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Speaker 1: Hey, Daniel, do your days feel longer or shorter as

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Speaker 1: you get older?

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Speaker 2: Are you saying I'm old?

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Speaker 1: Okay, No, I'm saying you're older, which is an objective

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Speaker 1: fact about the universe and time.

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Speaker 2: Well, you know, as I get older, I'm sleeping less

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Speaker 2: and that definitely makes my days feel longer because I'm

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Speaker 2: awake for more hours.

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Speaker 1: Even are you counting naps, Katie?

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Speaker 2: Don't tell everyone that I nap in my office during

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Speaker 2: the workday, even while being paid as a university professor.

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Speaker 1: That's a humble brag if I've ever heard one. And also,

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Speaker 1: you just told everyone.

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Speaker 2: Now, Oh, I think I'm getting too old for this

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Speaker 2: whole thing. Hi. I'm Daniel. I'm a particle physicist and

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Speaker 2: a professor at UC Irvine, and I get paid whether

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Speaker 2: I nap or not.

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Speaker 1: I am Katie. I am a professional nap or I

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Speaker 1: am so good at naps you wouldn't even believe it.

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Speaker 1: I also run a podcast called Creature Feature. I am

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Speaker 1: a biology educator.

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Speaker 2: Hmmm, And if you ever had an episode about naps

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Speaker 2: in the animal world, I actually have.

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Speaker 1: Like there's a lot of animals that do sleep in

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Speaker 1: weird ways, like little like micro naps that birds do

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Speaker 1: where they do like little tiny, itty bitty naps throughout

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Speaker 1: the day in order to stay alert, or like weird

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Speaker 1: giraffe sleeping schedules, where it's like they sleep in these

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Speaker 1: weird chunks and wake up throughout the night but sleep

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Speaker 1: like a lot. It's very interesting the idea of this,

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Speaker 1: like you know, sleep during the night, bewake during the day,

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Speaker 1: and sleep in a solid chunk is very much just

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Speaker 1: like a human quirk, right, A lot of animals sleep differently.

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Speaker 2: Well, I wonder about that with my dog. I never

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Speaker 2: find him sleeping in the same place in the morning

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Speaker 2: as he went to sleep in the evening, and I wonder, like,

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Speaker 2: does he have a night sleep? Is he just like

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Speaker 2: napping a bunch, because he also like sleeps most of

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Speaker 2: the day. So what is my dog doing in the middle.

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Speaker 1: Of the night, king he's online on dog Internet.

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Speaker 2: No, I mean recording his own podcast, wondering what I'm

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Speaker 2: doing rough stuff.

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Speaker 1: Yeah, there is an idea that human beings are not

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Speaker 1: necessarily meant to just sleep throughout the night, that when

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Speaker 1: we had natural light and slept sort of just in

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Speaker 1: piles of humans inside of caves or something that we

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Speaker 1: would wake up in intervals during the night, because we

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Speaker 1: have a sleep cycle right where we enter deep sleep

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Speaker 1: and then come out of it and then re enter

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Speaker 1: deep sleep. So the idea is that it might actually

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Speaker 1: be natural for us to wake up a few times

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Speaker 1: throughout the night and then fall back asleep, but that

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Speaker 1: we're sort of forced into a more rigid schedule with

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Speaker 1: our sleep and not now during the day and things

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Speaker 1: like that.

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Speaker 2: Well, what is natural about being a human is wondering

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Speaker 2: about how the universe works, and so welcome to the

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Speaker 2: podcast Daniel and Jorge Explain the Universe, a production of

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Speaker 2: iHeartRadio in which we try to do just that, dig

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Speaker 2: into the fundamental mechanisms of the universe, the tiniest particles,

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Speaker 2: the largest planets, the strangest black holes, and the weirdest

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Speaker 2: twists in the nature of the universe and space and time.

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Speaker 2: We want to understand how everything works, from the tiniest

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Speaker 2: little bits to the beautiful emergent phenomena that guide and

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Speaker 2: shape our daily lives, including the patterns of day and

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Speaker 2: night that control how tired, how sleepy we feel, and

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Speaker 2: how long we are awake. Katie, how long do you

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Speaker 2: sleep every night?

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Speaker 1: I know a lot of people can function with little sleep.

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Speaker 1: I need a lot of sleep to be coherent, so

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Speaker 1: I sleep maybe eight hours every night, and then unless

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Speaker 1: I have enough coffee, I will want like an hour

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Speaker 1: nap during the day. So that's nine hours of sleep

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Speaker 1: every day, or eight hours plus coffee.

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Speaker 2: I'm so glad to hear you're such a robust sleeper.

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Speaker 2: But sleeping is very important to our sense of well

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Speaker 2: being and to our ability to function and to understand

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Speaker 2: the universe. And our sleep patterns, of course, come from

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Speaker 2: the basic structure and dynamics of the solar system, the

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Speaker 2: Earth moving around the Sun, the way it spins. All

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Speaker 2: of this. Shapes are seasons, shapes are daily cycles. It's

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Speaker 2: really physics that sets the context for our entire lives.

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Speaker 1: It really is amazing how the day night cycle has

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Speaker 1: shaped the behavior of every living animal that has any

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Speaker 1: kind of photo receptor on its body. Like there's this

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Speaker 1: mass migration of plankton every day every night where like

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Speaker 1: during the night, all these little tiny, itty bitty microscopic

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Speaker 1: organisms come up from the depths of the ocean to

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Speaker 1: the surface because they are trying to evade per dation

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Speaker 1: during the daylight. So this day night cycle controls like

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Speaker 1: the largest mass migration that happens every day. And then

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Speaker 1: you know, of course it affects humans, but every animal's

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Speaker 1: behavior is impacted by this day night cycle and by

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Speaker 1: how many hours the sun is out, how many hours

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Speaker 1: the moon is out, and then the in between, like

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Speaker 1: animals that are crepuscular are there during dawn and dusk.

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Speaker 1: So it is really like all the behaviors of animals

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Speaker 1: to be so different if the Earth just was like

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Speaker 1: a little further from the Sun or a little closer,

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Speaker 1: a little smaller. You know, of course there would be

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Speaker 1: other factors that would change if we were closer to

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Speaker 1: the Sun or further from the Sun.

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Speaker 2: And at the root of it is physics, right, Physics

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Speaker 2: determines how fast the Earth spins and how long it

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Speaker 2: takes to go around the Sun. And as I'm always

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Speaker 2: saying that when we dig into the details of how

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Speaker 2: the universe works, what we're really learning about is the

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Speaker 2: context of our lives. We learn about where we are

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Speaker 2: the universe in time and in space, why we are here,

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Speaker 2: how it is that we ended up here, and how

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Speaker 2: long we should expect to be here, and for these

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Speaker 2: circumstances that we find so fundamental. So essential to our

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Speaker 2: lives how long we can rely on them to continue?

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Speaker 1: Are you telling me that night could just go away?

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Speaker 1: Because I would be so sad? I really, I really

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Speaker 1: like my sleep.

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Speaker 2: Well, a basic part of our experience here on Earth

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Speaker 2: is the night in days cycle. And it seems like

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Speaker 2: something fundamental, something that comes from the very spin of

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Speaker 2: the earth, something that probably has been unchanging for thousands

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Speaker 2: or millions or maybe even billions of years. But today

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Speaker 2: in the podcast, we're going to dig into exactly that question.

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Speaker 2: So on today's episode we'll be asking the question, is

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Speaker 2: the length of a day changing?

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Speaker 1: Does this mean we could all live longer? Because if

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Speaker 1: a day is longer, then you know we live longer, right,

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Speaker 1: That's how it works.

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Speaker 2: Well, if it day is longer, you might live fewer days, right,

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Speaker 2: even though which day is longer? If you want to

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Speaker 2: live more days, you need shorter days, right, right? Living

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Speaker 2: any longer just changing the units.

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Speaker 1: But if you change the units psychologically, does that make

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Speaker 1: a difference. I know, we got to get into what

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Speaker 1: people think about this topic. But there is this really

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Speaker 1: interesting phenomenon where people have studied what it's like to

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Speaker 1: be in a cave for a long period of time

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Speaker 1: because you do not have any input in terms of

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Speaker 1: what time of day it is, so you don't get

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Speaker 1: any kind of sunlight, you don't get any moonlight, and

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Speaker 1: most importantly, you get no change and you get no

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Speaker 1: change in temperature. It's just total stasis and people completely

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Speaker 1: lose track of time. They have no idea how long

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Speaker 1: they've been in there. Like there is a guy who

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Speaker 1: I think massively underestimated how much time he had been

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Speaker 1: in that cave.

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Speaker 2: There's that French guy. He went into a cave for

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Speaker 2: a few months and had no information about how time

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Speaker 2: was passing. And when he came out and asked him

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Speaker 2: how many days have passed, and he was a month

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Speaker 2: off after just three months.

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Speaker 1: Yeah, yeah, I think he had like underestimated it by

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Speaker 1: a month thout the time and there was shorter so

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Speaker 1: I guess. Yeah, but our perception of the sun cycle

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Speaker 1: may actually change how much we perceive sort of time,

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Speaker 1: So you know, that's very interesting. But yeah, I don't know.

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Speaker 1: I'm really curious to find out about this because that's

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Speaker 1: so interesting. I don't know if a day is changing,

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Speaker 1: what do people think?

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Speaker 2: Well, in some sense, units are irrelevant, right, you live

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Speaker 2: the same amount of time, and no matter whether days

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Speaker 2: are longer or shorter. But you're right, it does psychologically

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Speaker 2: make a difference. I mean, you run faster in centimeters

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Speaker 2: per second than you do in meters per second. It's

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Speaker 2: the same speed.

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Speaker 1: The instant way to gain more fitness, to be more fit,

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Speaker 1: just change your units.

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Speaker 2: My family is a tradition that when we go on

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Speaker 2: vacation within the United States, we pretend we're in a

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Speaker 2: foreign country where the exchange rate is different, so everything

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Speaker 2: seems cheaper because it makes us relax smaller on vacation, like, oh,

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Speaker 2: you know it cost ten dollars, that's only five dollars

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Speaker 2: in vacation dollars.

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Speaker 1: Hey, yeah, so yeah, it's I have food money, which

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Speaker 1: is not real money. Like I'm buying food. I need

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Speaker 1: this for my body. It's not real money. It's food money.

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Speaker 2: So sometimes these definitions do change the way we experience

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Speaker 2: these things. But on today's episode, we're interested in a

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Speaker 2: deeper question, which is about the rotation of the earth

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Speaker 2: itself and whether that is changing. So I was curious

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Speaker 2: about whether people out there had thoughts on this question.

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Speaker 2: So I went out there to ask our group of

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Speaker 2: volunteers if they thought the length of a day was changing.

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Speaker 2: Before you hear these answers, think about it for a

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Speaker 2: second yourself. What do you think about the possibility that

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Speaker 2: the Earth's rotation could be changing with time. Here's what

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Speaker 2: our volunteer had to say.

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Speaker 3: As far as I know, the speed of the rotation

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Speaker 3: of the Earth is going down, so the days are

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Speaker 3: getting longer and longer, but very very slowly.

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Speaker 2: Unfortunately, this time we only have one volunteer response, so

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Speaker 2: you're hearing one single solitary voice.

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Speaker 1: Guys, you got to get in here and you got

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Speaker 1: to start making puns, because that's you'll know. Daniel will

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Speaker 1: definitely read your answer. If you throw a pun in there,

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Speaker 1: or an honest engagement with the question at hand, that

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Speaker 1: might also be good.

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Speaker 2: If you'd like to join this group for future episodes,

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Speaker 2: please don't be shying right to me two questions at

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Speaker 2: Daniel Atjorhan dot com. You might be the single solitary

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Speaker 2: voice on a future episode, and if.

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Speaker 1: You are, you win a prize, and that prize is

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Speaker 1: a little thumbs up. Can you hear it? I'm giving

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Speaker 1: it right now? Yeah. Yeah, So I guess like I

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Speaker 1: understand that if I roll a ball right, it'll stop

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Speaker 1: rolling right, it will lose momentum. Uh. The Earth is

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Speaker 1: more or less a huge ball. The way I understand

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Speaker 1: it is the reason we keep moving around and rotating

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Speaker 1: is because of things like the sun. Like we are

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Speaker 1: orbiting the sun, and so that doesn't seem like that

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Speaker 1: should change unless the Sun changes, and then our other rotation,

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Speaker 1: rotating around our axis, I thought had something to do

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Speaker 1: with both the Sun and maybe like our molten core.

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Speaker 1: I gotta admit to you I have not thought too

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Speaker 1: much about it for a while.

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Speaker 2: Well, the first step is to figure out what exactly

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Speaker 2: is it we're talking about, because it turns out that

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Speaker 2: the definition of a day itself is a little bit

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Speaker 2: slippery and involves a lot of the things that you mentioned.

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Speaker 2: The most boring definition of a day is just like

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Speaker 2: a certain number of seconds. The definition of a second,

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Speaker 2: of course, just comes from how long it takes a

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Speaker 2: caesium atom to do like nine trillion oscillations. So that's

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Speaker 2: defined in terms of some like physical standard. And then

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Speaker 2: one definition of a day is just eighty six thousand,

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Speaker 2: four hundred seconds, just thirty six hundred seconds per hour

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Speaker 2: times twenty four hours, and that gives you a definition

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Speaker 2: of a day, but that's just like a fixed number

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Speaker 2: of seconds. It has no relationship to like how fast

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Speaker 2: the Earth is actually spinning. It's just like historically this

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Speaker 2: is roughly what a day was like.

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Speaker 1: They should have named that show twenty four eighty six thousand,

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Speaker 1: four hundred, because that's a bigger number and therefore cooler.

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Speaker 1: You can have more opportunities to build tensions.

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Speaker 2: Astronomically speaking, we might think of a day as what

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Speaker 2: astronomers call a solar day, which is the time between

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Speaker 2: high noons, Like when the Sun is exactly above you

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Speaker 2: in the sky. How many seconds between that and the

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Speaker 2: next time it happens. And that makes a lot of sense,

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Speaker 2: and it sort of aligns with what we imagine to

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Speaker 2: be a day. But there's a subtle wrinkle there, which

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Speaker 2: is that in the time it takes for the Earth

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Speaker 2: to spin, we're also moving around the Sun. So one

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Speaker 2: solar day is actually slightly more than one full rotation.

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Speaker 2: If you imagine, like the direction you're facing on the

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Speaker 2: first noon, then when the Earth has gone around the Sun,

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Speaker 2: you're now not facing the same direction on the next noon.

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Speaker 2: Because the Earth rotates in the same direction it moves.

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Speaker 2: You have to point at a slightly different angle, so

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Speaker 2: it's slightly more than one actual rotation of the Earth

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Speaker 2: is a solar day.

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Speaker 1: I'm having flashbacks to geometry class when we learned like

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Speaker 1: arcs and stuff, and it's like, oh, when will I

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Speaker 1: need to know this? When will this come in handy?

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Speaker 2: So the most precise definition of a day comes from

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Speaker 2: a stellar day, which is relative to like the fixed stars,

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Speaker 2: which they also move, of course, but they move on

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Speaker 2: a much longer timescale, so we can imagine that they're fixed.

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Speaker 2: So the stellar day is like how long it takes

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Speaker 2: the Earth's surface to rotate one time. It's not relative

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Speaker 2: to the motion of the Earth around the Sun. It's

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Speaker 2: more independent in that sense. Or from the surface of

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Speaker 2: the Earth, you can say how long it takes for

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Speaker 2: a star to return to the same position in the sky.

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Speaker 2: That's a stellar day.

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Speaker 1: Okay, that seems like it would be the most consistent. Also,

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Speaker 1: it just sounds really cheerful, like have a stellar days.

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Speaker 2: It does. And you pointed out something else earlier, which

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Speaker 2: is like, all this depends on the motion of stuff

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Speaker 2: through space and specifically the Earth's spin. Right, the Earth

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Speaker 2: is spinning as it goes around the Sun, and A

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Speaker 2: basic fact we learn in physics is conservation of Angland momentum.

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Speaker 2: In our universe, momentum is conserved, which means if you

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Speaker 2: have a certain amount of momentum and you do a

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Speaker 2: bunch of stuff, things bounce into each other or off

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Speaker 2: walls or whatever, and you add up the momentum before

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Speaker 2: and after, it has to be the same. That comes

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Speaker 2: from a deep symmetry in the universe. Space translation that

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Speaker 2: it doesn't matter where in the universe you do an

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Speaker 2: experiment or where your solar system is, laws of physics

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Speaker 2: should be the same. We also conserve Angler momentum, which

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Speaker 2: is related to how fast things rotate and how their

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Speaker 2: mass is distributed. And Angler momentum conservation also comes from

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Speaker 2: a deep symmetry the universe. In this case, it's the

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Speaker 2: rotational invariance. The fact that there's no preferred direction in

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Speaker 2: the universe is why we have angular momentum conservation. We

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Speaker 2: have a whole bunch of episodes about Nuther's theorem and

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Speaker 2: the connection between symmetries and conservation laws, but in this case,

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Speaker 2: it suggests to us that like, hey, the Earth is

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Speaker 2: out there in space not really interacting with much, shouldn't

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Speaker 2: it spin be constant if there's conservation of angular momentum.

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Speaker 1: I'm assuming that it is actually interacting with stuff though.

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Speaker 2: Yeah, so that simple model would suggest the Earth is

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Speaker 2: spinning and it doesn't interact with other stuff, and so

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Speaker 2: its spin should be the same. You set something spinning

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Speaker 2: in space, you come back a billion years later, it

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Speaker 2: should still be spinning. But there's two important caveats. One

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Speaker 2: is the one you mentioned. The Earth actually does interact

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Speaker 2: with other stuff. There's not just the Earth and the Sun.

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Speaker 2: There's Jupiter, there's the moon. All these other little tugs

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Speaker 2: can change the rotation of the Earth. We only have

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Speaker 2: conservation of angular momentum within a closed system. If you

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Speaker 2: have a force on them objects, or technically to have

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Speaker 2: a torque on an object from something else, then you

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Speaker 2: can change its spin. So, for example, you set something

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Speaker 2: spinning out in space, it will spin forever, but then

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Speaker 2: if you put your finger on it, you can slow

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Speaker 2: it down. That anglementum is overall conserved. It gets transferred

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Speaker 2: to you or to whoever's doing the tug in. But

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Speaker 2: in this case there are things tugging and tweaking the Earth.

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Speaker 1: It's like when you roll a ball, it slows down

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Speaker 1: not because that is, you know, the natural order of

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Speaker 1: things to slow down, but it is being slowed down

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Speaker 1: by like the ground and the air, and.

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Speaker 2: In this case it's mostly the moon. And we'll dig into.

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Speaker 1: Ooh, the moon. I knew it was the moon's fault.

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Speaker 2: And the second reason why the simple model of the

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Speaker 2: Earth spinning the same way in space forever doesn't work

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Speaker 2: is that the Earth is not a simple ball. The

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Speaker 2: Earth has layers. There's the atmosphere, there's the surface, there's

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Speaker 2: the inner layers, there's the ocean. There's all sorts of

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Speaker 2: stuff going on. We're actually interested in what affects the

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Speaker 2: length of a day. Is only the motion of the surface, right,

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Speaker 2: So the Earth is made of these different shells that

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Speaker 2: can spin at different speeds, and only one of them

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Speaker 2: determines the length of a day. And so those things

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Speaker 2: interact and there's coupling between them that can affect how

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Speaker 2: quickly the surface spins, which affects the length of a day.

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Speaker 1: Okay, so we may be getting slowed down by our

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Speaker 1: own layers here on Earth, or also the moon, which

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Speaker 1: begs the question do we need to get rid of

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Speaker 1: the moon. Yeah, let's take a break. I'm gonna just

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Speaker 1: pull out this corkboard I have about Katie's big plan

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Speaker 1: to destroy the Moon, which is very normal, and then

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Speaker 1: we will return and I'm sure I will have convinced

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Speaker 1: Daniel of my plan. So we're back. You know, let's

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Speaker 1: just put a pin in that destroy the Moon plan,

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Speaker 1: and let's talk more about what exactly are the factors

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Speaker 1: impacting the Earth's movements and what could be getting in

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Speaker 1: our way of having a normal stellar day.

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Speaker 2: I'm not going to let you do that, Katie. I'm

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Speaker 2: not going to let you just like try to normalize

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Speaker 2: this concept of destroying the Moon and moving on and

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Speaker 2: pretending it's just like part of the discourse. A totally

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Speaker 2: reasonable question. Can I ask, No, why didn't realize you

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Speaker 2: were an anti moonight?

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Speaker 1: I'm just asking questions, Daniel. I'm not I'm a moon centrist.

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Speaker 2: Like questions like should we lock Katie up and torture

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Speaker 2: her dog? I mean, some questions happen the obvious answer

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Speaker 2: of no.

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Speaker 1: Well, the pro moon crowd sugar is violent, is all

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Speaker 1: I'm going to say.

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Speaker 2: You know, we answered a question from a listener about

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Speaker 2: destroying the moon, and our answer was a definitive, Please

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Speaker 2: don't do that anybody, and it applies also to who

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Speaker 2: guest hosts, okay.

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Speaker 1: Because of the backwash, probably right, yeah, right now. I

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Speaker 1: like the moon. I like it. It's like a big

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Speaker 1: glowing cracker, and I like that about it. That's a

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Speaker 1: more right. And the Moon's not destroyed and the chunks

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Speaker 1: don't hit your eye, that's a more look, I mean.

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Speaker 2: You make it an Italian joke, all right. But the

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Speaker 2: Moon does play a big role in the rotation speed

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Speaker 2: of the Earth. Because the Earth is not just a

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Speaker 2: ball floating in space spinning on its own. We're in

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Speaker 2: a relationship with another big ball out there in space,

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Speaker 2: and the Moon is not that small a ball. It

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Speaker 2: has a lot of gravitational impact on the Earth.

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Speaker 1: It's like how you know if you have a kid,

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Speaker 1: just because they're small doesn't mean they're not gonna affect

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Speaker 1: your day.

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Speaker 2: In this case, the moon has a pretty strong gravitational

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Speaker 2: effect on the Earth, but not in the way you

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Speaker 2: might be thinking. We're all familiar with the tidal forces.

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Speaker 2: How the moon pulls on some of the ocean bodies

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Speaker 2: and makes water deeper and shallower in some respects. That's

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Speaker 2: because of tidal forces. The moon pulls on the Earth

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Speaker 2: with its gravity, and some parts of the Earth are

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Speaker 2: closer to the Moon than other parts, which means they

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Speaker 2: get stronger gravity from the Moon.

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Speaker 1: Yeah, tides go in, tides go out. You can explain that.

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Speaker 2: You can't explain that absolutely. That's not a mystery of science.

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Speaker 2: In particular, that tends to pull the Earth and its

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Speaker 2: oceans into more of a football shape because it's pulling

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Speaker 2: harder on the closer bits and more gently on the

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Speaker 2: further bits. So we're all familiar with the ocean tides,

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Speaker 2: but there are also land tides. The Moon is doing

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Speaker 2: the same thing to the Earth as it's doing to

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Speaker 2: its oceans. It's doing the same thing to the crust,

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Speaker 2: to the mantle, to the actual body of the Earth

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Speaker 2: as happens to the ocean. So we have a whole

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Speaker 2: episode about land tides. They're not as dramatic as ocean

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Speaker 2: tides because the Earth itself is not as flexible as

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Speaker 2: the oceans are squishable and sloshable. That's a technical turn.

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Speaker 1: They have washability, but they are there.

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Speaker 2: As the Moon goes around the Earth, it changes the

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Speaker 2: shape of the Earth. It's making the Earth more of

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Speaker 2: a football, and that football is pointing towards the Moon.

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Speaker 1: So is that like it is actually like moving things,

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Speaker 1: like slightly moving tectonic plates or something, or is it

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Speaker 1: more that it is just the entire crust is sort

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Speaker 1: of warping.

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Speaker 2: Yeah, the entire crust is sort of warping. But the

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Speaker 2: crust is also resisting that. Right. If the Earth was

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Speaker 2: made of diamond, than the Moon would have a much

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Speaker 2: smaller impact. So the impact of the Moon on the

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Speaker 2: Earth's shape depends on the structure of the Earth and

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Speaker 2: this tension in there, and there's friction in there because

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Speaker 2: what essentially is happening is that it's squeezing the Earth.

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Speaker 2: This is one way that you can keep an object

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Speaker 2: hot just through tidal forces. Some of the moons surrounding Jupiter,

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Speaker 2: for example, have such strong tidal forces that they're kept

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Speaker 2: hot like they have lava on the inside because the

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00:22:00,359 --> 00:22:04,840
Speaker 2: internal friction generated by Jupiter like effectively massaging its moons.

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Speaker 2: In this case, the Moon is massaging the Earth and

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Speaker 2: in doing so is transferring heat to the Earth, and

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Speaker 2: so the rotational system is losing that energy. So what's

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Speaker 2: happening is the Moon's rotation around the Earth is becoming slower,

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Speaker 2: and the Earth and the Moon's rotations are also slowing down.

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Speaker 1: So the heat that is generated by the Earth sort

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Speaker 1: of going a little football shaped. That slows down the

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Speaker 1: rotation of the Earth and the Moon.

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Speaker 2: Yeah, it slows down the rotation of both of them

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Speaker 2: around their axis, and of the Moon around the Earth,

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Speaker 2: and it makes the Moon drift further away because it's

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Speaker 2: going more slowly. So the Moon very gradually is getting

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Speaker 2: further away because there's less energy in that rotation as

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Speaker 2: that energy is getting transferred into the Earth and the Moon.

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Speaker 1: The heat energy comes from somewhere, and it is coming

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Speaker 1: from what would have been the rotational energy.

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Speaker 2: And this is how tidal locking happens. In many scenarios

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Speaker 2: of two bodies will be tidally locked, so they're always

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Speaker 2: facing each other with the same side. The Moon is

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Speaker 2: already tidly locked to the Earth, and given enough time,

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Speaker 2: the Moon will slow down the rotation of the Earth. Eventually,

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Speaker 2: the rotation of the Earth will take twenty eight of

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Speaker 2: our current days, So the Moon is having a pretty

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Speaker 2: strong effect on the rotation of the Earth.

438
00:23:23,880 --> 00:23:26,640
Speaker 1: I hate that. I don't like that at all, Daniel,

439
00:23:26,800 --> 00:23:29,320
Speaker 1: because I don't want to wait a whole month to

440
00:23:29,880 --> 00:23:32,720
Speaker 1: go to bedtime, because I love bedtime and I love sleeping.

441
00:23:33,520 --> 00:23:35,560
Speaker 1: I also don't want to wait twenty eight days to

442
00:23:35,600 --> 00:23:38,080
Speaker 1: wake up in the morning because I'm gonna, really, I'm

443
00:23:38,080 --> 00:23:43,119
Speaker 1: gonna be so angry and so like, don't even you

444
00:23:43,280 --> 00:23:46,160
Speaker 1: dare speak to me until I've had that monthly coffee.

445
00:23:46,320 --> 00:23:48,800
Speaker 2: I know. Wouldn't it be weird if a year was

446
00:23:48,920 --> 00:23:51,920
Speaker 2: like twelve days long? That'd be really strange. Yeah, it'd

447
00:23:51,960 --> 00:23:54,040
Speaker 2: be like your birthday every couple of weeks.

448
00:23:54,920 --> 00:23:56,840
Speaker 1: I feel like we would have to undergo some kind

449
00:23:56,880 --> 00:24:00,480
Speaker 1: of radical evolution. I mean, everything would at the point,

450
00:24:00,600 --> 00:24:03,240
Speaker 1: how long is that going to take, Daniel, because I

451
00:24:03,320 --> 00:24:03,880
Speaker 1: need a plan.

452
00:24:04,720 --> 00:24:08,919
Speaker 2: It's a pretty slow process. Actually, every century it affects

453
00:24:08,960 --> 00:24:12,639
Speaker 2: the rotation of the Earth by two point three milliseconds.

454
00:24:12,920 --> 00:24:15,919
Speaker 2: So this is a pretty small effect, although over you know,

455
00:24:16,000 --> 00:24:20,199
Speaker 2: cosmological time scales, it's dramatic. Just after the Moon was

456
00:24:20,280 --> 00:24:23,359
Speaker 2: formed and a huge collision of some proto planet with

457
00:24:23,680 --> 00:24:25,960
Speaker 2: the pre Earth, we think that the rate that the

458
00:24:26,000 --> 00:24:29,040
Speaker 2: Earth was spinning was about six hours for one rotation,

459
00:24:29,440 --> 00:24:31,920
Speaker 2: so day was just six hours long, and now it's

460
00:24:31,960 --> 00:24:34,560
Speaker 2: around twenty four hours long, and eventually it'll be twenty

461
00:24:34,640 --> 00:24:38,040
Speaker 2: eight days long. All that is getting slowed down gradually

462
00:24:38,119 --> 00:24:38,680
Speaker 2: by the Moon.

463
00:24:39,119 --> 00:24:41,560
Speaker 1: Do you think there will still be life on the

464
00:24:41,600 --> 00:24:43,920
Speaker 1: planet at that point or are we going to be

465
00:24:44,560 --> 00:24:48,760
Speaker 1: undergoing some problems that would make it difficult for life

466
00:24:48,800 --> 00:24:50,560
Speaker 1: to survive that situation.

467
00:24:50,880 --> 00:24:53,280
Speaker 2: This is deep in the future, and so between now

468
00:24:53,320 --> 00:24:56,280
Speaker 2: and then we could get hit by comets. The Sun

469
00:24:56,359 --> 00:24:58,800
Speaker 2: will expand and it will get brighter. So a lot

470
00:24:58,840 --> 00:25:01,480
Speaker 2: of things are going to change. Any difficulty to extrapolate

471
00:25:01,800 --> 00:25:03,680
Speaker 2: that far in the future. I mean, if we even

472
00:25:03,720 --> 00:25:07,000
Speaker 2: survive the next ten years without blowing ourselves to smithereens right,

473
00:25:07,480 --> 00:25:09,080
Speaker 2: But this is definitely one effect.

474
00:25:09,200 --> 00:25:11,800
Speaker 1: So you're an optimist, is what you're saying. You're an optimist.

475
00:25:13,440 --> 00:25:16,080
Speaker 2: I'm saying we don't know, We can't know, and I

476
00:25:16,119 --> 00:25:19,200
Speaker 2: think sometimes not knowing is better than knowing. Yeah, I

477
00:25:19,240 --> 00:25:21,360
Speaker 2: don't know. That makes me an optimist or a pessimist.

478
00:25:24,560 --> 00:25:27,200
Speaker 1: Okay, So the Moon is interfering with our spin here.

479
00:25:27,880 --> 00:25:32,399
Speaker 1: It's a harshing our mellow or maybe enhancing our mellow.

480
00:25:32,440 --> 00:25:34,960
Speaker 1: I don't know. I'm pro moon. Don't worry about that.

481
00:25:35,760 --> 00:25:39,640
Speaker 1: But is there anything else that is going on that

482
00:25:39,840 --> 00:25:42,400
Speaker 1: is affecting our jam around the Sun?

483
00:25:42,840 --> 00:25:45,159
Speaker 2: So many other things are going on, and some of

484
00:25:45,160 --> 00:25:48,399
Speaker 2: them are fighting back against the powers of the Moon. So,

485
00:25:48,480 --> 00:25:52,520
Speaker 2: for example, our oceans and climate change and the glaciers,

486
00:25:52,560 --> 00:25:55,080
Speaker 2: all of these things are working in the other direction

487
00:25:55,440 --> 00:25:58,439
Speaker 2: to actually speed up the rotation of the Earth.

488
00:25:58,920 --> 00:26:03,760
Speaker 1: Whoa, So so there are anti moon forces on Earth? Yes,

489
00:26:03,800 --> 00:26:07,439
Speaker 1: all right, So I get why the oceans are anti

490
00:26:07,480 --> 00:26:10,840
Speaker 1: moon because the Moon's always messing with them. But all right,

491
00:26:10,920 --> 00:26:14,800
Speaker 1: so we've got glaciers that are melting. How does that

492
00:26:15,000 --> 00:26:16,040
Speaker 1: increase our spin?

493
00:26:16,359 --> 00:26:18,960
Speaker 2: So even though angular momentum has to be conserved, that

494
00:26:19,000 --> 00:26:22,040
Speaker 2: doesn't mean necessarily that the spin velocity of the surface

495
00:26:22,080 --> 00:26:24,480
Speaker 2: has to be conserved. In the same way that if

496
00:26:24,480 --> 00:26:27,480
Speaker 2: you're a figure skeater and you have a fixed angular momentum,

497
00:26:27,600 --> 00:26:30,359
Speaker 2: you can pull your arms into be going faster. What

498
00:26:30,440 --> 00:26:33,320
Speaker 2: you've done is you've changed where your mass is distributed.

499
00:26:33,560 --> 00:26:36,679
Speaker 2: And since angular momentum depends not just on your spin velocity,

500
00:26:37,000 --> 00:26:40,679
Speaker 2: but on how that mass is distributed from the spin axis. Like,

501
00:26:40,760 --> 00:26:43,399
Speaker 2: the more mass you have far away from a spin axis,

502
00:26:43,400 --> 00:26:45,760
Speaker 2: the more angular momentum you have. So if you bring

503
00:26:45,800 --> 00:26:48,080
Speaker 2: that mass in closer to the axis, you have to

504
00:26:48,119 --> 00:26:51,320
Speaker 2: be spinning faster to have the same angular momentum. And

505
00:26:51,400 --> 00:26:54,159
Speaker 2: so if you can somehow make the Earth more compact,

506
00:26:54,240 --> 00:26:56,600
Speaker 2: then you can make it spin faster. One way to

507
00:26:56,640 --> 00:26:59,320
Speaker 2: do that is to bring massive stuff that's high up

508
00:26:59,560 --> 00:27:03,800
Speaker 2: i e. Frozen water in glaciers down lower. And so

509
00:27:03,920 --> 00:27:06,320
Speaker 2: for example, if you take all of the glaciers on

510
00:27:06,480 --> 00:27:09,320
Speaker 2: Earth and all the snow and you melt it and

511
00:27:09,359 --> 00:27:11,920
Speaker 2: you bring it down so closer to the rotation axis

512
00:27:11,960 --> 00:27:15,199
Speaker 2: of the Earth, then that has the effect of speeding

513
00:27:15,320 --> 00:27:16,800
Speaker 2: up the Earth's rotation.

514
00:27:17,200 --> 00:27:20,480
Speaker 1: I see. So you're more evenly distributing that mass because

515
00:27:20,520 --> 00:27:23,840
Speaker 1: like the ocean levels rise, but these very high peaks

516
00:27:24,359 --> 00:27:27,840
Speaker 1: in terms of glaciers lower down. So like now that

517
00:27:28,240 --> 00:27:33,120
Speaker 1: mouse is more evenly distributed, you know, which is bad

518
00:27:33,200 --> 00:27:36,399
Speaker 1: for us, but good if you want to spin really fast.

519
00:27:36,920 --> 00:27:39,119
Speaker 2: Yeah, exactly. Like if you wanted to slow down the

520
00:27:39,160 --> 00:27:41,800
Speaker 2: spin of the Earth, you could build really really tall

521
00:27:41,920 --> 00:27:45,040
Speaker 2: towers and lift a bunch of really big glaciers up

522
00:27:45,080 --> 00:27:47,119
Speaker 2: to the tops of them. That would slow down the

523
00:27:47,160 --> 00:27:49,520
Speaker 2: spin of the Earth. The melting of the glaciers is

524
00:27:49,560 --> 00:27:52,200
Speaker 2: basically the opposite. Says, oh, we already have a bunch

525
00:27:52,200 --> 00:27:55,240
Speaker 2: of these glaciers kind of elevated at the tops of mountains,

526
00:27:55,600 --> 00:27:58,480
Speaker 2: and so let's bring them down as low as we can,

527
00:27:59,040 --> 00:28:01,040
Speaker 2: and that will speed up the spin of the pair.

528
00:28:01,160 --> 00:28:03,720
Speaker 1: I see you've been peeking at my plans for Katie's

529
00:28:03,720 --> 00:28:05,240
Speaker 1: sky a glue.

530
00:28:06,000 --> 00:28:08,080
Speaker 2: There's another effect there, which is the weight of the

531
00:28:08,080 --> 00:28:11,000
Speaker 2: glaciers also changes a little bit the shape of the

532
00:28:11,080 --> 00:28:14,400
Speaker 2: Earth because there's so much ice in the polar regions.

533
00:28:14,560 --> 00:28:16,719
Speaker 2: What happens if that all melts is you get this

534
00:28:16,760 --> 00:28:20,399
Speaker 2: redistribution of ice and you get this post glacial rebound

535
00:28:20,680 --> 00:28:23,520
Speaker 2: where you no longer have this dramatic weight pushing down

536
00:28:23,560 --> 00:28:26,520
Speaker 2: the ground in the polar regions, and so that comes

537
00:28:26,520 --> 00:28:28,520
Speaker 2: back out a little bit. But because it's close to

538
00:28:28,560 --> 00:28:31,240
Speaker 2: the axis, it doesn't affect the spin of the Earth,

539
00:28:31,640 --> 00:28:34,399
Speaker 2: and so overall the effect is to bring more stuff

540
00:28:34,480 --> 00:28:36,280
Speaker 2: closer to the spin axis.

541
00:28:36,640 --> 00:28:40,440
Speaker 1: Okay, so by losing the weight of the poles, would

542
00:28:40,480 --> 00:28:42,200
Speaker 1: that make it go slower faster?

543
00:28:42,640 --> 00:28:45,360
Speaker 2: That makes it go faster, Yeah, because you have more

544
00:28:45,360 --> 00:28:48,160
Speaker 2: weight now closer to the poles. This effect is not

545
00:28:48,240 --> 00:28:50,840
Speaker 2: as big as the effect of the moon. It's like

546
00:28:51,400 --> 00:28:55,360
Speaker 2: negative point six milliseconds per century, where it's remember the

547
00:28:55,400 --> 00:28:59,360
Speaker 2: moon was plus two point three milliseconds per century. So

548
00:28:59,600 --> 00:29:02,320
Speaker 2: over all the long term effect is like one point

549
00:29:02,360 --> 00:29:06,479
Speaker 2: seven milliseconds per century gets added to our day. So

550
00:29:06,520 --> 00:29:09,120
Speaker 2: the moon really is dominating. The effect of the glaciers

551
00:29:09,160 --> 00:29:10,880
Speaker 2: is like a quarter of the effect of the moon.

552
00:29:11,280 --> 00:29:14,640
Speaker 1: Right, And we should not melt all the glaciers. I

553
00:29:14,680 --> 00:29:18,440
Speaker 1: think it is important to state the penguins need them,

554
00:29:18,760 --> 00:29:23,960
Speaker 1: polar bears need them. This is yes, no, no, Let's

555
00:29:24,040 --> 00:29:25,920
Speaker 1: keep the moon where it is. Let's keep the glaciers

556
00:29:25,920 --> 00:29:29,040
Speaker 1: where they is. If we can, like, don't do this.

557
00:29:29,200 --> 00:29:30,960
Speaker 1: But if you do do this, and you melt all

558
00:29:31,000 --> 00:29:34,360
Speaker 1: the glaciers and now you have this like evenly distributed water,

559
00:29:34,400 --> 00:29:37,200
Speaker 1: it doesn't seem like it'd be just as simple as like, well,

560
00:29:37,240 --> 00:29:40,640
Speaker 1: now the Earth's sort of more compact. It's not just

561
00:29:40,640 --> 00:29:43,200
Speaker 1: like pulling your arms in, right if you're an ice skater,

562
00:29:43,240 --> 00:29:45,360
Speaker 1: because it is, water has its own properties.

563
00:29:45,600 --> 00:29:47,840
Speaker 2: Yes, there's a big water cycle on the Earth, and

564
00:29:47,880 --> 00:29:51,040
Speaker 2: the water interacts heavily with the atmosphere, and so the

565
00:29:51,040 --> 00:29:54,040
Speaker 2: moon and the melting of the glaciers and climate change

566
00:29:54,440 --> 00:29:58,040
Speaker 2: sort of dominate the longer term effects, like over centuries. Definitely,

567
00:29:58,120 --> 00:30:00,280
Speaker 2: the length of a day is increasing, but there are

568
00:30:00,280 --> 00:30:02,760
Speaker 2: also much shorter term effects where the Earth is speeding

569
00:30:02,880 --> 00:30:06,040
Speaker 2: up and slowing down due to changes in the atmosphere.

570
00:30:06,240 --> 00:30:08,040
Speaker 2: Think what the Earth is a bunch of shells. You

571
00:30:08,080 --> 00:30:10,440
Speaker 2: have like the inner core, you have the surface, you

572
00:30:10,480 --> 00:30:13,760
Speaker 2: have the atmosphere. If you need to conserve angular momentum,

573
00:30:14,040 --> 00:30:16,000
Speaker 2: you could speed up one of them and slow down

574
00:30:16,040 --> 00:30:19,000
Speaker 2: another one, right the same way that like an astronaut

575
00:30:19,080 --> 00:30:22,120
Speaker 2: in space can change how they're spinning by moving their

576
00:30:22,200 --> 00:30:25,240
Speaker 2: arms around, So some parts of them can be spinning faster,

577
00:30:25,440 --> 00:30:28,000
Speaker 2: some parts of them can be spinning slower. And the

578
00:30:28,040 --> 00:30:31,040
Speaker 2: atmosphere doesn't have to spin at the same rate as

579
00:30:31,080 --> 00:30:31,600
Speaker 2: the earth.

580
00:30:32,080 --> 00:30:36,880
Speaker 1: Right, So that's kind of like how like gyroscopes work. Right,

581
00:30:36,920 --> 00:30:39,840
Speaker 1: you have like different layers and then different spinning, and

582
00:30:39,840 --> 00:30:42,760
Speaker 1: then you get pork and then I don't remember the rest.

583
00:30:43,320 --> 00:30:46,720
Speaker 2: Ah, that's exactly right, And this is a big source

584
00:30:46,760 --> 00:30:49,400
Speaker 2: of like weather on Earth and wind. Right. Wind is

585
00:30:49,440 --> 00:30:52,440
Speaker 2: basically when the atmosphere and the surface are not spinning

586
00:30:52,520 --> 00:30:54,440
Speaker 2: at the same speed, and so you feel it.

587
00:30:54,680 --> 00:30:57,840
Speaker 1: Right like when you're watching clouds move up ahead, it

588
00:30:57,880 --> 00:31:00,720
Speaker 1: does feel like there is a you know, a layer

589
00:31:00,800 --> 00:31:02,560
Speaker 1: moving above us mm hmm.

590
00:31:03,240 --> 00:31:05,360
Speaker 2: And a lot of this is due to the clouds

591
00:31:05,400 --> 00:31:08,200
Speaker 2: and the water cycle like, think about what happens when

592
00:31:08,280 --> 00:31:12,920
Speaker 2: water is moving through its natural progression of evaporation and precipitation.

593
00:31:13,640 --> 00:31:17,480
Speaker 2: When water evaporates, it's going up, right, and so when

594
00:31:17,520 --> 00:31:20,000
Speaker 2: it goes up, it can't be rotating at the same

595
00:31:20,040 --> 00:31:24,440
Speaker 2: speed to conserve angular momentum. It needs to be going slower, right.

596
00:31:24,560 --> 00:31:27,720
Speaker 2: Or think about it another way. If everything was rotating together,

597
00:31:28,280 --> 00:31:31,800
Speaker 2: then things at higher altitudes are actually moving faster because

598
00:31:31,800 --> 00:31:34,280
Speaker 2: they have a longer path, sort of like runners on

599
00:31:34,280 --> 00:31:36,560
Speaker 2: the outside laps of a race have to be moving

600
00:31:36,640 --> 00:31:37,840
Speaker 2: faster to keep up.

601
00:31:38,120 --> 00:31:41,400
Speaker 1: So as water is evaporating, is that because the water

602
00:31:41,560 --> 00:31:45,520
Speaker 1: starts out slower and it's like merging into the high

603
00:31:45,520 --> 00:31:48,360
Speaker 1: speed lane, but at a slower speed than the water

604
00:31:48,400 --> 00:31:51,920
Speaker 1: in the atmosphere? Is that's slowing down the atmosphere exactly.

605
00:31:52,160 --> 00:31:55,840
Speaker 2: And so as water rises, it falls behind because it's

606
00:31:55,880 --> 00:31:59,840
Speaker 2: not moving as fast, right, So it's effectively slowing down

607
00:32:00,040 --> 00:32:03,120
Speaker 2: the atmosphere. And this is why we get hurricanes.

608
00:32:03,400 --> 00:32:06,040
Speaker 1: Oh wow, okay, I mean I was going to say,

609
00:32:06,040 --> 00:32:09,160
Speaker 1: this is just how like traffic works, right, Nobody knows

610
00:32:09,160 --> 00:32:12,280
Speaker 1: how to zipper. Apparently water also doesn't know how to zipper,

611
00:32:12,320 --> 00:32:15,000
Speaker 1: and it slows down all the traffic, But how does

612
00:32:15,000 --> 00:32:16,080
Speaker 1: that cause hurricanes?

613
00:32:16,400 --> 00:32:19,560
Speaker 2: So as water is rising, the direction in which it

614
00:32:19,680 --> 00:32:22,880
Speaker 2: falls behind depends on the direction of the Earth's spin

615
00:32:23,240 --> 00:32:27,160
Speaker 2: and also the latitude the distance from the equator. Stuff

616
00:32:27,160 --> 00:32:29,720
Speaker 2: at the equator is traveling the fastest, and stuff of

617
00:32:29,760 --> 00:32:32,440
Speaker 2: the poles is not moving around the Earth at all,

618
00:32:32,640 --> 00:32:35,800
Speaker 2: just spins in place. So as water rises, some parts

619
00:32:35,840 --> 00:32:39,640
Speaker 2: fall behind more than others because they're traveling at different speeds.

620
00:32:39,640 --> 00:32:42,880
Speaker 2: This is basically how the Corioles effect works, and that's why,

621
00:32:42,920 --> 00:32:45,560
Speaker 2: for example, you get hurricanes going in one direction in

622
00:32:45,560 --> 00:32:48,840
Speaker 2: the northern hemisphere and the other direction on the southern hemistere.

623
00:32:49,040 --> 00:32:52,000
Speaker 2: We have a whole episode about tropical storms and hurricanes

624
00:32:52,080 --> 00:32:54,920
Speaker 2: and even space hurricanes that relates to this.

625
00:32:55,400 --> 00:32:58,120
Speaker 1: But toilets do flush in the same direction no.

626
00:32:58,040 --> 00:33:00,760
Speaker 2: Matter where you are, Yes, they do. I mean, listeners,

627
00:33:00,840 --> 00:33:03,480
Speaker 2: you tell me I've never been to the Sun's hemisphere.

628
00:33:04,160 --> 00:33:07,480
Speaker 2: But the idea is that essentially you have transfer of

629
00:33:07,640 --> 00:33:10,640
Speaker 2: velocity and angle momentum between these two layers, and so

630
00:33:10,680 --> 00:33:14,160
Speaker 2: you can make the atmosphere move slower by loading it

631
00:33:14,240 --> 00:33:16,680
Speaker 2: up with water, where you can make it move faster

632
00:33:16,880 --> 00:33:19,920
Speaker 2: by dumping water. And if the atmosphere is moving faster

633
00:33:20,000 --> 00:33:23,200
Speaker 2: or slower. The surface also moves faster or slower, because again,

634
00:33:23,280 --> 00:33:27,200
Speaker 2: angular momentum is roughly conserved, and so by speeding up

635
00:33:27,200 --> 00:33:30,040
Speaker 2: one layer, you can slow down another layer. And we

636
00:33:30,080 --> 00:33:32,800
Speaker 2: all know, of course how they can transfer angular momentum

637
00:33:32,840 --> 00:33:35,840
Speaker 2: between each other. That's basically a wind. Right when wind

638
00:33:35,920 --> 00:33:38,360
Speaker 2: is blowing across the surface of the Earth, it can

639
00:33:38,400 --> 00:33:41,560
Speaker 2: actually speed up the earth, or if the Earth is

640
00:33:41,600 --> 00:33:45,680
Speaker 2: moving faster, it's leaving the atmosphere behind that also creates wind.

641
00:33:45,880 --> 00:33:48,360
Speaker 2: So our experience of wind and storms, this is like

642
00:33:48,400 --> 00:33:52,160
Speaker 2: the surface and the atmosphere exchanging angular momentum.

643
00:33:52,200 --> 00:33:55,920
Speaker 1: I guess I never thought of the weather as exchanging

644
00:33:56,080 --> 00:33:59,240
Speaker 1: angular momentum. So next time I'm out, I'm gonna be like, wow,

645
00:33:59,720 --> 00:34:03,120
Speaker 1: look at this exchange of angular momentum today. Lovely, isn't it.

646
00:34:03,840 --> 00:34:06,480
Speaker 2: Yeah, Well, this is really what dominates the change in

647
00:34:06,520 --> 00:34:09,240
Speaker 2: the length of a day on the day to day

648
00:34:09,440 --> 00:34:11,759
Speaker 2: or month to month cycle. Like we talked about it

649
00:34:11,760 --> 00:34:13,560
Speaker 2: more detail in a little bit, But the length of

650
00:34:13,560 --> 00:34:15,480
Speaker 2: the day changes by quite a bit through the year

651
00:34:15,600 --> 00:34:17,919
Speaker 2: and over the years, and these short term effects really

652
00:34:17,920 --> 00:34:21,400
Speaker 2: are dominated by what's going on in the atmosphere. So

653
00:34:21,440 --> 00:34:24,160
Speaker 2: the weather changes the length of a day. Isn't that

654
00:34:24,200 --> 00:34:24,920
Speaker 2: kind of crazy?

655
00:34:25,120 --> 00:34:28,520
Speaker 1: That is crazy. I've always suspected it though, because sometimes

656
00:34:28,560 --> 00:34:31,040
Speaker 1: when the weather's really bad, the day just goes on

657
00:34:31,200 --> 00:34:34,080
Speaker 1: and on and on. I'm sure that's what you mean. Well,

658
00:34:34,160 --> 00:34:37,359
Speaker 1: let's take a quick break and when we get back,

659
00:34:37,360 --> 00:34:40,840
Speaker 1: we're going to talk about more ways that the Earth's

660
00:34:40,960 --> 00:34:56,640
Speaker 1: own issues is messing with It's been all right. So

661
00:34:56,920 --> 00:35:01,560
Speaker 1: the Earth is a complicated sphere. Not not exactly a sphere,

662
00:35:01,640 --> 00:35:03,960
Speaker 1: you know, more of an what is it, It's more

663
00:35:03,960 --> 00:35:05,120
Speaker 1: of an oblong right, a.

664
00:35:05,120 --> 00:35:06,719
Speaker 2: Little bit of a squashed basketball.

665
00:35:06,760 --> 00:35:09,239
Speaker 1: Actually, oh, there we go. That's what it was said

666
00:35:09,320 --> 00:35:11,440
Speaker 1: right by the first astronauts, is like, look at that

667
00:35:11,520 --> 00:35:16,080
Speaker 1: squash basketball, the little blue squashed basketball. So we've talked

668
00:35:16,080 --> 00:35:18,680
Speaker 1: about the effect that the moon has. We've talked about

669
00:35:18,719 --> 00:35:23,120
Speaker 1: the melting of the glaciers, and also the atmosphere and weather.

670
00:35:23,400 --> 00:35:23,920
Speaker 2: M hmmm.

671
00:35:24,239 --> 00:35:28,200
Speaker 1: Are there other factors internal to Earth that effects spin?

672
00:35:28,880 --> 00:35:31,080
Speaker 2: Yeah, we talked about what's out beyond the Earth. We

673
00:35:31,160 --> 00:35:33,560
Speaker 2: talked about what's above the surface, but what's going on

674
00:35:33,640 --> 00:35:36,879
Speaker 2: below the surface also has a big impact on how

675
00:35:36,960 --> 00:35:39,880
Speaker 2: fast the surface is spinning. The basic idea there is

676
00:35:39,960 --> 00:35:43,560
Speaker 2: the same that if the core spins at different speeds,

677
00:35:43,600 --> 00:35:46,279
Speaker 2: then the surface will spin at different speeds. Like if

678
00:35:46,320 --> 00:35:49,520
Speaker 2: something happened to speed up the core, then the surface

679
00:35:49,560 --> 00:35:52,400
Speaker 2: would slow down, or if the core went slower, the

680
00:35:52,480 --> 00:35:55,960
Speaker 2: surface would go faster, for the same gyroscopic reasons, right

681
00:35:56,000 --> 00:36:00,160
Speaker 2: conservation of angular momentum. And we have a big, big,

682
00:36:00,400 --> 00:36:03,480
Speaker 2: heavy core at the center of the Earth that spins

683
00:36:03,560 --> 00:36:06,360
Speaker 2: in weird ways, and how it spins and how that

684
00:36:06,440 --> 00:36:09,560
Speaker 2: spin changes definitely affects the length of the day.

685
00:36:09,960 --> 00:36:14,320
Speaker 1: When I visualize the Earth's core, I do see a

686
00:36:14,400 --> 00:36:18,480
Speaker 1: lava lamp, And I know that's probably not exactly accurate,

687
00:36:18,520 --> 00:36:21,560
Speaker 1: but that's how I imagine it, Like a bunch of hot,

688
00:36:21,920 --> 00:36:26,200
Speaker 1: gloopy substances kind of wiggling around each other inside there.

689
00:36:26,640 --> 00:36:29,399
Speaker 2: Yeah, that's not a bad mental model of.

690
00:36:31,320 --> 00:36:33,800
Speaker 1: I knew I could learn something from my bad taste

691
00:36:33,840 --> 00:36:34,640
Speaker 1: and home to core.

692
00:36:35,080 --> 00:36:37,560
Speaker 2: We have a few layers inside the Earth, but the

693
00:36:37,600 --> 00:36:41,040
Speaker 2: core is a big blob of iron and nickel. It's

694
00:36:41,080 --> 00:36:44,600
Speaker 2: about the size of Pluto. And because it's a massive

695
00:36:44,840 --> 00:36:47,880
Speaker 2: small changes in its spin will affect the spin of

696
00:36:47,920 --> 00:36:50,600
Speaker 2: the rest of the planet. And you might wonder, like, well,

697
00:36:50,600 --> 00:36:52,759
Speaker 2: how do we even know what's inside the planet and

698
00:36:52,760 --> 00:36:56,040
Speaker 2: how fast it's spinning. Well, nobody's been able to drill

699
00:36:56,120 --> 00:36:58,640
Speaker 2: down there and see it directly because.

700
00:36:58,360 --> 00:37:00,839
Speaker 1: Willis didnt hang on.

701
00:37:01,400 --> 00:37:04,399
Speaker 2: We can kind of ultrasound the earth, right, How does

702
00:37:04,400 --> 00:37:07,040
Speaker 2: an ultrasound work? How do you see a baby in

703
00:37:07,080 --> 00:37:10,040
Speaker 2: a pregnant woman's belly without opening her up? Of course,

704
00:37:10,280 --> 00:37:13,239
Speaker 2: as you send little sound waves down in there, ultrasound

705
00:37:13,320 --> 00:37:16,600
Speaker 2: emids high frequency sound waves higher than you can hear

706
00:37:17,000 --> 00:37:21,160
Speaker 2: infrasound would be very low frequency ultrasound amidst those sound waves.

707
00:37:21,320 --> 00:37:23,239
Speaker 2: And then based on how those soundwaves move to the

708
00:37:23,239 --> 00:37:27,120
Speaker 2: body and reflect and bounce back and interfere, we get

709
00:37:27,160 --> 00:37:29,960
Speaker 2: a picture of what's going on, sort of like knocking

710
00:37:30,040 --> 00:37:31,960
Speaker 2: on a wall to see whether it's tallow or not.

711
00:37:32,080 --> 00:37:34,960
Speaker 2: And as you move around you get different sounds. You

712
00:37:35,000 --> 00:37:37,600
Speaker 2: can sort of like make a mental image for what's

713
00:37:37,640 --> 00:37:41,040
Speaker 2: going on out there based on those sounds. And we

714
00:37:41,080 --> 00:37:43,000
Speaker 2: can do the same thing with the Earth.

715
00:37:43,239 --> 00:37:46,879
Speaker 1: So we take the Earth to the universe's largest obgy

716
00:37:47,040 --> 00:37:50,760
Speaker 1: in do an ultrasound on it. What are we seeing

717
00:37:51,120 --> 00:37:51,600
Speaker 1: in there?

718
00:37:51,920 --> 00:37:53,880
Speaker 2: So imagine we have like an earthquake, which is a

719
00:37:53,920 --> 00:37:57,840
Speaker 2: big sonic event. It creates pressure waves inside the Earth.

720
00:37:58,160 --> 00:38:00,840
Speaker 2: Those waves propagate through the earth. Earth. It is basically

721
00:38:00,880 --> 00:38:04,040
Speaker 2: like a fluid. Those pressure waves pass through the same way,

722
00:38:04,080 --> 00:38:06,399
Speaker 2: like if you slap the surface of the water, you're

723
00:38:06,400 --> 00:38:09,120
Speaker 2: gonna get waves moving through the water. So you have

724
00:38:09,160 --> 00:38:11,920
Speaker 2: a big earthquake and you get waves moving through the Earth.

725
00:38:12,239 --> 00:38:14,800
Speaker 2: Now if they meet a layer where like the density

726
00:38:14,800 --> 00:38:17,480
Speaker 2: of the earth is changing a lot, then those waves

727
00:38:17,520 --> 00:38:20,440
Speaker 2: are going to reflect and refract the same way like

728
00:38:20,840 --> 00:38:23,600
Speaker 2: light moving through glass or light moving through water will

729
00:38:23,680 --> 00:38:26,719
Speaker 2: change direction and some of it will bounce back. Density

730
00:38:26,760 --> 00:38:29,080
Speaker 2: waves moving through the earth will do the same thing.

731
00:38:29,560 --> 00:38:32,400
Speaker 2: So that's how we know that there are different layers

732
00:38:32,760 --> 00:38:36,560
Speaker 2: inside the Earth because we see these reflections. Earthquakes send

733
00:38:36,560 --> 00:38:39,200
Speaker 2: these waves down and we see how they bounce back

734
00:38:39,360 --> 00:38:42,120
Speaker 2: and bounce all around. We actually have to build complicated

735
00:38:42,200 --> 00:38:45,160
Speaker 2: models for how we expect these things to bounce around

736
00:38:45,160 --> 00:38:48,200
Speaker 2: and then compare them to the measurements we make around

737
00:38:48,200 --> 00:38:52,200
Speaker 2: the globe with seismometers of how things are wiggling. So yeah,

738
00:38:52,239 --> 00:38:54,759
Speaker 2: it's basically like a big obgy in for the.

739
00:38:54,719 --> 00:38:59,920
Speaker 1: Earth, right, So earthquakes is the obgy in for Earth,

740
00:39:00,280 --> 00:39:03,080
Speaker 1: got it? And then we measure those and then we

741
00:39:03,120 --> 00:39:06,440
Speaker 1: can figure out what is that feedback the pattern of

742
00:39:06,480 --> 00:39:09,359
Speaker 1: sort of interference and what that is saying about what's

743
00:39:09,400 --> 00:39:13,399
Speaker 1: going on. How do we know what it is made

744
00:39:13,440 --> 00:39:16,520
Speaker 1: out of? Right? Like, do we just expect different sort

745
00:39:16,560 --> 00:39:22,160
Speaker 1: of feedback patterns from different substances or are we getting

746
00:39:22,280 --> 00:39:26,800
Speaker 1: direct samples of the stuff that isn't the guy center

747
00:39:26,840 --> 00:39:27,360
Speaker 1: of the earth.

748
00:39:28,600 --> 00:39:32,040
Speaker 2: We're effectively measuring the density because the density controls the

749
00:39:32,080 --> 00:39:35,759
Speaker 2: speed of sound. As things are denser, sound travels more

750
00:39:35,840 --> 00:39:38,600
Speaker 2: quickly through them. That's why sound moves more rapidly through

751
00:39:38,600 --> 00:39:41,840
Speaker 2: water or steel than it does through the air. Because

752
00:39:41,880 --> 00:39:44,600
Speaker 2: sound are pressure waves, and if those atoms are more

753
00:39:44,640 --> 00:39:47,839
Speaker 2: tightly packed, then they have stronger bonds between them. Then

754
00:39:47,960 --> 00:39:50,239
Speaker 2: rippling one is going to ripple the other one more

755
00:39:50,320 --> 00:39:54,000
Speaker 2: quickly than if they're like farther apart or more loosely bound.

756
00:39:54,480 --> 00:39:58,360
Speaker 2: So the speed at which sound travels indicates the density

757
00:39:58,360 --> 00:40:01,280
Speaker 2: of the material. So by seeing how long it takes

758
00:40:01,600 --> 00:40:04,560
Speaker 2: those waves to propagate through the earth and when they return,

759
00:40:04,960 --> 00:40:07,040
Speaker 2: we can get an idea for the density of each

760
00:40:07,080 --> 00:40:09,960
Speaker 2: of the layers. And not just the density, we can

761
00:40:10,040 --> 00:40:14,239
Speaker 2: also measure the speed of their rotation because how fast

762
00:40:14,280 --> 00:40:17,440
Speaker 2: that inner layer is moving changes what the wave looks like.

763
00:40:17,520 --> 00:40:20,120
Speaker 2: When it bounces back. We all know about the Doppler

764
00:40:20,160 --> 00:40:23,080
Speaker 2: effect that, like a police siren going by you will

765
00:40:23,120 --> 00:40:29,720
Speaker 2: sound different as it's approaching you and as it's Yeah, exactly,

766
00:40:29,760 --> 00:40:32,560
Speaker 2: the same thing is true for waves that bounce off

767
00:40:32,600 --> 00:40:35,360
Speaker 2: of an object. If you use the radar to measure

768
00:40:35,440 --> 00:40:38,680
Speaker 2: that police cars velocity as it was going by, the

769
00:40:38,719 --> 00:40:41,160
Speaker 2: waves that come back to you tell you something about

770
00:40:41,160 --> 00:40:44,520
Speaker 2: the velocity of the police car. And in the same way,

771
00:40:44,600 --> 00:40:47,080
Speaker 2: waves that bounce off inner layers of the earth tell

772
00:40:47,160 --> 00:40:50,319
Speaker 2: us about the velocity of those layers. So we can

773
00:40:50,400 --> 00:40:52,440
Speaker 2: use these waves not just to image the earth and

774
00:40:52,480 --> 00:40:56,200
Speaker 2: tell where stuff is, but also how fast it's going,

775
00:40:56,520 --> 00:40:59,600
Speaker 2: though that takes more precise and crisper measurements.

776
00:41:00,120 --> 00:41:02,160
Speaker 1: I mean, it seems kind of hard to do that though,

777
00:41:02,200 --> 00:41:05,640
Speaker 1: For we always have to wait for an earthquake to happen,

778
00:41:06,760 --> 00:41:08,920
Speaker 1: and we can't really predict where the earthquake is going

779
00:41:09,000 --> 00:41:10,759
Speaker 1: to be. How do we do that?

780
00:41:11,080 --> 00:41:13,160
Speaker 2: So the best way to do that actually is to

781
00:41:13,320 --> 00:41:17,200
Speaker 2: create our own sonic waves rather than just wait for earthquakes.

782
00:41:17,640 --> 00:41:20,759
Speaker 1: And hey, big hammer, then big hammer.

783
00:41:20,680 --> 00:41:24,000
Speaker 2: Basically big physics hammer. Because there was a period after

784
00:41:24,080 --> 00:41:26,960
Speaker 2: the development of nuclear weapons and before we stopped testing

785
00:41:27,000 --> 00:41:30,440
Speaker 2: them that we did tests underground. So first we had

786
00:41:30,520 --> 00:41:33,080
Speaker 2: nuclear weapons and we tested them above ground, which was

787
00:41:33,200 --> 00:41:37,080
Speaker 2: exceptionally stupid because of the atmospheric radiation. Then we realized

788
00:41:37,239 --> 00:41:39,360
Speaker 2: that's not such a good idea, so then we started

789
00:41:39,400 --> 00:41:40,880
Speaker 2: testing them underground.

790
00:41:41,360 --> 00:41:43,120
Speaker 1: My dad some.

791
00:41:43,000 --> 00:41:46,000
Speaker 2: Of these test sites. You would explode a nuclear bomb

792
00:41:46,120 --> 00:41:49,040
Speaker 2: underground and then you would measure the impact and that

793
00:41:49,080 --> 00:41:51,880
Speaker 2: would create huge sonic oscillations in the crust of the

794
00:41:51,920 --> 00:41:56,080
Speaker 2: earth and very crisp, very clean because it was high intensity,

795
00:41:56,320 --> 00:41:59,319
Speaker 2: and also very brief, so it wrung the earth like

796
00:41:59,360 --> 00:42:00,320
Speaker 2: a perfect.

797
00:42:00,680 --> 00:42:04,520
Speaker 1: Whoa, Okay, so I've got it. Like several questions. One

798
00:42:04,640 --> 00:42:09,040
Speaker 1: is when you explode a nuke underground, where does all

799
00:42:09,080 --> 00:42:11,640
Speaker 1: that radiation go? Does it just sort of sink into

800
00:42:11,680 --> 00:42:14,680
Speaker 1: the earth somewhere, So that's question number one.

801
00:42:15,400 --> 00:42:18,880
Speaker 2: It's absorbed by the material immediately surrounding the explosion, so

802
00:42:18,880 --> 00:42:22,280
Speaker 2: it doesn't sink. It just gets deposited in the surrounding

803
00:42:22,320 --> 00:42:23,120
Speaker 2: dirt and rock.

804
00:42:23,480 --> 00:42:26,760
Speaker 1: So are there like pockets of radiation in these areas

805
00:42:26,800 --> 00:42:31,000
Speaker 1: where we tested these nukes, Yes, there are, gross it's

806
00:42:31,120 --> 00:42:35,480
Speaker 1: like a zip on the earth. Question number two is

807
00:42:35,560 --> 00:42:38,719
Speaker 1: how big I've seen a basement that doesn't seem big

808
00:42:38,800 --> 00:42:41,879
Speaker 1: enough to do a nuke inside of. So, like, how

809
00:42:41,880 --> 00:42:44,080
Speaker 1: big were these areas where they tested.

810
00:42:43,760 --> 00:42:46,160
Speaker 2: These Yeah, well the holes themselves are not that large

811
00:42:46,200 --> 00:42:48,319
Speaker 2: because you want them surrounded by the rock.

812
00:42:48,600 --> 00:42:52,360
Speaker 1: Yeah, okay, so then you put it down into the

813
00:42:52,400 --> 00:42:56,400
Speaker 1: hole and then it explodes into the rock, leaving what

814
00:42:57,480 --> 00:43:00,000
Speaker 1: kind of like how big is that exploded?

815
00:43:00,760 --> 00:43:04,319
Speaker 2: These nuclear explosions have significant impact on the rock for

816
00:43:04,440 --> 00:43:07,480
Speaker 2: you know, meters and meters and tens of meters, and

817
00:43:07,480 --> 00:43:09,880
Speaker 2: then you surrounded by various sensors so you can measure

818
00:43:09,920 --> 00:43:12,560
Speaker 2: the energy and the length of the shockwave and all

819
00:43:12,600 --> 00:43:15,600
Speaker 2: sorts of stuff. And not only do you create sensors

820
00:43:15,600 --> 00:43:18,719
Speaker 2: for your own explosions, because of the Cold War, the

821
00:43:18,840 --> 00:43:22,919
Speaker 2: US government invested deeply in seismic sensors so we could

822
00:43:23,000 --> 00:43:26,480
Speaker 2: study the Soviet explosions because we wanted to see when

823
00:43:26,560 --> 00:43:29,799
Speaker 2: they were testing nuclear weapons. And if you tapped one underground,

824
00:43:29,880 --> 00:43:32,640
Speaker 2: everybody across the Earth can figure it out. So it

825
00:43:32,719 --> 00:43:35,800
Speaker 2: was sort of like a golden age for seismology because

826
00:43:35,840 --> 00:43:38,520
Speaker 2: not only were there these crisp events that created these

827
00:43:38,600 --> 00:43:42,080
Speaker 2: ripples around the Earth, but also the US government invested

828
00:43:42,120 --> 00:43:45,680
Speaker 2: in the best possible set of seismographs, so we could

829
00:43:45,680 --> 00:43:49,200
Speaker 2: get data about Soviet tests. So there's this window of

830
00:43:49,239 --> 00:43:52,280
Speaker 2: like fifteen years in the end of the last century

831
00:43:52,719 --> 00:43:56,480
Speaker 2: when there's this excellent seismographic data about what's going on

832
00:43:56,600 --> 00:43:57,520
Speaker 2: inside the earth.

833
00:43:58,320 --> 00:44:02,200
Speaker 1: We were staring down nuclear annihilation, but at least we

834
00:44:02,320 --> 00:44:04,000
Speaker 1: got some good data from it.

835
00:44:04,800 --> 00:44:07,680
Speaker 2: You know, there's so many times when important science is

836
00:44:07,719 --> 00:44:12,239
Speaker 2: writing on the back of like either whimsical consumer electronics

837
00:44:12,239 --> 00:44:15,680
Speaker 2: where people spending like billions of dollars on their gadgets,

838
00:44:16,239 --> 00:44:19,080
Speaker 2: or the military industrial complex where you know, they spend

839
00:44:19,080 --> 00:44:22,560
Speaker 2: billions of dollars on satellites or something else, and we

840
00:44:22,600 --> 00:44:25,040
Speaker 2: can gather science data from it. And because science funding

841
00:44:25,120 --> 00:44:28,680
Speaker 2: is a tiny fraction of consumer spending or military spending,

842
00:44:28,880 --> 00:44:32,200
Speaker 2: we always got to take advantage of that whenever we can. Yeah,

843
00:44:32,360 --> 00:44:34,839
Speaker 2: and so there were some folks who pretty recently dug

844
00:44:34,920 --> 00:44:38,240
Speaker 2: up these old tapes and this is like science heroism

845
00:44:38,280 --> 00:44:40,600
Speaker 2: because they had to find these data and pull them

846
00:44:40,640 --> 00:44:43,520
Speaker 2: off of magnetic tapes, and remember how it was stored,

847
00:44:43,600 --> 00:44:46,160
Speaker 2: and sometimes you have to like bake these tapes to

848
00:44:46,200 --> 00:44:49,280
Speaker 2: the magnetic particles adhere better to the actual tape.

849
00:44:49,360 --> 00:44:52,959
Speaker 1: What you bacon, Oh, you know, tapes on nuclear explosions

850
00:44:53,040 --> 00:44:55,600
Speaker 1: done in the sixties and seventies.

851
00:44:55,440 --> 00:44:58,319
Speaker 2: And so pretty recently they found this data, they pulled

852
00:44:58,320 --> 00:45:01,480
Speaker 2: it off, they analyzed it, and they discovered something fascinating

853
00:45:01,560 --> 00:45:04,360
Speaker 2: about the core of the Earth. We always expected that

854
00:45:04,400 --> 00:45:07,440
Speaker 2: the core is rotating slightly faster than the surface of

855
00:45:07,480 --> 00:45:09,360
Speaker 2: the Earth, but what they found is that it was

856
00:45:09,440 --> 00:45:12,600
Speaker 2: much more variable than they expected. There's sometimes when the

857
00:45:12,600 --> 00:45:15,080
Speaker 2: core is rotating faster, and sometimes when the core is

858
00:45:15,160 --> 00:45:18,720
Speaker 2: rotating slower than the surface of the Earth. The surface

859
00:45:18,760 --> 00:45:20,920
Speaker 2: like catches up to it and passes it, and then

860
00:45:20,920 --> 00:45:22,160
Speaker 2: the core rotates faster.

861
00:45:22,440 --> 00:45:24,520
Speaker 1: Do you think that this is random or do you

862
00:45:24,520 --> 00:45:27,360
Speaker 1: think there's some kind of cyclical nature to the core.

863
00:45:27,520 --> 00:45:29,919
Speaker 2: What they discovered is that the oscillates in like six

864
00:45:30,040 --> 00:45:32,759
Speaker 2: year periods, where like one is going faster and the

865
00:45:32,800 --> 00:45:35,440
Speaker 2: other is going faster. And this is not something we

866
00:45:35,640 --> 00:45:38,160
Speaker 2: understand very well. You know, the inner parts of the

867
00:45:38,200 --> 00:45:40,440
Speaker 2: Earth are sort of a mystery, and you know, the

868
00:45:40,480 --> 00:45:42,960
Speaker 2: flow of energy there and the convection cells as things

869
00:45:43,000 --> 00:45:45,920
Speaker 2: are moving up and bubbling and frothing inside the earth

870
00:45:46,160 --> 00:45:48,200
Speaker 2: are something we're still trying to understand. So this is

871
00:45:48,200 --> 00:45:52,120
Speaker 2: a really interesting and fascinating clue for geologists. For those

872
00:45:52,160 --> 00:45:54,319
Speaker 2: people who saw news coverage about it, it was a little

873
00:45:54,360 --> 00:45:58,440
Speaker 2: bit misleading. It suggested that the Earth's core is changing direction,

874
00:45:58,920 --> 00:46:01,040
Speaker 2: that it's like rotating one way and then stops and

875
00:46:01,120 --> 00:46:04,480
Speaker 2: rotates the other way. That's not exactly what's happening. What's

876
00:46:04,480 --> 00:46:06,960
Speaker 2: happening is that's going faster than the surface and then

877
00:46:06,960 --> 00:46:10,880
Speaker 2: sometimes slower than the surface. So it's changing direction relative

878
00:46:10,920 --> 00:46:13,680
Speaker 2: to the surface, but not like relative to the Sun

879
00:46:13,840 --> 00:46:16,520
Speaker 2: or something like that. It's not like it's actually changing direction.

880
00:46:17,040 --> 00:46:19,319
Speaker 2: That would be much more dramatic and more awesome, but

881
00:46:19,360 --> 00:46:22,040
Speaker 2: that's not the scenario. But what it does mean is

882
00:46:22,080 --> 00:46:24,560
Speaker 2: that it's affecting the length of the day because it

883
00:46:24,600 --> 00:46:26,640
Speaker 2: affects how quickly the surface is rotating.

884
00:46:26,800 --> 00:46:28,839
Speaker 1: Okay, so this is a call out, so I'll keep

885
00:46:28,840 --> 00:46:32,880
Speaker 1: it anonymous. But I did have a strange science teacher

886
00:46:33,320 --> 00:46:37,240
Speaker 1: in elementary school who told us that the Earth's core

887
00:46:37,560 --> 00:46:42,080
Speaker 1: would change directions sometime in our lifetimes and that the

888
00:46:42,680 --> 00:46:47,760
Speaker 1: poles would switch and we would all get deadly skin cancer.

889
00:46:48,040 --> 00:46:50,120
Speaker 1: Is that true?

890
00:46:50,560 --> 00:46:52,800
Speaker 2: The Earth's core is not going to change direction except

891
00:46:52,800 --> 00:46:56,239
Speaker 2: for relative to the surface of the Earth. So in

892
00:46:56,280 --> 00:46:58,960
Speaker 2: that sense, yes, the magnetic north and south pole is

893
00:46:59,000 --> 00:47:01,480
Speaker 2: something of a fun miss and it does flip every

894
00:47:01,520 --> 00:47:03,640
Speaker 2: once in a while, but these flips tend to be

895
00:47:03,719 --> 00:47:06,880
Speaker 2: like tens of thousands of years, so probably not within

896
00:47:06,960 --> 00:47:09,799
Speaker 2: our lifetime. Although it's a little bit chaotic. It's much

897
00:47:09,840 --> 00:47:12,360
Speaker 2: more chaotic than the flip in the sun, which is

898
00:47:12,520 --> 00:47:15,799
Speaker 2: very regular, but again not something that we understand.

899
00:47:16,040 --> 00:47:19,719
Speaker 1: Okay, well, you know who you are, science teacher that

900
00:47:19,760 --> 00:47:20,720
Speaker 1: I had, You're wrong.

901
00:47:23,400 --> 00:47:25,759
Speaker 2: We're all just learning about the nature of the labors, right,

902
00:47:25,760 --> 00:47:27,600
Speaker 2: everybody's just updating their information.

903
00:47:28,800 --> 00:47:31,080
Speaker 1: That's a much kinder way to put it all. Right,

904
00:47:31,160 --> 00:47:34,919
Speaker 1: So we are having this oscillation of the Earth's core.

905
00:47:35,040 --> 00:47:38,399
Speaker 1: It is sometimes slower and sometimes faster than how the

906
00:47:38,520 --> 00:47:41,600
Speaker 1: crust is moving, and so that is having an impact

907
00:47:41,640 --> 00:47:43,120
Speaker 1: on the spin of the Earth.

908
00:47:43,600 --> 00:47:45,879
Speaker 2: Yeah, and so there are these long term effects, right.

909
00:47:45,920 --> 00:47:48,399
Speaker 2: The moon is the most dominant long term effect that's

910
00:47:48,400 --> 00:47:52,680
Speaker 2: slowing down the rotation of the Earth and making days longer.

911
00:47:53,320 --> 00:47:57,160
Speaker 2: The melting of glaciers is the most important effect long

912
00:47:57,239 --> 00:48:00,359
Speaker 2: term that's speeding up the rotation of the Earth, though

913
00:48:00,360 --> 00:48:02,680
Speaker 2: it's not as dramatic as the effect of the moon.

914
00:48:03,080 --> 00:48:06,919
Speaker 2: On shorter timescales, we have like the rotation of the core,

915
00:48:07,000 --> 00:48:10,120
Speaker 2: which affects things on a few year timescales, like six

916
00:48:10,239 --> 00:48:13,440
Speaker 2: year cycles. Then there's the atmosphere that changes things on

917
00:48:13,480 --> 00:48:16,960
Speaker 2: a much shorter timescale, and so for example, there's like

918
00:48:17,000 --> 00:48:20,240
Speaker 2: an annual period of the length of the day changing

919
00:48:20,280 --> 00:48:23,960
Speaker 2: of like a third of a millisecond per day, maximizing

920
00:48:24,040 --> 00:48:28,080
Speaker 2: like in February, and then again like in May. And

921
00:48:28,120 --> 00:48:30,600
Speaker 2: so there's these funny wiggles in the length of a day.

922
00:48:30,600 --> 00:48:32,400
Speaker 2: If you look at the data, it goes up and

923
00:48:32,440 --> 00:48:35,040
Speaker 2: down through the years on these longer cycles, and then

924
00:48:35,040 --> 00:48:38,600
Speaker 2: there's these really fast variations throughout the year. So like

925
00:48:38,800 --> 00:48:42,400
Speaker 2: even during a year, not every day is the same length.

926
00:48:43,000 --> 00:48:45,680
Speaker 2: In fact, recently we had a day June twenty ninth,

927
00:48:45,960 --> 00:48:49,120
Speaker 2: my mom's birthday, I think got a coincidence two thousand

928
00:48:49,120 --> 00:48:52,080
Speaker 2: and two, which was the shortest day ever on record.

929
00:48:52,600 --> 00:48:55,280
Speaker 1: Oh my gosh, that is so unfair to your mom.

930
00:48:55,560 --> 00:48:56,880
Speaker 1: That's so unfair.

931
00:48:57,400 --> 00:49:00,160
Speaker 2: Her birthday was like a millisecond and a half more

932
00:49:00,200 --> 00:49:01,240
Speaker 2: than twenty four hours.

933
00:49:01,280 --> 00:49:06,719
Speaker 1: She was taking injustice. Injustice, Just make it up to

934
00:49:06,760 --> 00:49:10,640
Speaker 1: her for next birthday, give her like one point six

935
00:49:11,040 --> 00:49:13,160
Speaker 1: extra milliseconds of birthday time.

936
00:49:15,000 --> 00:49:16,960
Speaker 2: And so overall, the length of a day is not

937
00:49:17,239 --> 00:49:20,600
Speaker 2: changing on timescales, so we can really measure, as much

938
00:49:20,600 --> 00:49:22,360
Speaker 2: as we joke about it, a mill a second and

939
00:49:22,400 --> 00:49:24,359
Speaker 2: a half of your birthday is not something you're going

940
00:49:24,400 --> 00:49:27,799
Speaker 2: to notice is at length of an eye, but it

941
00:49:27,840 --> 00:49:30,440
Speaker 2: is something that's changing. You know. These things that we

942
00:49:30,520 --> 00:49:33,360
Speaker 2: think are constant, like the moon and the sun and

943
00:49:33,400 --> 00:49:37,200
Speaker 2: the rotation of the Earth, these things are functions of time.

944
00:49:37,680 --> 00:49:40,360
Speaker 2: They are descriptions of where we are in the moment,

945
00:49:40,680 --> 00:49:44,600
Speaker 2: and on much longer cosmological time scales, these things are

946
00:49:44,680 --> 00:49:47,439
Speaker 2: changing dramatically. The rotation of the Earth was a sixth

947
00:49:47,440 --> 00:49:49,440
Speaker 2: hour day and it's on its way to becoming a

948
00:49:49,480 --> 00:49:53,080
Speaker 2: twenty eight day long day, and so here we are

949
00:49:53,160 --> 00:49:55,720
Speaker 2: sort of in the middle of that vast cosmic journey.

950
00:49:55,719 --> 00:49:59,040
Speaker 2: At one particular moment, we think it's the moment that

951
00:49:59,080 --> 00:50:01,239
Speaker 2: defines what it's like to be on Earth, but it's

952
00:50:01,239 --> 00:50:05,120
Speaker 2: not really. It's just one slice of an incredibly deep history.

953
00:50:05,360 --> 00:50:10,719
Speaker 1: So if I sleep for like ten hours, right, I

954
00:50:10,760 --> 00:50:14,360
Speaker 1: could say, hey, I'm not oversleeping, I'm just planning for

955
00:50:14,400 --> 00:50:14,960
Speaker 1: the future.

956
00:50:16,520 --> 00:50:19,240
Speaker 2: You're just incredibly far sighted, that's right.

957
00:50:19,400 --> 00:50:23,600
Speaker 1: This is actually not laziness. This is I'm trying to

958
00:50:23,719 --> 00:50:27,960
Speaker 1: evolve for our eventual lengthened day night cycles.

959
00:50:28,440 --> 00:50:31,080
Speaker 2: Well, to me, it's fascinating that if these things change,

960
00:50:31,080 --> 00:50:33,960
Speaker 2: but change very slowly, life on Earth has a chance

961
00:50:34,000 --> 00:50:37,319
Speaker 2: to adapt. Right, It's curious to me, like, what will

962
00:50:37,360 --> 00:50:39,840
Speaker 2: life be like on Earth when the day night cycle

963
00:50:40,120 --> 00:50:43,200
Speaker 2: is twenty eight of our current days, or even a

964
00:50:43,200 --> 00:50:46,120
Speaker 2: week of our current days. I feel like everything on

965
00:50:46,200 --> 00:50:48,480
Speaker 2: Earth must be different. I mean, the weather patterns are

966
00:50:48,480 --> 00:50:51,280
Speaker 2: going to be very different. The entire experience of life

967
00:50:51,280 --> 00:50:54,040
Speaker 2: on Earth and what it takes to survive will be

968
00:50:54,160 --> 00:50:54,880
Speaker 2: vastly different.

969
00:50:55,200 --> 00:50:57,719
Speaker 1: It is so hard to imagine because it really that

970
00:50:57,840 --> 00:51:01,480
Speaker 1: day night cycle does determine the behavior of every creature

971
00:51:02,120 --> 00:51:07,080
Speaker 1: on Earth and how massively you would have to adapt

972
00:51:07,120 --> 00:51:10,840
Speaker 1: and change to you know, you may have just entire

973
00:51:11,560 --> 00:51:14,240
Speaker 1: you know, nocturnal species, and you'd have to also adapt

974
00:51:14,320 --> 00:51:16,759
Speaker 1: to the how cold it would get. Right, if you

975
00:51:16,800 --> 00:51:19,680
Speaker 1: have one side of the planet that's not facing the sun,

976
00:51:19,760 --> 00:51:22,439
Speaker 1: it's going to be a lot colder than the other side,

977
00:51:22,440 --> 00:51:23,880
Speaker 1: and the other side it's gonna be a lot hotter.

978
00:51:24,239 --> 00:51:26,960
Speaker 1: It is unfathomable the amount of change if there is

979
00:51:27,000 --> 00:51:29,920
Speaker 1: still life on Earth, Like what the adaptations would have

980
00:51:29,960 --> 00:51:32,040
Speaker 1: to be in that situation.

981
00:51:32,080 --> 00:51:35,279
Speaker 2: And what would our podcast releasing schedule be in that

982
00:51:35,360 --> 00:51:38,040
Speaker 2: kind of scenario? Are we releasing more often less often?

983
00:51:38,080 --> 00:51:38,840
Speaker 2: I'm losing track?

984
00:51:39,600 --> 00:51:42,440
Speaker 1: Yeah, it'll have to be based on the commute, the

985
00:51:42,880 --> 00:51:44,279
Speaker 1: once a month commute.

986
00:51:45,520 --> 00:51:47,960
Speaker 2: All right, Well, thanks Katie for joining us and spinning

987
00:51:47,960 --> 00:51:51,080
Speaker 2: your mind around this topic, and thanks everybody for joining

988
00:51:51,160 --> 00:51:53,640
Speaker 2: us on this trip around the surface of the Earth

989
00:51:53,880 --> 00:51:56,720
Speaker 2: and understanding the fundamentals of its rotation.

990
00:51:57,200 --> 00:52:02,000
Speaker 1: Yeah, I have a stellar day everyone.

991
00:52:00,920 --> 00:52:03,960
Speaker 2: A little bit shorter than your solar day. All right everyone,

992
00:52:04,080 --> 00:52:12,279
Speaker 2: Thanks again. Tune in next time for more science and curiosity.

993
00:52:12,320 --> 00:52:15,200
Speaker 2: Come find us on social media, where we answer questions

994
00:52:15,200 --> 00:52:19,640
Speaker 2: and post videos. We're on Twitter, Discorg, Instant and now TikTok.

995
00:52:20,360 --> 00:52:23,160
Speaker 2: Thanks for listening, and remember that Daniel and Jorge Explain

996
00:52:23,200 --> 00:52:27,200
Speaker 2: the Universe is a production of iHeartRadio. For more podcasts

997
00:52:27,239 --> 00:52:31,880
Speaker 2: from iHeartRadio, visit the iHeartRadio app, Apple Podcasts, or wherever

998
00:52:31,920 --> 00:52:33,640
Speaker 2: you listen to your favorite shows.