Quantum Birds

Summary

Radiolab Episode Summary: "Quantum Birds"

Radiolab, hosted by Lulu Miller and Latif Nasser, dives deep into the intriguing world of migratory birds and the quantum mysteries that enable their remarkable navigation abilities. In the episode titled "Quantum Birds", released on February 14, 2025, senior producer Annie McEwan takes listeners on a captivating journey from field research to groundbreaking scientific discoveries.

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1. Fieldwork at Hawk Mountain Sanctuary

Annie McEwan recounts her expedition to Hawk Mountain Sanctuary in Pennsylvania, where she joins a team of volunteer researchers aiming to tag northern saw-whet owls—a crucial step in understanding their migration patterns.

[01:26] Annie McEwan: "I was there to join a group of volunteer researchers to wait in the cold and the dark, hoping to catch some owls."

The team sets up delicate nets and uses recordings of owl mating calls to attract these elusive birds. Despite initial setbacks with no owls being caught in the first two hours, perseverance pays off.

[05:00] Annie McEwan: "There are an owl. There's two of them... I could see these two tiny bundles of brownish white feathers caught out of the air."

2. Discovering the Owl’s Eye

Upon successfully capturing the owls, Annie and her team observe a fascinating anatomical feature—the exposed inner structures of an owl's eye. This observation becomes a pivotal moment, linking the physical characteristics of owls to the quantum mechanics underlying their navigation.

[06:16] Scott Widensall: "Gray thing you see is actually the back of the eyeball."

Annie is particularly mesmerized by the deep ear holes and the intricate inner workings of the owl’s eye, which hint at a sophisticated biological mechanism at play.

3. The Enigma of Bird Migration

The episode delves into the longstanding biological mystery: How do migratory birds navigate vast distances with such precision? While various theories exist—ranging from using the sun, stars, and even the Earth's magnetic field—none fully explain the accuracy of their journeys.

[08:15] Annie McEwan: "How does a little migratory bird leave its nest, say, in Alaska, and without compass or map, manage to arrive on the same branch of the same tree in a backyard in New Zealand, year after year after year?"

4. Magnetoreception Hypotheses: Magnetite vs. Radical Pair

Historically, scientists believed that birds might use tiny magnetite crystals in their beaks to sense the Earth's magnetic field. However, this theory faced challenges, particularly regarding how such weak magnetic signals could influence the bird's brain.

[10:27] Latif Nasser: "Yeah, it's like 10 to 100 times weaker than a fridge magnet."

5. Quantum Mechanics and Radical Pairs

Enter Klaus Schulten, a German physicist from the 1970s, who proposed a more radical theory rooted in quantum mechanics. Schulten introduced the concept of radical pairs—pairs of entangled electrons whose spins could be influenced by the Earth's magnetic field, potentially acting as a biological compass.

[14:30] Annie McEwan: "So the story of the deep sci fi sounding stuff actually starts in the 1970s with a guy named Klaus Schulten."

Despite initial skepticism and rejection from mainstream physics journals, Schulten's hypothesis gradually gained traction as further research underscored its viability.

6. Breakthrough with Cryptochrome

Fast forward 22 years, and the collaboration between Schulten and his graduate student, Thorsten Ritz, reignites interest in the radical pair mechanism. Their research identifies a molecule called cryptochrome in the eyes of migratory birds, which facilitates the formation of radical pairs when exposed to light.

[25:32] Annie McEwan: "Thanks in part to Morrison's work, we now know that there is a molecule... that can do this radical pair thing when it's hit by a photon of light."

7. The Quantum Compass Explained

Annie provides a simplified yet vivid explanation of how radical pairs function as a quantum compass:

1. Photon Interaction: A photon of light strikes the cryptochrome molecule in the bird's eye, creating a radical pair by separating entangled electrons.
2. Magnetic Sensitivity: These entangled pairs become highly sensitive to the Earth's magnetic field, altering their spin states based on the field's orientation.
3. Chemical Signals: The variation in electron spins leads to chemical changes that send signals to the bird's brain, informing its navigation.

[26:02] Annie McEwan: "A bird is flying at night under a blanket of stars... the photon of light hits the bird in the eyeball and it knocks an electron away... they still remain entangled."

8. Visual Perception of Magnetic Fields

One of the most fascinating aspects discussed is the possibility that birds "see" the Earth's magnetic field. This vision is hypothesized to appear as a subtle shading or a distinctive spot, varying in intensity as the bird changes direction.

[31:03] Annie McEwan: "The bird is not only sensing the Earth's magnetic field. It's actually seeing it."

While the exact visual representation remains a mystery, the theory suggests that the radical pair mechanism provides birds with a direct, visual sense of their orientation relative to the Earth's magnetic forces.

9. Reflections on Quantum Biology

Annie reflects on the profound connection between quantum physics and biological processes, expressing awe at how such minuscule particles can influence the grand navigational feats of birds.

[33:05] Thorsten Ritz: "It's some kind of landmark, like bright or dark spot or blue spot."

10. Conclusion and Acknowledgments

The episode culminates with heartfelt acknowledgments to the numerous contributors, researchers, and institutions that made this deep dive into quantum biology possible.

[37:54] Latif Nasser: "This episode was reported and produced by Annie McEwan... edited by Becca Bressler."

Annie also shares her gratitude towards the Hog Island Audubon Camp, Hawk Mountain Sanctuary, and the Cornell Lab of Ornithology, highlighting the collaborative effort behind such scientific explorations.

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Notable Quotes with Timestamps

• Annie McEwan [00:43]: "Listener supported WNYC studios."
• Scott Widensall [01:44]: "So I'm gonna be dryly scientific here and describe northern saw-whet owls as cosmically cute birds."
• Annie McEwan [05:27]: "And we put a little leg band with a nine digit unique serial number on their leg."
• Annie McEwan [06:32]: "I couldn't believe it. That was the coolest thing I've ever seen..."
• Annie McEwan [14:03]: "And as weird as it sounds, there is one of these little quantum facts of life that Klaus thought might somehow help birds see the magnetic field."
• Annie McEwan [26:02]: "Here we go down into the land of the teeny tiny electrons and protons and photons and neutrons..."
• Annie McEwan [33:07]: "But I guess he felt compelled to help me out."
• Annie McEwan [34:07]: "No, it's probably some kind of landmark, like bright or dark spot or blue spot..."
• Annie McEwan [35:35]: "The bird is watching the sunset... watching the Earth's magnetic field, in a sense, come online."

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Key Takeaways

• Quantum Mechanics in Biology: The episode illuminates how principles of quantum physics, particularly entanglement and radical pairs, play a crucial role in biological processes like bird migration.

• Cryptochrome’s Role: The discovery of cryptochrome as the molecule facilitating radical pair formation bridges the gap between quantum theory and observable biological behavior.

• Visual Magnetoreception: The hypothesis that birds can visually perceive the Earth's magnetic field opens new avenues in understanding animal navigation and sensory biology.

• Interdisciplinary Collaboration: The convergence of physics, biology, and field research exemplifies the importance of interdisciplinary efforts in solving complex scientific mysteries.

Quantum Birds not only unravels the sophisticated mechanisms behind avian navigation but also celebrates the seamless integration of quantum science into the natural world, showcasing the marvels that curiosity and collaborative research can reveal.

Transcript

[Latif Nasser]

Radiolab is brought to you by Progressive Insurance. Do you ever find yourself playing the budgeting game? Well, with the name your price tool from Progressive, you can find options that fit your budget and potentially lower your bills. Try [e-mail], progressive Casualty Insurance Company and affiliates. Price and coverage match limited by state law, not available in all states. Radiolab is supported by the John Templeton foundation, funding interdisciplinary research and catalyzing conversations designed to inspire awe and wonder. Dive deeply into the wonders of the universe. @Templeton.org.

[Annie McEwan]

Listener supported WNYC studios.

[Scott Widensall]

Wait, you're listening.

[Annie McEwan]

Okay. All right. Okay. All right. You're listening to Radiolabs from wnyc.

[Latif Nasser]

I'm Latif Nasser, this is Radiolab. And today.

[Annie McEwan]

Hello. Hello.

[Latif Nasser]

We are following the internal compass of our senior producer, Annie McEwan.

[Annie McEwan]

All right, so last October, I traveled to a mountain in Pennsylvania. It's dusk. It's a place called Hawk Mountain Sanctuary.

[Scott Widensall]

Hey, Gabe, how are you?

[Annie McEwan]

And I was there to join a group of volunteer researchers to wait in the cold and the dark, hoping to catch some owls.

[Scott Widensall]

Okay.

[Latif Nasser]

Catch some owls, yes.

[Annie McEwan]

But not just any owls. These were northern saw whet owls. Do you know what a saw whet owl is?

[Latif Nasser]

No.

[Annie McEwan]

What is the deal with these birds?

[Scott Widensall]

So I'm gonna be dryly scientific here and describe northern saw whet owls as cosmically cute birds.

[Annie McEwan]

Okay.

[Scott Widensall]

Because they are.

[Annie McEwan]

So Scott Widensall here, he's a natural. He was actually the guy that invited me up to come see these owls.

[Scott Widensall]

They're the smallest owl in the east.

[Annie McEwan]

They're about the size of a soda can. And do you ever just take one and put it in your pocket?

[Gabe]

We're not allowed.

[Annie McEwan]

They're like kittens. They're kittens, but they're owls. They have these huge eyes, they weigh.

[Scott Widensall]

A little bit more than a robin.

[Annie McEwan]

And to catch them. God, this net is so thin. Hopefully they won't see it. You have to string these wispy black nets up in the woods.

[Scott Widensall]

Just fire it up. Watch your ears.

[Annie McEwan]

You set up spider speakers and you blast this sound.

[Latif Nasser]

What is that?

[Annie McEwan]

Uh, that is a recording of a mating call of a male saw whet owl.

[Latif Nasser]

Sounds like a truck backing up.

[Scott Widensall]

It's this. It's the sexy sound of love. If you're a female saw whel.

[Annie McEwan]

Romantics. Anyway, so you get all that stuff set up, you walk away from the nets, you hunker down and wait, hang out. Like play cards and stuff?

[Scott Widensall]

Yep.

[Latif Nasser]

And why are they trying to catch these owls?

[Annie McEwan]

Uh, well, they're migrating Owls. So if they can tag them, we.

[Scott Widensall]

Can find out how long these birds live, where they travel. Do they come back to the same place every year? Do they have the same mate every year? Do they go to the same place in the winter?

[Annie McEwan]

It's like they get this window into the bird's life, which is great and cool. Um, but actually the reason I was there that night was because I had recently become really obsessed with a very particular part of, of a bird's body.

[Latif Nasser]

What part? What's the part?

[Annie McEwan]

I will tell you in a minute. But anyway, so we got the net set up and then after sitting around for a whole hour. Are you going up? We're going up. Oh my gosh. We went to check the nets and in the first hour, looks like. No owls in the nets. There were no owls.

[Scott Widensall]

Don't be discouraged.

[Annie McEwan]

Not at all.

[Scott Widensall]

We didn't catch anything in the first net check last night. And then we had a very busy night.

[Annie McEwan]

And in the second hour, okay, second time, looking at the nets, there were no owls. Again, no.

[Scott Widensall]

Did WNYC have a reputation for being a jinx?

[Annie McEwan]

Oh, no. Do you think that's what.

[Henrik Moritzen]

No.

[Annie McEwan]

And at some point in the night, we had been joined by this group of kids, this young birders club. And they were so excited to see owls and they were being amazing sports. But you know, it was past their bedtime. It was getting colder and colder, like the wind was picking up and these nets were just so empty.

[Latif Nasser]

Oh, man.

[Annie McEwan]

And I started to have this thought, like, man, we are just sitting in the woods listening to a garbage truck backing up and owls are not coming. It's about 9:00 at night. But then on the third hour, third time, I think there might be one. There's one. Owls. There's an owl.

[Teddy]

Wow.

[Annie McEwan]

There's two of them. In the glow of my headlamp, I could see these two tiny bundles of brownish white feathers caught out of the air like fish in a net. I can see its yellow eye. Wow. Got him. The volunteers detangled them from the nets.

[Thorsten Ritz]

Come on, open up your little talon.

[Annie McEwan]

And brought them down to the kids. She's looking at me. And they watched as they were weighed and measured.

[Scott Widensall]

And we put a little leg band with a nine digit unique serial number on their leg.

[Annie McEwan]

It was really iced. And then Scott did this very surprising thing.

[Scott Widensall]

I'm gonna lift, I'm gonna lift the facial disc away here.

[Annie McEwan]

Like, you know they have these disk faces. Yeah. Scott gently lifted forwards one side of the owl's face.

[Scott Widensall]

And you can Actually see that ear.

[Annie McEwan]

Opening, and it reveals this crazy inner head world of the owl. What is it there? It was, like, this surprisingly deep ear hole. It had this sort of, like, inner cave thing, all these nooks and crannies, and it was all covered with, like, a very thin layer of pinkish skin. But the wildest part was that that.

[Scott Widensall]

Gray thing you see is actually the back of the eyeball.

[Annie McEwan]

You can see the back of the huge, bulging eyeball in its head. Like, you see it. It's a little trap door to the back of the eyeball almost.

[Scott Widensall]

Yeah, pretty much.

[Thorsten Ritz]

Oh, my God.

[Annie McEwan]

I couldn't believe it.

[Latif Nasser]

Why would their face open like a door?

[Annie McEwan]

I don't know, but it was amazing. And it was so weird. And, like, I was so excited that we got to see this owl's eyeball. Like, so much of it. Wow, that was the coolest thing I've ever seen because, like, that's kind of the whole reason I was there to take a good look at the eye of a bird.

[Latif Nasser]

Hmm. Okay. How come?

[Annie McEwan]

Because I had recently learned that it's possible that one of the biggest biological mysteries of all time, this fleshy, feathery animal mystery, could be answered finally by tapping into the most abstract, far out there, hidden realm of the universe. I can see its yellow eye. A place where the laws of space, space, and time are completely upended. And that all of that is somehow happening. Somewhere inside, she's glaring. The eye of a migrating bird.

[Latif Nasser]

Okay, I have no idea what you're talking about.

[Annie McEwan]

Okay.

[Latif Nasser]

But I would like to.

[Annie McEwan]

Great. I was hoping you would. So before we go totally sci fi, I'm just gonna do a quick little orientation of things.

[Latif Nasser]

Okay?

[Annie McEwan]

So, as you know, many birds migrate, right?

[Scott Widensall]

Twice a year, this enormous avian river is passing overhead, you know, just stitching the continents, stitching the hemispheres together as they have been doing for millions of years.

[Annie McEwan]

And the big biological mystery that humans have puzzled over for millennia, and something we've actually talked about in RAD before a couple of times is basically just how do they do it?

[Latif Nasser]

Like, how do they find? Like, how do they figure out where to go?

[Annie McEwan]

Yeah. Like, how does a little migratory bird leave its nest, say, in Alaska, and without compass or map, manage to arrive on the same branch of the same tree in a backyard in New Zealand, year after year after year?

[Latif Nasser]

Yeah, right. And we don't know how it does that.

[Annie McEwan]

Well, we know pieces of the answer. So birds actually use a bunch of different things to orient themselves. Like, they use the stars, the sun, they follow Mountain ranges and rivers. They use their sense of smell, and sort of, incredibly, they can also use their sense of hearing.

[Scott Widensall]

Birds can hear extremely low frequency sound waves that are generated by ocean surf and tectonic activity and wind blowing through high mountain passes. And there's been some speculation that a bird migrating south through the Great Plains of North America would be able to hear the Atlantic Ocean in one ear, the Pacific Ocean in its other ear, and the rumble of volcanoes in the Transvolcanic Belt across the middle of Mexico dead ahead of it.

[Latif Nasser]

Wow.

[Annie McEwan]

So they have all these tricks, but the thing is, if you take all that stuff away, birds can still do it. They can still orient themselves in space. They can still figure out where to go. So there's like something else at work.

[Latif Nasser]

Here, like magnetic fields or something.

[Annie McEwan]

Yes. So since the late 19th century, biologists have thought that birds probably do use the Earth's magnetic field, which, you know, is this absolutely massive force field that surrounds the planet like a huge bubble protecting it from the sun's solar winds.

[Latif Nasser]

Right.

[Annie McEwan]

But the weird thing, and part of the thing that's been stumping scientists all these years is that an organism really.

[Scott Widensall]

Shouldn'T be able to sense it.

[Latif Nasser]

Huh. Why not?

[Annie McEwan]

Because as humongous and important as it is, it is, like, weirdly weak.

[Scott Widensall]

It is really, really, really, really, really weak.

[Latif Nasser]

Really?

[Annie McEwan]

Yeah, it's like 10 to 100 times weaker than a fridge magnet.

[Latif Nasser]

Wow.

[Annie McEwan]

And so, like, the question is just how do they sense this super weak thing? And for a long time, the assumption was that they were using crystals, these.

[Scott Widensall]

Tiny little deposits of magnetic crystals called magnetite in the beak of the bird.

[Annie McEwan]

And that was the story that we talked about in our other Radiolab episodes about this mystery.

[Scott Widensall]

And presumably this acts like a little.

[Annie McEwan]

Magnet, therefore accompanying the.

[Scott Widensall]

Yeah, pulls the beak to the north or something.

[Latif Nasser]

Yeah, that's what I thought happened.

[Annie McEwan]

Yeah. But the problem is, like, magnetite doesn't seem to be connected to the bird's brain in any way.

[Latif Nasser]

Oh.

[Annie McEwan]

So even if those deposits are sensing the Earth's field, there's no message getting to the brain of the bird for the bird to then say, ah, that's north. I should turn this way. Da, da, da, da, da. So it seemed like birds must be using the magnetic field to find their way around, but, like, nobody could figure out how they could sense it. And this is where the mystery of how birds do what they do has just been stuck for many, many years. Okay, but now we get to the new crazy amazing. Maybe we figured it all out. Part Right. Emphasis on crazy.

[Scott Widensall]

Maybe this is where we go seriously off the rails into the deep sci fi sounding stuff. So.

[Annie McEwan]

So the story of the deep sci fi sounding stuff actually starts in the 1970s with a guy named Klaus, a.

[Scott Widensall]

Young German physicist named Klaus Schulten, who was thinking about the problem of magnetoreception in birds.

[Annie McEwan]

At the time, biologists were like, all about these little iron crystals in the bird's beaks. But Schulten was thinking about some very strange physics.

[Scott Widensall]

What's called a radical pair.

[Latif Nasser]

A radical pair.

[Annie McEwan]

What is a radical pair?

[Latif Nasser]

I mean, I think it's a piece of fruit that just has red. Karl Marx radical pair. It's like Animal Farm but for plants.

[Annie McEwan]

No. So this is like an actual pair of things. And the things that are paired are electrons. And that means that we have to take a moment here to dig into how things work down at the teeny tiny scale of itty bitty stuff.

[Latif Nasser]

All right, we're zooming in. Or we're diving into.

[Annie McEwan]

We're diving and zooming.

[Latif Nasser]

Diving and zooming.

[Annie McEwan]

Here we go down into the land of the teeny tiny electrons and protons and photons and neutrons, all that stuff. And maybe you've heard some things about this tiny world and that things get very weird down there.

[Latif Nasser]

Yeah.

[Annie McEwan]

Right. So this is the quantum world.

[Latif Nasser]

Right.

[Annie McEwan]

So the tiny things down in the quantum world, it's like they break all our normal rules of space and time. For example, one thing can be in two different places at the same time. Things can move through solid barriers. Effects can happen before causes.

[Latif Nasser]

It's really weird.

[Annie McEwan]

Yeah. Like, and if this were true, like in the big stuff world, it would kind of be like you catching a ball could actually cause me to throw it to you. What? Or the ball is both in your hands and my hands at the same time. Or it's, you know, both blue and green at the same time.

[Latif Nasser]

Like whenever I hear about this kind of thing, it's always kind of incredible. But it's like also incredible. Like you can't even. It doesn't even seem real. You can't even believe it.

[Annie McEwan]

Totally, Totally. Yeah. And I think it's like we've just never experienced anything like this. But this is what hard hitting physicists, people who have studied this stuff all their lives, you know, they swear this is true. These are just the facts of life down there.

[Latif Nasser]

Yeah.

[Annie McEwan]

And as weird as it sounds, there is one of these little quantum facts of life that Klaus thought might somehow help birds see the magnetic field.

[Scott Widensall]

Yeah. Scholten had the idea that it was tied to an aspect of quantum physics known as quantum entanglement, where. Oh, boy. And now you're gonna expect me to explain something in quantum.

[Annie McEwan]

Okay, so like, simple version. Simple version. Super simple version is that sometimes two particles can become linked in a particular way, such that what affects one will.

[Scott Widensall]

Instantaneously affect the other.

[Annie McEwan]

Like, you can tweak one of them, and the other will react right away, even if those particles are really, really.

[Scott Widensall]

Far apart at opposite ends of the universe.

[Latif Nasser]

Okay.

[Annie McEwan]

Which is, you know, just another way that tiny things break the classical rules of space and time. Because, you know, in our world, the only way for one thing to affect another is by sending some kind of signal through space, which takes time, but it's like these two particles have some kind of backdoor space time loophole. So they're just kind of instalinked.

[Latif Nasser]

Right. That is weird.

[Annie McEwan]

Yeah. And this is what scientists call entanglement.

[Latif Nasser]

Got it.

[Annie McEwan]

And of course, this is totally fodder for sci fi writers. Like imagining worlds with teleportation energize or whatever.

[Scott Widensall]

Exactly. It's beam me up, Scotty stuff, no doubt about it.

[Annie McEwan]

But also, it's a real thing. I mean, it's the basis of quantum computing.

[Latif Nasser]

Right.

[Annie McEwan]

Part of what makes quantum computers so powerful. Anyway, so back to Klaus Schulden. He's sitting back there in the 70s thinking about a particular kind of entangled particles called radical pairs.

[Latif Nasser]

Not the fruit.

[Annie McEwan]

No. Right. So if you picture an atom in your high school textbook, picture it.

[Latif Nasser]

Yeah, yeah, yeah, yeah.

[Annie McEwan]

It has a nucleus with electrons zipping around it.

[Latif Nasser]

Right.

[Annie McEwan]

And a lot of times, those electrons come in pairs. Now, to understand that, there is one thing you need to know about electrons, which is that they have this something called spin. Now, apparently, they're not actually spinning, but this is how physicists talk about it, as if they can spin in one direction or the other. And when you have these electron pairs, their spins are linked. Now, Schulzen knew it was possible for a photon of light to knock one of those two paired electrons off its atom, away from its partner. And if it happens to land on a neighboring atom, even though they are now physically separate, the electrons stay paired. They are still connected. So now those two atoms become a radical pair. They're spiritually one, in a sense, because they have these electrons that are entangled in this spooky, instantaneous quantum way. Okay, so all of this was just total stock and trade quantum mechanics at the time. But Schulten, doing some elaborate experiments with radical pairs in the lab, had Noticed something he didn't expect. When these atoms become radical pairs, they are suddenly super duper duper magnetically sensitive.

[Latif Nasser]

Okay, okay, so now I'm seeing the bird connection here.

[Annie McEwan]

Okay, yes, yes. Okay, okay. So. And Scholson, like, he had buddies in biology land and he was well aware of this whole how does a bird sense the magnetic field mystery. And so he thought, like, hey, maybe if there are radical pairs somewhere inside the bird, maybe these could act like a magnetic compass.

[Scott Widensall]

And so Klaus Scholten came up with this idea and submitted it for publication. You know, wrote it up in a paper, submitted it into publication to an American physics journal and it was rejected. He had a rejection letter saying that a less bold researcher would have consigned this idea to the wastebasket.

[Latif Nasser]

Whoa.

[Annie McEwan]

Yeah.

[Scott Widensall]

I mean, he did eventually publish it in a small German journal, but even.

[Annie McEwan]

Then it was mostly ignored.

[Latif Nasser]

Why did it get rejected and then ignored?

[Annie McEwan]

I think for physicists, like on the physics side, all this quantum stuff is. It's very fragile. Like, as soon as there are a lot of things bumping around and into each other, these quantum effects, like entanglement, they disappear and like just collapse back into normal. And this is why, like Google and Microsoft, whatever spend have spent a buttload of money keeping their quantum computers really, really cold and inside special things, because they need to keep things very, very calm in there. Otherwise molecules are just going to bump around and ruin everything. And the inside of a bird, or really any animal, is a very busy, bumpy place to be. So Klaus Schulten, like, saying that entangled pairs of electrons might help a bird sense the magnetic field. That was kind of insane.

[Thorsten Ritz]

This was very difficult for many physicists to accept for a long time.

[Annie McEwan]

Astrobiologists.

[Thorsten Ritz]

Can you turn the volume on me down?

[Annie McEwan]

Yeah. People think I'm too loud, especially excitable biologists.

[Thorsten Ritz]

You know, when I get excited about something, I may be even louder.

[Annie McEwan]

Like Henrik Moritzen, who works at Oldenburg University in Germany now.

[Thorsten Ritz]

They are good.

[Annie McEwan]

They honestly just could not understand the math.

[Thorsten Ritz]

Like, my God, there is no way with my mathematical knowledge at that time, or now for that matter, can read that paper.

[Annie McEwan]

Wow.

[Thorsten Ritz]

So this is extremely hard quantum mechanics. I just gave up reading the paper, honestly.

[Annie McEwan]

So, okay, so you found this paper and you're like, oh, never mind, I can't understand.

[Thorsten Ritz]

I could not imagine any, any experiments or anything because I didn't understand it well enough.

[Annie McEwan]

Got it. So Scholzen's paper and his idea just sits on the shelf collecting dust. But lucky for us, much like the quantum world here on the radio, we have the ability to warp space and time. And so we're gonna take a little break. It's gonna be one minute, okay? And in that one minute, 22 years will have passed, and we will arrive at a moment where this quantum bird theory will again take flight.

[Latif Nasser]

Okay, so listeners, stay entangled with us. We'll be right back after this.

[Annie McEwan]

All right, here I am. Ready to. Ready to do it. My name is Annie McKeown, and I am a senior producer at this show, which basically just means that I, you know, spend many hours banging my head against, you know, the computer screen, but, you know, lovingly banging. The best part of my job is creating an immersive scene so you can, like, see it in your mind and feel it in your heart, and it doesn't even really matter what it is. It could be what it would be like to talk to a Neanderthal at a bar or a black hole moving through the earth. If it's done right, I can take you by the hand and lead you into this magical world that surprises you. If you enjoy venturing into these new worlds, worlds we create here at Radiolab, the best way to support us is by becoming a lab member. To learn more about the lab and our exclusive membership Perks, go to Radiolab.org join that's Radiolab.org join and thank you.

[Gabe]

Radiolab is supported by Intuit. TurboTax Taxes was dealing with piles of paperwork and frustrating forms and then waiting and wondering and worrying if you are going to get any money back. Now, doing your taxes is easily uploading your forms to a turbo tax expert who's matched to your unique tax situation. An expert who's backed by the latest technology which cross checks millions of data points for accuracy. While they work on your taxes, you get real time updates on their progress and you get the most money back guaranteed. All while you go about your day. No stressing, no worrying, no waiting. Now this is taxes Intuit TurboTax. Get an expert now on TurboTax.com, only. Available with TurboTax Live. Full service real time updates only in iOS mobile app. See guarantee [e-mail] guarantees.

[Lulu Miller]

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[Teddy]

Radiolab is brought to you by BetterHelp. You know, finding the right people to fill your life with is not easy. Whether you are looking for a partner or more friends, it is a lot of work for what can often feel like not a lot of reward. I do think though, that it is easier to find and get to know people you click with and fast when you really know yourself. And therapy is a great way to do just that. I can honestly say a therapist has changed my life for the better, and with BetterHelp, finding one has never been easier. It's fully online, making therapy affordable and convenient, and gives you access to a diverse network of more than 30,000 credentialed therapists with a wide range of specialties. And you can easily switch therapists anytime at no cost. Discover new relationships with yourself and others with BetterHelp. Visit betterhelp.com Radiolab to get 10% off your first month. That's betterhelph e l-p.com Radiolab.

[Latif Nasser]

I'm Latif Nasser, this is Radiolab. We are back from break with producer Annie McEwan and altogether we have just made a quantum leap forward in time. How many years? 20 some odd years? Something like that?

[Annie McEwan]

22 years? Yep. Okay, so Klaus Schulten in that time. Klaus Schulten has moved on to other things. He became a very important biophysicist and for the most part he set magnetoreception in birds aside.

[Thorsten Ritz]

Until year 2000, Schilten had a very smart graduate student called Thorsten Ritz, and.

[Annie McEwan]

He, together with Schulten, they took that old paper from the 70s and wrote.

[Thorsten Ritz]

Exactly the same hypothesis again with illustrations and in a language that biologists could understand.

[Annie McEwan]

And they also added one really important thought, which is that they think this radical pairing thing could happen inside the eye, because of course that's the place where light gets into a bird.

[Thorsten Ritz]

And then it took off like crazy.

[Annie McEwan]

Because now biologists knew where to look and what to look for. And in fact, thanks in part to Morrison's work, we now know that there is a molecule.

[Scott Widensall]

It's a pigment protein that is found in the eye of many birds, especially.

[Annie McEwan]

Migratory birds, that can do this radical pair thing when it's hit by a photon of light. And it's called cryptochrome, the molecule that.

[Thorsten Ritz]

Absorbs light and use this light energy to move an electron.

[Annie McEwan]

And since then, scientists all over the world have done experiment after experiment, finding more and more supporting evidence showing that.

[Scott Widensall]

This idea he had back in the 1970s was correct.

[Annie McEwan]

Okay, so can I play this out for you?

[Latif Nasser]

Yes, please.

[Annie McEwan]

Okay, ready? Here we go.

[Gabe]

Here we go.

[Latif Nasser]

I'm ready. Let's go.

[Thorsten Ritz]

Okay, so here is the idea.

[Annie McEwan]

A bird is flying at night under a blanket of stars, and if we were to zoom into its eyeball, we'd see cryptochrome molecules made up of atoms with a bunch of paired electrons buzzing around them. Yeah, and these pairs, like I said before, their spins are linked. So they're like little spinning dance partners.

[Thorsten Ritz]

One up, one down.

[Annie McEwan]

One spins up, the other spins down always. Okay, so there they are. They're just dancing in their little atom home together, and they're completely uninterested in the very, very weak magnetic field of the earth. Until the bird glances up at the night sky, and then, bam.

[Scott Widensall]

The photon of light that was emitted 10 million years ago from a distant.

[Annie McEwan]

Start hits the bird in the eyeball.

[Scott Widensall]

And it strikes this cryptochrome molecule, and it knocks an electron away from its.

[Annie McEwan]

Dance partner, and it goes kapoo. And it lands on another molecule in.

[Thorsten Ritz]

The eyeball that is a radical pair.

[Annie McEwan]

And remember, even though they're separated, they're.

[Scott Widensall]

Still linked, quantumly entangled.

[Annie McEwan]

So they're still doing their little dance. But now that they've been radicalized, they're.

[Thorsten Ritz]

In this highly unstable state, and they've.

[Annie McEwan]

Become super duper sensitive, 10 million times.

[Thorsten Ritz]

More sensitive to Earth's magnetic field.

[Annie McEwan]

And it's almost like this giant presence that was lying hidden suddenly appears. And now their dance is influenced by.

[Thorsten Ritz]

The magnetic field of the earth.

[Annie McEwan]

So now some of the time, they do their old up, down move, but they also sometimes spin in the same direction, like both up or both down or whatever.

[Latif Nasser]

Okay, so it's more variation, different kind of dance moves.

[Annie McEwan]

Exactly. Yeah. And, like, the key thing here is just, like, how much they spin opposite and how much they spin together. That changes depending on which direction the bird is flying. Okay, so, for example, it could be, like, if the bird is flying north, those electrons are more likely to be split, spinning together, both up, up. Okay, and then let's say the bird neurom veers right and heads due east. Now, those electrons are more likely to be spinning opposite each other. Up, down.

[Latif Nasser]

Hmm.

[Annie McEwan]

Are you with me?

[Latif Nasser]

I'm with you. I think I'm with you.

[Annie McEwan]

Are you?

[Latif Nasser]

Yeah.

[Annie McEwan]

Okay, well, just to bring it home here, this is obviously incredibly simplified, but the important thing is that there are not just one, but millions of these radical pairs in inside the eye of a bird doing their various dances all at the same time as the bird flies along. And it's not like these little bits are acting like magnets, like, pulling the bird one way or the other. Instead, you've got this kind of, like, Rube Goldberg bit of business at the end here, where different spins create different kinds of chemicals. All of that leading to the optic nerve, sending electrical signals to the brain. Woo.

[Thorsten Ritz]

Now, this is very, very complicated.

[Annie McEwan]

Yes.

[Thorsten Ritz]

The uncomplicated part is really the bird.

[Annie McEwan]

Now has a chemical, chemical compass in its brain.

[Thorsten Ritz]

And this chemical compass exists because the electron spin interacts with the Earth's magnetic field.

[Annie McEwan]

In other words, birds are finding their way around the planet across hemispheres, thanks to these teeny tiny particles inside their eyeballs that are getting pushed around by this giant force field surrounding the planet.

[Scott Widensall]

And so you can do something with your eyes that owls can't. Bingo. Exactly. No owl will ever look out of the corner of its eye at you because they can't move their eyes. And that's one of the reasons, I think, why humans have always thought owls are wise, because they never give you any side eye. They only look straight at you.

[Annie McEwan]

On the mountain in Pennsylvania.

[Scott Widensall]

All right, we're gonna let this bird go. I'm gonna pass.

[Annie McEwan]

After we caught the owls and took some measurements and saw their eyeballs. Ready? Ready. So I'm gonna hold it up on my hand. We let them go. There he goes. And now most of the research on this quantum entanglement stuff has been done on songbirds, not owls per se. But the scientists I've talked to say that if all this is right, it's likely something that pretty much all migrating birds, including these owls, do. And so, after learning all this, it was just this whole other thing, standing there and watching her fly off into the night on her way. Especially in light of something that Henrik and his team discovered in 2005.

[Thorsten Ritz]

If you look into the brain of a bird and you ask, which part of the brain do you use to process magnetic compass information?

[Annie McEwan]

The answer is in the visual system.

[Thorsten Ritz]

It's seeing, basically, that is activated.

[Annie McEwan]

The bird is not only sensing The Earth's magnetic field. It's actually seeing it.

[Latif Nasser]

Cool.

[Annie McEwan]

Do we know anything about what it might look like?

[Thorsten Ritz]

Well, I mean, this could be some kind of shading on top of whatever else they are seeing. But in principle, we have no idea because we cannot ask the bird what it's seeing.

[Annie McEwan]

Right. So there's no way of.

[Thorsten Ritz]

No. I mean, birds are tetrachromatic. Right. That means they already have a color channel more than us.

[Annie McEwan]

Oh, okay.

[Thorsten Ritz]

So they will see much more colorful world than we do. But it's hard for us to imagine how a much more colorful world would look like. You can go the other way. Humans have three, but a lot of mammals only have two. I can tell you that's a very, very dull world compared to the one we see. But a dog cann imagine what our colorful work will look because it has never seen it and it will never see it.

[Annie McEwan]

Right.

[Thorsten Ritz]

So now you imagine instead of three channels, birds have four channels.

[Annie McEwan]

Yes.

[Thorsten Ritz]

Then there comes on top that the birds have some oil droplets, which are basically filters, which means that they may actually have 6 color channels. How the hell 6 color channels look to anything? We have no idea because we can't see it. And then you add a magnetic channel on top, which also we have no idea how that would look. So it's guess. We will have to guess.

[Annie McEwan]

And when you lie in bed at night imagining what this looks like, you basically limit yourself to some kind of shading and leave it at that. Or are you allowing your imagination to paint a stronger image?

[Thorsten Ritz]

I have a very scientific brain, so anything I haven't proven, I'm not going to fantasize about. So to me, I don't know how.

[Latif Nasser]

It looks like he's just not giving it to you.

[Annie McEwan]

He's not? No, he's not. Okay. I guess one thought I had was. But then I managed to say enough wrong things in a row.

[Thorsten Ritz]

No, that is impossible because all are magnetic.

[Annie McEwan]

But I guess he felt compelled to help me out.

[Thorsten Ritz]

Okay. What it's most likely to be is some kind of landmark, like bright or dark spot or blue spot or whatever color we can't imagine spot.

[Annie McEwan]

And that whatever color we can't imagine is brighter when the bird is, say.

[Thorsten Ritz]

Facing towards north, and then it's gradually going to be darker away from that center.

[Annie McEwan]

So you could say, like the color spot dims as the bird turns and the spot is at its darkest when the bird is facing 90 degrees to that, like at the east and west marks. And then if the bird keeps turning.

[Thorsten Ritz]

Around, it will start Getting brighter again.

[Annie McEwan]

Yeah. And is at its brightest again when the bird is facing south. So it's probably a gradation of a color that we will never see, but, you know, we just don't know.

[Thorsten Ritz]

But it will not be at a specific distance. It will be more like two suns.

[Teddy]

What?

[Thorsten Ritz]

Yeah, but don't now quote me for it being a sun. It can be anything.

[Annie McEwan]

No, of course. But it's a spot, no matter what it looks like. For me. I don't know. I guess I'm sort of envious of the bird. Like, there's this whole crazy part of our universe that is. It's like a part of everything we are, but also, we never get to experience and, you know, we can't even wrap our little brains around it. And yet these birds, it's like they get this direct visual experience, like a message from that hidden foreign realm.

[Latif Nasser]

Huh? Yeah.

[Annie McEwan]

And one thing that I found just kind of beautiful was that talking to Henrik over the phone recently, he told me that he thinks, and there's a lot of evidence to support this, that, like, actually birds are only able to see the magnetic field at night. And he told me, you know, if you actually watch a migratory bird, after a day of eating or resting, like, a lot of them will fly to the top of trees and you'll see them watching the sunset. And what they're actually doing is calibrating their compasses. And as dusk falls, watching the Earth's magnetic field, in a sense, come online.

[Latif Nasser]

Whoa. That's so beautiful.

[Annie McEwan]

And then when they've got their magnetic compass set, they can take flight.

[Latif Nasser]

Wow. I'm not gonna look at a sunset the same way again. Thank you, Annie.

[Annie McEwan]

Thanks, Latif. And I have a lot of thanks to give for this episode. Thank you, thank you. Thank you a million times to Rosie Tucker and the staff, especially Eric Snyder, Holly Merker, and Seth Benz, at the Hog Island Audubon Camp. This place. And these people are absolutely incredible. They let me come along with them to Monhegan island in Maine to look for migratory birds, and I had a total blast. They have this amazing migration program in both the spring and the fall where you learn how to identify birds. You hike around this tiny, magical island, you eat amazing food. It's just the best. I'm really trying to get my parents to go. Anyway, check them [e-mail] thank you also to the Ned Smith center at Hawk Mountain Sanctuary and all the amazing owl tagging volunteers, Chris Bortz, Cassie Bortz, and Cheryl Faust for putting up with me. Huge thank you to Jeremy Bloom, sound designer extra extraordinaire, who helped me record the owls that night. And to my wonderful brother Jim, who for some reason agreed to spend his birthday helping me drive there and back again in one night. Huge thank you to Isabel Andreessen at the University of Oldenburg for letting us use their beautiful recording studio for free, which was awesome. And finally, thank you to Andrew Farnsworth at the Cornell Lab of Ornithology, as well as Nick Halmaji and Andrew Otto for helping me puzzle through the world of quantum physics in birds.

[Latif Nasser]

This episode was reported and produced by Annie McEwan, who also contributed original music and sound design. This episode was fact checked by Natalie Middleton and edited by Becca Bressler, who was the steady hand that helped guide it where it needed to go. Thanks for listening, all you bird brains and radical pears. Until next time.

[Ira Flatow]

Hi, I'm Teddy and I'm from Los Angeles. And here are the staff credits. Radiolab was created by Jad Abumrad and is edited by Soren Wheeler. Lulu Miller and Latif Nasser are our co hosts. Dylan Keefe is our director of sound design. Our staff includes Simon Adler, Jeremy Bloom, Becca Bressler, W. Harry Fortuna, David Gable, Maria Paz Gutierrez, Sindhu Nyanasambundam, Matt Kielty, Annie McEwen, Alex Neeson, Sara Khari, Sarah Sandback, Anissa Vitsa, Arianne Wack, Pat Walters and Molly Webster. Our fact checkers are Diane Kelly, Emily Krieger and Natalie Middleton.

[Henrik Moritzen]

Hi, this is Beth from San Francisco. Leadership support for Radiolab. Science programming is provided by the Gordon and Betty Moore Foundation Science Sandbox, a Simons foundation initiative, and the John Templeton Foundation. Foundational support for Radiolab was provided by the Alfred P. Sloan Foundation.

[Lulu Miller]

All right, here it goes. Hi, it's Lulu. That is the sound of me returning to the host chair after maternity leave. It is so nice to be back.

[Henrik Moritzen]

Hello.

[Lulu Miller]

And while I was gone, one of my favorite things we released was an episode reported by producer Sara Khari, all about Stockholm Syndrome. You know, a very close and nuanced look at its origins and the surprising ways that it has affected you and me, all of us. That episode is called How Stockholm Stuck. If you missed it, highly recommend you check it out. And we have an addendum to that episode. It's a very real and raw and searching conversation between Sara and one of the most prominent proponents of Stockholm Syndrome, a psychiatrist named Frank Okberg. And you can listen to that conversation over in our VIP party room. The lab. That of course is our members only feed where you can get extra goodies like this, extra conversations, bonus audio. So lab members check that out. If you're not a lab member but you've ever thought about maybe supporting Radiolab, now is a great time. Check out if joining the lab is for you over at www.radiolab.org join you can become a member, listen to that conversation and a bunch of others. Again, that's Radiolab.org join us.

[Beth]

I'm Ira Flato, host of Science Friday. For over 30 years, our team has been reporting high quality news about science, technology and medicine. News you won't get anywhere else. And now that political news is 24 7, our audience is turning to us to know about the really important stuff in their lives. Cancer, climate change, genetic engineering, childhood diseases. Our sponsors know the value of science and health news. For more sponsorship information, visit sponsorship wnyc.

[Annie McEwan]

Org.