Listener Questions #38

00:00:07
Speaker 1: If telescopes looked back from afar, what signs of Earth would glow? Would life in air and seas be something it could know?

00:00:17
Speaker 2: As sole survivors in the genus Homo, we've taken the throne. But are there other genera where a species is similarly alone?

00:00:26
Speaker 1: From the tiniest speck to giants tall? How small or big can thinkers be at all?

00:00:33
Speaker 3: Mmmmm woo which whatever questions keep you up at night, Daniel and Kelly's answers will make it right.

00:00:49
Speaker 1: Welcome to Daniel and Kelly's Extraordinary Universe. Listener Questions number thirty eight.

00:00:55
Speaker 4: Whoop whoop. Hello. I'm Kelly Waiter Smith.

00:01:10
Speaker 2: I study parasites and space, and it's an exciting week to be someone who studies space.

00:01:17
Speaker 4: Do you know why, Daniel?

00:01:19
Speaker 2: Hi?

00:01:19
Speaker 1: I'm Daniel. I study aliens and physics. And yes I'm aware of the Artemis launch because I do not live underground.

00:01:28
Speaker 4: Well okay, but so here's the thing, right, Okay, so you know.

00:01:30
Speaker 2: 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?

00:01:39
Speaker 4: And I was like I'm watching the humans that are going back to the Moon, and she goes, what, and so, you know, I haven't didn't know.

00:01:47
Speaker 2: 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.

00:01:58
Speaker 4: What's your sense?

00:02:00
Speaker 1: 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.

00:02:13
Speaker 4: Okay, isn't she supposed to be at school right now?

00:02:21
Speaker 1: Hi, Hazel? Did you know that we just sent astronauts back to the moon? You know about Artemis?

00:02:29
Speaker 5: Wait on the podcast?

00:02:30
Speaker 1: Yes Live? And do you think it's cool or whatever? I think it's interesting, but I probably wouldn't have been very much time thinking about it. Cool. All right, thank you, have a good day. Okay, thanks Pye.

00:02:43
Speaker 4: Disappointing answer.

00:02:46
Speaker 2: Yeah, for all the money that was spent on it, Yeah, I mean 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 like live feed, and she was like, well, when do we get to see like the astronauts, and as 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 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.

00:03:24
Speaker 1: What it's like for them, and then imagined herself in that ship.

00:03:27
Speaker 2: Probably 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.

00:03:44
Speaker 1: Well, let me ask you what aspect of it is very cool for you? Which part is getting you excited?

00:03:50
Speaker 2: 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 program on the Moon so that we can.

00:04:01
Speaker 1: Learn about like life and low gravity out in 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.

00:04:10
Speaker 2: 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 anti climactic and like, oh, all right, we spent a bunch of money to prove we could do it again, and now we're going to stop. Eah. But I don't know what about you? Are you excited and if so, why.

00:04:41
Speaker 1: 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, there's just the immediacy of that. Isn't that cool?

00:04:55
Speaker 4: That is cool.

00:04:56
Speaker 2: I'm glad the big rocket didn't go boom. That's what I was worried about that I wanted big rocket.

00:05:02
Speaker 4: Not go boom.

00:05:03
Speaker 2: But no, I mean, I thought that was cool. But 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.

00:05:18
Speaker 1: 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 sense that things are starting again and 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.

00:05:42
Speaker 2: 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 Europe up or something like that like we could have explore 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.

00:06:07
Speaker 4: I'll be bummed.

00:06:08
Speaker 2: 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.

00:06:16
Speaker 1: Yep, and good luck to all the astronauts.

00:06:19
Speaker 2: 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 those are all exciting things to me.

00:06:30
Speaker 4: So I am excited about those firsts.

00:06:33
Speaker 2: I mean, there have been Canadians in space before, but yeah, not to the moon, you know, so hooray.

00:06:38
Speaker 1: 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.

00:07:00
Speaker 4: If Daniel wasn't here, we would never get to the point.

00:07:02
Speaker 2: 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.

00:07:10
Speaker 6: Hi Daniel, Hi Kelly. My question came to mind some time ago, back when the James Reap 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.

00:07:41
Speaker 4: This is a fantastic question that I don't know the answer to.

00:07:44
Speaker 1: 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.

00:08:10
Speaker 2: 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.

00:08:19
Speaker 1: 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.

00:08:49
Speaker 2: 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?

00:08:56
Speaker 4: What counts as big?

00:08:57
Speaker 1: Yeah, galaxies are big, and that's why when we point James web telescope into the distant cosmos, the kind of things we're seeing are entire galaxies. Because they're big, they take up enough of the sky that we can resolve them. We can see them.

00:09:13
Speaker 2: Back to diffraction. I got you off track, that's what I do? You get au spec on? Okay.

00:09:18
Speaker 1: Essentially, there's a minimum pixel size in the sky the 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 and 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.

00:09:54
Speaker 5: Right.

00:09:55
Speaker 1: If you have, for example, two sources of light, then in some places those two sources of light will line up to be brighter, 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. So if you have two sources of light, then you get like an interference pattern across a screen. Right. Well, when light comes through an opening, you can model that as a bunch of sources across the.

00:10:27
Speaker 4: Opening, okay, and so some will interfere.

00:10:30
Speaker 1: 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. 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, okay, And so any optical system, even if you have perfect optics with no app or anything like that, you're gonna 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 to 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, and so its diffraction limited resolution for like visible light is like ten or twenty arcseconds, and Hubble is like two and a half meters across, and so its diffraction limited resolution is like zero point one 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 has a big your 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 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 gathered for a while, you can get a really nice picture of Androma 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.

00:13:12
Speaker 2: 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.

00:13:20
Speaker 1: That's not good news. No, we want to be creepy and spy on the aliens.

00:13:24
Speaker 2: 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?

00:13:33
Speaker 1: So currently with like jwst A distant Earth from a nearby exoplanet would just be a pixel. Right, Okay, you just see like one pixel. Now, with future telescopes, maybe we could see more, right, but to have a resolution and like spy on the surface of the planet, you'd need an aperture like the size of the sun. Wow, all right, we're talking about a telescope the size of the Sun, and that's possible. You can actually use the Sun and it's 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 it 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'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. Is it red? Is it blue? Are there greens in there? And we can tell a lot from how the light varies with time and how the light varies with frequency.

00:14:48
Speaker 4: Okay, what can we tell?

00:14:50
Speaker 1: 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. Right. That's 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, 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. A 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 from this one pixel. Right. And the reason we've developed all these techniques is because nobody satisfied just seeing a pixel. They want to know more. 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 thirty years and build that sun size 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.

00:16:29
Speaker 2: Totally yeah, because you're not getting funding for that sun telescope, probably, Kelly the what 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, yeah, about whether or not those aliens eat dinner.

00:16:50
Speaker 1: 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 photons, and by seeing which ones they gobbled, we can tell what's there. So like, is there water in the atmosphere? Is their ozone in the atmosphere? Is their methane? Is their co two? Wow, some of these things are very strong biomarkers because they're in chemical dis equilibrium, 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 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 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? Just blue light dim? Does 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 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?

00:19:39
Speaker 4: All right, yeah, you've got me.

00:19:40
Speaker 2: I'm amazed all of this from a pixel that that's pretty impressive.

00:19:43
Speaker 1: Oh, 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's 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 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.

00:20:40
Speaker 4: It's amazing. Yeah, so cool.

00:20:42
Speaker 2: And that would be with the kind of stuff that James Webb Space telescope is seeing.

00:20:47
Speaker 4: You can get all that information.

00:20:49
Speaker 1: Okay, exactly, wow, But James Webspace 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 two billion times fainter than the star. So it's like you're looking at a firefly next to a street lamp you 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 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 building that have a complicated shaped starshield to avoid the 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.

00:21:53
Speaker 2: Yay, all right, well that was an amazing answer. Let's go ahead and see what Jonas has to say.

00:22:00
Speaker 6: Hi, Daniel high Kelly, thank you so much for having my question on the podcast. You answer it exactly what it was going for intuit different. I kind of knew that the telescope would see very little, almost nothingly, but somehow that 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.

00:23:02
Speaker 1: 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.

00:23:12
Speaker 7: 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 genus is the most species in it? And what influences whether you end up with one are 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 twenty twenty six.

00:23:48
Speaker 1: All right, Kelly, tell us whether we're alone and whether we should feel bad about murdering all of our cousins.

00:23:54
Speaker 4: Well, you know, we didn't just murder them.

00:23:56
Speaker 2: We slept with them, We had the children and then well well we don't. We're not sure we ate them, and you know, check out a past Listener Questions episode for more information.

00:24:09
Speaker 4: And you know, in fact, we had.

00:24:11
Speaker 2: On November twenty fifth, twenty twenty five, we had an episode called 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.

00:24:25
Speaker 4: Were a lot of other Homo species in the past.

00:24:28
Speaker 2: Maybe not a lot, but there were others, and they've just kind of died out for a variety of reasons.

00:24:33
Speaker 1: 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?

00:24:48
Speaker 2: I want to believe it would be wonderful and amazing, But I am a bit of a cynic, and I'm a little.

00:24:53
Speaker 4: Bit scared of how our species would handle that.

00:24:55
Speaker 1: What do you think, 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.

00:25:05
Speaker 2: Yeah, no, okay, anyway, 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 name, 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.

00:25:35
Speaker 1: 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 it?

00:25:46
Speaker 2: You know in my notes that I wrote this all down because 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.

00:26:06
Speaker 1: And I've always wondered, like why these divisions? Are these arbitrary dotted lines humans have drawn? Or could you have nineteen or four? Like why this number of categories?

00:26:18
Speaker 2: 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 all right, yeah, so to some extent it probably is arbitrary. And so, like the classification system was started by Linnaeus and like I think the sixteen hundreds, 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 evolution questions and that they are real. But so I read a paper that at least for the genus level, they were trying to decide, 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 ransom 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?

00:27:34
Speaker 1: But do we even have a definition for genius? Like I know, definition of 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?

00:27:49
Speaker 2: Yeah, so different types of taxonomists sometimes have difference.

00:27:55
Speaker 1: And then we have taxonomy of taxonomists.

00:27:57
Speaker 4: Now, yes, yeah, yeah.

00:28:00
Speaker 2: 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 human's best attempt at categorizing nature that does not care about us and our attempts to categorize things. And if you look back at this stuff, like two hundred 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.

00:28:56
Speaker 1: I see. So in some sense, to answer the question 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, 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.

00:29:25
Speaker 2: Yeah, right, And 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 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, right, okay?

00:30:28
Speaker 1: And so like the planet Post 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.

00:30:38
Speaker 4: Yeah, it looks real weird.

00:30:40
Speaker 1: And the red Pandas I'm confused about that because there are other.

00:30:44
Speaker 2: Pandas Panda is an unfortunate choice of a name. Actually, I 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.

00:31:00
Speaker 4: Both of those pandas are not closely related.

00:31:03
Speaker 1: I love that the Latin name here means fire colored cat.

00:31:07
Speaker 2: Yes, yes, yes, and we it's a good name. But we let French zoologists George Cuvier name it. But the locals at the time, who of course already knew about it long before Europeans.

00:31:19
Speaker 4: Went in and were like, this is new.

00:31:22
Speaker 2: They called it wah or chitwah based on its vocalization, so that's probably what we should have called it.

00:31:29
Speaker 4: But anyway, we call it the red panda.

00:31:32
Speaker 1: And this thing is not just alone in its own genus right.

00:31:35
Speaker 2: Right, it's alone in its family, which is one category up, so family genus species.

00:31:40
Speaker 4: Pretty cool?

00:31:41
Speaker 1: Wowty, it really killed all of its.

00:31:43
Speaker 4: Cousinshn, it did have some.

00:31:47
Speaker 2: I think it had some past relatives that died. I can't imagine this sweet little red panda killing off it's relatives the way we did or the way we may have.

00:31:58
Speaker 1: But a fire cat could have done.

00:31:59
Speaker 2: That's that's true. 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. Ardvarks 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, ardvarks are alone in there. They had other relatives but they died off. So there's some examples. But actually, as a more general case, I found a couple of different estimates here, somewhere between thirty to forty percent based on the numbers that I found of genera of animals have only one species in them. So there's a lot of examples. I just picked some cute ones.

00:32:45
Speaker 1: Wait, and here's a Latin question for you. Genera is plural of genus.

00:32:50
Speaker 2: Yes, yeah, apparently I looked this up because I didn't want to get it wrong. Apparently genuses is acceptable, but genera is what is preferred.

00:32:59
Speaker 1: Nice. Well, I like genuses because it sounds like geniuses.

00:33:03
Speaker 2: 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.

00:33:13
Speaker 4: I saw, I tripped on it. That's ironic, all right.

00:33:17
Speaker 1: 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?

00:33:26
Speaker 4: A lot of dead stuff out there. It could mean a lot of things.

00:33:31
Speaker 2: 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, 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? Yeah, but yeah, it could be either of those things or some other things.

00:34:00
Speaker 1: Does that suggest like a history of bottlenecks where you know, diversity is crucial and only one species survives because they're different.

00:34:08
Speaker 2: 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.

00:34:19
Speaker 4: Yeah, I don't know.

00:34:20
Speaker 2: 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?

00:34:28
Speaker 4: Yeah, uh, yeah, that would be worth thinking more about. Yeah, I don't know, So I don't know.

00:34:32
Speaker 2: 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.

00:34:48
Speaker 4: But that's a good question. I don't know the answer.

00:34:50
Speaker 1: 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?

00:34:58
Speaker 4: Yes, yeah, for a lot of these we do.

00:35:00
Speaker 1: Cool.

00:35:00
Speaker 2: Yeah. 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 megadiverse genera really yes, and so for plants there are some megadiverse genera. So for example, a Solanum. This is the genus that includes like potatoes, tomatoes, eggplants. Thank goodness for salanim It is a delicious genus.

00:35:37
Speaker 1: I think it's a genius genus.

00:35:39
Speaker 4: Yeah, me as well.

00:35:41
Speaker 2: And I think the genus Gosh, the genius genus Homo, has done amazing things with Solanum.

00:35:54
Speaker 4: If only I could have said that fast. All right.

00:35:56
Speaker 2: Another very diverse genus is a Bogonia. You may have heard of bogonia as 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 diverb beetles, the beetles Agrillis.

00:36:12
Speaker 4: These are jewel beetles.

00:36:14
Speaker 2: One that you might have heard of is the emerald ash borer, which is causing a bunch of trouble in the United States right now. And Stennis. These are semi aquatic robe beetles. So just another kind of beetle.

00:36:26
Speaker 1: Just another kind of beetle. Wow, myth amazing biodiversity and evolutionary genius, just like just another kind.

00:36:35
Speaker 2: Of beetle now, the coleopter and people are shaking their fists at me.

00:36:39
Speaker 4: I'm sorry.

00:36:40
Speaker 2: I love beetles. They are wonderful. They are wonderful. In terms of vertebrates, the pristamantis, there's over six hundred species of these.

00:36:50
Speaker 4: These are absolutely super cute little frogs.

00:36:53
Speaker 2: And then there are some like genera of geckos that also have a lot of species, and the noless 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?

00:37:09
Speaker 1: When do you get a genius that? When do you get a genus that has a lot of species?

00:37:14
Speaker 4: It's a kelly answer, This is dKu. What do you think the answer is?

00:37:18
Speaker 1: It depends slash.

00:37:19
Speaker 4: We don't know that's right exactly. The answer is it depends.

00:37:24
Speaker 2: And so I found a paper that said for birds, it seems to me 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 are 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 mullusks. 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 or for things like Australian mammals. So, as far as I could 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.

00:38:22
Speaker 4: But who can wrap your head around those guys?

00:38:26
Speaker 1: Not me, I know.

00:38:28
Speaker 2: So Jane's last question was the most important one, right, does it have to do with parasites?

00:38:37
Speaker 1: Jane is just pandering now.

00:38:39
Speaker 2: And thank you, Jane, I appreciate it, and I hope you have an extraordinary twenty twenty six 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 genus is of parasites have the most diversity.

00:39:03
Speaker 4: I didn't see papers on that.

00:39:04
Speaker 1: There's a research topic.

00:39:05
Speaker 2: That's yet there you go, and that probably has a lot to do with like, you know, how are their hosts 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, well, here.

00:39:29
Speaker 1: 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.

00:39:39
Speaker 2: Yeah, so I don't have an example off the top of my head, but I know that's called host switching.

00:39:43
Speaker 4: So it is a thing that happens.

00:39:45
Speaker 1: That's amazing.

00:39:46
Speaker 3: Yeah.

00:39:46
Speaker 2: Oh oh, oh, I have a sad example, guinea worm is a really awful parasite that goes from copopods to humans. So copapods 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. I believe they I wasn't prepared to talk about the life cycle do with the best I can. I think they find mates in your body, and then the pregnant female.

00:40:15
Speaker 4: 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.

00:40:23
Speaker 2: And so the pregnant female moves down towards like your ankle or some other part like your foot, 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 match stick and you slowly wind the parasite around the match stick, and every day you pull out just a little bit of the parasite and then you clamp it onto the match stick 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. This is something that actually our species. You can you can read descriptions of this going back like thousands of years because their species has been dealing with this for a really long time and it's very distinctive. But if you break it, and by pulling it out too fast, yeah, it actually it's secreting something to control 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 all.

00:41:39
Speaker 1: Right, But I was not asking what is the most horrific parasite, Please describe it in detail. I was asking about post switching.

00:41:45
Speaker 4: I'm getting there, I'm getting there, okay.

00:41:47
Speaker 2: 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. The 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 gonna 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.

00:42:22
Speaker 4: Life cycle, okay.

00:42:23
Speaker 2: 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 fourteen cases in one year and that was it. And then they started finding it in the dogs. 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.

00:42:58
Speaker 4: It's possible.

00:42:59
Speaker 2: 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.

00:43:13
Speaker 4: Guinea worm is the worst?

00:43:14
Speaker 1: Interesting? Is that that's really the worst?

00:43:17
Speaker 4: My gosh.

00:43:18
Speaker 1: I'm so sorry Jane for accidentally including that description and the answer to her otherwise innocuous question.

00:43:24
Speaker 2: Okay, all right, here we go, Jane, thanks for asking about parasites at the end there.

00:43:30
Speaker 7: Thank you so much, Kelly for answering my question. 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 all 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. 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.

00:44:29
Speaker 6: Thank you.

00:44:48
Speaker 4: All right, and we are back.

00:44:50
Speaker 2: And man, Daniel, today is your day, man, because this is another alien's question. You stacked the deck, I think, and so let's go ahead and hear bra alien question.

00:45:01
Speaker 4: Daniel, is it your birthday?

00:45:05
Speaker 1: It's alien day?

00:45:06
Speaker 5: All right, 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 doctor Seuss's, who's living on a planet the size of a spec I know doctor 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.

00:45:47
Speaker 1: Thanks so much for taking my question.

00:45:49
Speaker 2: 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.

00:45:57
Speaker 1: I think I'd really like to meet a super duper tiny, micro scopic alien because they might have a very different view of the universe and experience phenomenon different scales, and I 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.

00:46:16
Speaker 4: But wouldn't you be worried about like stepping on them?

00:46:19
Speaker 1: I'd be worried about being infected.

00:46:21
Speaker 4: By them, or like inhaling it accidentally, like I'm so sorry, or blacks.

00:46:30
Speaker 1: 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 Vandanna saying she's actually a physicist who's now a science fiction author. Also great stuff.

00:46:45
Speaker 4: Cool.

00:46:46
Speaker 2: All right, Okay, so let's actually answer Brandon's question. I've done what I do and got us off track again. So how small could they get?

00:46:55
Speaker 1: Yeah? I love the branding is thinking about this, what are the limits of physics? And it's to do this because we want to understand what's realistic about aliens. You can't just fanticize by 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 being about today, So these are not absolute limits. Okay, 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 very very complicated quarks can never be alone. So now we're talking about weird new particle physics that 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.

00:48:06
Speaker 4: I mean, that's pretty tiny.

00:48:08
Speaker 2: 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, and.

00:48:17
Speaker 1: I think that's what sets the scale for life on Earth, right, like the smallest known life we have on Earth, or 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 you're building blocks are like order nanometer because you have to have like stable chemistry, you have to store information, you have to have a metabolism. You know, all 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 can have is like a micrometer. And so it's fun to think about like Doctor Seuss and the Who's you know, a dust spec on our planet is like one to one hundred 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 and complex society on a dust spec because that life would have to be much smaller than the dust spec, much smaller than a micrometer. And already we're hitting the minimum size for simple life bacteria, not to mention like intelligent life and complex society and all sorts of information processing in their brains.

00:49:34
Speaker 2: Okay, and as soon as you're getting into intelligence, you require more equipment and more size.

00:49:38
Speaker 4: Is that what you're.

00:49:39
Speaker 1: 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 ten to the eleven 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 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 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. Fruitflies, for example, have like you know, one hundred thousand or one hundred and fifty thousand 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 connectum of a fruitfly brain for the first time. Really super cool. So now they try to understand what does the fruit fly thinking, and how does that brain work and all sorts of stuff. Really cool bit of science done by a good friend of mine at Princeton. Cool so that's a good reason to think that, Like, you've got to 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. Oh like what, well, small things wiggle a lot. If you're man out of a smaller number of atoms, you're closer to like the vibration of those atoms. Okay, 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 may I have huge concrete blocks. Then that jiggling all averages down it 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 can 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 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.

00:52:53
Speaker 4: Interesting, I didn't know that.

00:52:54
Speaker 1: 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 on microbes, but it's tough. Insect level intelligence. Millimeter scale intelligence also possible, but tough. So I think, you know, the smallest size critter you could expect to be intelligent at the human level is probably about the size of a human.

00:53:24
Speaker 4: Really.

00:53:26
Speaker 2: 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.

00:53:36
Speaker 1: But like, 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. Oh okay, okay, you know, are we talking meter size or centimeter size or melimeter size? So I think a meter sized alien is probably the smallest you could imagine having human sized intelligence.

00:53:56
Speaker 4: Okay, perfect, All right, let's move on to upper limits.

00:54:00
Speaker 1: 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, and 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 they gives you a sense for like how the internals grow faster than the sides. 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 this 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. They're not the volume. And so that's why, for example, elephants are not as proportionately strong as ants are relative to their weight.

00:55:26
Speaker 4: You know what I'm wondering.

00:55:28
Speaker 2: 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 Elisaurus and all of those other like really big land animals. Yeah, but we have fewer of them now. Maybe we need to get Steve Brusatti on it. Tell us why we have fewer massive animals now? Because 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.

00:55:54
Speaker 1: We didn't kill all the dinosaurs though the asteroid did that for us.

00:55:58
Speaker 4: Well.

00:55:58
Speaker 2: No, but there was like giant lands. You know, there were a bunch of homo species and then there were like giant landslots, and then there were all these giant birds, and then humans went around killing the giant landers.

00:56:07
Speaker 1: But none of those were as big as Brontosaurus.

00:56:09
Speaker 4: No, that's a good point. That's good. Yeah, yeah, yeah. Wow.

00:56:11
Speaker 2: Anyway, we just gotta have Steve Brustani on a lot anyway, because he's a lot of fun.

00:56:15
Speaker 4: All right, go ahead, Sorry.

00:56:17
Speaker 1: 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 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 you can 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.

00:56:58
Speaker 4: And the biggest creaters ever are alive right now. Pretty cool that we're.

00:57:02
Speaker 1: Alive the same time and we didn't kill them all yey for us yet.

00:57:06
Speaker 2: Yeah, that's another fact I learned from Steve Brussati. Anyway, sorry, go ahead, very exciting.

00:57:12
Speaker 1: 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. Signals move across your brain at a certain speed. It's like one hundred 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 signals should arrive at different times, and it'll figure that out of the 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 pick sure, and your thoughts are gonna just be slower. You know, if you have a creator of 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 going to be really hard to communicate with those aliens, you know, And.

00:58:16
Speaker 2: 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 because you're pretty darn sure about it.

00:58:27
Speaker 1: 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 one hundred meters per second, you could definitely do that faster, right. The ultimate limit is light speed, which is a lot faster than one hundred 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 life biology, but you know that's always limited as an equals one.

00:59:11
Speaker 4: Yep, Okay, cool.

00:59:12
Speaker 1: 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 communicate across our bodies pretty quickly and have like coordinated actions and intelligence. So yeah, humans are pretty awesome.

00:59:31
Speaker 4: Oh man, I love that we decided that we're the best go us.

00:59:36
Speaker 1: In this episode, we went from humans are the worst to humans are the best and back again.

00:59:40
Speaker 2: Well, you know, we cover a broad range of emotions and a broad range of topics on this show.

00:59:45
Speaker 4: We've got it all.

00:59:46
Speaker 1: All right, let's send this answer to Brandon and see if we scratched his itch.

00:59:51
Speaker 5: Thank you for taking the time to put such thought into answering my chilly question. Of course, pop culture will take liberties to imagine intelligent life forms, ranging from Marvel's Galactus to Doctor Seus's Whovill, 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 hort in the elephant and start searching for random clovers to seek out microscopic intelligent life.

01:00:29
Speaker 2: Well, thank you so much for sending your questions and your curiosity to us. We absolutely adore getting to interact with you all.

01:00:37
Speaker 1: 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.

01:00:48
Speaker 2: And keep writing us at questions at Danielandkelly dot org.

01:00:52
Speaker 4: Until next time, see you later.

01:01:00
Speaker 1: 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.

01:01:07
Speaker 2: Find us Daniel and Kelly's Extraordinary Universe. Is edited by the amazing Matt Kesselman.

01:01:13
Speaker 1: 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.

01:01:23
Speaker 2: You can email us at questions at Danielankelly dot org. We really do want to hear from you, and you.

01:01:29
Speaker 1: Can find our website www dot danieland Kelly dot org, where you'll also find an invitation to join our discord where everybody comes and talks about the amazing universe.

01:01:40
Speaker 2: And we also have the most amazing moderators. This is an iHeart podcast. Thanks for joining us.