Daniel and Kelly’s Extraordinary Universe - What is an impossible color?

Episode Date: August 1, 2024

Daniel and Jorge explore the edges of our colorful experience of the Universe.See omnystudio.com/listener for privacy information.

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or wherever you get your podcasts. Hey, Jorge, as an artist, do you have a favorite color that you use for scientific cartoons Are some colors more science-y than others? Well, it depends on the science. I mean, some science is just more colorful than others. So then what's the color of physics? It kind of depends on the topic, too.

If it's about lasers, I might use red. Or if it's about the sun, I might use a yellow. I've used cyan for particle physics. What makes particle physics cyan? I don't know. That just kind of would seem like fit to the topic at the time. It just gives you the blues. Yeah, or if it's a red hot topic, I might go for a nice, intense red.

But for our books, they usually go with purple. Yeah, what's purple about our curiosity? It's more about the process, you know? It's kind of mentally bruising. I mean, mentally enlightening. I think it's a superposition of both of those. It's both blue and red, which makes purple. There you go.

Hi, I'm Jorge McCartunist and the author of Oliver's Great Big Universe. Hi, I'm Daniel. I'm a particle physicist and a professor at UC Irvine and my daughter tells me I can't see bad. Whoa. Wait, does that mean that you can't get mad or that you don't see the color red? Yes, as a parent of a stubborn toddler, I never once got mad. Absolutely kept my cool every single moment. No, she and I disagree a lot about what they call various colors,

and she's convinced I'm partially colorblind. Whoa, have you ever had it checked? Maybe it's true. What does that mean? You can't tell colors apart or you can seek certain colors, but how do you know you can't see them? You can do these tests where you're supposed to see numbers out of dots, but she just likes showing me lots of different shades

and asking me to come up with names of them, and I'm always like, I don't know, Wild Mountain Raspberry. And she's like, that's not red, it's purple or something. Sounds like she just likes to disagree with you. Yeah. I think I raised her right. Yeah. You raised her to make you red all the time.

But anyways, welcome to our podcast, Daniel and Jorge, Explain the Universe, a production of IHeart Radio. In which we try to pencil in an explanation for how the universe works. We try to color inside the lines and help you understand how this incredible, glittering, beautiful, bizarre, and crazy cosmos actually works. How all of those quantum mechanical little particles come together to emerge into this incredible experience that we all enjoy. That's right.

We try to paint a picture for you of our amazing and beautiful universe using all of the hues of the rainbow to try to communicate to you all the feelings and impressions that the universe has given us as a human race. And in the end, science is trying to build a bridge between our visceral experience, what you actually feel as a conscious entity and our mental picture of what's out there in the universe, the mental model we're all putting together to try to explain how the universe itself absent from our humanity actually works. But in the end, we never probe that deep reality independent of our senses. We're only limited to understanding how it works as filtered by our eyes and ears

and fingertips and everything else. Yeah. And as we look at the universe and filter it through our eyes, sometimes it makes us red with anger about the things we don't understand or blue about the things we may never understand and sometimes maybe even green and envy of maybe possible aliens out there that have figured it out. Did I miss a color? Orange makes it orange for a nice glass of orange juice. Aren't you glad you made that pun? Nice.

All of these things are part of our experience. The color purple in your mind is not actually part of the universe. It's just part of your experience of the universe. Somehow over the centuries and millennia, we have been able to piece to. gather a picture of how the universe out there might actually work, perhaps independent of our senses. Though, of course, we won't know until those aliens come and talk to us about the colors they see in the universe. Do you think they're colorblind, too? Like, Daniel, we think the answer to the universe is a light shade of lavender summer breeze. And then we end up

disagreeing about what that means. Yeah, I think whatever answer they have, my daughter will disagree with him. That's how I raised her. Let's not put her in the greeting committee. I think we agree on that. Oh, my gosh. Yes. Let's not send Daniel's children to meet the aliens. Yeah.

Unless they start an intergalactic war. Maybe the colors are sacred to them. And if Hazel disagrees about what's purple and what's red, she's going to really piss them off. Yeah. Or they might disagree about the color hazel itself. That's right. Yeah, exactly. She is.

Like, why are you caught hazel if you're not the color of a hazel nun? That's it. Forget this human race. It doesn't make any sense. It doesn't make any sense. You know, we named her hazel before we knew her, but she does turn out to like the color hazel and hazel nuts. So there's a win.

Yeah, but how do you know she's actually seeing the color hazel? Maybe she's hazel blind. Hazel blind. Wow. It's all hazy to her. It is. But we are fascinated by this concept of color, not just because it's such a visceral part of our experience,

but because it's deeply connected to, the physics of what's happening out there in the universe. It tells us something about how photons are wiggling or how neutrinos are flying through the universe if you're willing to apply red and blue shifts to them as well. So this concept of color, what we see, what's out there in the universe, it's very confusing but also very illuminating about how the universe actually works. Yeah, there's a lot of physics in light and in all the colors. But then, as you said, it gets filtered through our eyes and our brains. And sometimes what we see is not quite what's out there. And maybe There might be things out there that are maybe impossible for us to experience.

That's right. We know that there are frequencies of light the humans can never experience, but are there also colors that are impossible to see. So today on the podcast, we'll be tackling the question. What is an impossible color? It sounds like a job for Tom Cruise. Don't, dun, dun, dun, dun, dun, done, dun. This color,

We'll self-destruct after you view it. We need a movie in which Tom Cruise is a physicist. Yeah, I mean, he'd have to wear a lot of, like, wigs and prosthetics, of course. He can't look like Tom Cruise. Yeah, he's too sexy to be a physicist. Is that what you're saying? He didn't say that. He violates some physical law.

He's too orange. He's definitely very physical, even if he's not a physicist, right? He does his own stunts. Yeah, that's right. Yeah. I wonder if he would do his own stunts in a physics movie. Like, would he actually sit on the couch all day? I mean, that's probably more dangerous than jumping off a cliff.

Then he put all those professional nap stunters out of work. You can't just take naps on film as an honest. Wait, wait, wait, that's a career? I can be a stunt napper. Exactly. Oh, man, there's a career for everything. I've been doing it all this time for free, Daniel. You know that the sign of an advanced civilization is specialization, right?

And I think once we've achieved stunt napping, we've reached the pinnacle of civilizations. The aliens will be impressed. They might even hire us to nap for them. Well, there's a twist ending. But yeah, this is an interesting question. The idea that there might be colors out there that are impossible to create, to experience, to see, to generate, what side of the color spectrum are we? Yeah, it's a complicated question because colors intimately connected with frequency and we think about it as controlled by light. But really, it's something inside our minds.

It's something generated by our brain. It's an experience. And the colors you experience in the end come from the signals that travel up the optic nerve, which are not physical. They're just interpreted by your brain. And so it's interesting to think about whether there are colors that cannot be described by those signals. Oh, boy. Is this going to get into philosophy, Daniel?

Like what colors can a bat see? That's actually a great idea for a paper. I'm going to write that when we're done with this episode. Yeah. What color is your batwing? Everything in the end is philosophy. if you care about what it means, right? So if you're going to answer the question,

what does that mean anyway? Then yeah, you're getting into philosophy. That sounds like a philosophical statement in itself, Daniel. The philosophy of philosophy. Yeah. You can get a Ph.P.H. PhD. In recursive philosophy. And computer science, philosophical puzzles.

Well, as usual, we were wondering, how many people had thought about this question of what is an impossible color? And so as usual, Daniel went out there to the internet to ask people this question. Thanks very much to everybody who answers these questions for the podcast. If you would like to hear your voice on future episodes, please write to me to Questions at Danielonhorpe.com.

So think about it for a second. What do you think is an impossible color? Here's what people had to say. So color is just a construct of our brain decoding the frequency of elevation. If you think about it and imagine our rods and cones were tuned a little wider and we could actually see an infrared. red and ultraviolet, and colors we can't see would be associated with those frequencies. So I guess every color associated with low frequency radio all the way to gamma rays would

be impossible colors. If color is just how we perceive different wavelengths of light, and light can be in a huge range of wavelengths, it has something to do with the limits of the wavelength approaching either zero or infinity, where suddenly color doesn't make any sense anymore. more? An impossible color. Oh, very interesting. I'm going to say some sort of combination of spectral outputs that are, that is a different spectral resolution than what our, the receptors of our eyes are able to, something to do with color metamerism. Interesting answers. I feel like nobody pitched the idea that maybe it's a color that's made out of

plant-based proteins. Vegan colors. Wow. Yes. No animals or creatures were harmed in the making of this color. I can't even imagine a way you might harm an animal to make a color. You're talking about like, oh, let's see red. We're going to spill something's blood.

Like, it seems pretty unnecessary. I think, Daniel, you just don't have this strong enough imagination. No, but there are colors that are based. on, or traditionally there are dyes that are based on, like, insects, like, you know, insect juice. Oh, yeah. Okay. Interesting. Yeah.

But I don't know how vegans draw that line, you know. We're going to have to have some of them on the podcast to answer the question. Yeah. Sounds like a good question for Katie. All right. Well, let's dig into this question of what an impossible color is, whether it means we can't see it, we can't make it. We can't, it can't exist in the universe. Let's figure it out.

So, Daniel, what are the basics of light and color? Yeah. So let's start outside the human brain before we get into like signal processing and all that stuff and just begin with light, right? Light we know is made of electromagnetic fields. There are ripples in electromagnetic field. So we have electrical fields that can be made by like electrons and magnetic fields and are made by magnets. And light is a coupling of the electric fields and the magnetic fields together. Electric fields can induce magnetic fields. Light is like this perfect little packet where it's sloshing back and forth between the magnetic fields. Electric fields can induce electric fields. Light is like this perfect little packet where it's sloshing back and forth between. electric fields and magnetic fields in amazing harmony. And it can propagate through the universe, this little oscillation of the fields. And these oscillations have frequencies that have a wavelength, they have a frequency that relates to their energy. So if you have a beam of light, for example, coming out of a flashlight, it's actually made out of little photons.

And each photon has a specific energy, which has a specific wavelength and a specific frequency. So that's what light is, right? It's these packets of photons. So I have this laser and I'm shooting it. And there are photons coming out of it. And each photon is like a wiggle in the electromagnetic field. Is that what it is? Yeah.

Each photon is a wiggle in the electromagnetic field. But it's not a wiggle that's like propagating like if I throw a pebble in a pond. It's not spreading out there like that, right? Like in a laser, these things are going in a straight line. These things are going in a straight line. And we just did a really fun but very confusing episode about how long is a photon. And if you didn't listen to that one. I was going to listen to it, but it was a little long.

It was not a light topic. And that tells you that real photons out there in the universe are little packets that have a length that's determined by the spread of the frequencies. So in a sort of idealized sense, you can imagine every photon has exactly one frequency. It's like a pure little packet of one energy, one wavelength, one frequency. But that's actually mathematically very confusing because if it was like that, it would be everywhere in the universe. And so to build up a little packet that actually moves through the universe, a little blob that stays together and fly. through space, you have to have a little bundle of frequencies. So, you know, blue photon is like a little spread of various blue frequencies and a red photon is a little packet of a handful of differently

red frequencies. And they're all going at the same speed, which is the speed of light. Yes, exactly. They all go at the same speed, even though they have a different wavelength and a different frequency. The speed of light is the same across the spectrum. That's at least in our current theory, there are theories of physics like rainbow gravity, where different frequencies travel at different speeds and you get like weird effects around the edges of black holes but on our current theory of physics and according to all of our measurements every photon travels at the same speed and the spectrum of frequencies that light can have it's basically one dimensional right like there's only one knob for the frequency of light yeah if you're going to think about a photon from zero to infinity

but it's just a line and if you were to draw a plot of it yes exactly it's one dimensional it's a great way to think about it and it is infinitely dense right there's an infinite number of frequencies there. We think of these things as like, oh, they're quantum mechanical, so it must be discrete, must be broken up into chunks, right? But the reality is that free objects, even free electrons, are not quantized in their energy levels. They're quantized in the number of photons.

Like, you can't have 1.7 photons or 2.27 photons. You can have one or 2 or 19, but each photon can have any energy. There's no limitation. There's no quantization. There's no discretization of the energy spectrum. but yes, it is one-dimensional. That you know of, though, right? Like, is it possible that maybe frequency is quantized as well?

Yeah, in our current theory, that's the case. There are theories of quantum gravity in which, like, space is pixelated, which would make, like, a minimum wavelength. And in that case, every distance is quantized. In our current theories, there's no minimum frequency. But that doesn't actually really make sense below, like, the plank length where every photon would, like, collapse into a black hole anyway. So it only really applies up to a very, very, very.

high energy but much higher than we could probe today all right so that's the physics of it now let's get into the biology of it so when this these photons hit our eyes they create an experience in our brains yeah i think there's one step before that which is reflection like let's imagine we're looking at a banana right why do we see the banana as yellow we see the banana as yellow because white light hits the banana from the sun and then some of it is absorbed and some of it is reflected you start with almost every frequency of light that you can see hitting the banana, but then the banana has chemicals in it and atoms, and those atoms prefer to absorb some colors and not absorb other colors. And so when you see yellow as banana, that means that the wavelength of light

that is being reflected is a specific band. In this case, like between 570 and 580 nanometers. So you see something as red. It's not because it's like absorbing the red light, right? It's because it's reflecting the red light and absorbing everything else. But then, yeah, hits your eyeball and those photons with a certain frequency are now going to be interacted with by your eye which is like basically a little observational device but wait the banana so the banana absorbs all frequencies except maybe the kinds that are my brain will interpret as yellow yeah not all frequencies but all visible ones right banana can't necessarily absorb all x-rays and gamma rays or infrared but in the visible spectrum and again

and not even all of that right like you see it yellow because it's dominant in the yellow it's never like intense in yellow and zero in every other frequency you know it just peaks unless it's like a perfect banana like is it possible to create a perfect banana that only reflects like one frequency of yellow if you make a shade which only reflects one frequency of yellow I think hazel would call that perfect banana that is a nice name for a yellow yeah exact banana yes scientific banana okay so there's a reflection and also I mean there's filtering too but as well we're talking about it like it right like if i have rose colory glasses the world looks rose to me because it's

filtering out all frequencies except the ones that i see is rose yeah exactly it's filtering there's a reflection all this affects the frequencies that actually hit your eyeball but i hear a lot of confusion out there and the questions i get from listeners about what makes something a color whether it's absorbing it or reflecting it and so it's important to remember that the color is something that's in your eye depends on the light that hits your eyeball you can only see something if it hits your eyeball. For example, if a photon was flying in front of your face, you couldn't see it, right? If it just flies past you, you don't see like a little glowing blob going through the universe. You imagine your visual perception is giving you an accurate description of everything

that's out there in the universe, but you only see things that hit your eyeball. A photon that passes in front of you doesn't send any signals to you so you don't see it. Right. Like if someone to my right shoots a laser to my left, I won't see it. It has to be, they have to be shooting into my eye for me to see the laser. Yeah. Or hit. It has to hit dust particles along the way or air and ionize that and make a glow or a reflection, right? But a perfect laser in a vacuum, you will not see until it slices your head open. Do photons ever split into other photons? Photons can convert into electron positron pairs, which can then interact with other stuff,

like including other photons and do crazy stuff. That different can happen. And those could create other photons. So that can happen, but it's quantum mechanically pretty rare. If you pass a photon through a special kind of nonlinear crystal, it can split into two other photons. They use that for important experiments to like detect single photons. But mostly photons just fly through the universe. That's why we can see them after billions of years and across billions of light years.

They're pretty reliable indicators of what emitted them. All right. So photons can have all these frequencies. Sometimes they get filtered or when they bounce over things, they get, you know, some of them make it out. of the bounds and they sometimes hit our eyes and then that's our experience of seeing things yeah exactly and also our eyeballs do some filtering right to be experienced the photon has to make it into the pupil and then through the lens and then all the way to the back of the retina where it can actually be interacted with that's where there are these proteins which either turn on or turn

off based on the frequency of light so you have these like array of sensors in the back of your eyeballs which can detect photons Did you look into how that works? Like there's a molecule on the surface of the receptor there and then it just gets activated and it wiggles. And then how does that, does it release a chemical or does it create an action potential? How does that work? Yeah, it's actually really amazing. It's like a little machine and it actually changes the protein's configuration.

When it absorbs the photon, it flips like almost a physical switch on this chemical to change its configuration. And that adds energy to it. and then that's picked up by the optic nerve. It's really kind of amazing chemistry. And you have these things. They're scattered all over the back of your eye. Of course, people know there's two different kinds. There's rods,

which basically give you black and white vision. They're sensitive across the spectrum. Wait, wait. What does that mean? Like any photon of any frequency will activate them or not? It's not exactly flat across the spectrum, but essentially, yes, they're not very frequency specific. They're not choosy.

But they're very, very sensitive. Yeah, they're not choosy. But they're very good at picking out photons. They're much better than the cones. So they're good for like, at night, is there a predator there or not? You don't really care if it's red or green. You just want to know if it's something there. Basically, it gives us the sense of like brightness or darkness.

Yes, exactly. It's like black versus white. But then you have these other sensors, these cones. There's three different kinds of them. You have like six or seven million in the back of each eyeball. And most of them are actually concentrated in a tiny little spot in the retina near the center of your vision. So you have like color vision near the sense. center of your eyeball, but mostly black and white in the rest, which is fascinating.

And each of these cones responds to a different frequency of light. So it has like a protein on it and a different protein for each kind. You have three different kinds. And those proteins are tuned to flip or to not flip for different frequencies of light. So one of them mostly flips on for blue light. Another one mostly flips on for green. Another one flips on for like yellowish red light. And it sort of, they sort of ignore the other.

frequencies. They don't exactly ignore them, right? They're not in very narrow bands. So one of them does peak in the blue and one peaks in the green and one peaks in the red. If you imagine like, what's the probability for this protein to flip based on the frequency of light? Well, the blue one will almost always flip for a blue one, but it'll sometimes flip for a green one. They're not as reliably. And the red one will always flip for a red one and sometimes for a green one and occasionally even for a blue one. So they're a little bit overlapping. They're not like perfect bands. Right. They're fuzzy. They can each will react to a certain range of frequencies where those frequencies are centered. It kind of depends on the type of cone. Yeah, exactly. And so you have

three of these, each of which are centered at different places in the spectrum. And then what your brain does is interpret the signals from these cones to figure out, oh, how blue was it? So for example, if you get a signal only from blue cones and nothing from the red and the green one, then you're like, okay, that must have been pretty blue in order to signal the blue ones and not signal the the other ones. But if you get something that signals the blue one and the green one and not the red one, then you're like, okay, it was blue-green. And so you can sort of triangulate where it is on the spectrum by the ratios of how these things react. Interesting. All right, well, let's get to this idea that maybe there are colors that are impossible for us to see even with our

rods and cones. So let's dig into that. But first, let's take a quick break. December 29th, 1975, LaGuardia Airport. The holiday rush, parents hauling luggage, kids gripping their new Christmas toys. Then, at 6.33 p.m., everything changed. There's been a bombing at the TWA terminal. Apparently, the explosion actually impelled metal, glass. The injured were being loaded into ambulances. is just a chaotic, chaotic scene.

In its wake, a new kind of enemy emerged, and it was here to stay. Terrorism. Law and Order Criminal Justice System is back. In season two, we're turning our focus to a threat that hides in plain sight. That's harder to predict and even harder to stop. Listen to the new season of Law and Order Criminal Justice System on the IHeart Radio app, Apple Podcasts, or wherever you get your podcast. My boyfriend's professor is way too friendly, and now I'm seriously suspicious.

Oh, wait a minute, Sam. Maybe her boyfriend's just looking for extra credit. Well, Dakota, it's back to school week on the OK Storytime podcast, so we'll find out soon. This person writes, my boyfriend has been hanging out with his young professor a lot. He doesn't think it's a problem, but I don't trust her. Now, he's insisting we get to know each other, but I just want her gone. Now, hold up. Isn't that against school policy?

That sounds totally inappropriate. to this person, this is her boyfriend's former professor and they're the same age. And it's even more likely that they're cheating. He insists there's nothing between them. I mean, do you believe him? Well, he's certainly trying to get this person to believe him because he now wants them both to meet.

So, do we find out if this person's boyfriend really cheated with his professor or not? To hear the explosive finale, listen to the OK Storytime podcast on the IHeart Radio app, Apple Podcasts, or wherever you get your podcast. Have you ever wished for a change but weren't sure how to make it? Maybe you felt stuck in a job, a place, or even a relationship.

I'm Emily Tish Sussman, and on she pivots, I dive into the inspiring pivots of women who have taken big leaps in their lives and careers. I'm Gretchen Whitmer, Jody Sweeten. Monica Patton. Elaine Welter-off. I'm Jessica Voss. And that's when I was like, I got to go.

I don't know how, but that kicked off the pivot of how to make the transition. Learn how to get comfortable pivoting because your life is going to be full of them. Every episode gets real about the why behind these changes and gives you the inspiration and maybe the push to make your next pivot. Listen to these women and more on She Pivots.

Now on the IHeart Radio app, Apple Podcasts, or wherever you get your podcasts. The U.S. Open is here. And on my podcast, Good Game with Sarah Spain, I'm breaking down the players from rising stars to legends chasing history. The predictions will we see a first time winner and the pressure. Billy Jean King says pressure is a privilege, you know. Plus, the stories and events off the court. And of course, the honey deuses, the signature. cocktail of the U.S. Open. The U.S. Open has gotten to be a very fancy, wonderfully experiential

sporting event. I mean, listen, the whole aim is to be accessible and inclusive for all tennis fans, whether you play tennis or not. Tennis is full of compelling stories of late. Have you heard about Icon Venus Williams' recent wild card bids or the young Canadian, Victoria Mboko, making a name for herself? How about Naomi Osaka getting back to form? To hear this and more, Listen to Good Game with Sarah Spain, an IHeart women's sports production in partnership with deep blue sports and entertainment on the IHeart radio app, Apple Podcasts, or wherever you get your podcasts. Presented by Capital One, founding partner of IHeart Women's Sports. All right, we're talking about color today. Hopefully not getting too off color. Depends on if you think philosophy is off color or not.

What is the color of philosophy, Jorge? Whoa, well, that's getting a little purple there. I didn't mean to ask a lavender question. Well, you don't have to yellow it, Daniel. All right, well, we're talking about how we experience light. And so we know that light are photons. They come in different frequencies. There are frequencies from here to infinity.

But our eyes have these sensors that can detect photons around certain frequencies. And those are the ones that generally we would associate as red, green, and blue, right? RGB. RGB. And it's fascinating that here we've transformed, as you said, an infinite one-dimensional spectrum, photons could be anywhere along the spectrum, to now sort of this 3D spectrum, RGB, right? And the color that we perceive depends in principle on the photon, but really it depends on the

signals from these neurons, which is in this 3D space of red, green, or blue. You've got these signals from these neurons, and once you experience it's in your mind. It's just an interpretation of this point in this three-dimensional RGB space. I guess maybe a question you could ask is like, why are we doing it this way? Why are we seeing the world this way? Why don't we just, why didn't evolution come up with this answer that can just tell you what the frequency of light is? That's fascinating question. And there are some clues based on the variety of the way the color perception works in the animal kingdom.

Like we know that we have these three sensors, but there's nothing special about three. Like people think of RGB as the fundamental basis of color, but it's just sort of the way the human eye works. There are critters out there with like 11 different sensors. The mantis shrimp, I think, has like 14. And there are species out there that can see a broader range or a narrower, narrower range of colors. It just depends on what's more efficient.

The fascinating thing is that the more sensors you have, the better you are typically of being able to tell the difference between shades. So if you really need to know the difference between dark green and light green, you might evolve more sensors or more sort of like processing power to be able to distinguish these signals. Yeah, I guess the more sensors you have, like kind of like post you put in the frequency spectrum, the more you can tell things apart. Sometimes like the mantis shrimp is famous for having like 14 different sensors.

You might think, wow, they must see the world in really vivid color. but they have very, very few neurons to back it up behind that. So it's like they have really, really good hardware, but terrible software. So they might actually not experience more colors than we do, like the actual experience of a mentorship. Who can never know, right, until we write that paper? But I think it takes both complex hardware and complex software to experience a broad variety of colors.

I'm sure those 14 sensors are doing something, right? Like it's letting it discriminate a certain specific colors or certain specific patterns. But maybe after that, it's just not like the mantisrap is not appreciating the color. It depends a lot on the processing, right? You get these signals. If you have very crude responses to them, very crude like neural networks behind them to help you know how to respond to them, very wide bins in your response, for example, you could be wasting a lot of that information. You know, imagine you have like a super excellent microphone and then a terrible cable. You store it in very low fidelity file format.

Could be very lossy. This is all very, very speculative, of course. And there's experiments going on to try to understand what mantis shrimp experience. But there are some humans that have more than three cones. They're called tetra cronets. Yeah. Like mutants? Yes, mutants, exactly.

But there are people that have four different kinds of cones. When I first heard of that, I thought, whoa, they must have a fourth color. How does that happen? Like, they have a mutation that produces a whole different fourth kind of. Cone? Yeah. They're very rare. You can spot them not because they see a different color, we think.

It's not like there's a fourth color that adds to RGB that they can experience that we can't. It's just that they tend to be better discriminating between colors. So like they might pass a colorblindness test that the rest of us would fail. If you put like a really, really subtle difference between the greens and the blues, for example, they might pick something out that other people can't. If you put like a Stanford athlete next to a Harvard athlete. and you'd ask them like which one is which

you'd be like wait wait what they're the same they just look red but you know maybe a more discerning person might say oh no that's a crimson red and the other one's like a wine red junior college red yeah exactly yeah way to come up with an example that's really relatable

I'm sure a lot of people have really struggled with their oh sorry sorry I mean if you put a banana slug next to an anteater next to an ant eater is it the same yellow or not You know, that's actually a really fun question because all the University of California campuses are blue and gold, but they all have different shades of gold. Now, which one is more relatable? To exclude people who don't live in California or to exclude people who've never heard of Stanford and Harvard? I don't know. Let's hear from the listeners.

They're going to be like, you excluded everyone. Anyway, it's fascinating because the biological transformation, of these photons into optic signals puts us sort of like a distance from the actual photon. Like what you're experiencing in your mind is reaction to the optic nerve signals, not the photon directly. Well, it lands in your cone and then the cone generates a signal that then gets transmitted to your brain. Yeah, exactly. Is that what you mean? But you could simulate that signal without the photon, right?

You create that same signal, the optic nerve somehow without the photon, sort of a matrix style. you can experience that color without a photon of that energy actually arriving on your optic nerve and it tells you that like we say photons have color we call them red photons or blue photons but that's not really accurate the photons themselves don't have a color

the color is in your mind photons have an energy to have a frequency to have a wavelength the color is just like your experience of the photon well I mean it's our brains trying to figure out what that frequency is it's just that we came up with a name for things like oh that 30 point

7 Hertz frequency of light, we will call that yellow. Why not? Because we don't have decimal numbers back in the day. It's our brain trying to give us what it thinks is a useful experience or what evolution has proven to be a useful experience. The way that like touching something hot gives you a painful experience, turns out to be useful. Having these different experiences in your mind for these different bands of frequencies turns out to be useful. What's fascinating is a sort of philosophical question of like, what of these experiences themselves come from and are they the same? You know, you put two people in black and white rooms and raise them without color

and describe colors to them. Could they come out of that room and identify red versus blue versus green? Or is it purely captured in the innate experience and can never be described in any other terms? There are fascinating philosophical questions. That's I think has been proven. Our brains have evolved to react to certain colors in certain ways, right? Like green usually has a.

calming effect. Red has a certain sort of anxiety raising effect, right? Is that kind of what you mean? Like our brains are cute to react to certain colors or what? I'm not familiar with those studies, though I imagine it's probably is true that there are emotional responses to various colors. But I mean like the actual experience of the color. Like the red that you feel in your mind is just an experience in your mind the way pain is, right? Pain is like a reaction to heat, to damage to temperature. Red is a reaction to certain frequencies of light hitting you. But the light itself is not red, the way that, like, the heat from the burner is not actually literally painful. The pain is part of your experience of it. Yeah, yeah, I guess. But I feel like maybe

we're sort of maybe confusing things by trying to get to philosophical. It's basically just your brain trying to detect what's happening in the world, right? Yeah, it's your brain's interpretation of these signals. And you're right, getting philosophical does always confuse things because you end up with questions. You can't answer and you don't know if they actually teach you anything. So then let's get back to this topic of maybe that there's a color that's impossible for us to see or to make or both. Yeah, a few decades ago, a theory developed about how we experience color. It's actually slightly more complicated and actually slightly simpler than what we just

described. Instead of imagining that you get like three signals, red, green, and blue, actually the way that... But I guess maybe just from a very basic level, of course, there are colors we can see. Like, we can see light up on the infrared. and we can't see light down or up in the ultraviolet, right? Like there's a whole range of light frequencies, infinite range of light frequencies that our eyes just don't detect.

Like they just go through our eyes or they hit our eyes and don't activate it, right? Yeah, absolutely. There are lots of frequencies of light that don't generate any signal. I don't know if those frequencies of light have a color, though, right? Color is just our experience. And so you just don't assign a color to those frequencies. So there are frequencies we cannot see. I don't know if those frequencies have color.

What would you call a color? Is it like a, if we have like a visual spectrum, right? Like there's a range of frequencies that our eyes can detect. And so let's call color the light that is within that range. The frequency of the light within that range. Yeah, I would say color is our response to frequencies of light within that range. Okay. I mean, that sounds like a arbitrary definition. I could also just posit colors the frequency of the light that way we can see.

So that all works really well if you think about individual frequencies, of light. It all makes sense. But you know, we never see individual frequencies. You always see a mixture. You see a little bit of this frequency, a little bit of that frequency. And once we start thinking about mixtures of frequencies, things get more complicated. And actually a different theory of how we experience color emerged a few decades ago. It's called opposing neuron theory. It says instead of having like a three-dimensional space, RGB, red, green, and blue, one for each of these different kinds of cones, actually we only really have two. because we have opposing neurons that we have neurons that fire more when light is red and less when it's green.

And then we have another one, a blue versus yellow one that fires more when things are yellow and less when things are blue. So instead of having like three-dimensional information, our nerves have figured out a way to incorporate this in just two dimensions, like a green versus red axis and a blue versus yellow axis. It's still pulled out of the same cones, but there's a little bit of processing there to like convert it into this red axis. versus green and blue versus yellow. I think you're talking about what happens after it hits your optic nerve and maybe after it goes up into your visual cortex, right? You're talking about like, you know, maybe your brain or evolution said,

you know, maybe we don't need three signals to figure out what color of thing the banana is or whether that's a spotted leopard or not. Like maybe we can just, instead of having three variables, maybe we can just do with two variables and maybe that's more efficient and faster and just enough to survive. Yeah, exactly. I'm not exactly sure where this happens and, you know, where the brain technically ends and the optic nerve begins. But, yeah, this is part of the processing that happens in your brain.

This is opposing neuron theory. And that means something really interesting because it means there's a little bit of a loss of information. And it means that there are some colors which now cannot be described in this two-dimensional plane. For example, a mixture of green and red. You have this one opposing neuron, which is supposed to fire more if it's red and less if it's green. what does it do if you send it red and green, right? Does it fire more for the red and fire less for the green? It's an oar system.

It can tell you whether this light is red or it's green. There's no response that that neuron can make that says, I see red and green. Wouldn't it fire like somewhere in between? Like neurons encode things by the frequency at which they, you know, send signals, right? Like little like Morse codes. So if it's like doing do-da-da-da-d-d-d-d for red and for green, wouldn't like a mixture give you something in between?

You can see a color that's between red and green, but you can't see like intense red and green simultaneously. Oh, you're talking about the intensity of things, not like which frequencies are present. It's also true of this is fairly dim, but what you can see is a color between red and green, right? If you see like something on the spectrum

that's between red and green, it's like a yellow, then you can see that and the response of the neuron will be between its response for red and for green. If you shine pure green and pure red on it, It's supposed to both trigger it and inhibit it, and it doesn't know how to communicate that. There's no place on its response that means green and red. Now, you said this is a theory?

Is it like, are there experiments back it up? Or like, do we know where in the brain this is happening? We don't know where in the brain this is happening, and there's a controversial set of experiments. People were like, is it possible to see these things? What happens if you put like strips of color near each other and ask people to like focus on the line between them. So they have these experiments that did originally in the 80s where they put like strips of blue and strips of yellow next to each other or strips of red and strips of green next to each other and ask like what do you experience right at the edge, you know, where you're seeing like

red and green at the same time. So there's this paper in 80s by these two guys, Crane and the Piantanita and they claim to see these impossible colors. They asked people to describe what color they were seeing at the boundary and it was like indescribable. And so, So this paper was really controversial for a long time. And then there were experiments two decades later at Dartmouth in the mid 2000s that sort of disputed these results and said like, maybe people are just seeing sort of like an intermediate color. They're not simultaneously experiencing what happens when you have red and green photons.

It's just sort of like hard to describe. So this controversy in the literature about whether this theory is right. There are other theories of how we experience color and whether it's possible to see these colors in some way. So what do you mean by impossible colors? You're talking about like combinations of color that we can experience. Yeah, exactly. That maybe our optic nerves are picking up because they're definitely picking up

something, but we just, because of the way that our brains have maybe streamlined and gotten rid of certain information that doesn't think it needs, now we have kind of blind spots in the color spectrum. Yeah, exactly. And I read a really fascinating paper that suggested you might be able to experience this if you can come up with a way to like differently trigger different parts of your optic nerve. Like if you could get some of these opposing neurons to respond to the green light and some of them to respond to the red light, then instead of all sending the same signal, you'd have some sending the green signal and some sending the red signal both intensely.

And then maybe your brain would know how to interpret that and we'd give you this experience of this red green combination. That's one theory. And people argue like maybe that's what was happening in the 83. experiments that they somehow like parts of it were triggering this part of your nerve and other parts are experiencing other parts of the nerve but yeah it's about these mixtures of colors that we can't see we can see all the pure colors but these mixtures of colors we can't see well I guess you would see them you just wouldn't be able to maybe tell them apart from some of the primary colors

perhaps this is novel color which is a mixture of these two which we do not have an experience of because we think that the sensory mechanisms and the optical nerve processing can't carry the information to describe it. The loss of information means there's no way to encode it, basically, in those signals. Now, do these impossible colors have a specific frequency, or would you call it a different color because it's a mix of different frequencies? Yeah, see, that's fascinating because we think about color as associated with the frequency spectrum, right?

And so pure frequencies, we think of as pure colors, and that makes sense. But here we're talking about combinations of different frequencies, like shooting red and green photons or blue and yellow photons at you at the same time. And so that's why I think it's helpful that separate the question of frequency and color because color is what you experience in your mind and it's not always connected to just one frequency like this, red green color, whatever it is, that would be an experience in your mind, your brain's interpretation of seeing both red frequency photons and green frequency photons at the same time.

You wouldn't experience red, you wouldn't experience green, you'd experience some of red green thing we don't have a word for I guess it kind of goes back to the question of like what is yellow like if we have sensors that detect red blue and green what is yellow yeah if you just think about the spectrum right yellow is the color that triggers the green and the red about the same amount and doesn't trigger the blue like there's a specific frequency that will do that right I imagine and then you could call that frequency yellow but you can also kind of fool the eye into thinking of yellow by mixing frequencies. That's kind of what your TV and your phone screen do.

Yeah, there's a specific frequency range that we know triggers the experience of yellow in your minds, 570 to 580 nanometers, absolutely. And, you know, in the same way that there's like a cyan and there's a purple, you don't have a special cone for these things. There are our brain creating an experience for this whole range of possible signals that it's getting. Right, and you can sort of fool it into thinking of yellow

by mixing frequencies, right? I mean, like in your TV or your phone screen, there's only like three kinds of LEDs in it, right? There's red, green, and yellow ones. And so when you look at something yellow on your phone, it's not actually shooting yellow light. It's shooting some combination of red, blue, and green. That's making your brain think it's yellow. But there's also a frequency that would trigger that same, oh, that's yellow. Anyways, a point is that there are combinations of frequencies that maybe our brains are not designed to, like, trigger your consciousness of the,

them. Yeah, exactly. There should be a unique experience for those combinations, but the brain has no way to interpret it because it doesn't get a unique signal for those combinations. So we haven't like developed a unique experience. It's like you're blind to those colors, kind of. Yeah. Like it just looks red to you. You're like Stanford, Harvard, Irvine, I don't know. It could be any athlete. There's two other sort of ways to think about impossible colors as well, they're colors that can't be generated by any physical source. And then there's these things they called chimerical colors. Ooh, interesting.

All right, let's get into those impossible to make colors and dig into what that means. But first, let's take another quick break. December 29th, 1975, LaGuardia Airport. The Holiday Rush. Parents hauling luggage, kids gripping their new Christmas toys. Then, at 6.33 p.m., everything changed. There's been a bombing at the TWA terminal. Apparently, the explosion actually impelled metal glass.

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My boyfriend's professor is way too friendly, and now I'm seriously suspicious. Well, wait a minute, Sam, maybe her boyfriend's just looking for extra credit. Well, Dakota, it's back to school week on the OK Storytime podcast, so we'll find out soon. This person writes, my boyfriend has been hanging out with his young professor a lot. He doesn't think it's a problem, but I don't trust her. Now, he's insisting we get to know each other, but I just want her gone. Now, hold up. Isn't that against school policy?

That sounds totally inappropriate. Well, according to this person, this is her boyfriend's former professor, and they're the same age. And it's even more likely that they're cheating. He insists there's nothing between them. I mean, do you believe him? Well, he's certainly trying to get this person to believe him because he now wants them both to meet. So, do we find out if this person's boyfriend really cheated with his professor or not?

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Presented by Capital One, founding partner of IHeart Women's Sports. Are we getting very colorful today, looking at all of the rainbow of ideas around the concept of color and how we perceive it and what is a color anyway and what colors your banana as well? Hey, that's a personal question, man. Whoa, well, you just got really purple there. I wasn't even thinking about that. I see what's on your mind, Daniel. Lunch.

Oh, that's even racier. Let's steer back to physics. But we talked about how maybe there are combinations of frequencies of light that we can't see because really color is our experience of how light hits our eye and sometimes that's a specific frequency. Maybe that's sometimes that's a combination. or the absence of certain frequencies. So color is a complicated thing,

but there are maybe combinations of frequencies that we, our brains are just not equipped to detect. Unless maybe you're maybe trained to see them or maybe you're one of these people born with extra sensors, right? Yeah, it could be. And in the end, we don't know what other people experience. We can just ask them to compare previous experience to current experience or to some references,

but we can't cross correlate across brains. We don't know how to extract from inside the brain. brain the actual encoding of these things and interpret it in any sort of objective way map from one brain to another. In the end, it's frustrating. But we can't try to reverse engineer the system and think about ways to experience like weird colors or things that we can't experience. That's a lot of fun. And the system, the way it works, because it has these overlapping responses, also creates these things called imaginary colors, colors, not that we can't experience, but that no physical source could generate. Whoa. Yeah. I think that's a question that I had from the beginning. Are there

colors that are impossible to make? But I guess to be clear, all colors are possible in the universe, right? Like you can always stretch light to be a certain color, infinitely, with infinite precision in the universe, right? Yes, all frequencies of light can exist out there in the universe. But remember, color is our experience in the mind. And it's this interpretation of these red, green and blue cones and then perhaps through these opposing neurons, but because as things overlap, there's a question of like, what would happen if you only triggered the green neuron, right? Now, the green neuron and the red neuron are almost overlapping. They're almost identical. Like, there's a very small shift between them. So any physical photon that hits your eyeball that

triggers the green is very likely going to trigger also some red ones. So you shoot like pure green light at somebody's eyeball. Some of those red cones are all. also going to get triggered. Right. Because I think what we said before is that our cones are not perfect, right? Like they don't just respond to one frequency. They respond to a range of frequencies. And in our eyes, those ranges kind of overlap.

So there are some frequencies that will activate both. Yes. And the red and the green in particular are very close to each other. They respond almost the same way to different frequencies. And so like if you shoot something right in the middle of the green, then the green cone is always going to respond. And the red cone is going to respond like 90% of the time. The blue is like,

further shifted down. But it makes you wonder, like, what would happen if you could somehow just tweak the cones? Don't worry about the light you're shooting at it. Just somehow get the only the green cone to respond without the red cone responding. Like what would happen in your brain? Yes. They call this hypergreen, like the greeniest green that you could experience without any pollution

from the red. In reality, it's essentially impossible to generate this using photons because all these photons will also stimulate that red cone. Oh, you're talking about like it's an impossible experience of that color. We don't know that it's impossible. Like technically, if I attach little electrodes to all the nerves behind the green cones and stimulated them, then you would have this experience. But I can't create a photon that would do the same thing.

You mean like you can't create a photon that will ignore the red cones and only hit the green cone. Exactly. Unless you can somehow aim them really well. Yeah, exactly. super precise lasers in the back of your eye to only hit those green cones so it's possible then well we think it's possible for it to happen it's just that there isn't a physical source we could make that can do that yet but that's the experience of hyper green right right and it's probably

the color of like mountain dew or like if you took a green highlighter and like painted the back of your eyeball yeah so those are imaginary colors then there's another really fun kind of color You actually can experience. But, I mean, it's not just green, right? It's like all of them, right? Like, it's probably possible to create a hyper blue or a hyper red. It's trickier with green and red because those two response curves are basically on top of each other. So it's harder to separate.

Blue is further away. So it's possible to experience a pure blue than it is red or green. But in principle, yes, these same things are true. Even blue photons will stimulate a fraction of the green and red cones. all right so that's one kind of impossible color you said there's another kind there's another category these are called chimerical colors these are colors you experience if you change the way that your cones respond remember these are a little biological machines and they can sort of get tired you know that if you look at a really bright light and then look away for example you still see it right that's because your cones are tired and they're responding differently now there's something like residual effect there so for example if you stare like really bright yellow light, it sort of tires out these opposing neurons. Then if you close your eye or you look at something really, really black, then you see this blue response.

There's no blue there. You're seeing a reaction to tiring out your blue yellow neurons. And so what you see is this super dark blue, this blue that you otherwise could not experience because to experience it, you'd need to receive a bunch of blue photons and that would make it brighter. So you see this like impossibly dark. blue. Wow.

Couldn't you just sit in a dark room and shoot blue photons at my eyeball? You could do that, but then receiving those photons would create an experience of a brighter blue. And if you dial it down, eventually you just wouldn't see anything, you'd just see black. So this is like a blue you can experience without receiving any photons. Right, because you're basically doing the same thing as these imaginary colors, right? You're sort of like knocking out your perception of certain rods and cones, right? Mm-hmm.

Exactly. pretty easy to do you just go to like Wikipedia and Google chimerical colors they have these templates and you like stare at a yellow dot and then look at a black field and you can see this blue which is different from just like a really really dark blue it's fascinating it's called Stigian blue well it's wild to think that like if I'm just staring at something yellow like my brain and my eyeballs and brains are constantly going yellow yellow yellow yellow yellow yeah yeah yeah yeah and eventually they're just like I give up forget it

Yeah, then they're tired, and then the blue wins out, right? And then they're sort of like leaning over. They're biased against it. They're like exhausted at the yellow. They're like, don't show me any more yellow. We're leaning blue for a while. And they're basically sending you blue information, even though there's nothing there. And so because there's no brightness to it, but you're getting blue, your brain is like, well, I've got to give you something blue, but there's no brightness there.

So what do we do? Let's make the darkest blue we can. So it's a very deep blue. Does that mean that if I stare at a banana long enough, it'll eventually look blue? I think it means if you stare a banana long enough and close your eyes, you'll see an impossibly blue banana. I guess you won't see it because you won't be like experiencing photons from the banana. It'll be like sort of this lingering memory in your visual cortex of a blue banana. Yeah, you'll be experiencing a deep blue banana even though you're not getting blue photons from the banana.

From the banana, yeah, yeah. I guess it's all because we have this kind of flawed biological machinery that's trying to, interpret with the frequencies that we see in the world but maybe through evolution it's done it in a weird way where you have these weird effects right where we can see certain combinations or you know we see residual colors yeah all of these colors in the end are our brain's interpretation of these signals signals that are typically generated by this experience or that experience back throwing like the corners of this and the limitations of it we can try to get some understanding of what it means to see color what it tells us about what's happening out there in the universe oh Because I guess, you know, as physicists or a scientist, we can think about all the different frequencies of light, but maybe if you're like a simple creature, you don't need to know all that information. Like you don't need to know whether something's 10.7 hertz. You just need to know like, is this thing going to eat me or not that's in front of me? Is it red, is it the red kind that's going to eat me or is it the blue kind that's going to not eat me? Yeah, exactly.

And that's why some bees can see into the ultraviolet because they have to spot the right kind of flower, for example. That's probably why mantis shrimp have super impressive hard. for ultra-fast processing of this color and then, like, mostly waste that information because they don't really need to know specifically they just needed fast processing. Now, if a mantis shrimp looked at a banana, would it think it's a banana?

That's another philosophy paper I want to write. Or would I think, oh, that's a nice diggy and blue banana. What does it like to be a mantis shrimp eating a banana? Nobody knows. That's the right feel. I'm pretty sure nobody has polished that paper. I'm going to get on it. All right, well, an interesting discussion here about what color is and what we can perceive and, you know, it has a physical basis, but our brains, the way it's evolved, don't experience maybe the world, the way physics has built it.

And it's important to remember that our experience of the universe is always one step divorced from the reality of the universe, which is, in the end, our interpretation of a model we are building in our brain. or a direct experience is what we actually can count on. Everything else is our interpretation. Yeah. And if that makes you red with anger or blue with sadness, just close your eyes. Don't yellow at us. Yeah. Imagine a more beautiful universe of colors.

All right. Well, we hope you enjoyed that. Thanks for joining us. See you next time. For more science and curiosity, come find us on social media where we answer questions. and post videos. We're on Twitter, Discord, Insta, and now TikTok. Thanks for listening,

and remember that Daniel and Jorge Explain the Universe is a production of IHeartRadio. For more podcasts from IHeartRadio, visit the IHeartRadio app, Apple Podcasts, or wherever you listen to your favorite shows. December 29th, 1975, LaGuardia Airport. The holiday rush, parents hauling luggage, kids gripping their new Christmas toys. Then everything changed.

There's been a bombing at the TWA terminal, just a chaotic, chaotic scene. In its wake, a new kind of enemy emerged, terrorism. Listen to the new season of Law and Order Criminal Justice System on the IHeart Radio app, Apple Podcasts, or wherever you get your podcasts. My boyfriend's professor is way too friendly, and now I'm seriously suspicious. Wait a minute, Sam. Maybe her boyfriend's just looking for extra credit. Well, Dakota, luckily, it's back to school week on the OK Storytime podcast, so we'll find out soon. This person writes, my boyfriend's been hanging out with his young professor a lot.

He doesn't think it's a problem, but I don't trust her. Now he's insisting we get to know each other, but I just want her gone. Hold up. Isn't that against school policy? That seems inappropriate. Maybe. Find out how it ends by listening to the OK Storytime podcast and the IHeart Radio app, Apple Podcasts, or wherever you get your podcasts. Have you ever wished for a change but weren't sure how to make it?

Maybe you felt stuck in a job, a place, or even a relationship. I'm Emily Tish Sussman, and on she pivots, I dive into the inspiring pivots of women who have taken big leaps and their lives and careers. I'm Gretchen Whitmer, Jody Sweetie. Monica Patton, Elaine Welteroth. Learn how to get comfortable pivoting because your life is going to be full of them. Listen to these women and more on She Pips. Now on the IHeart Radio app, Apple Podcasts, or wherever you get your podcasts. This is an IHeart podcast.