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Speaker 1: If the Earth and Jupiter were to collide, what would happen?

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Speaker 1: How would we die?

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Speaker 2: Circadian rhythms are corrected using the Sun's light. If you

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Speaker 2: live at the bottom of the sea, how do you

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Speaker 2: get that right?

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Speaker 1: How big a planet could we use rockets to escape?

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Speaker 1: If we'd evolved on Jupiter, would we be planet down apes?

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Speaker 2: Whatever questions keep you up at night, Daniel and Kelly's

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Speaker 2: answers will make it right.

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Speaker 1: Welcome to Daniel and Kelly's Extraordinary Universe.

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Speaker 2: With an emphasis on Jupiter, it seems. Hello, I'm Kelly Wiersmith,

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Speaker 2: and I study parasites and space, and clearly Jupiter is

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Speaker 2: the best planet.

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Speaker 1: Hi, I'm Daniel. I'm a particle physicist, and yes, Jupiter

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Speaker 1: has the most particles of any planet.

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Speaker 2: And does that make it the best As a particle physicist.

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Speaker 1: It makes it the mostiest? I guess you know. I

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Speaker 1: think people underestimate, like how much of the Solar System

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Speaker 1: is just the Sun in Jupiter? Like mostly it's just

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Speaker 1: the Sun, and then you want to add Jupiter, all right,

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Speaker 1: to round it up to nine to nine point nine,

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Speaker 1: and everything else is just details. We're really just here

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Speaker 1: in somebody else's party.

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Speaker 2: Oh, man, that's a little it's a kind of a

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Speaker 2: bummer of a way to start our episode.

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Speaker 1: We are all insignificant, No, I think it tells you

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Speaker 1: something though, when you look at the depiction of the

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Speaker 1: Solar System and all the planets are like big, and

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Speaker 1: obviously it's not the scale, but it tells you something

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Speaker 1: about what we find important. Right, Clearly, we are important

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Speaker 1: in the Solar System. So we zoom up. It's like

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Speaker 1: that cover of the New Yorker where they show like

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Speaker 1: a map of the United States from the New York

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Speaker 1: City perspective, and it's like mostly Manhattan and then like

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Speaker 1: a few details and that's ridiculous and you laugh at it,

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Speaker 1: But that's exactly what we're doing about the planets, right.

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Speaker 3: Well.

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Speaker 2: But you know, on the one hand, we've known about

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Speaker 2: Jupiter for much less long than we've known about Earth,

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Speaker 2: and you know, we're here on Earth, makes it easier

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Speaker 2: to study. I'm going to go ahead and stand down

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Speaker 2: on defensive Earth and the Earth centered view of the world.

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Speaker 1: I'm the saying it's wrong. I'm just saying it reveals

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Speaker 1: something about our biases, right, the things we think should

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Speaker 1: be presented first.

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Speaker 2: I grant you that, but there's probably, you know, solar

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Speaker 2: systems that are bigger than ours, and maybe we shouldn't

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Speaker 2: even be talking about our solar system at all. And

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Speaker 2: where do you stop, Daniel, Where does it end?

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Speaker 1: It never ends, Kelly, There's no bottom to the philosophical

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Speaker 1: rabbit hole.

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Speaker 2: Oh my goodness.

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Speaker 1: But we love going down rabbit holes, especially rabbit holes

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Speaker 1: that you are interested in. So if you have a

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Speaker 1: question about the nature of the universe, or how something works,

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Speaker 1: or how little squishy critters make their lives, please write

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Speaker 1: to us with your question. We would love to answer

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Speaker 1: it here on the pod. And today we're answering three

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Speaker 1: super fun questions from listeners.

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Speaker 2: That's right, so let's start with our first question from.

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Speaker 1: Brad, A great question about Jupiter, of course.

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Speaker 4: Hello, Daniel and Kelly. I have a question about planetary collisions.

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Speaker 4: Jupiter is classified as a gas giant planet and is

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Speaker 4: known to sweep up many stray masses flowing through our

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Speaker 4: Solar system. If something were to happen to cause Earth

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Speaker 4: and Jupiter to collide, what would happen at impact? Is

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Speaker 4: the mass of Jupiter large enough to spaghettify Earth and

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Speaker 4: destroy us like a black hole? Or is the likelihood

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Speaker 4: of a direct collision too small, and Earth would just

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Speaker 4: be ejected from the Solar System if we become too close.

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Speaker 4: Or is the surfaces of Jupiter really a gas and

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Speaker 4: Earth would just pass into the inside of Jupiter and

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Speaker 4: basically be absorbed, and Earth would just coast through a

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Speaker 4: dense atmosphere of gases and would eventually hit a solid core.

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Speaker 4: Thanks Brad from League City, Texas.

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Speaker 1: So, Kelly, do you think Brad is a supervillain planning

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Speaker 1: to push Earth into Jupiter or threatened to?

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Speaker 2: You know, I did wonder about that when I was

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Speaker 2: listening to this question. I'm a little concerned, and you

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Speaker 2: know what, a little concerned in general now that this

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Speaker 2: is something you know on my radar to worry about.

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Speaker 2: And then too, I'm a little worried about Brad in particular.

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Speaker 1: A couple of red flags here. Yeah, I'm not sure

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Speaker 1: in his question if he's worried about this or excited

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Speaker 1: about it, He's like, let's do the experiment.

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Speaker 2: Yeah, yeah, hard to say, hard to say. Maybe we

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Speaker 2: shouldn't give him the answer m exact.

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Speaker 1: I worry about that. Like when the kid wrote to

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Speaker 1: me and asked me what it would take to blow

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Speaker 1: up Mars. I was like, hmm, should I really be

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Speaker 1: telling a ten year old how to destroy a planet?

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Speaker 2: Well, but on the other hand, you know, you hope

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Speaker 2: they don't wield that sort of power, didn't do anything

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Speaker 2: about the information.

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Speaker 1: Who knows what today's ten year olds will do in

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Speaker 1: twenty or thirty years.

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Speaker 2: Right, that's true, that's true, and you'll beat a blame, Daniel,

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Speaker 2: accept that blame.

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Speaker 1: But today we're here to answer Brad's question as a

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Speaker 1: hypothetical science question about something we hope will never happen,

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Speaker 1: which does reveal a lot of really interesting solar system physics.

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Speaker 1: So let's get into it.

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Speaker 2: And I think we should probably start with what is

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Speaker 2: spaghetification because that is clearly one of the best scientific

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Speaker 2: terms our community has ever come up with.

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Speaker 1: Absolutely. Spaghetification is usually used to describe what happens to

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Speaker 1: an object as it approaches a black hole, in that

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Speaker 1: you won't just fall in, you'll be torn apart into

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Speaker 1: spaghetti essentially before you actually fall into the black hole.

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Speaker 1: And this doesn't just happen around black holes. It happens

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Speaker 1: all the time in strong gravitational environments. In fact, it's

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Speaker 1: happening to you, right now, and it's happening to the moon.

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Speaker 1: It's the result of tidal forces. And the reason simply

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Speaker 1: is that the force of gravity depends on distance. So

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Speaker 1: if you're falling into a black hole or you're orbiting

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Speaker 1: a planet or whatever, and your feet are closer than

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Speaker 1: your head than your feet have a stronger gravitational force

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Speaker 1: on them than your head does, and effectively, that's a

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Speaker 1: force pulling your feet away from your head. And if

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Speaker 1: that force is strong enough, it will pull your head

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Speaker 1: off your body or your feet off of your head,

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Speaker 1: depending on your perspective.

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Speaker 2: I'm going to be honest here, I feel like you've

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Speaker 2: sort of de excitified spaghetti cation for me by being like,

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Speaker 2: it's just a kind of title force. It's like, what's happening.

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Speaker 5: To the moon.

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Speaker 2: And I'm like, oh, but I'm spaghetific. That's not what

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Speaker 2: I imagined in my head.

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Speaker 1: Uh, you're imagining some sort of black hole magic.

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Speaker 2: Yes, yes, I thought this was a specific black holy

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Speaker 2: thing and that spighetification really, you know, required you to

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Speaker 2: be thin like a noodle.

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Speaker 1: But okay, physics has been ruining things since fifteen eighty

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Speaker 1: four or whatever.

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Speaker 2: Oh, and what happened in particular in fifteen eighty four.

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Speaker 2: Daniel I just.

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Speaker 1: Made it that date. I was referencing one of Zach's comics.

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Speaker 2: I can't remember what year he had on this or

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Speaker 2: why he picked it.

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Speaker 1: I think it was supposed to be like Galleo's experiments

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Speaker 1: or Bacon or somebody like that. Anyway, the point is

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Speaker 1: that tidal forces are a thing. So if you approach Jupiter,

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Speaker 1: for example, then the difference in forces between one side

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Speaker 1: of your object and the other side of your object,

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Speaker 1: those are the tidal forces. And that's why we have

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Speaker 1: tides on the Earth, because the Moon pulls on one

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Speaker 1: side of the Earth more strongly than on the other

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Speaker 1: side of the Earth, making it a little bit of

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Speaker 1: a football, and the Earth it's the same thing to

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Speaker 1: the Moon, and that's why the Moon is locked in place.

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Speaker 1: It's called tidally locked because there's a little bit of

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Speaker 1: a football and it's hard for it to spin away

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Speaker 1: from having the point a bit of its football aligned

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Speaker 1: with the point a bit of the Earth's football.

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Speaker 2: Okay, but so Jupiter is much bigger than the Moon,

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Speaker 2: so is you know you said that when the force

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Speaker 2: gets hard it could like pop a head off. Is

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Speaker 2: Earth's metaphorical head gonna pop off towards Jupiter or is

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Speaker 2: it just gonna get like weird tides.

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Speaker 1: Yes, So there's a boundary called the Roche limit. If

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Speaker 1: you get closer than that, you get torn into pieces.

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Speaker 1: If you're further away from that, you don't. And that's

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Speaker 1: why some planets have rings and some planets have moons.

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Speaker 1: If your moon is further away than the Roche limit,

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Speaker 1: it stays together. Local gravity winds over the tidal forces.

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Speaker 1: If you get too close, then it gets torn apart

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Speaker 1: into a ring because the tidal forces overcome the internal gravity.

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Speaker 1: So that's the Roche limit. So what happens as the

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Speaker 1: Earth approaches Jupiter, Well, the roach limit for a solid

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Speaker 1: body like the Earth is actually inside the cloud tops

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Speaker 1: of Jupiter. Jupiter is a gas giant, and the outer

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Speaker 1: layer is like fifty kilometers of just clouds blow which

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Speaker 1: you have like gaseous hydrogen, and then liquid hydrogen, and

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Speaker 1: then this crazy helium neon rain, and then ocean of

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Speaker 1: metallic hydrogen before you get to the icy, rocky core.

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Speaker 1: So the Earth would sink into the clouds without getting

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Speaker 1: torn apart. It would get torn apart after it already

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Speaker 1: passes into the clouds.

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Speaker 2: Okay, So at that point we are closer to Jupiter

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Speaker 2: than Jupiter's rings. Right, So Earth's not going to become

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Speaker 2: like a ring of Jupiter. It's going to get torn

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Speaker 2: apart and then rain down on Jupiter. Is Jupiter the

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Speaker 2: planet that has the diamond rain?

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Speaker 1: I think that's Saturn. Ah, it is so disappointing thing. Yesh, Jupiter, yawn.

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Speaker 2: Come on, Jupiter, step up your game man.

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Speaker 1: All right. So now we have a collision of an

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Speaker 1: entire Earth, right, it's whole. It has not been pulled

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Speaker 1: apart by the tidal forces of Jupiter, and it hits Jupiter,

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Speaker 1: and Brad asks like, what's going to happen? And is

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Speaker 1: it going to pass in and be absorbed to hit

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Speaker 1: the solid core? And you're definitely not going to make

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Speaker 1: it all the way to the solid core because even

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Speaker 1: though Jupiter is a gas giant, it has like layers

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Speaker 1: and layers of hydrogen. That hydrogen is dense, and atmospheres

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Speaker 1: have friction. Even here on Earth, where atmosphere is pretty

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Speaker 1: low density compared to the Jovian atmosphere, you know, there's

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Speaker 1: re entry. If a rocket or an asteroid tries to

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Speaker 1: enter the Earth's atmosphere. There's a lot of friction from

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Speaker 1: the atmosphere and you get all this heat, and most

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Speaker 1: things that hit the Earth's atmosphere don't make it to

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Speaker 1: the surface. Same principle applies when the Earth hits the

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Speaker 1: Jovian atmosphere. Okay, and so what's going to happen is

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Speaker 1: you're going to compress the Jovian atmosphere, which is going

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Speaker 1: to heat it up, turn it into plasma, and that's

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Speaker 1: going to vaporize the crust and the mantle of the Earth. Yeah. Bad,

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Speaker 1: And so essentially a massive energy release. Here did a

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Speaker 1: little bit of the back of the envelope calculation, and

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Speaker 1: assuming that the Earth hits at like sixty kilometers per second,

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Speaker 1: which is, you know, fast but not super fast for

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Speaker 1: Solar system speeds, you're gonna release ten to the eighteen

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Speaker 1: megatons of TNT. Wow. And you might be like, I

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Speaker 1: don't know what that number means. Well, the Hiroshima explosion

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Speaker 1: was fifteen kilotons. This is ten to the eighteen mega tons.

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Speaker 1: So it's like so much bigger. And you know, I

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Speaker 1: mean the entire Earth is essentially a bomb, and a

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Speaker 1: lot of that mass is converted into energy. So it's

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Speaker 1: an enormous explosion. You're gonna get like a fireball rising

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Speaker 1: above the surface of Jupiter. It's gonna be much bigger

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Speaker 1: than the volume of the Earth. And you're gonna have

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Speaker 1: shock waves in the Jovian atmosphere which probably will last

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Speaker 1: for years. You may even leave a spot on Jupiter.

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Speaker 1: It's very unlikely you're gonna make it all the way

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Speaker 1: to the core because you've got lots of dense layers

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Speaker 1: before you get there. But yeah, it's gonna be a

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Speaker 1: huge impact. But remember Jupiter is huge compared to the Earth, Like,

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Speaker 1: it's so much bigger than the Earth that even though

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Speaker 1: this is an enormous amount of energy and would devastate

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Speaker 1: the Earth vaporized essentially, Jupiter is gonna mostly shrug it off.

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Speaker 2: Oh man, that's a little insulting. Every human I've ever

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Speaker 2: known or loved disappears and Jupiter's like, eh, okay. Well,

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Speaker 2: so say at this point, when this happens, we have

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Speaker 2: a self sustaining settlement on Mars. If the Martians were

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Speaker 2: like in the right position, could they see this or

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Speaker 2: would the act of Jupiter moving towards Earth have destroyed

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Speaker 2: Mars on the way or thrown Mars off orbit. This

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Speaker 2: is probably unfair. It's a totally different question. But am

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Speaker 2: I asking you anyway? Daniel?

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Speaker 1: Oh? I see well, I was imagining that the Earth

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Speaker 1: is getting tossed into Jupiter. Read when Jupiter is like

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Speaker 1: bullying its way into the inner Solar system. Oh okay,

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Speaker 1: so the Martians have a nice view of Earth shooting

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Speaker 1: by and then they yeah, they could watch Jupiter as

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Speaker 1: it gets impacted. In fact, we had ringside seats to

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Speaker 1: a similar event in the nineties.

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Speaker 2: And I think you told me that you were at

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Speaker 2: a telescope watching that, right, Yeah, I.

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Speaker 1: Had a super fast camera hooked up to a telescope

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Speaker 1: to watch this collision. This is in the mid nineties

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Speaker 1: comet Shoemaker Levee impacted Jupiter and created all these fireballs.

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Speaker 1: Now the comet not nearly the size of the Earth,

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Speaker 1: of course, but still very very dramatic. And what happened

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Speaker 1: is that this comet, which used to be orbiting the Sun,

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Speaker 1: got captured by Jupiter. So now it was orbiting Jupiter

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Speaker 1: sometime in the sixties and in the early nineties it

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Speaker 1: passed very close to Jupiter, so Jupiter tore it apart.

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Speaker 1: It went within the roch limit, not actually within the clouds.

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Speaker 1: The roach limit weirdly and confusingly depends on the object,

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Speaker 1: Like if you're made out of diamond, then your rochal

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Speaker 1: limit is much closer. You have to get much closer

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Speaker 1: to get torn apart than if you're made out of

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Speaker 1: like cotton candy. Right, And so this comic got torn

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Speaker 1: apart into twenty one pieces, which they labeled ABCD all

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Speaker 1: the way up to w NASA.

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Speaker 2: Very creative, of course they did. That was an opportunity

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Speaker 2: for creativity. So they had to pass it by and.

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Speaker 1: Then it's swung around one more time, and over six

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Speaker 1: days in nineteen ninety four, each piece took turns smacking

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Speaker 1: into Jupiter. Wo really amazing, and everyone on Earth was

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Speaker 1: like turning their telescopes to it and watching these pieces hit.

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Speaker 1: And the biggest spot is the one where the g

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Speaker 1: fragment hit, and so you can imagine what that spot

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Speaker 1: might be called.

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Speaker 2: I was just thinking that, but this is a children's show.

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Speaker 1: Exactly, and created a huge dark spot. There was a

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Speaker 1: fireball and a dark spot the width of the Earth.

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Speaker 2: Wow.

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Speaker 1: Right now, this fragment is a piece of a comet,

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Speaker 1: which is tiny compared to the Earth, but it created

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Speaker 1: a big spot the size of the Earth that was

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Speaker 1: visible for a year. So we've seen this kind of

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Speaker 1: impact much smaller, So essentially you just scale this up

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Speaker 1: much more dramatically, but still small compared to Jupiter.

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Speaker 2: Amazing. I wish I had watched them. That wasn't on

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Speaker 2: my radar because I didn't have amazing friends like you

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Speaker 2: back then. You wouldn't have let me go astray. But

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Speaker 2: that's all right.

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Speaker 1: I was in college at the time, and I was

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Speaker 1: home over the summer doing a research project on plasma physics,

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Speaker 1: and we had a super fast camera that we were

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Speaker 1: using to image what happened when you drop a little

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Speaker 1: pellet of fuel into the fusion plasma. And the guy

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Speaker 1: I worked for also had a telescope and he was like,

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Speaker 1: let's point this thing at Jupiter. So he connected the

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Speaker 1: camera to the telescope, pointed to Jupiter, and we had

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Speaker 1: one of the fastest digital cameras around at the time

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Speaker 1: for scientific applications, so we were hoping to have like

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Speaker 1: the highest time resolution photographs of this impact. But just

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Speaker 1: as the impact was going to happen, it went over

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Speaker 1: the horizon, so we got pictures of the fireball rising

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Speaker 1: over Jupiter, but not the impact itself. But it was

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Speaker 1: a lot of fun anyway.

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Speaker 2: So wait, this was ninety four though, is that right?

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Speaker 1: Yeah?

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Speaker 2: Okay, so I was twelve, so I probably I was

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Speaker 2: listening to Silverchair and I didn't care about anything other

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Speaker 2: than Silverchair.

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Speaker 1: So important stuff, important.

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Speaker 2: Stuff, ohs that way, at the time, the rest of us.

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Speaker 1: Were learning about the future impact of Earth on Jupiter.

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Speaker 2: But you know whatever, Well, I was having a good time,

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Speaker 2: so I wouldn't change it for anything, all right. Brad

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Speaker 2: asked if there was any chance we'd get ejected from

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Speaker 2: the Solar system, But you didn't mention that as a

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Speaker 2: as an option, so that's not something that would happen.

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Speaker 1: It could happen, It depends on how accurately Brad and

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Speaker 1: his supervillain team aim the Earth at Jupiter. One possibility

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Speaker 1: is it hits Jupiter right. Another possibility is that it's

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Speaker 1: captured and orbit Jupiter. And this has happened to a

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Speaker 1: bunch of stuff. We think that many of the moons

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Speaker 1: of Jupiter didn't form with Jupiter but were captured by

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Speaker 1: it later. But it's a little bit unlikely because for

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Speaker 1: that to happen, you have to be only at the

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Speaker 1: right angle and the right velocity at the right location

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Speaker 1: to get the orbital mechanics to work out. So more

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Speaker 1: likely you're either going to hit Jupiter or you're going

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Speaker 1: to get ejected from the Solar System because you're going

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Speaker 1: to have a gravitational interaction with Jupiter, which is then

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Speaker 1: going to throw you out of the Solar System.

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Speaker 2: All right, well, one way or another. I think someone

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Speaker 2: should be keeping a close eye on Brad and let's

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Speaker 2: see if our answer changes Brad's mind about whether or

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Speaker 2: not this is a good idea.

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Speaker 4: Daniel and Kelly, I absolutely love this response. I assure

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Speaker 4: you that I am not a supervillain and have no

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Speaker 4: plans to destroy the planet. It sounds like we would

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Speaker 4: get to watch as we pass into the gas cloud

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Speaker 4: layer before we heat up and explode. I like to

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Speaker 4: know that we would at least have a little impact

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Speaker 4: on Jupiter. I think all we need to know now

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Speaker 4: is where Michael Bay wants to set up the camera

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Speaker 4: to catch it's the greatest collision of all the time.

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Speaker 4: Thanks for all y'all do.

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Speaker 1: All right, we're back and we're answering questions from listeners.

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Speaker 1: Now we're going to take a break from Jupiter themed

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Speaker 1: questions and think about sleeping. Here's a wonderful question from

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Speaker 1: one of our Discord listeners. And if you're not on Discord, Colm,

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Speaker 1: join us on our Discord channel. We have lots of

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Speaker 1: fun conversations about science. We answer questions on there, other

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Speaker 1: people answer questions on there. We have wonderful moderators to

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Speaker 1: keep it a really happy fun family. Colm, join us

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Speaker 1: for science chats on Discord. You can find a link

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Speaker 1: on our website. Anyway, here's the question from our listener.

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Speaker 5: In the episode about sleeping dreams, the topic of circadian

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Speaker 5: rhythms in various animals came up. I was curious how

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Speaker 5: circadian rhythms work in animals that never see the sun,

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Speaker 5: like cave dwellers or various deep sea creatures. Thanks for

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Speaker 5: taking the question, looking forward to the answer.

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Speaker 2: Bye, all right, t to the j on Discord. I

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Speaker 2: gotta say, you know, this question came in and I thought,

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Speaker 2: all right, circadian rhythms. I'm a biologist. I should be

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Speaker 2: able to knock this answer out pretty quick. I don't

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Speaker 2: know anything about circadian rhythms. It turns out, oh no.

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Speaker 1: This was biology is a big field.

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Speaker 2: That's what I'm saying, but I really enjoyed the opportunity

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Speaker 2: to get to dig into circadian rhythms again. This is

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Speaker 2: one of the things I love about the questions we

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Speaker 2: get from listeners. There's so many things I thought I

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Speaker 2: understood and then they give me a chance to dig

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Speaker 2: into them, and I learned so much. So uh, circadian rhythms.

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Speaker 2: Circadian comes from the words circa diaz, which means approximately

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Speaker 2: a day. And I'm you know, I don't know, maybe

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Speaker 2: that's Latin. I probably pronounced it wrong, but you all

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Speaker 2: know what I'm saying. So it's all right. We're good

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Speaker 2: and nobody expects me to pronounce things right at this point.

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Speaker 1: That's not what they're here for, Kelly, is not.

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Speaker 2: What you're here for. So circadian rhythms are like internal

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Speaker 2: rhythms that happen on an approximately twenty four hour cycle,

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Speaker 2: and they're entrained or they're sort of like synced up

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Speaker 2: based on outside signals like light.

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Speaker 1: But why do you say approximate? I mean, the earth

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Speaker 1: cycle is pretty crisp. Wouldn't we do best being closely

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Speaker 1: linked to it? Why are you saying approximate?

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Speaker 2: Because you know it's just not perfect and some people

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Speaker 2: have cycles that are a little bit longer than twenty four.

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Speaker 2: Some people have cycles that are a little bit shorter

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Speaker 2: than twenty four. We think this contributes to why some

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Speaker 2: people are mourning people and some people are night people.

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Speaker 2: And then if you're talking about organisms other than humans,

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Speaker 2: you can get some other slightly different sorts of signals

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Speaker 2: that are approximately twenty four hours.

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Speaker 1: So then what parts of the human body are affected

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Speaker 1: by it? Obviously you sleep in this sort of twenty

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Speaker 1: four hour cycle. Is there other stuff going on also?

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Speaker 2: Yeah, lots of things. So like sleep is important, metabolism

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Speaker 2: is also important. Like your body temperature is impacted by

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Speaker 2: circadian rhythms.

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Speaker 1: Right, metabolism, So that is that why I shouldn't eat

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Speaker 1: chips at ten pm?

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Speaker 2: That could partly be it or be involved. I think

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Speaker 2: cortisol is to some extent involved in helping with digestion

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Speaker 2: and stuff, and so your cortisol kind of peaks at

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Speaker 2: times of day when you're like expected to be hungry

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Speaker 2: and expected to be eating.

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Speaker 1: What's cortisol?

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Speaker 2: Cortisol is a hormone that folks usually associate with recovery

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Speaker 2: from stress. So when you get stressed out by something,

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Speaker 2: your body releases cortisol, and then cortisol helps your body

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Speaker 2: sort of return to homeostasis or like a normal state

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Speaker 2: after you've been stressed out.

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Speaker 1: Cortisol sounds great, as you can say more of that.

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Speaker 2: Well, if you are, like, you know, running away from

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Speaker 2: a lion, cortisol is great, like it releases a bunch

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Speaker 2: of energy all at once that you can outrun the lion,

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Speaker 2: and then when you're in a safe spot, it helps

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Speaker 2: you sort of return to normal. But if your cortisol

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Speaker 2: level is elevated for a very long time, you can

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Speaker 2: start having diseases because you're constantly in a stressed out state.

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Speaker 2: So cortisol is more supposed to like get you out

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Speaker 2: of an intent hence acute situation, but if it's elevated chronically,

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Speaker 2: it can be bad. And there's a really interesting book

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Speaker 2: on this called Why Zebras Don't Get Ulcers by Robert Sippolski. Cool.

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Speaker 1: All right, yeah, well, I wonder if zebra's go to

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Speaker 1: my physics faculty meetings if they feel stressed out and

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Speaker 1: need cortisol afterwards.

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Speaker 2: Oh yeah, faculty meetings. I think what I'm stressed out

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Speaker 2: about in faculty meetings is that I could be spending

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Speaker 2: my time way better doing anything else. But you know,

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Speaker 2: I haven't had to go to faculty meetings for a while,

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Speaker 2: so that's great.

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Speaker 1: Dark wasn't Today is not about silly arguments and physics

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Speaker 1: faculty meetings. It's about the rhythms of the body. So

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Speaker 1: you're telling us that these things happen and impact sleep, metabolism,

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Speaker 1: and temperature. But what's the mechanism for it? Like, what

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Speaker 1: is driving it?

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Speaker 4: Yeah?

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Speaker 2: Okay, So most of the work that we've done to

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Speaker 2: figure out the mechanism has been done in organisms like

438
00:20:44,680 --> 00:20:48,000
Speaker 2: mice and fruitflies. But here's how we think that it works.

439
00:20:48,160 --> 00:20:50,280
Speaker 2: How we're guessing that it works in humans based on

440
00:20:50,320 --> 00:20:53,080
Speaker 2: what we've seen in lab animals. So there's a little

441
00:20:53,119 --> 00:20:56,560
Speaker 2: part of your brain called the hypothalamus, and inside of

442
00:20:56,560 --> 00:21:00,280
Speaker 2: the hypothalamis there's a little region called the super chiasmatic

443
00:21:00,400 --> 00:21:02,800
Speaker 2: nucleus or the SCN. Because I'm not going to try

444
00:21:02,880 --> 00:21:03,680
Speaker 2: say that a bunch.

445
00:21:03,480 --> 00:21:05,920
Speaker 1: Of times it sounds a lot like super cool, fudulistic,

446
00:21:05,960 --> 00:21:08,680
Speaker 1: expire audotious, but all right, yeah, I hear that every

447
00:21:08,680 --> 00:21:09,280
Speaker 1: time you say that.

448
00:21:09,359 --> 00:21:12,719
Speaker 2: Now, okay, no one's going to be able to pay

449
00:21:12,760 --> 00:21:14,439
Speaker 2: attention to the rest of the episode. They're going to

450
00:21:14,480 --> 00:21:18,080
Speaker 2: be singing just like Mary Poppins, but try to focus people,

451
00:21:18,560 --> 00:21:21,160
Speaker 2: all right. So you've got the SCN, and the SCN

452
00:21:21,280 --> 00:21:24,400
Speaker 2: is connected to the optic nerves, and so optic nerves

453
00:21:24,440 --> 00:21:26,480
Speaker 2: these are the nerves that go to your eyes. And

454
00:21:26,480 --> 00:21:29,000
Speaker 2: so we've talked in the past about how your eyes

455
00:21:29,119 --> 00:21:33,080
Speaker 2: have specialized cells called rods and cones, and those help

456
00:21:33,119 --> 00:21:36,479
Speaker 2: you detect like patterns and colors and to see your world.

457
00:21:36,880 --> 00:21:40,760
Speaker 2: But you also have cells that just detect the intensity

458
00:21:40,840 --> 00:21:45,800
Speaker 2: of light, and those cells send information through your optic

459
00:21:45,880 --> 00:21:49,560
Speaker 2: nerve back to the SCN, and your brain uses that

460
00:21:49,640 --> 00:21:52,600
Speaker 2: information to tell the rest of your body how the

461
00:21:52,640 --> 00:21:54,840
Speaker 2: rhythm should be working. And so it does this by

462
00:21:54,880 --> 00:21:58,639
Speaker 2: either sending messages through the nerves or by directing the

463
00:21:58,680 --> 00:22:01,040
Speaker 2: production of hormones that will then go to the rest

464
00:22:01,040 --> 00:22:04,359
Speaker 2: of your body and talk to your cells and basically say, Okay,

465
00:22:04,359 --> 00:22:08,919
Speaker 2: hey guys, it's morning. And when it's mourning, your body increases,

466
00:22:09,119 --> 00:22:13,680
Speaker 2: its heart rate, increases, its blood pressure, increases temperature. Your

467
00:22:13,680 --> 00:22:17,119
Speaker 2: body is not making melatonin at this point. Melatonin is

468
00:22:17,119 --> 00:22:20,480
Speaker 2: associated with sleep. So this is generally how your body

469
00:22:20,520 --> 00:22:24,760
Speaker 2: collects the information about what should be setting the timing

470
00:22:24,800 --> 00:22:28,359
Speaker 2: for the rhythm. But each one of your cells also

471
00:22:28,480 --> 00:22:30,159
Speaker 2: has its own circadian clock.

472
00:22:30,119 --> 00:22:32,840
Speaker 1: So we have these special cells in our eyes. Instead

473
00:22:32,840 --> 00:22:35,240
Speaker 1: of just using the information which already exists in the

474
00:22:35,359 --> 00:22:38,159
Speaker 1: rods and cones, we like evolve the separate pathway just

475
00:22:38,240 --> 00:22:40,840
Speaker 1: for this. Wow, this is pretty weird engineering.

476
00:22:41,000 --> 00:22:43,760
Speaker 2: Well, but it's detecting something different. Your rods and your

477
00:22:43,760 --> 00:22:47,720
Speaker 2: cones are detecting like colors and you know, patterns of

478
00:22:47,840 --> 00:22:50,800
Speaker 2: like dark against light and stuff like that. These cells

479
00:22:50,800 --> 00:22:54,360
Speaker 2: are just detecting the intensity of the light that's coming in.

480
00:22:54,800 --> 00:22:57,320
Speaker 2: So you're like, oh it's dawn now, or oh it's noon,

481
00:22:57,720 --> 00:22:59,119
Speaker 2: and so it's detecting that.

482
00:22:59,400 --> 00:23:01,439
Speaker 1: I feel like I could write a computer program to

483
00:23:01,600 --> 00:23:04,399
Speaker 1: extract the same information from the data produced by the

484
00:23:04,400 --> 00:23:07,320
Speaker 1: codes and the rods. But that's fine. Obviously the brain

485
00:23:07,359 --> 00:23:09,639
Speaker 1: is not engineered by physicists.

486
00:23:09,320 --> 00:23:11,920
Speaker 2: And that's not how evolution works. Evolution doesn't say, Okay,

487
00:23:12,000 --> 00:23:13,440
Speaker 2: I'm going to start from scratch and come up with

488
00:23:13,480 --> 00:23:15,080
Speaker 2: the best system. It's like, well, what do I have

489
00:23:15,160 --> 00:23:16,280
Speaker 2: and how can I work with it?

490
00:23:16,400 --> 00:23:18,720
Speaker 1: I just think it's a fascinating clue that something happened

491
00:23:18,760 --> 00:23:21,520
Speaker 1: there that this is what we ended up with. You know,

492
00:23:21,640 --> 00:23:24,000
Speaker 1: It's just another example of how like obviously this is

493
00:23:24,040 --> 00:23:27,719
Speaker 1: not well organized. Just what kind of worked? And so

494
00:23:27,760 --> 00:23:29,920
Speaker 1: do we know this because we've like done studies in

495
00:23:30,000 --> 00:23:32,719
Speaker 1: mice where we've like tweaked those cells or got rid

496
00:23:32,760 --> 00:23:34,840
Speaker 1: of those cells, or like shined light on those cells

497
00:23:34,880 --> 00:23:37,000
Speaker 1: or something, and it's changed the way the mice behave.

498
00:23:37,280 --> 00:23:39,159
Speaker 2: Yeah, so if you mess up a mouse or a

499
00:23:39,200 --> 00:23:43,840
Speaker 2: flies SCN, then they'll start free cycling. So essentially they

500
00:23:43,880 --> 00:23:46,240
Speaker 2: won't show these twenty four hour cycles.

501
00:23:46,440 --> 00:23:48,080
Speaker 1: They're not so xpl a doocious anymore.

502
00:23:49,359 --> 00:23:51,800
Speaker 2: That's right, that's right. It's truly quite atrocious.

503
00:23:51,880 --> 00:23:56,400
Speaker 1: All right, So that's wrong. Okay, that was pretty good.

504
00:23:56,520 --> 00:23:57,800
Speaker 1: That was really good.

505
00:23:58,000 --> 00:23:59,920
Speaker 2: Grudgingly patting me on the back there.

506
00:24:00,600 --> 00:24:02,600
Speaker 1: I was so excited about my next question. I didn't

507
00:24:02,760 --> 00:24:05,760
Speaker 1: registering a joke, but that was excellent. Yeah, ten points

508
00:24:05,760 --> 00:24:09,800
Speaker 1: for Kelly for everybody's keeping score. So you're telling us

509
00:24:09,880 --> 00:24:12,879
Speaker 1: that not only these light signals tell us when to

510
00:24:12,880 --> 00:24:16,720
Speaker 1: be fragilistic, but also the rest of our body responds

511
00:24:16,760 --> 00:24:17,320
Speaker 1: in some way.

512
00:24:17,720 --> 00:24:19,959
Speaker 2: Yeah. Okay, So first I just want to mention real

513
00:24:20,040 --> 00:24:24,600
Speaker 2: quick that that organisms from bacteria to humans show these clocks,

514
00:24:24,680 --> 00:24:28,200
Speaker 2: and so this is like not every organism uses their

515
00:24:28,680 --> 00:24:31,520
Speaker 2: SCN and so this sort of like feeds back on

516
00:24:31,520 --> 00:24:33,760
Speaker 2: our conversation about how you just use what you have.

517
00:24:33,920 --> 00:24:36,440
Speaker 2: This has been going on for a really long time anyway.

518
00:24:37,160 --> 00:24:40,240
Speaker 2: So not every single cell has its own circadian clock.

519
00:24:40,480 --> 00:24:43,280
Speaker 2: I misspoke earlier, but many cells, even if you take

520
00:24:43,320 --> 00:24:45,600
Speaker 2: them out of the body and you put them in

521
00:24:45,640 --> 00:24:48,560
Speaker 2: like a petri dish, they will show like a twenty

522
00:24:48,680 --> 00:24:52,119
Speaker 2: four hour schedule for the activities that they do, like

523
00:24:52,160 --> 00:24:54,960
Speaker 2: they've repair DNA at a certain time, you know, stuff

524
00:24:55,000 --> 00:24:56,960
Speaker 2: like that. And so here's how we think that works.

525
00:24:57,119 --> 00:25:02,400
Speaker 2: So your cell is making a a protein called clock protein.

526
00:25:03,240 --> 00:25:08,280
Speaker 2: The clock protein at dawn moves into your nucleus where

527
00:25:08,280 --> 00:25:12,520
Speaker 2: the genetic information is stored, and it binds to literally

528
00:25:12,720 --> 00:25:15,880
Speaker 2: thousands of different sites on your DNA. And when it binds,

529
00:25:15,960 --> 00:25:19,199
Speaker 2: it's telling your DNA to start making certain things. And

530
00:25:19,240 --> 00:25:21,320
Speaker 2: it could be making certain hormones, like it can say, hey,

531
00:25:21,359 --> 00:25:23,879
Speaker 2: start making that cortisol. It could start doing you know,

532
00:25:23,920 --> 00:25:26,640
Speaker 2: whatever is needed to increase body temperature or heart rate,

533
00:25:26,720 --> 00:25:30,040
Speaker 2: et cetera. So thousands of things are turned on when

534
00:25:30,080 --> 00:25:32,480
Speaker 2: your clock proteins go in there and bind to lots

535
00:25:32,520 --> 00:25:35,600
Speaker 2: of different spots. Another thing that's being made. Though, during

536
00:25:35,640 --> 00:25:37,919
Speaker 2: the course of the day are proteins that will shut

537
00:25:37,920 --> 00:25:42,359
Speaker 2: this down. And these proteins are called period proteins, And

538
00:25:42,400 --> 00:25:45,120
Speaker 2: so the period proteins will build up over the course

539
00:25:45,119 --> 00:25:47,200
Speaker 2: of the day because the clock proteins said, hey, start

540
00:25:47,200 --> 00:25:49,480
Speaker 2: making these, and at some point they've built up to

541
00:25:49,560 --> 00:25:52,160
Speaker 2: high enough levels that now they go into the nucleus

542
00:25:52,440 --> 00:25:55,360
Speaker 2: and they pull the clock proteins off of the DNA

543
00:25:56,040 --> 00:25:58,200
Speaker 2: and that stops all of the stuff that the clock

544
00:25:58,200 --> 00:26:01,560
Speaker 2: proteins had been turning on and getting made. As the

545
00:26:01,640 --> 00:26:05,439
Speaker 2: night goes on, the period proteins break down and go away,

546
00:26:05,840 --> 00:26:08,400
Speaker 2: and then the next morning the clock proteins go back

547
00:26:08,440 --> 00:26:09,880
Speaker 2: in and the cycle starts again.

548
00:26:10,200 --> 00:26:13,160
Speaker 1: So, like many clocks, you have some sort of process

549
00:26:13,200 --> 00:26:16,320
Speaker 1: which has a natural timescale built into it, right, and

550
00:26:16,400 --> 00:26:19,399
Speaker 1: so there is chemistry where things are slashing back and

551
00:26:19,480 --> 00:26:22,359
Speaker 1: forth and naturally at the same rate as our twenty

552
00:26:22,359 --> 00:26:24,160
Speaker 1: four hour cycle. Is that what's happening?

553
00:26:24,440 --> 00:26:26,879
Speaker 2: Yeah, yeah, that's a good summary. And I saw you.

554
00:26:27,080 --> 00:26:29,920
Speaker 2: Yeah cool looking something up? Was I wrong about something

555
00:26:30,000 --> 00:26:31,159
Speaker 2: or was it unrelated?

556
00:26:31,560 --> 00:26:34,200
Speaker 1: I was wondering if clock was an acronym for something

557
00:26:34,240 --> 00:26:35,400
Speaker 1: in a really tortured way.

558
00:26:35,520 --> 00:26:39,440
Speaker 2: But oh, okay, right, I.

559
00:26:39,359 --> 00:26:42,239
Speaker 1: Was hoping it stood for something ridiculous. Okay, because if

560
00:26:42,280 --> 00:26:44,399
Speaker 1: it was a physics acronym, it definitely would have a

561
00:26:44,480 --> 00:26:45,200
Speaker 1: ridiculous name.

562
00:26:45,359 --> 00:26:49,880
Speaker 2: Got it anyway, So light is important for determining these cycles, right,

563
00:26:49,920 --> 00:26:52,720
Speaker 2: But it also is fine tuned by things like the

564
00:26:52,720 --> 00:26:55,959
Speaker 2: temperature you find yourself at when during the day you're eating,

565
00:26:56,080 --> 00:26:58,520
Speaker 2: and these cues are important for other animals as well.

566
00:26:58,560 --> 00:27:01,000
Speaker 2: So it's not just light, but light does seem to

567
00:27:01,000 --> 00:27:02,719
Speaker 2: be a super important factor.

568
00:27:02,840 --> 00:27:04,800
Speaker 1: So it's interesting you have several different kinds of things

569
00:27:04,840 --> 00:27:07,000
Speaker 1: going on. Can they get out of sync or is

570
00:27:07,000 --> 00:27:08,840
Speaker 1: there something that tries to keep them in harmony.

571
00:27:09,080 --> 00:27:12,480
Speaker 2: Well, so, once you develop a cycle, your body is

572
00:27:12,560 --> 00:27:15,760
Speaker 2: pretty good at keeping that cycle going. So like if

573
00:27:15,800 --> 00:27:19,000
Speaker 2: you stayed in a dark room for two days, your

574
00:27:19,000 --> 00:27:21,320
Speaker 2: body would still have some of its normal cycle. It's

575
00:27:21,359 --> 00:27:24,560
Speaker 2: not like it breaks down immediately, but over time, if

576
00:27:24,600 --> 00:27:26,840
Speaker 2: you deprive your body of that light queue or you

577
00:27:26,920 --> 00:27:29,720
Speaker 2: mess your cues up, then you can start having problems.

578
00:27:29,760 --> 00:27:32,239
Speaker 2: So for example, if you work the night shift, you know,

579
00:27:32,359 --> 00:27:34,040
Speaker 2: any of us who have had jet lag have had

580
00:27:34,080 --> 00:27:37,680
Speaker 2: like a temporary period where circadian rhythm was like something's

581
00:27:37,760 --> 00:27:40,840
Speaker 2: not right, and then it's had to get back to normal.

582
00:27:41,760 --> 00:27:45,280
Speaker 2: But being off of your normal circadian rhythm too often,

583
00:27:45,359 --> 00:27:50,879
Speaker 2: for example, working the night shift increases your risk of diabetes, obesity, depression, dementia,

584
00:27:50,920 --> 00:27:53,440
Speaker 2: and some kinds of cancer. So these circadian rhythms seem

585
00:27:53,480 --> 00:27:56,200
Speaker 2: to be important for a lot of reasons, at least

586
00:27:56,200 --> 00:27:56,719
Speaker 2: for humans.

587
00:27:56,920 --> 00:28:00,800
Speaker 1: Wow, and how widespread are circadian rhythm that everything on

588
00:28:00,840 --> 00:28:02,400
Speaker 1: Earth has a circadian rhythm?

589
00:28:02,440 --> 00:28:07,040
Speaker 2: Well, so like bacteria, humans, plants, lots of stuff has

590
00:28:07,080 --> 00:28:10,000
Speaker 2: circadian rhythms. But our listener had a really great question,

591
00:28:10,119 --> 00:28:12,720
Speaker 2: which is how on Earth do you have a circadian

592
00:28:12,800 --> 00:28:15,000
Speaker 2: rhythm if you live in a place with no light?

593
00:28:16,000 --> 00:28:19,320
Speaker 2: And so the three different situations that I looked into

594
00:28:19,359 --> 00:28:22,040
Speaker 2: where there's no light are if you are, for example,

595
00:28:22,119 --> 00:28:24,520
Speaker 2: at the North Pole during the time of year where

596
00:28:24,520 --> 00:28:26,000
Speaker 2: you don't see the sun. There's like, I think a

597
00:28:26,040 --> 00:28:28,399
Speaker 2: couple months where that's the case, if you live in

598
00:28:28,440 --> 00:28:31,480
Speaker 2: a cave, or if you live in the deep sea.

599
00:28:31,520 --> 00:28:34,120
Speaker 2: And then there's also organisms like naked mole rats that

600
00:28:34,280 --> 00:28:37,280
Speaker 2: live underground. But I think naked molerats can peek their

601
00:28:37,320 --> 00:28:39,360
Speaker 2: heads out every once in a while and see the

602
00:28:39,400 --> 00:28:42,680
Speaker 2: sun to help in train their clock, so they get

603
00:28:42,680 --> 00:28:45,680
Speaker 2: some light cues still, So let's start with if you

604
00:28:45,720 --> 00:28:49,080
Speaker 2: live far north. So one thing that's important to note,

605
00:28:49,080 --> 00:28:51,000
Speaker 2: which we touched on just a second ago, is that

606
00:28:51,080 --> 00:28:55,600
Speaker 2: clocks don't go away immediately just because you're in total darkness.

607
00:28:55,720 --> 00:28:59,160
Speaker 2: So at the start of the long night, they're probably

608
00:28:59,200 --> 00:29:02,160
Speaker 2: fine because their body hasn't like forgotten the rhythm yet.

609
00:29:02,800 --> 00:29:05,120
Speaker 2: And during the time of year when it's all light,

610
00:29:05,720 --> 00:29:08,920
Speaker 2: they're probably also fine because the intensity of the light

611
00:29:09,200 --> 00:29:12,080
Speaker 2: still changes over the course of the day, and your

612
00:29:12,360 --> 00:29:15,160
Speaker 2: eyes are focusing on light intensity, not just whether it's

613
00:29:15,160 --> 00:29:17,080
Speaker 2: there or not, so they can still keep their rhythms

614
00:29:17,160 --> 00:29:19,960
Speaker 2: at that time of year. But there is a point

615
00:29:20,000 --> 00:29:23,760
Speaker 2: in the winter where their clocks have not had appropriate

616
00:29:23,800 --> 00:29:26,280
Speaker 2: input for long enough because it's been dark for so long,

617
00:29:26,800 --> 00:29:30,200
Speaker 2: and they do seem to stop showing signs of twenty

618
00:29:30,200 --> 00:29:32,440
Speaker 2: four hour cycles if you look at the reindeer, So

619
00:29:32,560 --> 00:29:35,400
Speaker 2: it looks like at some point they do start free

620
00:29:35,400 --> 00:29:39,680
Speaker 2: cycling essentially and their circadian rhythms start to break down. Wow,

621
00:29:39,760 --> 00:29:43,280
Speaker 2: they don't seem to have physiological problems associated with that.

622
00:29:43,680 --> 00:29:45,920
Speaker 2: I'm not quite sure why, but it looks like they

623
00:29:46,000 --> 00:29:47,520
Speaker 2: do break down at some point, So.

624
00:29:47,560 --> 00:29:49,280
Speaker 1: It's bad for them to be in the dark, like

625
00:29:49,360 --> 00:29:51,520
Speaker 1: it would be better if they got light occasionally to

626
00:29:51,520 --> 00:29:53,560
Speaker 1: sort of like correct their cycles or get them back

627
00:29:53,600 --> 00:29:54,040
Speaker 1: on track.

628
00:29:54,280 --> 00:29:56,720
Speaker 2: Yeah, So I was trying to figure out the answer

629
00:29:56,800 --> 00:29:58,840
Speaker 2: to that, and I think that the answer is to

630
00:29:58,880 --> 00:30:03,840
Speaker 2: some extent that it's complicated. So, you know, part of

631
00:30:03,920 --> 00:30:06,360
Speaker 2: why we have cycles is that it helps us figure

632
00:30:06,360 --> 00:30:08,280
Speaker 2: out like when we should be eating and stuff like that.

633
00:30:08,320 --> 00:30:10,280
Speaker 2: And part of that, if you are a wild animal,

634
00:30:10,440 --> 00:30:14,320
Speaker 2: is about when your food is even available, right, But

635
00:30:14,400 --> 00:30:16,520
Speaker 2: if you're in the dark and all the other animals

636
00:30:16,520 --> 00:30:19,000
Speaker 2: are in the dark all the time too, you might

637
00:30:19,040 --> 00:30:21,360
Speaker 2: not need to have a circadian rhythm because it might

638
00:30:21,400 --> 00:30:23,920
Speaker 2: you know, if you're, say you're a fox living in

639
00:30:23,920 --> 00:30:26,880
Speaker 2: the Arctic circle, you want to make sure you're awake

640
00:30:27,240 --> 00:30:29,320
Speaker 2: at the same time as the bunnies. But if it's

641
00:30:29,360 --> 00:30:33,440
Speaker 2: complete darkness and everybody's free cycling, you don't really need

642
00:30:33,480 --> 00:30:35,040
Speaker 2: to get up at a certain time because the bunnies

643
00:30:35,040 --> 00:30:36,840
Speaker 2: could be out there at any time, and so it's

644
00:30:37,200 --> 00:30:41,000
Speaker 2: not a helpful queue anymore to like have your activities

645
00:30:41,000 --> 00:30:42,360
Speaker 2: sync to a certain time of day.

646
00:30:42,640 --> 00:30:44,520
Speaker 1: I was wondering more about the internal stuff, Like you

647
00:30:44,560 --> 00:30:46,720
Speaker 1: mentioned earlier that if your rhythm gets messed up your

648
00:30:46,800 --> 00:30:50,040
Speaker 1: risk for diabetes and cancer and stuff. Is the same

649
00:30:50,080 --> 00:30:52,240
Speaker 1: thing true for reindeer when they're free cycling.

650
00:30:52,320 --> 00:30:54,160
Speaker 2: Yeah, so I don't know the answer for reindeer, but

651
00:30:54,240 --> 00:30:56,520
Speaker 2: I did try to find the answer to that question.

652
00:30:56,640 --> 00:31:00,280
Speaker 2: I was able to find some information about blind cavefish.

653
00:31:00,560 --> 00:31:03,840
Speaker 2: So there are fish that live in caves that have

654
00:31:04,000 --> 00:31:08,760
Speaker 2: closely related ancestors that live outside of caves. Oh, okay,

655
00:31:08,840 --> 00:31:11,880
Speaker 2: And so you can compare you know, essentially these like

656
00:31:12,040 --> 00:31:16,080
Speaker 2: sister species or sibling species and see how they differ.

657
00:31:16,680 --> 00:31:20,880
Speaker 2: And the species that live in caves don't have shorter lives,

658
00:31:20,920 --> 00:31:23,280
Speaker 2: and in a lot of cases they have longer lives

659
00:31:23,360 --> 00:31:26,719
Speaker 2: than their surface living counterparts. Well, okay, and then let

660
00:31:26,720 --> 00:31:28,719
Speaker 2: me tell you about their circadian rhythms. That's the important

661
00:31:28,720 --> 00:31:31,440
Speaker 2: piece here. So people were trying to figure out if

662
00:31:31,560 --> 00:31:35,520
Speaker 2: cavefish have circadian rhythms, and they were trying to figure out, like, okay,

663
00:31:35,520 --> 00:31:39,760
Speaker 2: in the absence of light, how do you do that?

664
00:31:39,880 --> 00:31:42,840
Speaker 2: And so one idea they had was that maybe bats

665
00:31:42,880 --> 00:31:45,280
Speaker 2: that go in and out of the cave are what

666
00:31:45,320 --> 00:31:47,800
Speaker 2: they're queuing into. Because when the bats leave where they

667
00:31:47,840 --> 00:31:50,600
Speaker 2: come back, they poop in the water and that poop

668
00:31:50,720 --> 00:31:53,960
Speaker 2: provides food for a lot of cavefish, right, so maybe

669
00:31:53,960 --> 00:31:56,280
Speaker 2: that's what they're sinking to, but there was no evidence

670
00:31:56,680 --> 00:31:58,720
Speaker 2: that that was actually happening, So it looks like they're

671
00:31:58,760 --> 00:31:59,760
Speaker 2: not sinking to that.

672
00:32:00,040 --> 00:32:01,960
Speaker 1: But there could be a lot of similar effects right

673
00:32:02,160 --> 00:32:04,480
Speaker 1: where things are happening outside the cave, and like even

674
00:32:04,520 --> 00:32:07,640
Speaker 1: the microbes in the air or something like that could

675
00:32:07,720 --> 00:32:11,320
Speaker 1: be affecting. You could be sensing indirectly the fact that

676
00:32:11,360 --> 00:32:13,920
Speaker 1: there's day and night outside the cave from inside the cave.

677
00:32:14,120 --> 00:32:16,400
Speaker 2: Yeah, that's right. But so people have also brought the

678
00:32:16,400 --> 00:32:18,960
Speaker 2: cavefish into the lab, and when they bring them into

679
00:32:19,000 --> 00:32:21,560
Speaker 2: the lab and they expose them to normal light cycles,

680
00:32:22,120 --> 00:32:25,520
Speaker 2: they can develop circadian rhythms. So they still even though

681
00:32:25,520 --> 00:32:28,040
Speaker 2: they don't have eyes, they still must have like the

682
00:32:28,080 --> 00:32:32,000
Speaker 2: cells needed to detect light, and they can develop rhythms.

683
00:32:32,280 --> 00:32:36,240
Speaker 2: But it looks like various parts of their circadian clock

684
00:32:36,280 --> 00:32:37,840
Speaker 2: are messed up. So if you look at things from

685
00:32:37,880 --> 00:32:40,280
Speaker 2: the genetic level, it's kind of messed up, and it

686
00:32:40,320 --> 00:32:43,560
Speaker 2: looks like they also for the most part, are losing

687
00:32:43,640 --> 00:32:47,440
Speaker 2: their circadian rhythms in the cave, but that doesn't seem

688
00:32:47,480 --> 00:32:48,640
Speaker 2: to be shortening their lives.

689
00:32:49,120 --> 00:32:51,320
Speaker 1: Wow, fascinating, Yeah, which.

690
00:32:51,080 --> 00:32:52,840
Speaker 2: Is not what I expected. Like I spent a long

691
00:32:52,880 --> 00:32:55,400
Speaker 2: time being like, well, no, what is the queue? They

692
00:32:55,440 --> 00:32:57,640
Speaker 2: have to have circadian rhythms, And then I found a

693
00:32:57,680 --> 00:33:00,680
Speaker 2: review paper that pretty much was like, the rhythms kind

694
00:33:00,720 --> 00:33:02,920
Speaker 2: of seem to disappear in caves. They're just kind of

695
00:33:03,040 --> 00:33:05,600
Speaker 2: like moving around whenever and sleeping whenever.

696
00:33:05,800 --> 00:33:07,400
Speaker 1: And that's okay, And that's okay.

697
00:33:07,440 --> 00:33:08,160
Speaker 2: We're not judging.

698
00:33:08,240 --> 00:33:11,040
Speaker 1: Teenagers everywhere are like see mom, it's fine for me

699
00:33:11,080 --> 00:33:12,120
Speaker 1: to stay up until two.

700
00:33:11,960 --> 00:33:14,440
Speaker 2: Am, all right, and their rooms are kind of like

701
00:33:14,520 --> 00:33:17,480
Speaker 2: messy caves. And I see lots lots of points of

702
00:33:17,560 --> 00:33:19,440
Speaker 2: comparison here.

703
00:33:20,360 --> 00:33:22,640
Speaker 1: All right, what about at the bottom of the ocean

704
00:33:22,680 --> 00:33:24,480
Speaker 1: where light doesn't filter down?

705
00:33:24,800 --> 00:33:26,720
Speaker 2: Okay, so this is interesting. So after I had finished

706
00:33:26,760 --> 00:33:29,760
Speaker 2: the research on caves, my expectation was that animals that

707
00:33:29,800 --> 00:33:31,840
Speaker 2: live in the deep sea are also going to not

708
00:33:31,920 --> 00:33:34,960
Speaker 2: really show circadian rhythms because they're you know, they're down

709
00:33:35,000 --> 00:33:37,360
Speaker 2: in an area where the light isn't getting to But

710
00:33:37,400 --> 00:33:39,560
Speaker 2: I thought, well, you know, maybe there's still some cues,

711
00:33:39,720 --> 00:33:42,080
Speaker 2: Like a lot of the food that comes to the

712
00:33:42,080 --> 00:33:44,959
Speaker 2: deep sea comes from things just sort of like dying

713
00:33:45,000 --> 00:33:47,640
Speaker 2: and raining down, and I thought, maybe there's like a

714
00:33:47,800 --> 00:33:52,440
Speaker 2: daily pattern to how the food rains down. But this

715
00:33:52,520 --> 00:33:53,920
Speaker 2: is actually really hard to study.

716
00:33:54,120 --> 00:33:56,720
Speaker 1: When the carcass snacks happen, that's really.

717
00:33:56,720 --> 00:33:58,880
Speaker 2: Well, you know, I pay attention to snacks.

718
00:34:01,680 --> 00:34:05,200
Speaker 1: Kids, dead bodies are falling, come on outside. What is

719
00:34:05,240 --> 00:34:06,520
Speaker 1: it like to be a parent at the bottom of

720
00:34:06,560 --> 00:34:06,960
Speaker 1: the ocean.

721
00:34:07,160 --> 00:34:09,680
Speaker 2: I mean, when a whale falls down, it is like

722
00:34:09,880 --> 00:34:15,480
Speaker 2: buffet for months. The videos are messed up. But so

723
00:34:15,800 --> 00:34:17,719
Speaker 2: the way that folks tend to study this is, you know,

724
00:34:17,800 --> 00:34:20,600
Speaker 2: they either take the deep sea animals into the lab,

725
00:34:21,000 --> 00:34:23,240
Speaker 2: but if you bring them into the lab, you're often

726
00:34:23,320 --> 00:34:25,520
Speaker 2: like turning on lights to study them, and so now

727
00:34:25,600 --> 00:34:28,040
Speaker 2: they're in like a not natural environment. And you know,

728
00:34:28,120 --> 00:34:30,640
Speaker 2: labs in general are not like the bottom of the sea.

729
00:34:31,120 --> 00:34:33,080
Speaker 2: But another way that people study it is they will

730
00:34:33,120 --> 00:34:36,759
Speaker 2: put like essentially mobile labs. They'll lower them down to

731
00:34:36,800 --> 00:34:39,000
Speaker 2: the bottom of the sea and then they'll like take

732
00:34:39,040 --> 00:34:41,239
Speaker 2: pictures or videos and try to see if they can

733
00:34:41,440 --> 00:34:44,600
Speaker 2: detect cycles and what's happening down there. But another problem

734
00:34:44,600 --> 00:34:46,960
Speaker 2: there is that they turn on lights often when they

735
00:34:46,960 --> 00:34:49,600
Speaker 2: do that. Yeah, and so this stuff is hard to study.

736
00:34:49,640 --> 00:34:53,240
Speaker 2: But I found a study that did use cameras with lights,

737
00:34:53,320 --> 00:34:56,120
Speaker 2: and they found that a lot of species didn't show

738
00:34:56,640 --> 00:34:58,879
Speaker 2: detectable patterns, but it was also hard to get large

739
00:34:58,920 --> 00:35:01,480
Speaker 2: sample sizes. But they did find that there is a

740
00:35:01,680 --> 00:35:05,040
Speaker 2: kind of worm that lives in a tube and there's

741
00:35:05,160 --> 00:35:07,480
Speaker 2: a pattern to when it sticks its head out of

742
00:35:07,480 --> 00:35:10,279
Speaker 2: the tube to try to get food. They were looking

743
00:35:10,280 --> 00:35:12,759
Speaker 2: at different things that were changing in the environment, and

744
00:35:12,840 --> 00:35:16,360
Speaker 2: it looks like this behavior is correlated with the tides.

745
00:35:16,480 --> 00:35:19,120
Speaker 2: So you can still feel the tides at the bottom

746
00:35:19,120 --> 00:35:21,800
Speaker 2: of the sea. Oh wow, which is amazing. I didn't

747
00:35:21,840 --> 00:35:22,360
Speaker 2: realize that.

748
00:35:22,680 --> 00:35:25,920
Speaker 1: Yeah, thank you Moon, and see it's all connected. Yes,

749
00:35:25,920 --> 00:35:27,440
Speaker 1: it turns out there is a through line for the

750
00:35:27,440 --> 00:35:28,120
Speaker 1: whole episode.

751
00:35:28,360 --> 00:35:28,719
Speaker 5: That's orry.

752
00:35:28,760 --> 00:35:31,879
Speaker 2: I guess. Spaghetification is kind of interesting, but I guess

753
00:35:31,960 --> 00:35:34,080
Speaker 2: so it's not just the tides, but the tides have

754
00:35:34,160 --> 00:35:37,120
Speaker 2: different temperatures, so it could be temperature that's queueing this.

755
00:35:37,320 --> 00:35:37,440
Speaker 3: Yea.

756
00:35:37,640 --> 00:35:40,279
Speaker 2: The tides also can bring food, so maybe it's the

757
00:35:40,320 --> 00:35:44,640
Speaker 2: food that's queuing the clocks. And this information is largely observational,

758
00:35:44,680 --> 00:35:46,399
Speaker 2: so there's still a lot that we have left to learn,

759
00:35:46,840 --> 00:35:50,320
Speaker 2: but some indication that tides can be what's impacting timing

760
00:35:50,360 --> 00:35:54,400
Speaker 2: in the deep sea and that's literally everything I know

761
00:35:54,480 --> 00:35:57,440
Speaker 2: about circadian clocks, because this is complicated.

762
00:35:57,000 --> 00:35:59,040
Speaker 1: All right, So bottom line for us, what do we

763
00:35:59,080 --> 00:36:01,600
Speaker 1: know about how circadie rhythms work? And animals that never

764
00:36:01,640 --> 00:36:02,200
Speaker 1: see the sun.

765
00:36:02,600 --> 00:36:06,120
Speaker 2: Sometimes you're poned and you can't create a circadian rhythm

766
00:36:06,120 --> 00:36:08,799
Speaker 2: because you just don't have the cues. Other times you

767
00:36:08,840 --> 00:36:13,080
Speaker 2: can find something that correlates with the light, or sometimes

768
00:36:13,120 --> 00:36:16,640
Speaker 2: instead of having a circadian rhythm, you have a circ

769
00:36:16,680 --> 00:36:19,480
Speaker 2: a title rhythm or something, and you're queuing in on

770
00:36:19,840 --> 00:36:22,960
Speaker 2: some other environmental thing that can help you maintain a

771
00:36:23,040 --> 00:36:23,960
Speaker 2: rhythm in your life.

772
00:36:24,040 --> 00:36:26,480
Speaker 1: Well, I thought that answer was super colent, fragilistic. But

773
00:36:26,600 --> 00:36:29,520
Speaker 1: let's hear what our listener says and see if there

774
00:36:29,520 --> 00:36:30,880
Speaker 1: are follow up questions.

775
00:36:31,520 --> 00:36:34,319
Speaker 5: Wow, thanks for answering my question. Never would have thought

776
00:36:34,360 --> 00:36:37,480
Speaker 5: that deep sea creatures could sense the tides all the

777
00:36:37,520 --> 00:36:39,080
Speaker 5: way down there. That's pretty cool.

778
00:36:59,080 --> 00:37:02,640
Speaker 2: We are backed Jupiter, a fascinating planet that could kill

779
00:37:02,760 --> 00:37:07,280
Speaker 2: us all. Arthur, what do you want to know about Jupiter?

780
00:37:08,360 --> 00:37:11,120
Speaker 6: Hi, Denim and Kelly. Nice to talk to you guys.

781
00:37:11,400 --> 00:37:13,920
Speaker 6: I have a rocket thrust issue.

782
00:37:14,360 --> 00:37:17,200
Speaker 3: I know that we can't escape the gravity of a

783
00:37:17,239 --> 00:37:21,400
Speaker 3: black hole no matter how powerful our rocket is, but

784
00:37:21,640 --> 00:37:24,360
Speaker 3: I don't know the largest mass of a planet we

785
00:37:24,440 --> 00:37:27,400
Speaker 3: can escape from with our current technology.

786
00:37:27,840 --> 00:37:29,200
Speaker 6: I mean, can an.

787
00:37:29,040 --> 00:37:32,879
Speaker 3: Average space rocket lift off from jupter, from the Sun,

788
00:37:33,280 --> 00:37:34,359
Speaker 3: from a neutron star?

789
00:37:34,960 --> 00:37:37,520
Speaker 6: I hope you have some funds are in this thanks.

790
00:37:37,840 --> 00:37:41,920
Speaker 1: See, Jupiter is just so attractive gravitationally, people can't stop

791
00:37:41,920 --> 00:37:42,760
Speaker 1: thinking about it.

792
00:37:42,760 --> 00:37:47,120
Speaker 2: It's beautiful also, all right.

793
00:37:47,200 --> 00:37:51,360
Speaker 1: So Arthur is wondering about taking off from planets because

794
00:37:51,440 --> 00:37:53,799
Speaker 1: the more massive the planet, the stronger the gravity, the

795
00:37:53,880 --> 00:37:56,600
Speaker 1: harder it is to lift off of. And he wants

796
00:37:56,640 --> 00:37:59,239
Speaker 1: to know if an average rocket could actually get you

797
00:37:59,480 --> 00:38:03,680
Speaker 1: off of Jupiter or even more exotic and denser locations.

798
00:38:03,920 --> 00:38:06,120
Speaker 2: So the first thing I want to know is I

799
00:38:06,120 --> 00:38:08,160
Speaker 2: can tell from the answer it's going to require math.

800
00:38:08,800 --> 00:38:11,360
Speaker 2: Did you do these calculations or is there a website

801
00:38:11,400 --> 00:38:12,360
Speaker 2: that has this information.

802
00:38:13,760 --> 00:38:15,719
Speaker 1: There are a lot of websites that have this information,

803
00:38:15,960 --> 00:38:18,720
Speaker 1: but I never trust them because you can find mistakes

804
00:38:18,719 --> 00:38:21,759
Speaker 1: on those websites, which is the source of a lot

805
00:38:21,760 --> 00:38:24,400
Speaker 1: of mistakes in like chat GBT, because it just like

806
00:38:24,440 --> 00:38:26,320
Speaker 1: strips some from the websites and gives you the answer,

807
00:38:26,640 --> 00:38:29,120
Speaker 1: sometimes in the wrong context or whatever. So I always

808
00:38:29,160 --> 00:38:32,200
Speaker 1: double check these myself. All right, wow, so what matters

809
00:38:32,239 --> 00:38:35,440
Speaker 1: for lifting off the surface? You're probably going to think

810
00:38:35,680 --> 00:38:38,480
Speaker 1: escape velocity. And first I want to say it's not

811
00:38:38,560 --> 00:38:40,400
Speaker 1: about escape velocity, but then it's going to turn out

812
00:38:40,440 --> 00:38:41,240
Speaker 1: to be about escape.

813
00:38:41,080 --> 00:38:43,759
Speaker 2: Velocity physicists, I know.

814
00:38:43,880 --> 00:38:47,000
Speaker 1: So escape velocity famously is the speed you have to

815
00:38:47,040 --> 00:38:50,279
Speaker 1: be going so you can escape the gravitational pull of

816
00:38:50,320 --> 00:38:52,799
Speaker 1: an object. Right, So for example, if I'm standing on

817
00:38:52,840 --> 00:38:54,640
Speaker 1: the surface of the Earth, how fast do I have

818
00:38:54,640 --> 00:38:56,680
Speaker 1: to throw a baseball straight up so that it just

819
00:38:56,760 --> 00:39:00,600
Speaker 1: keeps going forever? That it's kinetic energy over comes the

820
00:39:00,640 --> 00:39:03,839
Speaker 1: potential energy, Well, that has to climb out of right,

821
00:39:03,880 --> 00:39:07,040
Speaker 1: So as you move up away from the Earth, you're gaining.

822
00:39:07,040 --> 00:39:09,080
Speaker 1: Potential energy has to come from somewhere. It comes from

823
00:39:09,120 --> 00:39:12,439
Speaker 1: your kinetic energy. If you have enough kinetic energy, then

824
00:39:12,680 --> 00:39:16,200
Speaker 1: you can go forever. Essentially, if your kinetic energy overcomes

825
00:39:16,239 --> 00:39:18,560
Speaker 1: the potential, well you have to climb. So you have

826
00:39:18,600 --> 00:39:22,240
Speaker 1: to go fast to escape the Earth. But the reason

827
00:39:22,280 --> 00:39:24,160
Speaker 1: that's not what this is about is that that's not how

828
00:39:24,239 --> 00:39:27,799
Speaker 1: rockets work. Right, Rockets you don't slingshot them from the

829
00:39:27,840 --> 00:39:29,880
Speaker 1: Earth in one push. I mean, people are working on that,

830
00:39:29,920 --> 00:39:32,440
Speaker 1: and it's hilarious, but traditional rockets.

831
00:39:32,560 --> 00:39:34,600
Speaker 2: Wait, why is it hilarious and not inspirational?

832
00:39:36,480 --> 00:39:39,640
Speaker 1: It's just like the grown up version of a nine

833
00:39:39,680 --> 00:39:42,000
Speaker 1: year old boy's idea for how to get to space,

834
00:39:42,239 --> 00:39:45,320
Speaker 1: you know, like, let's pull back a really big rubber band,

835
00:39:45,640 --> 00:39:48,400
Speaker 1: you know. I mean, I knew they're working on sentrifusions

836
00:39:48,400 --> 00:39:50,840
Speaker 1: and it's pretty cool, but it seems like impractical to me.

837
00:39:50,880 --> 00:39:53,440
Speaker 1: Also because the g forces are insane, so I think

838
00:39:53,440 --> 00:39:56,440
Speaker 1: you could probably launch like stuff into space, but not people.

839
00:39:56,239 --> 00:39:59,120
Speaker 2: Anyway, that's my sense too. Yeah, you're launching stuff hard and.

840
00:39:59,040 --> 00:40:03,640
Speaker 1: Payloads anyway, That's not how traditional rockets work. If you notice,

841
00:40:03,680 --> 00:40:06,360
Speaker 1: when a rocket takes off, it's not going super duper fast.

842
00:40:06,520 --> 00:40:10,920
Speaker 1: It's very slowly climbing, right, And that's because rockets don't

843
00:40:10,960 --> 00:40:13,040
Speaker 1: have a single hard push at the beginning where they

844
00:40:13,040 --> 00:40:15,799
Speaker 1: gain a lot of speed and then gradually lose it

845
00:40:15,840 --> 00:40:18,279
Speaker 1: as they rise. They have a continual force. They have

846
00:40:18,360 --> 00:40:21,160
Speaker 1: an engine on them, so rockets only have to go

847
00:40:21,600 --> 00:40:25,040
Speaker 1: non zero velocity in order to move up. Right, as

848
00:40:25,080 --> 00:40:27,319
Speaker 1: long as the force from the rocket is greater than

849
00:40:27,320 --> 00:40:29,680
Speaker 1: the force of gravity from the Earth, it's going to

850
00:40:29,680 --> 00:40:32,200
Speaker 1: be moving up okay, right, So it can move up

851
00:40:32,239 --> 00:40:34,520
Speaker 1: super duper slowly. It could take like a year to

852
00:40:34,520 --> 00:40:37,000
Speaker 1: take off from the planet, doesn't matter. It's not about

853
00:40:37,080 --> 00:40:40,640
Speaker 1: escape velocity. It's about putting enough energy in to overcome

854
00:40:40,680 --> 00:40:42,799
Speaker 1: the potential energy to the Earth, but doesn't have to all

855
00:40:42,800 --> 00:40:45,680
Speaker 1: be upfront. So that's why it's sort of not about

856
00:40:45,760 --> 00:40:46,600
Speaker 1: escape velocity.

857
00:40:46,800 --> 00:40:49,960
Speaker 2: Okay. But so say you were lifting off at like

858
00:40:50,040 --> 00:40:54,600
Speaker 2: a foot per second, that would be much more energetically expensive,

859
00:40:54,600 --> 00:40:56,880
Speaker 2: wouldn't it, Because you're needing to like maintain the mass

860
00:40:56,920 --> 00:41:00,200
Speaker 2: you're trying to send up as you slowly go up,

861
00:41:00,200 --> 00:41:03,520
Speaker 2: And if you do it all faster, that's probably more efficient.

862
00:41:04,040 --> 00:41:05,880
Speaker 1: It's more efficient. Yeah, And if you do it all

863
00:41:05,880 --> 00:41:07,920
Speaker 1: at once, just by giving it one big push, then

864
00:41:07,960 --> 00:41:09,719
Speaker 1: you don't need to bring any propellant with you and

865
00:41:09,760 --> 00:41:13,600
Speaker 1: you can just accelerate the payload. Right Whereas if you're

866
00:41:13,760 --> 00:41:15,600
Speaker 1: climbing up at a foot per second, yeah, you've got

867
00:41:15,640 --> 00:41:18,160
Speaker 1: to bring the rest of the latter with you essentially,

868
00:41:18,560 --> 00:41:20,200
Speaker 1: and you've got to lift that fuel. So we're definitely

869
00:41:20,320 --> 00:41:20,560
Speaker 1: going to.

870
00:41:20,560 --> 00:41:21,280
Speaker 2: Get there, okay.

871
00:41:21,280 --> 00:41:22,920
Speaker 1: So what we do need to do is think about

872
00:41:23,200 --> 00:41:25,239
Speaker 1: how much fuel we have to bring and how we

873
00:41:25,280 --> 00:41:28,120
Speaker 1: can overcome this energy, and so you have to calculate

874
00:41:28,160 --> 00:41:30,719
Speaker 1: how much kinetic energy do you need to overcome the

875
00:41:30,760 --> 00:41:33,640
Speaker 1: potential energy the Earth. It's not important that it albeit

876
00:41:33,640 --> 00:41:37,040
Speaker 1: at once, and rockets do it gradually. But the way

877
00:41:37,080 --> 00:41:39,080
Speaker 1: to calculate that is to calculate what they call the

878
00:41:39,120 --> 00:41:43,360
Speaker 1: delta V, the change in velocity that a rocket can provide.

879
00:41:43,719 --> 00:41:45,960
Speaker 1: And in the end, this turns out to be very

880
00:41:46,040 --> 00:41:50,360
Speaker 1: similar to the escape velocity, and it makes sense that

881
00:41:50,400 --> 00:41:53,399
Speaker 1: it's similar because they're both connected to essentially how much

882
00:41:53,480 --> 00:41:56,160
Speaker 1: energy you need to climb out of this gravitational well

883
00:41:56,840 --> 00:41:59,400
Speaker 1: and so. On Earth, the escape velocity is about eight

884
00:41:59,520 --> 00:42:01,920
Speaker 1: kilometers per second. That's how fast you would have to

885
00:42:01,960 --> 00:42:04,480
Speaker 1: throw a baseball or launch a payload from the surface.

886
00:42:04,800 --> 00:42:07,040
Speaker 1: But it's also very closely connected. We'll use the rocket

887
00:42:07,080 --> 00:42:09,840
Speaker 1: equation in a minute to how much fuel you have

888
00:42:09,920 --> 00:42:11,560
Speaker 1: to bring with you, and that's going to turn out

889
00:42:11,560 --> 00:42:13,520
Speaker 1: to be the limiting factor of whether you can lift

890
00:42:13,520 --> 00:42:16,520
Speaker 1: off the planet is can you practically bring enough fuel

891
00:42:16,800 --> 00:42:20,480
Speaker 1: to get this much delta V? So on Earth you

892
00:42:20,520 --> 00:42:23,360
Speaker 1: need like eight kilometers per second, and then you go

893
00:42:23,400 --> 00:42:26,040
Speaker 1: to the rocket equation. The rocket equation says how much

894
00:42:26,120 --> 00:42:28,080
Speaker 1: mass do you need to bring so that you can

895
00:42:28,120 --> 00:42:30,719
Speaker 1: do this, so you can climb out of this gravitational well,

896
00:42:30,760 --> 00:42:34,080
Speaker 1: because remember a rocket, what is it doing. It's throwing

897
00:42:34,160 --> 00:42:36,880
Speaker 1: stuff out the back. Right. The way it works is

898
00:42:36,880 --> 00:42:40,279
Speaker 1: it's conserving momentum. Imagine you like in a rowboat and

899
00:42:40,320 --> 00:42:42,760
Speaker 1: you have a pile of bricks. You throw the bricks

900
00:42:42,800 --> 00:42:45,520
Speaker 1: out the back of the rowboat. The bricks go backwards,

901
00:42:45,560 --> 00:42:48,080
Speaker 1: you go forwards. That's how a rocket works. It's throwing

902
00:42:48,200 --> 00:42:50,000
Speaker 1: stuff out the back. So you have to have that

903
00:42:50,040 --> 00:42:52,920
Speaker 1: stuff in the rocket to throw out the back in

904
00:42:53,040 --> 00:42:55,640
Speaker 1: order to propel it. It's helpful if that stuff also

905
00:42:55,680 --> 00:42:58,160
Speaker 1: has the energy you can use to push the propellant.

906
00:42:58,280 --> 00:43:00,000
Speaker 1: It doesn't have to be you can have those things

907
00:43:00,200 --> 00:43:03,240
Speaker 1: be uncoupled. But in a chemical rocket you have fuel

908
00:43:03,280 --> 00:43:06,120
Speaker 1: which is both propellant and the source of energy, and

909
00:43:06,120 --> 00:43:09,120
Speaker 1: the rocket equation tells you what your mass ratio is.

910
00:43:09,160 --> 00:43:11,959
Speaker 1: So on Earth, for example, you need a delta vive

911
00:43:12,040 --> 00:43:15,319
Speaker 1: about ten kilometers per second. That tells you your mass

912
00:43:15,360 --> 00:43:17,879
Speaker 1: ratio is nine, which means you need a nine to

913
00:43:17,880 --> 00:43:20,320
Speaker 1: one fuel to payload mass ratio.

914
00:43:20,480 --> 00:43:21,200
Speaker 2: That's not great.

915
00:43:21,280 --> 00:43:23,600
Speaker 1: It's not great. Yeah, if you have like one hundred

916
00:43:23,680 --> 00:43:27,719
Speaker 1: kilogram person and a thousand kilogram spaceship around them. You

917
00:43:27,800 --> 00:43:30,719
Speaker 1: need nine times as much mass in fuel to get

918
00:43:30,719 --> 00:43:31,920
Speaker 1: that thing into orbit.

919
00:43:32,200 --> 00:43:34,759
Speaker 2: Wow. Yeah, how much worse is it for Jupiter? And

920
00:43:34,800 --> 00:43:36,000
Speaker 2: does it scale linearly?

921
00:43:36,480 --> 00:43:40,000
Speaker 1: It scales exponentially, which is the bad news. Right, And

922
00:43:40,080 --> 00:43:42,520
Speaker 1: so say you're on a super Earth which has the

923
00:43:42,520 --> 00:43:44,960
Speaker 1: mass of like five to ten times the Earth, then

924
00:43:45,000 --> 00:43:47,800
Speaker 1: the escape velocity is like twenty five to thirty kilometers

925
00:43:47,800 --> 00:43:50,200
Speaker 1: per second. Okay, that's not so bad. It's three to

926
00:43:50,239 --> 00:43:54,160
Speaker 1: four times as much, but the mass ratio is ninety three.

927
00:43:54,360 --> 00:43:57,520
Speaker 1: It's ten times as bad as it is here on Earth.

928
00:43:57,880 --> 00:44:00,919
Speaker 2: Ninety three to one, ninety three to one.

929
00:44:01,640 --> 00:44:04,360
Speaker 1: So instead of having a nine to one fuel to

930
00:44:04,440 --> 00:44:07,160
Speaker 1: payload ratio, you have a ninety three to one fuel

931
00:44:07,160 --> 00:44:10,200
Speaker 1: to payload ratio. So now like your rocket is basically

932
00:44:10,320 --> 00:44:12,719
Speaker 1: just fuel, right, and that's just for a super Earth.

933
00:44:13,160 --> 00:44:15,759
Speaker 1: Now go to Jupiter. Jupiter is so massive that it's

934
00:44:15,840 --> 00:44:19,160
Speaker 1: escape velocity is like forty kilometers per second, and this

935
00:44:19,200 --> 00:44:22,279
Speaker 1: gives a mass ratio of more than one thousand Wow. Right,

936
00:44:22,360 --> 00:44:25,200
Speaker 1: so you'd need a fuel tank that's a thousand times

937
00:44:25,280 --> 00:44:29,279
Speaker 1: bigger than your payload. This is probably even an underestimate,

938
00:44:29,320 --> 00:44:32,240
Speaker 1: but essentially this is impossible for chemistry, right, The chemical

939
00:44:32,320 --> 00:44:35,399
Speaker 1: rockets cannot achieve this. And if you went to the Sun, right,

940
00:44:35,680 --> 00:44:38,680
Speaker 1: then the escape velocity from the Sun is four hundred

941
00:44:38,800 --> 00:44:42,120
Speaker 1: kilometers per second, and so now the mass ratios are

942
00:44:42,160 --> 00:44:46,160
Speaker 1: just astronomical. From a neutron star, the escape velocity is

943
00:44:46,200 --> 00:44:50,160
Speaker 1: four tenths the speed of light. And so I couldn't

944
00:44:50,160 --> 00:44:51,960
Speaker 1: even get my calculator to give me a number on this.

945
00:44:52,000 --> 00:44:54,880
Speaker 1: W was just so big. And so the bottom line

946
00:44:54,960 --> 00:44:57,520
Speaker 1: is that chemical rockets, where you have this fuel and

947
00:44:57,560 --> 00:45:00,560
Speaker 1: you're slowly climbing out of the gravitational well, well they

948
00:45:00,600 --> 00:45:03,720
Speaker 1: work pretty well if the escape velocity is low. Because

949
00:45:03,719 --> 00:45:06,359
Speaker 1: the mass ratio is pretty small, you can afford nine

950
00:45:06,400 --> 00:45:09,000
Speaker 1: to one, which sounded bad already to you, right, But

951
00:45:09,400 --> 00:45:12,160
Speaker 1: on a bigger planet like a super Earth, it's pretty

952
00:45:12,160 --> 00:45:14,799
Speaker 1: hard to use. And a Jupiter or the Sun or

953
00:45:14,800 --> 00:45:17,080
Speaker 1: a neutron star, it's definitely not practical.

954
00:45:17,280 --> 00:45:21,560
Speaker 2: So what about like a project orion's style propulsion system?

955
00:45:21,640 --> 00:45:25,000
Speaker 2: So if you were exploding nuclear bombs out the back

956
00:45:25,080 --> 00:45:27,600
Speaker 2: of your rocket to send you up, could you get

957
00:45:27,640 --> 00:45:28,400
Speaker 2: off of Jupiter?

958
00:45:28,719 --> 00:45:31,799
Speaker 1: Yeah? You could. This is limited to chemical rockets, right,

959
00:45:32,160 --> 00:45:34,480
Speaker 1: and you can have other strategies you could build a

960
00:45:34,480 --> 00:45:38,920
Speaker 1: space elevator, right. You could have nuclear propulsion, absolutely, and

961
00:45:39,080 --> 00:45:42,760
Speaker 1: especially if you're launching the nuclear weapons behind the rocket

962
00:45:42,840 --> 00:45:44,680
Speaker 1: somehow so that they don't have to come along with

963
00:45:44,760 --> 00:45:47,439
Speaker 1: the rocket, then you can escape this trap of having

964
00:45:47,480 --> 00:45:49,840
Speaker 1: to bring all of your propellant with you. Yeah. Or

965
00:45:49,880 --> 00:45:51,800
Speaker 1: if you have like a light sale with a laser

966
00:45:51,840 --> 00:45:54,200
Speaker 1: behind it, you can use that to lift off of

967
00:45:54,239 --> 00:45:57,200
Speaker 1: a planet. Or you could just build your thing in space. Anyway,

968
00:45:57,880 --> 00:46:00,280
Speaker 1: while you're building it on the surface of Jupiter. Doesn't

969
00:46:00,280 --> 00:46:04,080
Speaker 1: really make sense unless that's where your super villain hideout is. Oh,

970
00:46:04,280 --> 00:46:06,759
Speaker 1: which case, I have to wonder Jupiter doesn't get a

971
00:46:06,760 --> 00:46:08,880
Speaker 1: whole lot of light. I wonder how your circadian rhythms

972
00:46:08,920 --> 00:46:11,319
Speaker 1: are going in your supervillain layer one.

973
00:46:11,360 --> 00:46:13,840
Speaker 2: You better hope that Bread isn't sending the Earth greening

974
00:46:13,880 --> 00:46:16,560
Speaker 2: into your your supervillain layer on Jupiter.

975
00:46:16,760 --> 00:46:19,719
Speaker 1: Oh, maybe he's saving us, right, maybe he's using the

976
00:46:19,800 --> 00:46:22,840
Speaker 1: Earth that doesn't really work, using the Earth to crush

977
00:46:22,880 --> 00:46:24,319
Speaker 1: somebody else's supervillain layer.

978
00:46:24,760 --> 00:46:25,359
Speaker 5: Yeah, not a.

979
00:46:25,280 --> 00:46:27,640
Speaker 2: Great plan, Brad, not paying you to write that plot, Daniel.

980
00:46:31,880 --> 00:46:35,640
Speaker 1: So yeah, chemical rockets work essentially only on smaller planets.

981
00:46:35,800 --> 00:46:38,440
Speaker 1: On bigger planets, you need other technologies, but those technologies

982
00:46:38,480 --> 00:46:41,040
Speaker 1: are not impossible. So I think if we did evolve

983
00:46:41,160 --> 00:46:43,920
Speaker 1: on Jupiter or on the surface of a neutron star,

984
00:46:44,520 --> 00:46:47,080
Speaker 1: technically it's still possible to get off of those, but

985
00:46:47,440 --> 00:46:48,600
Speaker 1: not with rockets.

986
00:46:48,760 --> 00:46:51,680
Speaker 2: All right, let's see if Arthur has any follow up questions,

987
00:46:51,800 --> 00:46:54,360
Speaker 2: and maybe he'll tell us what his supervillain plan is.

988
00:46:56,400 --> 00:46:59,360
Speaker 6: Thanks guys for the kind of answer my question. I

989
00:46:59,440 --> 00:47:02,560
Speaker 6: knew that enough from a bigger planet would be hard,

990
00:47:03,080 --> 00:47:06,000
Speaker 6: but I didn't knoww it would be almost impossible, at

991
00:47:06,080 --> 00:47:09,920
Speaker 6: least for chemical rockets, as you explained. I think that

992
00:47:10,239 --> 00:47:13,680
Speaker 6: this either puts a big as the risk on plans

993
00:47:13,680 --> 00:47:17,239
Speaker 6: for space exploration since the range of celestial bodies we

994
00:47:17,280 --> 00:47:22,200
Speaker 6: could visit would be very limited, or either forces research

995
00:47:22,320 --> 00:47:25,680
Speaker 6: for more efficient technologies. As you mentioned, all I have

996
00:47:25,719 --> 00:47:29,239
Speaker 6: to say about supervillains is that they love rockets these days,

997
00:47:29,480 --> 00:47:31,600
Speaker 6: so I do not doubt they have plans for this

998
00:47:31,960 --> 00:47:33,040
Speaker 6: massive loudness.

999
00:47:33,440 --> 00:47:35,879
Speaker 1: Thanks a lot, all right, thank you everybody for sending

1000
00:47:35,920 --> 00:47:37,920
Speaker 1: in your questions. Remember you can write to us two

1001
00:47:38,000 --> 00:47:40,480
Speaker 1: questions at Daniel and Kelly dot org and send us

1002
00:47:40,520 --> 00:47:43,399
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1003
00:47:43,440 --> 00:47:46,359
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1004
00:47:46,480 --> 00:47:47,520
Speaker 2: Can't wait to hear from you.

1005
00:47:47,560 --> 00:47:49,120
Speaker 1: Thanks, everybody, stay curious.

1006
00:47:56,080 --> 00:48:00,279
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1016
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