Slicing the moon in half would be disastrous for Earth – but beautiful

It’s time to aim for the moon – and fire at will. In this episode of Dead Planets Society, our hosts Leah Crane and Chelsea Whyte are attempting to crack the whole thing in half. A literal moonshot, if you will.

While the moon may be beautiful hanging in the night sky, it is the nemesis of many astronomers because its light often outshines the dimmer objects they’re trying to observe. Destroying the moon entirely isn’t an option for solving this problem – or is it? Leah and Chelsea are teaming up with experts Haym Benaroya at Rutgers University in New Jersey and Jonathan McDowell at the Harvard-Smithsonian Center for Astrophysics in Massachusetts to act on a long-standing lunar grudge and find out.

It would take an awful lot of force, not just to crack the moon open and turn the resulting debris into what McDowell describes as “the world’s biggest ball pit,” but to keep gravity from combining it all back together right away. A cosmic jackhammer, or maybe a huge array of lasers, might serve to perforate the moon, but it would take something bigger to actually crack it – perhaps harnessing the power of moonquakes, or smashing one of the solar system’s smaller worlds into it.

The consequences of cracking the moon open would be fairly destructive overall. It could create a fiery rain of lunar fragments with the potential to end life on Earth, and the moon’s influence on the tides would change drastically. But it’s not all bad – the release of the moon’s molten centre could create the largest, weirdest piece of sculpture ever.

Dead Planets Society is a podcast that takes outlandish ideas about how to tinker with the cosmos – from putting out the sun to causing a gravitational wave apocalypse – and subjects them to the laws of physics to see how they fare.

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Transcript

Chelsea Whyte: Welcome back to Dead Planet Society.

Leah Crane: This is a podcast where we imagine what it might be like if we were given cosmic powers to rearrange the universe.

Chelsea Whyte: I’m Chelsea Whyte, senior news editor at New Scientist.

Leah: And I’m Leah Crane, physics and space reporter at New Scientist.

Chelsea: And today, Leah, we are going for the big one.

Leah: Yes.

Chelsea: This is the one we want to get from the beginning. Listeners, today we are going to destroy the moon.

Leah: Yes. It’s time to get my arch nemesis.

Chelsea: Look, when you first started talking to me about wanting to destroy the moon, I wasn’t fully on board, right? Like, I love the moon. It’s nice to look at, it makes evenings really pleasant and glowy, but the part of me that does want to break things, thinks the moon’s a pretty good target. So, I think you should tell us, Leah, why do you hate the moon?

Leah: It knows what it did. But honestly, it doesn’t really matter why I, personally, hate the moon. I’m not the only one who hates it. We’re going to crack it in half regardless of anyone’s personal feelings.

Chelsea: And what are we going to use? Are we talking, like, giant jackhammer, lasers?

Leah: We’re going full Wile E Coyote, so I say we try everything. Unfortunately, the moon is not in fact an egg. So, it’s going to take some work to get it cracked. But the aftermath should be really interesting.

Chelsea: Yes. I mean, what’s even in there?

Leah: Rocks. And for some more detailed answers to our questions, we called Jonathan McDowell, who’s an astrophysicist at the Harvard-Smithsonian Centre for Astrophysics. Jonathan hates the moon too.

Jonathan: I hate the moon, yes. The moon is evil because, you know, we complain about how bright all these new satellites are, and the moon is the brightest satellite of the earth, by far. I mean, there’s only one of it, which is good, but it makes a stop ground-based observing of deep, interesting, really faint deep space stuff for, like, half the month, every month. So, you know, what a pain.

Chelsea: So, if you could, would you get rid of the moon? Like, even with just the snap of your fingers?

Jonathan: Yes. The Thanos snap. Alright. Yes. Go on. You know, I think we need to do some kind of environmental impact statement first.

Leah: That’s not how this show works.

Jonathan: Okay. Right, sorry.

Chelsea: Impact statement? Never.

Leah: How very dare you?

Chelsea: But let’s talk about smashing something into the moon. If we somehow cracked it in half, I’m not really sure we’d know what’s inside there or what would come out?

Leah: The yolk.

Chelsea: But that’s why we need to talk to an expert. So, we also chatted to Haym Benaroya at Rutgers University to ask him, ‘What’s in the moon?’

Haym: Actually, most people don’t realise that the interior core of the moon is actually liquid molten, like the Earth. And so, if we did split it up into two, all that molten metal would then come out and pretty quickly, well, maybe not that quickly, it would freeze up as it gets exposed to the atmosphere. So, we could be releasing a blob of something that solidifies with time, and we don’t know how it’s going to expand in the microgravity of space. So, that’s one thing. A lot of what we know about the moon started with the Apollo, because when the Apollo landed on the moon, all these different capsules, they all put different instrumentation on there, they found out that the moon was seismically active, which had their moonquakes. Interestingly, because of the nature of the moon, those moonquakes last a lot longer than earthquakes do. Like, for example, on Earth, an earthquake that’s two minutes long is really a long earthquake. And the two minutes for somebody surviving that is really-, it feels like two hours. But on the moon, even though the magnitudes are a lot lower, the moonquakes are actually very long. They could last an hour. So, people who are now thinking about how to design habitats for the moon, for people to live in, have to consider maybe some of these structures that we design have to account for those special effects.

Leah: Maybe we could consider it in the opposite direction. See if we can get an assist from a quake.

Chelsea: Yes. Can we use the moonquakes?

Haym: Yes. Basically, I guess you could fissure a few locations and then wait for the quake to hit. And those fissures that we created might actually split it. Or at least a chunk of it could be split off.

Chelsea: So, like, perforate the moon, and then let the moon destroy itself?

Haym: Yes. Over time. The only thing we don’t know is how long that might take. So, it might not help today’s astronomers. Maybe astronomers in the future.

Leah: I suspect that, no matter what we do, it’s not going to super help today’s astronomers.

Haym: I don’t think so. In fact, a lot of astronomers today are actually eager to go to the moon, to the far side of the moon, and put their telescopes there, because then, the moon is actually shielding all their equipment from the earth, from all the electromagnetics, all the noise that comes from the earth to the moon. Those are the other astronomers. The evil astronomers that you talk to, that want to destroy the moon, I think have a different vision.

Chelsea: Yes.

Leah: A slightly different vision. It’s an inspired vision, if you ask me. So, we called up one of these so-called evil astronomers.

Chelsea: Okay. So, what if we mine a bunch of holes, lots of them, all around one, like, the equator of the moon, and we drop a ton of TNT down there, like we’re Wile E Coyote, could we make enough of an explosion to blast the moon apart and keep them from, you know, coming back together?

Jonathan: Right. So, you’ve blown the moon into little pieces?

Chelsea: Yes.

Jonathan: Now, these little pieces, right, if you just put in enough energy to break the chemical bonds of the rock and make it into pieces, they’re still again in each other’s gravity field. And so, what happens is you’ve made the world’s biggest ball pit. Right? You have the rocks come back to each other, under gravity, and you’ve made an enormous rubble pile asteroid.

Leah: The biggest, pointiest, worst ball pit ever.

Jonathan: Exactly. And so, that doesn’t cut it. You’ve got to not only explode it enough to smash it into pieces, you’ve got to give enough energy to each of those pieces that they each have lunar escape velocity, and can go apart from each other and not come back together. And that’s a lot more energy.

Chelsea: I mean, do we even have the amount of TNT available to do this?

Jonathan: I don’t think so. So, let’s figure it out. So, you need ten trillion, one megaton thermonuclear bombs to do what you want to do.

Chelsea: Yes. We don’t have that. I mean, that seems like a lot.

Jonathan: Yes. We have too many thermonuclear weapons as is, but that would just be massively too many.

Chelsea: Yes.

Jonathan: So, I think that’s not available in the stockpile right not.

Chelsea: Fair enough.

Jonathan: So, you know, getting that much energy to totally destroy the moon isn’t easy. There’s one way that we know you can do it, that is tried and tested, it’s happened lots of times, and that is to hit the moon at high speed with another comparably-sized object.

Leah: Mercury.

Jonathan: Right. So, Mercury would do nicely. Ceres or Pluto would do nicely. You know, everyone’s down on Pluto now, so let’s just get rid of Pluto.

Chelsea: No. We love Pluto here.

Jonathan: Okay.

Leah: Speak for yourself.

Chelsea: But if we’re going to take down the moon, I will let Pluto die.

Jonathan: Yes.

Leah: But we probably want something that we can control enough to send it, like, from earth towards the moon, right? We don’t want to send the moon bits hurdling back towards us.

Jonathan: That’s right. It does matter a bit the direction that you hit the moon, and it’s not as straightforward as you think because, so what we know from smashing satellites into one another is that when you smash two things together at hypersonic velocity what happens is that a hypersonic shock wave goes through each, reduces it to shrapnel, and the clouds of shrapnel pass through each other, pretty much on the trajectories that they were already on.

Chelsea: Okay.

Jonathan: And so, the risk is that what you’ll end up with, in this case, is the same thing. You’ve nicely destroyed the moon, but its fragments are carrying on in lunar orbit, and are orbiting the earth.

Chelsea: But we could have, like, a cool, shiny, spiky ring around the earth, instead of the moon, right?

Jonathan: No. It would take a while for the moon to re-coalesce, yes. So, that’s right. That’s what you would end up with. It’s a ring that would re-coalesce into the moon after some number of years.

Chelsea: But if we had this ring, would it pose a danger? Like, would there be lots of meteor showers? Would it rain just on earth?

Jonathan: Absolutely because what you’re doing, right, is you’re shredding the moon, you’re leaving it, on average, in the same orbit, but then you’re adding random velocity components to each of the pieces, right? And some of those components are going to send stuff out into the solar system, but some are going to send it to lower perigee orbits, where they can eventually be perturbed and come down, and re-enter.

Chelsea: And destroy all of our satellites and the space station, and all sorts of other things

Jonathan: It’ll do that first, but then it’ll destroy our cities as well because you’ll have, like, re-entering significant asteroid. I mean, you know, remember that a one kilometre asteroid is not good news for life on Earth. Now, admittedly it would be re-entering at a significantly lower velocity than an asteroid. So, instead of coming up from solar orbit, right, they’d be coming in from earth orbit, and so they’d be, sort of, at border seven or eight kilometres a second instead of 30 kilometres a second. And so, that is, you know, ten times less energy.

Chelsea: It’s still not great, though. I mean, not pleasant.

Leah: Maybe there’s a slightly less destructive way. We did start with wanting to crack it, not vaporise it, but before we get to that, quick ad break.

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Chelsea: I was wondering, like, is there any way to use a jackhammer on the moon? Could you, like, use suspenders that, sort of, hook you into the ground and then stay still enough to drill a hole?

Jonathan: So, that’s not as silly as it sounds. So, what you’re saying is actually accurate because it’s very difficult to dig into the moon. So, what happens, you know, the moon gets hit by meteorites all the time. There’s no water, you know, liquid water on the moon. So, all those meteorites that keep hitting the ground, they create a finer and finer dust that work their way into all the gaps in the ground. So, eventually, over millions of years, all those gaps are filled. So, now what you have is a super dense surface. We can’t really dig into it. In fact, people were thinking, you know, maybe you can drill but you can’t really dig. And people are looking at different ways of maybe drill a small hole and put some explosives in there. Sort of, not blow it up, but explode it on the ground to loosen the soil, and then you can dig it. Because, you know, if you brought one of these large cranes from the earth to the moon, assuming you could afford to do it, it tries to dig. What it’ll do is what you just described. It’s going to just push itself off the surface. It won’t be able to dig. So, that’s one of the real challenges about digging. So, you have to maybe drill holes, maybe do a few explosions along the way. You know, if you’re still interested in perforating the moon in order to split it apart, you know, do a lot of drilling. You know, put special explosives in those little holes, and then blow them up, and then that will probably create, like, a little valley that you can then continue doing that until you, you know, you’re digging almost half way to the centre.

Chelsea: Just bombs on bombs.

Jonathan: Eventually, yes.

Leah: Would we be able to see something like that from earth? Like, if we dug a, yes, we probably would, right?

Jonathan: You would, yes.

Leah: If it was on the nearside.

Jonathan: Yes. In fact, our telescopes now can see the Apollo stuff that was left behind on the surface.

Leah: Right. So, we wouldn’t be able to get away with this Wile E Coyote plan undetected?

Jonathan: No. Not unless you do it on the far side of the moon.

Chelsea: But I feel like we would want to do it on the nearside because, like you were saying, any sort of, you know, debris, like, I feel like we’d want to crack it from our side. But maybe I’m wrong.

Leah: Because we would want to push the debris away.

Jonathan: Yes. It’s hard to tell. Certainly, whatever you do on the side facing us, like explosions and digging, and stuff, will throw stuff our way. So, maybe the far side makes more sense, because then it will, sort of, throw it the other way, away from the earth.

Leah: Right. And then the space police won’t catch us.

Chelsea: Now, what about another idea?

Jonathan: Okay.

Chelsea: Follow me here. Are there lasers powerful enough that we could take ships out to the moon, and fire lasers at it, and either cut it in half or blow it up? Like, because you were talking about how dense it is, I’m curious, like, do we even know if that’s possible?

Jonathan: Well, there are really military-grade lasers, which could probably do a lot of damage wherever they hit. So, I would think, probably, with time. It’s like what we said before, you know, do some small explosions, then we get a valley, we do some more. So, I think with a laser, it just keeps working. Maybe while it’s orbiting it’s, sort of, lasers are circumference, and then eventually works its way down, and eventually maybe, you know, we send that huge chisel that you had right into one of those valleys that the laser created and then, you know, just pull it apart. We get some special tool to pull it apart, you know? Like atlas, with a lever, you know, lifting the moon on his shoulder.

Leah: Yes. It reminds me of the process they use to, like, cut steel, to make stuff with. You just cut it with the laser.

Jonathan: Right.

Leah: We could just do that to the moon, but it might take a while because of the moon is big.

Chelsea: Yes. But also, we have to do some kind of laser heist. I don’t know where we’re getting a military-grade laser.

Jonathan: Well, you know, I think all things are on the table, right?

Chelsea: Right.

Leah: We’re conjuring it.

Chelsea: Okay.

Jonathan: Yes.

Chelsea: Cosmic space laser, we have that one. Okay, great.

Leah: Yes. And I’m just thinking of the moment where if you’d spend, you know, years and years very patiently blazering a deeper and deeper circumference around the moon, and then I just want to send something in there, like in Star Wars, like, into that valley, and just go, and pop it apart.

Jonathan: That’s right. That last increment probably doesn’t have to be very big or very complicated.

Leah: Right.

Chelsea: We could go in it.

Leah: I feel like that would be bad.

Chelsea: Would the moon’s own gravity be counter-acting what we’re doing here? Like, would it try to be forming back together as we’re orbiting and lasering this slice through?

Jonathan: Yes. It’s a good point. It really would, right? So, imagine that we actually split it into two halves. Those two halves are now attracting each other. So, they’re going to try to stay together.

Chelsea: So, we need need not just a little boop. We need a big bang to get those guys far away from each other.

Jonathan: Right. So, we can slit it with a small bump, but then, to get them really far apart, maybe orbiting opposite sides of the earth, we’d need something pretty significant.

Leah: Right. So, we’re going to have to do a military-grade laser and a nuke. It’s going to have to be a combo platter.

Jonathan: Or get some space tugs, you know, slowly pull them apart.

Chelsea: Oh, yes. Net each side and just drag it.

Leah: With the metal flowing out of the middle?

Jonathan: That’s right. Which is actually probably safer because, that way, you can, sort of, control it as you pull them apart. And maybe they won’t break apart. Maybe put a huge net around each half of the moon so rocks don’t fly off, you know? So, we could, sort of, map it out so that we don’t cause more damage than what we’re trying to do, which is get two moons, right? That’s the goal? Get two moons?

Chelsea: Well, yes. Destroy the one moon. Whatever we end up with is fine.

Jonathan: Whatever we end up.

Leah: But I like the idea of two moons.

Chelsea: But I’m curious, then, once we’re pulling those two halves apart, are we going to get that molten metal, sort of, cheese pull in the middle?

Jonathan: Yes, you would. I’d have to think about how long it would take to freeze it, because it’s not that small, you know? Let me see. It’s probably, like, a few hundred miles. Imagine a few hundred miles diameter ball of molten metal. So, as soon as it’s exposed to space, then it’s going to start freezing. So, depending how fast you pull it apart, you might end up with a really weird modern art kind of shape after it starts pulling apart. You know, if it freezes too fast, maybe it’ll keep those two halves together and we’ll have, like, the weirdest moon in the universe.

Chelsea: Yes. Like a dumbbell shape.

Jonathan: That’s right. Maybe that’s better than destroying it. Get, like, a unique moon out there.

Leah: Yes. We’re turning the moon into art.

Jonathan: Modern art.

Chelsea: I’m into it.

Leah: It’s interesting to think about. Like, if we did have two halves of the moon up in the sky, probably on at least slightly differently timed orbits, that would look completely crazy, right?

Jonathan: It would change everything on Earth from the point of view of, you know, how much light is reflected off the moon. When we look up at the sky, sometimes you have a very bright moon. So, now it’s going to be smaller. Maybe the surface will change, so the reflection will change as well. It could play havoc with our tides, right? So, the moon is very important to the tides of all the lakes, and rivers, and oceans. So, now you have half. Each of these, say, is half the original moon. So, it has half the effect on the Earth, on the tidal forces. And now you have two of them, so now, instead of having, like, the maximum tide once every 24 hours, you’re going to have tides going maximum when each half of the moon goes around a certain location. Maybe that’ll make the waves larger, maybe it’ll make the tides more erratic. You know, who knows what’ll happen?

Leah: That seems bad for life.

Jonathan: It’s complicated, right?

Chelsea: Okay. What if we put both halves on either side of the earth, exactly opposite of each other, and got them going the same speed, and they were, sort of, inter-locked in that. Would that cancel out the tides?

Jonathan: No because there’ll be, if you imagine the spot in between the two of them, that will be a low tide. So, tides will happen every twelve hours.

Chelsea: Would just be double the speed?

Jonathan: Yes. Every twelve hours, but they won’t be as big of a tide as now, as what we have now.

Leah: So, weird tides and an absolutely wild night sky.

Jonathan: It could look like a modern art sculpture. Probably the biggest sculpture in existence.

Leah: I’m picturing, like, a Chihuly.

Chelsea: Oh, yes.

Jonathan: Chihuly? Yes.

Chelsea: I do like the idea of becoming the sculptors of the largest piece of art in the universe.

Jonathan: It definitely would do that, and probably will be multi-coloured, too, as different parts cool at different rates, you know? So, it’ll be pretty cool.

Chelsea: The metal rainbow in the sky. Yes, okay. We’re doing this.

Jonathan: A permanent one.

Leah: I’m in. Let’s do it. Let’s get started tomorrow.

Jonathan: Okay.

Chelsea: While we get started on that, thank you to Haym and Jonathan, and to you for listening. Moon officially vanquished.

Leah: And from our inbox, we’ve got a question from Sarah Duncan who asks, ‘What would it take to destroy a black hole? Is it even possible? If a nearby black hole was destroyed, would it affect our solar system?’

Chelsea: That’s a really great question, Sarah. That’ll be a tough one. Hopefully, we can get into it in a future episode. If you have any questions to add to our list, our email is deadplanets@newscientist.com, and if you joined us for a live recording at New Scientist Live over the weekend, thanks for coming. We’ll be sharing that episode in two weeks, so look out for it in your feed.

Leah: And if you just want to chat about any of our episodes so far, hit us up on Twitter, or X, I guess. I’m @downhereonearth, and Chelsea is @chelswhite. See you next time.

Chelsea: Bye.