040 --> 00:28:24,640
Speaker 2: Back here on Earth.

643
00:28:24,680 --> 00:28:27,920
Speaker 1: I really liked your comment about needing to sample several places.

644
00:28:28,200 --> 00:28:30,320
Speaker 1: It seems obvious that if you only land on Earth

645
00:28:30,320 --> 00:28:32,720
Speaker 1: in one place, you might conclude, oh, this whole place

646
00:28:32,800 --> 00:28:35,800
Speaker 1: is granted or oh, look, it's all beautiful marble or something.

647
00:28:36,000 --> 00:28:38,800
Speaker 1: Obviously you need to look around to get a better sample.

648
00:28:39,160 --> 00:28:40,960
Speaker 1: And so when we only land on one place on

649
00:28:41,000 --> 00:28:43,680
Speaker 1: the Moon, like the Apollo astronauts, you know, only looked

650
00:28:43,880 --> 00:28:46,720
Speaker 1: or near where they landed, we may have gotten a

651
00:28:46,720 --> 00:28:49,120
Speaker 1: bias sample of what's going on up there. So that's

652
00:28:49,200 --> 00:28:51,400
Speaker 1: really cool that they're going to explore it. So other

653
00:28:51,480 --> 00:28:53,520
Speaker 1: than landing on the surface. In your book, you were

654
00:28:53,560 --> 00:28:56,960
Speaker 1: talking about seeing what's inside a planet by basically how

655
00:28:56,960 --> 00:28:59,280
Speaker 1: it wobbles. Can you walk us through the physics of that,

656
00:28:59,320 --> 00:29:01,720
Speaker 1: the moment off and how it gives us a picture

657
00:29:01,720 --> 00:29:02,680
Speaker 1: of what's inside.

658
00:29:02,880 --> 00:29:03,200
Speaker 2: Yeah.

659
00:29:03,240 --> 00:29:07,360
Speaker 3: Absolutely, So all of the planets spin to some amount, right,

660
00:29:07,360 --> 00:29:09,400
Speaker 3: That's why we have a day on the Earth. And

661
00:29:10,680 --> 00:29:14,360
Speaker 3: when it spins, a planet doesn't just stay a perfect sphere.

662
00:29:14,360 --> 00:29:16,560
Speaker 3: It kind of gets fatter at the equator than it

663
00:29:16,560 --> 00:29:18,800
Speaker 3: does at the poles. Now, it turns out that how

664
00:29:18,880 --> 00:29:21,360
Speaker 3: fat it gets at the equator versus the poles is

665
00:29:21,400 --> 00:29:24,720
Speaker 3: directly related to what the material properties of the object are. So,

666
00:29:24,760 --> 00:29:26,600
Speaker 3: for example, if you had a perfect water planet, right,

667
00:29:26,680 --> 00:29:28,600
Speaker 3: imagine the small planet made of water and you spun

668
00:29:28,640 --> 00:29:31,720
Speaker 3: it there's a specific like ellipsoidal shape you would get

669
00:29:31,840 --> 00:29:34,560
Speaker 3: for a liquid planet, Whereas if you had a dense

670
00:29:34,640 --> 00:29:37,560
Speaker 3: core inside the planet and with a solid layer and

671
00:29:37,600 --> 00:29:39,800
Speaker 3: then a water ocean on the outside, you're going to

672
00:29:39,800 --> 00:29:42,480
Speaker 3: get a different amount of flattening or a different amount

673
00:29:42,520 --> 00:29:44,960
Speaker 3: of kind of bulging at the equator from that. So

674
00:29:45,000 --> 00:29:47,400
Speaker 3: we can actually use the amount of bulging of these

675
00:29:47,440 --> 00:29:52,000
Speaker 3: planets when they're spinning to get information about what's inside.

676
00:29:52,160 --> 00:29:54,880
Speaker 1: So, for example, you spin a basketball, it stays a sphere,

677
00:29:54,920 --> 00:29:57,160
Speaker 1: but if you spin a blog a pizza dough, it

678
00:29:57,200 --> 00:29:59,840
Speaker 1: becomes a disc, right, and so it tells you pizza

679
00:29:59,840 --> 00:30:02,560
Speaker 1: do softer than basketballs. I guess we already knew that,

680
00:30:02,640 --> 00:30:04,720
Speaker 1: But you're saying we can apply the same thing to planets.

681
00:30:04,920 --> 00:30:07,440
Speaker 1: By the deformation of the sphere, we can tell basically

682
00:30:07,520 --> 00:30:08,480
Speaker 1: how rigid it is.

683
00:30:08,600 --> 00:30:11,200
Speaker 3: Yes, absolutely, and also where the dense, how dense it

684
00:30:11,280 --> 00:30:15,600
Speaker 3: is essentially in different parts. So for example, Saturn, Saturn

685
00:30:15,680 --> 00:30:18,080
Speaker 3: is the bulgiest of all the planets in our solar systems.

686
00:30:18,120 --> 00:30:19,760
Speaker 3: Even if if you look at through a telescope, it

687
00:30:19,760 --> 00:30:22,520
Speaker 3: doesn't look like a sphere, It actually looks like more

688
00:30:22,520 --> 00:30:25,640
Speaker 3: of an oblate spheroid. So it's really interesting to look

689
00:30:25,640 --> 00:30:26,800
Speaker 3: at Saturn through a telescope.

690
00:30:26,920 --> 00:30:29,440
Speaker 1: You mean Saturn looks like squished, like somebody sat on it.

691
00:30:29,560 --> 00:30:31,520
Speaker 2: Yes, Saturn looks like someone satur on it.

692
00:30:31,440 --> 00:30:34,880
Speaker 1: In the best possible way. I mean Saturn's beautiful, Yes, yes, absolutely.

693
00:30:35,160 --> 00:30:37,680
Speaker 3: But because of that, we know that Saturn isn't just

694
00:30:37,880 --> 00:30:40,080
Speaker 3: a ball of hydrogen helium. We know that there have

695
00:30:40,160 --> 00:30:43,479
Speaker 3: to be some rocks inside kind of condensed at the center,

696
00:30:43,640 --> 00:30:45,920
Speaker 3: and then the gas sphere is kind of more on

697
00:30:45,960 --> 00:30:47,640
Speaker 3: the outside of it. So we've actually been able to

698
00:30:47,640 --> 00:30:50,520
Speaker 3: figure that out from the size of its equatorial bulge.

699
00:30:50,640 --> 00:30:52,560
Speaker 2: So that's the first way we can use rotation. There

700
00:30:52,560 --> 00:30:53,160
Speaker 2: are other ways.

701
00:30:53,160 --> 00:30:57,080
Speaker 3: So for example, as planets orbit and rotate, they can

702
00:30:57,400 --> 00:31:00,760
Speaker 3: actually as they're rotating, they don't always point their north

703
00:31:00,800 --> 00:31:04,320
Speaker 3: pole to exactly the same location, so they can actually process,

704
00:31:04,400 --> 00:31:07,840
Speaker 3: so their rotational axis can move around in a circle

705
00:31:08,160 --> 00:31:10,520
Speaker 3: about their orbit axis. And if you've ever played with

706
00:31:10,600 --> 00:31:12,960
Speaker 3: like a top, like a toy top, and you've spun

707
00:31:13,000 --> 00:31:15,760
Speaker 3: it and you've seen it make this little wobbly circlar pattern,

708
00:31:15,840 --> 00:31:18,800
Speaker 3: planets do the same thing. So planetary rotation axis wobble,

709
00:31:18,880 --> 00:31:21,040
Speaker 3: they process, and they also do this thing called nutating

710
00:31:21,120 --> 00:31:24,000
Speaker 3: where they kind of dip down a little bit, and

711
00:31:24,200 --> 00:31:28,000
Speaker 3: the period of those procession motions and the kind of

712
00:31:28,040 --> 00:31:31,760
Speaker 3: how cyclical they are really tells us about the interior

713
00:31:31,800 --> 00:31:32,600
Speaker 3: properties as well.

714
00:31:32,680 --> 00:31:34,280
Speaker 1: But why does it happen in the first place, I mean,

715
00:31:34,400 --> 00:31:37,360
Speaker 1: does an angular momentum tell us that it should we

716
00:31:37,360 --> 00:31:39,760
Speaker 1: spin along the same axis? Is this the effect of

717
00:31:39,840 --> 00:31:41,400
Speaker 1: like other things pulling on it?

718
00:31:41,640 --> 00:31:42,440
Speaker 2: Yes, exactly.

719
00:31:42,560 --> 00:31:45,160
Speaker 3: So if Earth were alone, if it was just the Earth,

720
00:31:45,160 --> 00:31:46,920
Speaker 3: then nothing else was around, we would not have any

721
00:31:47,000 --> 00:31:50,920
Speaker 3: procession or mutation. But we've got the Sun, we've got

722
00:31:50,960 --> 00:31:54,400
Speaker 3: the Moon nearby, and both of those things causecessional motions

723
00:31:54,400 --> 00:31:58,000
Speaker 3: and wobbling nutational motions that affect our orbit in our day.

724
00:31:58,200 --> 00:32:00,680
Speaker 1: So Jupiter and the other things are pulling on the

725
00:32:00,720 --> 00:32:03,960
Speaker 1: Earth and changing the direction of its spin axis basically

726
00:32:04,120 --> 00:32:06,960
Speaker 1: like where the north pole is pointing in the galaxy.

727
00:32:07,640 --> 00:32:10,200
Speaker 1: And you're saying that tells us something about what's inside

728
00:32:10,240 --> 00:32:12,280
Speaker 1: the Earth. People, I think are used to thinking about

729
00:32:12,360 --> 00:32:14,440
Speaker 1: the gravitational model of like, well, you can treat the

730
00:32:14,440 --> 00:32:16,960
Speaker 1: whole planet as a point mass at its center of mass,

731
00:32:17,160 --> 00:32:19,000
Speaker 1: you can't learn anything else about it. So how is

732
00:32:19,040 --> 00:32:21,600
Speaker 1: it possible to know something about the distribution of mass

733
00:32:21,640 --> 00:32:24,280
Speaker 1: inside the planet from how it's spin wobbles.

734
00:32:24,440 --> 00:32:26,960
Speaker 3: So the wobbling and the spin can tell you things,

735
00:32:27,000 --> 00:32:29,080
Speaker 3: for example, like if you have a liquid layer inside

736
00:32:29,080 --> 00:32:30,920
Speaker 3: the planet. So I don't know if you've ever played

737
00:32:30,920 --> 00:32:33,480
Speaker 3: this game, but if you take a beach ball and

738
00:32:33,520 --> 00:32:35,960
Speaker 3: you put like a little pocket of water in it

739
00:32:36,040 --> 00:32:37,680
Speaker 3: and you try to throw it to someone, it moves

740
00:32:37,720 --> 00:32:40,800
Speaker 3: completely differently than if you don't. Or even easier, take

741
00:32:40,840 --> 00:32:44,360
Speaker 3: an egg. Take a raw egg and take a cooked egg,

742
00:32:44,520 --> 00:32:47,200
Speaker 3: both still in their shells, and put them on your counter.

743
00:32:47,000 --> 00:32:49,280
Speaker 2: And spin them, and you will see that they spin.

744
00:32:49,280 --> 00:32:51,760
Speaker 3: Very differently because one of them has liquids inside of

745
00:32:51,760 --> 00:32:54,040
Speaker 3: it and the other one is fully solid. So we

746
00:32:54,080 --> 00:32:58,040
Speaker 3: can use the way that the spin axis wobbles to

747
00:32:58,080 --> 00:33:00,000
Speaker 3: figure out where are there liquid layers in this place?

748
00:33:00,320 --> 00:33:02,880
Speaker 2: Is it fully solid that sort of thing I see?

749
00:33:03,320 --> 00:33:05,600
Speaker 1: Is this planet more like a soft or hard boiled egg.

750
00:33:06,880 --> 00:33:10,120
Speaker 1: That's incredible, And can't you also measure the moment of

751
00:33:10,120 --> 00:33:12,520
Speaker 1: inertia of the planet and tell like where the mass

752
00:33:12,560 --> 00:33:15,080
Speaker 1: is distributed, Like you can tell the difference between like

753
00:33:15,160 --> 00:33:17,360
Speaker 1: all the mass being at the core versus all the

754
00:33:17,400 --> 00:33:18,680
Speaker 1: mass being at the surface.

755
00:33:19,040 --> 00:33:21,200
Speaker 3: Yeah, so it's a bit complicated in the math, but

756
00:33:21,240 --> 00:33:23,880
Speaker 3: it turns out that the precession rate, so how fast

757
00:33:24,280 --> 00:33:27,920
Speaker 3: the axis of the rotation processes about the orbit normal.

758
00:33:27,960 --> 00:33:28,800
Speaker 2: I'll give you any example.

759
00:33:28,840 --> 00:33:31,040
Speaker 3: So on the Earth right now, our north pole points

760
00:33:31,080 --> 00:33:33,040
Speaker 3: to the North Star. It was named lat Way for

761
00:33:33,080 --> 00:33:35,760
Speaker 3: a very specific reason. But it's moving around and in

762
00:33:35,800 --> 00:33:38,520
Speaker 3: about twenty it takes about twenty six thousand years for

763
00:33:38,640 --> 00:33:41,520
Speaker 3: that pole to get back to the North Star. Right,

764
00:33:41,640 --> 00:33:45,360
Speaker 3: So the period of our orbit is twenty six thousand years,

765
00:33:45,800 --> 00:33:49,760
Speaker 3: and that period can be used to actually determine the

766
00:33:49,800 --> 00:33:53,640
Speaker 3: moment of inertia of the Earth through some fancy math formulas.

767
00:33:53,960 --> 00:33:56,840
Speaker 3: And so if we can measure the precession rate or

768
00:33:56,880 --> 00:33:59,440
Speaker 3: the period for other planetary bodies, we can also figure

769
00:33:59,440 --> 00:34:00,640
Speaker 3: out their moment of inertia.

770
00:34:00,920 --> 00:34:04,120
Speaker 1: Wow, twenty six thousand years. How long have we been

771
00:34:04,160 --> 00:34:06,680
Speaker 1: making these measurements? Couldn't have been more than a thousand

772
00:34:06,800 --> 00:34:07,680
Speaker 1: years that maximum?

773
00:34:07,760 --> 00:34:10,239
Speaker 3: Yeah, yeah, it's definitely less than that. But you know,

774
00:34:10,280 --> 00:34:11,840
Speaker 3: you can you can trace out a little arc of

775
00:34:11,880 --> 00:34:13,640
Speaker 3: a circle, then you can pretty much draw out the

776
00:34:13,680 --> 00:34:14,400
Speaker 3: rest of the circle.

777
00:34:14,600 --> 00:34:16,080
Speaker 1: Yeah, I guess we have a model and we can

778
00:34:16,120 --> 00:34:19,279
Speaker 1: fit to that little arc. That's amazing, incredible. We can

779
00:34:19,360 --> 00:34:22,600
Speaker 1: learn so much about what's inside these objects without even

780
00:34:22,680 --> 00:34:25,160
Speaker 1: ever going inside. All right, I can't wait to talk

781
00:34:25,160 --> 00:34:27,040
Speaker 1: about this some more, but first we have to take

782
00:34:27,160 --> 00:34:42,840
Speaker 1: another break. Okay, we're back and we're talking to Professor

783
00:34:42,880 --> 00:34:46,280
Speaker 1: Sabina Stanley, author of the new book What's Hidden Inside

784
00:34:46,280 --> 00:34:49,600
Speaker 1: Planets about what's inside the Earth and other planets. Now,

785
00:34:49,600 --> 00:34:51,800
Speaker 1: I want to talk about sort of how the inside

786
00:34:51,840 --> 00:34:55,520
Speaker 1: affects the outside, because obviously, if you're just curious about

787
00:34:55,520 --> 00:34:57,200
Speaker 1: how the solar system is formed, you want to know,

788
00:34:57,239 --> 00:35:00,000
Speaker 1: like what's inside the Earth. But even if you're not,

789
00:35:00,239 --> 00:35:03,359
Speaker 1: like it has an effect on living on the surface, right,

790
00:35:03,600 --> 00:35:06,640
Speaker 1: tell us about how the magnetic field of these things

791
00:35:06,680 --> 00:35:09,200
Speaker 1: is generated and how it relates to bubbling soup.

792
00:35:09,480 --> 00:35:12,600
Speaker 2: Yeah, so magnetic fields are my favorite topic. Not gonna lie.

793
00:35:12,840 --> 00:35:14,200
Speaker 2: So here's this amazing thing. Right.

794
00:35:14,239 --> 00:35:16,120
Speaker 3: We're on the surface of the Earth, and one of

795
00:35:16,120 --> 00:35:18,239
Speaker 3: the reasons it's such a nice place to live at

796
00:35:18,239 --> 00:35:21,160
Speaker 3: the moment is because we have this beautiful magnetic field

797
00:35:21,160 --> 00:35:24,480
Speaker 3: that completely envelops the Earth. And that magnetic field what

798
00:35:24,520 --> 00:35:27,040
Speaker 3: it does for us is it shields the surface from

799
00:35:27,120 --> 00:35:29,439
Speaker 3: high energy particles that come from the solar wind, which

800
00:35:29,480 --> 00:35:31,640
Speaker 3: come from the Sun and from cosmic rays that come

801
00:35:31,640 --> 00:35:34,879
Speaker 3: from deep space, and those very high energy particles. If

802
00:35:35,000 --> 00:35:37,120
Speaker 3: we didn't have our magnetic field, they would kind of

803
00:35:37,120 --> 00:35:39,279
Speaker 3: blast the surface of the Earth and they would do

804
00:35:39,360 --> 00:35:41,520
Speaker 3: some terrible things. First of all, they would cause high

805
00:35:41,560 --> 00:35:44,640
Speaker 3: radiation environments, so we'd likely have higher rates of cancer,

806
00:35:44,719 --> 00:35:49,080
Speaker 3: for example. But also they cause lots of electrical disturbances.

807
00:35:49,120 --> 00:35:51,200
Speaker 3: And if you think about our power grid, our power

808
00:35:51,239 --> 00:35:53,680
Speaker 3: grid does not like there to be large fluctuations in

809
00:35:53,800 --> 00:35:54,960
Speaker 3: electromagnetic fields.

810
00:35:55,080 --> 00:35:57,439
Speaker 2: That's another thing that is not so good.

811
00:35:57,640 --> 00:36:02,280
Speaker 3: It also tends to these solar winds that bombard planets.

812
00:36:02,560 --> 00:36:05,600
Speaker 3: They can actually erode the atmosphere of a planet, so

813
00:36:05,640 --> 00:36:07,840
Speaker 3: they can take they can basically, you know, it's like

814
00:36:07,920 --> 00:36:10,040
Speaker 3: pointing a hair dryer at the Earth. You're going to

815
00:36:10,080 --> 00:36:11,719
Speaker 3: be able to blow off all the gas from it.

816
00:36:12,000 --> 00:36:13,799
Speaker 3: So there are all these things that the magnetic field

817
00:36:13,800 --> 00:36:16,840
Speaker 3: actually shields us from. But this magnetic field that surrounds

818
00:36:16,920 --> 00:36:19,960
Speaker 3: us is actually created deep inside the Earth in the

819
00:36:20,000 --> 00:36:24,520
Speaker 3: iron core. So iron is great electrical conductor. When you

820
00:36:24,520 --> 00:36:26,560
Speaker 3: have a great electrical conductor, if you can get it

821
00:36:26,600 --> 00:36:29,560
Speaker 3: moving around in the right way, then you can actually

822
00:36:29,640 --> 00:36:33,239
Speaker 3: generate magnetic fields And the best kind of analogy I

823
00:36:33,239 --> 00:36:34,880
Speaker 3: can think of for this is if anyone has a

824
00:36:34,880 --> 00:36:38,400
Speaker 3: home generator or if they have a bike light that

825
00:36:38,440 --> 00:36:41,360
Speaker 3: they can pedal to get going, you're basically converting the

826
00:36:41,440 --> 00:36:44,800
Speaker 3: kinetic energy of that motion into electromagnetic energy.

827
00:36:44,880 --> 00:36:45,879
Speaker 2: So you either you know.

828
00:36:45,840 --> 00:36:48,960
Speaker 3: You're pedaling, causes your bike light causes currents to flow

829
00:36:49,280 --> 00:36:52,120
Speaker 3: that causes your bike light to shine right, or similar

830
00:36:52,120 --> 00:36:55,160
Speaker 3: in your generator. So in the core of the earth,

831
00:36:55,560 --> 00:36:59,440
Speaker 3: convection which occurs because the center is hotter than the

832
00:36:59,440 --> 00:37:01,520
Speaker 3: outer parts of the core, So you kind of have

833
00:37:01,560 --> 00:37:03,360
Speaker 3: bubbling up like like you would if you put a

834
00:37:03,360 --> 00:37:05,759
Speaker 3: pot of soup on the stove, right, you get the

835
00:37:05,840 --> 00:37:07,759
Speaker 3: bottom of the pot is hot, the top of the

836
00:37:07,760 --> 00:37:11,040
Speaker 3: pot is cold, So you get these overturning motions in

837
00:37:11,080 --> 00:37:14,080
Speaker 3: the soup. Same thing happens in the core, and so

838
00:37:14,160 --> 00:37:17,759
Speaker 3: that overturning motions they create magnetic fields and you get

839
00:37:17,760 --> 00:37:20,399
Speaker 3: what called a dynamo. So the dynamo in the center

840
00:37:20,400 --> 00:37:22,719
Speaker 3: of the earth generates this magnetic field that protects us

841
00:37:22,800 --> 00:37:23,400
Speaker 3: on the surface.

842
00:37:23,600 --> 00:37:27,080
Speaker 1: Amazing, And so you're saying that it's the convection cells

843
00:37:27,280 --> 00:37:30,320
Speaker 1: that generate the magnetic field, not for example, the spinning

844
00:37:30,360 --> 00:37:30,920
Speaker 1: of the planet.

845
00:37:31,320 --> 00:37:36,560
Speaker 3: Right, So there's a somewhat common misunderstanding out there that

846
00:37:36,680 --> 00:37:38,720
Speaker 3: the reason that Earth has a magnetic field, for example,

847
00:37:38,760 --> 00:37:41,560
Speaker 3: is due to its spinning. And this has been used sometimes,

848
00:37:41,560 --> 00:37:45,160
Speaker 3: for example, to explain why Venus, which is spinning very slowly,

849
00:37:45,600 --> 00:37:46,920
Speaker 3: doesn't have a magnetic field.

850
00:37:47,040 --> 00:37:47,880
Speaker 2: And it turns out.

851
00:37:47,719 --> 00:37:50,600
Speaker 3: That you don't need spinning at all to generate a

852
00:37:50,640 --> 00:37:53,800
Speaker 3: magnetic field. So magnetic fields can be generated through dynamo

853
00:37:53,840 --> 00:37:58,800
Speaker 3: processes without spinning. Now, spinning sometimes helps in organizing motions

854
00:37:58,800 --> 00:38:01,200
Speaker 3: and stuff like that, but it's not actually a requirement.

855
00:38:01,400 --> 00:38:03,759
Speaker 3: So it's the convective motions, not the spinning, right.

856
00:38:03,920 --> 00:38:06,400
Speaker 1: And so in your analogy, you're talking about like peddling

857
00:38:06,640 --> 00:38:09,879
Speaker 1: your bicycle to generate electricity, And we haven't seen any

858
00:38:09,920 --> 00:38:12,680
Speaker 1: magnetic monopoles in our universe, so we know that to

859
00:38:12,760 --> 00:38:15,120
Speaker 1: generate magnetic fields you have to take a charge and

860
00:38:15,200 --> 00:38:18,239
Speaker 1: put it in motion, which is how electrical generators work.

861
00:38:18,320 --> 00:38:21,680
Speaker 1: But what is the charge here? Like we have flows

862
00:38:21,719 --> 00:38:24,560
Speaker 1: of iron. Iron is obviously metallic and it conducts, but

863
00:38:24,800 --> 00:38:27,560
Speaker 1: don't you need some ion in motion in order to

864
00:38:27,560 --> 00:38:30,000
Speaker 1: get a current going? What generates the actual current? If

865
00:38:30,040 --> 00:38:32,520
Speaker 1: you just have neutral iron how does that generate a

866
00:38:32,560 --> 00:38:33,280
Speaker 1: magnetic field.

867
00:38:33,480 --> 00:38:36,319
Speaker 3: Yeah, it's actually an induction process. So what it is

868
00:38:36,320 --> 00:38:39,319
Speaker 3: is you've got a good electrical conductor and imagine you

869
00:38:39,400 --> 00:38:42,359
Speaker 3: have a magnetic field and it's frozen into a good

870
00:38:42,360 --> 00:38:46,720
Speaker 3: electrical conductor. So magnetic fields tend to stick inside good conductors.

871
00:38:46,719 --> 00:38:48,600
Speaker 2: They don't like to change. But imagine then that.

872
00:38:48,560 --> 00:38:51,640
Speaker 3: You start moving that conductor around relative to itself, so

873
00:38:51,680 --> 00:38:53,480
Speaker 3: you shear it, you pull it apart a little bit.

874
00:38:53,640 --> 00:38:56,000
Speaker 3: That magnetic field has to go with it, so you

875
00:38:56,080 --> 00:38:59,320
Speaker 3: stretch and twist the magnetic fields through the motion itself

876
00:38:59,560 --> 00:39:01,080
Speaker 3: to create new magnetic fields.

877
00:39:01,160 --> 00:39:05,760
Speaker 1: Wow. Fascinating. And the Earth's magnetic field, though it's pretty reliable,

878
00:39:05,840 --> 00:39:08,200
Speaker 1: is not actually constant. Isn't it gradually changing?

879
00:39:08,400 --> 00:39:08,600
Speaker 2: Yes?

880
00:39:08,680 --> 00:39:12,560
Speaker 3: Absolutely, So we have records from the rocks in our crust.

881
00:39:12,680 --> 00:39:15,440
Speaker 3: They can be magnetized at the time that they form,

882
00:39:15,960 --> 00:39:19,279
Speaker 3: and those records tell us that Earth's magnetic field has

883
00:39:19,360 --> 00:39:21,680
Speaker 3: changed over time. We at least have data that shows

884
00:39:21,719 --> 00:39:24,520
Speaker 3: it's been around for about three billion years, if not longer.

885
00:39:25,360 --> 00:39:27,160
Speaker 3: But it hasn't always been the same. So there are

886
00:39:27,200 --> 00:39:29,160
Speaker 3: times in the past where the field has gotten weaker.

887
00:39:29,200 --> 00:39:31,520
Speaker 3: There are times in the past where the field has

888
00:39:31,600 --> 00:39:34,399
Speaker 3: flipped polarity, so the north magnetic pole became the south

889
00:39:34,480 --> 00:39:38,120
Speaker 3: magnetic pole and vice versa. And even today, on like

890
00:39:38,719 --> 00:39:41,920
Speaker 3: weekly time scales, we can measure the small changes in

891
00:39:41,920 --> 00:39:44,280
Speaker 3: the earth magnetic field that are happening from a variety

892
00:39:44,320 --> 00:39:46,560
Speaker 3: of things. Some things are external, but sometimes we can

893
00:39:46,600 --> 00:39:49,200
Speaker 3: also see on a yearly scale we can see the

894
00:39:49,280 --> 00:39:51,920
Speaker 3: changes due to different flows happening in the core of

895
00:39:51,920 --> 00:39:52,320
Speaker 3: the Earth.

896
00:39:52,520 --> 00:39:54,719
Speaker 1: Can we use these changes in the magnetic field to

897
00:39:54,719 --> 00:39:57,040
Speaker 1: sort of image those flows the same way we can

898
00:39:57,280 --> 00:39:59,640
Speaker 1: see changes in the gravitational field to give us a

899
00:39:59,640 --> 00:40:00,919
Speaker 1: picture of what's inside the Earth.

900
00:40:01,000 --> 00:40:04,000
Speaker 3: Yeah, it gets a little more challenging the deeper you go.

901
00:40:04,200 --> 00:40:06,640
Speaker 3: And with magnetic fields, what we can see, for example,

902
00:40:06,800 --> 00:40:09,040
Speaker 3: is because we know it's a good electrical conductor, if

903
00:40:09,040 --> 00:40:11,520
Speaker 3: we see a magnetic field pattern drifting.

904
00:40:11,120 --> 00:40:11,800
Speaker 2: In one direction.

905
00:40:12,120 --> 00:40:14,360
Speaker 3: So for example, there's this kind of famous thing we

906
00:40:14,400 --> 00:40:17,680
Speaker 3: talk about in geomagnetism called the westward drift. So if

907
00:40:17,719 --> 00:40:19,759
Speaker 3: you follow certain features of the magnetic field, you see

908
00:40:19,760 --> 00:40:22,440
Speaker 3: they all kind of drift westward, and we interpret that

909
00:40:22,480 --> 00:40:25,080
Speaker 3: to being there's flow generally in the westward direction.

910
00:40:25,120 --> 00:40:26,000
Speaker 2: There's like a jet.

911
00:40:25,760 --> 00:40:29,280
Speaker 3: Stream in the core of the Earth. That's flowing westward,

912
00:40:29,800 --> 00:40:31,359
Speaker 3: that's taking the magnetic field with us.

913
00:40:31,400 --> 00:40:34,240
Speaker 1: Wow, and so how well do we understand this process?

914
00:40:34,280 --> 00:40:37,280
Speaker 1: Are there still open questions about like why it's flipping

915
00:40:37,360 --> 00:40:39,320
Speaker 1: and why it's changing or is it something that we

916
00:40:39,440 --> 00:40:40,359
Speaker 1: understand pretty well?

917
00:40:40,520 --> 00:40:44,040
Speaker 3: So many open questions. So the amazing thing about this process,

918
00:40:44,080 --> 00:40:46,840
Speaker 3: so fluid dynamics. If you've had any experience with climate

919
00:40:46,880 --> 00:40:50,200
Speaker 3: modeling or trying to study flows that happen in pipes

920
00:40:50,239 --> 00:40:54,279
Speaker 3: and so forth, fluids are really complicated. They can they

921
00:40:54,320 --> 00:40:58,120
Speaker 3: can display turbulence for example, or laminar flows depending on

922
00:40:58,160 --> 00:41:01,640
Speaker 3: what types of you know, what what the situation is like.

923
00:41:02,320 --> 00:41:03,720
Speaker 2: Now, if you add to that.

924
00:41:04,200 --> 00:41:06,799
Speaker 3: Add to fluid dynamics magnetic fields and all the things

925
00:41:06,800 --> 00:41:09,759
Speaker 3: that happen with magnetic fields, you almost get an added complication.

926
00:41:10,560 --> 00:41:12,239
Speaker 3: And so when we try to think about, well, how

927
00:41:12,280 --> 00:41:14,680
Speaker 3: do we study the dynamo process, right, we can't really

928
00:41:14,719 --> 00:41:18,000
Speaker 3: wait thousands of years to watch the real system over time.

929
00:41:18,000 --> 00:41:20,200
Speaker 3: We want to study it faster. So you can either

930
00:41:20,239 --> 00:41:23,240
Speaker 3: do experiments or you can try to write a computer

931
00:41:23,320 --> 00:41:26,280
Speaker 3: model that can mimic what's going on in a core

932
00:41:26,360 --> 00:41:29,800
Speaker 3: when it's generating a magnetic field. Experiments are really hard

933
00:41:29,960 --> 00:41:33,880
Speaker 3: turns out that dynamos they like three things. They like

934
00:41:34,040 --> 00:41:37,480
Speaker 3: really good electrical conductors, they like really fast motions, and

935
00:41:37,520 --> 00:41:40,520
Speaker 3: they like really large length scales. And then you start saying, Okay,

936
00:41:40,560 --> 00:41:44,520
Speaker 3: I'm going to build my giant sphere of a really

937
00:41:44,520 --> 00:41:46,960
Speaker 3: good electrical conductor and then spin it really fast, and

938
00:41:47,000 --> 00:41:49,880
Speaker 3: you just you end up with a huge challenging problem.

939
00:41:49,880 --> 00:41:52,879
Speaker 3: The biggest dynamo experiment out there is the three meter

940
00:41:53,120 --> 00:41:56,600
Speaker 3: Dynamo Sphere in Maryland, and it has yet to generate

941
00:41:56,760 --> 00:42:00,640
Speaker 3: an active dynamo, so that's a challenging problem. We use

942
00:42:00,640 --> 00:42:04,160
Speaker 3: computer simulations to study dynamos inside planets. The problem there

943
00:42:04,840 --> 00:42:07,880
Speaker 3: is that planets, the motions, the scales, and the motions

944
00:42:07,880 --> 00:42:10,719
Speaker 3: are so tiny and so fast that there isn't enough

945
00:42:10,719 --> 00:42:13,719
Speaker 3: computer power on the planet to run a simulation accurately.

946
00:42:13,960 --> 00:42:15,920
Speaker 3: So we have to make a lot of assumptions and

947
00:42:16,000 --> 00:42:19,880
Speaker 3: simplifying type conditions, so we aren't able to fully study

948
00:42:19,880 --> 00:42:20,720
Speaker 3: the system the way.

949
00:42:20,560 --> 00:42:22,960
Speaker 2: We want to. We have to be very nuanced in

950
00:42:23,000 --> 00:42:23,920
Speaker 2: how we study it. Well.

951
00:42:23,960 --> 00:42:27,160
Speaker 1: Do we understand why the Earth's flipping of the magnetic

952
00:42:27,200 --> 00:42:29,839
Speaker 1: field seems so irregular compared to, for example, the Sun,

953
00:42:29,880 --> 00:42:32,760
Speaker 1: which has this rock solid solar cycle of eleven years.

954
00:42:32,920 --> 00:42:35,560
Speaker 3: Yeah, we don't fully understand why at all. We can't

955
00:42:35,600 --> 00:42:37,799
Speaker 3: even kind of predict what we would expect for other

956
00:42:37,840 --> 00:42:39,680
Speaker 3: planets as well. We have what I would call a

957
00:42:39,719 --> 00:42:42,759
Speaker 3: hand way the understanding, and that we would describe the

958
00:42:42,760 --> 00:42:46,480
Speaker 3: core fluid as being a very nonlinear system that can

959
00:42:46,560 --> 00:42:51,120
Speaker 3: have different attractors or different stable systems. And sometimes it's

960
00:42:51,160 --> 00:42:53,640
Speaker 3: in one stable position, sometimes it's another. And so if

961
00:42:53,640 --> 00:42:55,759
Speaker 3: you have something near a stable position, imagine you have

962
00:42:55,800 --> 00:42:59,480
Speaker 3: a ball sitting and you have like a nice valley

963
00:42:59,480 --> 00:43:01,239
Speaker 3: in two hill on the side, and you stick the

964
00:43:01,280 --> 00:43:03,600
Speaker 3: ball on one of the tops of the hills, right,

965
00:43:03,640 --> 00:43:05,759
Speaker 3: it'll pretty much stay there, but maybe if you shake

966
00:43:05,800 --> 00:43:07,279
Speaker 3: it a little bit too much, give it a bit

967
00:43:07,280 --> 00:43:10,040
Speaker 3: too many perturbations, it'll sink down and go to the

968
00:43:10,040 --> 00:43:13,600
Speaker 3: other stable position. So we think that some perturbations in

969
00:43:13,640 --> 00:43:16,440
Speaker 3: the fluid can sometimes cause the field of flip, but

970
00:43:16,560 --> 00:43:18,360
Speaker 3: we don't have a good way to, for example, predict

971
00:43:18,440 --> 00:43:20,440
Speaker 3: when the next flip is going to happen, what's the

972
00:43:20,719 --> 00:43:23,280
Speaker 3: key factor that causes such a flip for example?

973
00:43:23,280 --> 00:43:24,800
Speaker 2: And these are all areas of current research.

974
00:43:24,920 --> 00:43:29,440
Speaker 1: Wow. And then as we discover planets in other solar systems.

975
00:43:29,719 --> 00:43:33,160
Speaker 1: How do we begin to do geology of those planets?

976
00:43:33,200 --> 00:43:35,520
Speaker 1: And first, I guess there's a trivial question is would

977
00:43:35,560 --> 00:43:37,719
Speaker 1: you call it geology? Geology is to study the Earth,

978
00:43:37,800 --> 00:43:40,120
Speaker 1: so it is this like exo planetology, what do you

979
00:43:40,120 --> 00:43:40,480
Speaker 1: call it?

980
00:43:40,640 --> 00:43:41,880
Speaker 2: This is a great question.

981
00:43:42,000 --> 00:43:44,839
Speaker 3: I think the norm has been to refer to geology

982
00:43:44,920 --> 00:43:46,600
Speaker 3: as looking at rocks.

983
00:43:46,320 --> 00:43:48,480
Speaker 2: And it doesn't matter where those rocks are. So rocks.

984
00:43:48,640 --> 00:43:51,080
Speaker 3: There are Mars geologists, I'll just get that out there,

985
00:43:51,080 --> 00:43:54,800
Speaker 3: instead of mars oologists or whatever you would call them instead. Yeah,

986
00:43:54,800 --> 00:43:58,520
Speaker 3: with exoplanets, the challenge there is the type of information

987
00:43:58,600 --> 00:44:00,920
Speaker 3: you can get can be quite limitted compared to what

988
00:44:00,920 --> 00:44:03,160
Speaker 3: we can get when we're in our own Solar system

989
00:44:03,239 --> 00:44:05,760
Speaker 3: or here on the Earth. But even with the standard

990
00:44:05,760 --> 00:44:09,880
Speaker 3: techniques that can discover exoplanets, right, if you think about

991
00:44:10,080 --> 00:44:13,400
Speaker 3: the methods involving radial velocity detection, so where you measure

992
00:44:13,480 --> 00:44:17,040
Speaker 3: fluctuations in the stars light curve caused by the motion

993
00:44:17,200 --> 00:44:19,400
Speaker 3: of a planet around it, you get information about the

994
00:44:19,400 --> 00:44:21,719
Speaker 3: period of the orbit, and that can also give you

995
00:44:21,960 --> 00:44:24,840
Speaker 3: measurements about the mass of the planet. Then if you

996
00:44:24,960 --> 00:44:27,560
Speaker 3: use transit where a planet passes in front of or

997
00:44:27,560 --> 00:44:30,160
Speaker 3: behind a star, you can get information about the size

998
00:44:30,200 --> 00:44:31,799
Speaker 3: of the planet. So as soon as you have the

999
00:44:31,840 --> 00:44:33,600
Speaker 3: size and the mass, you already have kind of an

1000
00:44:33,640 --> 00:44:36,600
Speaker 3: average density, a bulk density of the planet. So we

1001
00:44:36,680 --> 00:44:40,080
Speaker 3: have sense of whether when we discover these exoplanets, is

1002
00:44:40,120 --> 00:44:43,400
Speaker 3: it a gas giant, is it an Earth like planet?

1003
00:44:43,560 --> 00:44:45,799
Speaker 3: Is it an ice world like Uranus and Neptune. So

1004
00:44:45,840 --> 00:44:49,600
Speaker 3: we can do some very broad geology, let's say, from

1005
00:44:49,640 --> 00:44:52,720
Speaker 3: that type of information. But what I'm most excited about

1006
00:44:52,920 --> 00:44:55,279
Speaker 3: is the possibilities that are going to come forward with

1007
00:44:55,400 --> 00:44:59,799
Speaker 3: JWST because this new telescope is going to be able

1008
00:44:59,840 --> 00:45:04,759
Speaker 3: to measure the atmospheres of exoplanets and tell us what

1009
00:45:04,760 --> 00:45:07,440
Speaker 3: they're made of. That's going to be crucial information to

1010
00:45:07,480 --> 00:45:10,320
Speaker 3: figure out what's actually going on deeper inside the planet.

1011
00:45:10,400 --> 00:45:13,080
Speaker 3: Right our atmosphere on Earth is the way it is

1012
00:45:13,160 --> 00:45:15,799
Speaker 3: because of interactions with the interior of the Earth, and

1013
00:45:15,880 --> 00:45:17,640
Speaker 3: so we're going to be able to use information about

1014
00:45:17,640 --> 00:45:20,120
Speaker 3: the atmospheres of these exoplanets to also tell us something

1015
00:45:20,120 --> 00:45:21,040
Speaker 3: about the interior.

1016
00:45:21,080 --> 00:45:23,040
Speaker 1: What do you mean by that? I know our atmosphere

1017
00:45:23,160 --> 00:45:25,680
Speaker 1: is different because we have a magnetic field and because

1018
00:45:25,680 --> 00:45:29,040
Speaker 1: of the surface gravity. What else does our atmosphere tell

1019
00:45:29,120 --> 00:45:30,480
Speaker 1: us about what's inside the Earth.

1020
00:45:30,640 --> 00:45:33,600
Speaker 3: Right, So if there was an alien flying by our

1021
00:45:33,600 --> 00:45:36,080
Speaker 3: solar system, and all it could measure is kind of

1022
00:45:36,080 --> 00:45:38,400
Speaker 3: the spectrum of our atmosphere, it would be able to

1023
00:45:38,400 --> 00:45:40,200
Speaker 3: tell that there was life here most likely.

1024
00:45:40,280 --> 00:45:40,440
Speaker 2: Right.

1025
00:45:40,480 --> 00:45:43,120
Speaker 3: We've done things to our environment to make it very

1026
00:45:43,200 --> 00:45:46,920
Speaker 3: obvious that there is industrial action happening on the surface.

1027
00:45:47,080 --> 00:45:47,279
Speaker 2: Right.

1028
00:45:47,360 --> 00:45:50,560
Speaker 3: But also, for example, a lot of the processes that

1029
00:45:50,719 --> 00:45:53,840
Speaker 3: regulate some of the key species in our atmospheres, like

1030
00:45:53,880 --> 00:45:58,080
Speaker 3: carbon dioxide. On Earth, there's the carbon cycle. The carbon

1031
00:45:58,200 --> 00:46:01,360
Speaker 3: cycle not only involves the atmosphere, it involves the ocean,

1032
00:46:01,680 --> 00:46:05,440
Speaker 3: the surface, and the deep interior. So carbon gets recycled

1033
00:46:05,840 --> 00:46:09,040
Speaker 3: inside the Earth, and so we can actually learn about

1034
00:46:09,160 --> 00:46:12,440
Speaker 3: how exchanges of materials happen with the interior and the

1035
00:46:12,480 --> 00:46:15,280
Speaker 3: atmosphere by looking at how much carbon there is around,

1036
00:46:15,280 --> 00:46:17,360
Speaker 3: for example, right. And so the same is true for

1037
00:46:17,480 --> 00:46:20,480
Speaker 3: other element cycles, and so the same could be true

1038
00:46:20,480 --> 00:46:21,279
Speaker 3: for exoplanets.

1039
00:46:21,400 --> 00:46:24,520
Speaker 1: We had Professor Shields on the podcast recently, and she

1040
00:46:24,640 --> 00:46:29,160
Speaker 1: does exoplanet climate simulations. We're basically building models of these

1041
00:46:29,200 --> 00:46:31,960
Speaker 1: planets and then trying to make them consistent with what

1042
00:46:32,000 --> 00:46:34,799
Speaker 1: we might understand from JWST. It sounds like you're talking

1043
00:46:34,840 --> 00:46:37,279
Speaker 1: about doing something similar, but you're building models of the

1044
00:46:37,320 --> 00:46:40,480
Speaker 1: internals of these planets to explain then the climate in

1045
00:46:40,520 --> 00:46:43,120
Speaker 1: the atmosphere, which then tells us about the light we're

1046
00:46:43,120 --> 00:46:45,120
Speaker 1: seeing from these planets. So it seems like quite a

1047
00:46:45,120 --> 00:46:48,160
Speaker 1: few steps there from the photons we're getting in JWST

1048
00:46:48,520 --> 00:46:51,520
Speaker 1: to our model of what's happening inside those planets. Incredible

1049
00:46:51,520 --> 00:46:52,200
Speaker 1: that we could learn.

1050
00:46:52,080 --> 00:46:53,640
Speaker 2: Anything, Yes, absolutely agree.

1051
00:46:53,800 --> 00:46:56,240
Speaker 1: And what about future missions? I know there are space

1052
00:46:56,280 --> 00:46:58,840
Speaker 1: telescopes that are going to be looking specifically for planets.

1053
00:46:58,880 --> 00:47:01,000
Speaker 1: Are those going to have the toy to tell us

1054
00:47:01,080 --> 00:47:03,319
Speaker 1: more about these planets or do we need to wait

1055
00:47:03,400 --> 00:47:07,760
Speaker 1: until we can send landers to listen for exoplanet quakes.

1056
00:47:07,840 --> 00:47:12,040
Speaker 3: What I'm most excited about for future exoplanet data has

1057
00:47:12,080 --> 00:47:14,239
Speaker 3: to do with magnetic fields again, right, So if we

1058
00:47:14,320 --> 00:47:17,640
Speaker 3: think Earth having a magnetic field is so important for

1059
00:47:17,719 --> 00:47:20,239
Speaker 3: shielding life on the surface, then it might be nice

1060
00:47:20,280 --> 00:47:22,960
Speaker 3: if we knew that exoplanets had magnetic fields. It maybe

1061
00:47:22,960 --> 00:47:25,880
Speaker 3: it's something we should add to the conditions for a habitable.

1062
00:47:25,520 --> 00:47:26,320
Speaker 2: Planet out there.

1063
00:47:26,640 --> 00:47:28,960
Speaker 3: And there have been some signs, some evidence that we

1064
00:47:29,040 --> 00:47:31,760
Speaker 3: might actually be able to measure magnetic fields of exoplanets

1065
00:47:31,960 --> 00:47:35,600
Speaker 3: so there's hope that with even more measurements and so forth,

1066
00:47:35,960 --> 00:47:38,400
Speaker 3: we might actually be able to tell in the future

1067
00:47:38,440 --> 00:47:40,440
Speaker 3: if an exoplanet has a magnetic field.

1068
00:47:40,200 --> 00:47:42,239
Speaker 1: Today, how would that be possible? Are you looking for

1069
00:47:42,320 --> 00:47:45,360
Speaker 1: like the Northern lights equivalent on the planet, seeing the

1070
00:47:45,360 --> 00:47:47,319
Speaker 1: effect of the magnetic field on the atmosphere.

1071
00:47:47,360 --> 00:47:49,200
Speaker 3: So that's one way kind of so it's not the

1072
00:47:49,239 --> 00:47:52,200
Speaker 3: Northern lights itself, but actually the way we found out

1073
00:47:52,280 --> 00:47:54,120
Speaker 3: Jupiter had a magnetic field. We knew that Jupiter had

1074
00:47:54,120 --> 00:47:56,239
Speaker 3: a magnet field in the nineteen sixties even though we'd

1075
00:47:56,239 --> 00:48:00,719
Speaker 3: never been there, because electrons that spire roll along the

1076
00:48:00,760 --> 00:48:03,480
Speaker 3: magnetic field lines of Jupiter get really close to the

1077
00:48:03,520 --> 00:48:06,080
Speaker 3: poles into the atmosphere there right, and that causes aurora

1078
00:48:06,120 --> 00:48:08,800
Speaker 3: on Jupiter as well. But it also causes a type

1079
00:48:08,880 --> 00:48:12,040
Speaker 3: of radio emissions to come off of Jupiter, and those

1080
00:48:12,160 --> 00:48:14,480
Speaker 3: radio emissions get beamed out into space and we could

1081
00:48:14,480 --> 00:48:16,359
Speaker 3: actually measure them here on the surface of the Earth.

1082
00:48:16,560 --> 00:48:18,840
Speaker 3: So we knew about Jupiter's magnetic field in the nineteen

1083
00:48:18,880 --> 00:48:21,200
Speaker 3: sixties before we'd ever gone there, because we received these

1084
00:48:21,280 --> 00:48:25,000
Speaker 3: radio emissions. Same is true for any other planet. Now,

1085
00:48:25,000 --> 00:48:27,720
Speaker 3: it turns out that the intensity of those radio emissions

1086
00:48:27,760 --> 00:48:30,040
Speaker 3: is really important, so you need really strong magnetic fields

1087
00:48:30,040 --> 00:48:31,360
Speaker 3: in order to be able to measure them. On the

1088
00:48:31,360 --> 00:48:33,680
Speaker 3: surface of the Earth. We have this horrible atmosphere on

1089
00:48:33,719 --> 00:48:35,799
Speaker 3: Earth and it blocks a lot of radio emissions, which

1090
00:48:35,840 --> 00:48:38,400
Speaker 3: is very frustrating, although kind of good for breathing. So

1091
00:48:38,520 --> 00:48:43,520
Speaker 3: I guess, you know, let's say we put a radio

1092
00:48:43,520 --> 00:48:46,120
Speaker 3: telescope on the far side of the Moon. That would

1093
00:48:46,120 --> 00:48:49,320
Speaker 3: be great for helping to detect radio emissions from exoplanets.

1094
00:48:49,640 --> 00:48:52,319
Speaker 3: So there's that method, but they're also what I would

1095
00:48:52,360 --> 00:48:53,560
Speaker 3: call sneakier methods.

1096
00:48:53,640 --> 00:48:53,839
Speaker 2: Right.

1097
00:48:54,120 --> 00:48:57,880
Speaker 3: For example, if you look at the transit spectrum, so

1098
00:48:57,880 --> 00:48:59,600
Speaker 3: if you look at a planet that's going in front

1099
00:48:59,600 --> 00:49:03,440
Speaker 3: of a sign or a star and you see kind

1100
00:49:03,480 --> 00:49:06,000
Speaker 3: of how wide the planet is. People can already kind

1101
00:49:06,000 --> 00:49:08,440
Speaker 3: of tell if a planet has an atmosphere by the

1102
00:49:08,480 --> 00:49:11,600
Speaker 3: fact that it could have different thicknesses or different radius

1103
00:49:11,640 --> 00:49:14,920
Speaker 3: in different wavelengths, and that you know, sometimes the atmosphere

1104
00:49:14,960 --> 00:49:18,239
Speaker 3: will let light through, whereas the planet itself won't, right,

1105
00:49:18,320 --> 00:49:20,279
Speaker 3: And so that's how we can tell whether something has

1106
00:49:20,320 --> 00:49:23,239
Speaker 3: an atmosphere, is what particular wavelengths of light get through

1107
00:49:23,239 --> 00:49:25,560
Speaker 3: at different distances. The same can be true about a

1108
00:49:25,560 --> 00:49:28,479
Speaker 3: magnetic field. Sometimes a magnetic field can cause certain light

1109
00:49:28,600 --> 00:49:31,279
Speaker 3: spectra light frequencies to not get through, so we might

1110
00:49:31,320 --> 00:49:35,480
Speaker 3: be actually able to measure a magnetosphere surrounding a planet

1111
00:49:36,160 --> 00:49:39,279
Speaker 3: by looking at transit spectra. You can also maybe see

1112
00:49:39,320 --> 00:49:41,960
Speaker 3: if a planet has like a tail, right, and so

1113
00:49:42,280 --> 00:49:44,759
Speaker 3: sometimes if atmosphere is being blown off a planet, you

1114
00:49:44,840 --> 00:49:46,840
Speaker 3: might be able to see that in a transit spectrum

1115
00:49:46,920 --> 00:49:50,080
Speaker 3: or through other types of light detection. So there might

1116
00:49:50,080 --> 00:49:52,360
Speaker 3: be some sneaky ways to look for magnet fields of

1117
00:49:52,360 --> 00:49:53,279
Speaker 3: exoplanets as well.

1118
00:49:53,719 --> 00:49:56,480
Speaker 1: Wonderful well, I expect that the next generation of scientists

1119
00:49:56,520 --> 00:49:58,640
Speaker 1: will be even more creative about coming up with ways

1120
00:49:58,640 --> 00:50:02,360
Speaker 1: to extract a me information from these tiny little blips

1121
00:50:02,360 --> 00:50:03,200
Speaker 1: in our telescopes.

1122
00:50:03,360 --> 00:50:04,040
Speaker 2: Yes, hopefully so.

1123
00:50:04,280 --> 00:50:06,120
Speaker 1: Wonderful well. Thank you very much for coming on the

1124
00:50:06,160 --> 00:50:08,319
Speaker 1: podcast and telling us so much about the mysteries that

1125
00:50:08,360 --> 00:50:10,439
Speaker 1: are under our feet and the mysteries that are out

1126
00:50:10,440 --> 00:50:11,440
Speaker 1: there in the universe.

1127
00:50:11,640 --> 00:50:12,200
Speaker 2: Thanks so much.

1128
00:50:12,200 --> 00:50:14,279
Speaker 1: This was fun, all right. That was my chat with

1129
00:50:14,320 --> 00:50:17,120
Speaker 1: Professor Sabina Stanley again. She's the author of the book

1130
00:50:17,200 --> 00:50:20,520
Speaker 1: What's Hidden Inside Plants, which you can get now at

1131
00:50:20,560 --> 00:50:24,120
Speaker 1: all reputable booksellers. Thanks very much for listening. Tune in

1132
00:50:24,200 --> 00:50:34,480
Speaker 1: next time. Thanks for listening, and remember that Daniel and

1133
00:50:34,560 --> 00:50:37,880
Speaker 1: Jorge Explain the Universe is a production of iHeart Radio.

1134
00:50:38,239 --> 00:50:43,319
Speaker 1: Or more podcasts from iHeartRadio, visit the iHeartRadio app, Apple Podcasts,

1135
00:50:43,440 --> 00:50:45,800
Speaker 1: or wherever you listen to your favorite shows.