Speaker 1: If the Earth and Jupiter were to collide, what would happen?
Speaker 1: How would we die?
Speaker 2: Circadian rhythms are corrected using the Sun's light. If you
Speaker 2: live at the bottom of the sea, how do you
Speaker 2: get that right?
Speaker 1: How big a planet could we use rockets to escape?
Speaker 1: If we'd evolved on Jupiter, would we be planet down apes?
Speaker 2: Whatever questions keep you up at night, Daniel and Kelly's
Speaker 2: answers will make it right.
Speaker 1: Welcome to Daniel and Kelly's Extraordinary Universe.
Speaker 2: With an emphasis on Jupiter, it seems. Hello, I'm Kelly Wiersmith,
Speaker 2: and I study parasites and space, and clearly Jupiter is
Speaker 2: the best planet.
Speaker 1: Hi, I'm Daniel. I'm a particle physicist, and yes, Jupiter
Speaker 1: has the most particles of any planet.
Speaker 2: And does that make it the best As a particle physicist.
Speaker 1: It makes it the mostiest? I guess you know. I
Speaker 1: think people underestimate, like how much of the Solar System
Speaker 1: is just the Sun in Jupiter? Like mostly it's just
Speaker 1: the Sun, and then you want to add Jupiter, all right,
Speaker 1: to round it up to nine to nine point nine,
Speaker 1: and everything else is just details. We're really just here
Speaker 1: in somebody else's party.
Speaker 2: Oh, man, that's a little it's a kind of a
Speaker 2: bummer of a way to start our episode.
Speaker 1: We are all insignificant, No, I think it tells you
Speaker 1: something though, when you look at the depiction of the
Speaker 1: Solar System and all the planets are like big, and
Speaker 1: obviously it's not the scale, but it tells you something
Speaker 1: about what we find important. Right, Clearly, we are important
Speaker 1: in the Solar System. So we zoom up. It's like
Speaker 1: that cover of the New Yorker where they show like
Speaker 1: a map of the United States from the New York
Speaker 1: City perspective, and it's like mostly Manhattan and then like
Speaker 1: a few details and that's ridiculous and you laugh at it,
Speaker 1: But that's exactly what we're doing about the planets, right.
Speaker 3: Well.
Speaker 2: But you know, on the one hand, we've known about
Speaker 2: Jupiter for much less long than we've known about Earth,
Speaker 2: and you know, we're here on Earth, makes it easier
Speaker 2: to study. I'm going to go ahead and stand down
Speaker 2: on defensive Earth and the Earth centered view of the world.
Speaker 1: I'm the saying it's wrong. I'm just saying it reveals
Speaker 1: something about our biases, right, the things we think should
Speaker 1: be presented first.
Speaker 2: I grant you that, but there's probably, you know, solar
Speaker 2: systems that are bigger than ours, and maybe we shouldn't
Speaker 2: even be talking about our solar system at all. And
Speaker 2: where do you stop, Daniel, Where does it end?
Speaker 1: It never ends, Kelly, There's no bottom to the philosophical
Speaker 1: rabbit hole.
Speaker 2: Oh my goodness.
Speaker 1: But we love going down rabbit holes, especially rabbit holes
Speaker 1: that you are interested in. So if you have a
Speaker 1: question about the nature of the universe, or how something works,
Speaker 1: or how little squishy critters make their lives, please write
Speaker 1: to us with your question. We would love to answer
Speaker 1: it here on the pod. And today we're answering three
Speaker 1: super fun questions from listeners.
Speaker 2: That's right, so let's start with our first question from.
Speaker 1: Brad, A great question about Jupiter, of course.
Speaker 4: Hello, Daniel and Kelly. I have a question about planetary collisions.
Speaker 4: Jupiter is classified as a gas giant planet and is
Speaker 4: known to sweep up many stray masses flowing through our
Speaker 4: Solar system. If something were to happen to cause Earth
Speaker 4: and Jupiter to collide, what would happen at impact? Is
Speaker 4: the mass of Jupiter large enough to spaghettify Earth and
Speaker 4: destroy us like a black hole? Or is the likelihood
Speaker 4: of a direct collision too small, and Earth would just
Speaker 4: be ejected from the Solar System if we become too close.
Speaker 4: Or is the surfaces of Jupiter really a gas and
Speaker 4: Earth would just pass into the inside of Jupiter and
Speaker 4: basically be absorbed, and Earth would just coast through a
Speaker 4: dense atmosphere of gases and would eventually hit a solid core.
Speaker 4: Thanks Brad from League City, Texas.
Speaker 1: So, Kelly, do you think Brad is a supervillain planning
Speaker 1: to push Earth into Jupiter or threatened to?
Speaker 2: You know, I did wonder about that when I was
Speaker 2: listening to this question. I'm a little concerned, and you
Speaker 2: know what, a little concerned in general now that this
Speaker 2: is something you know on my radar to worry about.
Speaker 2: And then too, I'm a little worried about Brad in particular.
Speaker 1: A couple of red flags here. Yeah, I'm not sure
Speaker 1: in his question if he's worried about this or excited
Speaker 1: about it, He's like, let's do the experiment.
Speaker 2: Yeah, yeah, hard to say, hard to say. Maybe we
Speaker 2: shouldn't give him the answer m exact.
Speaker 1: I worry about that. Like when the kid wrote to
Speaker 1: me and asked me what it would take to blow
Speaker 1: up Mars. I was like, hmm, should I really be
Speaker 1: telling a ten year old how to destroy a planet?
Speaker 2: Well, but on the other hand, you know, you hope
Speaker 2: they don't wield that sort of power, didn't do anything
Speaker 2: about the information.
Speaker 1: Who knows what today's ten year olds will do in
Speaker 1: twenty or thirty years.
Speaker 2: Right, that's true, that's true, and you'll beat a blame, Daniel,
Speaker 2: accept that blame.
Speaker 1: But today we're here to answer Brad's question as a
Speaker 1: hypothetical science question about something we hope will never happen,
Speaker 1: which does reveal a lot of really interesting solar system physics.
Speaker 1: So let's get into it.
Speaker 2: And I think we should probably start with what is
Speaker 2: spaghetification because that is clearly one of the best scientific
Speaker 2: terms our community has ever come up with.
Speaker 1: Absolutely. Spaghetification is usually used to describe what happens to
Speaker 1: an object as it approaches a black hole, in that
Speaker 1: you won't just fall in, you'll be torn apart into
Speaker 1: spaghetti essentially before you actually fall into the black hole.
Speaker 1: And this doesn't just happen around black holes. It happens
Speaker 1: all the time in strong gravitational environments. In fact, it's
Speaker 1: happening to you, right now, and it's happening to the moon.
Speaker 1: It's the result of tidal forces. And the reason simply
Speaker 1: is that the force of gravity depends on distance. So
Speaker 1: if you're falling into a black hole or you're orbiting
Speaker 1: a planet or whatever, and your feet are closer than
Speaker 1: your head than your feet have a stronger gravitational force
Speaker 1: on them than your head does, and effectively, that's a
Speaker 1: force pulling your feet away from your head. And if
Speaker 1: that force is strong enough, it will pull your head
Speaker 1: off your body or your feet off of your head,
Speaker 1: depending on your perspective.
Speaker 2: I'm going to be honest here, I feel like you've
Speaker 2: sort of de excitified spaghetti cation for me by being like,
Speaker 2: it's just a kind of title force. It's like, what's happening.
Speaker 5: To the moon.
Speaker 2: And I'm like, oh, but I'm spaghetific. That's not what
Speaker 2: I imagined in my head.
Speaker 1: Uh, you're imagining some sort of black hole magic.
Speaker 2: Yes, yes, I thought this was a specific black holy
Speaker 2: thing and that spighetification really, you know, required you to
Speaker 2: be thin like a noodle.
Speaker 1: But okay, physics has been ruining things since fifteen eighty
Speaker 1: four or whatever.
Speaker 2: Oh, and what happened in particular in fifteen eighty four.
Speaker 2: Daniel I just.
Speaker 1: Made it that date. I was referencing one of Zach's comics.
Speaker 2: I can't remember what year he had on this or
Speaker 2: why he picked it.
Speaker 1: I think it was supposed to be like Galleo's experiments
Speaker 1: or Bacon or somebody like that. Anyway, the point is
Speaker 1: that tidal forces are a thing. So if you approach Jupiter,
Speaker 1: for example, then the difference in forces between one side
Speaker 1: of your object and the other side of your object,
Speaker 1: those are the tidal forces. And that's why we have
Speaker 1: tides on the Earth, because the Moon pulls on one
Speaker 1: side of the Earth more strongly than on the other
Speaker 1: side of the Earth, making it a little bit of
Speaker 1: a football, and the Earth it's the same thing to
Speaker 1: the Moon, and that's why the Moon is locked in place.
Speaker 1: It's called tidally locked because there's a little bit of
Speaker 1: a football and it's hard for it to spin away
Speaker 1: from having the point a bit of its football aligned
Speaker 1: with the point a bit of the Earth's football.
Speaker 2: Okay, but so Jupiter is much bigger than the Moon,
Speaker 2: so is you know you said that when the force
Speaker 2: gets hard it could like pop a head off. Is
Speaker 2: Earth's metaphorical head gonna pop off towards Jupiter or is
Speaker 2: it just gonna get like weird tides.
Speaker 1: Yes, So there's a boundary called the Roche limit. If
Speaker 1: you get closer than that, you get torn into pieces.
Speaker 1: If you're further away from that, you don't. And that's
Speaker 1: why some planets have rings and some planets have moons.
Speaker 1: If your moon is further away than the Roche limit,
Speaker 1: it stays together. Local gravity winds over the tidal forces.
Speaker 1: If you get too close, then it gets torn apart
Speaker 1: into a ring because the tidal forces overcome the internal gravity.
Speaker 1: So that's the Roche limit. So what happens as the
Speaker 1: Earth approaches Jupiter, Well, the roach limit for a solid
Speaker 1: body like the Earth is actually inside the cloud tops
Speaker 1: of Jupiter. Jupiter is a gas giant, and the outer
Speaker 1: layer is like fifty kilometers of just clouds blow which
Speaker 1: you have like gaseous hydrogen, and then liquid hydrogen, and
Speaker 1: then this crazy helium neon rain, and then ocean of
Speaker 1: metallic hydrogen before you get to the icy, rocky core.
Speaker 1: So the Earth would sink into the clouds without getting
Speaker 1: torn apart. It would get torn apart after it already
Speaker 1: passes into the clouds.
Speaker 2: Okay, So at that point we are closer to Jupiter
Speaker 2: than Jupiter's rings. Right, So Earth's not going to become
Speaker 2: like a ring of Jupiter. It's going to get torn
Speaker 2: apart and then rain down on Jupiter. Is Jupiter the
Speaker 2: planet that has the diamond rain?
Speaker 1: I think that's Saturn. Ah, it is so disappointing thing. Yesh, Jupiter, yawn.
Speaker 2: Come on, Jupiter, step up your game man.
Speaker 1: All right. So now we have a collision of an
Speaker 1: entire Earth, right, it's whole. It has not been pulled
Speaker 1: apart by the tidal forces of Jupiter, and it hits Jupiter,
Speaker 1: and Brad asks like, what's going to happen? And is
Speaker 1: it going to pass in and be absorbed to hit
Speaker 1: the solid core? And you're definitely not going to make
Speaker 1: it all the way to the solid core because even
Speaker 1: though Jupiter is a gas giant, it has like layers
Speaker 1: and layers of hydrogen. That hydrogen is dense, and atmospheres
Speaker 1: have friction. Even here on Earth, where atmosphere is pretty
Speaker 1: low density compared to the Jovian atmosphere, you know, there's
Speaker 1: re entry. If a rocket or an asteroid tries to
Speaker 1: enter the Earth's atmosphere. There's a lot of friction from
Speaker 1: the atmosphere and you get all this heat, and most
Speaker 1: things that hit the Earth's atmosphere don't make it to
Speaker 1: the surface. Same principle applies when the Earth hits the
Speaker 1: Jovian atmosphere. Okay, and so what's going to happen is
Speaker 1: you're going to compress the Jovian atmosphere, which is going
Speaker 1: to heat it up, turn it into plasma, and that's
Speaker 1: going to vaporize the crust and the mantle of the Earth. Yeah. Bad,
Speaker 1: And so essentially a massive energy release. Here did a
Speaker 1: little bit of the back of the envelope calculation, and
Speaker 1: assuming that the Earth hits at like sixty kilometers per second,
Speaker 1: which is, you know, fast but not super fast for
Speaker 1: Solar system speeds, you're gonna release ten to the eighteen
Speaker 1: megatons of TNT. Wow. And you might be like, I
Speaker 1: don't know what that number means. Well, the Hiroshima explosion
Speaker 1: was fifteen kilotons. This is ten to the eighteen mega tons.
Speaker 1: So it's like so much bigger. And you know, I
Speaker 1: mean the entire Earth is essentially a bomb, and a
Speaker 1: lot of that mass is converted into energy. So it's
Speaker 1: an enormous explosion. You're gonna get like a fireball rising
Speaker 1: above the surface of Jupiter. It's gonna be much bigger
Speaker 1: than the volume of the Earth. And you're gonna have
Speaker 1: shock waves in the Jovian atmosphere which probably will last
Speaker 1: for years. You may even leave a spot on Jupiter.
Speaker 1: It's very unlikely you're gonna make it all the way
Speaker 1: to the core because you've got lots of dense layers
Speaker 1: before you get there. But yeah, it's gonna be a
Speaker 1: huge impact. But remember Jupiter is huge compared to the Earth, Like,
Speaker 1: it's so much bigger than the Earth that even though
Speaker 1: this is an enormous amount of energy and would devastate
Speaker 1: the Earth vaporized essentially, Jupiter is gonna mostly shrug it off.
Speaker 2: Oh man, that's a little insulting. Every human I've ever
Speaker 2: known or loved disappears and Jupiter's like, eh, okay. Well,
Speaker 2: so say at this point, when this happens, we have
Speaker 2: a self sustaining settlement on Mars. If the Martians were
Speaker 2: like in the right position, could they see this or
Speaker 2: would the act of Jupiter moving towards Earth have destroyed
Speaker 2: Mars on the way or thrown Mars off orbit. This
Speaker 2: is probably unfair. It's a totally different question. But am
Speaker 2: I asking you anyway? Daniel?
Speaker 1: Oh? I see well, I was imagining that the Earth
Speaker 1: is getting tossed into Jupiter. Read when Jupiter is like
Speaker 1: bullying its way into the inner Solar system. Oh okay,
Speaker 1: so the Martians have a nice view of Earth shooting
Speaker 1: by and then they yeah, they could watch Jupiter as
Speaker 1: it gets impacted. In fact, we had ringside seats to
Speaker 1: a similar event in the nineties.
Speaker 2: And I think you told me that you were at
Speaker 2: a telescope watching that, right, Yeah, I.
Speaker 1: Had a super fast camera hooked up to a telescope
Speaker 1: to watch this collision. This is in the mid nineties
Speaker 1: comet Shoemaker Levee impacted Jupiter and created all these fireballs.
Speaker 1: Now the comet not nearly the size of the Earth,
Speaker 1: of course, but still very very dramatic. And what happened
Speaker 1: is that this comet, which used to be orbiting the Sun,
Speaker 1: got captured by Jupiter. So now it was orbiting Jupiter
Speaker 1: sometime in the sixties and in the early nineties it
Speaker 1: passed very close to Jupiter, so Jupiter tore it apart.
Speaker 1: It went within the roch limit, not actually within the clouds.
Speaker 1: The roach limit weirdly and confusingly depends on the object,
Speaker 1: Like if you're made out of diamond, then your rochal
Speaker 1: limit is much closer. You have to get much closer
Speaker 1: to get torn apart than if you're made out of
Speaker 1: like cotton candy. Right, And so this comic got torn
Speaker 1: apart into twenty one pieces, which they labeled ABCD all
Speaker 1: the way up to w NASA.
Speaker 2: Very creative, of course they did. That was an opportunity
Speaker 2: for creativity. So they had to pass it by and.
Speaker 1: Then it's swung around one more time, and over six
Speaker 1: days in nineteen ninety four, each piece took turns smacking
Speaker 1: into Jupiter. Wo really amazing, and everyone on Earth was
Speaker 1: like turning their telescopes to it and watching these pieces hit.
Speaker 1: And the biggest spot is the one where the g
Speaker 1: fragment hit, and so you can imagine what that spot
Speaker 1: might be called.
Speaker 2: I was just thinking that, but this is a children's show.
Speaker 1: Exactly, and created a huge dark spot. There was a
Speaker 1: fireball and a dark spot the width of the Earth.
Speaker 2: Wow.
Speaker 1: Right now, this fragment is a piece of a comet,
Speaker 1: which is tiny compared to the Earth, but it created
Speaker 1: a big spot the size of the Earth that was
Speaker 1: visible for a year. So we've seen this kind of
Speaker 1: impact much smaller, So essentially you just scale this up
Speaker 1: much more dramatically, but still small compared to Jupiter.
Speaker 2: Amazing. I wish I had watched them. That wasn't on
Speaker 2: my radar because I didn't have amazing friends like you
Speaker 2: back then. You wouldn't have let me go astray. But
Speaker 2: that's all right.
Speaker 1: I was in college at the time, and I was
Speaker 1: home over the summer doing a research project on plasma physics,
Speaker 1: and we had a super fast camera that we were
Speaker 1: using to image what happened when you drop a little
Speaker 1: pellet of fuel into the fusion plasma. And the guy
Speaker 1: I worked for also had a telescope and he was like,
Speaker 1: let's point this thing at Jupiter. So he connected the
Speaker 1: camera to the telescope, pointed to Jupiter, and we had
Speaker 1: one of the fastest digital cameras around at the time
Speaker 1: for scientific applications, so we were hoping to have like
Speaker 1: the highest time resolution photographs of this impact. But just
Speaker 1: as the impact was going to happen, it went over
Speaker 1: the horizon, so we got pictures of the fireball rising
Speaker 1: over Jupiter, but not the impact itself. But it was
Speaker 1: a lot of fun anyway.
Speaker 2: So wait, this was ninety four though, is that right?
Speaker 1: Yeah?
Speaker 2: Okay, so I was twelve, so I probably I was
Speaker 2: listening to Silverchair and I didn't care about anything other
Speaker 2: than Silverchair.
Speaker 1: So important stuff, important.
Speaker 2: Stuff, ohs that way, at the time, the rest of us.
Speaker 1: Were learning about the future impact of Earth on Jupiter.
Speaker 2: But you know whatever, Well, I was having a good time,
Speaker 2: so I wouldn't change it for anything, all right. Brad
Speaker 2: asked if there was any chance we'd get ejected from
Speaker 2: the Solar system, But you didn't mention that as a
Speaker 2: as an option, so that's not something that would happen.
Speaker 1: It could happen, It depends on how accurately Brad and
Speaker 1: his supervillain team aim the Earth at Jupiter. One possibility
Speaker 1: is it hits Jupiter right. Another possibility is that it's
Speaker 1: captured and orbit Jupiter. And this has happened to a
Speaker 1: bunch of stuff. We think that many of the moons
Speaker 1: of Jupiter didn't form with Jupiter but were captured by
Speaker 1: it later. But it's a little bit unlikely because for
Speaker 1: that to happen, you have to be only at the
Speaker 1: right angle and the right velocity at the right location
Speaker 1: to get the orbital mechanics to work out. So more
Speaker 1: likely you're either going to hit Jupiter or you're going
Speaker 1: to get ejected from the Solar System because you're going
Speaker 1: to have a gravitational interaction with Jupiter, which is then
Speaker 1: going to throw you out of the Solar System.
Speaker 2: All right, well, one way or another. I think someone
Speaker 2: should be keeping a close eye on Brad and let's
Speaker 2: see if our answer changes Brad's mind about whether or
Speaker 2: not this is a good idea.
Speaker 4: Daniel and Kelly, I absolutely love this response. I assure
Speaker 4: you that I am not a supervillain and have no
Speaker 4: plans to destroy the planet. It sounds like we would
Speaker 4: get to watch as we pass into the gas cloud
Speaker 4: layer before we heat up and explode. I like to
Speaker 4: know that we would at least have a little impact
Speaker 4: on Jupiter. I think all we need to know now
Speaker 4: is where Michael Bay wants to set up the camera
Speaker 4: to catch it's the greatest collision of all the time.
Speaker 4: Thanks for all y'all do.
Speaker 1: All right, we're back and we're answering questions from listeners.
Speaker 1: Now we're going to take a break from Jupiter themed
Speaker 1: questions and think about sleeping. Here's a wonderful question from
Speaker 1: one of our Discord listeners. And if you're not on Discord, Colm,
Speaker 1: join us on our Discord channel. We have lots of
Speaker 1: fun conversations about science. We answer questions on there, other
Speaker 1: people answer questions on there. We have wonderful moderators to
Speaker 1: keep it a really happy fun family. Colm, join us
Speaker 1: for science chats on Discord. You can find a link
Speaker 1: on our website. Anyway, here's the question from our listener.
Speaker 5: In the episode about sleeping dreams, the topic of circadian
Speaker 5: rhythms in various animals came up. I was curious how
Speaker 5: circadian rhythms work in animals that never see the sun,
Speaker 5: like cave dwellers or various deep sea creatures. Thanks for
Speaker 5: taking the question, looking forward to the answer.
Speaker 2: Bye, all right, t to the j on Discord. I
Speaker 2: gotta say, you know, this question came in and I thought,
Speaker 2: all right, circadian rhythms. I'm a biologist. I should be
Speaker 2: able to knock this answer out pretty quick. I don't
Speaker 2: know anything about circadian rhythms. It turns out, oh no.
Speaker 1: This was biology is a big field.
Speaker 2: That's what I'm saying, but I really enjoyed the opportunity
Speaker 2: to get to dig into circadian rhythms again. This is
Speaker 2: one of the things I love about the questions we
Speaker 2: get from listeners. There's so many things I thought I
Speaker 2: understood and then they give me a chance to dig
Speaker 2: into them, and I learned so much. So uh, circadian rhythms.
Speaker 2: Circadian comes from the words circa diaz, which means approximately
Speaker 2: a day. And I'm you know, I don't know, maybe
Speaker 2: that's Latin. I probably pronounced it wrong, but you all
Speaker 2: know what I'm saying. So it's all right. We're good
Speaker 2: and nobody expects me to pronounce things right at this point.
Speaker 1: That's not what they're here for, Kelly, is not.
Speaker 2: What you're here for. So circadian rhythms are like internal
Speaker 2: rhythms that happen on an approximately twenty four hour cycle,
Speaker 2: and they're entrained or they're sort of like synced up
Speaker 2: based on outside signals like light.
Speaker 1: But why do you say approximate? I mean, the earth
Speaker 1: cycle is pretty crisp. Wouldn't we do best being closely
Speaker 1: linked to it? Why are you saying approximate?
Speaker 2: Because you know it's just not perfect and some people
Speaker 2: have cycles that are a little bit longer than twenty four.
Speaker 2: Some people have cycles that are a little bit shorter
Speaker 2: than twenty four. We think this contributes to why some
Speaker 2: people are mourning people and some people are night people.
Speaker 2: And then if you're talking about organisms other than humans,
Speaker 2: you can get some other slightly different sorts of signals
Speaker 2: that are approximately twenty four hours.
Speaker 1: So then what parts of the human body are affected
Speaker 1: by it? Obviously you sleep in this sort of twenty
Speaker 1: four hour cycle. Is there other stuff going on also?
Speaker 2: Yeah, lots of things. So like sleep is important, metabolism
Speaker 2: is also important. Like your body temperature is impacted by
Speaker 2: circadian rhythms.
Speaker 1: Right, metabolism, So that is that why I shouldn't eat
Speaker 1: chips at ten pm?
Speaker 2: That could partly be it or be involved. I think
Speaker 2: cortisol is to some extent involved in helping with digestion
Speaker 2: and stuff, and so your cortisol kind of peaks at
Speaker 2: times of day when you're like expected to be hungry
Speaker 2: and expected to be eating.
Speaker 1: What's cortisol?
Speaker 2: Cortisol is a hormone that folks usually associate with recovery
Speaker 2: from stress. So when you get stressed out by something,
Speaker 2: your body releases cortisol, and then cortisol helps your body
Speaker 2: sort of return to homeostasis or like a normal state
Speaker 2: after you've been stressed out.
Speaker 1: Cortisol sounds great, as you can say more of that.
Speaker 2: Well, if you are, like, you know, running away from
Speaker 2: a lion, cortisol is great, like it releases a bunch
Speaker 2: of energy all at once that you can outrun the lion,
Speaker 2: and then when you're in a safe spot, it helps
Speaker 2: you sort of return to normal. But if your cortisol
Speaker 2: level is elevated for a very long time, you can
Speaker 2: start having diseases because you're constantly in a stressed out state.
Speaker 2: So cortisol is more supposed to like get you out
Speaker 2: of an intent hence acute situation, but if it's elevated chronically,
Speaker 2: it can be bad. And there's a really interesting book
Speaker 2: on this called Why Zebras Don't Get Ulcers by Robert Sippolski. Cool.
Speaker 1: All right, yeah, well, I wonder if zebra's go to
Speaker 1: my physics faculty meetings if they feel stressed out and
Speaker 1: need cortisol afterwards.
Speaker 2: Oh yeah, faculty meetings. I think what I'm stressed out
Speaker 2: about in faculty meetings is that I could be spending
Speaker 2: my time way better doing anything else. But you know,
Speaker 2: I haven't had to go to faculty meetings for a while,
Speaker 2: so that's great.
Speaker 1: Dark wasn't Today is not about silly arguments and physics
Speaker 1: faculty meetings. It's about the rhythms of the body. So
Speaker 1: you're telling us that these things happen and impact sleep, metabolism,
Speaker 1: and temperature. But what's the mechanism for it? Like, what
Speaker 1: is driving it?
Speaker 4: Yeah?
Speaker 2: Okay, So most of the work that we've done to
Speaker 2: figure out the mechanism has been done in organisms like
Speaker 2: mice and fruitflies. But here's how we think that it works.
Speaker 2: How we're guessing that it works in humans based on
Speaker 2: what we've seen in lab animals. So there's a little
Speaker 2: part of your brain called the hypothalamus, and inside of
Speaker 2: the hypothalamis there's a little region called the super chiasmatic
Speaker 2: nucleus or the SCN. Because I'm not going to try
Speaker 2: say that a bunch.
Speaker 1: Of times it sounds a lot like super cool, fudulistic,
Speaker 1: expire audotious, but all right, yeah, I hear that every
Speaker 1: time you say that.
Speaker 2: Now, okay, no one's going to be able to pay
Speaker 2: attention to the rest of the episode. They're going to
Speaker 2: be singing just like Mary Poppins, but try to focus people,
Speaker 2: all right. So you've got the SCN, and the SCN
Speaker 2: is connected to the optic nerves, and so optic nerves
Speaker 2: these are the nerves that go to your eyes. And
Speaker 2: so we've talked in the past about how your eyes
Speaker 2: have specialized cells called rods and cones, and those help
Speaker 2: you detect like patterns and colors and to see your world.
Speaker 2: But you also have cells that just detect the intensity
Speaker 2: of light, and those cells send information through your optic
Speaker 2: nerve back to the SCN, and your brain uses that
Speaker 2: information to tell the rest of your body how the
Speaker 2: rhythm should be working. And so it does this by
Speaker 2: either sending messages through the nerves or by directing the
Speaker 2: production of hormones that will then go to the rest
Speaker 2: of your body and talk to your cells and basically say, Okay,
Speaker 2: hey guys, it's morning. And when it's mourning, your body increases,
Speaker 2: its heart rate, increases, its blood pressure, increases temperature. Your
Speaker 2: body is not making melatonin at this point. Melatonin is
Speaker 2: associated with sleep. So this is generally how your body
Speaker 2: collects the information about what should be setting the timing
Speaker 2: for the rhythm. But each one of your cells also
Speaker 2: has its own circadian clock.
Speaker 1: So we have these special cells in our eyes. Instead
Speaker 1: of just using the information which already exists in the
Speaker 1: rods and cones, we like evolve the separate pathway just
Speaker 1: for this. Wow, this is pretty weird engineering.
Speaker 2: Well, but it's detecting something different. Your rods and your
Speaker 2: cones are detecting like colors and you know, patterns of
Speaker 2: like dark against light and stuff like that. These cells
Speaker 2: are just detecting the intensity of the light that's coming in.
Speaker 2: So you're like, oh it's dawn now, or oh it's noon,
Speaker 2: and so it's detecting that.
Speaker 1: I feel like I could write a computer program to
Speaker 1: extract the same information from the data produced by the
Speaker 1: codes and the rods. But that's fine. Obviously the brain
Speaker 1: is not engineered by physicists.
Speaker 2: And that's not how evolution works. Evolution doesn't say, Okay,
Speaker 2: I'm going to start from scratch and come up with
Speaker 2: the best system. It's like, well, what do I have
Speaker 2: and how can I work with it?
Speaker 1: I just think it's a fascinating clue that something happened
Speaker 1: there that this is what we ended up with. You know,
Speaker 1: It's just another example of how like obviously this is
Speaker 1: not well organized. Just what kind of worked? And so
Speaker 1: do we know this because we've like done studies in
Speaker 1: mice where we've like tweaked those cells or got rid
Speaker 1: of those cells, or like shined light on those cells
Speaker 1: or something, and it's changed the way the mice behave.
Speaker 2: Yeah, so if you mess up a mouse or a
Speaker 2: flies SCN, then they'll start free cycling. So essentially they
Speaker 2: won't show these twenty four hour cycles.
Speaker 1: They're not so xpl a doocious anymore.
Speaker 2: That's right, that's right. It's truly quite atrocious.
Speaker 1: All right, So that's wrong. Okay, that was pretty good.
Speaker 1: That was really good.
Speaker 2: Grudgingly patting me on the back there.
Speaker 1: I was so excited about my next question. I didn't
Speaker 1: registering a joke, but that was excellent. Yeah, ten points
Speaker 1: for Kelly for everybody's keeping score. So you're telling us
Speaker 1: that not only these light signals tell us when to
Speaker 1: be fragilistic, but also the rest of our body responds
Speaker 1: in some way.
Speaker 2: Yeah. Okay, So first I just want to mention real
Speaker 2: quick that that organisms from bacteria to humans show these clocks,
Speaker 2: and so this is like not every organism uses their
Speaker 2: SCN and so this sort of like feeds back on
Speaker 2: our conversation about how you just use what you have.
Speaker 2: This has been going on for a really long time anyway.
Speaker 2: So not every single cell has its own circadian clock.
Speaker 2: I misspoke earlier, but many cells, even if you take
Speaker 2: them out of the body and you put them in
Speaker 2: like a petri dish, they will show like a twenty
Speaker 2: four hour schedule for the activities that they do, like
Speaker 2: they've repair DNA at a certain time, you know, stuff
Speaker 2: like that. And so here's how we think that works.
Speaker 2: So your cell is making a a protein called clock protein.
Speaker 2: The clock protein at dawn moves into your nucleus where
Speaker 2: the genetic information is stored, and it binds to literally
Speaker 2: thousands of different sites on your DNA. And when it binds,
Speaker 2: it's telling your DNA to start making certain things. And
Speaker 2: it could be making certain hormones, like it can say, hey,
Speaker 2: start making that cortisol. It could start doing you know,
Speaker 2: whatever is needed to increase body temperature or heart rate,
Speaker 2: et cetera. So thousands of things are turned on when
Speaker 2: your clock proteins go in there and bind to lots
Speaker 2: of different spots. Another thing that's being made. Though, during
Speaker 2: the course of the day are proteins that will shut
Speaker 2: this down. And these proteins are called period proteins, And
Speaker 2: so the period proteins will build up over the course
Speaker 2: of the day because the clock proteins said, hey, start
Speaker 2: making these, and at some point they've built up to
Speaker 2: high enough levels that now they go into the nucleus
Speaker 2: and they pull the clock proteins off of the DNA
Speaker 2: and that stops all of the stuff that the clock
Speaker 2: proteins had been turning on and getting made. As the
Speaker 2: night goes on, the period proteins break down and go away,
Speaker 2: and then the next morning the clock proteins go back
Speaker 2: in and the cycle starts again.
Speaker 1: So, like many clocks, you have some sort of process
Speaker 1: which has a natural timescale built into it, right, and
Speaker 1: so there is chemistry where things are slashing back and
Speaker 1: forth and naturally at the same rate as our twenty
Speaker 1: four hour cycle. Is that what's happening?
Speaker 2: Yeah, yeah, that's a good summary. And I saw you.
Speaker 2: Yeah cool looking something up? Was I wrong about something
Speaker 2: or was it unrelated?
Speaker 1: I was wondering if clock was an acronym for something
Speaker 1: in a really tortured way.
Speaker 2: But oh, okay, right, I.
Speaker 1: Was hoping it stood for something ridiculous. Okay, because if
Speaker 1: it was a physics acronym, it definitely would have a
Speaker 1: ridiculous name.
Speaker 2: Got it anyway, So light is important for determining these cycles, right,
Speaker 2: But it also is fine tuned by things like the
Speaker 2: temperature you find yourself at when during the day you're eating,
Speaker 2: and these cues are important for other animals as well.
Speaker 2: So it's not just light, but light does seem to
Speaker 2: be a super important factor.
Speaker 1: So it's interesting you have several different kinds of things
Speaker 1: going on. Can they get out of sync or is
Speaker 1: there something that tries to keep them in harmony.
Speaker 2: Well, so, once you develop a cycle, your body is
Speaker 2: pretty good at keeping that cycle going. So like if
Speaker 2: you stayed in a dark room for two days, your
Speaker 2: body would still have some of its normal cycle. It's
Speaker 2: not like it breaks down immediately, but over time, if
Speaker 2: you deprive your body of that light queue or you
Speaker 2: mess your cues up, then you can start having problems.
Speaker 2: So for example, if you work the night shift, you know,
Speaker 2: any of us who have had jet lag have had
Speaker 2: like a temporary period where circadian rhythm was like something's
Speaker 2: not right, and then it's had to get back to normal.
Speaker 2: But being off of your normal circadian rhythm too often,
Speaker 2: for example, working the night shift increases your risk of diabetes, obesity, depression, dementia,
Speaker 2: and some kinds of cancer. So these circadian rhythms seem
Speaker 2: to be important for a lot of reasons, at least
Speaker 2: for humans.
Speaker 1: Wow, and how widespread are circadian rhythm that everything on
Speaker 1: Earth has a circadian rhythm?
Speaker 2: Well, so like bacteria, humans, plants, lots of stuff has
Speaker 2: circadian rhythms. But our listener had a really great question,
Speaker 2: which is how on Earth do you have a circadian
Speaker 2: rhythm if you live in a place with no light?
Speaker 2: And so the three different situations that I looked into
Speaker 2: where there's no light are if you are, for example,
Speaker 2: at the North Pole during the time of year where
Speaker 2: you don't see the sun. There's like, I think a
Speaker 2: couple months where that's the case, if you live in
Speaker 2: a cave, or if you live in the deep sea.
Speaker 2: And then there's also organisms like naked mole rats that
Speaker 2: live underground. But I think naked molerats can peek their
Speaker 2: heads out every once in a while and see the
Speaker 2: sun to help in train their clock, so they get
Speaker 2: some light cues still, So let's start with if you
Speaker 2: live far north. So one thing that's important to note,
Speaker 2: which we touched on just a second ago, is that
Speaker 2: clocks don't go away immediately just because you're in total darkness.
Speaker 2: So at the start of the long night, they're probably
Speaker 2: fine because their body hasn't like forgotten the rhythm yet.
Speaker 2: And during the time of year when it's all light,
Speaker 2: they're probably also fine because the intensity of the light
Speaker 2: still changes over the course of the day, and your
Speaker 2: eyes are focusing on light intensity, not just whether it's
Speaker 2: there or not, so they can still keep their rhythms
Speaker 2: at that time of year. But there is a point
Speaker 2: in the winter where their clocks have not had appropriate
Speaker 2: input for long enough because it's been dark for so long,
Speaker 2: and they do seem to stop showing signs of twenty
Speaker 2: four hour cycles if you look at the reindeer, So
Speaker 2: it looks like at some point they do start free
Speaker 2: cycling essentially and their circadian rhythms start to break down. Wow,
Speaker 2: they don't seem to have physiological problems associated with that.
Speaker 2: I'm not quite sure why, but it looks like they
Speaker 2: do break down at some point, So.
Speaker 1: It's bad for them to be in the dark, like
Speaker 1: it would be better if they got light occasionally to
Speaker 1: sort of like correct their cycles or get them back
Speaker 1: on track.
Speaker 2: Yeah, So I was trying to figure out the answer
Speaker 2: to that, and I think that the answer is to
Speaker 2: some extent that it's complicated. So, you know, part of
Speaker 2: why we have cycles is that it helps us figure
Speaker 2: out like when we should be eating and stuff like that.
Speaker 2: And part of that, if you are a wild animal,
Speaker 2: is about when your food is even available, right, But
Speaker 2: if you're in the dark and all the other animals
Speaker 2: are in the dark all the time too, you might
Speaker 2: not need to have a circadian rhythm because it might
Speaker 2: you know, if you're, say you're a fox living in
Speaker 2: the Arctic circle, you want to make sure you're awake
Speaker 2: at the same time as the bunnies. But if it's
Speaker 2: complete darkness and everybody's free cycling, you don't really need
Speaker 2: to get up at a certain time because the bunnies
Speaker 2: could be out there at any time, and so it's
Speaker 2: not a helpful queue anymore to like have your activities
Speaker 2: sync to a certain time of day.
Speaker 1: I was wondering more about the internal stuff, Like you
Speaker 1: mentioned earlier that if your rhythm gets messed up your
Speaker 1: risk for diabetes and cancer and stuff. Is the same
Speaker 1: thing true for reindeer when they're free cycling.
Speaker 2: Yeah, so I don't know the answer for reindeer, but
Speaker 2: I did try to find the answer to that question.
Speaker 2: I was able to find some information about blind cavefish.
Speaker 2: So there are fish that live in caves that have
Speaker 2: closely related ancestors that live outside of caves. Oh, okay,
Speaker 2: And so you can compare you know, essentially these like
Speaker 2: sister species or sibling species and see how they differ.
Speaker 2: And the species that live in caves don't have shorter lives,
Speaker 2: and in a lot of cases they have longer lives
Speaker 2: than their surface living counterparts. Well, okay, and then let
Speaker 2: me tell you about their circadian rhythms. That's the important
Speaker 2: piece here. So people were trying to figure out if
Speaker 2: cavefish have circadian rhythms, and they were trying to figure out, like, okay,
Speaker 2: in the absence of light, how do you do that?
Speaker 2: And so one idea they had was that maybe bats
Speaker 2: that go in and out of the cave are what
Speaker 2: they're queuing into. Because when the bats leave where they
Speaker 2: come back, they poop in the water and that poop
Speaker 2: provides food for a lot of cavefish, right, so maybe
Speaker 2: that's what they're sinking to, but there was no evidence
Speaker 2: that that was actually happening, So it looks like they're
Speaker 2: not sinking to that.
Speaker 1: But there could be a lot of similar effects right
Speaker 1: where things are happening outside the cave, and like even
Speaker 1: the microbes in the air or something like that could
Speaker 1: be affecting. You could be sensing indirectly the fact that
Speaker 1: there's day and night outside the cave from inside the cave.
Speaker 2: Yeah, that's right. But so people have also brought the
Speaker 2: cavefish into the lab, and when they bring them into
Speaker 2: the lab and they expose them to normal light cycles,
Speaker 2: they can develop circadian rhythms. So they still even though
Speaker 2: they don't have eyes, they still must have like the
Speaker 2: cells needed to detect light, and they can develop rhythms.
Speaker 2: But it looks like various parts of their circadian clock
Speaker 2: are messed up. So if you look at things from
Speaker 2: the genetic level, it's kind of messed up, and it
Speaker 2: looks like they also for the most part, are losing
Speaker 2: their circadian rhythms in the cave, but that doesn't seem
Speaker 2: to be shortening their lives.
Speaker 1: Wow, fascinating, Yeah, which.
Speaker 2: Is not what I expected. Like I spent a long
Speaker 2: time being like, well, no, what is the queue? They
Speaker 2: have to have circadian rhythms, And then I found a
Speaker 2: review paper that pretty much was like, the rhythms kind
Speaker 2: of seem to disappear in caves. They're just kind of
Speaker 2: like moving around whenever and sleeping whenever.
Speaker 1: And that's okay, And that's okay.
Speaker 2: We're not judging.
Speaker 1: Teenagers everywhere are like see mom, it's fine for me
Speaker 1: to stay up until two.
Speaker 2: Am, all right, and their rooms are kind of like
Speaker 2: messy caves. And I see lots lots of points of
Speaker 2: comparison here.
Speaker 1: All right, what about at the bottom of the ocean
Speaker 1: where light doesn't filter down?
Speaker 2: Okay, so this is interesting. So after I had finished
Speaker 2: the research on caves, my expectation was that animals that
Speaker 2: live in the deep sea are also going to not
Speaker 2: really show circadian rhythms because they're you know, they're down
Speaker 2: in an area where the light isn't getting to But
Speaker 2: I thought, well, you know, maybe there's still some cues,
Speaker 2: Like a lot of the food that comes to the
Speaker 2: deep sea comes from things just sort of like dying
Speaker 2: and raining down, and I thought, maybe there's like a
Speaker 2: daily pattern to how the food rains down. But this
Speaker 2: is actually really hard to study.
Speaker 1: When the carcass snacks happen, that's really.
Speaker 2: Well, you know, I pay attention to snacks.
Speaker 1: Kids, dead bodies are falling, come on outside. What is
Speaker 1: it like to be a parent at the bottom of
Speaker 1: the ocean.
Speaker 2: I mean, when a whale falls down, it is like
Speaker 2: buffet for months. The videos are messed up. But so
Speaker 2: the way that folks tend to study this is, you know,
Speaker 2: they either take the deep sea animals into the lab,
Speaker 2: but if you bring them into the lab, you're often
Speaker 2: like turning on lights to study them, and so now
Speaker 2: they're in like a not natural environment. And you know,
Speaker 2: labs in general are not like the bottom of the sea.
Speaker 2: But another way that people study it is they will
Speaker 2: put like essentially mobile labs. They'll lower them down to
Speaker 2: the bottom of the sea and then they'll like take
Speaker 2: pictures or videos and try to see if they can
Speaker 2: detect cycles and what's happening down there. But another problem
Speaker 2: there is that they turn on lights often when they
Speaker 2: do that. Yeah, and so this stuff is hard to study.
Speaker 2: But I found a study that did use cameras with lights,
Speaker 2: and they found that a lot of species didn't show
Speaker 2: detectable patterns, but it was also hard to get large
Speaker 2: sample sizes. But they did find that there is a
Speaker 2: kind of worm that lives in a tube and there's
Speaker 2: a pattern to when it sticks its head out of
Speaker 2: the tube to try to get food. They were looking
Speaker 2: at different things that were changing in the environment, and
Speaker 2: it looks like this behavior is correlated with the tides.
Speaker 2: So you can still feel the tides at the bottom
Speaker 2: of the sea. Oh wow, which is amazing. I didn't
Speaker 2: realize that.
Speaker 1: Yeah, thank you Moon, and see it's all connected. Yes,
Speaker 1: it turns out there is a through line for the
Speaker 1: whole episode.
Speaker 5: That's orry.
Speaker 2: I guess. Spaghetification is kind of interesting, but I guess
Speaker 2: so it's not just the tides, but the tides have
Speaker 2: different temperatures, so it could be temperature that's queueing this.
Speaker 3: Yea.
Speaker 2: The tides also can bring food, so maybe it's the
Speaker 2: food that's queuing the clocks. And this information is largely observational,
Speaker 2: so there's still a lot that we have left to learn,
Speaker 2: but some indication that tides can be what's impacting timing
Speaker 2: in the deep sea and that's literally everything I know
Speaker 2: about circadian clocks, because this is complicated.
Speaker 1: All right, So bottom line for us, what do we
Speaker 1: know about how circadie rhythms work? And animals that never
Speaker 1: see the sun.
Speaker 2: Sometimes you're poned and you can't create a circadian rhythm
Speaker 2: because you just don't have the cues. Other times you
Speaker 2: can find something that correlates with the light, or sometimes
Speaker 2: instead of having a circadian rhythm, you have a circ
Speaker 2: a title rhythm or something, and you're queuing in on
Speaker 2: some other environmental thing that can help you maintain a
Speaker 2: rhythm in your life.
Speaker 1: Well, I thought that answer was super colent, fragilistic. But
Speaker 1: let's hear what our listener says and see if there
Speaker 1: are follow up questions.
Speaker 5: Wow, thanks for answering my question. Never would have thought
Speaker 5: that deep sea creatures could sense the tides all the
Speaker 5: way down there. That's pretty cool.
Speaker 2: We are backed Jupiter, a fascinating planet that could kill
Speaker 2: us all. Arthur, what do you want to know about Jupiter?
Speaker 6: Hi, Denim and Kelly. Nice to talk to you guys.
Speaker 6: I have a rocket thrust issue.
Speaker 3: I know that we can't escape the gravity of a
Speaker 3: black hole no matter how powerful our rocket is, but
Speaker 3: I don't know the largest mass of a planet we
Speaker 3: can escape from with our current technology.
Speaker 6: I mean, can an.
Speaker 3: Average space rocket lift off from jupter, from the Sun,
Speaker 3: from a neutron star?
Speaker 6: I hope you have some funds are in this thanks.
Speaker 1: See, Jupiter is just so attractive gravitationally, people can't stop
Speaker 1: thinking about it.
Speaker 2: It's beautiful also, all right.
Speaker 1: So Arthur is wondering about taking off from planets because
Speaker 1: the more massive the planet, the stronger the gravity, the
Speaker 1: harder it is to lift off of. And he wants
Speaker 1: to know if an average rocket could actually get you
Speaker 1: off of Jupiter or even more exotic and denser locations.
Speaker 2: So the first thing I want to know is I
Speaker 2: can tell from the answer it's going to require math.
Speaker 2: Did you do these calculations or is there a website
Speaker 2: that has this information.
Speaker 1: There are a lot of websites that have this information,
Speaker 1: but I never trust them because you can find mistakes
Speaker 1: on those websites, which is the source of a lot
Speaker 1: of mistakes in like chat GBT, because it just like
Speaker 1: strips some from the websites and gives you the answer,
Speaker 1: sometimes in the wrong context or whatever. So I always
Speaker 1: double check these myself. All right, wow, so what matters
Speaker 1: for lifting off the surface? You're probably going to think
Speaker 1: escape velocity. And first I want to say it's not
Speaker 1: about escape velocity, but then it's going to turn out
Speaker 1: to be about escape.
Speaker 2: Velocity physicists, I know.
Speaker 1: So escape velocity famously is the speed you have to
Speaker 1: be going so you can escape the gravitational pull of
Speaker 1: an object. Right, So for example, if I'm standing on
Speaker 1: the surface of the Earth, how fast do I have
Speaker 1: to throw a baseball straight up so that it just
Speaker 1: keeps going forever? That it's kinetic energy over comes the
Speaker 1: potential energy, Well, that has to climb out of right,
Speaker 1: So as you move up away from the Earth, you're gaining.
Speaker 1: Potential energy has to come from somewhere. It comes from
Speaker 1: your kinetic energy. If you have enough kinetic energy, then
Speaker 1: you can go forever. Essentially, if your kinetic energy overcomes
Speaker 1: the potential, well you have to climb. So you have
Speaker 1: to go fast to escape the Earth. But the reason
Speaker 1: that's not what this is about is that that's not how
Speaker 1: rockets work. Right, Rockets you don't slingshot them from the
Speaker 1: Earth in one push. I mean, people are working on that,
Speaker 1: and it's hilarious, but traditional rockets.
Speaker 2: Wait, why is it hilarious and not inspirational?
Speaker 1: It's just like the grown up version of a nine
Speaker 1: year old boy's idea for how to get to space,
Speaker 1: you know, like, let's pull back a really big rubber band,
Speaker 1: you know. I mean, I knew they're working on sentrifusions
Speaker 1: and it's pretty cool, but it seems like impractical to me.
Speaker 1: Also because the g forces are insane, so I think
Speaker 1: you could probably launch like stuff into space, but not people.
Speaker 2: Anyway, that's my sense too. Yeah, you're launching stuff hard and.
Speaker 1: Payloads anyway, That's not how traditional rockets work. If you notice,
Speaker 1: when a rocket takes off, it's not going super duper fast.
Speaker 1: It's very slowly climbing, right, And that's because rockets don't
Speaker 1: have a single hard push at the beginning where they
Speaker 1: gain a lot of speed and then gradually lose it
Speaker 1: as they rise. They have a continual force. They have
Speaker 1: an engine on them, so rockets only have to go
Speaker 1: non zero velocity in order to move up. Right, as
Speaker 1: long as the force from the rocket is greater than
Speaker 1: the force of gravity from the Earth, it's going to
Speaker 1: be moving up okay, right, So it can move up
Speaker 1: super duper slowly. It could take like a year to
Speaker 1: take off from the planet, doesn't matter. It's not about
Speaker 1: escape velocity. It's about putting enough energy in to overcome
Speaker 1: the potential energy to the Earth, but doesn't have to all
Speaker 1: be upfront. So that's why it's sort of not about
Speaker 1: escape velocity.
Speaker 2: Okay. But so say you were lifting off at like
Speaker 2: a foot per second, that would be much more energetically expensive,
Speaker 2: wouldn't it, Because you're needing to like maintain the mass
Speaker 2: you're trying to send up as you slowly go up,
Speaker 2: And if you do it all faster, that's probably more efficient.
Speaker 1: It's more efficient. Yeah, And if you do it all
Speaker 1: at once, just by giving it one big push, then
Speaker 1: you don't need to bring any propellant with you and
Speaker 1: you can just accelerate the payload. Right Whereas if you're
Speaker 1: climbing up at a foot per second, yeah, you've got
Speaker 1: to bring the rest of the latter with you essentially,
Speaker 1: and you've got to lift that fuel. So we're definitely
Speaker 1: going to.
Speaker 2: Get there, okay.
Speaker 1: So what we do need to do is think about
Speaker 1: how much fuel we have to bring and how we
Speaker 1: can overcome this energy, and so you have to calculate
Speaker 1: how much kinetic energy do you need to overcome the
Speaker 1: potential energy the Earth. It's not important that it albeit
Speaker 1: at once, and rockets do it gradually. But the way
Speaker 1: to calculate that is to calculate what they call the
Speaker 1: delta V, the change in velocity that a rocket can provide.
Speaker 1: And in the end, this turns out to be very
Speaker 1: similar to the escape velocity, and it makes sense that
Speaker 1: it's similar because they're both connected to essentially how much
Speaker 1: energy you need to climb out of this gravitational well
Speaker 1: and so. On Earth, the escape velocity is about eight
Speaker 1: kilometers per second. That's how fast you would have to
Speaker 1: throw a baseball or launch a payload from the surface.
Speaker 1: But it's also very closely connected. We'll use the rocket
Speaker 1: equation in a minute to how much fuel you have
Speaker 1: to bring with you, and that's going to turn out
Speaker 1: to be the limiting factor of whether you can lift
Speaker 1: off the planet is can you practically bring enough fuel
Speaker 1: to get this much delta V? So on Earth you
Speaker 1: need like eight kilometers per second, and then you go
Speaker 1: to the rocket equation. The rocket equation says how much
Speaker 1: mass do you need to bring so that you can
Speaker 1: do this, so you can climb out of this gravitational well,
Speaker 1: because remember a rocket, what is it doing. It's throwing
Speaker 1: stuff out the back. Right. The way it works is
Speaker 1: it's conserving momentum. Imagine you like in a rowboat and
Speaker 1: you have a pile of bricks. You throw the bricks
Speaker 1: out the back of the rowboat. The bricks go backwards,
Speaker 1: you go forwards. That's how a rocket works. It's throwing
Speaker 1: stuff out the back. So you have to have that
Speaker 1: stuff in the rocket to throw out the back in
Speaker 1: order to propel it. It's helpful if that stuff also
Speaker 1: has the energy you can use to push the propellant.
Speaker 1: It doesn't have to be you can have those things
Speaker 1: be uncoupled. But in a chemical rocket you have fuel
Speaker 1: which is both propellant and the source of energy, and
Speaker 1: the rocket equation tells you what your mass ratio is.
Speaker 1: So on Earth, for example, you need a delta vive
Speaker 1: about ten kilometers per second. That tells you your mass
Speaker 1: ratio is nine, which means you need a nine to
Speaker 1: one fuel to payload mass ratio.
Speaker 2: That's not great.
Speaker 1: It's not great. Yeah, if you have like one hundred
Speaker 1: kilogram person and a thousand kilogram spaceship around them. You
Speaker 1: need nine times as much mass in fuel to get
Speaker 1: that thing into orbit.
Speaker 2: Wow. Yeah, how much worse is it for Jupiter? And
Speaker 2: does it scale linearly?
Speaker 1: It scales exponentially, which is the bad news. Right, And
Speaker 1: so say you're on a super Earth which has the
Speaker 1: mass of like five to ten times the Earth, then
Speaker 1: the escape velocity is like twenty five to thirty kilometers
Speaker 1: per second. Okay, that's not so bad. It's three to
Speaker 1: four times as much, but the mass ratio is ninety three.
Speaker 1: It's ten times as bad as it is here on Earth.
Speaker 2: Ninety three to one, ninety three to one.
Speaker 1: So instead of having a nine to one fuel to
Speaker 1: payload ratio, you have a ninety three to one fuel
Speaker 1: to payload ratio. So now like your rocket is basically
Speaker 1: just fuel, right, and that's just for a super Earth.
Speaker 1: Now go to Jupiter. Jupiter is so massive that it's
Speaker 1: escape velocity is like forty kilometers per second, and this
Speaker 1: gives a mass ratio of more than one thousand Wow. Right,
Speaker 1: so you'd need a fuel tank that's a thousand times
Speaker 1: bigger than your payload. This is probably even an underestimate,
Speaker 1: but essentially this is impossible for chemistry, right, The chemical
Speaker 1: rockets cannot achieve this. And if you went to the Sun, right,
Speaker 1: then the escape velocity from the Sun is four hundred
Speaker 1: kilometers per second, and so now the mass ratios are
Speaker 1: just astronomical. From a neutron star, the escape velocity is
Speaker 1: four tenths the speed of light. And so I couldn't
Speaker 1: even get my calculator to give me a number on this.
Speaker 1: W was just so big. And so the bottom line
Speaker 1: is that chemical rockets, where you have this fuel and
Speaker 1: you're slowly climbing out of the gravitational well, well they
Speaker 1: work pretty well if the escape velocity is low. Because
Speaker 1: the mass ratio is pretty small, you can afford nine
Speaker 1: to one, which sounded bad already to you, right, But
Speaker 1: on a bigger planet like a super Earth, it's pretty
Speaker 1: hard to use. And a Jupiter or the Sun or
Speaker 1: a neutron star, it's definitely not practical.
Speaker 2: So what about like a project orion's style propulsion system?
Speaker 2: So if you were exploding nuclear bombs out the back
Speaker 2: of your rocket to send you up, could you get
Speaker 2: off of Jupiter?
Speaker 1: Yeah? You could. This is limited to chemical rockets, right,
Speaker 1: and you can have other strategies you could build a
Speaker 1: space elevator, right. You could have nuclear propulsion, absolutely, and
Speaker 1: especially if you're launching the nuclear weapons behind the rocket
Speaker 1: somehow so that they don't have to come along with
Speaker 1: the rocket, then you can escape this trap of having
Speaker 1: to bring all of your propellant with you. Yeah. Or
Speaker 1: if you have like a light sale with a laser
Speaker 1: behind it, you can use that to lift off of
Speaker 1: a planet. Or you could just build your thing in space. Anyway,
Speaker 1: while you're building it on the surface of Jupiter. Doesn't
Speaker 1: really make sense unless that's where your super villain hideout is. Oh,
Speaker 1: which case, I have to wonder Jupiter doesn't get a
Speaker 1: whole lot of light. I wonder how your circadian rhythms
Speaker 1: are going in your supervillain layer one.
Speaker 2: You better hope that Bread isn't sending the Earth greening
Speaker 2: into your your supervillain layer on Jupiter.
Speaker 1: Oh, maybe he's saving us, right, maybe he's using the
Speaker 1: Earth that doesn't really work, using the Earth to crush
Speaker 1: somebody else's supervillain layer.
Speaker 5: Yeah, not a.
Speaker 2: Great plan, Brad, not paying you to write that plot, Daniel.
Speaker 1: So yeah, chemical rockets work essentially only on smaller planets.
Speaker 1: On bigger planets, you need other technologies, but those technologies
Speaker 1: are not impossible. So I think if we did evolve
Speaker 1: on Jupiter or on the surface of a neutron star,
Speaker 1: technically it's still possible to get off of those, but
Speaker 1: not with rockets.
Speaker 2: All right, let's see if Arthur has any follow up questions,
Speaker 2: and maybe he'll tell us what his supervillain plan is.
Speaker 6: Thanks guys for the kind of answer my question. I
Speaker 6: knew that enough from a bigger planet would be hard,
Speaker 6: but I didn't knoww it would be almost impossible, at
Speaker 6: least for chemical rockets, as you explained. I think that
Speaker 6: this either puts a big as the risk on plans
Speaker 6: for space exploration since the range of celestial bodies we
Speaker 6: could visit would be very limited, or either forces research
Speaker 6: for more efficient technologies. As you mentioned, all I have
Speaker 6: to say about supervillains is that they love rockets these days,
Speaker 6: so I do not doubt they have plans for this
Speaker 6: massive loudness.
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