May 21, 2012

Rippin' the Rainbow a New One

We tear into this show with a dark scene from 1665. A young Isaac Newton, hoping to ride out the plague by heading to the country to puzzle over the deep mysteries of the universe, finds himself wondering about light. And vision. He wants to get to the bottom of where color comes from--is it a physical property in the outside world, or something created back inside your eyeball somewhere? James Gleick explains how Newton unlocked the mystery of the rainbow. And, as Victoria Finlay tells us, sucked the poetry out of the heavens.

Jonah Lehrer restores some of the lost magic by way of Goethe--who turned a simple observation into a deep thought: even though color starts in the physical world, it is finished in our minds.

Which, thanks to Mark Changizi, brings us to a very serious question: what do dogs see when they look at the rainbow? We humans see seven colors: red, orange, yellow, green, blue, and violet (ROYGBiV!). But as Thomas Cronin and Jay Neitz--two guys who study vision--explain, that's just a sliver of the spectrum. Along the way, we get some help imagining the rainbow from a choir, and we meet a little sea creature (pictured below), who with 16 color receptors, blows the rest of us earthlings out of the water. 

Mantis shrimp

Mantis shrimp, photo by ursanate/flickr-CC-BY-2.0

UPDATE: In the years since we first aired this episode, more research has gone into these amazing little creatures and there is new evidence to suggest that while the Mantis Shrimp has all the parts necessary to see a Super Duper Rainbow, they may not, in fact, be engaging this potential. Curious? Check it out!



Read more:

James Gleick, Issac Newton

Victoria Finlay, Color: A Natural History of the Palette

And be sure to check out The Oatmeal's amazing amazing post, "Why the Mantis Shrimp is my new favorite animal," inspired by this episode. 

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Opening theme:           You're listening to Radiolab from WNYC and NPR.

James Gleick:               And I assume we're live on the air now.

Jad Abumrad:               We don't do live.

Robert Krulwich:          Have you guys ever talked to each other?

Jad Abumrad:               I don't think so, no.

Robert Krulwich:          So this is Jad Abumrad.

James Gleick:               Well hi.

Robert Krulwich:          This is Jim Gleick.

Jad Abumrad:               Hi, how are you?

James Gleick:               Fine, how are you?

Jad Abumrad:               Pretty good, pretty good.

Jad Abumrad:               Rainbows, rainbows. Okay, so we're going to start today with author James Gleick.

James Gleick:               As I recall, you wanted to talk about Isaac Newton.

Robert Krulwich:          That's right.

Jad Abumrad:               We did call him to talk about Isaac Newton, but more specifically colors.

James Gleick:               All right, Isaac Newton, he's 23 years old.

Jad Abumrad:               1665.

James Gleick:               And he's home for the holidays. No, there's no holiday, he's home for the plague.

Jad Abumrad:               There was actually a plague, they sent everybody home from school. In any case, he's in his room, famously solving all of these mysteries of the world. And one of the questions that he thinks about during this break is ...

James Gleick:               What are colors? Where do they come from?

Robert Krulwich:          When I see the color red, is that red inside my head, or is it something that exists out there in the world?

James Gleick:               Is the light without, or is the light within?

Robert Krulwich:          So he pokes a knife into his eye.

Jad Abumrad:               He what? What do you mean?

James Gleick:               Here's what Newton wrote in his notebook.

Speaker 5:                    I took a bodkin, put it betwixt my eye and the bone as near to the back side of my eye as I could, and pressing my eye with the end of it ... there appeared several dark, white, and colored circles.

Jad Abumrad:               Did that lead him to some conclusion about where the spots live, whether they're outside or inside?

James Gleick:               No, this didn't get him very far.

Jad Abumrad:               Because seeing spots when you poke your eye doesn't tell you much about what color is. But what he did next did, and this one he's a little more famous for.

James Gleick:               He got himself a prism, which is just a bit of glass shaped like a pyramid. It wasn't so easy for him to get his hands on a prism, but he did.

Robert Krulwich:          Then he shut his blinds so the room was totally dark, but he poked a little hole in one of the blinds. And then he waited.

James Gleick:               The sun had to be at just the right angle.

Robert Krulwich:          And he waited. And when the sun got to just the right spot, a ray of light shot through the room. Newton immediately stuck his prism into the light, and the light shattered ...

James Gleick:               ... and became a rainbow on the wall.

Jad Abumrad:               Or, in Newton's own words ...

Victoria Finlay:             A colored image of the sun. Now that's gorgeous, isn't it? A colored image of the sun.

Jad Abumrad:               That's Victoria Finlay, she wrote a book about color, and she says, “The thing to understand about this experiment is that at the time people believed that white light ...”

Victoria Finlay:             “... was given by God, or given by this amazing thing called nature.”

James Gleick:               The light from the sun was sort of holy. If there was anything that was pure, it was white.

Jad Abumrad:               So, when the prism did the rainbow thing, which people knew prisms did, they just figured ...

James Gleick:               ... the colors are in there in the glass.

Jad Abumrad:               In other words, that rainbow had nothing to do with the light itself, that was just the prism ...

James Gleick:               ... adding some kind of impurities to the light.

Robert Krulwich:          Oh wow, I hadn't thought of the possibility that the prism is muddying the light, it's polluting the light.

James Gleick:               Yeah, how do you know that the prism isn't generating these colors? So he got a second prism, and this was the trick.

Jad Abumrad:               While the first prism was still making that rainbow on the wall ...

James Gleick:               ... he moved a few feet away and he held up a second prism in the blue area to see what would happen to the blue light.

Jad Abumrad:               Would the prism add more colors to the blue light?

James Gleick:               Or would it be transformed in some other way? And what he found was ... nothing happens. It remains blue.

Jad Abumrad:               So he thought, “Hm, if the blue light isn't getting muddied by the prism, then maybe the prism wasn't muddying the white light to begin with. Maybe that rainbow of colors was actually coming from inside the white light.”

James Gleick:               He inferred that the first prism is dividing light into its constituent parts.

Victoria Finlay:             Which means that the white light we see around us is actually constituted of all of these colors.

Jad Abumrad:               The colors were in the light, they are the light. He had his answer: light is a physical thing in the physical world, you could tweak it, test it, study it. This was the beginning of everything we know about light today ...

James Gleick:               ... which Newton put us on the road toward finding ...

Jad Abumrad:               ... that ultraviolet rays, x-rays, radio waves, they're all different energies of light. And colors are just energies within that little sliver that we can see. And that has led to our understanding of the greenhouse effect, knowing what stars are made of, even the age of our own universe.

Robert Krulwich:          But not everybody was pleased by this.

Victoria Finlay:             Well, a little bit later, John Keats, a romantic poet, was really cross with him in a poem because they said he removed all the poetry of the rainbow.

Robert Krulwich:          And the real challenge to Newton's view of color, one that would really stick, oddly enough it did come from a poet. Not Keats, but the poet named Goethe.

Jonah Lehrer:               Yeah, he was this German romantic poet.

Jad Abumrad:               That is author Jonah Lehrer ...

Robert Krulwich:          ... a regular with us who writes about this kind of thing, always wonderfully.

Jonah Lehrer:               One day he is walking in the park, and he spots these yellow crocuses, and he looks at the yellow crocuses and admires their petals, it's early Spring and they're blooming. And then he quickly turns away.

Jad Abumrad:               And in an instant, he suddenly sees ...

Jonah Lehrer:               ... this dash of violet across his eyes.

Robert Krulwich:          He still sees the shape of the flower, but now it's violet. It's the opposite of yellow. He hadn't rubbed his eye, he hadn't stuck a needle in it, and yet there it was.

Jonah Lehrer:               It seemed just as real.

Robert Krulwich:          As real as the yellow crocus.

Jonah Lehrer:               And yet he knew it wasn't real, it came from inside his mind. And we've all hallucinated colors, you can press on your eyeball or close your eyes and you'll see this riot of fireworks. But for Goethe, that simple observation leads him to think that maybe color isn't simply about the external universe, and maybe our perception of colors began in the world. But maybe it was finished inside the mind.

Robert Krulwich:          And today, hundreds of years later, this is still an open question.

James Gleick:               A scientist can say color has an objective reality. But the colors we see are tricks of the imagination, and there is no perfectly objective view of color. Personally, I like to keep both of those opinions in mind at the same time.

Robert Krulwich:          Me too.

Jad Abumrad:               Me three. Well, lucky for us ... we're going to do a whole show of this.

Robert Krulwich:          You don't say!

Jad Abumrad:               I'm Jad Abumrad.

Robert Krulwich:          I'm Robert Krulwich.

Jad Abumrad:               This is Radiolab, and today ...

Robert Krulwich:          ... it's all about color. Where is color?

Jad Abumrad:               Is it in, is it out?

Robert Krulwich:          That's the question.

Jad Abumrad:               Yeah, we're going to explore that question through the eyes of a butterfly.

Robert Krulwich:          In the killing fields of Cambodia.

Jad Abumrad:               With a woman who may see colors the rest of us can only dream of.

Robert Krulwich:          And we'll go back to a time when the sea apparently looked like dark red wine.

Jad Abumrad:               Stick us in your earholes, because we're about to get colorful.

Jad Abumrad:               And by the way, just before we get rolling, I just want to say we did something kind of different for us while making this hour. We put out this call to a bunch of musicians - solo artists, bands - to send us their favorite color songs, their own interpretations of their favorite color songs.

Jad Abumrad:               We got an amazing response. So, throughout this hour, you're going to hear color songs of various kinds woven into some of the pieces, between the pieces.

Robert Krulwich:          Those songs, by the way, we have plans for.

Jad Abumrad:               Yeah, big plans. You can go to our website,, to get a full list of the songs.

Robert Krulwich:          And thank you, by the way, everybody who sent those songs in.

Jad Abumrad:               Absolutely.

Jad Abumrad:               Okay, so should we go?

Robert Krulwich:          Yes, so to get things going ...

Jad Abumrad:               Hey, here he is.

Robert Krulwich:          Not long after we talked to Jim Gleick about Sir Isaac Newton, we talked to a neuroscientist by the name of Mark Changizi ...

Jad Abumrad:               I'm going to chew grapes, if that's all right with you.

Robert Krulwich:          ... who had written a book about color.

Jad Abumrad:               Would you like some grapes?

Mark Changizi:              No thank you.

Robert Krulwich:          And we threw the question at him.

Jad Abumrad:               So, one of the debates that became interesting to us is this, “Where is the color?” Is it out there, is this grape, that I'm holding right now, is it red for everything? A bee, a whale? Does it exist in a way that you could pin down and say it's outside me, or does it only get to be red when it gets in my head?

Mark Changizi:              Well, a more severe way to ask this, and I ask this whenever I'm giving talks, is just, “Would aliens see it as red?”

Jad Abumrad:               Yeah, would aliens see it as red?

Mark Changizi:              Right, and the answer is almost surely no.

Jad Abumrad:               “The truth is,” says Mark, “even your dog wouldn't see it as red.”

Mark Changizi:              Your dog has color vision, has blue-yellow, and black-white.

Jad Abumrad:               Really?

Mark Changizi:              Yes.

Jad Abumrad:               So what would the world look like to a dog?

Mark Changizi:              If you've ever known a guy who's colorblind, and 10% of men are colorblind, that's roughly what it's like.

Jad Abumrad:               Huh.

Robert Krulwich:          Well here's a question: if a dog and a human and a crow were to be staring at a rainbow, would they be seeing very different things?

Mark Changizi:              Yes.

Jad Abumrad:               Now, this question that Robert just kind of tossed out during an interview, about how different creatures would see the rainbow, this ended up taking us down a little wormhole, and we ended up actually getting a choir to help us illustrate what we learned. But just to set a baseline, your normal rainbow goes like this, starting bottom up:

Jad Abumrad:               Three, two, one.

Choir:                           Red, orange, yellow, green, blue, violet.

Jad Abumrad:               Red, orange, yellow, green, blue, violet, ROYGBIV.

Thomas Cronin:            ROYGBIV, I don't know why people put the I in there, but that's it.

Robert Krulwich:          If you didn't have the indigo, you couldn't say it though, it'd be ROYGBV.

Thomas Cronin:            That's why you need the I, I think, is just to say ROYGBIV.

Jad Abumrad:               That, by the way, is Tom Cronin.

Choir:                           Hi, Tom.

Thomas Cronin:            I'm what's called a visual ecologist.

Jad Abumrad:               Mark suggested we give him a call. He told us that humans see seven colors in the rainbow.

Mark Changizi:              In the case of the dog ...

Jad Abumrad:               ... very different rainbow.

Mark Changizi:              It's going to start off ...

Choir:                           Blue.

Mark Changizi:              ... blue, he'll be able to see blue just fine.

Thomas Cronin:            So it would see a rainbow starting with blue.

Jad Abumrad:               Same blue we see.

Thomas Cronin:            And then grading off into green.

Choir:                           Green.

Jad Abumrad:               Same green as us.

Thomas Cronin:            And then disappearing. The rainbow would end there.

Jad Abumrad:               With a tiny bit of yellow thrown in.

Robert Krulwich:          That's it?

Thomas Cronin:            Yeah, so the rainbow would only be about half as thick as ours.

Jad Abumrad:               Wow, that's a sucky rainbow, dog.

Robert Krulwich:          That's why, when God promised that he would never deliver another deluge, and he made the promise in a rainbow, the dogs just were totally unimpressed.

Jad Abumrad:               And what is it about the dog eye that makes it see this way?

Thomas Cronin:            It doesn't have red-sensitive photoreceptors, no red-sensitive cones.

Jad Abumrad:               The weird thing is that the difference between dogs and us, cone-wise, is just one. They have cones tuned to blue and green, so do we, but we have this one extra: red.

Choir:                           Red.

Jad Abumrad:               Which doesn't really seem like a big difference, it's just one cone. But ...

Jay Neitz:                      To have three is so much better than two.

Jad Abumrad:               That's Jay Neitz, vision scientist.

Choir:                           Hi Jay.

Jay Neitz:                      Because of this multiplicative thing. Red can get mixed with blue.

Choir:                           Blue.

Jad Abumrad:               Which makes purple.

Choir:                           Purple.

Jay Neitz:                      Or red can get mixed with yellow.

Choir:                           Yellow.

Jad Abumrad:               To make orange.

Choir:                           Orange.

Jay Neitz:                      And green can mix with blue ...

Jad Abumrad:               ... to get teal, or turquoise.

Choir:                           Turquoise.

Jay Neitz:                      And that's how we get about 100 different shades of color that we can see. So, by adding one photopigment, instead of adding just one more color you actually add about 98 colors or so.

Robert Krulwich:          All right, let's move on. So now we have a crow, unless you'd like to change the bird.

Jay Neitz:                      Well, the crow is not so interesting because it's pretty much like us. So let's take something like a sparrow. Because sparrows have ultraviolet vision.

Robert Krulwich:          What do they see?

Jay Neitz:                      They see ... The rainbow starts before our rainbow starts. Where we just see sky, it would see an ultraviolet color.

Choir:                           Ultraviolet.

Jay Neitz:                      And then it would see the violet.

Choir:                           Violet.

Jay Neitz:                      Then it would see the blue.

Choir:                           Blue.

Jay Neitz:                      And the greens.

Choir:                           Green.

Jay Neitz:                      And the oranges.

Choir:                           Orange.

Jay Neitz:                      Well, the yellow first and the orange.

Choir:                           Yellow.

Jay Neitz:                      And then the red.

Choir:                           Red.

Jay Neitz:                      And probably would see further into the red than us because they have ...

Choir:                           Very, very red.

Jay Neitz:                      ... a more red-sensitive red receptor than we have.

Choir:                           Extremely red.

Jay Neitz:                      So they'd see a much broader rainbow. It would start earlier, and it would end later.

Jad Abumrad:               Whoo.

Robert Krulwich:          So, should we assume that the sparrow is the champion, that that's as high as it gets?

Jay Neitz:                      If you're talking about vertebrates-

Robert Krulwich:          No, I'm talking about anything that has a heart, and a mind, and a body.

Jay Neitz:                      Once you leave the vertebrates, then all bets are off. Many animals have much better color vision than the vertebrates do, yeah.

Robert Krulwich:          Oh really?

Jad Abumrad:               Like what?

Jay Neitz:                      Butterflies are a great example, butterflies have five or six kinds of color receptors, we only have three, remember.

Robert Krulwich:          Butterflies see more colors than we do?

Jay Neitz:                      Yeah.

Robert Krulwich:          So if a butterfly were looking at a rainbow ... I never thought we'd get here.

Jay Neitz:                      Well they do, I'm sure, butterflies are out there when the rainbows are out. But they would see colors we have no names for, between the blues and the greens, and the greens and the yellows.

Robert Krulwich:          So it would go from ultraviolet, it would see that.

Choir:                           Ultraviolet.

Robert Krulwich:          Then it would see violet.

Choir:                           Violet.

Jay Neitz:                      And then blue.

Choir:                           Blue.

Jad Abumrad:               And then blue-blue-green?

Choir:                           Blue-blue-green.

Jay Neitz:                      Yep.

Jad Abumrad:               And green-green-bluey-bluey, or whatever?

Choir:                           Green-green-bluey-bluey.

Robert Krulwich:          And then orange and red and all that?

Choir:                           Orange, red.

Jay Neitz:                      They have very complicated eyes.

Jad Abumrad:               Okay, so just to recap, here's the dog.

Choir:                           Green; blue.

Jad Abumrad:               Here's us humans.

Choir:                           Red; orange; yellow; green; blue; violet.

Jad Abumrad:               Now the sparrow.

Choir:                           Extremely red; very, very red; red; orange; yellow; green; blue; violet; ultraviolet.

Jad Abumrad:               A little bit more bass, a little bit more high end, so to speak. And finally, the butterfly.

Choir:                           Extremely red; very, very red; orange; yellow; green; green-green-bluey-bluey; blue-blue-green; blue; violet; ultraviolet.

Jad Abumrad:               Which is not so far above the sparrow, but it's got more mids in there.

Robert Krulwich:          So I'm now thinking butterflies get the crown.

Jay Neitz:                      Yeah, but then if you go onto coral reefs, you come across these animals called mantis shrimps.

Jad Abumrad:               What are they called, meta ...

Jay Neitz:                      Mantis, like a praying mantis.

Robert Krulwich:          Oh, mantis shrimp.

Jay Neitz:                      The shrimp catches prey using an arm like a praying mantis has. Mantis shrimps are mostly pretty small, about the size of a finger, some get to be as big as your forearm, big animals.

Jad Abumrad:               I'm actually looking this up right here. Oh my God, they're so colorful.

Jay Neitz:                      They are colorful, though.

Jad Abumrad:               Here, look at this. Oh my God, they're just ... It's like they're electric-colored.

Robert Krulwich:          They're like turquoise, or something.

Jad Abumrad:               Iridescent. And their eyes are like little cartoon eyes, they're gigantic.

Jay Neitz:                      Yeah, they have two really big eyes right on the front.

Jad Abumrad:               And you said that dogs have two cones, we have three, how much does the butterfly have again?

Jay Neitz:                      The butterfly has five, depends on the butterfly. Mantis shrimps have 16.

Robert Krulwich:          Sixteen?

Jad Abumrad:               Oh my God.

Robert Krulwich:          If you have 16 ...

Jay Neitz:                      Sixteen kinds of receptors.

Jad Abumrad:               What would the rainbow look like to them? Could they even see it?

Jay Neitz:                      A mantis shrimp would see a rainbow fine, because they live in very shallow water, and so the water's pretty clear, almost like air. They would start the rainbow way, way, way inside where we see violet, they would see ...

Choir:                           Super-duper-ultraviolet.

Jay Neitz:                      Extraordinarily deep ultraviolet. And then they would go on through several kinds of ultraviolet, probably five or six kinds of ultraviolet.

Choir:                           [crosstalk 00:15:49].

Jay Neitz:                      And then we would get to violet.

Choir:                           Violet.

Jay Neitz:                      Now they're reaching our colors. And go through violet, blue, blue-green.

Robert Krulwich:          Would they have those green-green, blue-blue-blues as well?

Jay Neitz:                      Yep.

Choir:                           Green-green; blue-blue-blue; yellow; orange.

Jay Neitz:                      And then they would go out into the reds. They would be about as red as us when they got to the red end.

Robert Krulwich:          But only in the reds.

Jay Neitz:                      Yeah.

Choir:                           [inaudible 00:16:12].

Jad Abumrad:               What a rainbow that must be.

Robert Krulwich:          Yeah.

Jay Neitz:                      They have the most complicated visual system of any animals by a factor of two or more.

Jad Abumrad:               Wait, you said any, do you mean that unequivocally? Any?

Jay Neitz:                      Yeah, no other animal that we know of has a visual system within 50% as complicated.

Jad Abumrad:               All right mantis.

Choir:                           Mantis shrimp.

Jay Neitz:                      But you know, on the other hand, their brains are tiny, so who knows what it turns into.

Jad Abumrad:               They may not have the ability to perceive the beauty of the rainbow in the way that ...

Jay Neitz:                      I don't know, mantis shrimps are into violence, they're not really into beauty. They go around and kill things. Really, that's what they do, that's one reason they're so fascinating. They love to go around and kill things.

Robert Krulwich:          What do they kill?

Jay Neitz:                      Crabs, other mantis shrimps, shrimps, octopuses.

Jad Abumrad:               They'll kill octopuses?

Jay Neitz:                      Yeah, small ones. A good-sized mantis shrimp can break the wall of an aquarium?

Jad Abumrad:               Really?

Jay Neitz:                      Yeah, there's ones in California that can break aquarium walls if they hit it hard.

Jad Abumrad:               Oh my God.

Robert Krulwich:          So you have a pugnacious Muhammad Ali seagoing animal with incredibly great visual sense.

Choir:                           Mantis shrimp.

Jad Abumrad:               Special thanks to Jim Briggs, our engineer for the choir session, which was a blast.

Robert Krulwich:          To Mark Changizi for sending us off in this direction.

Jad Abumrad:               To Michael Kerschner and the Young New Yorkers chorus.

Robert Krulwich:          And John Maclay and the Grace Church Choral Society, and those folks from the Collegiate Chorale and the Dessoff Choirs who joined us.

Jad Abumrad:               And to Alex Ambrose of WQXR for getting everybody together.

Robert Krulwich:          Thank you, thank you, thank you.

Choir:                           Hallelujah.

Robert Krulwich:          Okay, a very quick update. Since we aired this broadcast, the mystery of the mantis shrimp eye has just gotten deeper. As we mentioned, they don't seem to gaze at sunsets or rainbows. We now think that maybe they use colors as kind of triggers for particular actions. One color says fight, another color says eat, another color says sex. They still have the best eyes in the world, but what they're doing with those eyes is a bigger mystery now than ever.

Speaker 13:                  Start of message.

Thomas Cronin:            Hi, this is Tom Cronin.

Jay Neitz:                      Hello, this is Jay Neitz.

Choir:                           Radiolab is supported in part by the National Science Foundation.

Jay Neitz:                      And ...

Thomas Cronin:            And the Alfred P. Sloan Foundation.

Jay Neitz:                      Alfred P. Sloan Foundation.

Thomas Cronin:            Enhancing public understanding of science ...

Victoria Finlay:             ... science and technology ...

Choir:                           ... in the modern world.

Victoria Finlay:             More information about Sloan ...

Thomas Cronin:            ... at www.sloan ...

Victoria Finlay:             ... S-L-O-A-N ...

Thomas Cronin:            ... .org.

James Gleick:               This is James Gleick. Radiolab is produced by WNYC ...

Choir:                           ... and distributed by NPR.

Victoria Finlay:             Okay, hope that's good enough for you.

Thomas Cronin:            Bye.