Daniel and Kelly’s Extraordinary Universe - Listener Questions #9

Episode Date: May 1, 2025

Daniel and Kelly answer questions about space within the atom, picky parasites, and speed-of-light particles.See omnystudio.com/listener for privacy information.

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chase? Do other particles travel at the speed of light? Why is dark chocolate better than white? Biology, physics, archaeology, forestry. Thankfully, no one asked about chemistry. But whatever question keeps you up at night, Daniel and Kelly's answer will make it right. Welcome to another listener's questions episode on Daniel and Kelly's Extraordinary Universe. Hello, I'm Kelly Weiner-Smith. I study parasites and space.

Hi, I'm Daniel. I'm a particle physicist. I study particles and the spaces between them. Ah, well, one of the first questions that we have today is about balls, which makes me wonder, you know, usually when you think about scientists, be they ecologists or physicists. I'm about to make a family inappropriate balls joke, Kelly. No! No, I'm not.

Geez, Louise. I just felt like the audience was like, uh-oh, where were we? going with this. Daniel, this is a joke about sports. Oh, my goodness. Sport balls. Yeah, go ahead. Oh, my goodness. There's never been an inappropriate joke about balls and sports. You know what? I feel like you're pigeonholing me here, Daniel, and I've got a lot more range than you're giving me credit for. I'm just looking out for the audience, you know, there are kids in the backseat listening to this and I just want to make sure this joke is clean. Anyway, go ahead. Tell us about sports balls. Well, it's not even a joke. It's a question. Now you've raised all the expectations.

So my question is, you know, usually when you think about scientists, you don't immediately think, oh, wow, they're great at sports, although many of us are. So are there any sports where being a physicist would give you an advantage? Now that is a very clean question, Daniel, I'll point out. That is a very clean question, yes, very family appropriate, but not an easy question, you know, because I feel like sports don't rely on calculations. You might think, oh, you're playing baseball. ball you want to calculate the trajectory of the pitch so it gets exactly in the right spot but nobody has time for that all this stuff is intuitive you know it's all muscle memory it's amazing that your brain can do that all so fast it's got this heuristic physics engine inside of it that just like

almost instantly tells you exactly how to kick the ball so it goes exactly where you want it to go though of course it's not that easy but does being a physicist help you in any sport I don't think the answer is yes the only thing I can imagine is that being a physicist might make it more enjoyable to be a sports fan because you have the science to know, like, how difficult something is. Like, to an accelerated baseball up to 100 miles an hour, that's tough to put enough spin on a soccer ball so that it goes around the defenders. Like, that's some serious work.

So, you know, maybe if anything, it helps you appreciate the sports. I like that. I do feel like in general, science makes me appreciate just about everything about the world more. And, you know, I've talked to people who are like, well, why does it increase? your joy to know the chemical reaction that makes firefly butts glow. And I'm like, I don't know, just the fact that nature came up with that makes it even more wonderful and amazing. And anyway, science makes everything better. Science does make everything better. I was just visiting some folks at MIT and Harvard and talking to them about the value of science in society. I was talking to a young

guy and he was making the argument that science has its own value. You know, people often say science has value because it develops technology and changes our lives, that's a dot, and that's all true. But I could see that he was trying to express something deeper, which is that like science makes the universe more wonderful and our experience of it deeper and more pleasurable in the same way that like art does. You know, what value does art add to society? It adds to the experience of being human and science, though it does have the spin-offs. I think it also deepens our appreciation of the universe just in and of itself the same way that art does. And I don't know. really respect that. I think that a lot, but I think it's not often said that really science has

its own intrinsic value to humanity. Yeah, I agree. I study Gauls, which are these growths on trees and they can take lots of different shapes, but insects live inside of them. And every once in a while, you'll see an insect come out of them that's like iridescent and just absolutely gorgeous. And it's so small that if you don't get it under a microscope, you don't get to see how gorgeous it is. But nature has all of this tiny but fabulous. It is tiny but fabulous. There's so much about the world that we don't even know yet. Some of these insects that emerge, they haven't even been described by science yet. And they're gorgeous. There's just so much cool stuff happening in nature. We don't even know all about it. And the more science teaches us, the more amazing it is. All right. Although it might

get us even further off track, I have a philosophy of biology question. I've always wondered about that I now want to ask you, because you brought it up essentially. And that's why do we find nature beautiful like do you think it's possible that we could have evolved on a planet and been like eh it's kind of ugly here does every species love the vistas and the fabulousness of the critters on their planets or there are there aliens out there that are like our whole planet's kind of brown and bleh you know if you evolved on mars you'd be like wow look at the glorious red that's a great question i don't know the answer to i'm glad that we do enjoy the beauty of nature i mean would suck if we didn't need to, right? I'm wondering if there's like a reason for that, if it's

evolutionary, if it's just luck, or if the universe is just inherently beautiful, or if it's something about us that humans just like to find beauty and things. I mean, so I'm just spitballing here. I don't know that there's a solid final answer here, but I mean, I think all animals are to some extent queued into the things that other animals are doing around them because you need to make sure you don't get eaten. You need to find the food you're going to eat. So I think we're all paying attention to whatever degree our sensory systems will allow us to, but do we find it beautiful? I just don't know how we could even ask that. I mean, when you see a dog playing in the snow, do they think that's beautiful or do they think

that's fun? I think it's beautiful, how much fun they're having. That makes me happy. Yeah, it's incredible. I think this connects to the whole philosophy of consciousness discussion we had with Megan Peters recently about the nature of your experience, what it's like to be you or an alien or a dog and how little we understand about that. So maybe someday the cognitive scientists will be able to answer that question, but not today.

That's right. We'll have to get Megan Peters back on the show in a couple years, and she'll give us the answer. But in the meantime, we do have some questions from listeners that might actually have answers, or at least we're going to do our best to provide the answers, and then we're going to check in with the listeners to see whether or not we have satisfied their curiosity or just inflamed it further. And it's party time. So let's listen to the first question.

Since every atom is mostly empty space, and we know how much matter there is in the universe, how big would a ball be if we made one only out of the protons, neutrons, and electrons, and we just eliminated the empty space? Would that fit in my trunk? All right. What do you think of this question from Martin? Is this the kind of thing you think about also? Keeps me up at night. Well, you know, actually, the more you and I talk, the more interested I am in what the right way is to visualize an atom because, you know, the more we talk, the more clear it is to me that the sort of diagrams that I saw in my science textbook is no longer how we think about it. And so, well, I haven't personally thought of this

question prior to hearing it. I'm excited to hear the answer. Yeah. And I'm excited to talk about it because this is the kind of thing you hear about in popular science all the time. It's like a gee whiz fact. The atom is all filled with empty space that I think is cool to say. But if you dig into it, it doesn't really have a lot of meaning and actually misleads people into the nature of these quantum particles in the atom rather than giving them any clarity. So I'm actually looking forward to the chance to unpack it and give people a clear sense for what's going on inside the atom. Can I ask a question that will test how well I've been listening in the past? Oh, yes. Oh, boy. All right. Here we go. Historically, when I've done this, I've usually embarrassed

myself, but I'm moving forward anyway. So that's what I'm hoping for here. Yeah, well, you know, I aim to please. Okay, so in the past, we've talked about how, you know, particles aren't like points. They're like waves. And so, you know, if you're thinking about empty space, is there less empty space because it's not points? It's waves and those waves take up a lot of space inside the atom. Or, you know, you can think of those waves as filling a lot of the atom. Is that part of the answer? Or did Kelly totally miss the point again? That's totally part of the answer. You shouldn't be thinking of these particles as just point particles. In some of our calculations, it's convenient to do that. And when it doesn't matter, we do it. But when you do

zoom in on these things, it doesn't make sense to think of them as points, but little distributed wave packets. And the answer has a couple more wrinkles to it. One is like, well, what does it mean to have the size of a particle? What are we talking about here? Do particles have a surface the way he's imagining, packing these things together where the surface is touch? And then also, is the space in the atom even empty at all? And the answer is no. But let's talk about the first one because this idea of, like, taking the particles and making a ball of just them with no empty space, packing them together, really leans on your mental image of particles as balls that you could, like, squeeze together so the surfaces touch. Like if you have a pile of tennis balls, you can think about how to pack them into an object, right? So they're touching, they're squeezed in together.

And it's actually a really interesting mathematical problem, like how many spheres can you pack into a cube? it's hard and it's fascinating, it's complicated, but it requires these things to have a specific shape, right? Packing tennis balls requires them to have a surface, a well-defined point where the tennis ball ends and the new one can start. And usually you think about these things as rigid because tennis balls you could squeeze, but imagine like a perfectly rigid sphere. It has an edge to it, a surface, right? And we think about stuff as having surfaces because we live in a world where they seem to, right? You put your butt in the chair, there's a contact between the surface of your butt and the surface of the chair and your butt doesn't phase through the chair and you can say

where one starts and the other one ends right so in our classical macroscopic world this makes a lot of sense to have a surface and to pack things together and now we're trying to take that and apply it to quantum particles protons and protons and that only works if they also have a well-defined surface if you can even talk about what it means for them to have a size and I feel like the answer is that it doesn't make sense because of the wave stuff we were talking about. It doesn't make sense because of the wave stuff, but even more deeply, it doesn't make sense because the size of an object depends on how you poke it, unfortunately. So in our macroscopic world, the reason when you poke the wall, your finger doesn't go through

it is that there are forces there. There's like a mesh of atoms in the wall and a mesh of atoms in your finger, and those things are repelling each other electromagnetically, right? So that's what defines the surface, is these charged particles repelling each other. Okay, so think about an electron, right? Take an electron and poke it with another electron. What happens? Well, it gets repelled because, like, charges repel each other, right?

Well, what happens if you poke it with a neutrino? Phases right through because the electron and the neutrino don't interact. So then the point is that you can't find the exterior of the electron because it just goes through and you don't see where they bounce off? If that's where you're going, why can't you just define the outside of electron by what it does when you throw another electron at it. You could, and that works if you're just packing electrons, right? The answer depends.

And this is also even true for like macroscopic objects. Take, for example, the earth, right? Where's the edge of the earth? Well, I don't know. I mean, the atmosphere peters out and it's kind of gradual. And so like what happens if you shoot a rock at the earth? It also depends on the size of the rock, right? Does it bounce off the atmosphere?

Does it penetrate the atmosphere? Does it destroy the earth? The same thing is true if you shoot charged particles at the earth. So, like, where you would say the edge of the earth is depends on how you probe it. What finger you are using, are using a finger that's electrically charged? Are using a finger that's only charged in the weak force? Are using something that has no charge at all? Like, it depends on how you probe it, unfortunately.

And you might think, oh, this is nitpicking. Can't you just choose a definition? You can choose a definition. But I just want to highlight that, like, these quantum objects don't have a well-defined surface, the way classical objects do. Because classical objects only interact via electromagnetism. right all these other charges are essentially irrelevant that's why it seems like you have a simple crisp definition of an edge for a ball or a shoe or the wall but for quantum objects they have

all these other kinds of interactions so it really depends on how you're poking them and if we're going to pack protons and neutrons and electrons together we have all those charges at work all right yeah this stuff is complicated when you go to space conferences you could talk to space geeks for like literally days about the definition of where space starts and where earth ends or begins but okay So we've been talking about how you measure how big things are, why that's complicated. Have scientists to some extent agreed on how big any of the particles are, electrons, protons, or do we just have no definition for any of them? No, we have some definitions.

And of course, the answer is, it depends. Just like ecology. I know. You're no better. Literally there's a 20-page paper just on this question. How do we define the size of a proton? because people have come up with a bunch of different ways to do it, like shoot this thing at it and measure at what angle it starts to change its deflection,

et cetera, et cetera. There's a few different ways, and there's a whole paper trying to like harmonize them into one concept, but the answer is it's not simple to define the size of a proton. Basically, though, what you do is you shoot electrons at the proton, and you shoot it at various angles, and you see the deflection. And like at some point, basically the electron gets gently deflected,

and then suddenly it starts to get more dramatically deflected, like it's bouncing back, right? There's more of a collision there. And you can measure the size of a proton. Like, this is different than what happens with an electron. Electron is either a fundamental and a point particle, or it's just really, really small. We can't tell the difference right now. We're going to have a whole episode soon about, like, probing the inside of the electron. The electron is so small that we can't measure its size.

But the proton is definitely bigger than the electron. We can roughly measure its size and, you know, people argue about the exact definition, but roughly it's 10 to the minus 15 meters. It's a really, really, really tiny thing, yeah. teeny, teeny, tiny. Okay, so now we have a hand-wavy guess for how big a proton is, but that's only one of the three things we need to pack together. So where do we go from here? Yeah, so now trying to imagine taking these objects and trying to make a ball out of them. So, you know, Martin's question is basically take all the protons and neutrons,

of neutrons in the universe and squeeze them together with no empty space. How big is that, right? So can you pack that stuff together? Well, you can pack protons and neutrons together, right? And that's what the nucleus is, the bunch of protons and neutrons pack together, right? And so far we've seen ones with, you know, hundreds of nucleons, definitely not, you know, 10 to the 80 like we have in the universe, but in principle, you can pack these things together. And for example, the hearts of neutron stars are a bunch of these things, just all.

squeeze together. So that's definitely possible. But again, you're not packing them like tennis balls. The distance between these things is not the physical edge of them, but it's where those bonds determine they're happy to be, right? Because you squeeze them together enough and they change into something else. Like you squeeze two neutrons together, you're going to form something that's not a neutron. Like actually, at the heart of neutron stars, they're not neutrons anymore. They form this weird new state of matter called nuclear pasta, which is not nearly as delicious as it sounds, yeah. Do you physicists work hungry all the time? And is that how we came up with spaghettification and stuff like this? You know, if you read papers, but the hearts and

neutron stars, they have these figures showing these like weird sheets of matter. And they're like, this is nuclear lasagna. And if you keep squeezing it, you get like nuclear rigatoni. And like, it's really pretty hilarious. I'm on board. That sounds great. But the point is you're not just squeezing them together based on this radius. There are bonds here. And the balance of these forces determine how you could actually pack them together. Now, try to add some electrons, right? Martin wants us to squeeze in all the particles. So you might think, well, how close could you really bring electrons to these particles? Well, the answer is the hydrogen atom. That's what the hydrogen atom is. It's the closest you can bring an electron to be happy near a proton and a

neutron. It's already in its minimum state. You can't localize electrons more than that because of the Heisenberg uncertainty principle. Their really tiny mass means a small uncertainty in their momentum means a huge uncertainty in their velocity. So basically you can't bring electrons closer to protons and neutrons than they already are in most of the universe, right? And you might think, okay, but I'm doing this mental thought exercise where I'm bringing them together to touch their surfaces.

No, they don't have surfaces, right? The concept of a surface should be replaced in your mind with like the forces between these things, how happy are they to come close together? Okay, so say you squish everything together and the forces get as close as they're comfortable getting together. I know that when you answer a question, you go big or you go home. So you've done this calculation. This is just one more thing I want to say before we get there, which is I think this also

should change your view of the atom. Like if you're thinking about the atom as these tiny little dots orbiting with mostly empty space, remember that these dots are where they are because it's a balance of the forces, which means there's a lot of energy being exchanged constantly. So if you like the particle picture of forces that like the way things interact electromagnetically is by exchanging photons, you should take your mental image that's like filled with darkness between all these particles and replace it with like a blinding ocean of photons. And the center of the atom is not empty. It's a sea of frothing energy. Right. And so it's not really empty in any sense.

But yeah, let's take Martin's question at face value. We know you can't treat these things as tiny balls, but let's try, right? So ignoring the balance of the forces, let's just assume that the proton is a hard little sphere like a billiard ball with a radius of 10 to the minus 15 meters. Then you can calculate its volume, and that would be 10 to the minus 45 meters cubed roughly. Now, there's a lot of protons in the universe. we estimate there's about 10 to the 80 protons in the observable universe. We don't know how big the full universe is, but the sphere that we can observe, we know

its volume, we know its density, we know how much matter there is. So that's a number we can calculate, and that's a really, really big number. It's like nobody can hold that number in their mind. But fortunately, our mathematics can describe it. So take 10 to the 80, tiny little balls, each of which has this tiny little volume, and you pack it together and you end up with something whose volume is really quite large. It's 10 to the 35 cubic meters. And it's flabbergasting to think about because you're taking these objects whose individual volumes are 10 of the minus 45 cubic meters

and you end up with a total volume of 10 to the 35. And the reason that number still ends up so big is just the sheer number of protons in the universe is just such a big number that even though they're so tiny, they add up to make a really big ball. It's not easy to visualize 10 to the 35 cubic meters, but that's a sphere whose radius is about a trillion meters, which is like 7AU, or about 1,500 times the radius of the sun. So if you did this, took all the protons in the universe and, like, centered them in the center of the solar system,

it would be a sphere whose edge was between Jupiter and Saturn's orbit. Oh, my gosh. That was a great question, Martin. There was so much to unpack there. So no, Martin, you can't put it in your trunk. Unless Martin's got a really big truck. Yeah. It makes some really big trucks in the U.S. They do make some really ridiculously big trucks that are good for running over pedestrians or hauling the universe. All right, Martin, let us know what you think of our answer.

That was absolutely fantastic. Thank you so much. Not only did it answer my question, but it also answered 20 other questions I didn't even know I had. And my original question actually came up because it was moving apartments. So now I know that with my van, I guess I'd have to do at least four drives round trip if I wanted to move the universe. So thank you very much. And all of a sudden, you hear this. Attention passengers. The pilot is having an emergency, and we need someone, anyone, to land this plane.

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dealing with identity, struggles, and all the issues affecting our Latin community. You feel like you get a little whitewash because you have to do the code switching? I won't say whitewash, because at the end of the day, you know, I'm me. Yeah? But the whole pretending and coat, you know,

it takes a toll on. Listen to the new season of Grasas Has Come Again as part of My Cultura Podcast Network On the IHartRadio app, Apple Podcasts, or wherever you get your podcast. I've been trying to figure out the way to even phrase this question for a long time. When you have a carnivore, They tend to run down the sick, the weak, and the elderly, but argument says they'd prefer an elephant in its prime if they could get it. So my question is, parasites, how opportunistic are they?

Is there a level of health that they tend to be looking for? Do they want to go after the healthiest? Or do they tend to infect the sick, the young, and the elderly? Oh, this is a fun question. I was hoping you'd react that way. Well, you know, it has parasites in it, so I'm immediately excited about it. So glad you're excited about this question. How we understand Ricky's question?

Is he saying that carnivores tend to eat the sick and the weak and the elderly because those are the ones they can catch? But if they have their druthers, they would rather eat a big, meaty specimen in its prime because it's more food or because it's healthier and therefore could it be better food? Is that the idea? I think that is the idea. I can understand the motivation here that a carnivore probably would like to have the largest packet of food possible. And an animal that's easy to catch could be an animal that's sick. So the quality of the meat could be lower. But I think in general, animals are quite happy to go for the sick, the elderly, the babies, like whatever they're able to catch. Because, you know, taking down an elephant in his prime is dangerous for, for example, a lion that could get stomped to them. And so for a lot of reasons, I think, animals tend to go for whatever prey they can catch. And this is something that parasites actually take advantage of. So, for example, there is a tapeworm parasite called a conococcus granulosis, and it infects moose, and it lives in the moose lungs, and it replicates and produces this giant fluid-filled sack.

It's kind of like a tumor, and inside the sack there's all these baby parasites. But having a huge sack in your lungs makes it harder to run away from wolves. And so these animals get debilitated. They are sick. It's hard for them to get away from wolves. And so wolves end up catching these moose. And then they end up eating the parasites while they're eating the moose. And they get infected.

Is that good for the parasites or not good for the parasites? That is great for the parasites. So these tapeworms need to get from the moose to the wolves to complete their life cycle. Wow. Yeah, it's incredible. When they're in the wolves, they often don't seem to cause that much damage. And frequently, when you get these parasites, that have to go from prey to a predator,

and they get transmitted by the predator eating the prey. The predators, when they harbor the parasites, don't tend to be that debilitated. It seems like the parasites tend to live, for example, in their gut. They produce eggs, and when you're in what's called the definitive host, which is where you find a mate, you produce eggs that pass, like with the host feces out into the environment again. And so if that predator is eating a lot, pooping a lot,

going all over the place, then your eggs are transmitted everywhere. And so they tend to not damage this particular host in the life cycle. But then when you get into a host that needs to get eaten by the predator, you do often see those kinds of hosts getting debilitated or messed up in some way by the parasites because that facilitates transmission. So let's see if I understand these things end up in a moose and they want the moose to get caught by wolves. So they end up in the lungs slowing the moose down. Wait, hold on, nerdy question.

Plural of moose is moose. Meese? I don't know. Mises. Mooses. Moes? I'm not sure. So they slow the moose down and then the wolf eats them, gets the parasite, which is what

the parasite wants, but somehow the parasite manages to not slow down the wolf because it wants the wolf to be healthy. How does it manage to end up in the moose lungs, the meese lungs, but not in the wolf lungs? Does it know when it's in wolf or moose? It does. And I taste the flesh and like, hmm, this tastes wolfy. Well, so when it's in the moose, it makes the fur. fluid-filled sacks. I don't know how it knows that it's in the moose, but there might be some sort

of cues that tell it what host it's in. I feel like if I was injected in a random animal, I could tell the difference between a moose and a wolf, but maybe not. I really doubt it. I mean, maybe it takes longer to pass through an herbivore's digestive system than a carnivore. So maybe you could track how long it took before you were pooped out. How would you tell the difference, Daniel? I mean, they taste different, right? Like one's a predator, one's an herbivore. I'm pretty sure if you put like a moose steak and a wolf steak in front of me, I could taste the difference. Yeah, but you're not eating steaks of the different animals for comparison.

You're blind inside of an animal's gut. Yeah, but I'm eating it, right? Like, how are these things surviving? They are sort of absorbing nutrients across their skin. They're not sampling the steak. I mean, I understand they're not going to be like having a baked potato and A1 sauce or whatever, but they are interacting with their eating nutrients from this animal. So the information is there.

I don't know, parasites are sophisticated enough to tell the difference, but it's possible in principle, right? Yeah, yeah. And I think there are some cues that parasites can use to figure out what hosts they're in, but also, you know, just because of the way things often happen in nature, there's like a cycle to what host you can expect you're going to find yourself in next. Like if you are in a moose's lung, you're probably not going to end up in the moose's lungs again because moose don't tend to eat each other's lungs.

But you are pretty likely to end up in a wolf gut, for example. So it could just be first host, second host. It might not even know. Yeah, right. Just working through its life cycle. And it doesn't form those fluid-filled sacks in wolves. It's just they find mates. They make eggs and the eggs pass into the environment.

And then the moose accidentally eats the eggs. And that's how they get infected. Man, it's good to be a wolf. But I think that Ricky's question is essentially about choosing the host, right? So in this case, they debilitate the host. But do they want to start from a healthy moose or do they not care? Are they happy to get into a moose that's about to get? gobbled by a wolf anyway? Does it matter whether the moose is healthy or not?

I think Ricky's question is, do parasites try to choose the host that they end up in? I think Ricky's question is, do they care about the health of the host, the same way that carnivores are choosing the sick and the feeble and easy to catch? Do parasites care about the health of the host that they're infecting? I don't have a lot of choice. And so for a kind of caucus granulosis, I don't think it has a preference for the host that it's in as long as it can debilitate that. host and get it eaten by wolves. You maybe don't want to infect a host that is like super sick and is about to die tomorrow because after a parasite infects a host, it takes days to weeks

before it's mature enough that it could survive jumping to the next host. And so they probably don't want the host to die immediately. But in general, most parasites don't have a lot of choice because parasites aren't very mobile. You might think back to our, we called it dirtworms, but these are the geohelments, the nematodes that live in the soil. And when we were talking about that parasite, we were talking about how the hookworms need to burrow through the feet, burrow through the skin to get into their hosts. They can't be very choosy.

They, like, move away from the feces, and then they just have to wait and hope something steps on them. And so if, like, these feet are stinky, I'd rather not infect this person, like, they don't have a choice. They take what they can get. Not having a choice and not having a preference are different things, right? the way we were talking about appreciation of nature, it might be that they don't have a choice and they end up in whatever moose, but there are some moose that they're like, this is a primo

moose. Yeah, I'm really loving this one. Other ones are like, man, this moose kind of sucks. And there's some moose that probably have better immune systems than others. And so if you're going to try to infect a moose, you'd rather have the moose that's immune system isn't going to slow your growth. They don't really get like a choice, you know. They don't get like a platter with five different moose and they get to pick which moose looks the most delicious. You know, you go to the seafood store and you're like, I want that lobster. They don't get to pick. But if we invited it on the podcast, it might still have an opinion.

Sure, yeah. I mean, you know, maybe we all have opinions. But we don't have that. Instead, we have the president of the Hell Monothological Society of Washington speaking for all parasites. You know, I don't know that I get to speak on behalf of the parasites. But you are. You're telling us what they prefer. I'm telling you they might have preferences, which is hedging my best even more.

But then when we were talking about the dirtworms, we also talked about whipworms and roundworms. And they get into hosts when their eggs are accidentally consumed. And there too, they don't have a choice. Like they just get eaten by whoever they get eaten by and then they got to make the best out of the situation that they're in. There are trematodes. So these are, if you've heard of schistisomyasis or liver flukes, there are some trematode diseases that are bad in like Asia and Africa. We don't have too many to worry about here. Swimmers itch.

Have you ever heard of Swimmers It sounds uncomfortable. It is uncomfortable. So the idea with trematodes is that they typically start in snails. They often castrate the snail and they reproduce asexually. So they make tons and tons and tons of these free swimming infectious stages that leave the snail and they go off in search of something else. Swimmers itch is when you get these free swimming stages that are going off in search of a bird to infect snakes. But they accidentally hit you. And they take in what they can get.

Maybe they can't tell the difference, but they burrow into you. and then your immune system kills them almost immediately, but then you get this horrible itch afterwards because you have an immune reaction to it. For some reason, because it's called swimmer's itch, I'm imagining this itch is in a very uncomfortable place. Oh, geez, Daniel, you just keep bringing the conversation back there. But it could be there, but my colleagues and I usually get it on like our calves

because we're in salt marshes and it's, yeah, don't worry. Don't worry. That's free swimming stage of the parasite, depending on the species that you're looking at, they often have strategies to try to get closer to where their hosts usually hang out. So if they're leaving a snail and hoping to infect a fish, some of them will respond by swimming towards whatever light source you give them. So they're trying to swim up to the water surface where they're more likely to encounter certain kinds of fish.

But once they encounter a fish, they'll take what they can get. They're not choosy because literally 2,000 of these free swimming stages of tremantode called Uoploricus Californiances. It's the one that I studied for my Ph.D. 2,000 of them leave the snail every day. Like, that's how many need to be made in the hopes that some of them encounter a fish because there's a low probability game. So in general, there's not a lot of evidence of choosiness. They're not very mobile.

They don't have a chance to be choosy. But parasitoid wasps can be a little bit more mobile. So parasitoid wasps lay their eggs in some insect and then their eggs consume the inside of the insect and then burst out of it when they're done. This is, yeah, it's super creative. creepy. There's some evidence that some parasitoid wasps can tell if a, for example, caterpillar has already had eggs laid in it. And then they'll go off in search of another one because they don't want their offspring to have to compete with like older wasp babies that are already

starting to eat the caterpillar from the inside. So there's some choosiness in the more mobile parasites, but in general they don't get a chance to do much choosing. All right. So to some of the answer for Ricky, I think that there are some outcomes for the parakeets. that are better. Like if they get into a healthy host, it lasts long enough for them to do their whole life cycle dance. But they don't get choices often, unlike carnivores. They can't pick who they're going to chase after. Though if we invited them on the podcast, they might still have thoughts about where they ended up. We don't know. What is it like to be a parasite? Nobody knows. Maybe you should be president of the Hellmetological Society of Washington because you're

doing a great job speaking for parasites. No, no. I want to be a philosopher of parasitology. I don't think that exists. We just invented a new academic field today. Oh, my goodness. There's probably no funding for it, unfortunately. But I hope we're wrong about that. But let's see if Ricky would like to fund a new position for the philosopher of parasitology. And if I'm wrong, and you are a philosopher of parasitology, we want to hear from you. Write to us, please. To Questions at danielandkelly.org. And while we're waiting for that email to come in, let's see what Ricky thought of the answer. First of all, it is obviously my fault because I knew what question I asked.

And then I was like, oh, I'll listen to your answer while I'm having lunch. But that aside, which was totally on me, thank you, Daniel, for bringing it back. My real question was about preference if there were the ability to infect an, quote, unquote, ideal host. What would that look like? And I think you really got there, especially with the mobile ones, with the parasitoid wasps, which are a big thing for me as a farmer. And also, I have two useless philosophy degrees, and I'm considering pursuing this third one.

Thanks. And thank you, Kelly, for going into such incredible nerdy detail for me. Imagine that you're on an airplane, and all of a sudden you hear this. Passengers, the pilot is having an emergency and we need someone, anyone to land this plane. Think you could do it? It turns out that nearly 50% of men think that they could land the plane with the help of air traffic control. And they're saying like, okay, pull this, pull that, turn this. It's just, I can do it my eyes close.

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All right, for our next question, we have a question from Wendy. Hi, I'm Wendy from Vermont. I have a question about the speed of light. The speed of light is something really fundamental, I think, because both light and gravity waves travel at that speed. Does every force carrier travel at the speed of light? And if that's the case, it's not the speed of light, is it? Isn't it the speed of the universe?

Thanks so much. And Wendy asks a really deep, really basic question about the nature of the universe and motion at the speed of light and why do we call it the speed of light anyway, all sorts of stuff connected here, that I hear a lot of people puzzling about. and that I still puzzle about because the nature of the universe and transmission of information is not something we have fully understood, even if we do have a great mathematical framework

for describing it. So let's start from the beginning. Does every force carrier travel at the speed of light? I'm going to guess the answer is it depends. No, no. No? Is it no? We are watering down the crispness of physics today. You're right.

The answer is it depends, but it depends very precisely on. on something, which is whether the force carrier has mass. You see, things that have mass cannot travel at the speed of light, never, ever, ever. They can approach the speed of light. You can keep pushing them and pushing them and pushing them. They will asymptotically get closer and closer to the speed of light relative to something. But things that have mass cannot travel at the speed of light. It would take infinite energy. Sorry, Usain Bolt. Exactly. Keep pushing, though. Keep pushing. And for those of you out there thinking, don't things traveling near the speed of light also gain mass and become infinitely massive? The answer to that is no.

They just have infinite energy. And we have a whole episode talking about whether potatoes turn into black holes need the speed of light. Check that out. If you're interested in the question of relativistic mass. But the issue here is whether something has mass. So things that do have mass can never travel at the speed of light relative to anybody, whereas things that don't have mass are always moving at the speed of light forever. everybody. So when he asks, does every force carrier travel at the speed of light? It depends on whether they have mass. So let's quiz Kelly. What are they? Oh, no. Some force carriers. Uh, the electromagnetic field. Yeah. And what is the particles associated with that? Electron? No, the photon. Foton. Yeah, that's what I said. Yes. So the photon is the particle that transmits the electromagnetic force. Like when two electrons are repelling each other, what's happening there? Well, electrons cause ripples in the the electromagnetic field because they have a charge and check out our episode on week

hypercharge to get like a deeper understanding of like what charge is but essentially it's a coupling between two fields and so two electrons nearing each other are both causing these ripples and the electromagnetic field and those ripples push on each other and so you can think about it from the field perspective or you can think about it from the particle perspective and say those ripples in the electromagnetic field those are photons and so what's happening when the electrons come near each other is they are exchanging photons that's what's meant by a force carrier. The particles associated with the field that transmits that force.

So for the electromagnetic force, it's the electromagnetic field and the force carrier is the photon. And photons, they are massless. And so they do move at the speed of light. Now, other forces have different fields and different force carrier. So, for example, the strong force. Is that the one with the colors? Yes, exactly. The strong force, the charge there is not a plus or minus. It's a red, green, or blue. which is really weird. And there's a bunch of glue-on fields, has eight glu-on fields,

and each field carries two colors, not just one. So it can be like red, anti-green or something crazy. And these gluons are also massless. So gluon fields transmit information at the speed of light as well. So that's two forced carriers that do travel at the speed of light. And gravitational waves also move at the speed of light. Now, gravitational waves,

not technically a force carrier. There are ripples in the gravitational field created by the acceleration of masses. But information in gravity does travel at the speed of light. And we don't know what a force carrier is for gravity because we don't have a theory of quantum gravity. So we don't know, like, are there gravitons, et cetera, et cetera. But gravitational waves definitely travel at the speed of light. But other force carriers do have mass. So for example, the weak force is all messed up because the Higgs goes on.

The Higgs comes in and it makes the W and the Z have mass, whereas the photon, doesn't makes a big mess of the weak force. So these things are quite massive. I'm just going to go ahead and interject that I'm not the one who added fuzziness to physics. It was Higgs. Yeah, it was Higgs. Go ahead. Tell me more about this. Yeah. So the W and the Z bosons are really quite massive. The W's mass is like 80 times the mass of a proton. The Z is like 90 times. These are super duper massive particles. And it's one reason why the weak force is so weak because its force carriers are so massive. They don't travel at the speed of light, and they're very unstable. They decay very quickly into other stuff.

And so these force carriers, the W and the Z, do not travel at the speed of light. So it depends on whether they're massless. Okay, so we've answered the first part of the question then. No, every force carrier does not travel at the speed of light. Okay, so where do we go from there? Yeah, and so she's asking, like, why do we call it the speed of light? If other things travel at that same speed, it's not special to photons. And she's right.

Photons are the first thing we saw that was massless that traveled at the maximum speed of the universe. And so it really is the maximum speed of information in the universe. And all massless things can travel at this mass of speed and have to travel at this massless speed. So, yeah, it's the speed of information or the speed of causality or the speed of the universe. You could also call it the speed of gluons, right? We call it the speed of light because light was the first thing we discovered that mood at this speed. So it's just sort of historical. But it's also really fascinating, like, philosophically, why the universe has a maximum speed

and why it's this number and why it means that all observers have to see massless things moving at this speed. So first of all, I think I prefer speed of the universe. I don't know. That sounds more epic. But why? Yeah. Why is this the speed of the universe?

Yeah, nobody knows currently. We don't even know if there is an explanation. You know, one possibility is that it comes out of the way space is built. You know, space could be quantized. It could be a bunch of pixels, and these pixels could interact with each other through quantum entanglement, and that's how space is woven together from a bunch of, like, little space pixels, and that the speed of information is connected to that entanglement, and so it could come out of some deeper understanding of space.

That's just a speculation. Currently, we don't know. Currently, it's just a number that we measure, and it could be anything. It could be twice as big. It could be half as big. And it's an important number because it really determines what it's like to be in the universe. Like on one hand, having the speed of light be as small as it is relative to the size of the universe means we can't see that far.

Right. Like this whole regions of the universe, we can't even see because in the 14 billion years of its history, life hasn't had time to get here. Imagine if the speed of light was a thousand or a billion times higher. We could see so much further into the universe. and the information in our neighborhood wouldn't be as out of date. That would be amazing. In the other hand, there'd be downsides also.

Like, the fact that the speed of light is not infinite protects us from alien death rays, for example. You know, if an alien shoots a death ray at Earth from Andromeda, that's a few million light years away. We got a few million years before it comes here. So that's cool. If the speed of light was like instantaneous or much, much higher, then we would be vulnerable. to alien death rays in a much bigger volume. It sort of isolates this in a protective way. Now we have time to get our affairs together.

Yeah, exactly. Exactly. Talk to your parasites, get everything in order. Are your parasites in your will? Have you figured all that out, Kelly? You know, I don't have a will yet. Oh, no. Get on that.

That's like literally on my to-do list for this week. But I'll make sure someone good gets my parasites. Yeah. So it's really fascinating. We don't know the answer. It's possible that the value of the. speed of light is determined by some deeper physics we don't know yet, or it's possible it's just like a random number. And when the universe cools and settles, it turns out to be this

number. And in the multiverse, different universes have different values of this number. We don't know the answer to that. But it is fascinating. It's something I hear a lot of people sort of misunderstanding when they're writing to me and asking questions about it. You know, for example, there's this constant question like, what does it like to be a photon? You know, do photons experience time? in the universe that we've talked about, that I think reveals a sort of misunderstanding about the nature of these massless objects and their velocity. Well, let's see if you've cleared this all up for Wendy. Thank you so much for your lucid and straightforward answer about the speed of force carriers.

I also appreciated your elaboration on the speed of the universe, why it is what it is, which is also a question I've pondered. Of course, I'm left wondering about why the weak force is so different from the strong force of gravity and electromagnetism, why it froze out of the electric weak force as the universe cooled. But that's another question altogether. Thanks again. All right. Well, thank you so much to everyone who submitted questions, and we are looking forward to hearing your questions.

You can write us at Questions at Daniel and Kelly.org, and we will definitely write you back. either with an answer if we know it right away or if you've kind of stumped us or it's a question we get often we'll answer it on the show. And please write us family-friendly questions so that Kelly doesn't have to cringe when I'm responding to them.

You know, Daniel, I feel like you took family-friendly topics and sort of morphed them into something not family-friendly, so I don't think our listeners can win. I have a special gift in that area. You would have thought that the co-host with the last name, Weiner-Smith,

would have that gift. There you go. That was you, and that was all you. We're a good team. All right, everybody, until next time. Thanks for listening. 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. 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. Why are TSA rules so confusing? You got a hood of you. I'm take it off. I'm Manny. I'm Noah.

This is Devin. And we're best friends and journalists with a new podcast called No Such Thing, where we get to the bottom of questions like that. Why are you screaming? I can't expect what to do. Now, if the rule was the same, go off on me. I deserve it. You know, lock him up.

Listen to No Such Thing on the IHeart Radio app, Apple Podcasts, or wherever you get your podcast. No Such Thing. I'm Dr. Joy Hardin Bradford, host of the Therapy for Black Girls podcast. I know how overwhelming it can feel if flying. makes you anxious. In session 418 of the Therapy for Black Girls podcast, Dr. Angela Nielbornet and I discuss flight anxiety. What is not a norm is to allow it to prevent you from doing the things that you want to do, the things that you were meant to do. Listen to therapy for Black Girls on the IHeart Radio app, Apple Podcasts, or wherever you get your podcast.

Betrayal Weekly is back for season two with brand new stories. The detective comes driving up fast and just like screeches right in the parking lot. I swear I'm not crazy, but I think he poisoned me. I feel trapped. My breathing changes. I realize, wow, like he is not a mentor. He's pretty much a monster. But these aren't just stories of destruction.

They're stories of survival. I'm going to tell my story and I'm going to hold my head up. Listen to Betrayal Weekly on the IHeart Radio app, Apple Podcasts, or wherever you get your podcasts. Hi, it's Jemma Spag, host of the Psychology of Your 20s. This September at the Psychology of Your 20s, we're breaking down the very interesting ways psychology applies to real life, like why we crave external validation. I find it so interesting that we are so quick to believe others' judgments of us and not our own judgment of ourselves.

So according to this study, not being liked actually creates similar pain levels as real life physical pain. I'll learn more about the psychology of everyday life and, of course, your 20s, this September, listen to the psychology of your 20s on the IHeart radio app, Apple Podcasts, or wherever you get your podcasts. This is an IHeart podcast.