Daniel sent us this one, and I think it's the kind of question that quietly ruins your day if you sit with it long enough. We did that episode on homing pigeons — how they navigate using infrasound, frequencies way below what we can hear. And Daniel's question is basically: if pigeons are walking around hearing ocean waves from hundreds of miles away, what exactly are we missing? What percentage of light and sound can humans actually detect? And if the answer is "almost none," what does that mean for how we think about reality?
The numbers are genuinely upsetting. Visible light — everything you have ever seen, every sunset, every face, every color — is about zero point zero zero three five percent of the electromagnetic spectrum. That's not a rounding error. That's a sliver so thin that if the full spectrum were the height of the Empire State Building, visible light would be about the thickness of a sheet of paper somewhere around the lobby.
That's the number that made me put down my coffee.
Sound isn't much better. Human hearing covers roughly twenty hertz to twenty kilohertz, about ten octaves. But mechanical vibrations in nature span from infrasound below zero point zero zero one hertz all the way up to ultrasound above one gigahertz. That's more than thirty octaves. We hear about ten of them. Do the math and we're detecting roughly zero point one four percent of the sound that actually exists around us.
Between sight and sound, the two senses we lean on most heavily to navigate the world, we're working with less than one percent of what's out there. That's not a sensory system. That's a keyhole.
Let's start with light, because the number is shocking and I want to walk through where it comes from. The electromagnetic spectrum spans from gamma rays with wavelengths around ten to the negative twelfth meters, all the way out to radio waves with wavelengths up to ten to the fifth meters. That's roughly seventeen orders of magnitude. Visible light sits between about three hundred eighty and seven hundred fifty nanometers. That's about one point four orders of magnitude. So even on a logarithmic scale, we're seeing maybe eight percent of the range. But in terms of actual frequency bandwidth — the number of distinct frequencies we can detect — it's zero point zero zero three five percent.
Even within that tiny band, we're not getting the full picture. We're sampling.
Human cone cells have peak sensitivities at three specific wavelengths — about four hundred twenty nanometers for blue, five hundred thirty-four for green, five hundred sixty-four for red. We're taking a continuous gradient of light and reducing it to three data points. Your brain then interpolates every color you've ever seen from just those three signals. It's like having a piano with eighty-eight keys but only being able to hear three notes, and your brain just guesses the rest of the chord.
Which is why the mantis shrimp makes me feel like I'm living in a sensory poverty trap.
The mantis shrimp is the flagship example for a reason. Humans have three types of photoreceptor cells. Mantis shrimp have between twelve and sixteen. They see ultraviolet light. They see polarized light — not just the presence of polarization but the angle of it, which we can't perceive at all without specialized filters. They can detect circularly polarized light, which is a thing we didn't even know existed in nature until we found it in mantis shrimp. Their world is so visually rich that we literally cannot imagine it. Not "it's hard to imagine." Our brains lack the hardware to simulate what a mantis shrimp sees. The experience is not just unknown — it's unknowable to us.
There's something almost claustrophobic about that. The idea that there's a color — not a new shade of a color we know, but an entirely new qualia, a new category of visual experience — happening right in front of us, and we'll never know what it looks like.
Here's the thing about the mantis shrimp that really gets me. They're not rare. They're not some deep-sea oddity. They live in shallow tropical waters. They're common. You can see one in an aquarium. You're looking at a creature that is looking back at you and seeing things about you — about the light reflecting off your face — that you will never, ever perceive. And you're both standing in the same room.
That's the horror movie premise hiding inside a nature documentary. So let's move to sound. Give me the pigeon connection, because that's what kicked this whole thing off for Daniel.
Pigeons detect infrasound down to about zero point one hertz. To put that in perspective, the lowest frequency humans can hear is about twenty hertz. Below that, we feel vibration as a physical sensation — like the thump of a bass speaker in your chest — but we don't perceive it as sound. At zero point one hertz, a single wave cycle takes ten seconds. A pigeon can hear a sound wave that takes ten full seconds to complete one oscillation. What does that even sound like? We have no idea.
They're using this to navigate.
They're using it to hear the shape of the landscape. Ocean waves crashing on coastlines generate infrasound that travels for hundreds, possibly thousands of miles. Mountain ranges create standing wave patterns in the atmosphere. Weather systems produce characteristic infrasound signatures. A pigeon flying over France isn't just looking at landmarks — it's hearing the Atlantic Ocean to the west, the Alps to the east, and a storm front moving in from the north. It's navigating through a soundscape that we are completely, utterly deaf to.
When a pigeon flies home, it's not following a map. It's following a symphony we can't hear.
And then you go up the frequency range and things get equally wild. Bats echolocate at frequencies up to two hundred kilohertz. Human hearing tops out around twenty kilohertz, and that degrades with age — most adults can't hear above fifteen or sixteen kilohertz. So bats are operating in a sound world ten times higher than our absolute maximum. They emit calls and listen for echoes that can resolve objects as small as a human hair. A bat flying through a forest at night is essentially seeing with sound at a resolution that would require a microscope for us to match visually.
Dolphins echolocate at frequencies up to one hundred fifty kilohertz. They can detect the internal structure of objects — not just the shape, but what's inside. A dolphin can echolocate a fish and determine whether it has a swim bladder, what size it is, what species it is, and whether it's worth eating, all from the acoustic signature. They're creating three-dimensional acoustic images of their environment in real time. It's not hearing as we understand it. It's a completely different sensory modality that we group under "hearing" because we don't have a better word for it.
We've got pigeons hearing the landscape, bats seeing with sound, dolphins performing acoustic medical imaging on their lunch, and we're over here proud of ourselves for noticing the doorbell rang.
We haven't even talked about the Schumann resonances yet.
The Earth has a set of electromagnetic resonances — standing waves in the cavity between the planet's surface and the ionosphere. The fundamental frequency is seven point eight three hertz. That's well below human hearing, but it's there, constantly, everywhere on Earth. Lightning strikes around the world — about fifty per second globally — pump energy into this cavity, and the planet literally hums at seven point eight three hertz. We evolved in this field. It's been present for the entire history of life on Earth. And we can't perceive it at all without instruments.
There's something almost poetic about that. The planet is singing to itself and we can't hear it.
What's fascinating is that seven point eight three hertz happens to overlap with the alpha range of human brain waves — the frequency associated with relaxed wakefulness. There's been a lot of pseudoscience about this, people claiming the Schumann resonance is the "heartbeat of the Earth" that we're somehow tuned to. The reality is more mundane but still interesting: it's probably coincidence, but it means that when you're in a relaxed alpha state, your brain's electrical activity is oscillating at roughly the same frequency as the planet's electromagnetic cavity. Two rhythms, completely unaware of each other, moving in parallel.
We've established that our perceptual window is tiny. But here's where it gets really interesting — the consequences of that narrow window. Because this isn't just a fun fact about mantis shrimp. It shapes what we study, what we build, what we think is real.
This is where the history of science comes in. Most of the major discoveries in physics came from detecting things we had no sensory apparatus for. Heinrich Hertz demonstrated radio waves in eighteen eighty-seven — he built an apparatus that could generate and detect electromagnetic radiation at frequencies far below visible light. He wasn't extending human vision. He was translating the invisible into something we could measure. When he first saw the spark in his receiver, he was seeing radio waves for the first time in human history — not with his eyes, but through a transducer.
He famously said he didn't think it had any practical use.
He called it "of no use whatsoever." Which is the most Hertz thing possible. Eight years later, in eighteen ninety-five, Wilhelm Röntgen discovered X-rays — electromagnetic radiation at frequencies far above visible light. The first X-ray image was of his wife's hand, showing her bones and her wedding ring. She reportedly said, "I have seen my death." Which is about as visceral a reaction to invisible light as you can get.
Both of those discoveries happened because someone built a tool that could detect what human senses couldn't. And in both cases, the phenomenon had been there the whole time. Radio waves have been passing through your body since the birth of the universe. X-rays have been streaming from the sun and from cosmic sources for billions of years. We just had no way to know.
That pattern keeps repeating. Infrasound from nuclear tests was discovered accidentally in the nineteen fifties when microbarographs — instruments designed to detect atmospheric pressure changes — started picking up signals from nuclear detonations thousands of miles away. Scientists realized they had stumbled onto a global infrasound surveillance network by accident. The signals had always been there. The atmosphere had always been carrying them. We just finally built something that could listen.
This is where the umwelt concept comes in, right? This is the thing that I think really ties all of this together.
Jakob von Uexküll, nineteen oh nine. He was an Estonian-German biologist who proposed that every organism lives in its own sensory world — its umwelt — which is a subset of the total physical environment. The umwelt isn't just what an organism perceives. It's what an organism can perceive. It's the boundary of its reality. A tick's umwelt consists of exactly three signals: butyric acid, which indicates mammal breath, warmth, and touch. That's it. The tick sits on a branch, waits for the smell of butyric acid, drops onto a warm body, finds a spot to bite, and that's its entire existence. It has no concept of light, sound, or anything else. Its reality is three data points.
We look at the tick and think, "poor thing, what a limited existence." But we're doing the same thing. Our umwelt is richer — we've got five senses instead of three signals — but it's still a tiny subset of what's physically out there. The difference between us and the tick is a matter of degree, not kind.
And here's where it gets practical. This isn't just philosophy. There are real-world consequences to our narrow umwelt.
The earthquake thing.
The earthquake thing. In two thousand nine, a major earthquake struck L'Aquila, Italy. It killed over three hundred people. But in the days before the quake, something strange happened. A population of common toads in a breeding pond about seventy-four kilometers from the epicenter abandoned the pond en masse — five days before the earthquake. They left during spawning season, which is behavior that makes zero evolutionary sense unless something was seriously wrong. The leading hypothesis is that they detected P-waves — primary waves that travel through the Earth's crust faster than the destructive S-waves — or possibly infrasound in the range they can sense but we can't.
Five days of warning. We got zero.
It's not just toads. There are documented cases of elephants moving to higher ground before the two thousand four Indian Ocean tsunami. Dogs behaving erratically before earthquakes. Even some fish species changing their swimming patterns. These animals aren't psychic. They're not sensing the supernatural. They're sensing real physical phenomena — infrasound, ground vibrations, changes in the local electromagnetic field — that we simply lack the hardware to detect.
The question becomes: could we build that hardware? Could we build an infrasound sensor network that gives us the warning time that toads get for free?
We're working on it. There are infrasound monitoring stations around the world, originally built for detecting nuclear tests, that are increasingly being used for natural disaster warning. But they're sparse and they weren't designed for this purpose. The toad has a distributed, self-powered, self-maintaining infrasound detection system that's been refined by millions of years of evolution. We're playing catch-up with an amphibian.
That's a humbling sentence. Let's talk about the sensory substitution angle, because this is where it gets optimistic.
So we've established that our senses are narrow-band filters. But the brain isn't just a passive receiver — it's an interpreter. And it turns out the brain is remarkably flexible about what kind of data it can learn to interpret as sensory experience. There's a device called the BrainPort that converts visual information from a camera into patterns of electrical stimulation on the tongue. Blind users wear it and after training, their brain learns to interpret the tongue sensations as visual information. They don't feel like they're feeling something on their tongue. They experience it as seeing. The brain rewires itself to create a new sensory channel.
You're telling me people are seeing with their tongues.
They are literally seeing with their tongues. And there's another system called the vOICe — that's spelled v, capital O, capital I, capital C, lowercase e — which converts visual information into soundscapes. Blind users learn to interpret these complex sound patterns as visual experiences. Again, the subjective experience isn't "I'm hearing something." It's "I'm seeing something." The brain doesn't care where the data comes from. It just wants data.
Which suggests our perceptual limits are not just hardware constraints. They're also software limitations that can be overcome.
This is where the future gets really interesting. If the brain can learn to interpret tongue stimulation as vision, or sound as vision, what else could it learn to interpret? Could we give humans magnetoreception — the ability to sense magnetic fields, like birds use for navigation? Could we give humans electroreception, like sharks use to detect the electrical fields of prey? Could we build a device that translates infrasound into something the human brain can perceive, giving us the pigeon's soundscape?
The first humans with augmented perception might experience a reality as different from ours as a mantis shrimp's is from a human's. They wouldn't just have better senses. They'd have new senses. New categories of experience.
This connects to the biggest philosophical question lurking behind all of this. If ninety-nine point nine nine six five percent of the electromagnetic spectrum is invisible to us, and ninety-nine point eight six percent of the sound spectrum is inaudible to us, what else might we be missing? Not just stuff we haven't detected yet — but stuff we can't detect. Phenomena for which we have no sensory apparatus and no instrument because we don't even know to look.
Dark matter is the obvious example.
Dark matter makes up about twenty-seven percent of the universe's mass-energy density. Everything we can see — every star, every planet, every galaxy, every nebula, every cloud of gas, every photon of light — that's about five percent. Dark matter is five times more abundant than all the stuff we can see, and we can't detect it with any of our senses. We only know it exists because of its gravitational effects on visible matter. It doesn't interact with light at all. It's passing through your body right now and you have no way to know.
We're not just missing most of the light and most of the sound. We're missing most of the mass.
That's just what we know about. The history of science is a history of discovering that our umwelt is smaller than we thought. Every time we build a new instrument, we find new phenomena. Radio waves, X-rays, cosmic microwave background radiation, gravitational waves — all of these were completely invisible to us until we built the right transducer. What's the next one? What's the phenomenon that's as obvious and pervasive as radio waves, but we haven't built the right instrument yet because we don't even know to look?
There's a line I keep coming back to. Every screen is a lie. When you look at your phone, you're not seeing Wi-Fi signals. You're seeing a translation of Wi-Fi signals into pixels. When you get an X-ray at the doctor's office, you're not seeing X-rays. You're seeing a translation of X-ray absorption into a grayscale image. When you use a microwave, you're not seeing microwave radiation. You're seeing your food get hot and trusting that the invisible thing doing the heating is real. Our entire technological civilization is built on translations of the imperceptible into the perceptible.
Medical ultrasound is the perfect example. We use sound at frequencies between two and eighteen megahertz to image internal organs. We literally cannot hear the diagnostic tool that shows us our own hearts beating. The technology exists because we built a transducer that converts ultrasound echoes into visual images. Without that translation layer, ultrasound would be as invisible to us as radio waves were to Hertz's contemporaries.
What do we actually do with this information? Because I think there's a risk of walking away from this conversation feeling nihilistic — like, "nothing is real, we can't trust our senses, what's the point." And I don't think that's the right takeaway.
No, the takeaway is almost the opposite. It's intellectual humility. When you disagree with someone about a subjective experience — whether a room is too cold, whether a piece of music is beautiful, whether a situation feels threatening — consider that you might literally be living in different sensory worlds. Not just different opinions. Different perceptual realities. Your umwelt and their umwelt may not overlap completely.
That's a useful thing to carry around. The person you're arguing with might not be wrong. They might just be picking up a frequency you can't hear.
Second practical takeaway: pay attention to animal behavior. If your dog is acting strangely before a storm — pacing, whining, hiding — it's not being irrational. It's sensing infrasound or barometric pressure changes that you can't detect. That's a real data stream you're ignoring. If you see birds suddenly go quiet or animals behaving oddly, especially before a natural event, take it seriously. They're not being superstitious. They're accessing information you don't have.
The third one, which I think is the one that sticks with me: the next time you use any technology — Wi-Fi, microwave, X-ray, ultrasound, radio, GPS — remember that you're experiencing a translation. Every screen is a beautiful, useful lie that maps the imperceptible onto the perceptible. The world you experience directly is a tiny fraction of the world that actually exists. Everything else you know about reality came to you through a transducer.
That's not a reason to distrust science. It's a reason to be amazed by it. We figured out that we were missing almost everything, and then we built tools to fill in the gaps. That's extraordinary.
Let me leave one question hanging in the air, because I think this is the conversation starter for listeners. If we could design a sixth sense for humans — something completely outside our current perceptual range, something we'd add to the human umwelt deliberately — what should it be? Magnetic field detection like birds, so you always know which way is north? Electric field sensing like sharks, so you can feel the electrical activity of living things around you? Infrasound like pigeons, so you can hear the weather coming from a hundred miles away?
I'd vote for magnetoreception. Imagine never needing a compass. Imagine always knowing where you are relative to the Earth's magnetic field. It would change how we think about space and navigation at a fundamental level.
I think I'd want the pigeon's infrasound. I want to hear the landscape. I want to know what the ocean sounds like from Jerusalem.
That's a very you answer.
It's a very sloth answer. We're deeply connected to the earth. We invented mindfulness.
You did not invent mindfulness.
The historical record is disputed.
There is no historical record.
Now: Hilbert's daily fun fact.
Hilbert: In the nineteen forties, the lighthouse keepers at Cape Race, Newfoundland, maintained a tradition of carving intricate ship models inside empty lightbulbs — a practice passed down from a single keeper who started it in nineteen oh two. Only three of these lightbulb ships are known to survive, all in private collections, and the technique for getting the model inside the bulb without breaking it was never written down.
...right.
What a strange and specific thing to know.
That's the show. This has been My Weird Prompts. If this episode made you feel small in a good way, share it with someone who needs their reality checked. You can find us at my weird prompts dot com. We'll be back next week with another weird prompt.
