Listener Questions #38

Daniel and Kelly answer questions about aliens watching Earth, about lone species, and about the size limits of intelligence. See omnystudio.com/listener https://omnystudio.com/listener for privacy information.

Speaker names marked ? are inferred from speaking time and the show’s known hosts — they are not voice-verified.

• 0:00Daniel Whiteson?

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• 1:43Daniel Whiteson?

  If telescopes looked back from afar, what signs of Earth would glow? Would life in air and seas be something it could know?

• 1:52Kelly Weinersmith?

  As sole survivors in the genus Homo, we've taken the throne. But are there other genera where a species is similarly alone?

• 2:02Daniel Whiteson?

  From the tiniest speck to giants tall, how small or big can thinkers be at all?

• 2:09Kelly Weinersmith?

  Hmm, uh, what do I, what do I say next?

• 2:13Daniel Whiteson?

  What was that?

• 2:18Kelly Weinersmith?

  Whatever questions keep you up at night, Daniel and Kelly's answers will make it right.

• 2:24Daniel Whiteson?

  Welcome to Daniel and Kelly's extraordinary universe listener questions number 38.

• 2:30Kelly Weinersmith?

  Whoop whoop.

• 2:43Kelly Weinersmith?

  Hello, I'm Kelly Wiener Smith. I study parasites and space, and it's an exciting week to be someone who studies space.

• 2:52Kelly Weinersmith?

  Do you know why, Daniel?

• 2:54Daniel Whiteson?

  Hi, I'm Daniel. I study aliens and physics. And yes, I'm aware of the Artemis launch because I do not live underground.

• 3:03Kelly Weinersmith?

  Well, okay, but so here's the thing, right? Okay, so I, you know, of course I was watching the Artemis launch and I was watching it when my daughter got off the bus and got home from school. And she came home and she's like, what are you watching? And I was like, I'm watching the humans that are going back to the moon. And she goes, what? And so I, you know, I haven't been.

• 3:21Daniel Whiteson?

  She didn't know?

• 3:22Kelly Weinersmith?

  No, and so I don't think that the kids are like talking about this. Like, I don't think that like this generation is very excited about the fact that we're sending people back to the moon. What's your sense?

• 3:35Daniel Whiteson?

  That's a great question. And, you know, I just realized now that I don't think I've discussed it with my kids at all. I just sort of watched it myself and I have no idea if they know anything about it. Hold on, let's find out.

• 3:48Kelly Weinersmith?

  Okay.

• 3:53Kelly Weinersmith?

  Isn't she supposed to be at school right now?

• 3:56Daniel Whiteson?

  Hi Hazel, did you know that we just sent astronauts back to the moon?

• 4:01Speaker 06

  Yeah, Artemis 2, right?

• 4:03Daniel Whiteson?

  You know about Artemis?

• 4:04Speaker 06

  Wait, am I on the podcast?

• 4:05Daniel Whiteson?

  Yes, live. And do you think it's cool or whatever?

• 4:09Speaker 06

  I think it's interesting, but I probably wouldn't spend very much time thinking about it.

• 4:12Daniel Whiteson?

  Cool. All right. Thank you. Have a good day.

• 4:14Speaker 06

  Okay, thanks. Bye.

• 4:16Kelly Weinersmith?

  Oh, that's a disappointing answer.

• 4:21Kelly Weinersmith?

  Yeah, for all the money that was spent on it. Yeah, I mean, Ada, Ada was excited. And then we, so you know, we watched, she sat with me, we watched the launch. And then we sat for a while and we were watching the, the like live feed. And she was like, well, when do we get to see like the astronauts? And I was like, I guess they're not going to show you the inside. So like, you know, they were doing, they've got to go around Earth a couple of times before they leave, you know, the orbits of Earth to head to the moon. And I guess they decided they weren't going to show the astronauts on the inside because they were, you know, doing multiple tasks or whatever. But Ada was really bummed. She's like, well, I want to see what they look like.

• 4:59Daniel Whiteson?

  What it's like for them. And then imagine herself in that ship, probably.

• 5:03Kelly Weinersmith?

  Yeah, yeah. And so not only had she not heard about it, but then she really didn't get to see the people at all. And the next day she didn't ask, is there any news about the astronauts? And I know they're not landing, but I think the kids are already sort of not super excited about it.

• 5:19Daniel Whiteson?

  Well, let me ask you, what aspect of it is very cool for you? Which part is getting you excited?

• 5:25Kelly Weinersmith?

  Well, so I'm hoping that we will start doing more consistent research, like we'll set up a research station and then we will, we'll have like long-term research programs on the moon.

• 5:36Daniel Whiteson?

  So that we can learn about like life in low gravity and space and radiation and all the kind of stuff you guys recommended in your book that we need to do to be serious about settling space.

• 5:45Kelly Weinersmith?

  Yeah, I'm hoping we do all of that stuff now, but you know, that would be really expensive. And so that would require us to do something very different than what we did last time, which was just go to beat the Soviets and then go home because we had done it. And so, you know, if we're just going to show the Chinese that we can do it again. Just to beat them before they try to do it. And then we stop, then it will be sort of anticlimactic and like, oh, all right. We spent a bunch of money to prove we could do it again, and now we're gonna stop. Meh. But I don't know, what about you? Are you, are you excited? And if so, why?

• 6:17Daniel Whiteson?

  Well, that's just so like thoughtful and future thinking. Is there a part of you that just feels like a visceral excitement? Like, big rocket, go boom. You know, or like, people are in space, you know, just the immediacy of that. Isn't that cool?

• 6:30Kelly Weinersmith?

  That is cool. I'm glad the big rocket didn't go boom. That's what I was, I was worried about that. I wanted big rocket not go boom. But, uh, no, I mean, I thought that was cool. And like, but I, I also think it's cool just when we get a satellite into space without the rocket going boom. Like, it's very easy to get me excited about space stuff. But yeah, yeah, I think it's cool that we've got humans going to the moon again.

• 6:53Daniel Whiteson?

  I'm always excited about like, things go into space. That's very cool. Every Falcon launch or whatever, I think it's pretty fun. This mission in particular, I'm like, not sure what we're learning or what we're doing. We haven't done before. So it's also exciting in the like sense that things are starting again. We're exploring, we're working towards something in the future. So a lot of the excitement for me also comes from the promise of what this might mean.

• 7:17Kelly Weinersmith?

  If we go to the moon, touch our feet down on the moon and we don't stay this time, I will be bummed that we didn't spend that money on things like an exploratory mission to Europa or something like that. Like, we could have explored, used robots to explore other stuff and gotten more data. And like, cause you know, robots can do more than humans can. And so if we spent all this money to get humans to the moon and then we don't figure out a way to stay there, I'll be bummed. Anyway, hopefully this time we'll stay and we'll do more research and get the data. But anyway, we'll have to wait and see, but I'm glad the rocket did not go boom.

• 7:51Daniel Whiteson?

  Yep, and good luck to all the astronauts.

• 7:54Kelly Weinersmith?

  Yes, right. And oh, yeah, and you know, I am excited that we have a woman in space. We have a black man in space and we have a Canadian in space. And so, uh, those are all exciting things to me. So I am excited about those firsts. I mean, there have been Canadians in space before, but yeah, not to the moon, you know? So, hooray.

• 8:13Daniel Whiteson?

  And I'm excited to be answering questions from our listeners today because one of the exciting things about space is the sense of exploration, pushing back on what we don't know. And that's exactly what we're trying to do here on the podcast is to dive deep into your curiosity and push back what you don't understand to broaden your mental picture of the universe.

• 8:34Kelly Weinersmith?

  Friends, if Daniel wasn't here, we would never get to the point. So thank goodness we have Daniel to keep us on track. And so let's go ahead and get to Jonas's question about space telescopes.

• 8:45Speaker 07

  Hi, Daniel. Hi, Kelly. My question came to mind some time ago, back when the James Webb Telescope was a big topic in the media and in podcasts like yours. If it were pointed at Earth from the distance of the nearest Earth-like exoplanet, what could it actually detect? How would Earth's appearance be shaped by its physical properties? And could any biological signatures such as signs of life in the atmosphere realistically be inferred? Many thanks for exploring this question.

• 9:16Kelly Weinersmith?

  This is a fantastic question that I don't know the answer to.

• 9:20Daniel Whiteson?

  It's a very cool question because he's putting himself in the minds of aliens and wondering if there are aliens out there that are similar to us, could they see us? Right? It's a great question because obviously we haven't seen any aliens yet. And so he's wondering if the reverse is true. Maybe aliens will discover us before we discover them. But it's also a good way to understand what we could possibly see with our technology.

• 9:45Kelly Weinersmith?

  Yes. And so of course you would love someone who is thinking like an alien or thinking about aliens. And so let's go ahead and talk about what telescopes can see.

• 9:54Daniel Whiteson?

  Yeah, I think there's a lot of misconception about what telescopes actually do. And people imagine that really powerful telescopes could maybe like show you what's happening on the surface of an exoplanet or something. But telescopes are really good at seeing distant, dim, huge things. They're not very good at seeing small things that are far away, which is what Jonas is hoping that they could see. And the reason is a little bit of physics, which is important to understand telescopes, which is the diffraction limit.

• 10:24Kelly Weinersmith?

  And so you're saying Earth would be a small thing. So what would be a big thing? Like the sun? Or are we talking about like entire solar systems or entire galaxies? What counts as big?

• 10:32Daniel Whiteson?

  Yeah, galaxies are big. And that's why when we point James Webb Telescope into the distant cosmos, the kind of things we're seeing are entire galaxies because they're big.

• 10:43Kelly Weinersmith?

  Okay.

• 10:43Daniel Whiteson?

  Right? They take up enough of the sky that we can resolve them. We can see them.

• 10:49Kelly Weinersmith?

  Back to diffraction. I got you off track. That's what I do. You get us back on. Okay.

• 10:53Daniel Whiteson?

  Essentially, there's a minimum pixel size in the sky that telescopes can resolve. And the reason is that light at this scale acts like a wave. If light was just made of tiny little geometrical particles, little balls with perfect resolution, then you wouldn't have this effect. But when light enters the telescope, it goes through an aperture, right? This is the opening in the telescope that gathers the light. And anytime a wave goes through a hole or through any sort of opening, you can model it like a series of sources across that opening. This is sort of like the granddaddy version of interference. Right? If you have, for example, two sources of light, then in some places, those two sources of light will line up to be brighter.

• 11:38Daniel Whiteson?

  And in other places, they will light up to cancel out. Right? Because waves go up and down and up and down. And if the up from one wave hits the down from the other wave, they cancel out. And if the up hits the up, then they add to each other. Right? So that's interference.

• 11:51Kelly Weinersmith?

  Okay.

• 11:52Daniel Whiteson?

  So if you have two sources of light, then you get like an interference pattern across the screen. Right? Well, when light comes through an opening, you can model that as a bunch of sources across the opening.

• 12:03Kelly Weinersmith?

  Okay. And so some will interfere?

• 12:05Daniel Whiteson?

  And so, exactly. You get interference between all of those. And so you can't have an opening. You can't have an aperture. You can't gather light without getting some interference. It's impossible to avoid interference. This is the process we call diffraction.

• 12:19Kelly Weinersmith?

  Okay.

• 12:20Daniel Whiteson?

  Anytime light passes through an opening, you get interference among itself because the light that comes out of the opening is just like as if you had a series of sources across that opening.

• 12:30Kelly Weinersmith?

  Okay.

• 12:30Daniel Whiteson?

  And so any optical system, even if you have perfect optics with no aberration or anything like that, you're going to get interference because you have an aperture. And that causes fuzziness, right? And so essentially, you can't resolve things that are really, really small. And the size of the effective resolution, the size of a pixel on the sky, depends on the size of your aperture and the wavelength of light that you're gathering. And so for various wavelengths and various sizes of your telescope, you can resolve a pixel in the sky of various sizes. So the human pupil has an aperture that's like a few millimeters across.

• 13:10Daniel Whiteson?

  And so its diffraction limited resolution for like visible light is like 10 or 20 arc seconds. And Hubble is like two and a half meters across. And so its diffraction limited resolution is like 0.1 arc seconds, right? So much, much smaller. So the pixels you get with Hubble are much smaller in the sky than the pixels you get from the naked eye, because it has a bigger aperture. And James Webb is like six and a half meters wide, so it's even better. But still, these pixels are too big to see like the surface of an exoplanet. You're never gonna like spy on an alien having dinner on an exoplanet,

• 13:51Daniel Whiteson?

  because the size of that alien dinner in our sky is much, much smaller than anything we can resolve. So what these telescopes are good at is accumulating a bunch of photons from dim things that are huge, big enough to see in our sky, but too dim to make out with the naked eye. So you can just point the telescope at them for a long time, and then you can gather enough photons so that it then appears. A great example is like Andromeda. Andromeda is really big. It's a huge galaxy. It's actually quite large in the sky. It's bigger than a full moon. But you can't see it with the naked eye because it's too dim. But you point a telescope at it and gather it for a while,

• 14:34Daniel Whiteson?

  you can get a really nice picture of Andromeda, because it's big, much bigger than diffraction limited resolution, and just too dim for your eye to make out, so your telescope can accumulate enough photons to get an image of it.

• 14:48Kelly Weinersmith?

  Okay, so the good news is that the telescopes save us from ourselves. We can't be creepy and spy on the aliens in great detail.

• 14:55Daniel Whiteson?

  That's not good news. No, we want to be creepy and spy on the aliens.

• 14:59Kelly Weinersmith?

  Oh, okay, okay. But what can we learn about the aliens? Can we learn if they are there or not? Like, can we detect life or not?

• 15:08Daniel Whiteson?

  So currently with like JWST, a distant Earth from a nearby exoplanet would just be a pixel. Right? Okay. You see that one pixel. Now with future telescopes, maybe we could see more. Right. But to have a resolution like spy on the surface of the planet, you'd need an aperture like the size of the sun.

• 15:28Kelly Weinersmith?

  Wow.

• 15:29Daniel Whiteson?

  All right, we're talking about a telescope the size of the sun, and that's possible. You can actually use the sun and its gravity to bend light and focus it into a collector. So you could use the whole solar system as a telescope. That's like really an idea we could pull off one day. And you could use that to look at aliens having dinner. But currently, that whole alien planet would be a pixel. That doesn't mean that you couldn't learn anything about it, right? It would be a super interesting pixel. Because if you think, oh, it's just one pixel, it's just one piece of information. But there's a lot of information in two different dimensions there. There's how the pixel varies with time and also how the brightness of the pixel varies versus wavelength. Right? One pixel means contributions from lots of different frequencies of light.

• 16:15Daniel Whiteson?

  Is it red? Is it blue? Are there greens in there? We can tell a lot from how the light varies with time and how the light varies with frequency.

• 16:23Kelly Weinersmith?

  Okay, what can we tell?

• 16:25Daniel Whiteson?

  So Earth emits in two major ways. Number one is it glows just because it has a temperature. Right? Like Earth is pretty cool and everything in the universe that has a temperature glows. And so you can tell the temperature of Earth by the frequency at which it glows. Like you take that pixel and you pass it through a prism and you can see which colors of light come out. And from the various frequencies of light, you can see the black body radiation of Earth. And you can use that to deduce the surface temperature of Earth from a distance.

• 16:56Kelly Weinersmith?

  Cool.

• 16:56Daniel Whiteson?

  Right?

• 16:57Kelly Weinersmith?

  Okay.

• 16:57Daniel Whiteson?

  Very cool. And so you can tell, oh, the earth is approximately what we call room temperature. Or maybe it's not. Maybe it's covered in magma and it's super hot, or it's an ice ball, right? So you can learn something about the temperature of the earth. The earth also reflects a lot of sunlight. So it's two major emissions. There's black body radiation from the temperature of the earth and there's reflection of sunlight. And reflection mostly happens when you have oceans and when you have clouds. So you can tell, hey, is it cloudy on that planet? Or is it a water planet, right? So you can get a sense for the cloud cover. You can get a sense for the water cover of this planet just from this one pixel, right? And the reason we developed all these techniques is because nobody's satisfied just seeing a pixel. They want to know more.

• 17:42Daniel Whiteson?

  And this is what scientists do, right? They learn how to extract as much information about the universe as possible from the data they got. They're not just going to say like, well, let's just wait 30 years and build that sun sized telescope. Like, no, we're here today. We want answer now, right? I love the ingenuity of scientists to extract this information from whatever tiny data they have.

• 18:04Kelly Weinersmith?

  Totally. Yeah. Because you're not getting funding for that sun telescope, probably. Kelly, the wet blanket is here to say. But so, okay, so if you know temperature and that there's water, you can maybe guess if there could be some sort of alien, maybe it's alien bacteria. But now you've got like a hunch about whether or not those aliens eat dinner.

• 18:25Daniel Whiteson?

  You can do even better than that. You can learn what the atmosphere is made out of. And if there are biomarkers in the atmosphere, right? So again, we just still have one pixel, but we can do clever things like wait for sunrise on the planet. During sunrise, that alien star shines through the atmosphere of the planet. And then those photons come to earth. And because those photons have gone through the atmosphere and atmospheres tend to absorb at certain frequencies based on their composition, we can tell what's in the atmosphere. So there will be absorption lines in that spectrum. There will be gaps that tell you what molecules are in the atmosphere because those molecules ate some.

• 19:07Daniel Whiteson?

  And by seeing which ones they gobbled, we can tell what's there. So like, is there water in the atmosphere? Is there ozone in the atmosphere? Is there methane? Is there CO2? Wow. Some of these things are very strong biomarkers because they're in chemical disequilibrium. Like, for example, oxygen is produced by photosynthesis, methane typically produced by biology, though there are geological sources. But if you have them both in the atmosphere, they tend to react and disappear. So if you see oxygen and methane in the atmosphere of an exoplanet, that means that there is a constant replenishment of those things. There's something

• 19:46Daniel Whiteson?

  on that planet making oxygen, making methane. Neither of these things are smoking gun proof of alien life, but they're like, you know, good, strong hints. Something out there is pumping out oxygen. So that's the kind of thing you can see, again, just from this pixel, right? Super cool. I was reading a really cool paper yesterday about how you can watch the transit, the eclipse, to learn more about the atmosphere. Remember that sometimes the way you discover these exoplanets is by seeing them cross in front of their sun and dim the light of the sun just a little bit, right? But the cool thing is that you can look at that dimming in various frequencies, right? You can say, well, does red light dim? Does blue light dim? Does

• 20:30Daniel Whiteson?

  green light dim? And that's another way to tell what's in the atmosphere, because the width of the eclipse and the depth of the eclipse will depend on what's in the atmosphere. So for example, if you're watching Earth pass in front of the sun and you're looking at a frequency that nitrogen likes to absorb, then the Earth is going to seem wider because now you're including the atmosphere. And in other frequencies where nitrogen is transparent and the Earth is opaque, the Earth is going to seem smaller, right? So it's like, is the eclipse including the atmosphere or not? Is a frequency dependent answer. So by looking at different frequencies, you can help determine, oh, what's this atmosphere mostly made out of? Really clever stuff.

• 21:14Kelly Weinersmith?

  All right. Yeah, you've got me. I'm amazed. All of this from a pixel? That's, that's pretty impressive.

• 21:18Daniel Whiteson?

  We're not even done yet, right? Now we got to think about time variation because as time goes on, the earth is spinning. So the sun reflecting off the earth will change based on where are the clouds, where are the oceans? And somebody actually did a study answering this exact question. They said, if we were in the next star system and we looked at earth and we watched the variation of the reflection of sunlight off of the earth, could we make a map of the earth? And so you can look this up. It's amazing. It roughly maps out what the earth continents look like. I mean, it's very, very pixelated. It's basically just like bands, but it shows you, oh, there's a bunch of land, then there's a really big ocean, then there's another

• 22:00Daniel Whiteson?

  little bit of land, then there's a smaller ocean. So you see the Pacific, you see the Atlantic, you see the Americas, you see Eurasia and Africa. Like, again, not in great resolution, but much more than zero information. Super duper cool. It's very cool.

• 22:15Kelly Weinersmith?

  That's amazing. Yeah. So cool. And that, and that would be with the kind of stuff that James Webb Space Telescope is seeing. You can get all that information.

• 22:24Daniel Whiteson?

  Exactly.

• 22:24Kelly Weinersmith?

  Okay.

• 22:24Daniel Whiteson?

  Exactly.

• 22:25Kelly Weinersmith?

  Wow.

• 22:26Daniel Whiteson?

  But James Webb Space Telescope is not the best way to do this, right? What you want to do when you're looking for exoplanets is you want to block the light from the sun because these planets are like 2 billion times fainter than the star. So it's like you're looking at a firefly next to a street lamp, you know, across the country. So it's very, very hard to do. And the right way to do that is to block the light from the street lamp. You can't just put like a circular shade to block the starlight because there's this weird interference effect where you end up having a bright dot at the center of that circle. We talked about this once when we were talking about the history of discoveries, a really cool story about the Poisson spot. Anyway, they have a new generation of space telescopes they're

• 23:08Daniel Whiteson?

  building that have a complicated shaped star shield to avoid this sort of interference effect. And those are going to be awesome at seeing these exoplanets. Really, we need a dedicated device with sensitivity at the right frequency and with one of these star shields. So, you know, in the next couple of decades, we're going to be seeing a lot more information about these exoplanets.

• 23:28Kelly Weinersmith?

  Yay. All right. Well, that was an amazing answer. Let's go ahead and see what Jonas has to say.

• 23:36Speaker 07

  Hi, Daniel. Hi, Kelly. Thank you so much for having my question on the podcast. Your answer hit exactly what I was going for. Intuitively, I kind of knew that the telescope would see very little, almost nothing really. But somehow, that's where my mind went. Not what does it see, but what can we actually read from a tiny spot on the screen? And the answer blew me away. Just one pixel, and yet we can read so much from it. Hooray, science. And okay. Deep down, of course, I was wondering as well, how realistic is it that we actually find signs of life with the James Webb Telescope? Thanks for the great discussion.

• 24:27Speaker 04

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• 24:56Speaker 01

  Hey, it's Niall Rogers, host of Before the Moment, a Lincoln original series. I'm driving across the country, meeting some of today's most fascinating artists. We're exploring the stories before the moment that changed everything. This week, I'm joined by breakout singer-songwriter Alex Warren.

• 25:16Speaker 03

  To this day, Ordinary would not have done anything, and I would have not been able to put it out if Book Talk didn't back it up and if my wife and her friend didn't back it up. So, pretty crazy how like, just one thing.

• 25:27Speaker 01

  Right.

• 25:28Speaker 03

  I mean, I bet we could point to nine different things in our careers where it's just one thing all of a sudden. If that one thing didn't happen, then I wouldn't be here.

• 25:35Speaker 01

  What you're talking about right now is what I've been talking about since the beginning of my career. There's these things outside of you.

• 25:42Speaker 07

  Yeah.

• 25:43Speaker 01

  That make everything happen. These other forces somehow came into contact with each other.

• 25:50Speaker 07

  Yeah.

• 25:51Speaker 01

  Help propel you to this place.

• 25:52Speaker 07

  It's just insane.

• 25:54Speaker 01

  Experience Before the Moment, a Lincoln original series on the iHeart Radio app, YouTube, or wherever you get your podcasts.

• 26:13Daniel Whiteson?

  All right, we're back and we're answering questions from listeners. And here's a question from a regular listener who's got a really wonderful, charming accent.

• 26:23Speaker 02

  Hi, Kelly and Daniel. This is Jane from Redcar, England. I've got a question for you. Homo sapiens is the only species in the genus Homo, unless Bigfoot is real. Are there any other species that are similarly alone? What animal genuses are most species in it? And what influences whether you end up with one or a thousand? And does it have anything to do with parasites? Still loving all that you do. Thank you so much for answering my question. Have an extraordinary 2026.

• 26:59Daniel Whiteson?

  All right, Kelly, tell us whether we're alone and whether we should feel bad about murdering all of our cousins.

• 27:05Kelly Weinersmith?

  Well, you know, we didn't just murder them. We slept with them and we had their children. And then, well, we don't, we're not sure we ate them. And, uh, you know, check out a past listener questions episode for more information. And, and, you know, in fact, we had, uh, on November 25th, 2025, we had an episode called, uh, how long have we been human? Where we had Scott Solomon on. And so it's worth noting that, yes, the only species of Homo that's around right now is us, but there were a lot of other Homo species in the past, maybe not a lot, but there were others and they've just kind of died out for a variety of reasons.

• 27:44Daniel Whiteson?

  Have you ever wondered what it would be like today if we had several species and they were all like intelligent, but they had like, you know, different characteristics, different kinds of intelligence and different kinds of strength? Would that be wonderful and amazing or like divisive and political?

• 27:59Kelly Weinersmith?

  I want to believe it would be wonderful and amazing, but I am a bit of a cynic and I'm a little bit scared of how our species would handle that. What do you think?

• 28:07Daniel Whiteson?

  Well, I think the fact that we killed them off before written history already tells us the answer. We're not very tolerant of differences.

• 28:16Kelly Weinersmith?

  Yeah, no, okay. Anyway, that's a, that's a true downer right there. But anyway, okay, so Jane wanted to know about other examples. And so there's a couple of fun ones here. So the platypus is another species that is the only member of its genus. Daniel doesn't like me saying Latin names, so I'm going to try to, I'll avoid them. Red pandas are the only species in their genus. And in fact, they're also the only species in their family.

• 28:45Daniel Whiteson?

  But give us a reminder, species, genus, family. I mean, I know as a professional biologist, this is just like back of the hand stuff for you. Why are you laughing? What are you joking about here?

• 28:57Kelly Weinersmith?

  Because you know in my notes that I wrote this all down because I, I either have to say the mnemonic out loud and the only one I memorized is dirty. And so I will not be saying it on the show. So I wrote it. So yeah, you got kingdom, then phylum, then class, order, family, genus, then species.

• 29:17Daniel Whiteson?

  And I've always wondered like, why these divisions? Are these arbitrary dotted lines humans have drawn? Or could you have 19 or four? Like, why this number of categories?

• 29:28Kelly Weinersmith?

  Yeah, that is a good question. We were going to get into that a little bit later. Let's get into that now, though. And so.

• 29:34Daniel Whiteson?

  All right.

• 29:34Kelly Weinersmith?

  Yeah, so some, to some extent, it probably is arbitrary. And so like, the classification system was started by Linnaeus in like, I think, the 1600s. And this was long before we knew about, you know, evolution, long before the theory of natural selection came along. And so this was before we had like, you know, evolutionary trees and phylogenetic trees. And so to some extent, it must have been arbitrary because we didn't have these like connections in our mind and we didn't know, you know, about one species coming from another. But there's some reason to believe that they're useful in like, thinking about evolutionary questions and that they are real. But so I read a paper that at least for the genus level, they were trying to decide.

• 30:17Kelly Weinersmith?

  Like, is what we're seeing in terms of categories of genera real? And so what they did was they looked at real rates at which we think species are being made and real rates at which we think species are going extinct. And then they sort of ran some models and they said, okay, if we're right about calculating some of this stuff, then how often should you see genera popping up? How many species should you see in each genus?

• 30:45Daniel Whiteson?

  But do we even have a definition for a genus? Like, I know definition of a species, it exists, even if it's controversial and fuzzy. Is the definition of a genus have some basis in biology? Or is it just like, I'm putting this here and that there?

• 30:59Kelly Weinersmith?

  Yeah, so different types of taxonomists sometimes have different.

• 31:06Daniel Whiteson?

  And then we have taxonomy of taxonomists now.

• 31:09Kelly Weinersmith?

  That, yes, yeah, yeah. So a paper I was reading was lamenting that different kinds of taxonomists sometimes have different criteria for when they identify something as a genus or not. And so they were arguing that we needed to try to decide, is it possible to have a category of genus that is the same for everybody? And if we don't have that, how big of a problem is it? And so, yes, to some extent, some of the stuff that we're talking about today is going to be arbitrary because this is humans' best attempt at categorizing nature that does not care about us and our attempts to categorize things.

• 31:52Kelly Weinersmith?

  And if you look back at this stuff like 200 years from now, you might find that genuses have been split or genuses have been clumped together because we've decided these things are actually like more closely related. We just hadn't looked at the genetics before. We hadn't had a chance to get around to it.

• 32:07Daniel Whiteson?

  I see. So in some sense, the answer to the question depends on arbitrary choices made by taxonomists hundreds of years ago. But in another sense, there must be something about like the platypus, which makes it different from other species. It's not just that it got randomly categorized into its own genus. It's like more different from all the other species than most species, right? There's like a larger phenotypical distance in some sense.

• 32:35Kelly Weinersmith?

  Yeah, right. And you so you definitely shouldn't come away from this conversation thinking this is like totally arbitrary and random, you know, like there's many, many people working on this stuff. We now have a lot of genetic data. A lot of people have spent time looking at the, you know, the internal organs of these species, the external features of these species, the, you know, genetic information from these species. We have a lot of data that we're bringing to bear on this. And in a month or two, we're going to have Scott Egan on the show talking about how we define species. So we'll have a lot more information on that coming soon. But like, people have collected a ton of data, thought very carefully about this stuff. And a lot of the relationships between organisms,

• 33:17Kelly Weinersmith?

  we are like nearly certain are true. But the question is just, when do you say, okay, we're stopping here and we're putting a name on what's happening right here? You know what I mean? Like, it's definitely, these relationships are flowing and we sort of know in the directions in which they're flowing. The question is just, when do you stop and say, what's happening right here gets a name?

• 33:38Daniel Whiteson?

  Right. Okay. And so like, the platypus is a famous example, because it really isn't anything else sort of near it in the phenotypical tree of life, right? It really is sort of kind of on its own.

• 33:49Kelly Weinersmith?

  Yeah, it looks real weird.

• 33:51Daniel Whiteson?

  And the red pandas, I'm confused about that because there are other pandas.

• 33:55Kelly Weinersmith?

  Panda is an unfortunate choice of a name. I actually can't remember if the like, what most of us think of as pandas, like the big black and white bears, if they were named first, or if red pandas were named first. But they're not. You know, same way starfish aren't really fish. Both of those pandas are not closely related.

• 34:13Daniel Whiteson?

  I love that the Latin name here means fire colored cat.

• 34:17Kelly Weinersmith?

  Yes.

• 34:18Daniel Whiteson?

  What?

• 34:18Kelly Weinersmith?

  Yes, yes. And we, it's a good name, but we let French zoologist George Couvier name it. But the locals at the time, who of course already knew about it long before Europeans went in and were like, this is new. They, they called it wah or chit wah based on its vocalization. So that's probably what we should have called it. But anyway, we call it the red panda.

• 34:43Daniel Whiteson?

  And this thing is not just alone in its own genus, right?

• 34:46Kelly Weinersmith?

  Right. It's alone in its family, which is one category up. So family, genus, species. Pretty cool.

• 34:52Daniel Whiteson?

  Wow. Pretty. It really killed all of its cousins, huh?

• 34:56Kelly Weinersmith?

  It did have some, I think it had some past relatives that died. I can't imagine this sweet little red panda killing off its relatives the way we did, but, or the way we may have.

• 35:09Daniel Whiteson?

  But a fire cat could have done that.

• 35:10Kelly Weinersmith?

  That's, yeah, that's true. I, I met a red panda once and it had arthritis and moved very slowly. So they don't seem vicious to me, but she had a very long, nice life in a zoo. Aardvarks are another member that's alone in their genus, but this one's also alone in its family, like the red pandas, and it's alone in its order, which is one level above family. So order, family, genus, species, aardvarks are alone in there. They had other relatives, but they died off. So there are some examples, but actually as a more general case, I found a couple of different estimates here. Somewhere between 30 to 40% based on the numbers that I found of genera of animals

• 35:50Kelly Weinersmith?

  have only one species in them. So there's a lot of examples. I just picked some cute ones.

• 35:56Daniel Whiteson?

  Wait, here's a Latin question for you. Genera is plural of genus?

• 36:00Kelly Weinersmith?

  Yes. Yeah. Apparently, I looked this up because I didn't want to get it wrong. Apparently genus is, is acceptable, but genera is what is preferred.

• 36:10Daniel Whiteson?

  I see. Well, I like genus is because it sounds like geniuses.

• 36:13Kelly Weinersmith?

  Yes. Yeah. And then maybe people will like accidentally transfer that idea to us and they'll be like, oh, Daniel and Kelly are smart because Kelly said genus genius. I tripped on it. That's ironic.

• 36:27Daniel Whiteson?

  All right. So one third of all animal genera have one species in them. What does that mean? What does that tell us about the history of evolution or anything?

• 36:37Kelly Weinersmith?

  A lot of dead stuff out there. It could, it could mean a lot of things. So it could mean that there's a lot of new like lineages out there. So things just haven't had a chance to split yet. It could mean that there's a lot of extinction out there. And there were groups out there that had a lot of relatives. And then a lot of their relatives died and just one survived like us. You know, we, there were a bunch of other homo species, but only we survived. And that's sort of an interesting question is what is it that determines who the survivors are?

• 37:07Daniel Whiteson?

  Yeah.

• 37:08Kelly Weinersmith?

  But yeah, it could be either of those things or some other things.

• 37:11Daniel Whiteson?

  Does that suggest like a history of bottlenecks? Where, you know, diversity is crucial and only one species survives because they're different?

• 37:19Kelly Weinersmith?

  I don't know if that necessarily suggests a bottleneck. I don't, gosh, that's the first time I've heard the word bottleneck applied to groups of species instead of like a population. Yeah, I don't know. Yeah. Maybe, I guess maybe you've got something catastrophic that happens and it knocks out a bunch of different species, but one. Is that what you're saying?

• 37:39Daniel Whiteson?

  Yeah.

• 37:39Kelly Weinersmith?

  Uh, yeah, that would be worth thinking more about. Yeah, I don't know. So I don't know if it's usually like the same catastrophe that wipes out a bunch of different species, but one. Like it could be, you know, habitat loss wipes out this homo species and parasite wipes out another homo species or something. And it's not like the same thing. But that's a good question. I don't know the answer.

• 38:01Daniel Whiteson?

  Well, in the case of some of these animals, do we have like fossils of other critters in the same genus that are no longer around? So we know that it used to be broader?

• 38:08Kelly Weinersmith?

  Yes. Yeah. For a lot of these, we do.

• 38:10Daniel Whiteson?

  Oh, cool.

• 38:11Kelly Weinersmith?

  Yeah, for a lot of the examples that we went through earlier, we do. So they they were not alone in the past. So another question, that bottleneck question was great. I'm gonna be, that's like gonna be a keeping me up at night question. Okay, so then Jane's other question was, what about genera with lots of species in them? And there are some mega diverse genera.

• 38:33Daniel Whiteson?

  Really?

• 38:34Kelly Weinersmith?

  Yes, and so for plants, there are some mega diverse genera. So for example, Solanum, this is the genus that includes like potatoes, tomatoes, eggplants. Thank goodness for Solanum, it is a delicious genus.

• 38:48Daniel Whiteson?

  I think it's a genius genus.

• 38:50Kelly Weinersmith?

  Yeah, me as well. And I think the genus, the gosh, the genius genus homo has done amazing things with Solanum. If only I could have said that fast. Anyway, all right. Another very diverse genus is Begonia. You may have heard of Begonias, they're kind of flower. There's a lot of them. For animals, because that is specifically what Jane was asking about. There are two beetle genera that are very diverse.

• 39:20Daniel Whiteson?

  The beetles.

• 39:21Kelly Weinersmith?

  The beetles. Agrilis, these are jewel beetles. One that you might have heard of is the Emerald Ashborer, which is causing a bunch of trouble in the United States right now. And Stennis, these are semi aquatic rove beetles. So just another kind of beetle.

• 39:37Daniel Whiteson?

  Just another kind of beetle, wow. Just dismiss amazing biodiversity and evolutionary genius. Just like, just another kind of beetle.

• 39:47Kelly Weinersmith?

  The coleopteran people are shaking their fists at me. I'm sorry, I love beetles, they are wonderful. They are wonderful. In terms of vertebrates, the Pristemantis, there's over 600 species of these. These are absolutely super cute little frogs. And then there are some like genera of geckos that also have a lot of species. And Anolus lizards have a lot of species too. So when do you get a genus that has a lot of species? And Daniel, don't look at the outline, look at me. What do you think the answer is?

• 40:20Daniel Whiteson?

  When do you get a genus that, when do you get a genus that has a lot of species?

• 40:25Kelly Weinersmith?

  It's a Kelly answer. This is D K E U. What do you think the answer is?

• 40:29Daniel Whiteson?

  It depends slash we don't know.

• 40:30Kelly Weinersmith?

  Yes, that's right. Exactly. The answer is it depends. And so I found a paper that said for birds, it seems to be that you get a genus that has a ton of diversity when the birds disperse annually and are feeding generalists. So when they like eat everything and they're willing to disperse to different places. So maybe they're just like, you know, filling a lot of different niches that way. But that kind of ecological stuff doesn't seem to matter as much for mollusks. For things like irises, it tends to be more abiotic stuff. And so by abiotic stuff, I mean stuff that's not living, like, you know, temperature, water availability, stuff like that. Geographic range seems to matter more for things like Australian mammals. So as far as I could

• 41:13Kelly Weinersmith?

  tell, there's no like, rule of thumb that works for everything when you're trying to figure out what genus should have more species. It seems like it depends on what kind of group of organisms you're talking about. And of course, you'll note, I didn't even bother talking about bacteria, because yes, they probably represent more diversity than anything else. But who can wrap your head around those guys? Not me.

• 41:37Daniel Whiteson?

  I know.

• 41:39Kelly Weinersmith?

  So Jane's last question was the most important one.

• 41:43Daniel Whiteson?

  Right.

• 41:44Kelly Weinersmith?

  Does it have to do with parasites?

• 41:47Daniel Whiteson?

  Jane is just pandering now.

• 41:50Kelly Weinersmith?

  And thank you, Jane. I appreciate it. And I hope you have an extraordinary 2026 as well. But unfortunately, as far as I could tell, it doesn't have to do with parasites. But you know what? I'm guessing that's because no one's looked yet. And they should look harder. I'm guessing that the diversity of parasites, in terms of like, what genuses of parasites have the most diversity. I didn't see papers on that.

• 42:15Daniel Whiteson?

  There's a research topic.

• 42:16Kelly Weinersmith?

  That's yeah, there you go. And that probably has a lot to do with like, you know, how are their host diversifying? Like if a host genus has a lot of diversity, probably parasite genuses you find in them also have a lot of diversity because they probably split with the hosts. And so maybe that's where you can find some like predictable trends and, you know, good old predictable parasites, as I always say.

• 42:39Daniel Whiteson?

  Well, here I have a parasite question for you. Is there an example of a parasite losing its host species? Like the host goes extinct, but the parasite adapts and survives?

• 42:50Kelly Weinersmith?

  Yeah, so there I don't, I don't have an example off the top of my head, but I know that's called host switching. So it is a thing that happens.

• 42:56Daniel Whiteson?

  That's amazing.

• 42:56Kelly Weinersmith?

  Yeah. Oh, oh, oh, I have a sad example. Guinea worm is a really awful parasite that goes from copepods to humans. So copepods are tiny little aquatic crustaceans. And they're like so small that you might not see them, but you might accidentally drink them in your water. If you're living in, for example, certain places in Africa. And if you drink them, they, I believe they, I wasn't prepared to talk about the life cycle. I'll do the best I can. I think they find mates in your body. And then the pregnant female, the male dies. Who cares? Pregnant female. I'm just, I'm just joking. No, I'm just joking. I'm joking. I like dudes. And so the pregnant female moves down towards like your ankle or some other part, like your foot.

• 43:39Kelly Weinersmith?

  And she sticks part of her rear end out of your body. It causes a horrible feeling. That makes you want to stick your foot or your leg in cool water. And so you tend to put your foot in the water supply. When you do that, she releases her eggs into the water. And then they get consumed by those little critters in the water we were talking about, and the cycle starts again. And so the way that we've tried to deal with this parasite is that you take something like a matchstick and you slowly wind the parasite around the matchstick. And every day you pull out just a little bit of the parasite and then you clamp it onto the matchstick and you do it again the next day. This is a horribly painful thing and it can get infected. And it's just, you know, miserable.

• 44:22Kelly Weinersmith?

  This is something that actually our species, you can, you can read descriptions of this going back like thousands of years because our species has been dealing with this for a really long time. And it's very distinctive. But if you break it and you pull, by pulling it out too fast, it actually, it's secreting something that controls our immune system. And if you break it, your immune system will have a massive reaction to it, which is worse than you feel when you're slowly trying to pull it out. So the goal is to just pull it all out in one piece without killing it.

• 44:49Daniel Whiteson?

  All right, but I was not asking, what is the most horrific parasite? Please describe it in detail. I was asking about host switching.

• 44:56Kelly Weinersmith?

  I'm getting there, I'm getting there. Okay, so the Carter Foundation and a number of other different organizations have been going to all the different places where you find this parasite. And they, anywhere that time they find a person who's infected, they bring them to a facility and they say, okay, we'll like, support you for the duration of your infection. And anytime your foot hurts and like, you know, every day you'll come to us, you're going to put your foot in cool bleach water. So it'll kill the eggs. Or like, they've got some procedure where they like, make sure that the eggs don't get back into the water. They help them, you know, wind out the parasite safely and they are stopping the life cycle.

• 45:34Daniel Whiteson?

  Okay.

• 45:34Kelly Weinersmith?

  And so they've got it down to like, zero cases in a lot of the countries where you used to find this parasite. And it was down to like, one country where you were still finding it. And it was 14 cases in one year and that was it. And then they started finding it in the dogs.

• 45:50Daniel Whiteson?

  Oh my gosh.

• 45:51Kelly Weinersmith?

  So there was massive selection pressure for the parasite to be able to jump hosts, because the humans were figuring out a solution around it. And maybe before, sometimes it was infecting dogs and we just didn't know. But now they're starting to find it in dogs and the dogs run wild and they go in and out of the water all the time. And so anyway, this could be a case of host switching. It's possible, actually, this is a case where we didn't realize it was in the dogs before. And maybe I haven't actually answered your question. Anyway, we could do a whole episode on this if people are interested. This is like, a really important case of humans trying to eradicate a parasite. Long answer, host switching exists, that might be an example. Guinea worm is the worst.

• 46:25Daniel Whiteson?

  Interesting, is that, that's really the worst? Oh my gosh. I'm so sorry, Jane, for accidentally including that description in the answer to your otherwise innocuous question.

• 46:35Kelly Weinersmith?

  Okay, all right, here we go, Jane. Thanks for asking about parasites at the end there. Thank you so much, Kelly, for answering my question.

• 46:45Speaker 02

  I was surprised how quickly you got to murder and cannibalism, though, and delighted that you managed to shoehorn host switching into the answer, even though it didn't appear to be relevant. Happy to pander to your interests any day. Next time, aliens. I was stunned to hear that we're not special in being home or alone, to coin a phrase, and almost a third of species are the only example in their genera. I guess thinking about beetles makes us seem more unusual. Although I wonder if it was just that the beetle and frog taxonomists were more restrained when taxonomizing, if that's a word. I'm glad that you find my accent charming, Daniel.

• 47:30Speaker 02

  I'll have to think of more questions to give you more chances to hear it. I do love the way Kelly says arbitrary, though. Keep being extraordinary. Thank you.

• 47:49Speaker 04

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• 48:18Speaker 01

  Hey, it's Nile Rodgers, host of Before the Moment, a Lincoln original series. I'm driving across the country, meeting some of today's most fascinating artists. We're exploring the stories before the moment that changed everything. This week, I'm joined by Miguel.

• 48:36Speaker 02

  My small experience with the discrepancy in the business of music made me angry in the best way, and I wanted to finish. So I started really leaning into my therapy, trying to get down to what matters now. Somewhere, Miguelito felt like he didn't have a place to say how he felt. And music was the place that I went to to say how I felt.

• 48:58Speaker 01

  Experience Before the Moment, a Lincoln original series, on the iHeartRadio app, YouTube, or wherever you get your podcasts.

• 49:17Kelly Weinersmith?

  All right, and we are back. And man, Daniel, today is your day, man, because this is another aliens question. You stacked the deck, I think. And so let's go ahead and hear Brandon's alien question. Daniel, is it your birthday?

• 49:34Daniel Whiteson?

  It's Alien Day.

• 49:35Kelly Weinersmith?

  All right.

• 49:35Speaker 02

  Hey, Daniel and Kelly. Like Daniel, I'm fascinated by the idea of aliens and how they could differ from us, especially in regards to size. We are as big or small as our environment allows us to be. And pop culture has shown us a lot of fun depictions of the scale of different aliens. I guess the most egregious would be Dr. Seuss's Who's Living on a Planet the Size of a Speck. I know Dr. Seuss isn't known for his realism. I think physics is going to call BS in that case. But it does get me thinking about what are the upper limits and lower limits of scale that physics will allow for intelligent life? Thanks so much for taking my question.

• 50:18Kelly Weinersmith?

  Oh, Daniel, if you were going to meet an alien, would you rather meet a big alien or a little alien? Or a medium alien, like a Goldilocks alien?

• 50:26Daniel Whiteson?

  I think I'd really like to meet a super duper tiny microscopic alien, because they might have a very different view of the universe and experience phenomena at different scales and have different ways of intuiting how it works and thinking about it. I think that might be super insightful. I'd love to meet quantum sized aliens.

• 50:45Kelly Weinersmith?

  But wouldn't you be worried about, like, stepping on them?

• 50:48Daniel Whiteson?

  I'd be worried about being infected by them.

• 50:51Kelly Weinersmith?

  Or like inhaling it accidentally, like, I'm so sorry, Zor Black.

• 50:59Daniel Whiteson?

  I read a great science fiction book once about aliens that come to Earth and basically just live on people. Yeah, it's called The Woman Who Thought She Was a Planet. It's fantastic. Vandana Singh, she's actually a physicist who's now a science fiction author also. Great stuff.

• 51:14Kelly Weinersmith?

  Cool. All right. Okay. So let's, let's actually answer Brandon's question. I have, I've done what I do and got us off track again. So how small could they get?

• 51:24Daniel Whiteson?

  Yeah, I love that Brandon is thinking about this. What are the limits of physics? And it's important to do this because we want to understand what's realistic about aliens. You can't just fantasize about them being super tiny or being the size of a galaxy because they are limited by physics. But also we are limited in our imagination of what kinds of aliens might be out there. So today I'll give you a sense for what I think could be the smallest or the biggest aliens and what physics limits that. But you know, there could be lots of other ways of being alive and having brains and bodies that we're not thinking about today. So that you're not absolute limits.

• 52:01Kelly Weinersmith?

  Okay.

• 52:01Daniel Whiteson?

  So on the smaller end, I think we should assume that the teeny tiniest building blocks of life have to be atoms. Like we could dig deeper into quarks, but you know, that makes it very, very complicated. Quarks can never be alone. So now we're talking about weird new particle physics and makes weird new structures of quarks. But if we just stick to atoms, that already gives us a pretty tight lower bound. Because atoms are a certain size, right? You really can't build something out of atoms that's smaller than like a tenth of a nanometer.

• 52:35Kelly Weinersmith?

  I mean, that's pretty tiny. I guess I didn't imagine that we were even going to be working on the nanometer scale. But your imagination is vaster or tinier than mine.

• 52:46Daniel Whiteson?

  And I think that's what sets the scale for life on Earth, right? Like the smallest known life we have on Earth are like bacteria or phages, if you think about even smaller. But those things are like, you know, a micrometer. It's harder to get much smaller than that when your building blocks are like order nanometer. Cause you have to have like stable chemistry. You have to store information. You have to have a metabolism. You know, all of this stuff requires a lot of complexity. You can't build life out of like three atoms, right? You need complicated stuff to support even bacteria. And so that means that the smallest kind of life you could have is like a micrometer. And so it's fun to think about like Dr. Seuss and the Who's.

• 53:30Daniel Whiteson?

  You know, a dust speck on our planet is like one to 100 micrometers. And so. If life has to be at least as big as a micrometer, then it's really hard to imagine having intelligent life in complex society on a dust speck, because that life would have to be much smaller than the dust speck, much smaller than a micrometer. And already, we're hitting the minimum size for simple life, bacteria, not to mention like intelligent life in complex society and all sorts of information processing in their brains.

• 54:03Kelly Weinersmith?

  Okay. And as soon as you're getting into intelligence, you require more equipment and more size. Is that what you're?

• 54:08Daniel Whiteson?

  Yeah, intelligence requires like memory and more information processing, communication ability between the members of the species. You know, for example, the human brain has like 10 to the 11 neurons in it. So you're probably not getting intelligent life out of like six or seven building blocks. And even our AIs, right? If you want to build synthetic life, those things have millions and millions of, or billions of parameters, which means you have a very large number of artificial neurons in that neural network. So a lot of complexity is required for real intelligence. So if you have a bunch of neurons all together, and you have a minimum size for like the basic building block, that gives

• 54:48Daniel Whiteson?

  you an estimate of like maybe a millimeter is the minimum size for really complex behavior. And you know, here on earth, we have critters that are like a millimeter, you know, insects, for example, order a millimeter. And those don't individually show a whole lot of intelligence. There's some learning there. Fruit flies, for example, have like, you know, 100,000 or 150,000 neurons in them. And they don't show a whole lot of really complex intelligent behavior. They can learn, they can dance, they can sing to each other. It's fascinating. Actually, they just mapped the entire connectome of a fruit fly brain for the first time. Really super cool. So now they can like, try to understand what is a fruit fly thinking and

• 55:31Daniel Whiteson?

  how's that brain work and all sorts of stuff. Really cool bit of science done by a good friend of mine at Princeton.

• 55:36Kelly Weinersmith?

  Cool.

• 55:37Daniel Whiteson?

  So that's a good reason to think that like, you gotta be at least a millimeter probably in order to be intelligent. And even still at that scale, you got a lot of physics to worry about. Not just like, what's the smallest building block you can make these things out of, but like, how do small systems operate? Because small systems have issues that big systems don't have, mostly having to do with noise.

• 56:02Kelly Weinersmith?

  Oh, like what?

• 56:03Daniel Whiteson?

  Well, small things wiggle a lot. If you're made out of a smaller number of atoms, you're closer to like the vibration of those atoms.

• 56:10Kelly Weinersmith?

  Okay.

• 56:11Daniel Whiteson?

  Small things just have more thermal noise. Thermal noise just means related to the temperature, because remember, the warmer you are, the more the stuff inside of you is jiggling. That's what temperature is. And so the smaller you are, the closer you are to that jiggling. If you're big, you know, you made out of huge concrete blocks, then that jiggling all averages out and doesn't really affect you. But if you're a really small system, then you're going to be affected by that thermal noise, and it could drown out any signals. This is one reason why, for example, our brains are the size they are. You might wonder, like, boy, childbirth is dangerous. Lots of women in history have died in childbirth. That's bad. Why didn't we select for denser brains, smaller neurons

• 56:56Daniel Whiteson?

  that could have the same intelligence at a smaller scale? And the answer is that if you make our neurons much smaller, then you're closer to the thermal noise, and so you lose intelligence. So there's the thought that we're sort of at the sweet spot, right? The smallest brain you could have to have this much intelligence. And so, you know, you really can't get too small and still have complex systems that don't get drowned in noise.

• 57:22Kelly Weinersmith?

  Interesting. I didn't know that.

• 57:23Daniel Whiteson?

  Yeah. And so I would say that the smallest life you could have when building out of atoms is probably microbial life. Is it possible for microbes to be intelligent? Maybe, possibly networks of microbes, but it's tough. Insect level intelligence, millimeter scale intelligence, also possible, but tough. So I think, you know, the smallest sized critter you could expect to be intelligent at the human level is probably about the size of a human.

• 57:53Kelly Weinersmith?

  Really? So I mean, so we've ruled out insect size, but why couldn't you have like a brilliant dog? And like, yes, we have good, good boys and good girls who are very smart and do good jobs. But like,

• 58:06Daniel Whiteson?

  Oh, man, Kelly, I'm doing this at the physics level, which means, you know, factors of two or five, whatever. So I'm gripping dogs in with humans.

• 58:14Kelly Weinersmith?

  Oh, okay, okay.

• 58:16Daniel Whiteson?

  You know, are we talking meter size or centimeter size or millimeter size? So I think a meter sized alien is probably the smallest you could imagine having human sized intelligence.

• 58:25Kelly Weinersmith?

  Okay, perfect. All right, let's move on to upper limits.

• 58:29Daniel Whiteson?

  So when you get bigger in three dimensions, then you suffer from the square cube law. This very basic fact in physics that as you get bigger, your volume grows with your size cubed. Right? Which means your mass grows with your size cubed. But your strength, the muscles and bones depend on the cross sectional area. And that tends to grow with the size squared. Just imagine a cube, you make it twice as long on each side. Then it's gonna have eight times as much stuff in it. Right? But each side is only going to be four times as big as the original cube. So that gives you a sense for like how the internals grow faster than the sides.

• 59:12Daniel Whiteson?

  And this is one reason why, for example, there's a limit to the size of a building you can build. Because if you build a building larger, then it gets really high volume. But the side doesn't get much bigger. And so now like pressure on the side of a building grows because you have like the same amount of force on a smaller area proportionally. And this is also an issue for animals. You try to scale up an animal, then its volume grows faster than its strength, than the strength of its bones and its muscles, which depend on like the cross sectional area there, not the volume. And so that's why, for example, elephants are not as proportionally strong as ants are relative to their weight.

• 59:55Kelly Weinersmith?

  You know what I'm wondering? So, you know, we've got like, we've got elephants and they're really big. But why don't we, and you know, we used to have T. rex and Allosaurus and all of those other like really big land animals.

• 1:00:09Daniel Whiteson?

  Yeah.

• 1:00:09Kelly Weinersmith?

  But we have fewer of them now. Maybe we need to get Steve Brusatti on to tell us why we have fewer massive animals now. Cause there's, you know, there's always been this constraint. Oh, it's probably because we killed them. Dang it. Oh, man, we're coming back to that.

• 1:00:23Daniel Whiteson?

  We didn't kill all the dinosaurs, though the asteroid did that for us.

• 1:00:27Kelly Weinersmith?

  Well, no, but there was like giant land sloths. You know, there were a bunch of Homo species and then there were like giant land sloths. And then there were all these giant birds and then humans went around killing the giant land sloth.

• 1:00:36Daniel Whiteson?

  But none of those were as big as Brontosaurus.

• 1:00:38Kelly Weinersmith?

  No, that's a good point. That's good. Yeah, yeah, yeah. No, anyway, we just gotta have Steve Brusatti on a lot anyway, because he's a lot of fun. All right, go ahead. Sorry.

• 1:00:45Daniel Whiteson?

  But yeah, there are constraints there. Getting bigger is harder because you need really big muscles. You need really big bones. The bones proportionally have to grow faster than everything else in order to keep up with the volume. Also, it makes dissipating heat hard because you have less surface area per volume. And all of this depends on the gravity, right? The more gravity you have on the planet, the faster this constraint comes into play. The less gravity you have, the slower, right? You could have bigger animals on a lower gravity planet. And in the same way, if you're in the ocean, you can escape some of this because the water helps support some of the weight. You have better cooling. That's why, for example, the biggest critters ever are in the ocean.

• 1:01:27Kelly Weinersmith?

  And the biggest critters ever are alive right now. Isn't that pretty cool that we're alive at the same time?

• 1:01:33Daniel Whiteson?

  And we didn't kill them all. Yay for us.

• 1:01:35Kelly Weinersmith?

  Yet. Yeah, that's another fact I learned from Steve Brusatti. Anyway, sorry, go ahead. Very exciting.

• 1:01:40Daniel Whiteson?

  But there's also a limit to how big you can get, even if you're in the water, because the bigger you get, the slower you can think.

• 1:01:48Kelly Weinersmith?

  Oh.

• 1:01:48Daniel Whiteson?

  Signals move across your brain at a certain speed. It's like 100 meters per second, not light speed. And so coordination across your body becomes difficult, right? Now, your brain knows about how long it takes signals to travel from your toes or from your nose and it Coordinates that, right? Somebody touches you at the same time on your toe and on your nose, your brain knows that the signal should arrive at different times and it'll figure that out, it'll reverse engineer that. But if you're like a kilometer size being, then that coordination is going to take a lot of time, seconds or even minutes. It's hard to imagine having like a unified consciousness in that picture. And your thoughts are going to just be slower.

• 1:02:31Daniel Whiteson?

  You know, if you have a crater the size of the solar system, you know, made out of dark matter or something really creative, it's gonna think super duper slow. It's gonna be really hard to communicate with those aliens, you know?

• 1:02:44Kelly Weinersmith?

  And do you feel, you feel certain about like, about that? There's like no way around it? Are you telling us like a truth of the universe? Or is this a like, this is how you'd set up your sci fi fiction book? Cause you're pretty darn sure about it.

• 1:02:56Daniel Whiteson?

  This is all based on a lot of assumptions about how biology works, which is inspired by how things work here on Earth. And aliens could circumvent a lot of this. Like our nerve signals travel at 100 meters per second. You could definitely do that faster, right? The ultimate limit is light speed, which is a lot faster than 100 meters per second. So you could get bigger if you had faster signals, right? That's for sure. If you had different chemistry, if you had different information storage, you could do all sorts of things different. I mean, if things were like not biological at all, we're talking about machine intelligence or made out of crystals or plasma or something, then everything could be very, very different. But I'm trying to extrapolate from Earth-like biology. But you know, that's always limited, it's N equals one.

• 1:03:40Kelly Weinersmith?

  Yep. Okay, cool.

• 1:03:41Daniel Whiteson?

  But the good news is that all of this suggests that intelligence on Earth is kind of in the sweet spot. We're big enough to have complex brains that avoid the noise, but we're small enough to be able to like communicate across our bodies pretty quickly and have like coordinated actions and intelligence. So yeah, humans are pretty awesome.

• 1:04:00Kelly Weinersmith?

  Oh man, I love that we decided that we're the best. Go us.

• 1:04:05Daniel Whiteson?

  In this episode, we went from humans are the worst to humans are the best and back again.

• 1:04:09Kelly Weinersmith?

  Well, you know, we cover a broad range of emotions and a broad range of topics on this show. We've got it all.

• 1:04:15Daniel Whiteson?

  All right, let's send this answer to Brandon and see if we scratched his itch. Thank you for taking the time to put such thought into answering my silly question. Of course, pop culture will take liberties to imagine intelligent life forms ranging from Marvel's Galactus to Dr. Seuss's Whoville. And Daniel is always reminding us that our human and earthly context limits our ability to imagine just how truly alien aliens could be. But it's fascinating to know that scientifically, the most likely scenario is that any beings we encounter someday will roughly be on scale with humans. Thanks again. And now I will not pull a Horton the Elephant and start searching for random clovers to seek out microscopic intelligent life.

• 1:04:58Kelly Weinersmith?

  Well, thank you so much for sending your questions and your curiosity to us. We absolutely adore getting to interact with you all.

• 1:05:05Daniel Whiteson?

  We really do. Your curiosity powers this podcast, and it also powers all of science. So keep thinking, keep wondering, keep demanding that the universe makes sense to you.

• 1:05:17Kelly Weinersmith?

  And keep writing us at [email protected]. Until next time.

• 1:05:22Daniel Whiteson?

  See you later. Thanks, everybody, for listening. Please go and do us a favor and rate the show on whatever podcast app you're using. It really helps people find us.

• 1:05:37Kelly Weinersmith?

  Daniel and Kelly's Extraordinary Universe is edited by the amazing Matt Kesselman.

• 1:05:42Daniel Whiteson?

  He really is a wizard. You can also find us online on Blue Sky, Instagram, and X, D and K Universe. Come engage with us.

• 1:05:52Kelly Weinersmith?

  You can email us at [email protected]. We really do want to hear from you.

• 1:05:58Daniel Whiteson?

  And you can find our website, www.danielandkelly.org, where you'll also find an invitation to join our Discord, where everybody comes and talks about the amazing universe.

• 1:06:09Kelly Weinersmith?

  And we also have the most amazing moderators. This is an iHeart Podcast. Thanks for joining us.

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