Daniel and Kelly’s Extraordinary Universe - Listener Questions #22

Episode Date: November 20, 2025

Daniel and Kelly answer questions about interstellar comets, evolution of parasitoids, and the nature of scientific theories.See omnystudio.com/listener for privacy information.

This is an I-Heart podcast. I'm Robert Smith, and this is Jacob Goldstein, and we used to host a show called Planet Money. And now we're back making this new podcast called Business History about the best ideas and people and businesses in history. And some of the worst people, horrible ideas, and destructive companies in the history of business. First episode, how Southwest Airlines use cheap seats and free whiskey to fight its way into the airlines. The most Texas story ever. Listen to Business History on the IHeart Radio app, Apple Podcasts, or wherever you get your podcasts. What do you get when you mix 1950s Hollywood, a Cuban musician with a dream, and one of the most iconic sitcoms of all time?

You get Desi Arness. On the podcast starring Desi Arnaz and Wilmer Valderrama, I'll take you in a journey to Desi's life, how he redefined American television, and what that meant for all of us watching from the sidelines, waiting for a face like hours on screen. Listen to starring Desi Arnaz and Wilmer Valderrama on the IHard Radio app, Apple Podcasts, or wherever you get your podcast. Hey there, Dr. Jesse Mills here. I'm the director of the men's clinic at UCLA, and I want to tell you about my new podcast called The Mail Room. And I'm Jordan, the show's producer. And like most guys, I haven't been to the doctor in way too long.

I'll be asking the questions we probably should be asking, but aren't. Every week, we're breaking down the world of men's health from testosterone and fitness to diets and fertility. We'll talk science without the jargon and get your real answers to the stuff you actually wonder about. So check out the mailroom on the IHeart Radio app, Apple Podcasts, or wherever you get your favorite shows. On an all-new episode of IHeartRadios Las Culturistas, Emmy, Golden Globe and Tony Award winner Sarah Paulson

spills on red carpet hacks. We saw these pictures and you're like, what is the story with this? She gets real about the inspiration behind her roles. Oh, no, there is no end to how people will behave. And she puts host Matt Rogers and Bowen-Yag on notice. I don't think so, honey. I feel very, very triggered by this.

Open your free I-Heart radio app. Search Lust Cultureista. And listen to the full podcast now. There's a new comet approaching from deep space. Could we get sick if its dust gets in our face? The jewel wasp parasitoid feels around its heart. host brain. How did evolution come up with this? It's totally insane. Scientific theory, model hypothesis, or law. Do these words really mean anything or nah? Whatever questions keep you up

at night, Daniel and Kelly's answers will make it right. Welcome to another listener questions episode on Daniel and Kelly's extraordinary universe. We've done 22 of these. Hello, I'm Kelly Wiener-Smith. I study parasites and space. And all of these questions today have a bit of biology in them, so I'm pretty excited about it. Hi, I'm Daniel. I'm a particle physicist, and I'll admit there's a bit of biology in everything we do. Oh, yeah.

But there's not physics in everything we do, so that's good news. Yes, there is. Yeah, no, of course there is. Physics is everything. Yeah, I guess I should have. gone with chemistry, and then we could have, like, bonded, even though we knew we were wrong. Exactly. Yeah.

Then we could confirm each other's biases. Yep. Yep. Anyway, I blew it. That's all right. Moving on. But today we're not here to talk about my biases or about your biases. We're here to answer questions from you, from people out there wondering how the universe

works, trying to make sense of it, and scratching their heads a little bit. And we try to help you scratch your heads for a slightly shorter amount of time. And so if you have a question that is keeping you up at night, send it to us at questions at Daniel and Kelly.org. It might take a few months for the answers to come back to you and go online, but we answer every question

at least by email, and some of them even make it on the show. Because we believe in the value of human curiosity. I'm interested in particles. Kelly's interested in parasitoids, but everybody's curious about something. And my favorite thing about science

is that we're all curious about different things, which is why we get to learn about so many different amazing things in the universe, chemistry. And all of the questions that we get, I feel like, are super fascinating and make me think about things in different ways. So feel free to help expand our minds by getting us to think about a new question. That's right. And because this podcast is not just about what we're curious about, it's about what everybody's curious about. So join the conversation. Send us your questions to

questions at Daniel and Kelly.org. And our first question today comes from Tim, who lives in the greatest of these United States, which is, of course, Virginia. What did we say about confirming our biases today? That it's great. That's probably what we said. All right. Let's hear from Tim, who unfortunately lives in Virginia. Hey, Daniel and Kelly. It's Tim from Virginia. I was watching YouTube and watching videos about our newest interstellar visitor Atlas and Omoa and what was the other one called? Not Benu. The other one. So anyway, this is Atlas is the third interstellar visitor that we've had in our solar system.

And they were talking about how it doesn't pose a threat to Earth. But I was wondering if it leaves a debris field in its wake, what are the chances that it has some sort of unknown virus or bacteria or maybe even like their version of tardigrades, which can survive in space? that they just deposit in our solar system that could possibly, if a planet goes through its trail, could get scooped up by a planet and cause problems. I thought it might be a fun question for both of you to answer.

Thanks for what you do. Bye. Oh, this is a fun question. So not that long ago, you and I talked about um-o-ma-mau. No. Oh, muamua. Mu-mu-mua. Oh, mu-mua.

Oh, mu-a-mua. Recently, you and I talked about Omuamua and Avi Loeb's hypothesis that it was an interstellar visitor. And if anybody wants more information, they can go pull that up. Hypothesis is being very generous to Avi. Yes. Idea well-smoking banana peels might be better. Sensationalist nonsense cooked up to sell his book. Oh, yeah, yeah.

We are not pulling any punches today. And so, Daniel, remind us, what do we know about these interstellar visitors? So most of the comets we see come from inside our solar system. They either come from the Kuiper Belt, which is a big chunk of rocky, icy stuff out there deep in the solar system, or long-period comets come even further out from like the Orte Cloud, a hypothetical, never yet observed bunch of icy rocky blobs way, way, way out past Pluto. And so most of the comets, Haley's comet and the other stuff that we see come from inside our solar system. But, you know, our solar system is not alone in the galaxy.

And every once in a while, an icy rocky chunk from another solar system will drift over and enter our backyard. And until this year, we'd only ever seen two of those. Omoomua famous because it was the first. And sort of surprised everybody. We saw it pretty quickly after we turned on a telescope capable of finding these things, which is always awesome because we didn't know how often we would see these. And when you see one immediately, you're like, ooh, wow, maybe these aren't so rare. Yeah. And I got to say one of my favorite facts that I've learned while working with you is that the Ort Cloud is a maybe. It's a thing that we think exists but haven't actually confirmed. And that, I think, was something that you discussed in response to a listener's question. And so anyway, love what I'm learning. Keep going. So 2017, we saw Omu, it was pretty weird. It was like a bare object that was either long and thin or very flat and it was rotating weirdly. And so the reflections were strange. Lots of speculation.

about it. In the end, it looks like it was mostly the nucleus of a comet that had already lost all of its stuff, and outgassed a little bit on the way out of the solar system, giving it a little bit of acceleration. Then in 2019, we saw the second one, Borisov. This is a bigger object, more like a standard comet, had a coma. It was outgassing. Still very cool to see these things from deep in space. And, you know, this is awesome because, as you say, a lot of our knowledge about the rest of the galaxy is hypothetical. It comes either from just observation or from speculation and from models. So to see something come and visit us, we get to study in much more detail and learn a lot about the rest of the galaxy. And so in 2025, we're very excited to see the third one, which is called Atlas. Well, and you must have been very excited because you are really into aliens and Oumuamua was sent by aliens. It was an interstellar ship, right? That's what I heard. No, no, no.

You know, there's a lot of really interesting stuff about Oh, Mu, Mu, and it's totally reasonable to ask, like, does this look like a natural object, or is it weird and could it be artificial? That's totally legitimate, and we should be excited and open-minded about what we could see. And of all the people out there excited to have aliens come visit, I'm definitely near the top of the list. But we also should be skeptical about it, and those claims require a lot of evidence. and there's a lot of push by the chair of the Harvard Physics Department to call this thing aliens and he wrote a whole book about it and we did a whole episode about it and there's lots of videos describing in detail

how this was not an effort sort of primed by scientific integrity, unfortunately. So we're very sure that Omuamua is a comet and it's weird and it's interesting in sort of planetary physics sort of ways but it's not an alien object. Okay, got it. Thanks for clearing that up for me. And so tell me more. about the 2025 interstellar visitor. Yeah, so this is pretty fresh and new, and it's still approaching us, right?

It hasn't reached the closest point to the sun that it's going to reach yet. It's coming into the solar system still, which is exciting. When we found Oumu is already on its way out and moving really fast, so every day it got more distant and smaller and harder to image. But this is coming closer, and so we're getting better and better and crisper and crisper photographs of it. So the first images we had got of it, you can look at these things up online, These come from the two-meter twin telescope.

These are ground-based telescopes. And they show it like a big fuzzy blob. And from those pictures, we couldn't really tell what it was or how big it was. We could tell it's something around 25 to 40 kilometers across, but we didn't know how much of that was like the actual thing and how much of it was like a dusty coma or gas being boiled off of the surface by the sun. So those were our first measurements about it. And we knew where it was and how fast it was going.

So we could tell it was coming from outside the solar system, but we didn't yet know what it was. Is a coma just the like dust and stuff that trails behind a comet? Yeah, exactly. And most of that comes from the sun, right? Solar radiation, the particles, the photons, the electrons, the protons that come from the sun will impact the comet and boil some of that stuff off. And we'll dig into that in a minute. But that's where the comet's tail comes from. And the tail should grow as it gets closer and closer to the sun.

And so right now it's still pretty far. from the sun and the coma is sort of small, but we expect that as it gets closer and closer and it heats up and the sun fries it more, it's going to get a longer and longer tail, yeah. Can we tell the difference between the, like, junk that's getting kicked off because of the sun and the center of it? Is it clear enough to differentiate? We can, in fact. And so we have also space-based imaging. So we have Hubble, we have sphere X, which is a deep infrared telescope, and we have James Webb Space Telescope. But before of those space telescopes were able to take a picture of it, there was a lot of discussion about

what is this thing. It turns out it's coming in sort of close to the planet of the ecliptic, which is the plane that all the planets are on. And so our friend Avi Loeb made a big deal about this, and he suggested that this was evidence that it was an alien visitor sent intentionally to visit our solar system. So he's still on the same kick? He is still on the same kick. And he saw the fuzz around the object, and he misinterpreted that to be like motion smears. Like if you're taking a slow picture of a fast-moving object, it will smear. Because he didn't understand that astronomers already know about that effect and build it into their telescopes with tracking to avoid motion smearing.

So he was arguing that it wasn't a comet, that it was a bare object, maybe metallic, and the fuzz was from motion smearing. Astronomers told him how he was wrong. He mostly ignored them. Again, it's not a discussion that's inspired by scientific integrity. He's just trying to sell his books. But then we got space-based telescopes to take a clear picture of it, And you can see in those pictures a very bright core and a fuzzier coma.

So you can tell the difference from the coma and from the core. And then Spherex can do some really cool stuff where they see the spectrum of light that comes off of it. So the core of it is like two to four kilometers and the rest of it is a fuzzy coma. And what's really fascinating is that that fuzzy coma is mostly carbon dioxide. So these things that are from deep space, they have rocky cores, but there's a lot of ice. on them. And there's carbon monoxide ice, carbon dioxide ice, and then water ice. And these things evaporate at different temperatures. Carbon monoxide evaporates at a pretty low temperature, like 40 Kelvin. It doesn't take a lot of solar rays to fry off all the common monoxide. Carbon dioxide

at about 100 Kelvin and water at hundreds of Kelvin. But we don't see any carbon monoxide in the coma. So this thing is probably a combination of CO2 carbon dioxide and water. And And since it's still far out on the solar system, it's mostly outgassing the CO2, which sublimates on the surface. And when it gets closer, we'll probably see some water, some water ice turn into steam. Is there rock in there, too? And that's just not getting kicked out into the coma? Yeah, exactly. Probably there's also rock out there.

And, you know, Avi responds to this and saying he thinks actually the thing glows on its own, that it's not just reflecting light. Which astronomers pointed out was just him misreading a plot in a paper. maybe intentionally, maybe not, who knows. Anyway, you should mostly ignore all of his nonsense and pay attention to the astronomers to actually know what they're talking about. So it's a fascinating object. We're going to learn something about deep space and what things are made out of. This thing is probably a chunk of ice and rock from somebody else's ort cloud, right?

Some other star has ort clouds, and we snagged a piece of it because they lost it. It's going to be really interesting. It's not going to come close to the Earth. So if you're worried about this thing, because it's a big chunk of ice and rock, About the same size as the one that ended the dinosaurs, but it's not going to hit the Earth. In fact, when it makes its closest approach to the sun, we're going to be on the other side of the sun. That's reassuring. I like that.

Although I'm sure we'll see it less well, and that's a bummer, but tradeoffs. All right. So that's the setup. Tim has a really fun question. He's wondering, like, what if this thing really does come from aliens? What if it's, like, loaded with their viruses or alien tardigrades? And those things boil off and they sort of make a path. through the solar system, and some of them come to Earth, are we in danger?

What do you think? Awesome question. Yeah. Well, we're not going to pass through any sort of dense part of its tail. Like, we're going to be the other side of the sun when it turns around and it's going to exit the solar system. So it's not like it's going to leave a long wake that we're going to fly right through. But, you know, it is leaving particles and bits of itself in our solar system.

And so who knows, if this thing actually is from aliens and, like, seated with all sorts of weird microbes. Maybe they design this thing to, like, explode when it comes close to the sun and spray all of its stuff everywhere through the solar system, in which case some of them will come to Earth and could potentially, you know, come through the atmosphere and land on the surface and infect people's brains and convince them to live in Virginia rather than California. I mean, we're talking deep tragedies here. Oh, give me a break, man. That's where he was going, right?

They might even convince them to study chemistry. I mean, those aliens, who, they're up to no good. I mean, that would be a nefarious plot. Absolutely. So, but do you think so, okay, so when we were doing our tardigrade episode, which we did a little while back, we showed that, yes, tardigrades are, like, resistant to tons of things, but when you expose them to the radiation in space, they do kick the dust. They can't survive that indefinitely. And I would have to imagine there's not a lot that could survive an interstellar voyage, but I

guess we can't rule it out. What do you think? It depends. I mean, you could survive an interstellar voyage if you're the cold. of one of these objects, right? If you're shielded by a lot of ice and rock, then, yeah, you could survive the radiation. You know, whether you could survive being frozen that long

and your metabolism could restart, you know, I think that's a biological question. But I think we've seen that in lots of critters here on Earth. So I think it's plausible for things to be frozen at the core and survive the interstellar trip and even the solar wind. But then, you know, once it disperses in our solar system, you know, then it's vulnerable again. And I think that's the most,

dangerous point. Yeah, when it gets kicked out of the coma or kicked into the coma. Yeah. Unless, of course, they come out in, you know, tiny little microscopic alien ships and so they have their own shielding. I mean, if we're going to speculate here, like, let's go all in, right? Let's go lobe style. Let's pretend we're the chair of the Harvard physics department. That would be pretty solid. Exactly. So, Tim, this is a really exciting event. It's super fascinating. There's no evidence that it's aliens. Like the astronomers want to believe that it's aliens, but so far there's nothing that points in that direction. But of course, you don't know. And it could be that it comes deeper into the solar system and we learn new stuff, in which case we're all very happy to believe

that this is aliens if the data points that way. And in that scenario, it's not going to directly leave a wake for us to fly through, but it could disperse stuff which eventually will come to Earth. I mean, there's a lot of cosmic dust that falls to Earth every day. So it could control. tribute to that. We could all be breathing in bits of an alien package one day. Could we have all already breathed in, oh, muamua, mua bits? Oh, yeah, absolutely. Nice. Exciting. We are connected through space and time.

All right, let's see what Tim thinks of our answer. Is he going to sleep well tonight or not? Let's find out. Hey, Daniel and Kelly. Thank you for answering all of my questions. I can rest assured now, knowing that Earth won't go through an alien comet's tale. and gain a whole bunch of microbes that will convert us to alien life forms. Keep up with good work.

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Listen to business history on the IHeart Radio app, Apple Podcasts, or wherever you get your podcast. All right, we are back and we're answering questions from listeners, questions we get every email, and also questions on our Discord. If you love thinking about the universe and hearing us chat about it, you might want to chat with us. We are very active on our Discord. If you want to join, it's for everybody who's curious about the universe. Go to our website, www.danielandkelly.org where you'll find the link to join the Discord.

So many fun, nice people talking about the universe and asking questions. Kelly, tell us about this question. Well, at first I'd like to just note that we also have the best moderators. So, you know, another good reason to come join us. All right. So Marco from Discord had this question about parasite manipulation of host behavior. And Marco's not just another Kelly sock puppet account? I mean, you'll never know.

You'll never know. Hi, Daniel and Kelly. I have a question about the jewel. wasp discussed in Ed Young's book in immense world. Horrified is an understatement, as is the sentence, I had a nightmare about this. In the book, Young describes

how the jewel wasp feels around for the cockroach brain with its stinger, and I keep wondering about the evolutionary mechanisms at play here. The wasp doesn't know what a brain is, obviously, but how on earth could it have evolved the precision to accomplish this? Unwilt aside, this

strongly implies that the wasp has not only absurd command of its own body, but the body of the cockroach as well. There's a ton of evolutionary time to miss the sweet spots in the cockroaches back and head and not be successful. There's a neat series I've been watching on octopuses and it discusses how these intelligent creatures

learn everything on their own without parental support. Wasps aren't teaching their young where to sting. So how does this amazing ability emerge from this tiny little wasp brain? Just realized I've been listening to the podcast long enough to realize the answer is, we don't know. Thanks for everything. Love the show. Can't wait to hear the answer. All right. So first of all, I love that Marco clearly has been paying attention and suspects that there's a high probability the answer is going to be, I don't know.

Good job, Marco. Welcome to the forefront of science, everyone. That's right. That's right. And so, yes, the answer at the very end for a lot of these questions is going to be, we don't know. But let's talk about some of the things that we do know first because I love this system. And I'm going to use it as an excuse to tell you all about it. Yeah, so tell us about the jewel wasp and what it does to poor cockroaches. Are we going to feel sympathy for cockroaches at the end of this? Oh, maybe. And then I've got to talk about the parasitoids that manipulate web-building behavior in spiders and actually makes you feel sympathy for spiders. That's another day.

I love those systems. Their videos are just like nuts. Anyway, all right. Today, we're a pro-cockroach. Tell us why. Okay. Well, I'm actually going to end up on team jewel wasp. But anyway, so jewel wasps, they're beautiful.

they're kind of iridescent, they need to lay their eggs somewhere and provide their babies with a meal. And so essentially what they're going to do is paralyze a cockroach, hide it in a really great spot, lay an egg on it, that egg is going to hatch, eat the cockroach from the inside, and then leave its carcass when it's done. That's the big overview. And the cockroach is alive while these things are growing inside of it? The egg is attached to the outside of its body, but then the baby does eat its way in. Oh, boy. Yeah, it's pretty gruesome. And why does the cockroach have to be alive?

Is that so that it stays fresh and tasty, the way we, like, put, like, living lobsters into pots? Yeah, yeah, I don't feel comfortable about that. Don't do it myself. But anyway, so this would be, like, you wouldn't want to leave the pure-ed spinach for your baby out on the counter for, like, a week. You know, you want your cockroach and your spinach to be fresh. All right, so here's how the process goes down. So the jewel wasp and the cockroach get in a tussle. because the cockroach knows that the jewel wass is bad news.

So the first thing that the jewel wasp does, if it gets lucky enough and can get the angle right, is it stings the cockroach in the thorax, so like the chest kind of region. And this will paralyze the cockroach's front legs for up to five minutes. And so this makes it so the cockroach can't fight back quite as well. And the jewel wasp will deliver its second sting. The second sting is in the head.

So it goes through the neck, kind of moves through the tissues until it finds the brain. It's got this like ovipositor that delivers the sting. So it's almost like a needle at the end. And so it puts this needle up into the brain and it delivers another sting. Yikes. And this sting, I know, it's nasty. This sting, but I love it.

The sting does a couple different things. It's nasty in just the way Kelly loves. It is. We're learning a lot about you today. Yeah. Well, nature's horrible, but fascinating. And so now the cockroach starts grooming itself furiously. And I think we're not totally sure why that is happening.

Maybe it's because they want to. the meal to be like super fresh, you know, like bacteria infecting your meal. And so the cockroach cleans its stuff up a lot. And then another interesting thing is that the cockroach technically is capable of moving, but its desire to initiate its own movement pretty much goes away. So it can move, but it doesn't. It's desire. We're talking about what it's like to be a cockroach, like we're in the mind of the cockroach thinking about what it wants. So, all right, I'm being a bit anthropomorphic about it, the cockroar, I don't know what the cockroach is thinking, but whereas usually cockroaches in an area where they know that there's like something dangerous would initiate movement

and would get out of there, this cockroach just kind of stands around. But it's still capable of moving because the parasitoid will like find a good nesting spot and then come back and grab the cockroach's antenna and lead it to a nesting spot and the cockroach will follow. It's like, it's like driving it? It's like, let's go this way, let's go that way. Yeah, the way it's usually talked about is like, it's like walking a dog on a leash or something like that. It just follows. And so then it gets moved into this little, like, nook where everything can be hidden so that nothing will eat the cockroach and also eat the baby because the cockroach can't fight back really anymore. And it will, the mom will put the cockroach in the nest, lay the egg somewhere on

the cockroach, I think, like near its leg, and then seal up this little nest site with, you know, leaves and rocks and stuff like that. And then the rest of the process takes about eight days, the egg hatches, eats the inside of the cockroach, pupates inside, so it goes through a couple developmental stages in the body of the cockroach. So it's basically laid the egg along with some food. It's sort of like a chicken egg, it's the embryo with the food, but the chicken provides it instead of stealing it from a cockroach.

All right. Yeah, that's exactly right. And a lot of parasitoids do this. There are parasitoids, you know, just the other day I saw a parasitoid dragging a giant spider. It had paralyzed and it was dragging it to its nest so that it could then lay eggs on it and keep its meal fresh. Oh, boy. And so what's special about this system, not from the perspective of the cockroach, of course, but is that a lot of parasitoids will paralyze food and then lay their eggs in or on it as a meal for when they hatch. But you've got this extra layer where the parasitoid is also able to direct the cockroach to go to a particular location rather than needing to physically drag it there.

which a bunch of others have to do. Wow, amazing. Yes, amazing. So the cockroach, like, participates in its own demise. It does. It does. It's complicit. That's gross.

Complicit. I don't know that I, that word has too much human baggage. Let's, it unwillingly, unwittingly does the wasp bidding. Okay, so Marco was interested in the fact that when that second sting happens and the sting is happening in the brain, the wasp that is stinging the brain, the wasp that is stinging the brain, its mom isn't there to like teach it how to do that. So how does it just know where to sting in a brain? And at the end of the day, the answer is going to be, we don't really know. But I'm going to give you a little bit more detail about what is actually happening when it stings the brain. So we talked about how it puts its little like hypodermic needle-esque butt into the neck of the wasp and it starts going up to the brain. And there have been some experiments trying to figure out what happens inside the cockroach's brain. So one thing they did was they Injected carbon-14 radio-labeled amino acids into the stinger, and then they look to see where it ended up in the cockroach. And it does end up in this area called the sub-esophageal ganglion, so it's, like, kind of the bottom part of a cockroach's brain.

So injecting carbon-14 labeled amino acids, this is just a way of tracing, like, where something goes. It's like, add, like, a little dye so you can see where something goes. But in this case, it's not a visual dye. It's like you're measuring the radioactive decays, or how does that work? Yeah, that's exactly right. Fascinating. Wow. Yeah, pretty cool experiment.

Okay, and then they did some other experiments to try to figure out what it is that the wasp is queuing in on to figure out to figure out where it's supposed to deposit what we call it. We call the stuff that gets deposited during the sting, venom, which is awesome. Anyway, so they've done things like humanely euthanize a cockroach and then remove its brain and then give it back to. the wasp. And when you do that, the wasp spends a bunch of time, like, searching and not delivering its venom. It's like, what, something is missing in here? And so it's, like, it's definitely It's looking for the brain. It's looking for the brain. And it gets kind of confused when it's not there. And so then the scientist looked a little bit closer at the ovipositor, and they found sensors on there. And some of the sensors are mechanical receptors, so they, like, can touch

things. And some are chemical receptors. And so first, they wanted to dive into what, happens with the mechanical receptors. And so they took all the mechanical receptors off of the wasp and the wasp just kind of like searched around for a really long time. It was super confused because it couldn't feel anything. Then they humanely euthanized the cockroaches and they put a very soft substance that wasn't very brainlike into the head of the cockroach. And the wasp also searched around for a really long time and was like, what is going on? But then they put a hard substance, harder substance that's more like the brain. And the wasp, and the wasp, responded more quickly. So it doesn't have to be a brain, but it's got to feel right.

So they're testing what the wasp wants to sting. And they're like, how about a squishy brain, having an actual brain, how about something that feels like a brain? They're like exploring the space of what the wasp is willing to engage with. That's fascinating. Yeah, yeah. And if you like kind of mix up the brain and kind of change its consistency by like mixing it up with like scissors or something, they also are confused and are like, what the heck is going on here? So it looks like the mechanical stuff really matters. And so that suggests to me that there's some genetic coding that gets passed from generation to generation doesn't need to be learned where they know like it goes in the neck and then you look for something that feels a certain way. And I don't think we've

looked close enough in this system to understand exactly how that happens. But we have looked at other behaviors that are, you know, what we would say is innate. They just happen without learning. So it's so important that it touches the brain that the system has evolved requirements to ensure that it only happens when there's like an actual brain there to be delivered on, not just like randomly spraying this stuff in the head of the cockroach. Yeah, so presumably the chemical cocktail that gets delivered into the brain is expensive to make in some way, like requires a lot of energy or certain nutrients or something.

So you don't want to go stinging things and waste. it. And so if this cockroach seems like it's totally off for some reason, then you abandon it. Well, go find a cockroach with a bigger, tastier brain. That's right. Well, there are other parasitoids that can test and see, like, are there already parasitoid wasps living inside of this insect? Because I don't want my babies to have to compete with babies that had a head start. And so there's all sorts of, like, crazy stuff that happens when the wasp is, like, evaluating its host for quality. All right. So this is really fascinating and very complex behavior. And I feel like Marco's question is essentially, how does the wasp evolve this kind of behavior? The mom is not there

to teach it, which means it must be somehow innate, which suggests it's like in the code of the DNA, which means it comes from evolution, not from like the wasp culture. How is such a complex process ever evolve? It feels impossible to imagine that you develop such an intricate system because it needs many parts to work all at once. Well, maybe your imagination is limited, Daniel. No, I'm just kidding. Yes, it is very complicated. So one of the ways that we look at the evolution of complex behaviors

is that we'll look at things that closely related species are doing. And sometimes you can see the steps that build in a more complicated behavior. So, for example, this system has two stings, and one of them is a little bit more complicated. But a lot of other parasitoids, as we've already talked about, do one sting to paralyze their prey. So you can see that as like a beneficial early step. We have not in this system been able to work out the order in which all of these complicated things evolved and sort of built up. And so let me just make it explicit. You're suggesting that it's a complex series of behaviors, but there probably are simpler versions of it that are also beneficial.

You don't need all the complex pieces in order to gain some benefit. And that would allow you to tell the evolutionary story. Is that the argument? Yep, that's exactly right. And every intermediate step needs to be beneficial in order for it to like keep passing through the population unless you've got drift going on. But anyway, okay, so these are, there are beneficial steps.

And, you know, you can imagine something like initially the jewel wasps only stung the cockroach once and paralyzed it and then you had to drag it. But then there was one wasp that had some mutation that made it extra stabby. And it stabbed once in the thorax and once in the brain. And that did something that made the cockroach a little bit easier to handle, which meant the mom could lay more eggs and could do this more

times, and maybe that got passed on genetically. And you can imagine generation after generation that gets honed and more and more beneficial. And maybe my imagination is limited, but does the phrase extra stabby appear in the biological literature anywhere? No, that's just because I'm super creative, you know? That was my creativity. I'm just kidding. You're very creative. But yeah, so we don't know exactly the path that this. took. But you can imagine how it would have built up. And then, you know, it's possible somebody could test this by looking at closely related wasp species. And maybe if you understood more mechanistically about how this was all happening, you could understand how one step could happen

after another. But for this system, I would say we don't have a really good evolutionary answer. I think that all makes sense that complex behaviors evolve from simpler behaviors that are also beneficial. And it sometimes takes a while to figure out what path you can take from simpler to more complex. I think the thing that blows my mind is that these complex behaviors feel kind of fragile. Like everything has to work for this to happen. And it feels like there's so many ways for it to go wrong. It's incredible that it relies on such a complex system. And then it mostly works. And then I look at, you know, like humans. I've raised a child. It's complicated. It feels like there's so many ways you can go wrong. And then I walk around. I'm like, wow, all of these

humans, they were raised by people. It seems to mostly work. It's incredible. You know, biology seems so fragile, but it is pretty robust. Yeah, I mean, it is incredible, but, you know, there's plenty of times when jewel wasps go after cockroaches in nature and the cockroach wins and the jewel wasp doesn't get to sting or... Yay, cockroach. Or, you know, the jewel wasp dies for one reason or another, or it just doesn't... Like, there's plenty of times in nature where these things do fail, and those individuals usually just get wiped out of the population. And just so it doesn't sound like I'm saying, well, whenever we're talking about complex behaviors, we always... We always just imagine a picture.

There are systems where step by step we've sort of figured this stuff out. And I'm working on finding a behavioral geneticist to come on the show to talk to us about those answers. So stay tuned. All right. Well, I think that's a pretty good answer for Marco. Let's inject that into his head and see how his brain responds. Did we lead you to the answer, Marco? I promise we won't lay any eggs on you.

After hearing your answer, I admit I'm no less terrified of jewel wasps. I can only hope I don't have another fever dream frantically trying to keep one from stinging the back of my head by jumping into water I can't find. I'm forever in awe of evolution coming down to random events and mind-boggling numbers until some advantage emerges and get successfully encoded. I keep going back to a couple points you made. One is that without passing down knowledge, genetic coding, instructs in organisms' behavior. The wasps are compelled to behave as they do, and evolution handles the rest. With most of the podcast episodes, we end up with more questions like, how did Kelly end up on Team Jewel Wasp? I can't side with that freak show. I fully support Wally's cute sidekick, not the Jewel Wasps.

That feels like siding with monstrous killers, or the 17% of people that prefer white chocolate. Not tolerate it, but like it better. It truly is an extraordinary universe. Thanks, Daniel and Kelly. On the podcast Health Stuff, we are tackling all the health questions that keep you up at night. Yes, I'm Dr. Priyanka Wally, a double board certified physician. And I'm Hurricane Dibolu, a comedian and someone who once Googled, Do I have scurvy at 3 a.m? On Health Stuff, we're talking about health in a different way.

It's not only about what we can do to improve our health, but also what our health says about us and the way we're living. Like our episode where we look at diabetes. In the United States, I mean, 50% of Americans are pre-diabetic. How preventable is type 2? Extremely. Or our in-depth analysis of how incredible mangoes are. Oh, it's hard to explain to the rest of the world that you, like, your mangoes are fine because

mangoes are incredible, but like, you don't even know. You don't know. You don't know. It's going to be a fun ride. So tune in. Listen to Health Stuff on the IHeartRadio app, Apple Podcasts, or wherever you get your podcasts. The Big Take podcast from Bloomberg News dives deep into one big global business story every weekday. A shutdown means we don't get the data, but it also means for President Trump that there's no chance of bad news on the labor market.

What does a bacon, egg, and cheese sandwich reveal about the economy? Our breakfast foods are consistent consumer staples, and so they sort of. become outsize indicators of inflation. What's behind Elon Musk's trillion-dollar payout? There's a sort of concerted effort to message that Musk is coming back. He's putting politics aside. He's left the White House. And what can the PCE tell you that the CPI can't?

CPI tries to measure out-of-pocket costs that consumers are paying for things, whereas the PCE index that the Fed targets is a little bit broader of a measure. Listen to the big take from Bloomberg News every weekday afternoon on the IHeart radio app, Apple Podcasts, or wherever you get your podcasts. And she said, Johnny, the kids didn't come home last night. Along the central Texas planes, teens are dying. Suicides that don't make sense. Strange accidents and brutal murders. In what seems to be, a plot ripped straight out of Breaking Bad.

drugs, alcohol, trafficking of people. There are people out there that absolutely know what happened. Listen to Paper Ghosts, the Texas Teen Murders, on the IHeart Radio app, Apple Podcasts, or wherever you get your podcasts. I'm Robert Smith. This is Jacob Goldstein. And we used to host a show called Planet Money. And now we're back making this new podcast called Business History

about the best ideas and people and businesses in history. and some of the worst people, horrible ideas, and destructive companies in the history of business. Having a genius idea without a need for it is nothing. It's like not having it at all. It's a very simple, elegant lesson. Make something people want. First episode, how Southwest Airlines use cheap seats and free whiskey to fight its way into the airline business. The most Texas story ever.

There's a lot of mavericks in that story. We're going to have mavericks on the show. We're going to have plenty of robber barons. So many robber barons. And you know what? They're not all bad. And we'll talk about some of the classic great moments of famous business geniuses, along with some of the darker moments that often get overlooked.

Like Thomas Edison and the electric chair. Listen to business history on the Iheart radio app, Apple Podcasts, or wherever you get your podcast. Next up, we have a question from Southern Scotland, and I am so excited because I got to go to Scotland for the first time last month. I was in Edinburgh, which is probably not where Ben is from. But Ben, your country is beautiful. I loved it. And vegetarian haggis, A-plus.

And I'm going to Scotland next week for a wedding in Inverness. Yeah, and you're going to wear a kiltz. I'm going to wear a kilt, exactly. All right, but today the question is not about Daniel's wardrobe at Scottish weddings. It's about what these terms in science mean. So let's hear Ben's question. Hello, Daniel and Kelly. It's Ben here from Cucubri in southern Scotland.

I'd really like to know what you think is the difference, if any, between a theory, a law, a hypothesis, and a model. I'm especially curious about Darwin's theory of the origin of species. Is this a typical scientific theory? Does it have predictive power? can it be refuted by experiment? I feel I really need the combined advice of a particle physicist and a parasitologist

to help to settle these questions. I really enjoy your podcast. Oh, this is a really great question. This is a really fun question. I'm really glad that Ben asked it because it's one of these questions where if you ask philosophers or if you ask scientists,

you'll get a different answer. And if you ask different philosophers and different scientists, you'll get lots of different answers. It's something a lot of people are not very precise about, frankly. Yeah, I think when I was an undergrad, I remember in my biology class, there were definitions of all of these terms. And then I was very confused later on when they were used in ways that were not at all consistent with what was in that textbook.

And anyway, now I know we're all sloppy. Well, you know, scientists are practitioners. We're not experts in the philosophy of science. We go out there and we do science and we say theory. We say law. We say model. We haven't all taken philosophy classes where, like, the distinctions, between these things are argued by nerds who are super excited about it.

You know, we're excited about the biology or the chemistry or the physics or that kind of stuff. And so when you hear scientists talk about it, they're not often being very precise because they're not experts in the definitions of these terms. Philosophers of science are the folks who really narrowed down on this. But again, also philosophers of science disagree reasonably with each other about how to describe this stuff. So I'll break it down for you in a way that makes sense to me.

But definitely other people will have different definitions. this. This is not definitive in any sense. And if I could just mention that I also think another thing that makes it complicated isn't just that most of us don't actually know what these terms mean. It's that even if we did, when you understand something, it's not usually like there's a clear switch that gets flipped where you're like, oh, now we've entered law lands. Before we were in hypothesis land. It's like you need to slowly accumulate and it's not always clear when it's time to like update to a new term. And so anyway, that probably complicates things too. Yeah, yeah, absolutely. So let's start with laws. I think of a law as something the universe actually does. There's some truth out there. And one of the basic assumptions in science is that the universe follows laws and we don't know them, but we can do experiments and think about it and all those sorts of stuff to try to figure them out. So we think the universe follows some sort of concise, simple, fundamental rules. And those are the laws of the universe.

All right, still with me. Yep. Cool. Now, we don't know what those things are, but we can have theories about it. So we want it from law to theory. Theories are like our explanations for how the universe works. So general relativity, for example, is a theory about how matter bends space and how space tells matter to move. Quantum mechanics is a theory that tells us that space is filled with oscillating fields.

These are theories. They're like our explanatory frameworks to describe the theory. things that we see in the universe. And we hope that those theories line up with the truth, the laws that are actually out there in the universe. And so theories, it's kind of a fuzzy term, right? Theories are sort of like our ideas. They include a bunch of evidence and they come together to give like some sort of coherent explanation for how something is working in the universe. A theory is not just like a random guess, not just like, hmm, maybe it's this, right? like a fan theory to explain the ending of some movie you just saw, right?

It's something that's really based in evidence and has been tested and it's sort of part of our explanation of the universe. Yeah, lots of different labs have looked at it. It's been looked at from lots of different angles, predictions have been tested. Yeah, agreed. Yeah, so the whole, like, you know, gravity's just a theory man. Doesn't mean that, like, we don't know anything about gravity or it's just, like, one of ten options to explain why we stick to the surface of the Earth.

right? A theory can be something that's very well developed and understood. I don't know. Was gravity really the best pick there? Seems like there's a lot we don't know about gravity. That's the other thing about a theory is that they're never complete, right? They're evolving. They're changing. You know, gravity is a wonderful, amazing theory, but there's definitely a lot we don't know about, you know, what's going out at the center of black holes or the early universe or fundamentally how gravity works for particles, right? Definitely it's not a complete explanation of the It's an explanation of part of the universe, and we don't have a unified theory. We'd love to have one because we think there is one set of laws, but we have sort of piecemeal theories that we think are approximating those laws. Excellent. I'm glad we have a scientist slash philosopher on the show. So there are laws out there. We try to build theories about how the universe works and follow those laws. What's a model in that sense? And model is a very overloaded term. In physics, we use model to mean sort of a simplified version of a theory, because theories are complicated. Like, if you wanted to calculate the orbit of the Earth around the sun, you couldn't use

general relativity. Nobody knows how to do that calculation. General relativity, really, really nasty. The only times we've ever been able to solve problems with general relativity are in simplified settings, like an empty universe, a universe with just a black hole in it, a universe filled with uniform dust. None of those correspond to our reality. Our reality is two complicated to solve with the full theory. And so we build a model. We can simplify the universe. We can say like, let's assume the universe is empty except for the earth and the sun. Now let's do the calculation. And we hope that the calculation is still relevant to the real universe, right? We find a simpler version, something we actually can crank on and hope that the answer is

still relevant. Or we can simplify the calculations. We can say, well, let's use an approximate version of the theory. You know, Einstein's equations for general relativity, if things are far apart and masses are not too high and they're slow moving, they reduce to Newton's theory. And so you can use Newton's theory for most of. You want to calculate whether your cannonball is going to fly over the castle walls. You don't need to use general relativity. You're going to get basically the right answer using a simpler model, right, a model of general relativity, which is just Newton's equations. And so, you know, spherical cows are a fun joke because that's the kind of thing. does this is due? We're like, well, let's replace a complex situation with a simpler situation

where the answer is basically the same. So a model is a simplification. Either you've simplified the universe or you've simplified the theory so that you can get some answers out. Yeah, and models are great. They help you decide if, you know, you're a simplification. When you do a simplification, you're making assumptions that some things don't matter that much. And so then when your model gives you an answer and you test it, you can see, oh, was I right that that thing doesn't matter that much? And, you know, ideally it's an iterative process. The model gives you a prediction you can test. You actually go out and you test it, and then you update your model as needed.

That's right. And it's important to understand that every calculation anybody has ever done uses models, uses simplifications. All of physics uses approximations. If you want to calculate how the Earth goes around the Sun, in principle, you need to include the gravitational tug from every single object out there in the universe, which is pulling on the Earth. Most of those are negligible. And some rock out there in Andromeda is really not going to change the path of the earth in a way we can measure. But in principle, it does.

So we always do approximations. It's impossible to ever do full calculations in any of our theories for any situations. So all of science is approximate to some degree. And that's where a lot of science happens is figuring out how to be clever about it. What approximations can I make so that the answer is still useful and irrelevant? And I can get this done in a PhD length of time and not be here for 10,000 years. That can often be a very painstaking part of the process, though. Like, what are my parameter estimates that are reasonable and useful?

And that can be a lot of work. That's right. And so that's what a model is. And let me say that model is used very differently in different fields. Like I talk to computer scientists and machine learning people. For them, a model is like a trained network. They talk about neural networks as my model or their boosted decision tree is a model. They use model to mean something very different than physicists do.

And I know biologists talk about like, model systems. They're studying the brain. They're doing it in mice or they're doing it in rats or they're doing it in flies. To them, that's the meaning of model. Like, which model system are you using? But when someone says to you, you know, what do you do and you say, oh, I do modeling, they know that that means that you are using equations to try to capture the dynamics of a system and are making predictions that way. So I think we use the word model in a couple different ways, one of which is model systems. Yeah. And I think that fits in because like you're using the mouse. as a model system to understand Alzheimer's because you can't and you shouldn't do experiments on humans and to use the mouse brain as a stand-in as an approximation for the human brain because you know, it's not okay to do the things to humans that you do to mice. And maybe it's not okay to do to mice either, but it's maybe more okay. I think it's the argument biologists make. Yeah, yes. Depends on who you're talking to, but I guess I'd prefer it happened on mice. Yeah. All right. And so the last term was hypothesis. We test our model by generating hypotheses.

We're saying, here's my model of the universe. I think that this interstellar comet is made of ice and CO2. Let me generate a hypothesis about what James Webb Space Telescope will see when we point it at it. And then I can compare that hypothesis to what we actually see. So the model predict something. That's our hypothesis. And then we compare it to reality in order to learn whether the model is correct or not. Yep.

Cool. So we have laws, theories, models, and hypotheses. And the last bit of Ben's question was a sort of, loaded question about Darwin's theory. I hear a lot of this discussion online about how evolution is just a theory man, and because it all happened in the past, it's not really predicting anything, it's just descriptive, and therefore it's unfalsifiable and not really scientifically valid. And I wonder if these critiques are really done in good faith. You know, these are folks attacking evolution, trying to use the language of science to undermine it, but I don't

think they really believe in the scientific process, personally. Yeah, agree. So let's talk about it. Darwin's theory is definitely a theory. I mean, it provides an explanation for how speciesation happens, right? There's lots of evidence out there that it's pulled together. It definitely qualifies as a theory. And in that sense, it's not just like some dudes' random guess, right? It's a well-established explanation for a huge variety of stuff that we see out there. What do you think? Yes. So for 150 years, we've been trying to decide if evolution through natural selection is supported by the data. And, you know, there's probably evolutionary biologists in every department that does research around the world.

And we have found results that make us think about evolution through natural selection in a different way. But in 150 years, none of us have come up with a result that's like, oh, definitely we drop this theory. So we've got 150 years of researching coming up with predictions based on this theory that are supported by future work. So, yeah, I agree with you. Yeah. And Ben asks, like, is this a predictive theory? And I think the answer is absolutely. You know, it predicts lots of things about what you should find out there in the world. You should find fossils.

You should find simpler behaviors leading to more complex behaviors. You should see real-time evolution, you know, when communities respond to changing circumstances. You should see a connection between the species that we observe and the genetic information that leads to them. This is, I think, a really powerful confirmation of natural selection is finding the sort of mechanism, the DNA, the biochemistry. that underlies all this and seeing confirmed the history of that evolution in the DNA. I think it's super fascinating. You know, we can learn things about like when communities diverged by seeing the differences in their DNA.

Yep, yep. And, you know, Darwin is clearly like the best scientist of all time. Sorry, Daniel. And so if you could be the scientist who finds the data that refutes this theory, you could replace the name Darwin, right? And so there's no... Mainstream narrative, the biologist is trying to protect. Yeah, that's right. That's right.

No, every scientist out there wants to overthrow the mainstream narrative because that's how you become a famous scientist. And also, that's what we all want to do. We want to learn the truth about the universe. We're driven by our curiosity to reveal the truth, not to support some sort of dogma. But you raised, I think, the last, maybe the most important point is the question about whether this could be refuted. So can you clearly imagine some evidence that hypothetically would undercut this theory of evolution. At this point, we have so much evidence. It's kind of hard to imagine something we could have missed

and, like, one piece of information that would refute everything. So I think at this point, if you had a finding that, like, you know, multicellular life existed before we found unicellular life, like it just popped into existence or something, we would have to look really hard at, like, have we collected all the data and all the different places? Like, because there's this mountain, of evidence and you've got this one thing that maybe doesn't fit.

But I do think that if there were evidence out there, scientists would be open to considering it and looking at it and trying to understand if that makes us wrong or if it's just a like shady corner in the room of evolution that we haven't explored yet. And we just need to move into that area instead. Yeah. And I think the question is reasonable. Like we expect theories to do more than just describe the data we've seen. We want them to generalize if they really are coming.

close to the truth, the laws of the actual universe, they should be able to predict things we haven't seen. And Ben's question is like, well, hasn't this, all this stuff happened in the past? Yeah, a lot of the stuff has happened in the past, but we haven't seen it yet. And so we can predict, like, I predict what I'm going to find when I dig into the ground. Yeah, the stuff is already there and the events already occurred. But if we haven't seen it yet, then it's fair to predict it and to treat that as a test of the theory. Yep, agreed. All right. So Ben, let us know if we answered your question about the definition of these terms and their application to Darwin's theory of the origin of the species.

Well, Daniel and Kelly, even though the classification of groups of ideas is obviously a complicated topic, I just knew that you would come up with some clear insights. Thank you very much. And it's good to hear that Darwin's amazing theories are currently being used by scientists to help both explain and predict many phenomena. I wish you all the best for your trip to Inverness, Daniel, and I hope the weather matches that in Southern California. and stay comfortable wearing that kilt.

All right, well, that was a ton of fun. As always, I learned a ton. Hopefully, the listeners learned a ton too. Please remember, you can write us at questions at danielandkelly.org. You can join us on our Discord channel. You can find us on Twitter and Instagram and Blue Sky.

Reach out to us, please. And let curiosity drive you through your day. Daniel and Kelly's Extraordinary Universe, is produced by IHeart Radio. We would love to hear from you. We really would. We want to know what questions you have about this extraordinary universe.

We want to know your thoughts on recent shows, suggestions for future shows. If you contact us, we will get back to you. We really mean it. We answer every message. Email us at Questions at Danielandkelly.org. Or you can find us on social media. We have accounts on X, Instagram, Blue Sky,

and on all of those platforms, you can find us at D and K Universe. Don't be shy. Write to us. I'm Robert Smith, and this is Jacob Goldstein, and we used to host a show called Planet Money. And now we're back making this new podcast called Business History about the best ideas and people and businesses in history.

And some of the worst people, horrible ideas, and destructive companies in the history of business. First episode, How Southwest Airlines Use Cheap Seats and Free Whiskey to fight its way into the world. the airline is. The most Texas story ever. Listen to Business History on the IHeart Radio app, Apple Podcasts, or wherever you get your podcasts. What do you get when you mix 1950s Hollywood, a Cuban musician with a dream, and one of the most iconic sitcoms of all time? You get Desi Arness. On the podcast star in Desi Arness and Wilmer

Valderrama, I'll take you in a journey to Desi's life, how he redefined American television and what that meant for all of us watching from the sidelines, waiting for a face like hours on Listen to starring Desi Arnaz and Wilmer Valdarama on the IHard Radio app, Apple Podcasts, or wherever you get your podcast. Hey there, Dr. Jesse Mills here. I'm the director of the men's clinic at UCLA, and I want to tell you about my new podcast called The Mail Room. And I'm Jordan, the show's producer.

And like most guys, I haven't been to the doctor in way too long. I'll be asking the questions we probably should be asking, but aren't. Every week, we're breaking down the world of men's health from testosterone and fitness to diets and fertility. We'll talk science without the jargon and get your real answers to the stuff you actually wonder about. So check out the mailroom on the IHeart Radio app, Apple Podcasts, or wherever you get your favorite shows.

On an all-new episode of IHeartRadios Las Culturistas, Emmy, Golden Globe and Tony Award winner Sarah Paulson spills on red carpet hacks. We saw these pictures and you're like, what is the story with this? She gets real about the inspiration behind her roles. Oh, no, there is no end to how people will behave. And she puts host Matt Rogers and Bowen-Yag on notice.

I don't think so, honey. I feel very, very triggered by this. Open your free IHeart radio app. Search Las Culturista. And listen to the full podcast now. This is an IHeart podcast.