Science Friday
Hosted by Ira Flatow
A new book explores how the moon changed us—and how we’ve changed the moon.
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Hey, it's Ira Flatow, and this is Science Friday.
Today on the show, Earth's trusty sidekick, the moon.
We think that the Earth and the moon mixed so completely that they are now basically the same chemically. They're kind of twins in a way.
Summer is such a great time to look at the moon. And you know what? The moon is not just a big rock. The moon is responsible for some of the most important processes here on Earth. Not just the tides, but migrations, reproduction, circadian rhythms, and a whole lot more. Author Rebecca Boyle makes the case for our space sibling in her book, Our Moon: How Earth's Celestial Companion Transformed the Planet, Guided Evolution, and Made Us Who We Are. We talked to her last year when her book came out. And this month, the Sci-Fi Book Club is reading Our Moon. Rebecca, welcome to Science Friday. Thanks so much for having me. All right. You, this is like a love story. You write about the moon, right?
And so I'm going to close my eyes, and I want you to take me to the moon. We've traveled. What do I see?
Well, we've gone about a quarter of a million miles. And if you're on the surface and you've landed and it's been a few minutes, hopefully there's not dust kind of settling still around you in microgravity. You weigh about one-sixth of what you weigh on Earth. It is completely silent, except for maybe the beeping of your life support system in your spacesuit or your spaceship. And there is nothing in front of you but a landscape that only a geologist would love. It's mostly white, mostly gray, but there are flecks of color depending on how the sun hits the rocks and maybe how the angle of the sun is falling on your spacecraft or what's right in front of your window.
It looks very, very desolate and nothing like anywhere you've ever seen on this planet.
We don't know how exactly it came to be, do we? There's debate about why there is a moon.
Yeah. This kind of also blows my mind. Like, we should know a lot about this thing. Like, it's right there. It turns out it's just really complicated. And we know something really horrible happened early in Earth's history when Earth was very new that combined and it created this world we have now, this paired system of worlds, Earth and the moon. So something the size of probably Mars whacked into Earth and both of these things were totally obliterated, like, to dust, because they're both just totally vaporized. And somehow, they both coalesce into these two different worlds. We don't actually know really how that happened because the physics of it are just so complicated and hard to model. But we think that the Earth and the moon mixed so completely that they are now basically the same chemically.
They're kind of twins, in a way. The moon is as much a part of us as we are of it.
Wow. So the moon and the Earth were very close together. And so the moon has been moving away? All these years.
Yeah.
For how many years?
Yeah, it is receding from us about the rate at which your fingernails grow. But over the course of millennia, you know, it's not nothing. And eventually, it will be far enough away that it will no longer totally eclipse the sun.
Oh.
Which will be a bummer, but that's not happening yet.
Okay, good. Don't you find it amazing? I've always found it amazing that it's exactly the right distance away that it creates that total eclipse.
Yeah, this is like my favorite cosmic coincidence. And it's sort of mind boggling to imagine how rare that would be in the whole universe. I don't know if those conditions obtain literally anywhere else. And if it was nearer to Earth, you know, a long time ago, probably had a stronger pull on the tide. And there was an interesting study looking at coral growth rings, which is like, kind of like tree rings. You can sort of date corals and understand their environment by looking at these things. At this one study, there was evidence that the day was 20 hours long 400 million years ago. So the Earth's day is also getting longer as the moon is moving away from us. And because it was closer then, the day was shorter, which meant the tide was more powerful.
And it turns out that a little after that, like 80 million years, so not a blink of an eye, really, but a little while later, this is when Pangea is starting to form and ocean basins are closing. So tides are really extreme in this period about 320 million years ago in the Devonian. So fish, imagine being a fish in like shallow water in this inlet. And there's like an 80-foot change in the height of water over the course of a couple of hours. So you better either get back to the water fast or learn how to breathe the air. And the fish that could do that are the ones that gave rise to all of us.
Let's go to Edward in Adirondack, New York. Hi, Edward.
Um, hi. Um, part of my question has already been addressed, but I know that every, every artificial satellite, its orbit eventually decays. And, um, I, I know that you've already addressed the, the idea that the, um, the moon is going farther away from the Earth. Um, is there any projected idea of how that, um, moving away from the Earth is going to affect Earth itself? Like the tides and every other thing you mentioned?
That's cool. Good question.
Yeah, well, the good news is that it will be a really long time before anything bad happens. So like, you know, million, hundreds of millions of years in the future. But yeah, it will be a bad day when that eventually happens because the moon helps stabilize the tilt of our axis and keeps our seasons and our climate relatively stable over millennia. It controls the tide. It, you know, directs the migrations and reproductive cycles of animals. And all of these things will have to either fundamentally change or, you know, just take place in different ways if we don't have the moon.
Were you surprised at anything that you uncovered about the moon when you were doing your research?
I was surprised at the extent to which it has played such a fundamental role in our concept of ourselves as a species and our understanding of the universe and our place in it. You know, I mean, the moon is the primary way that humans learn to tell time and I think orient ourselves in time. As far as we know, no other animal can do this. Like you can squirrels, you know, for instance, can plan and save food and things like that. But I don't imagine them saying, in six moons from now, I'm going on vacation. And that's a really fundamental shift in thinking. And I think that sort of lays the foundation for this relationship that we've had with the moon the whole time.
Let's go to Rachel in Seaside, California. Hi, Rachel.
This show is a gem for the whole country. And thank you to our author for writing this book.
Thank you.
Helps me to love the moon even more. I heard a wonderful thing that I want to fact check with you because I read it on social media. It seemed to have some backup, some backup articles. I heard that the moon is responsible in part for maintaining our magnetic field that just as it pulls on the Earth's oceans, it also pulls on the Earth's liquid molten core and kind of creates this dynamo effect that maintains this protective shield that is also responsible for why we have liquid water, life and all the rest. So I just wanted to know if you had heard. Is this true?
Yeah, I mean, this is one of these things that's difficult to prove geophysically because like, it's hard to measure the entire magnetic field of Earth in a, in a way that relates to the dynamo and relates to the magma moving around. But yeah, it's a very valid and active theory that the moon plays this big role in through its tide, mostly through its gravitational pull on Earth. But there is another interesting story about this, which is that this fateful day that this impactor, which we call Thea, came to Earth and obliterated Earth and itself. They both remixed and combined into these two worlds. But maybe Thea is still a part of Earth. There's really recent research looking at these strange provinces underneath Earth's
crust that are in its mantle that look like blobs. Like if you could slice Earth in half and look at it face on, it would look like earmuffs covering the iron core of our planet. And there is one theory that those little blobs are the remains of Thea. And if that's the case, then yeah, the moon definitely has played a role.
When we come back, you know, we think a lot about what the moon does to Earth. But how about what the Earth did to help form the moon's surface by keeping it warm?
And the way that the moon differentiated and cooled down into this rocky sphere changed because Earth was here keeping it toasty.
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Doris in Charlotte, North Carolina. Hi, Doris.
Hi, how are you doing?
Hi there, good. Go ahead.
So my question is about Earth's effects on the moon. Everyone talks about all of the things that happen to Earth because of the moon. And we all know a lot of how the moon affects Earth. But how does Earth affect the moon? Does it? Like, as it grows, as it moves further and further away from Earth, is it going to change as well? And what kind of changes would occur?
Great question.
Oh, I love this question.
Thank you, Doris.
Yes. And yeah, the answer is yes. It's so interesting in the ways in which this happens. One of the most fundamental is the weird disparity between the near side and the far side of the moon. So they look really different, like both just looking at them and just chemically, they seem very distinct. And one theory for why that is, is that Earth maybe warmed the near side of the moon when it was closer, when it was first cooling off. And the way that the moon differentiated and cooled down into this rocky sphere changed because Earth was here, keeping it toasty. Another one is that the moon has this very fine, tenuous layer of oxygen, actually, which comes from us. Oxygen is really reactive, and so it likes to go into rocks, and it likes to, you know,
bond with iron and make rust and things like that. So it doesn't last very long, unless life is here making it. And as we know, that's why we have a very oxygen-rich atmosphere. So sometimes, when the moon and the Earth and the sun are aligned in such a way that the solar wind is blowing onto Earth, and then onto the moon after that, some of the oxygen in our atmosphere is blown all the way to the moon, which is this, like, little evidence that we are here and we are alive. And at some point, when the moon's far enough away, that will no longer be the case.
You know, it's been more than 50 years since the Apollo missions put people on the moon and, and there was a little quiet period, I mean, quiet decades.
Yeah, yeah.
And now we're trying to, there's so many landers and we're trying to put people back on the moon, right? Can you give us a sort of a rundown of what's going on with all these attempts?
I mean, just this week, there's been so much news on the moon. It's really crazy. There was a launch on, a few days ago, of this first commercial lunar lander, which is not going to be the first lander now. It burned up in the atmosphere yesterday, unfortunately for this team. And then today, just a couple hours ago, Japan landed a small lander on the moon, becoming the fifth country to do so. We're not sure exactly if it's okay, like, there's some questions about whether or not it is going to get power, or, you know, how it may have rolled over, we're not totally sure. And it's midnight right now in Japan, so the press conference, they all went to sleep. But yeah, the fact that there's so much happening right now is just a reflection of our continued interest, I think. It's always going to be a place that we want to imagine going and being.
And I think being there permanently, you know, looking out from it at Earth permanently, the way that maybe we do on the space station, you know, it's not like there's going to be a city up there anytime soon, or some sort of settlement, but I do think that there will be people up there, coming and going, and living in really austere conditions, probably, you know, but, and trying to do science, trying to do research, maybe trying to go prospecting for resources and to make money and all these different human things. And I think that's going to really fundamentally change the way we view the moon. And it becomes a little bit more of an extension of Earth than it already is, and more of an extension of us than it already is.
Ed on Twitter writes, sort of in your vein, how is the moon being used as a launch site for Mars, a Mars mission?
This is one of the things NASA likes to talk about. They have "Moon to Mars" as kind of NASA lingo for one reason for doing Artemis, which is this sister of Apollo, you know, new human landing program. And, you know, I don't know. Sometimes I think of that meme where it's like the guy walking with his girlfriend and like turning around to look at another woman and the girlfriend's like, "Hey." You know, that's how I feel like the moon is like that girlfriend being like, "Why does the moon need to be a stepping stone for somewhere else? The moon is interesting in its own right." But yeah, I mean, that's one reason why people want to go up there and look around for things like water, because if you can mine for water and separate its hydrogen and oxygen and refine that, then you have rocket fuel. And so you can take less with you off Earth and then get to Mars maybe more easily.
Yeah. Well, thank you very much for taking time to be with us today.
Thanks so much for having me. This was fun.
Rebecca Boyle's book is "Our Moon: How Earth's Celestial Companion Transformed the Planet, Guided Evolution, and Made Us Who We Are." And it is this month's pick for the Sci-Fi Book Club. And again, if you'd like to read along, find out more at sciencefriday.com/bookclub. That's sciencefriday.com/bookclub. Thanks to new scientist Sophie Bushwick, who contributed to that story. This episode was produced by Rasha Areading. See you next time. I'm Ira Flatow.
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