
Birds navigate using Earth’s magnetic field, but scientists still don’t know how they actually sense it.
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Host (Noam Hassenfeld)
You know that feeling when too many things fall through the cracks?
Ed Yong
Monday.com was built for that gap, the
Host (Noam Hassenfeld)
AI work platform where people and agents work side by side to deliver more together. Create your first Monday agent today@Monday.com. there's this bird that kind of blows my mind. It's called the bar tailed godwit and it migrates from Alaska all the way to Australia or New Zealand. A few years ago, scientists put a tracker on it and they found that it flew for 11 straight days. So over 8,000 miles. And it was just in the air the whole time, flying over the Pacific Ocean. Scientists used to think birds were using the sun or the stars or some kind of vague, undefined instinct. But it seems like birds are also sensing Earth's magnetic field. They're sensing magnetism. Magnetism is this fundamental force of the universe that we can't see or feel, but it's powerful enough to shape stars, it protects planets, it moves compass needles, and somehow it guides birds across entire oceans. But magnetoreception is the only sense where we don't know what part of the body is doing the sensing. One researcher called it the holy grail of sensory biology. I wanted to figure out how much we don't know about all this. How much is still unexplainable. So I called up Ed Yong. Ed's one of the best science writers working today. He won a Pulitzer Prize for his work covering Covid and public health during the pandemic. But more recently, he wrote a very different kind of book. It's called An Immense How Animal Senses Reveal the Hidden Realms Around Us. It's about birds that might see magnetism, dogs that can smell time, fish that can sense electric fields and all the ways animals live inside realities we can barely imagine. And if we grapple with that, if we really try to take that understanding seriously, it might change the way we see ourselves. Hi, Ed. Thanks for coming on the show.
Ed Yong
Hi, thanks for having me.
Host (Noam Hassenfeld)
So you want a Pulitzer for your reporting? During the pandemic, how'd you get into animals?
Ed Yong
It's actually the other way around, really. I was into animals for as long as I was into anything. As a child, I went to zoos and watched nature documentaries and read books about wildlife that were way too advanced for me, but had very beautiful pictures. So I've loved the natural world for my entire life.
Host (Noam Hassenfeld)
So you wrote this book called An Immense World. It's all about the various diverse ways that animals perceive the world we live in. I really want to focus on birds in particular.
Ed Yong
Great.
Host (Noam Hassenfeld)
How did scientists figure out birds weren't just using the sun or weren't just remembering where to go? Like, how did they realize this was an actual sensory system that could sense magnetism?
Ed Yong
Yeah. So this goes back to the 1950s, when some German ornithologists were watching birds at the time when they're about getting ready to migrate. Birds show this restlessness, this anxiety, that in German is called zugenruge. Okay. And these scientists looked at these birds and realized that their restlessness wasn't just random. They tended to hop in a particular direction. Like, they had this sort of sense of which direction to go in.
Host (Noam Hassenfeld)
They're, like, hopping in the direction that they kind of want to migrate.
Ed Yong
Totally. Yeah. You could put them in a cage. You could put the cage in a room that's completely isolated. So dark, no view of any landmarks. You can't see outside, much less the sun or the stars. And the birds are still hopping in basically the right direction. And then you can take wires and create an artificial magnetic field around the bird that basically flips the Earth's natural one. And now they start hopping in the opposite direction.
Host (Noam Hassenfeld)
Ah, so you can, like, control which way they want to go by controlling the magnetic field around them.
Ed Yong
Yes, exactly.
Host (Noam Hassenfeld)
I think I want to just take a second to make sure I understand what exactly a magnetic field is. I don't know if I could define that exactly for you.
Ed Yong
I mean, I'm not sure I can define it for you exactly either. This is actually a very difficult thing to do. But I think, you know, the vision of magnetic fields that we get in a high school textbook will do for these purposes. So you have a bar magnet with north and a south pole, and you have lines that curve out from one pole and go back to the other. And these lines represent this field around the magnet that magnetic objects are influenced by. It just so happens that the entire planet is basically one of these magnets. The Earth has a solid iron core, and it's got a churning Layer of liquid iron around that, and that turns it into basically a gigantic bar magnet with the same kind of field lines enveloping it. And so when I hold a compass and look at it, the needle in the compass is being influenced by the planet's field. And that's how we can tell a direction. Now it seems that animals migrating, songbirds, sea turtles, possibly giant whales, many more. A lot of the ones that do these arduous long distance migrations have these inbuilt biological compasses.
Host (Noam Hassenfeld)
I guess. I guess my question then is like, I'm looking at you with my eyes, Right. I'm listening to you with my ears.
Ed Yong
Yep.
Host (Noam Hassenfeld)
What are birds sensing magnetism with?
Ed Yong
Great. Also, I love the way that you're asking these questions with a slightly confused tone. That is the right tone.
Host (Noam Hassenfeld)
Just to be clear, I have no idea how to even like wrap my. I'm gonna let you have the magnetic field thing without asking like 15 more questions on it. Yes. But yeah. What is in the burn that is getting them this information?
Ed Yong
The short answer is we don't know.
Host (Noam Hassenfeld)
Perfect.
Ed Yong
And that's kind of astonishing. Just take vision. My eyes. See, I can tell you exactly which molecules inside my eye are responsible for reacting to light and transforming that into an electrical signal that goes to my brain. That's all really worked out.
Host (Noam Hassenfeld)
Right.
Ed Yong
We don't have that for magnetoreception. And there are many reasons for that.
Host (Noam Hassenfeld)
1.
Ed Yong
One of the reasons is that with light, the stuff that we see, we know that light is blocked by living matter. And so any organ that detects light should be on the surface of the body or, you know, connect exposed to it by some kind of hole. The problem is that magnetic fields permeate living matter.
Host (Noam Hassenfeld)
Right.
Ed Yong
So they just go through my body and they're not impeded by skin or bone or anything like that. And so a sensor that detects a magnetic could be absolutely anywhere. It could be in one place, it could be, say, in a bird. It could be in their head, could be in their eye, could be in their butt, could be in their wings.
Host (Noam Hassenfeld)
Like we just don't even know where to start looking is what you're saying.
Ed Yong
Totally. One scientist described this to me as looking for a needle in a needle stack. And I think that beautifully conveyed the challenge here. A lot of our intuitions about how sensing works just doesn't really apply here. And the other problem here is that theoretically you shouldn't be able to sense a magnetic field. Like, they're really, really weak. So right now the molecules in my body are Just kind of jiggling about on their own. And those tiny little movements pack billions of times more energy than the Earth's magnetic field. And the idea that something biological, something alive, should detect that is kind of preposterous. It's why, for a long time, scientists didn't believe that this was even possible.
Host (Noam Hassenfeld)
It's interesting, because my instinct would be like, okay, maybe they aren't sensing magnetism then. But we have pretty good evidence that if you flip the magnetic field, they hopped in a different direction. They definitely are sensing magnetism. We don't know what the organ is. Do we have any guesses?
Ed Yong
Yes. Yeah, we have three reasonable guesses. So, one involves this iron mineral called magnetite. And the crystals of magnetite basically work like a compass needle. So just picture that you have cells with these crystals inside them that are moving in depending on their relationship to the Earth's magnetic field.
Host (Noam Hassenfeld)
Almost like an inbuilt compass or something like that.
Ed Yong
Almost like an inbuilt compass.
Host (Noam Hassenfeld)
Okay.
Ed Yong
The second involves electromagnetic induction. So as a bird flies, its inner ear has these canals full of fluid that conduct electricity. And as those move through the planet's magnetic field, they get small electric currents induced in them. And maybe the bird can then sense those currents. We know that there are animals that can sense electric fields. That's a little bit easier than sensing the really weak magnetic field.
Host (Noam Hassenfeld)
Got it. Okay. So it could not be magnetite.
Ed Yong
It could be induction.
Host (Noam Hassenfeld)
Induction.
Ed Yong
And then the third possibility, arguably are some of the strongest evidence backing it up. But it's also the most complicated. It kind of involves quantum physics. And I don't think we should go there, but I can explain it a bit more specifically.
Host (Noam Hassenfeld)
I never think we should go there. Let's just.
Ed Yong
Right, okay.
Host (Noam Hassenfeld)
Stay away.
Ed Yong
Let's imagine you've got a pair of molecules, okay, that are locked in a partnership. Think of two dancers.
Host (Noam Hassenfeld)
Okay.
Ed Yong
When light hits those molecules, when a spotlight shines on the dancers, they start getting excited. They take hold, they begin the dance. And when they're in that excited state, they can be influenced by even something as weak as the planet's magnetic field.
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Host (Noam Hassenfeld)
Okay.
Ed Yong
And so by sensing those chemicals, we can get a sense of where the bird is relative to the planet. The chemicals in question exist in a bird's eye. And this raises the really, really tantalizing possibility that birds might actually be able to see the Earth's magnetic field.
Host (Noam Hassenfeld)
Wait, hold on, hold on. Okay, hold on. What does that. I don't even have a good question. What does that mean? What would that be.
Ed Yong
It's good that you don't have a good question because I don't have any answers. So it's a match made in heave. Look, we really don't know. We don't know which of these ideas is correct. And even if this one is correct, we absolutely don't know what it might be like. I like to imagine maybe it's a kind of heads up display. Like maybe part of the bird's visual world has a different quality to it, maybe in terms of brightness or contrast or something that allows it to. Um. No, over there, that's where I should go. But I really want to stress this is completely made up. All of these possibilities are on the table. What does magneto reception feel like to a bird? We have absolutely no idea. And I think that's kind of wonderful because it does open up the space to just freely imagine. Right. Like when it comes to things like vision, we have a good start because we, most of us do it, but with magnetoreception it's so strange, it's so alien that you really have no choice but to just let your mind go wild.
Host (Noam Hassenfeld)
Okay. I mean, you know where I have to go now? Cause I know you're saying that we don't know and we can't know right now, but if we can freely imagine for a second, I don't know, what could that mean to see magnetism? Like if there are magnetic field lines, would that mean that everything a bird sees is like striped? How can we even try to conceptualize what this kind of sense would be like for a bird, what its internal experience could be?
Ed Yong
Yeah, with great difficulty. Right. Like you'll notice that these hypotheses that I've put forward really involve converting magnetic fields into things that we're more familiar with. Like something to do with vision or something to do with touch. Right. And I think that's part of the challenge. It's not only that we don't have the sense, but we also really have no way of talking about it.
Commercial Narrator
Yeah.
Host (Noam Hassenfeld)
We don't have words.
Ed Yong
Right. We don't have a vocabulary. You know, with vision we have brightness and image and dimming and all of this rich descriptive language. We have that for smell.
Host (Noam Hassenfeld)
Yeah. It'd be like asking what a song smells like or something.
Ed Yong
Right. Like we just don't even have the starting place for describing what a bird might sense on its way. I think that's kind of wild. Right. Because here you, you know, you've talked about bar tailed Godwitz, but like probably all migrating Birds are using this to some extent. You know, it's the summer. Like I just spent two months watching this Glori parade of species flying past me. In a couple of months, I'll see them coming back down south in the other way. They're all probably detecting magnetic fields. This sense that is so omnipresent around us we can't describe. We find it really hard to study. We don't understand. We just know that it exists, which is kind of great.
Host (Noam Hassenfeld)
So what is it actually like to be a bird or a dog or a bat? We'll give it our best shot in just a minute.
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Host (Noam Hassenfeld)
You should be Professor X and you should be Magneto. So this. This is really why I wanted to talk to you more. More than the birds, more than magnetoreception. It's because of what we can get by imagining how all kinds of animals experience the world. And this is what an immense world in large part is about. But I wonder if you can tell me about the concept of an Umwelt. This is sort of a central theme running through your book. What does that mean? Why is that relevant here?
Ed Yong
Yeah, so Umwelt is just German for environment, but in the context of animal senses, it has very particular meaning. So my Umwelt is the part of the world that I can perceive. It is that unique blend of sights and smells and textures and sounds that I have access to. And the. The cr. The crucial thing here is that it's going to be totally different if I was another animal or if I was another individual. So if we had a bar tailed godwit here sitting in my lap, its Umwelt would be radically different from mine. It would be able to sense the Earth's magnetic field. I can't do that. It would see colors that I can't sense. It would probably smell things that I can't sense. It would feel the air currents around the room in a way that I can't feel. And even though we share the same physical space, we would have a very different experience of that space. And that's what the Umwald concept is. I happen to think it's one of the most delightful concepts in biology because it hints that, you know, even in these places that we feel like we understand, we're really only getting this tiny fraction of all there is to get.
Host (Noam Hassenfeld)
Yeah. I wonder if you can take me through a couple of your favorite umwelts that really illustrate just the expansive diversity of perceptual worlds that animals have.
Ed Yong
Yeah, sure. So birds see a much wider range of colors than we do. So they see ultraviolet, which is a color we tend not to see. And this massive catalog of ultraviolet blended in with other colors and kind of a cocktail of purples and similar hues. This means that when they're looking out in the world, they are seeing things that we absolutely do not. Patterns on flowers, on their own feathers that we miss because we don't live in a world that's quite as colorful. When you go into the water, you have fish that produce their own electricity, their own electric fields, and can sense the electric fields given off by each other and by other living things. You have seals that can detect the turbulent currents left behind by swimming fish that basically act as traps left behind in the water. Closer to home, my dog typo senses this world of smells that I am absolutely not privy to, like when we go on walks. This is Made clear to me by the way he intently sniffs the sidewalks and pavements that look completely nondescript to my eyes and yet are bursting with interest to his nose.
Host (Noam Hassenfeld)
And with dogs, I mean, I've some of this reporting on the show that, you know, based on how much of a smell has faded, the dog can almost smell time.
Ed Yong
Right.
Host (Noam Hassenfeld)
Which is something that is hard to wrap my head around.
Ed Yong
Yeah. Smells linger in a way that a lot of other stimuli don't. And because of that, when a dog is sniffing, it's sort of sniffing into the past and a little bit into the future. It's anticipating things that are going to happen based on smells that have drifted in its direction. And, you know, I love thinking about that, like the different nature of the different senses and what your experience of the world is like if you have a different primary sense to the vision that most humans rely on. Because I think that as much as I don't think like this, I think there are a lot of people who really think that humans are the shit, you know, that we are the great species.
Host (Noam Hassenfeld)
We've never messed up.
Ed Yong
We're doing great guys. We're doing it, you know, that for many reasons that are understandable, our intelligence, the technology at our disposal, that we really are at the top of this ladder of being. You know, that's an idea that dates back to Aristotle, millennia ago. But I think that the Umwelt idea is very equalizing. It's a little bit dethroning. It's humbling. It shows that for all of those things, you know, we are still missing out on so much.
Host (Noam Hassenfeld)
Yeah. I mean, I think about this line from Wittgenstein, I think he said something like, if a lion could speak, would we understand him?
Ed Yong
Right.
Host (Noam Hassenfeld)
And you know, there's all this work being done on like translating whale song or trying to communicate with animals, as if the way to communicate is just to convert the noises they make into the letters that we use.
Ed Yong
Yes, yes. Thank you. Right.
Host (Noam Hassenfeld)
And it does feel like there's just. There's a lot bigger differences than just
Ed Yong
a lot bigger differences.
Host (Noam Hassenfeld)
Translation, you can't Google Translate the whales or it'll be harder than we think.
Ed Yong
Thank you. Right. I think thinking about interspecies communication as just a matter of building a sufficiently advanced dictionary is the wrong way of thinking about it.
Host (Noam Hassenfeld)
Yeah.
Ed Yong
Because the deep mystery about the Umwelt idea is how does another animal see, perceive the world? What does it feel like to be a bat, in the words of Thomas Nagel, a philosopher, or a bar tailed Godwin or my dog or anything. And I think fundamentally, that is an unanswerable question.
Host (Noam Hassenfeld)
Yeah.
Ed Yong
There is always going to be this chasm, this divide between my subjective experience of the world and yours or that of another species. And that's okay. I think learning to sit with that unknowability and that that discomfort of uncertainty is a big part of why I love this topic and why I love this idea. Even if you know that you won't get the answer, it's the effort that matters and the effort that we should still make.
Host (Noam Hassenfeld)
Yeah. I mean, it does make me feel humble in the face of all of these species that we share the world with. And I think. I don't know, it also makes me think about you and me and every person I come into contact with. Because, like, if this is the case with us and animals, you know, my friends and I, my family and I, my coworkers and I, we must be experiencing radically different versions of the world. And if we can accept at a certain level that we kind of are all experiencing something different, I feel like that humility has to extend to our relationships with each other.
Ed Yong
Yeah, you're absolutely right. If you do that, if you flex those muscles, you do start extending that to other people as well. And as well you should. Because we all know that we are different from other people. Right. We have different beliefs, values. But the Umwelt idea says that at a very, very fundamental level, simply the information that we can wrest from the world, like the things that we perceive in our surroundings, even that is different. And I think it's a great base for thinking about how different we are from other people, trying to empathize with them. It's one thing to gawk and be amazed at bar tailed godwits and bats and dogs and even ticks. But I really hope that the values in the book help us be better people with other people, too.
Host (Noam Hassenfeld)
If you want to see this episode on video, head over to Netflix. This episode was produced by Valerie Shenkman and me, Noam Hassenfeld. It was edited by Joanna Solotarov. Our video editors are Shelby Smith and Alex Coles. Our animator is Karim Correa. Our fact checker is Melissa Hirsch. Our studio engineers are Davon Howard and Joe Nebras. Mixing and sound design by Christian Ayala. Music from me. Meredith Haddonot runs the show. And Bird Pinkerton watched as Flapton shaved down the sides of the guitar, pulling small pegs out from a pouch along his waist and hammering them in. I still remember when I first made this for Platty, flapton said. She was the one that gave me the courage to fight back. Thanks, as always, to Brian Resnik for co creating the show with Bird and me. And thanks to listener Daniel for writing in with a team I missed the Anaheim Ducks, formerly the Mighty Ducks, a team I had forgotten about when I asked about teams named after works of art, especially Golling, because the Ducks are named after one of the greatest works of modern cinema. Love listeners who fact check. If you have thoughts about the show, we'd love to hear from you. Please email us@ unexplainableox.com or if you'd like to support this show, join Vox. Become a Member just go to vox.com members and if you signed up because of us, let us know. Unexplainable is part of the Vox Media Podcast Network and we'll see you right back here next time.
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Vox | Host: Noam Hassenfeld | Guest: Ed Yong | August 3, 2026
This episode of Unexplainable dives deep into the mysterious sensory world of birds, centering on magnetoreception—the ability of birds to sense Earth's magnetic field. Host Noam Hassenfeld speaks with acclaimed science writer Ed Yong about the science and wonder behind this "hidden world." They explore how birds might be perceiving forces that humans cannot even imagine, what this teaches us about animal senses, and how recognizing these differences can foster more humility and empathy—not just toward animals, but toward each other.
"Magnetoreception is the only sense where we don’t know what part of the body is doing the sensing. One researcher called it the holy grail of sensory biology."
(Host, 01:57)
"The short answer is we don't know."
(Ed Yong, 07:21)
"Let's imagine you've got a pair of molecules...when a spotlight shines on the dancers, they start getting excited...and when they're in that excited state, they can be influenced by even something as weak as the planet's magnetic field."
(Ed Yong, 11:01)
"Part of the challenge is...not only that we don't have the sense, but we also really have no way of talking about it."
(Ed Yong, 14:20)
"My Umwelt is the part of the world I can perceive...the crucial thing here is that it’s going to be totally different if I was another animal or another individual."
(Ed Yong, 18:23)
"When a dog is sniffing, it’s sort of sniffing into the past and a little bit into the future."
(Ed Yong, 21:24)
"The deep mystery about the Umwelt idea is how does another animal perceive the world?"
(Ed Yong, 23:32)
"Learning to sit with that unknowability and that discomfort of uncertainty is a big part of why I love this topic."
(Ed Yong, 23:51)
This episode artfully explores the frontier of animal senses, focusing on bird magnetoreception—a powerful but almost wholly mysterious sense. Through clear stories and explanations, Ed Yong and Noam Hassenfeld reveal not just gaps in scientific understanding, but the profound limitations of human perception. By embracing the limits of what we can know, the conversation calls for humility—not only toward animals, but toward fellow humans whose realities may be more different from our own than we usually recognize.
For anyone curious about how science confronts the unknown, or anyone looking to feel a little more wonder and humility about the living world, this episode richly delivers.