Daniel and Kelly’s Extraordinary Universe - Why is half of the moon always hidden?

Episode Date: August 29, 2019

Visit the far side of the moon with Daniel and Jorge Learn more about your ad-choices at https://www.iheartpodcastnetwork.comSee omnystudio.com/listener for privacy information.

This is an I-Heart podcast. Ah, come on. Why is this taking so long? This thing is ancient. Still using yesterday's tech, upgrade to the ThinkPad X-1 Carbon, ultra-light, ultra-powerful, and built for serious productivity

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so you can work, create, and boost productivity all on one device. December 29th, 1975, LaGuardia Airport. The holiday rush, parents hauling luggage, kids gripping their new Christmas toys. Then everything changed. There's been a bombing at the TWA. terminal, just a chaotic, chaotic scene. In its wake, a new kind of enemy emerged, terrorism. Listen to the new season of Law and Order Criminal Justice System

on the IHeart Radio app, Apple Podcasts, or wherever you get your podcasts. My boyfriend's professor is way too friendly, and now I'm seriously suspicious. Wait a minute, Sam. Maybe her boyfriend's just looking for extra credit. Well, Dakota, luckily, it's back to school week on the OK Storytime podcast, so we'll find out soon. This person writes, my boyfriend's been hanging out with his young professor a lot. He doesn't think it's a problem, but I don't trust her. Now he's insisting we get to know each other, but I just want her gone. Hold up. Isn't that against school policy? That seems inappropriate.

Maybe find out how it ends by listening to the OK Storytime podcast and the IHeart Radio app, Apple Podcasts, or wherever you get your podcasts. Do you know we're not the first people to join physics and cartooning? What? I thought we were definitely on the forefront there. No, you know, one of my favorite comic strips ever is named after something awesome in physics. Ooh, let me guess. Calvin and Hobbs? No, no, that's philosophy.

Thinking, thinking, Garfield? Wait, do you think I like Garfield? It's the same joke every time. That's true. Are you thinking just because of quantum fields? Like maybe Garfield is another quantum field? Maybe peanuts? I don't know. I have no idea how peanuts could relate to physics. I am officially disappointed in you.

All right. I give up. Hi, I'm Jorge. I'm a cartoonist and the creator of PhD comics. Hi, I'm Daniel. I'm a particle physicist. And I have no idea what cartoons relate to physics. Especially ours, right? Especially ours. And welcome to our podcast, Daniel and Jorge Explain the Universe, a production of I-Hard Radio. In which we talk about crazy things about the universe, things that are close by, things that are far away, things on one side, things on the other side.

And we break it down an attempt to explain something to you that's both mind-blowing and actually understandable. That's right, all the things that are both maybe right here and kind of far away at the same time. That's right. Nearby and yet hidden. We seek to reveal those truths to you. So today on the podcast, we'll be talking about something that is basically in our everyday lives, right? Well, every night lives. Every night life. Yeah, my night life is not that exciting anymore. But back when I used to go out at night, yeah, it's something that I would wonder about. Back before Netflix. Back before kids. But yeah, this is the kind of thing, you know, you can look up in the sky and easily wonder about. Yeah, it's right there almost every night.

And yet we can't see it. Nobody really knows what it looks like, right? Until recently, that's right. Nobody had ever seen it, even though it hangs right there. And so today we're talking about what's on the far side of the moon. That's right. If you look up in the night sky often, you may notice the moon, of course, and a sharp observer may notice that the moon looks similar every time. The portion of it you can see changes, right, becomes a crescent, becomes larger.

But if you pay attention, you notice that the features you see on the moon are actually the same every night. Yeah, it never changes that, right? That's mind-blowing to think because the moon is a giant sphere and we're a sphere and we're going around the sun spinning and the moon is spinning around us. And yet we always see the same side of the moon all every night. That's right. It doesn't change. One side of the moon is the near side. That's the side that faces the earth.

And the other side faces away from the earth towards the rest of the year. universe. And until 1959, no human had even seen a picture of it. We had no idea what could be on it. It could have been like filled with crazy lunar civilization or, you know, have a message written on it or something. Like,

I can't believe you took you guys this long or something, right? It could have been filled with Israeli tardigrades for all we know. I think you're fast forwarding a few decades, yeah. But yeah, I mean, there could have been even nothing, right? It could have been just a half sphere for all we know.

The moon could have just been like a slice orange and we only see one side of it, right? Yeah, it could have been that the moon is actually a big prop, right? And if we come around the other side, we see like the scaffolding and all that stuff. That could have been amazing. And, you know, we make a joke about it. Could we even have known that the moon was a sphere and not just like a giant disk floating in space? I think it would be pretty hard to get a giant disk in any model of moon formation. But you never know, right?

And this is why we explore, because you got to say. see stuff to really understand. You can speculate, you can say, we think we know what the backside of the moon is like. Turns out when we saw it, there were some surprises. And until you, really, yeah, there were some surprises. The backside of the moon is not the same as the front side of the moon. And you know, you got to go and look. This is why we do experiments. This is why we explore the universe, because until you see it, you never really know. And so only a handful of humans have actually seen the other side of the moon, right? Seen it, yeah. I mean, we've had pictures and only a handful of humans have seen it sort of like with their own eyes. Yes,

that's true. It takes, you have to orbit the moon in order to see that. So yeah, only a few people have ever seen this. But, you know, fewer people have ever seen my moon. It's not quite as prestigious, but. Yeah, let's not get into that on this podcast. Let's say that for Daniel and Jorge after dark. Okay. All right. That's, folks, that's the sound of Jorge carefully stepping away backwards from that joke. No, but it's a fascinating topic. And I was wondering, did people understand that? Because it's kind of odd.

Is it like a giant cosmic coincidence or is it totally normal for us to only see one side of it? That's a, that's why I'm blowing to me. Yeah. So I walked around and I asked people, you know, what do they think about this? Were they aware of it? Did they realize? Did they understand it? Could they give a physical explanation?

Yeah. So as usual, Daniel went out there. Somewhere in the world, where were you, at this time, Daniel? Were you in California or? No, I was back in California. So these are UC Irvine summer students who answered these questions. As usual, Daniel went out and asked random people on the street. The question of the episode.

And today's question was, today's question was, did you know that that half of the moon always faces away? So think about it for a second. If you had realized this or if you knew this, I'm sure a lot of our listeners knew this, but maybe you hadn't thought about it for a while. And so think about what you would answer if a random physicist approach you on the street. Yes.

Do you know why that is? Just I know because I know that the Earth rotates and I know the moon doesn't. There's a reason why we only see one face of the moon and never the other. I did not. There is a side of the moon that did not face the Earth. Because of Earth's rotation as well. Yeah, I mean, my understanding is the Moon is rotating around the Earth. And the Earth rotates on its axis because it's spinning.

But, yeah, I didn't realize the moon was spinning, too. I didn't think it was. I guess because both the moon and the earth are rotating, and so we never see the backside. Related to rotations of the stellar bodies. No, I did not know that. Yes. Well, do you know why that is?

Is that a coincidence? Is there a physical reason? Physics. Physics. Yeah. Okay. Awesome. Oh, all right.

So a lot of people didn't know. Yeah. And a lot of people didn't know. Yeah, some people were really shocked. And as soon as they understood that it was happening, they were like, that's really weird. How could that be? What? Yeah.

It's almost like it's doing it on purpose, right? Like the moon is suspicious of us and doesn't want to turn its back to us, you know? Like it's hurling through space, but it's like, I don't want to, I need to be facing the Earth at all time. And it's slowly backing away also, right? Don't forget. We're losing it very gradually. So the moon is sort of like edging away from us the way you're edging away from my inappropriate jokes. Yeah, so I guess it's not as well known as I would have guessed it was, you know?

A lot of people seem surprised. And of the people who did know that it happened, none of them could give me an explanation for why, right? Nobody understood the physics of it. People appreciated the concept, but nobody could explain why. Well, you know, I think the question I have is, what's the official name for it? I think we've called it the far side of the moon, the backside of the moon. I think Floyd called it the dark side of the moon. It's called the far side of the moon, right?

And I think that's probably inspiration for that cartoon, right, the far side. Because like, what's going on over there? Like the weird hidden side. Though I'd love to ask Gary Larson about that one day. It's not the dark side of the moon, though, because... Oh, actually, I do know the answer to that because I just read a little bit of his biography. Oh, what is the answer? The answer is he had another name for it, but then when he sold it to a syndicate or a newspaper, they said,

hey, how about we call it to far side? And he's like, sure. Well, editors actually contribute something? I never heard of that before. That's the anti-climatic story. And if our editors listening to this podcast, we love everything you suggest, by the way. That's right. We meant newspaper.

That's right, comic editors. No, so the far side is the backside of the moon, the side of the moon that always faces away into the cosmos, away from the earth. The dark side of the moon is the name of a Pink Floyd album, right? And is not the same thing because the... side of the moon that's lit up is the side of the moon that faces the sun, right, not the side of the moon that faces the earth. So the dark side of the moon is the side of the moon that faces away from the sun, right? So sometimes the far side of the moon is lit up, like when the moon is right between the earth and the sun, then the far side is totally bright and

the near side is totally dark. Oh, wow, I never thought about that before. Yeah. Because I guess the far side of the moon gets lit up sometimes. It does. And so like sometimes the sun is just like blasting it with energy, but there's nobody there to look, right? It's like whatever secrets the far side of the moon holds, you know, are being revealed by the sun, but nobody's looking at it. Right. All those beautiful lunar sunsets and sunrises, nobody there to appreciate it. Because the moon doesn't have a stable dark side, right? It's not always the same side that's dark. The temperatures on the moon vary like crazy, right? If you're on the bright side of the moon, it can get warmer. If you're on the dark side of the moon, it gets like super duper cold.

And because there's no atmosphere to hold in the temperature, it basically, as the boundary between the bright side and the dark side moves across the surface of the moon, the temperature just is like plummeting super quickly. So the dark side of the moon changes all the time, but the far side of the moon never changes. That's right. That's the weird part. That's right. And you heard.

And it's never changed or it's, you know what I mean? Like, are we looking at a different moon than human? minutes 10,000 years ago or it's never changed? That's a great question. You know, in old drawings of the moon, it looks the same, but that only goes back, you know, like a thousand years or so. But the physics that we'll explain in a few minutes suggests that it hasn't changed in a long, long time. It should be stable. Wow. And that is so weird. It is weird. And, you know, let's describe exactly how weird that is, because in people's responses, you could hear, there was some confusion about, like, exactly what's doing the spinning and what could be affecting it. So let's go through that.

in some detail and explain what's happening before we explain why. Because the Earth is spinning around, we're spinning around, and the moon is spinning around us at a different rate, right? And the only things you really need to think about, you don't need to think about the fact that the Earth spins, it doesn't matter, or if the Earth is orbiting the Sun. The only two things you need to think about are the Moon moving around the Earth, right? The Moon is in orbit around the Earth. It goes around the Earth, and the Moon is spinning.

It's kind of like we are spinning around the Sun once every year, but we're all. also spinning in place kind of that's right exactly and a different part of the earth faces the sun literally every day right it's the earth doesn't have a near side and a far side to the sun right right so and that's because we orbit it takes us a whole year to go around right but only takes us a day to spin right but in the case of the moon it spins at exactly the right speed so that the same side of the of the moon is always facing the earth those two numbers how long it takes to go around the earth and how fast it spins around are perfectly synced up so that the same side of the moon is always facing the earth.

Oh, and not just synced up, but they have to be synced up going the opposite way, right? Yeah, if the moon is going around the earth clockwise, then the moon has to be going around spinning in place counterclockwise at exactly the same number of times per day or per night. Let me just check that my mental model here. This is hard to figure out. So if it's moving around clockwise, imagine the near, so you have the near side,

start at 12 o'clock, right? And the near side of the moon is, of course, facing the earth. If the moon didn't rotate, then by the time you got to 6 o'clock, then the, what we call the far side of the moon would be facing the earth.

So in order for that not to happen, it also has to rotate actually clockwise, right? So it moves around the earth clockwise, and it rotates clockwise, so that it's the same side, is always facing the earth. Oh, right. Yeah, it's tricky. Yeah. Yeah, sorry, I got that totally wrong. It's hard to keep track of. Hey, editor, can you please, um, can you make Jorge never say

anything wrong? Yeah, can you make me sound a little bit more intelligent there? Thank you. Yeah, there you go. Oh, you're right, you're right. It has to, um, kind of like spin, oh, wow, yes, it has to spin the same direction at the same rate. Exactly. It has to spin the same direction at exactly the same rate. And, you know, anytime you see a coincidence in physics, like these two numbers, which could be different, happen to be exactly the same thing, you got to look for a physical reason, because either it's a ginormous coincidence, or it's a signal from the folks who invented the simulation that is our universe, or there's a physical reason that it has to be that way. Right, right. Because it's, it's, it's, I feel like it's rare, right? Like the earth

doesn't do that around the sun, and none of the other planets do that around the sun, right? Like, they not just spin at different speeds, but they spin in like different axes and different directions. And so it's like, just because you're going around at a larger object doesn't mean that you're going to have this perfectly synced orbit, right? Yeah, you're right. None of the planets in our solar system have this same feature. Though there are some other moons, some of the moons of Jupiter do the same thing to Jupiter. Right. And that's a clue, right?

Because if you have a one coincidence, that's crazy. If you have the same coincidence several times, then, you know, that's a sign that there's some physics happening. I think you're telling me that it's all due to this very interesting physical effect, right? Like, there is a physics of why this happens. There's definitely some physics, yeah. Yeah, so let's get into it. But first, let's take a quick break. Ah, come on.

Why is this taking so long? This thing is ancient. Still using yesterday's tech, upgrade to the ThinkPad X1 Carbone. Ultra-light, ultra-powerful, and built for serious productivity with Intel Core Ultra processors, blazing speed, and AI-powered performance. It keeps up with your business, not the other way around. Whoa, this thing moves. Stop hitting snooze on new tech.

Win the tech search at Lenovo.com. Lenovo, Lenovo. Unlock AI experiences with the ThinkPad X1 Carbon, powered by Intel Core Ultra processors so you can work, create, and boost productivity all on one device. December 29th, 1975, LaGuardia Airport. The holiday rush, parents hauling luggage, kids gripping their new Christmas toys. Then, at 6.33 p.m., everything changed.

There's been a bombing at the TWA terminal. Apparently the explosion actually impelled metal glass. The injured were being loaded into ambulance. is just a chaotic, chaotic scene. In its wake, a new kind of enemy emerged, and it was here to stay. Terrorism. Law and Order Criminal Justice System is back.

In Season 2, we're turning our focus to a threat that hides in plain sight that's harder to predict and even harder to stop. Listen to the new season of Law and Order Criminal Justice System on the IHeart Radio app, Apple Podcasts, or wherever you get your podcasts. My boyfriend's professor is way too friendly, and now I'm seriously suspicious.

Oh, wait a minute, Sam. Maybe her boyfriend's just looking for extra credit. Well, Dakota, it's back to school week on the OK Storytime podcast, so we'll find out soon. This person writes, my boyfriend has been hanging out with his young professor a lot. He doesn't think it's a problem, but I don't trust her. Now, he's insisting we get to know each other,

but I just want her gone. Now, hold up. Isn't that against school policy? That sounds totally inappropriate. Well, according to this person, this is her boyfriend's former professor, and they're the same age. And it's even more likely that they're cheating. He insists there's nothing between them. I mean, do you believe him?

Well, he's certainly trying to get this person to believe him because he now wants them both to meet. So, do we find out if this person's boyfriend really cheated with his professor or not? To hear the explosive finale, listen to the OK Storytime podcast on the IHeart Radio app, Apple Podcasts, or wherever you get your podcast. All right, we're talking about why the moon always looks the same every night all the time. Like it's out there spinning around the earth and it's spinning around its own axis, but it always seems to face the earth the same way. And so that's weird, right? Yeah, it's due to an effect called tidal locking,

which is connected to something we've talked about several other times called tidal forces. And it's pretty simple, right? Like the tides of the ocean? Yeah, just like the tides of the ocean, right? It's the same effect. And the idea is the gravity will pull more strongly on stuff that's nearby than stuff that's far away, right? That makes perfect sense. We're familiar with that.

But we're used to thinking about objects sort of as points, like the earth goes around the sun. We just think about the force on the whole earth, right? Or the moon goes around the earth. We think about the force on the whole moon. But the moon is kind of big, right? which means that the force on the close side of the moon is stronger than the force on the far side of the moon, right? Oh, the earth is pulling the parts of the moon that are closest to it more than it's pulling the stuff that's in the behind it. Exactly. And those are called tidal forces. And if tidal forces are strong enough, like if you're near a black hole, then the difference in the force on one side of the object and the other can be enough to tear it apart, right?

And you might be thinking, tear it apart. What? If you're pulling on something with two different forces in the back and the front side, that's the same thing as pulling it apart. That's the same thing as applying a force from one side to the other. And so, for example, if you get too close to a black hole, you will literally get shredded into bits. And, you know, we've seen this before.

Like Shoemaker Levy was a comet that came too close to Jupiter, and Jupiter pulled it apart into 26 pieces. It still went around the sun and slammed into Jupiter, so it got its revenge. But tidal forces are a thing. thing. Anytime you have an object that's large compared to the force of gravity, then it's going to have a big difference in the gravity on one side and the other. And that's the same way the moon makes tides on Earth, right? It pulls the water closer to it to make the tides.

But it's not just with big objects in space. It's like happening all the time to everyone everywhere, right? That's right, yeah. Like if I stand up, if I stand up right here in my studio, my feet aren't getting pulled by the earth more than the top of my head. That's right. The earth is literally pulling you apart. Now, your body is strong enough to withstand that fairly small difference between the force on your head and the force on your feet. But yes, the earth is trying to pull you apart, unless you're lying down flat, in which case the earth is pulling on every part of you the same way. And if you're really tall, you know, then the earth might pull you to bits. But it mostly happens to large objects where the distance between one side and the other side is

large so that the magnitude of the force of gravity is large between the between the two and that's when you notice it so the difference is larger yes exactly so the difference is larger and the moon is big enough that the earth's gravity pulls one part of it harder than the backside of it and it actually changes the shape of the moon a little bit so the moon is not a sphere it's like and it's like an obloid object it's like a 3d ellipse the moon is not perfectly spherical it's not perfectly spherical because is getting squeezed by the earth. And if these tidal forces were stronger than the Earth, then the Moon would get pulled apart, right?

That's what happens when a moon gets too close to a planet, for example. It can get pulled into pieces and turned into rings, right? And so the Moon is in this place where it's close enough to the Earth to be in orbit, close enough to have these strong tidal forces, but not so close that the Earth pulls it apart. Interesting. And so Earth kind of squishes the Moon out of a perfectly spherical shape, But then how does that relate to why we only see one side of it?

Well, because then it gets stuck, right? So now the moon is not a sphere. It's an ellipse. And the half that's closer to the earth is even closer than it was back when it was a sphere, right? It's like it's fallen down a little bit. And so that part gets heavier, right? It has a stronger force of gravity. And on the backside, it's an ellipse also.

And that part, it gets even lighter. So now the near side of the moon weighs more than the backside of the moon, meaning there's a stronger force of gravity. So now it's sort of stuck, right? It's like a ball and a hole. The close side of the moon, you can't spin away, right? Because if it spins, then the fat part gets pulled back towards the earth. Exactly.

You know, imagine you have like a bicycle wheel, right? And you're holding it and it spins freely. And it's happy to be in any arrangement, right? It spins because every arrangement is the same if it's a perfect circle. But now put something heavy on one spot of the bicycle wheel. What's going to happen? it's going to prefer for that part to be down, right? And if you push it away a little bit,

it's going to spin back so that the heavy part is down. That's what happened to the moon. The near side of the moon is heavier than the far side because it's closer to the earth and sort of stuck in that way. And that's the reason? That's the reason why we only see one side of the moon? That's the reason. It's called tidal locking, right?

Tidal forces change the shape of it a little bit. And then that shape makes it more conducive to always face the heavier side towards the planet. And so it happened to the moon, and it's happened to several moons of Jupiter. And it's not that uncommon a thing. So it's not a coincidence at all, right? It's physics. Yeah.

So blame the tides. The tidal forces of the moon cause tides on Earth, but the tidal forces of the Earth cause the moon to always have a near side. But wait, I'm a little bit confused. In order for the Earth to deform the moon, doesn't the moon need to be stationary? Do you know what I mean? Like if the moon was spinning, then this. tidal force would even out across all sides, right?

Kind of like the earth is a little bit fat around the middle because we're spinning and part of it gets more attracted to the sun sometimes. Yeah, that's a good point. I think if the moon was spinning fast enough, it might have been able to avoid this, right? Because it could, it could sort of spin out of that little well that it gets stuck in and have another part of it be stretched. So the stretching would be evened out. But I guess that just means that in the early days, the moon was not spinning fast enough

to avoid this. remember the moon formed out of debris right the moon was just a big cluster of debris it's not like the moon was a perfect sphere that was spinning and then just sort of placed on earth it was formed in place right and the earth had a role in in that formation oh and when it formed it formed in this weird deformed shape yeah which locked it into always facing the right the same way yeah so it probably was never a sphere right it's not like back in its early days in its youth it remembers being having a perfect body and then the earth ruined it and then it hooked up with the earth and it got all blobby exactly oh i see the moon formed into the right blob into that blob right and but that

also means that all of the debris that formed the moon didn't have a lot of spin to it right like maybe it was sort of basically kind of static when it formed because it would you know you know i mean like if it formed out of debris that's moving flowing flowing around it would eventually coalesce into a spinning ball, right? Yeah, basically everything has some angular momentum, right? Because to have no angular momentum would mean for everything to magically cancel out. So if you just took all that debris, and for those of you who aren't familiar with how the moon is formed, we did a whole podcast episode about how the moon probably came from some of the

collision of a small planetoid with an early Earth and a huge amount of debris was thrown out into space and some of that stuff coalesced into rings and then eventually, into the moon. And so it's, you know, there, we don't have a lot of information about exactly what that collision looked like, but the amount of rotation, the amount of spin in that debris depends a lot on like how that first planetoid hit the proto-earth, how much spin there was. There must not have been a lot of spin, because if there had been a lot of spin, then, you know, the moon would have started out spinning and maybe this tidal force would not have deformed it into the right blob.

Spinning fast is a good defense against getting stretched out by title forces. It's a good way to keep your shape, keep in shape. That's right. I recommend spin classes to the moon. There we go. Cool. So that tidal forces is the reason that we always see the same side of the moon. Physics explains it in the end.

One more mystery dismantled by physics. Once more, the magic is gone. Thanks to... Physics, ruining the magic for thousands of years. All right. Now, let's get into what is on that far side of the moon. Are there aliens? Are there nothing?

Are there... Is there a secret message to you? That's right. But first, let's take a quick break. Ah, come on. Why is this taking so long? This thing is ancient. Still using yesterday's tech, upgrade

to the ThinkPad X1 Carbon, ultra-light, ultra-powerful, and built for serious productivity with Intel core ultra-processors, blazing speed, and AI-powered performance. It keeps up with your business, not the other way around. Whoa, this thing moves.

Stop hitting snooze on new tech. Win the tech search at Lenovo.com. Lenovo, Lenovo. Unlock AI experiences with the ThinkPad X1 Carbon, powered by Intel Core Ultra processors so you can work, create, and boost productivity all on one device. December 29th, 1975, LaGuardia Airport.

The Holiday Rush. Parents hauling luggage, kids gripping their new Christmas toys. Then, at 6.33 p.m., everything changed. There's been a bombing at the TWA terminal. Apparently, the explosion actually impelled metal, glass. The injured were being loaded into ambulances. Just a chaotic, chaotic scene. In its wake, a new kind of enemy emerged, and it was here to stay.

Terrorism. Law and order criminal justice system is back. In season two, we're turning our focus to a threat that hides in plain sight. That's harder to predict and even harder to stop. Listen to the new season of Law and Order Criminal Justice System on the IHeart Radio app, Apple Podcasts, or wherever you get your podcasts. My boyfriend's professor is way too friendly, and now I'm seriously suspicious. Oh, wait a minute, Sam. Maybe her boyfriend's just looking for extra credit. Well, Dakota, it's back to school week on the OK Storytime podcast, so we'll find out soon.

This person writes, my boyfriend has been hanging out with his young professor a lot. He doesn't think it's a problem, but I don't trust her. Now, he's insisting we get to know each other, but I just want her gone. Now, hold up. Isn't that against school policy? That sounds totally inappropriate. Well, according to this person, this is her boyfriend's former professor, and they're the same age. And it's even more likely that they're cheating. He insists there's nothing between them. I mean, do you believe him?

Well, he's certainly trying to get this person to believe him because he now wants them both to meet. So, do we find out if this person's boyfriend really cheated with his professor or not? To hear the explosive finale, listen to the OK Storytime podcast on the Iheart Radio app, Apple Podcasts, or wherever you get your podcast. All right, we're talking about the moon and why it always looks the same every night. it doesn't seem to be spinning the moon, even though it's a giant spherical object.

And so we figured out, we talked about that it's due to tidal locking. So it formed in such a way that it's always spinning at the right rate that we always see it the same way. That's right. The near side of the moon has basically become heavier because it's turned into a little bit of an ellipse, and that makes it prefer to keep that side to the earth.

I imagine that wasn't always the case. You know, when the first, can you imagine being on the earth when the moon formed? Like, you know. I think that would be pretty hot and nasty, given that it formed out of a huge collision and the earth is basically a ball of lava. Oh, yeah.

That'd be a short trip. Okay. Not so romantic. No, no. No. Hot and nasty, but not in a good way. All right. So due to this tidal force,

the moon, when it formed, formed such a way that it basically got locked into always facing the earth the same side. That's right. Which means if there's a side of the moon that we cannot see from the earth and people didn't see until

1959 when the Soviets finally sent something up there to take a picture of it. Really? It was the Soviets who first saw it? Yeah. Remember back in the day, the Soviets were leading us in the space race, right? In the 50s and the early 60s, Sputnik and all that stuff,

they were ahead. And actually, it's pretty funny because the Soviets were there first, right? They were the first ones to see this stuff. And so the Soviet scientists, they just started naming things in Russian, right? and boy, this annoyed the Americans. Not only because they, you know, didn't get to see it first

and they didn't get to take the first pictures, but now everything on the backside of the moon is like, has some crazy Russian name. Wow. Is that true? Yeah, totally. You think I'd just make this stuff up? I don't, maybe. No, this is totally true.

Well, so they, what did they send, like a satellite and it took pictures as it went around the backside of the moon? Exactly, yeah. And back then, you know, we didn't have digital photographs and all this kind of stuff. So they had like the pictures first and they started naming the craters and the features first.

Exactly. So everything on the backside is named in Russian? It started out that way. But then the Americans got the international astronomical union to intervene and then they decided to do

a sort of international process which is, you know. What do you mean intervene? Like they were in the middle of naming things and then they're like, whoa, whoa, stop, stop. Yeah, exactly. Exactly.

Anyway, it turns out that the backside of the moon is not just like the near side of the moon, right? It's not exactly the same. How can it be different? Yeah, it's still sort of a mystery. We don't actually still understand it. Now, it's not dramatically different.

I mean, in the end, it's just rocks and dust, right? It's not like there's a glittering ocean there or some civilization or like crazy mountains or anything like that. No, it turns out that there are more craters. And if you look at the moon from the earth, you see these sort of pockmarks. And you also see these open areas that we call seas, even though there's no. water in them and the backside of the moon has more of these craters and fewer of the seas so it has a different complexion yeah exactly it has more acne and you might be tempted to think oh that's because

you know it's facing out and so it's going to get hit right right yeah like a shield yeah but the earth is not actually a very large in the sky of the of the moon right the moon is kind of far away and the earth only protects the moon by about like three percent of its sky or something so if there's a rock aiming at the moon, it's most likely still just going to hit the moon. So that's not enough to account for the difference. And remember, the both sides of the moon. Like the earth gravity protects the moons, like this side of the moon, maybe, no? No, no, it's not a big enough effect.

And so it's a big mystery. You know, there's a lot of speculation that maybe there's more like tectonic activity on the front side of the moon, which is sort of smoothing it over. Remember we talked about Europa, that weird moon that has almost no craters. on it that are older than like 10 or 20 years old because there's a lot of resurfacing like stuff coming up and making a new surface. It could be that that's happening more quickly on the front side of the moon than the backside, but people don't really understand like why would that be? So there's some interesting mysteries there. It's like squishier on this side. Yeah, yeah. It's sort of getting refreshed, right? Like the near side of the moon gets its

skin scrubbed. It gets a spa treatment more often. I think the moon is just thinking like, you know what, nobody's going to look at my backside. Nobody cares. There's nobody back here. I'm just going to let it go. Yeah. And folks, this is your motivation. You know, keep your hygiene spherical. Keep your back end. Agne free. Yeah, there's hygiene advice from a scientist and a cartoonist. That's definitely who you want to be listening to. So why do you think there's more churn or more like volcanic activity on this side? Is it related to the fact that it's being it's closer to the earth it could be right i mean we're talking about how the moon is formed and the internals of it and what's going on inside and is it still hot enough to like flow and move

around um but it's it's something we've only recently really started to explore and to understand so it's still a question lunar scientists don't know the answer to this as far as i'm aware so it's it's an open question and you know until recently we didn't know basic stuff about the moon like does it have a strong magnetic field and you know why are there pockets of magnetism here and there and so So, you know, even though we went to the moon 50 years ago, we haven't been back very much. And so there's a lot of questions we just don't have answers to. You know, I think people who study the moon are officially like to be called moonies. Well, you're in charge of naming.

So if they're not called that, if they weren't called that before, they are now. All right. So that's the far side of the moon. And, Daniel, is it somewhere that we want to go or would be interesting to go to or, you know, for vacation or for signs? I wouldn't recommend it for vacation. but it is interesting just because it's not well explored, which means there's always an opportunity for surprises, right? Which is sort of my whole philosophy about science.

It's like science is about exploration. You can think you know what something's going to do. You can think you know what something's going to look like. You can think you, you know whether there are particles there. But until you go and look, you haven't given yourself the opportunity to be surprised by the universe. And so it's definitely worth exploring because it's also not that far away. And it was in 2019, right?

This year that humans finally landed something on the far side of the moon. Really? That's right, yeah. Just now. Just now. Yeah, just a few months ago, China landed something and took a bunch of pictures and is doing experiments over there. And so it's an interesting place, right?

Like, do we understand how the moon formed? It gives us insights into how planets formed and the early history of the Earth and stuff. It's also not a terrible place to do science because it's shielded by the whole moon from all this noise of radio broadcast and a knowing. podcast hosts and all that stuff, that's spewing stuff out into space. So if you want to build, for example, a radio telescope, that's a really nice, quiet spot. It's like the most you can get away from other people.

Exactly. It's an introverts vacation, exactly. There you go. That's how you market it. But you can only market it to like one introvert at a time. If you speak Russian and want a quiet place with no signal on your phone, the far side of the moon would be. ideal. Yeah, the market for that are super zillionaire Russian introverts, right? Which I imagine there might be a few, right? Doesn't Russia have a bunch of millionaires? Yeah, zillionaire Russian introverts listening to this podcast. We will sell you a ticket to the far side of the moon. That's right. We will tell you how to get there. Exactly. Exactly. But it's one of my favorite kind of

things because people can really grasp it. You can look up at the sky and you can think, you know, it's crazy that my ancestors and my ancestors' ancestors who have all been looking at, you know, at this same thing hanging in the sky and the same side of it too. Also not seen the same thing we don't see. Yeah, exactly. That for thousands of years, no human who had been looking up in the sky had seen the backside of this thing until basically our generation, right, or the generation before us, finally cracked this mystery, finally lifted our eyeballs off the surface so we could see

the other side of this thing, which is right there in our faces. Cool. Well, it's amazing to think there are still mysteries, even as close as the moon, right? There are mysteries everywhere. Not just places that are hard to get to, but just unexplained phenomena in physics. Yeah, yeah, exactly. And that's why physics goes on, right? Because there are always mysteries.

Some people ask me like, you know, are we ever going to figure things out? And I'm pretty sure there's always going to be some person with a question out there. You know, why is this this way? Why isn't it that way? And why does this look different from this other thing? There's always questions to be answered. And there are always interesting insights to be uncovered when you dig into those questions. Each one is like a little thread in the fabric of the universe, which if you tug on it, might unravel and reveal something fascinating.

Yeah, humans are annoying like that, you know, never satisfied. Humans or physicists. Or three-year-old kids. Basically the same. It's one category. It's one category. All right, well, we hope you enjoyed that. And God you to think a little bit about the moon and how it formed and what's out there that we still don't know.

Every time you go out into the night and look up at the night's got. That's right. And if you have questions about something you don't understand, you'd like us to explain, please send them to us at questions at daniel and Jorge.com. And if you are a Russian billionaire with disposable income, let us know. That's right. Send it to money at danielanhorpe.com. See you next time. Thanks for tuning in.

If you still have a question after listening to all these explanations, please. Drop us a line. We'd love to hear from you. You can find us at Facebook, Twitter, and Instagram at Daniel and Jorge, that's one word, or email us at Feedback at Danielandhorpe.com. Thanks for listening, and remember that Daniel and Jorge Explain the Universe is a production of IHeartRadio. For more podcasts from IHeartRadio, visit the IHeartRadio app, Apple Podcasts, or wherever you listen to your favorite shows. In the heat of battle, your squad relies on you.

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And Lenovo, Landauvo. December 29th, 1975, LaGuardia Airport. The holiday rush. Parents hauling luggage, kids gripping their new Christmas toys. Then, everything changed. There's been a bombing at the TWA terminal. Just a chaotic, chaotic scene. In its wake, a new kind of enemy emerged, terrorism.

Listen to the new season of Law and Order Criminal Justice System on the IHeart Radio app, Apple Podcasts, or wherever you get your podcasts. My boyfriend's professor is way too friendly, and now I'm seriously suspicious. Wait a minute, Sam. Maybe her boyfriend's just looking for extra credit. Well, Dakota, luckily, it's back to school week on the OK Storytime podcast, so we'll find out soon. This person writes, my boyfriend's been hanging out with his young professor a lot. He doesn't think it's a problem, but I don't trust her. Now he's insisting we get to know each other, but I just want her gone. Hold up. Isn't that against school policy? That seems inappropriate.

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