Speaker 1: If telescopes looked back from afar, what signs of Earth
Speaker 1: would glow? Would life in air and seas be something
Speaker 1: it could know?
Speaker 2: As sole survivors in the genus Homo, we've taken the throne.
Speaker 2: But are there other genera where a species is similarly alone?
Speaker 1: From the tiniest speck to giants tall? How small or
Speaker 1: big can thinkers be at all?
Speaker 3: Mmmmm woo which whatever questions keep you up at night,
Speaker 3: Daniel and Kelly's answers will make it right.
Speaker 1: Welcome to Daniel and Kelly's Extraordinary Universe. Listener Questions number
Speaker 1: thirty eight.
Speaker 4: Whoop whoop. Hello. I'm Kelly Waiter Smith.
Speaker 2: I study parasites and space, and it's an exciting week
Speaker 2: to be someone who studies space.
Speaker 4: Do you know why, Daniel?
Speaker 2: Hi?
Speaker 1: I'm Daniel. I study aliens and physics. And yes I'm
Speaker 1: aware of the Artemis launch because I do not live underground.
Speaker 4: Well okay, but so here's the thing, right, Okay, so
Speaker 4: you know.
Speaker 2: Of course I was watching the Artemis launch, and I
Speaker 2: was watching it when my daughter got off the bus
Speaker 2: and got home from school, and she came home and
Speaker 2: she's like, what are you watching?
Speaker 4: And I was like I'm watching the humans that are
Speaker 4: going back to the Moon, and she goes, what, and so,
Speaker 4: you know, I haven't didn't know.
Speaker 2: No, And so I don't think that the kids are
Speaker 2: like talking about this, Like I don't think that like
Speaker 2: this generation is very excited about the fact that we're
Speaker 2: sending people back to the moon.
Speaker 4: What's your sense?
Speaker 1: That's a great question. And you know, I just realized
Speaker 1: now that I don't think I've discussed it with my
Speaker 1: kids at all. I just sort of watched it myself,
Speaker 1: and I have no idea if they know anything about it.
Speaker 1: Hold on, let's find out.
Speaker 4: Okay, isn't she supposed to be at school right now?
Speaker 1: Hi, Hazel? Did you know that we just sent astronauts
Speaker 1: back to the moon? You know about Artemis?
Speaker 5: Wait on the podcast?
Speaker 1: Yes Live? And do you think it's cool or whatever?
Speaker 1: I think it's interesting, but I probably wouldn't have been
Speaker 1: very much time thinking about it. Cool. All right, thank you,
Speaker 1: have a good day. Okay, thanks Pye.
Speaker 4: Disappointing answer.
Speaker 2: Yeah, for all the money that was spent on it, Yeah,
Speaker 2: I mean Ada was excited and then we so, you know,
Speaker 2: we watched she sat with me, we watched the launch
Speaker 2: and then we sat for a while and we were
Speaker 2: watching the like live feed, and she was like, well,
Speaker 2: when do we get to see like the astronauts, and
Speaker 2: as like, I guess they're not going to show you
Speaker 2: the inside. So, like you know, they were doing they've
Speaker 2: got to go around Earth a couple times before they
Speaker 2: leave you know, the orbits of Earth to head to
Speaker 2: the Moon, and I guess they decided they weren't going
Speaker 2: to show the astronauts on the inside because they were
Speaker 2: you know, doing multiple tasks or whatever. But Ada was
Speaker 2: really bummed. She's like, well, I want to see what
Speaker 2: they look like.
Speaker 1: What it's like for them, and then imagined herself in
Speaker 1: that ship.
Speaker 2: Probably yeah, yeah, And so not only had she not
Speaker 2: heard about it, but then she really didn't get to
Speaker 2: see the people at all. And the next day she
Speaker 2: didn't ask is there any news about the astronauts? And
Speaker 2: I know they're not landing, but I think the kids
Speaker 2: are already sort of not super excited about it.
Speaker 1: Well, let me ask you what aspect of it is
Speaker 1: very cool for you? Which part is getting you excited?
Speaker 2: Well, so I'm hoping that we will start doing more
Speaker 2: consistent research, like we'll set up a research station, and
Speaker 2: then we will we'll have like long term research program
Speaker 2: on the Moon so that we can.
Speaker 1: Learn about like life and low gravity out in space
Speaker 1: and radiation and all the kind of stuff you guys
Speaker 1: recommended in your book that we need to do to
Speaker 1: be serious about settling space.
Speaker 2: Yeah, I'm hoping we do all of that stuff now,
Speaker 2: but you know that would be really expensive, and so
Speaker 2: that would require us to do something very different than
Speaker 2: what we did last time, which was just go to
Speaker 2: beat the Soviets and then go home because we had
Speaker 2: done it. And so you know, if we're just going
Speaker 2: to show the Chinese that we can do it again,
Speaker 2: just to beat them before they try to do it,
Speaker 2: and then we stop, then it will be sort of
Speaker 2: anti climactic and like, oh, all right, we spent a
Speaker 2: bunch of money to prove we could do it again,
Speaker 2: and now we're going to stop. Eah. But I don't
Speaker 2: know what about you? Are you excited and if so, why.
Speaker 1: Well that's just so like thoughtful and future thinking. Is
Speaker 1: there a part of you that just feels like a
Speaker 1: visceral excitement like big rocket go boom, you know, or
Speaker 1: like people are in space? You know, there's just the
Speaker 1: immediacy of that. Isn't that cool?
Speaker 4: That is cool.
Speaker 2: I'm glad the big rocket didn't go boom. That's what
Speaker 2: I was worried about that I wanted big rocket.
Speaker 4: Not go boom.
Speaker 2: But no, I mean, I thought that was cool. But
Speaker 2: I also think it's cool just when we get a
Speaker 2: satellite into space without the rocket going boom, Like it's
Speaker 2: very easy to get me excited about space stuff. But yeah, yeah,
Speaker 2: I think it's cool that we've got humans going to
Speaker 2: the Moon again.
Speaker 1: I'm always excited about, like things go into space. That's
Speaker 1: very cool. Every Falcon launch or whatever. I think it's
Speaker 1: pretty fun. This mission, in particular, I'm like not sure
Speaker 1: what we're learning or what we're doing. We haven't done before.
Speaker 1: So it's also exciting in the sense that things are
Speaker 1: starting again and we're exploring, we're working towards something in
Speaker 1: the future. So a lot of the excitement for me
Speaker 1: also comes from the promise of what this might mean.
Speaker 2: If we go to the Moon, touch our feet down
Speaker 2: on the Moon and we don't stay this time, I
Speaker 2: will be bummed that we didn't spend that money on
Speaker 2: things like an exploratory mission to Europe up or something
Speaker 2: like that like we could have explore used robots to
Speaker 2: explore other stuff and gotten more data and like, cause
Speaker 2: you know, robots can do more than humans can. And
Speaker 2: so if we spent all this money to get humans
Speaker 2: to the moon and then we don't figure out a
Speaker 2: way to stay there.
Speaker 4: I'll be bummed.
Speaker 2: Anyway, Hopefully this time we'll stay and we'll do more
Speaker 2: research and get the data. But anyway, we'll have to
Speaker 2: wait and see. But I'm glad the rocket did not
Speaker 2: go boom.
Speaker 1: Yep, and good luck to all the astronauts.
Speaker 2: Yes right, and oh yeah, and you know, I am
Speaker 2: excited that we have a woman in space, we have
Speaker 2: a black man in space, and we have a Canadian
Speaker 2: in space, and so those are all exciting things to me.
Speaker 4: So I am excited about those firsts.
Speaker 2: I mean, there have been Canadians in space before, but yeah,
Speaker 2: not to the moon, you know, so hooray.
Speaker 1: And I'm excited to be answering questions from our listeners
Speaker 1: today because one of the exciting things about space is
Speaker 1: the sense of exploration, pushing back on what we don't know.
Speaker 1: And that's exactly what we're trying to do here on
Speaker 1: the podcast, is to dive deep into your curiosity and
Speaker 1: push back what you don't understand to broaden your mental
Speaker 1: picture of the universe.
Speaker 4: If Daniel wasn't here, we would never get to the point.
Speaker 2: So thank goodness we have Daniel to keep us on track,
Speaker 2: and so let's go ahead and get to Jonas's question
Speaker 2: about space telescopes.
Speaker 6: Hi Daniel, Hi Kelly. My question came to mind some
Speaker 6: time ago, back when the James Reap telescope was a
Speaker 6: big topic in the media and in podcasts like yours.
Speaker 6: If it were pointed at Earth from the distance of
Speaker 6: the nearest Earth like exoplanet, what could it actually detect?
Speaker 6: How would Earth's appearance be shaped by its physical properties?
Speaker 6: And could any biological signatures such as signs of life
Speaker 6: in the atmosphere realistically be inferred. Many thanks for exploring
Speaker 6: this question.
Speaker 4: This is a fantastic question that I don't know the
Speaker 4: answer to.
Speaker 1: It's a very cool question because he's putting himself in
Speaker 1: the minds of aliens and wondering if there are aliens
Speaker 1: out there that are similar to us, could they see
Speaker 1: us right. It's a great question because obviously we haven't
Speaker 1: seen any aliens yet, and so he's wondering if the
Speaker 1: reverse is true. Maybe aliens will discover us before we
Speaker 1: discover them, but it's also a good way to understand
Speaker 1: what we could possibly see with our technology.
Speaker 2: Yes, and so of course you would love someone who
Speaker 2: is thinking like an alien or thinking about aliens. And
Speaker 2: so let's go ahead and talk about what telescopes can see.
Speaker 1: Yeah. I think there's a lot of misconception about what
Speaker 1: telescopes actually do. And people imagine that really powerful telescopes
Speaker 1: could maybe like show you what's happening on the surface
Speaker 1: of an exoplanet or something. But telescopes are really good
Speaker 1: at seeing distant, dim, huge things. They're not very good
Speaker 1: at seeing small things that are far away, which is
Speaker 1: what Jonas is hoping that they could see. And the
Speaker 1: reason is a little bit of physics which is important
Speaker 1: to understand telescopes, which is the diffraction limit.
Speaker 2: And so you're saying Earth would be a small thing,
Speaker 2: So what would be a big thing like the Sun?
Speaker 2: Or are we talking about like entire solar systems or
Speaker 2: entire galaxies?
Speaker 4: What counts as big?
Speaker 1: Yeah, galaxies are big, and that's why when we point
Speaker 1: James web telescope into the distant cosmos, the kind of
Speaker 1: things we're seeing are entire galaxies. Because they're big, they
Speaker 1: take up enough of the sky that we can resolve them.
Speaker 1: We can see them.
Speaker 2: Back to diffraction. I got you off track, that's what
Speaker 2: I do? You get au spec on? Okay.
Speaker 1: Essentially, there's a minimum pixel size in the sky the
Speaker 1: telescopes can resolve. And the reason is that light at
Speaker 1: this scale acts like a wave. If light was just
Speaker 1: made of tiny, little geometrical particles, little balls with perfect resolution,
Speaker 1: then you wouldn't have this effect. But when light enters
Speaker 1: the telescope, it goes through an aperture. Right, This is
Speaker 1: the opening and the telescope that gathers the light. And
Speaker 1: anytime a wave goes through a hole or through any
Speaker 1: sort of opening, you can model it like a series
Speaker 1: of sources across that opening. This is sort of like
Speaker 1: the granddaddy version of interference.
Speaker 5: Right.
Speaker 1: If you have, for example, two sources of light, then
Speaker 1: in some places those two sources of light will line
Speaker 1: up to be brighter, and in other places they will
Speaker 1: light up to cancel out. Right, Because waves go up
Speaker 1: and down and up and down, and if the up
Speaker 1: from one wave hits the down from the other wave,
Speaker 1: they cancel out and if the up hits the up,
Speaker 1: then they add to each other, right, So that's interference.
Speaker 1: So if you have two sources of light, then you
Speaker 1: get like an interference pattern across a screen. Right. Well,
Speaker 1: when light comes through an opening, you can model that
Speaker 1: as a bunch of sources across the.
Speaker 4: Opening, okay, and so some will interfere.
Speaker 1: And so exactly you get interference between all of those.
Speaker 1: And so you can't have an opening, you can't have
Speaker 1: an aperture, you can't gather light without getting some interference.
Speaker 1: It's impossible to avoid interference. This is the process we
Speaker 1: call diffraction. Anytime light passes through an opening, you get
Speaker 1: interference among itself because the light that comes out of
Speaker 1: the opening is just like as if you had a
Speaker 1: series of sources across that opening, okay, And so any
Speaker 1: optical system, even if you have perfect optics with no
Speaker 1: app or anything like that, you're gonna get interference because
Speaker 1: you have an aperture, and that causes fuzziness, right, And
Speaker 1: so essentially you can't resolve things that are really really small.
Speaker 1: And the size to the effective resolution, the size of
Speaker 1: a pixel on the sky depends on the size of
Speaker 1: your aperture and the wavelength of light that you're gathering,
Speaker 1: and so for various wavelengths and various sizes of your telescope,
Speaker 1: you can resolve a pixel in the sky of various sizes.
Speaker 1: So the human pupil has an aperture that's like a
Speaker 1: few millimeters across, and so its diffraction limited resolution for
Speaker 1: like visible light is like ten or twenty arcseconds, and
Speaker 1: Hubble is like two and a half meters across, and
Speaker 1: so its diffraction limited resolution is like zero point one
Speaker 1: arc seconds, right, so much much smaller. So the pixels
Speaker 1: you get with Hubble are much smaller in the sky
Speaker 1: than the pixels you get from the naked eye because
Speaker 1: has a big your aperture, and James Webb is like
Speaker 1: six and a half meters wide, so it's even better.
Speaker 1: But still these pixels are too big to see like
Speaker 1: the surface of an exoplanet. You're never gonna like spy
Speaker 1: on an alien having dinner on an exoplanet because the
Speaker 1: size of that alien dinner in our sky is much
Speaker 1: much smaller than anything we can resolve. So what these
Speaker 1: telescopes are good at is accumulating a bunch of photons
Speaker 1: from dim things that are huge, big enough to see
Speaker 1: in our sky, but too dim to make out with
Speaker 1: the naked eye, so you can just point the telescope
Speaker 1: at them for a long time and then you can
Speaker 1: gather enough photons so that it then appears. A great
Speaker 1: example is like Andromeda. Andromeda is really big. It's a
Speaker 1: huge galaxy. It's actually quite large in the sky. It's
Speaker 1: bigger than a full moon, but you can't see it
Speaker 1: with the naked eye because it's too dim. But you
Speaker 1: point a telescope at it and gathered for a while,
Speaker 1: you can get a really nice picture of Androma because
Speaker 1: it's big, much bigger than diffraction limited resolution and just
Speaker 1: too dim for your eye to make out, so your
Speaker 1: telescope can accumulate enough photons to get an image of it.
Speaker 2: Okay, so the good news is that the telescopes save
Speaker 2: us from ourselves. We can't be creepy and spy on
Speaker 2: the aliens in great detail.
Speaker 1: That's not good news. No, we want to be creepy
Speaker 1: and spy on the aliens.
Speaker 2: Oh okay, okay, but what can we learn about the aliens?
Speaker 2: Can we learn if they are there or not? Like,
Speaker 2: can we detect life or not?
Speaker 1: So currently with like jwst A distant Earth from a
Speaker 1: nearby exoplanet would just be a pixel. Right, Okay, you
Speaker 1: just see like one pixel. Now, with future telescopes, maybe
Speaker 1: we could see more, right, but to have a resolution
Speaker 1: and like spy on the surface of the planet, you'd
Speaker 1: need an aperture like the size of the sun. Wow,
Speaker 1: all right, we're talking about a telescope the size of
Speaker 1: the Sun, and that's possible. You can actually use the
Speaker 1: Sun and it's gravity to bend light and focus it
Speaker 1: into a collector, so you could use the whole solar
Speaker 1: system as a telescope. That's like really an idea we
Speaker 1: could pull off one day and you could use that
Speaker 1: to look at aliens having dinner. But currently that whole
Speaker 1: alien planet would be a pixel. That doesn't mean it
Speaker 1: you couldn't learn anything about it, right, It would be
Speaker 1: a super interesting pixel because if you think, oh, it's
Speaker 1: just one pixel, it's just one piece of information. But
Speaker 1: there's a lot of information in two different dimensions. There's
Speaker 1: how the pixel varies with time and also how the
Speaker 1: brightness of the pixel varies versus wavelength. Right, one pixel
Speaker 1: means contributions from lots of different frequencies of light. Is
Speaker 1: it red? Is it blue? Are there greens in there?
Speaker 1: And we can tell a lot from how the light
Speaker 1: varies with time and how the light varies with frequency.
Speaker 4: Okay, what can we tell?
Speaker 1: So Earth emits in two major ways. Number one is
Speaker 1: it glows just because it has a temperature, right, Like
Speaker 1: Earth is pretty cool, and everything in the universe that
Speaker 1: has a temperature glows. And so you can tell the
Speaker 1: temperature of Earth by the frequency at which it glows.
Speaker 1: Like you take that pixel and you pass it through
Speaker 1: a prism, and you can see which colors of light
Speaker 1: come out. And from the various frequencies of light, you
Speaker 1: can see the black body radiation of Earth. And you
Speaker 1: can use that to deduce the surface temperature of Earth
Speaker 1: from a distance. Right. That's very cool, and so you
Speaker 1: can tell, oh, the Earth is approximately what we call
Speaker 1: room temperature, or maybe it's not. Maybe it's covered in magma,
Speaker 1: it's super hot, or it's an ice ball, right, So
Speaker 1: you can learn something about the temperature of the Earth.
Speaker 1: The Earth also reflects a lot of sunlight. So it's
Speaker 1: two major emissions. There's black body radiation from the temperature
Speaker 1: of the Earth, and there's reflection of sunlight. A reflection
Speaker 1: mostly happens when you have oceans and when you have clouds,
Speaker 1: So you can tell, hey, is it cloudy on that
Speaker 1: planet or is it a water planet? Right, so you
Speaker 1: can get a sense for the cloud cover. You can
Speaker 1: get a sense for the water cover of this planet
Speaker 1: from this one pixel. Right. And the reason we've developed
Speaker 1: all these techniques is because nobody satisfied just seeing a pixel.
Speaker 1: They want to know more. And this is what scientists do, right.
Speaker 1: They learn how to extract as much information about the
Speaker 1: universe as possible from the data they got. They're not
Speaker 1: just going to say, like, well, let's just wait thirty
Speaker 1: years and build that sun size telescope, Like, no, we're
Speaker 1: here today, we want answer now, right. I love the
Speaker 1: ingenuity of scientists to extract this information from whatever tiny
Speaker 1: data they have.
Speaker 2: Totally yeah, because you're not getting funding for that sun telescope, probably,
Speaker 2: Kelly the what blanket is here to say? But so, okay,
Speaker 2: so if you know temperature and that there's water, you
Speaker 2: can maybe guess if there could be some sort of
Speaker 2: alien maybe it's alien bacteria. But now you've got like
Speaker 2: a hunch, yeah, about whether or not those aliens eat dinner.
Speaker 1: You can do even better than that, you can learn
Speaker 1: what the atmosphere is made out of and if there
Speaker 1: are biomarkers in the atmosphere. Right, So again we just
Speaker 1: still have one pixel, but we can do clever things
Speaker 1: like wait for sunrise on the planet. During sunrise, that
Speaker 1: alien star shines through the atmosphere of the planet and
Speaker 1: then those photons come to Earth. And because those photons
Speaker 1: have gone through the atmosphere and atmospheres tend to absorb
Speaker 1: at certain frequencies based on their composition, we can tell
Speaker 1: what's in the atmosphere. So there will be absorption lines
Speaker 1: in that spectrum. There will be gaps that tell you
Speaker 1: what molecules are in the atmosphere because those molecules ate
Speaker 1: some photons, and by seeing which ones they gobbled, we
Speaker 1: can tell what's there. So like, is there water in
Speaker 1: the atmosphere? Is their ozone in the atmosphere? Is their methane?
Speaker 1: Is their co two? Wow, some of these things are
Speaker 1: very strong biomarkers because they're in chemical dis equilibrium, like
Speaker 1: for example, oxygen is produced by photosynthesis, Methane typically produced
Speaker 1: by biology, though there are geological sources, but if you
Speaker 1: have them both in the atmosphere, they to react and disappear.
Speaker 1: So if you see oxygen and methane in the atmosphere
Speaker 1: of an exoplanet, that means that there is a constant
Speaker 1: replenishment of those things. There's something on that planet making oxygen,
Speaker 1: making methane. Neither of these things are smoking gun proof
Speaker 1: of alien life, but they're like, you know, good strong
Speaker 1: hints something out there is pumping out oxygen. So that's
Speaker 1: the kind of thing you can see again just from
Speaker 1: this pixel, right, super cool. I was reading a really
Speaker 1: cool paper yesterday about how you can watch the transit
Speaker 1: the eclipse to learn more about the atmosphere. Remember that
Speaker 1: sometimes the way you discover these exoplanets is by seeing
Speaker 1: them cross in front of their sun and dim the
Speaker 1: light of the Sun just a little bit, right. But
Speaker 1: the cool thing is that you can look at that
Speaker 1: dimming in various frequencies. Right, You can say, well, does
Speaker 1: red light dim? Just blue light dim? Does green light dim?
Speaker 1: And that's another way to tell what's in the atmosphere,
Speaker 1: because the width of the eclipse and the depth of
Speaker 1: the eclipse will depend on what's in the atmosphere. So,
Speaker 1: for example, if you're watching Earth pass in front of
Speaker 1: the Sun and you're looking at a frequency that nitrogen
Speaker 1: likes to absorb, then the Earth is going to seem
Speaker 1: wider because now you're including the atmosphere. And in other
Speaker 1: frequencies where nitrogen is transparent and the Earth is opaque,
Speaker 1: the Earth is going to seem smaller. Right, So it's like,
Speaker 1: is the eclipse including the atmosphere not? Is a frequency
Speaker 1: dependent answer. So by looking at different frequencies you can
Speaker 1: help determine Oh, what's this atmosphere? Mostly made out of
Speaker 1: really clever stuff?
Speaker 4: All right, yeah, you've got me.
Speaker 2: I'm amazed all of this from a pixel that that's
Speaker 2: pretty impressive.
Speaker 1: Oh, we're not even done yet. Right now, we got
Speaker 1: to think about time variation because as time goes on,
Speaker 1: the Earth is spinning, so the sun reflecting off the
Speaker 1: Earth will change based on where are the clouds, where
Speaker 1: are the oceans? And somebody actually did a study answering
Speaker 1: this exact question. They said, if we were in the
Speaker 1: next star system and we looked at Earth and we
Speaker 1: watched the variation of the reflection of sunlight off of
Speaker 1: the Earth, could we make a map of the Earth.
Speaker 1: And so you can look this up. It's amazing. It
Speaker 1: roughly maps out what the Earth's continents look like I mean,
Speaker 1: it's very very pixelated. It's basically just like bands, but
Speaker 1: it shows you, Oh, there's a bunch of land, then
Speaker 1: there's a really big ocean, then there's another little bit
Speaker 1: of land, then there's a smaller ocean. So you see
Speaker 1: the Pacific, you see the Atlantic, you see the Americas,
Speaker 1: you see Eurasia and Africa. Like again, not in great resolution,
Speaker 1: but much more than zero information. Super duper cool. It's
Speaker 1: very cool.
Speaker 4: It's amazing. Yeah, so cool.
Speaker 2: And that would be with the kind of stuff that
Speaker 2: James Webb Space telescope is seeing.
Speaker 4: You can get all that information.
Speaker 1: Okay, exactly, wow, But James Webspace Telescope is not the
Speaker 1: best way to do this, right. What you want to
Speaker 1: do when you're looking for exoplanets is you want to
Speaker 1: block the light from the Sun because these planets are
Speaker 1: like two billion times fainter than the star. So it's
Speaker 1: like you're looking at a firefly next to a street
Speaker 1: lamp you across the country. So it's very very hard
Speaker 1: to do and the right way to do that is
Speaker 1: to block the light from the street lamp. You can't
Speaker 1: just put like a circular shade to block the starlight
Speaker 1: because there's this weird interference effect where you end up
Speaker 1: having a bright dot at the center of that circle.
Speaker 1: We talked about this once we were talking about the
Speaker 1: history of discoveries, a really cool story about the Poisson spot. Anyway,
Speaker 1: they have a new generation of space telescopes they're building
Speaker 1: that have a complicated shaped starshield to avoid the sort
Speaker 1: of interference effect, and those are going to be awesome
Speaker 1: at seeing these exoplanets. Really we need a dedicated device
Speaker 1: with sensitivity at the right frequency and with one of
Speaker 1: these star shields, so you know, in the next couple
Speaker 1: of decades we're going to be seeing a lot more
Speaker 1: information about these exoplanets.
Speaker 2: Yay, all right, well that was an amazing answer. Let's
Speaker 2: go ahead and see what Jonas has to say.
Speaker 6: Hi, Daniel high Kelly, thank you so much for having
Speaker 6: my question on the podcast. You answer it exactly what
Speaker 6: it was going for intuit different. I kind of knew
Speaker 6: that the telescope would see very little, almost nothingly, but
Speaker 6: somehow that where my mind went, not what does it see?
Speaker 6: But what can we actually read from a tiny spot
Speaker 6: on the screen, And the answer blew me away just
Speaker 6: one pixel, and yet we can read so much from it.
Speaker 6: Hooray science and Okay, deep down, of course I was
Speaker 6: wondering as well, how realistic is it that we actually
Speaker 6: find signs of life with the James Webb telescope. Thanks
Speaker 6: for the great discussion.
Speaker 1: All right, we're back and we're answering questions from listeners.
Speaker 1: And here's a question from a regular listener who's got
Speaker 1: a really wonderful, charming accent.
Speaker 7: Hi, Kelly and Daniel, this is Jane from Redcar, England.
Speaker 7: I've got a question for you. Homo sapiens is the
Speaker 7: only species in the genus Homo unless Bigfoot is real?
Speaker 7: Are there any other species that are similarly alone? What
Speaker 7: animal genus is the most species in it? And what
Speaker 7: influences whether you end up with one are a thousand?
Speaker 7: And does it have anything to do with parasites? Still
Speaker 7: loving all that you do. Thank you so much for
Speaker 7: answering my question. Have an extraordinary twenty twenty six.
Speaker 1: All right, Kelly, tell us whether we're alone and whether
Speaker 1: we should feel bad about murdering all of our cousins.
Speaker 4: Well, you know, we didn't just murder them.
Speaker 2: We slept with them, We had the children and then
Speaker 2: well well we don't. We're not sure we ate them,
Speaker 2: and you know, check out a past Listener Questions episode
Speaker 2: for more information.
Speaker 4: And you know, in fact, we had.
Speaker 2: On November twenty fifth, twenty twenty five, we had an
Speaker 2: episode called how Long Have We Been Human? Where we
Speaker 2: had Scott Solomon on And so it's worth noting that, yes,
Speaker 2: the only species of Homo that's around right now is us,
Speaker 2: but there.
Speaker 4: Were a lot of other Homo species in the past.
Speaker 2: Maybe not a lot, but there were others, and they've
Speaker 2: just kind of died out for a variety of reasons.
Speaker 1: Have you ever wondered what it would be like today
Speaker 1: if we had several species and they were all like intelligent,
Speaker 1: but they had like, you know, different characteristics, different kinds
Speaker 1: of intelligence and different kinds of strength. Would that be
Speaker 1: wonderful and amazing or like divisive and political?
Speaker 2: I want to believe it would be wonderful and amazing,
Speaker 2: But I am a bit of a cynic, and I'm
Speaker 2: a little.
Speaker 4: Bit scared of how our species would handle that.
Speaker 1: What do you think, Well, I think the fact that
Speaker 1: we killed them off before written history already tells us
Speaker 1: the answer. We're not very tolerant of differences.
Speaker 2: Yeah, no, okay, anyway, that's a true downer right there.
Speaker 2: But anyway, okay, so Jane wanted to know about other examples,
Speaker 2: and so there's a couple of fun ones here. So
Speaker 2: the platypus is another species that is the only member
Speaker 2: of its genus. Daniel doesn't like me saying Latin name,
Speaker 2: so I'm going to try to I'll avoid them. Red
Speaker 2: pandas are the only species in their genus, and in
Speaker 2: fact they're also the only species in their family.
Speaker 1: But give us a reminder, species, genus, family. I mean,
Speaker 1: I know, as a professional biologist, this is just like
Speaker 1: back of the hand stuff for you. Why are you laughing?
Speaker 1: What are you joking about it?
Speaker 2: You know in my notes that I wrote this all
Speaker 2: down because I either have to say the mnemonic out loud,
Speaker 2: and the only one I memorized is dirty, and so
Speaker 2: I will not be saying it on the show, So
Speaker 2: I wrote it. So, yeah, you got kingdom, then phylum,
Speaker 2: then class order, family, genus, then species.
Speaker 1: And I've always wondered, like why these divisions? Are these
Speaker 1: arbitrary dotted lines humans have drawn? Or could you have
Speaker 1: nineteen or four? Like why this number of categories?
Speaker 2: Yeah, that is a good question. We were going to
Speaker 2: get into that a little bit later. Let's get into
Speaker 2: that now though, and so all right, yeah, so to
Speaker 2: some extent it probably is arbitrary. And so, like the
Speaker 2: classification system was started by Linnaeus and like I think
Speaker 2: the sixteen hundreds, and this was long before we knew
Speaker 2: about you know, evolution, long before the theory of natural
Speaker 2: selection came along. And so this was before we had like,
Speaker 2: you know, evolutionary trees and phylogenetic trees, and so to
Speaker 2: some extent it must have been arbitrary because we didn't
Speaker 2: have these like connections in our mind, and we didn't know,
Speaker 2: you know, about one species coming from another. But there's
Speaker 2: some reason to believe that they're useful in like thinking
Speaker 2: about evolution questions and that they are real. But so
Speaker 2: I read a paper that at least for the genus level,
Speaker 2: they were trying to decide, like, is what we're seeing
Speaker 2: in terms of categories of genera real? And so what
Speaker 2: they did was they looked at real rates at which
Speaker 2: we think species are being made and real rates at
Speaker 2: which we think species are going extinct, and then they
Speaker 2: sort of ransom models and they said, okay, if we're right,
Speaker 2: about calculating some of this stuff. Then how often should
Speaker 2: you see genera popping up? How many species should you
Speaker 2: see in each genus?
Speaker 1: But do we even have a definition for genius? Like
Speaker 1: I know, definition of species, It exists, even if it's
Speaker 1: controversial and fuzzy. Is the definition of a genus have
Speaker 1: some basis in biology? Or is it just like I'm
Speaker 1: putting this here and that there?
Speaker 2: Yeah, so different types of taxonomists sometimes have difference.
Speaker 1: And then we have taxonomy of taxonomists.
Speaker 4: Now, yes, yeah, yeah.
Speaker 2: A paper I was reading was lamenting that different kinds
Speaker 2: of taxonomists sometimes have different criteria for when they identify
Speaker 2: something as a genus or not, And so they were
Speaker 2: arguing that we needed to try to decide is it
Speaker 2: possible to have a category of genus that is the
Speaker 2: same for everybody? And if we don't have that, how
Speaker 2: big of a problem is it? And so, yes, to
Speaker 2: some extent, some of the stuff that we're talking about
Speaker 2: today is going to be arbitrary because this is human's
Speaker 2: best attempt at categorizing nature that does not care about
Speaker 2: us and our attempts to categorize things. And if you
Speaker 2: look back at this stuff, like two hundred years from now,
Speaker 2: you might find that genuses have been split or genuses
Speaker 2: have been clumped together because we've decided these things are
Speaker 2: actually like more closely related. We just hadn't looked at
Speaker 2: the genetics before. We hadn't had a chance to get
Speaker 2: around to it.
Speaker 1: I see. So in some sense, to answer the question
Speaker 1: on arbitrary choices made by taxonomists hundreds of years ago.
Speaker 1: But in another sense, there must be something about like
Speaker 1: the platypus which makes it different from other species, not
Speaker 1: just that it got randomly categorized into its own genus.
Speaker 1: It's like more different from all the other species than
Speaker 1: most species. Right, there's like a larger phenotypical distance in
Speaker 1: some sense.
Speaker 2: Yeah, right, And so you definitely shouldn't come away from
Speaker 2: this conversation thinking this is like totally arbitrary and random.
Speaker 2: You know, like there's many many people working on this stuff.
Speaker 2: We now have a lot of genetic data. A lot
Speaker 2: of people have spent time looking at the you know,
Speaker 2: the internal organs of these species, the external features of
Speaker 2: these species, the you know, genetic information from these species.
Speaker 2: We have a lot of data that we're bringing to
Speaker 2: bear on this, and in a month or two we're
Speaker 2: going to have Scott Egan on the show talking about
Speaker 2: how we define species, so we'll have a lot more
Speaker 2: information on that coming soon. But like, people have collected
Speaker 2: a ton of data, thought very carefully about this stuff,
Speaker 2: and a lot of the relationships between organisms we are
Speaker 2: like nearly certain are true. But the question is just
Speaker 2: when do you say, Okay, we're stopping here and we're
Speaker 2: putting a name on what's happening right here, you know
Speaker 2: what I mean. Like, it's definitely these relationships are flowing,
Speaker 2: and we sort of know in the directions in which
Speaker 2: they're flowing. The question is just when do you stop
Speaker 2: and say, what's happening right here gets a name, right, okay?
Speaker 1: And so like the planet Post is a famous example
Speaker 1: because it really isn't anything else sort of near it
Speaker 1: in the phenotypical tree of life, right, it really is
Speaker 1: sort of kind of on its own.
Speaker 4: Yeah, it looks real weird.
Speaker 1: And the red Pandas I'm confused about that because there
Speaker 1: are other.
Speaker 2: Pandas Panda is an unfortunate choice of a name. Actually,
Speaker 2: I can't remember if the like what most of us
Speaker 2: think of as pandas, like the big black and white bears,
Speaker 2: if they were named first, or if red pandas were
Speaker 2: named first, but they're not, you know, same way starfish
Speaker 2: aren't really fish.
Speaker 4: Both of those pandas are not closely related.
Speaker 1: I love that the Latin name here means fire colored cat.
Speaker 2: Yes, yes, yes, and we it's a good name. But
Speaker 2: we let French zoologists George Cuvier name it. But the
Speaker 2: locals at the time, who of course already knew about
Speaker 2: it long before Europeans.
Speaker 4: Went in and were like, this is new.
Speaker 2: They called it wah or chitwah based on its vocalization,
Speaker 2: so that's probably what we should have called it.
Speaker 4: But anyway, we call it the red panda.
Speaker 1: And this thing is not just alone in its own
Speaker 1: genus right.
Speaker 2: Right, it's alone in its family, which is one category up,
Speaker 2: so family genus species.
Speaker 4: Pretty cool?
Speaker 1: Wowty, it really killed all of its.
Speaker 4: Cousinshn, it did have some.
Speaker 2: I think it had some past relatives that died. I
Speaker 2: can't imagine this sweet little red panda killing off it's
Speaker 2: relatives the way we did or the way we may have.
Speaker 1: But a fire cat could have done.
Speaker 2: That's that's true. I met a red panda once and
Speaker 2: it had arthritis and moved very slowly, so they don't
Speaker 2: seem vicious to me. But she had a very long,
Speaker 2: nice life in a zoo. Ardvarks are another member that's
Speaker 2: alone in their genus. But this one's also alone in
Speaker 2: its family, like the red pandas, and it's alone in
Speaker 2: its order, which is one level above family, so order family,
Speaker 2: genus species, ardvarks are alone in there. They had other
Speaker 2: relatives but they died off. So there's some examples. But actually,
Speaker 2: as a more general case, I found a couple of
Speaker 2: different estimates here, somewhere between thirty to forty percent based
Speaker 2: on the numbers that I found of genera of animals
Speaker 2: have only one species in them. So there's a lot
Speaker 2: of examples. I just picked some cute ones.
Speaker 1: Wait, and here's a Latin question for you. Genera is
Speaker 1: plural of genus.
Speaker 2: Yes, yeah, apparently I looked this up because I didn't
Speaker 2: want to get it wrong. Apparently genuses is acceptable, but
Speaker 2: genera is what is preferred.
Speaker 1: Nice. Well, I like genuses because it sounds like geniuses.
Speaker 2: Yes, yeah, and then maybe people will like accidentally transfer
Speaker 2: that idea to us and they'll be like, oh, Daniel
Speaker 2: and Kelly are smart, because Kelly said genus genius.
Speaker 4: I saw, I tripped on it. That's ironic, all right.
Speaker 1: So one third of all animal genera have one species
Speaker 1: in them. What does that mean? What does that tell
Speaker 1: us about the history of evolution or anything?
Speaker 4: A lot of dead stuff out there. It could mean
Speaker 4: a lot of things.
Speaker 2: So it could mean that there's a lot of new
Speaker 2: like lineages out there, so things just haven't had a
Speaker 2: chance to split yet. It could mean that there's a
Speaker 2: lot of extinction out there, and there were groups out
Speaker 2: there that had a lot of relatives and then a
Speaker 2: lot of their relatives died and just one survived, like us.
Speaker 2: You know, there were a bunch of other Homo species,
Speaker 2: but only we survived. And that's sort of an interesting question.
Speaker 2: Is what is it that determines who the survivors are? Yeah,
Speaker 2: but yeah, it could be either of those things or
Speaker 2: some other things.
Speaker 1: Does that suggest like a history of bottlenecks where you know,
Speaker 1: diversity is crucial and only one species survives because they're different.
Speaker 2: I don't know if that necessarily suggests a bottleneck. I
Speaker 2: don't gosh, that's the first time I've heard the word
Speaker 2: bottleneck applied to groups of species instead of like a population.
Speaker 4: Yeah, I don't know.
Speaker 2: Yeah, maybe I guess maybe you've got something catastrophic that
Speaker 2: happens and it knocks out a bunch of different species,
Speaker 2: but one is that what you're saying?
Speaker 4: Yeah, uh, yeah, that would be worth thinking more about. Yeah,
Speaker 4: I don't know, So I don't know.
Speaker 2: If it's usually like the same catastrophe that wipes out
Speaker 2: a bunch of different species, but one like it could be,
Speaker 2: you know, habitat loss wipes out this Homo species and
Speaker 2: parasite wipes out another Homo species or something, and it's
Speaker 2: not like the same thing.
Speaker 4: But that's a good question. I don't know the answer.
Speaker 1: Well, in the case of some of these animals, do
Speaker 1: we have like fossils of other critters in the same
Speaker 1: genus that are no longer around so we know that
Speaker 1: it used to be broader?
Speaker 4: Yes, yeah, for a lot of these we do.
Speaker 1: Cool.
Speaker 2: Yeah. Yeah, for a lot of the examples that we
Speaker 2: went through earlier, we do, so they they were not
Speaker 2: alone in the past. So another question that bottleneck question
Speaker 2: was great, I'm gonna be that's like gonna be a
Speaker 2: keeping me up at night question. Okay, So then Jane's
Speaker 2: other question was what about genera with lots of species
Speaker 2: in them. And there are some megadiverse genera really yes,
Speaker 2: and so for plants there are some megadiverse genera. So
Speaker 2: for example, a Solanum. This is the genus that includes
Speaker 2: like potatoes, tomatoes, eggplants. Thank goodness for salanim It is
Speaker 2: a delicious genus.
Speaker 1: I think it's a genius genus.
Speaker 4: Yeah, me as well.
Speaker 2: And I think the genus Gosh, the genius genus Homo,
Speaker 2: has done amazing things with Solanum.
Speaker 4: If only I could have said that fast. All right.
Speaker 2: Another very diverse genus is a Bogonia. You may have
Speaker 2: heard of bogonia as they're kind of flower. There's a
Speaker 2: lot of them for animals, because that is specifically what
Speaker 2: Jane was asking about. There are two beetle genera that
Speaker 2: are very diverb beetles, the beetles Agrillis.
Speaker 4: These are jewel beetles.
Speaker 2: One that you might have heard of is the emerald
Speaker 2: ash borer, which is causing a bunch of trouble in
Speaker 2: the United States right now. And Stennis. These are semi
Speaker 2: aquatic robe beetles. So just another kind of beetle.
Speaker 1: Just another kind of beetle. Wow, myth amazing biodiversity and
Speaker 1: evolutionary genius, just like just another kind.
Speaker 2: Of beetle now, the coleopter and people are shaking their
Speaker 2: fists at me.
Speaker 4: I'm sorry.
Speaker 2: I love beetles. They are wonderful. They are wonderful. In
Speaker 2: terms of vertebrates, the pristamantis, there's over six hundred species
Speaker 2: of these.
Speaker 4: These are absolutely super cute little frogs.
Speaker 2: And then there are some like genera of geckos that
Speaker 2: also have a lot of species, and the noless lizards
Speaker 2: have a lot of species too. So when do you
Speaker 2: get a genus that has a lot of species? And Daniel,
Speaker 2: don't look at the outline, look at me. What do
Speaker 2: you think the answer is?
Speaker 1: When do you get a genius that? When do you
Speaker 1: get a genus that has a lot of species?
Speaker 4: It's a kelly answer, This is dKu. What do you
Speaker 4: think the answer is?
Speaker 1: It depends slash.
Speaker 4: We don't know that's right exactly. The answer is it depends.
Speaker 2: And so I found a paper that said for birds,
Speaker 2: it seems to me that you get a genus that
Speaker 2: has a ton of diversity when the birds disperse annually
Speaker 2: and are feeding generalists, so when they like eat everything
Speaker 2: and they are willing to disperse to different places, so
Speaker 2: maybe they're just like you know, filling a lot of
Speaker 2: different niches that way. But that kind of ecological stuff
Speaker 2: doesn't seem to matter as much for mullusks. For things
Speaker 2: like irises, it tends to be more abiotic stuff. And
Speaker 2: so by abiotic stuff, I mean stuff that's not living
Speaker 2: like you know, temperature, water availability, stuff like that. Geographic
Speaker 2: range seems to matter more or for things like Australian mammals. So,
Speaker 2: as far as I could tell, there's no like rule
Speaker 2: of thumb that works for everything. When you're trying to
Speaker 2: figure out what genus should have more species, it seems
Speaker 2: like it depends on what kind of group of organisms
Speaker 2: you're talking about. And of course you'll note I didn't
Speaker 2: even bother talking about bacteria, because yes, they probably represent
Speaker 2: more diversity than anything else.
Speaker 4: But who can wrap your head around those guys?
Speaker 1: Not me, I know.
Speaker 2: So Jane's last question was the most important one, right,
Speaker 2: does it have to do with parasites?
Speaker 1: Jane is just pandering now.
Speaker 2: And thank you, Jane, I appreciate it, and I hope
Speaker 2: you have an extraordinary twenty twenty six as well. But unfortunately,
Speaker 2: as far as I could tell, it doesn't have to
Speaker 2: do with parasites. But you know what, I'm guessing that's
Speaker 2: because no one's looked yet, and they should look harder.
Speaker 2: I'm guessing that the diversity of parasites, in terms of
Speaker 2: like what genus is of parasites have the most diversity.
Speaker 4: I didn't see papers on that.
Speaker 1: There's a research topic.
Speaker 2: That's yet there you go, and that probably has a
Speaker 2: lot to do with like, you know, how are their
Speaker 2: hosts diversifying? Like, if a host genus has a lot
Speaker 2: of diversity, probably parasite genuses you find in them also
Speaker 2: have a lot of diversity because they probably split with
Speaker 2: the hosts, And so maybe that's where you can find
Speaker 2: some like predictable trends and you know, good old predictable
Speaker 2: parasites as I always say, well, here.
Speaker 1: I have a parasite question for you. Is there an
Speaker 1: example of a parasite losing its host species, like the
Speaker 1: host goes extinct, but the parasite adapts and survives.
Speaker 2: Yeah, so I don't have an example off the top
Speaker 2: of my head, but I know that's called host switching.
Speaker 4: So it is a thing that happens.
Speaker 1: That's amazing.
Speaker 3: Yeah.
Speaker 2: Oh oh, oh, I have a sad example, guinea worm
Speaker 2: is a really awful parasite that goes from copopods to humans.
Speaker 2: So copapods are tiny little aquatic crustaceans, and they're like
Speaker 2: so small that you might not see them, but you
Speaker 2: might accidentally drink them in your water if you're living in,
Speaker 2: for example, certain places in Africa, and if you drink them.
Speaker 2: I believe they I wasn't prepared to talk about the
Speaker 2: life cycle do with the best I can. I think
Speaker 2: they find mates in your body, and then the pregnant female.
Speaker 4: The male dies. Who cares pregnant female. I'm just I'm
Speaker 4: just joking. No, I'm just joking. I'm joking. I like dudes.
Speaker 2: And so the pregnant female moves down towards like your
Speaker 2: ankle or some other part like your foot, and she
Speaker 2: sticks part of her rear end out of your body.
Speaker 2: It causes a horrible feeling that makes you want to
Speaker 2: stick your foot or your leg in cool water, and
Speaker 2: so you tend to put your foot in the water. Supply,
Speaker 2: when you do that, she releases her eggs into the
Speaker 2: water and then they get consumed by those little critters
Speaker 2: in the water we were talking about, and the cycle
Speaker 2: starts again. And so the way that we've tried to
Speaker 2: deal with this parasite is that you take something like
Speaker 2: a match stick and you slowly wind the parasite around
Speaker 2: the match stick, and every day you pull out just
Speaker 2: a little bit of the parasite and then you clamp
Speaker 2: it onto the match stick and you do it again
Speaker 2: the next day. This is a horribly painful thing, and
Speaker 2: it can get infected and it's just, you know, miserable.
Speaker 2: This is something that actually our species. You can you
Speaker 2: can read descriptions of this going back like thousands of
Speaker 2: years because their species has been dealing with this for
Speaker 2: a really long time and it's very distinctive. But if
Speaker 2: you break it, and by pulling it out too fast, yeah,
Speaker 2: it actually it's secreting something to control our immune system,
Speaker 2: and if you break it, your immune system will have
Speaker 2: a massive reaction to it, which is worse than you
Speaker 2: feel when you're slowly trying to pull it out. So
Speaker 2: the goal is to just pull it all out in
Speaker 2: one piece without killing it all.
Speaker 1: Right, But I was not asking what is the most
Speaker 1: horrific parasite, Please describe it in detail. I was asking
Speaker 1: about post switching.
Speaker 4: I'm getting there, I'm getting there, okay.
Speaker 2: So the Carter Foundation and a number of other different
Speaker 2: organizations have been going to all the different places where
Speaker 2: you find this parasite and they anywhere. The time they
Speaker 2: find a person who's infected, they bring them to a
Speaker 2: facility and they say, okay, we'll like support you for
Speaker 2: the duration of your infection and anytime your foot hurts,
Speaker 2: and like, you know, every day you'll come to us.
Speaker 2: You're gonna put your foot in cool bleach water so
Speaker 2: it'll kill the eggs or like, they've got some procedure
Speaker 2: where they like make sure that the eggs don't get
Speaker 2: back into the water. They help them, you know, wind
Speaker 2: out the parasite safely, and they are stopping the.
Speaker 4: Life cycle, okay.
Speaker 2: And so they've got it down to like zero cases
Speaker 2: in a lot of the countries where you used to
Speaker 2: find this parasite, and it was down to like one
Speaker 2: country where you were still finding it, and it was
Speaker 2: fourteen cases in one year and that was it. And
Speaker 2: then they started finding it in the dogs. So there
Speaker 2: was massive selection pressure for the parasite to be able
Speaker 2: to jump hosts because the humans were figuring out a
Speaker 2: solution around it, and maybe before sometimes it was infecting
Speaker 2: dogs and we just didn't know. But now they're starting
Speaker 2: to find it in dogs, and the dogs run wild
Speaker 2: and they go in and out of the water all
Speaker 2: the time, and so anyway, this could be a case
Speaker 2: of host switching.
Speaker 4: It's possible.
Speaker 2: Actually, this is a case where we didn't realize it
Speaker 2: was in the dogs before, and maybe I haven't actually
Speaker 2: answered your question. Anyway, we could do a whole episode
Speaker 2: on this if people are interested. This is like a
Speaker 2: really important case of humans trying to eradicate a parasite.
Speaker 2: Long answer host switching exists, that might be an example.
Speaker 4: Guinea worm is the worst?
Speaker 1: Interesting? Is that that's really the worst?
Speaker 4: My gosh.
Speaker 1: I'm so sorry Jane for accidentally including that description and
Speaker 1: the answer to her otherwise innocuous question.
Speaker 2: Okay, all right, here we go, Jane, thanks for asking
Speaker 2: about parasites at the end there.
Speaker 7: Thank you so much, Kelly for answering my question. I
Speaker 7: was surprised how quickly you got to murder and cannibalism, though,
Speaker 7: and delighted that you managed to shoehorn host switching into
Speaker 7: the answer, even though it didn't appear to be relevant.
Speaker 7: Happy to pander to your interests any day next time aliens.
Speaker 7: I was stunned to hear that we're not special in
Speaker 7: being home all alone to coin a phrase, and almost
Speaker 7: a third of species are the only example in their genera.
Speaker 7: I guess thinking about beetles makes us seem more unusual,
Speaker 7: although I wonder if it was just that the beetle
Speaker 7: and frog taxonomists were more restrained when taxonomizing, if that's
Speaker 7: a word. I'm glad that you find my accent charming, Daniel.
Speaker 7: I'll have to think of more questions to give you
Speaker 7: more chances to hear it. I do love the way
Speaker 7: Kelly says arbitrary, though, keep being extraordinary.
Speaker 6: Thank you.
Speaker 4: All right, and we are back.
Speaker 2: And man, Daniel, today is your day, man, because this
Speaker 2: is another alien's question. You stacked the deck, I think,
Speaker 2: and so let's go ahead and hear bra alien question.
Speaker 4: Daniel, is it your birthday?
Speaker 1: It's alien day?
Speaker 5: All right, hey, Daniel, and Kelly. Like Daniel, I'm fascinated
Speaker 5: by the idea of aliens and how they could differ
Speaker 5: from us, especially in regards to size. We are as
Speaker 5: big or small as our environment allows us to be,
Speaker 5: and pop culture has shown us a lot of fun
Speaker 5: depictions of the scale of different aliens. I guess the
Speaker 5: most egregious would be doctor Seuss's, who's living on a
Speaker 5: planet the size of a spec I know doctor Seuss
Speaker 5: isn't known for his realism. I think physics is going
Speaker 5: to call bs in that case. But it does get
Speaker 5: me thinking about what are the upper limits and lower
Speaker 5: limits of scale that physics will allow for intelligent life.
Speaker 1: Thanks so much for taking my question.
Speaker 2: Oh Daniel, if you were going to meet an alien,
Speaker 2: would you rather meet a big alien or a little
Speaker 2: alien or a medium alien like a Goldilocks alien.
Speaker 1: I think I'd really like to meet a super duper tiny,
Speaker 1: micro scopic alien because they might have a very different
Speaker 1: view of the universe and experience phenomenon different scales, and
Speaker 1: I have different ways of intuiting how it works and
Speaker 1: thinking about it. I think that might be super insightful.
Speaker 1: I'd love to meet quantum sized aliens.
Speaker 4: But wouldn't you be worried about like stepping on them?
Speaker 1: I'd be worried about being infected.
Speaker 4: By them, or like inhaling it accidentally, like I'm so sorry,
Speaker 4: or blacks.
Speaker 1: I read a great science fiction book once about aliens
Speaker 1: that come to Earth and basically just live on people. Yeah,
Speaker 1: it's called the Woman who Thought she was a planet.
Speaker 1: It's fantastic Vandanna saying she's actually a physicist who's now
Speaker 1: a science fiction author. Also great stuff.
Speaker 4: Cool.
Speaker 2: All right, Okay, so let's actually answer Brandon's question. I've
Speaker 2: done what I do and got us off track again.
Speaker 2: So how small could they get?
Speaker 1: Yeah? I love the branding is thinking about this, what
Speaker 1: are the limits of physics? And it's to do this
Speaker 1: because we want to understand what's realistic about aliens. You
Speaker 1: can't just fanticize by them being super tiny or being
Speaker 1: the size of a galaxy because they are limited by physics.
Speaker 1: But also we are limited in our imagination of what
Speaker 1: kinds of aliens might be out there. So today I'll
Speaker 1: give you a sense for what I think could be
Speaker 1: the smallest or the biggest aliens and what physics limits that.
Speaker 1: But you know, there could be lots of other ways
Speaker 1: of being alive and having brains and bodies that we're
Speaker 1: not being about today, So these are not absolute limits. Okay,
Speaker 1: So on the smaller end, I think we should assume
Speaker 1: that the teeny tiniest building blocks of life have to
Speaker 1: be atoms like we could dig deeper into quarks, but
Speaker 1: you know that makes very very complicated quarks can never
Speaker 1: be alone. So now we're talking about weird new particle
Speaker 1: physics that makes weird new structures of quarks. But if
Speaker 1: we just stick to atoms, that already gives us a
Speaker 1: pretty tight lower bound because atoms are a certain size, right,
Speaker 1: you really can't build something out of atoms that's smaller
Speaker 1: than like a tenth of a nanometer.
Speaker 4: I mean, that's pretty tiny.
Speaker 2: I guess I didn't imagine that we were even going
Speaker 2: to be working on the nanometer scale. But your imagination
Speaker 2: is vaster or tinier than mine, and.
Speaker 1: I think that's what sets the scale for life on Earth, right,
Speaker 1: like the smallest known life we have on Earth, or
Speaker 1: like bacteria or phages if you think about even smaller.
Speaker 1: But those things are like you know, a micrometer. It's
Speaker 1: harder to get much smaller than that. When you're building
Speaker 1: blocks are like order nanometer because you have to have
Speaker 1: like stable chemistry, you have to store information, you have
Speaker 1: to have a metabolism. You know, all this stuff requires
Speaker 1: a lot of complexity. You can't build life out of
Speaker 1: like three atoms, right, You need complicated stuff to support,
Speaker 1: even bacteria, And so that means that the smallest kind
Speaker 1: of life you can have is like a micrometer. And
Speaker 1: so it's fun to think about like Doctor Seuss and
Speaker 1: the Who's you know, a dust spec on our planet
Speaker 1: is like one to one hundred micrometers, and so if
Speaker 1: life has to be at least as big as a micrometer,
Speaker 1: then it's really hard to imagine having intelligent life and
Speaker 1: complex society on a dust spec because that life would
Speaker 1: have to be much smaller than the dust spec, much
Speaker 1: smaller than a micrometer. And already we're hitting the minimum
Speaker 1: size for simple life bacteria, not to mention like intelligent
Speaker 1: life and complex society and all sorts of information processing
Speaker 1: in their brains.
Speaker 2: Okay, and as soon as you're getting into intelligence, you
Speaker 2: require more equipment and more size.
Speaker 4: Is that what you're.
Speaker 1: Yeah, Intelligence requires like memory and more information processing, communication
Speaker 1: ability between the members of the species. You know, for example,
Speaker 1: the human brain has like ten to the eleven neurons
Speaker 1: in it, so you're probably not getting intelligent life out
Speaker 1: of like six or seven building blocks. And even our ais, right,
Speaker 1: if you want to build synthetic life, those things have
Speaker 1: millions and millions of billions of parameters, which means you
Speaker 1: have a very large number of artificial neurons in that
Speaker 1: neural network. So a lot of complexity is required for
Speaker 1: real intelligence. So if you have a bunch of neurons
Speaker 1: all together, and you have a minimum size for like
Speaker 1: the basic building block, that gives you an estimate of
Speaker 1: like maybe a millimeter is the minimum size for really
Speaker 1: complex behavior. And you know, here on Earth we have
Speaker 1: critters that are like a millimeter. You know, insects, for example,
Speaker 1: order a millimeter, and those don't individually show a whole
Speaker 1: lot of intelligence. There's some learning there. Fruitflies, for example,
Speaker 1: have like you know, one hundred thousand or one hundred
Speaker 1: and fifty thousand neurons in them, and they don't show
Speaker 1: a whole lot of really complex intelligent behavior. They can learn,
Speaker 1: they can dance, they can sing to each other. It's fascinating. Actually,
Speaker 1: they just mapped the entire connectum of a fruitfly brain
Speaker 1: for the first time. Really super cool. So now they
Speaker 1: try to understand what does the fruit fly thinking, and
Speaker 1: how does that brain work and all sorts of stuff.
Speaker 1: Really cool bit of science done by a good friend
Speaker 1: of mine at Princeton. Cool so that's a good reason
Speaker 1: to think that, Like, you've got to be at least
Speaker 1: a millimeter probably in order to be intelligent. And even
Speaker 1: still at that scale, you got a lot of physics
Speaker 1: to worry about, not just like what's the smallest building
Speaker 1: block you can make these things out of, but like
Speaker 1: how do small systems operate? Because small systems have issues
Speaker 1: that big systems don't have, mostly having to do with noise.
Speaker 1: Oh like what, well, small things wiggle a lot. If
Speaker 1: you're man out of a smaller number of atoms, you're
Speaker 1: closer to like the vibration of those atoms. Okay, small
Speaker 1: things just have more thermal noise. Thermal noise just means
Speaker 1: related to the temperature, because remember, the warmer you are,
Speaker 1: the more the stuff inside of you is jiggling. That's
Speaker 1: what temperature is. And so the smaller you are, the
Speaker 1: closer you are to that jiggling. If you're big, you
Speaker 1: may I have huge concrete blocks. Then that jiggling all
Speaker 1: averages down it doesn't really affect you. But if you're
Speaker 1: a really small system, then you're going to be affected
Speaker 1: by that thermal noise and it can drown out any signals.
Speaker 1: This is one reason why, for example, our brains are
Speaker 1: the size they are. You might wonder, like, boy, childbirth
Speaker 1: is dangerous. Lots of women in history have died in childbirth.
Speaker 1: That's bad. Why didn't we select for denser brains, smaller
Speaker 1: neurons that could have the same intelligence at a smaller scale.
Speaker 1: And the answer is that if you make our neurons
Speaker 1: much smaller, then you're closer to the thermal noise, and
Speaker 1: so you lose intelligence. So there's the thought that we're
Speaker 1: sort of at the sweet spot, right the smallest brain
Speaker 1: you could have to have this much intelligence, and so
Speaker 1: you know, you really can't get too small and still
Speaker 1: have complex systems that don't get drowned in noise.
Speaker 4: Interesting, I didn't know that.
Speaker 1: Yeah, And so I would say that the smallest life
Speaker 1: you could have when building out of atoms is probably
Speaker 1: microbial life. Is it possible for microbes to be intelligent? Maybe?
Speaker 1: Possibly networks on microbes, but it's tough. Insect level intelligence.
Speaker 1: Millimeter scale intelligence also possible, but tough. So I think,
Speaker 1: you know, the smallest size critter you could expect to
Speaker 1: be intelligent at the human level is probably about the
Speaker 1: size of a human.
Speaker 4: Really.
Speaker 2: I mean, so we've ruled out insect size, But why
Speaker 2: couldn't you have like a brilliant dog, And like, yes,
Speaker 2: we have good good boys and good girls who are
Speaker 2: very smart and do good jobs.
Speaker 1: But like, oh, man, Kelly, I'm doing this at the
Speaker 1: physics level, which means, you know, factors of two or
Speaker 1: five whatever, So I'm gripping dogs in with humans. Oh okay, okay,
Speaker 1: you know, are we talking meter size or centimeter size
Speaker 1: or melimeter size? So I think a meter sized alien
Speaker 1: is probably the smallest you could imagine having human sized intelligence.
Speaker 4: Okay, perfect, All right, let's move on to upper limits.
Speaker 1: So when you get bigger in three dimensions, then you
Speaker 1: suffer from the square cube law. This very basic fact
Speaker 1: in physics that as you get bigger, your volume grows
Speaker 1: with your size cubed, right, which means your mass grows
Speaker 1: with your size cubed. But your strength the muscles and
Speaker 1: bones depend on the cross sectional area, and that tends
Speaker 1: to grow with the size squared. Just imagine a cube.
Speaker 1: You make it twice as long on each side, and
Speaker 1: then it's gonna have eight times as much stuff in it, right,
Speaker 1: But each side is only going to be four times
Speaker 1: as big as the original cube. So they gives you
Speaker 1: a sense for like how the internals grow faster than
Speaker 1: the sides. And this is one reason why, for example,
Speaker 1: there's a limit to the size of a building you
Speaker 1: can build because if you build a building larger, then
Speaker 1: it gets really high volume, but the side doesn't get
Speaker 1: much bigger. And so now like pressure on the side
Speaker 1: of a building grows because you have like this same
Speaker 1: amount of force on a smaller area proportionally, and this
Speaker 1: is also an issue for animals. You try to scale
Speaker 1: up an animal, then its volume grows faster than its strength,
Speaker 1: than the strength of its bones and its muscles, which
Speaker 1: depend on like the cross sectional area. They're not the volume.
Speaker 1: And so that's why, for example, elephants are not as
Speaker 1: proportionately strong as ants are relative to their weight.
Speaker 4: You know what I'm wondering.
Speaker 2: So you know, we've got like we've got elephants and
Speaker 2: they're really big, but why don't we and you know
Speaker 2: we used to have t rex and Elisaurus and all
Speaker 2: of those other like really big land animals. Yeah, but
Speaker 2: we have fewer of them now. Maybe we need to
Speaker 2: get Steve Brusatti on it. Tell us why we have
Speaker 2: fewer massive animals now? Because there's you know, there's always
Speaker 2: been this constraint. Oh, it's probably because we killed them,
Speaker 2: dang it. Oh man, we're coming back to that.
Speaker 1: We didn't kill all the dinosaurs though the asteroid did
Speaker 1: that for us.
Speaker 4: Well.
Speaker 2: No, but there was like giant lands. You know, there
Speaker 2: were a bunch of homo species and then there were
Speaker 2: like giant landslots, and then there were all these giant birds,
Speaker 2: and then humans went around killing the giant landers.
Speaker 1: But none of those were as big as Brontosaurus.
Speaker 4: No, that's a good point. That's good. Yeah, yeah, yeah. Wow.
Speaker 2: Anyway, we just gotta have Steve Brustani on a lot anyway,
Speaker 2: because he's a lot of fun.
Speaker 4: All right, go ahead, Sorry.
Speaker 1: But yeah, there are constraints there. Getting bigger is harder
Speaker 1: because you need really big muscles, you need really big bones.
Speaker 1: The bones proportionally have to grow faster than everything else
Speaker 1: in order to keep up with the volume. Also, it
Speaker 1: makes dissipating heat hard because you have less surface area
Speaker 1: per volume. And all this depends on the gravity. Right,
Speaker 1: The more gravity you have on the planet, the faster
Speaker 1: this constraint comes into play. The less gravity you have,
Speaker 1: the slower you can have bigger animals on a lower
Speaker 1: gravity planet. And in the same way, if you're in
Speaker 1: the ocean, you can escape some of this because the
Speaker 1: water helps support some of the weight. You have better cooling.
Speaker 1: That's why, for example, the biggest critters ever are in
Speaker 1: the ocean.
Speaker 4: And the biggest creaters ever are alive right now. Pretty
Speaker 4: cool that we're.
Speaker 1: Alive the same time and we didn't kill them all
Speaker 1: yey for us yet.
Speaker 2: Yeah, that's another fact I learned from Steve Brussati. Anyway, sorry,
Speaker 2: go ahead, very exciting.
Speaker 1: But there's also a limit to how big you can get,
Speaker 1: even if you're in the water, because the bigger you get,
Speaker 1: the slower you can think. Signals move across your brain
Speaker 1: at a certain speed. It's like one hundred meters per second,
Speaker 1: not light speed, and so coordination across your body becomes difficult.
Speaker 1: Right now, your brain knows about how long it takes
Speaker 1: signals to travel from your toes or from your nose,
Speaker 1: and it coordinates that. Right somebody touches you at the
Speaker 1: same time on your toe and on your nose. Your
Speaker 1: brain knows that the signals should arrive at different times,
Speaker 1: and it'll figure that out of the reverse engineer that
Speaker 1: but if you're like a kilometer size being, then that
Speaker 1: coordination is going to take a lot of time, seconds
Speaker 1: or even minutes. It's hard to imagine having like a
Speaker 1: unified consciousness in that pick sure, and your thoughts are
Speaker 1: gonna just be slower. You know, if you have a
Speaker 1: creator of the size of the solar system, you know,
Speaker 1: made out of dark matter or something really creative, it's
Speaker 1: gonna think super duper slow. It's going to be really
Speaker 1: hard to communicate with those aliens, you know, And.
Speaker 2: Do you feel you feel certain about like about that?
Speaker 2: There's like no way around it. Are you telling us
Speaker 2: like a truth of the universe or is this a
Speaker 2: like this is how you'd set up your sci fi
Speaker 2: fiction book because you're pretty darn sure about it.
Speaker 1: This is all based on a lot of assumptions about
Speaker 1: how biology works, which is inspired by how things work
Speaker 1: here on Earth, and aliens could circumvent a lot of this.
Speaker 1: Like our nerve signals travel at one hundred meters per second,
Speaker 1: you could definitely do that faster, right. The ultimate limit
Speaker 1: is light speed, which is a lot faster than one
Speaker 1: hundred meters per second, So you could get bigger if
Speaker 1: you had faster signals. Right, that's for sure. If you
Speaker 1: had different chemistry, if you had different information storage, you
Speaker 1: could do all sorts of things different. I mean, if
Speaker 1: things were like not biological at all, We're talking about
Speaker 1: machine intelligence or made out of crystals or plasma or something,
Speaker 1: then everything could be very, very different. But I'm trying
Speaker 1: to extrapolate from Earth life biology, but you know that's
Speaker 1: always limited as an equals one.
Speaker 4: Yep, Okay, cool.
Speaker 1: But the good news is that all of this suggests
Speaker 1: that intelligence on Earth is kind of in the sweet spot.
Speaker 1: We're big enough to have complex brains that avoid the noise,
Speaker 1: but we're small enough to be able to communicate across
Speaker 1: our bodies pretty quickly and have like coordinated actions and intelligence.
Speaker 1: So yeah, humans are pretty awesome.
Speaker 4: Oh man, I love that we decided that we're the
Speaker 4: best go us.
Speaker 1: In this episode, we went from humans are the worst
Speaker 1: to humans are the best and back again.
Speaker 2: Well, you know, we cover a broad range of emotions
Speaker 2: and a broad range of topics on this show.
Speaker 4: We've got it all.
Speaker 1: All right, let's send this answer to Brandon and see
Speaker 1: if we scratched his itch.
Speaker 5: Thank you for taking the time to put such thought
Speaker 5: into answering my chilly question. Of course, pop culture will
Speaker 5: take liberties to imagine intelligent life forms, ranging from Marvel's
Speaker 5: Galactus to Doctor Seus's Whovill, and Daniel is always reminding
Speaker 5: us that our human and earthly context limits our ability
Speaker 5: to imagine just how truly alien aliens could be. But
Speaker 5: it's fascinating to know that scientifically, the most likely scenario
Speaker 5: is that any beings we encounter someday will roughly be
Speaker 5: on scale with humans. Thanks again, and now I will
Speaker 5: not pull a hort in the elephant and start searching
Speaker 5: for random clovers to seek out microscopic intelligent life.
Speaker 2: Well, thank you so much for sending your questions and
Speaker 2: your curiosity to us. We absolutely adore getting to interact
Speaker 2: with you all.
Speaker 1: We really do. Your curiosity powers this podcast, and it
Speaker 1: also powers all of science. So keep thinking, keep wondering,
Speaker 1: keep demanding that the universe makes sense to you.
Speaker 2: And keep writing us at questions at Danielandkelly dot org.
Speaker 4: Until next time, see you later.
Speaker 1: Thanks everybody for listening. Please go and do us a
Speaker 1: favor and rate the show on whatever podcast app you're using.
Speaker 1: It really helps people.
Speaker 2: Find us Daniel and Kelly's Extraordinary Universe. Is edited by
Speaker 2: the amazing Matt Kesselman.
Speaker 1: He really is a wizard. You can also find us
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Speaker 1: Come engage with us.
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Speaker 2: We really do want to hear from you, and you.
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Speaker 1: where you'll also find an invitation to join our discord
Speaker 1: where everybody comes and talks about the amazing universe.
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