The Darkest Dark

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So when we're at sea, beyond the ship lights, it's absolutely dark.

Especially if it's a cloudy night.

I mean, it's as dark as anywhere you can get on the planet.

If they turn out the lights on the ship, I mean, it's just astonishing.

You know, when you're there in, like, complete darkness.

It's a funny presence.

It's hard to describe, but you do feel like, you know, it's there and it's like, I don't know, it sounds weird.

It's probably left over some terror of the dark we have.

Who knows?

But yeah, you feel like it's asking you something.

Hey, it's Molly Webster. This is Radiolab.
We're in the middle of deep winter. The shortest day of the year just happened.
And, you know, when the sun sets at 430, it can feel like a wall just kind of descends outside of my apartment, just like an impenetrable wall of blackness. And it can feel like that there's just nothing out there.
There's nothing beyond it. There's nothing in it.
It's just kind of this black void. And this is a lovely annual spiral that I get to go down until this year when I bumped into the guy you just heard from.
His name is Sanka Johnson. He's a biologist at Duke University.
And he told me a story that has me reimagining darkness this winter. And so this episode is that story, and we're going to start with Sanka out at sea on the back of a boat.
I mean, I always like to say that everybody wants to go to sea once, and maybe one out of a hundred ever wants to go againickness and all those things are kind of real. But the people who want to go again, I mean, they really want it.
We just have this passion for being out there and not just the ocean and not just the animals, but the life on the ship is like its own special sort of strange thing. How so? Well, everything is decided for you.
I mean, you don't get to decide breakfast. You don't get to decide lunch or dinner.
You live in a very small room. I mean, one of my rooms was so small that the bottom half of my bed actually went into the wall.
And so I would crawl in, and my upper part of my body was still in a room, and other half was like dug into the bowels of the wall of the ship. And, yeah, extremely industrial.
If you like trees or anything green or anything like that, it's just, you know, a pile of steel. A bit like an oil rig platform without the oil, but it's still got the smell.
I mean, it smells really. Oh, really? Well, it smells intensely of diesel because of it.
Well, that's how you move the ship, right? You know, there's this giant engine, a giant diesel engine engine i guess i just thought it like went somewhere else i don't know like it went off the back of the ship and didn't engulf you or something no it goes right through your head wow you've really painted a picture here you know my wife always says that we need to stop calling it a cruise because that it makes it sound like a pleasure cruise when it's really more like working in a sort of a factory of sort, you know, out in the middle of nowhere. And what Sanka is doing out there is releasing these giant nets off the back of the ship and the nets get lowered down deep, deep, deep, deep, deep into the sea, like we're talking 10,000 feet almost.
And they're trying to capture these creatures that live in a world where light and dark play out a battle of life and death. It's pitch black.
You won't see anything. And so 80 to 90 percent of the species down there can make light.

They're running around with little flashlights under their eyes and shining them forward to look for things.

They're fishing with light.

You know, they're using their own light and the light of others to basically find each other and most of the time try to eat each other, every now and then try to mate.

Some of these animals, their whole body is covered with lights. And so, you know, we're collecting these animals in one way or another, and then we photograph them in a dish, and literally it usually takes about one to two hundred shots to get a nice shot of an animal.
Wow. It's a very frustrating process.
Loved doing it, but there was this group of animals that we simply could not get a good photograph because they were just so, I mean, basically incredibly black. To the point which, you know, when you took a picture of them, all you saw was like a black shape in the middle of the picture.
You're not seeing gills. You're not seeing fins.
You're not seeing, you're just- Yeah, you're just looking at what looks like a two-dimensional cutout shape of a fish. Normally, when you look at things, and we take it for granted, even when we look at things that are quite black, we see the shape of it.
Like, you know, one of the, weirdly enough, one of the darkest things in our lives is a new automobile tire. And when you look at a tire, I mean, it looks like a tire, right? So this just, I mean, you really feel like when you look at some of these fish, you're looking through them into a hole, into absolute nothingness.
Wow. Okay.
So what are the certain fish or species? One, they're called the dragonfish, and they're sort of like the evil fish predators of the deep. They're kind of long and skinny, and they're lit up with a few lights on their bodies, and they tend to have pretty impressive teeth that are so long that they actually have slots in their forehead so that they can close their jaw without the teeth punching into their brain.
They slide their teeth into their skull. Yeah.

So when, you know, they shut their jaw, I mean, if they didn't do this, they would literally impale their own brain with their teeth. That is going to be the best thing I hear all day.
And the other group were the anglers that, you know, people saw in Finding Nemo where they're hanging a little bioluminescent lure on a basically a little stick, you know, over their face. And so if the angler isn't extremely dark, that bioluminescence lights up its body, which makes it not a very successful lure.
So, you know, you imagine you're some poor little fish, you swim up to see this nice, tasty looking bioluminescent sphere. And then, you know, you see a pair of, you know, big eyes and a giant body and all this other kind of stuff leering back at you, you're probably going to back off.
And so anglerfish need to be really dark so that they avoid lighting themselves up. That's fascinating.
So it's not even necessarily, sometimes I think really dark to blend in or something. Well, it is.
Any light you make is going to give you away. It's like you're surrounded by enemies.
And if you give anything away, they're all going to come for you. Oh my gosh.
It's like that horror film, like The Quiet Place. Yeah.
It's exactly like that. It's like a very tense world because the fish is working incredibly hard not to be lit up by its own lure.
I mean, once we measured it, two things about them really surprised us. One was they were the darkest things that had ever been measured on the planet.
Oh my gosh. Yeah.
They're about a hundred times darker than anything that you consider dark in your normal life. You know, like I said, you know, a new automobile tire is actually one of the darkest things you see.
And then, you know, like whatever, a black table or, you know, any of the black things in your life typically reflect, you know, a few percent of the light. And these were about 100 times better than that.
Their black is the blackest known technological substance, which is this stuff called Vantablack. Is the fish darker than Vantablack?

They're kind of equal.

They're all at a... I'm totally jumping in here just to say for anyone who has not seen Vantablack,

Sonka and I did some Googling of it.

It's like this essentially spray on black carbon that if you put it on a surface,

it like disappears the thing that you paint it on. So it ends up looking like you're looking at a black hole.
A friend of mine bought some of the Vantablack and the problem with the Vantablack is the second you look at it, dust starts to fall on it. And so then, you know, the surface ends up being a lot more reflective than you want.
And the only way to get it on is to sort of cook it on in this like hot vacuum, which is not great for lots of things. And here, you know, these animals are absorbing nearly all the light and they're still able to swim around.
It's really rugged. It's really robust.
Wow. Okay, so you're staring at the blackest black and you're not like, all right, job well done.
No. We've done it.
No, no, no, not quite. What happens next? I mean, the other thing, yes, we sort of learned in the measurement was, and this kind of blew us away because, you know, people talk a lot about natural selection and evolution and how, you know, animals, you know, have a strong pressure to increase their ability to do something.
And we noticed that even though, you know, across the entire spectrum, you know, these

animals are extraordinarily black, blacker than just about anything that's ever been

out there, they were about three to four times as black right in the area where the

bioluminescence was.

Oh.

Which showed you that even though they were just about perfect, natural selection was

pushing them to be even more perfect.

And it gave you an idea of just how ferocious, you know, the pressure is down there to be, you know, you know, as good as you can be in this way, you know, to camouflage yourself as well as you can. So we knew they were fighting really hard and we wanted to know how they were doing it.
Like how do you create the blackest black? Yeah, exactly. You know, if they're fighting that hard to do it, they must be doing something pretty cool.

The journey to discover that very cool thing takes Sanka from butterflies to the moon and completely shifts around my understanding of darkness.

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Investing involves risk, performance not guaranteed. Hey, it's Molly Webster.
This is Radiolab. We are talking to Sonka Johnson, who is finding himself staring at some incredibly black fish.
They're like the black holes of fishes and he's trying to figure out, he wants to figure out, how do they get this dark? The trick is he maybe sees one of them every two or three years. So in order to set off on his quest of figuring out how the fish get so black, he actually has to start by looking at another animal.
So we wanted something that was easier to get, but nevertheless, you know, still quite black. And we had heard that maybe there were some butterflies that parts of their wings were really black.
And we thought, well, wow, you know, we could work with that. Hi.
Where did you hear that? Funny enough, a really amazing insect biologist who is interested in the color of butterfly wings is like 50 feet down the hall. And so he pulls out this beautiful butterfly called a Brooks bird wing that's mostly green, but parts of it around the green are extremely black.
So then you're just like, how? Yeah, exactly. Because, you know, the first thing you might think is, well, if you want to make something really black, you know, just keep adding more and more pigment.

Like if you want to put something really black on like a painting or something, just keep adding more and more black paint.

Turns out that doesn't work.

So like if, you know, you can have a coffee table that is absolutely soaked with some sort of really black pigment.

And it's still kind of shiny when you look at it in a lot of directions.

And the fish, the fish were not shiny at all.

Neither was the butterfly wing.

Remember, it'll be a lot of directions. And the fish, the fish were not shiny at all.

Neither was the butterfly wing.

Remember, it looked like that void.

So Sanka and his grad student stuck the wing under a microscope

to try and figure out what was going on.

And what they saw was not a void at all.

Yeah, it was really cool.

It was like this beautiful honeycomb array. Like those Czech cereals, except it sort of went in all directions and it was very, very small.
So there's a whole bunch of little holes and they had a really particular size, being about the size of a wavelength of light. And we got all excited about that because once it gets through,

it's like there's this undercarriage that's like this crazy pinball machine

where the light just sort of bounces around, you know, sort of unhappily

and can never find its way back out the hole.

Like if you fell through a hole in the ice and you're trying to swim around,

and so your chance of actually getting back out of the ice is really low.

So turns out to make something really dark, you also have to mess with the structure of it. You have to kind of create a weird little forest where photons go to die.
There's some things going on with pigments, but for the most part, it's just about how this butterfly wing is made at a microscopic level. And we really had that hammered in when Alex took some of this, you know, black and green part of the wing, and he did a certain kind of microscopy that requires that you first spray kind of like a gold coating on top of them.
Okay. And normally that makes whatever you spray, well, it looks kind of gold.
It looks like it just got sprayed with metal, like, you know, like the Tin Man and the Wizard of Oz. And they were still black and they were still green.
So, it didn't matter. You spray all this gold on it.
Really? Yeah. They were just perfectly black still, which meant that even though we had covered up all the color, you know, all the pigment, but we left the structure, the structure alone was enough to keep the wing completely black.
Like's, it's like so, you're really diving deep into actually like what color is. Yes.
It is a hard concept for my brain to think structure. It's really thinking about the physics of color, right? Yeah, exactly.
Which you don't often think about. You just think there is a color, there's a paint, there's a thing and I put it on something and it is that.
But like the idea that it's that you could cover up the color and the structure could still make a color. Yeah, it's like what gives them their beautiful green color or blue color or whatever is actually when you look at them in a microscope, they're just a forest of funny little structures.
Really? And those little structures preferentially reflect certain kinds of light. And in the case of the black parts, they basically, they reflect nothing.
But what we really wanted to do is get back to the fish because, you know, we really like the fish. And so, you know, at this point, we knew that they had to be doing something really special with their structure.
And we wanted to know what that was. And we expected to see something kind of like what we saw in the butterflies.
Like the honeycomb forest. Yeah, something like a honeycomb forest or like this, you know, this crazy pinball structure or something to suck a ball light.
And it wasn't what we saw at all. Instead, we saw this, basically it's, I mean, I don't know how many people still eat Tic Tacs.
But, you know, imagine if you don't eat Tic Tacs. You're talking to a person that will still eat a Tic Tac.
I love Tic Tacs. Or, you know, all those sort of mints.
You know, they're sort of shaped, you know, kind of like an oval. It's like mini, mini pills.
Mini, mini pills. Yeah, like tiny pills, right? And they're all piled together.
And that's pretty much what we saw, which- Wait, you saw that in the fish? In the fish, inside the fish skin. And so, in each one of those little Tic Tacs, it's something called a melanosome.
It's like a little structure that holds melanin, you know, the thing that makes many animals dark. Whoa, wait, okay.
So is a melanosome a cell or it's something that's inside a cell? It's something inside a cell. Typically inside a cell, it's pretty small and it's shaped like a tic-tac and it absorbs light.
And normally when you're looking at an animal that's dark, there are a few of these melanosomes in each cell. But in this case, there was this massive proliferation of them.
You know, they're just, they like the fish, they just sort of went nuts and, you know, just sort of making tons and tons and tons of these things to the point where, you know, the whole inside of the skin of the fish was just this crammed together pile of melanosomes.

And we knew that wasn't enough.

Like I said before, having a lot of pigment isn't enough to make something really dark.

You have to have the right structure to go with it.

And we thought that was going to be really easy to figure out, like, what's going on.

I mean, this involved basically a bunch of math.

The problem is it's not so hard to understand how light interacts with a particle when it's all by itself. But it's really hard to understand what it's doing when it's all in a pile.
Because all the little things in the pile, they all interact with each other. It's like, you know, if you throw a rock into a pond, you get this beautiful, expanding, circular front of

waves. Now, imagine you throw like 10,000 little pebbles into the pond.
Then you get this really

complicated mess. And that's what we were trying to figure out was the complicated mess.
And I

think I was looking for, you know, technical ways of solving that mess. And weirdly enough,

I kept getting pulled back to people who were studying the full moon, which we did not expect at all. I just thought you were going to be like, yeah, and then one day in October, we figured out the math problem.
No, no, no. So when you would scientist Google a whole bunch of tiny particles piled on top of each other, light, you would get like articles about the moon.
Yes. And in the beginning, it kind of surprised me.
I was like, why do they keep bringing it back to the moon? Yeah, because I think of the moon and I think bright. I don't think black.
So I wouldn't be like, I'm going to look at the moon to solve this black problem. Turns out the soil of the moon, the regolith, is not so different in terms of the shape and size and refractive indices and absorption of these black fish.
And so the math that was developed for the moon could be adapted to study what was going on in the fish. And so what did it tell you about the fish? Like what? Basically, what we did is we were able then using that math to run a million different simulations to basically see the size of the particles was sort of the perfect size for making the fish as black as possible.
And then we found out that not only were the, you know, the little tic-tacs the right size, but they were actually pretty much exactly the right shape, which was really cool because that shape and size was very different from the melanosomes you see in all the other animals. And so, you know, these black fish were actually, you know, fine-tuning, you know, the shape and size of these little things.
So that once the light got into this sort of gumball pile of, you know, these Tic Tacs, it would just scatter around forever.

And every time it bounced into another melanosome, more of it would get sucked up. The light would more or less get lost.
and it ended up having a lot of implications for engineers who wanted to build things like this

to make you know really um black things you know that they can use in cameras and spectrometers and a ton of other equipment. People have like engineers have co-opted this research? Yeah, we see papers on it.
Lots of engineers like try to make little tic-tacs that they're, you know, spraying on different surfaces or incorporating different surfaces to make really dark materials. You know, solar cells are a really big deal because, you know, everyone's trying to optimize the amount of, you know, electricity you can get out of a solar cell.
But then also a lot of the sort of the internal parts of things that we use involving light, you know, cameras and things of that sort. It turns out there are a surprising number of people who are interested in making light go away.
So can you photograph an anglerfish now? No, we still can't do it. But now we know why we can't get a good picture.
I mean, that was kind of it. I mean, you know, we were able to solve, you know, come up with the answer about, like, why we couldn't get a good picture.
And we could figure out how the animals could do it. And it helped us understand a little bit more about sort of the hide-and-seek game in the deep sea and how deadly serious it is.
That, you know, animals will go to these extreme, you know, sort of adaptations just to avoid being seen by, like, a little bioluminescent flashlight. So you just, of all, like there's so many things you've done in your life and like one of them was you're just staring at the darkest color on the planet.
Yeah. Well, I mean, one of the things our lab studies a lot are like things like coloration, iridescence, bioluminescence, and all that kind of stuff.
But one of the things we always ignored was, you know, these sort of non-color things, like basically the absence of color, like being extremely black. And so it was a really neat new thing to look at.
And it got us really excited when we could see, you know, something that made ecological sense, you know, in these animals having to hide and something that just ended up with such a striking result. Yeah, it is so cool.
You're in a world where you're probably lured to the lures and then you've been staring the whole time at the black is black. Yeah.
Yeah. I mean, I always say that, you know, we're, you know, as humans, we're attracted to certain things.
And we ignore the thing that actually matters.

So, like, for example, when we look at something red, we really focus on the fact that it's red.

But biologically, what's really happening is something is taking away all the blue and green and yellow light.

And that's the actual part that matters.

And so what we see is actually the opposite of what's really happening. What that means is that the darkness, whether you're talking about a fish or the looming gloom outside of your window.
What feels like an emptiness, Sanka saying that it actually contains multitudes.

And not just that.

It is a place where all the light falls inside of it.

So in a way, the darkest thing is also the brightest.

Blackness, at least in my experience, is not an emptiness,

but has an incredible presence.

It feels very rich, like it's the ultimate substance. This episode was reported by me, Molly Webster.
It was produced by me, Rebecca Lacks, and Pat Walters. It was edited by Pat Walters.
It was fact-checked by Natalie Middleton with mixing from Jeremy Bloom. We also featured music by Norwegian pianist Vettel Nara.
Before we go, two fact clarifications. dragonfish fact, are not the fish that have fangs that slide back into their skulls.
That is the fangtooth fish. Fangtooth fish can also be ultra black.
In fact, all of these fishes are some of the darkest things measured on the planet, but they are not the only dark things.

We've seen ultra black in insects and in birds.

To read more about all of this, head on over to our website. And for all of you tech heads out there, you probably know that by now there are new man-made substances that are actually darker than Vantablack.
All of that's at radiolab.org. And that's it.

I'm Molly Webster.

This is Radiolab.

And I'll see you out there in the dark.

Does that sound creepy?

Thanks for listening.

Bye.

Hey, I'm Lemon, and I'm from Richmond, Indiana.

And here are the staff credits.

Radiolab was created by Jad Abumrad and is edited by Soren Wheeler. Lulu Miller and Latif Nasser are our co-hosts.
Dylan Keefe is our Director of Sound Design. Our staff includes Simon Adler, Jeremy Bloom, Becca Bressler, W.
Harry Fortuna, David Gable, Maria Paz Gutierrez, Cindy Nyanan-Sambandan, Matt Kielty, Rebecca Lax, Annie McEwen, Alex Neeson, Sarah Kari, Sarah Sandback, Anissa Vitsa, Arianne Wack, Pat Walters, and Molly Webster. Our fact checkers are Diane Kelly, Emily Krieger, and Natalie Middleton.
Hi, my name is Teresa. I'm calling from Colchester in Essex, UK.
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