How Nature Creates Colors That Aren't Really There (1)
- Thank you to Brilliant for supporting PBS.
Hey, smart people.
Joe, here.
I need to talk to you about a bird.
- Our biggest wow factor is probably
this crimson topaz here and so-
- That's not real.
Hold on a second.
Did you see that?
- The camera. - That looks fake.
I also need to talk to you about a bone.
- [Jeffrey] So this is actually a whale bone
from Australia that in fact has been opalized.
- Every part of what you just said is ridiculous.
That's probably the coolest fossil I've ever seen.
And we need to talk about all these beetles.
Turns out you can order dead bugs off the internet.
(Joe laughs)
(beetle clatters)
I've been ordering a lot.
All of these have one incredible thing in common,
and it is nature's greatest color trick.
In past videos, we've taken a deep dive
into some really mind-blowing ways that nature makes color.
We've looked for the blackest black.
We've asked why blue is the rarest of all colors,
but I've been saving this color trick until now
because, well, I think it might be the best one.
(curious music)
This is a phenomenon called iridescence.
It means rainbow colored.
We find iridescence in loads of places.
Here, here, here too.
And there, also there,
even in that dirty puddle out in the parking lot.
But why?
Now, color has many functions in nature.
Sometimes it's for getting attention,
sometimes for staying concealed,
and sometimes for reasons we don't understand.
But iridescence is uniquely mind-blowing
because the colors that we see aren't really there.
They come from a weird trick of physics.
To figure out how it works,
I asked a beetle expert, a bird expert,
and a rock expert to show us some
of nature's most incredible examples of iridescence.
It turns out if you go to a huge awesome museum
like the National Museum of Natural History
in Washington D.C., they have entire rooms
full of awesome colorful stuff to show you.
We started in the bird wing.
(crickets chirp)
Get it?
(crickets chirp)
Bird wing.
(crickets chirp)
Okay, sure.
So peacocks get all the attention
when it comes to iridescent plumage,
but I think that the fanciest rainbow feathers
belong to the smallest members
of the living dinosaur family, hummingbirds.
- They're gorgeous, unbelievable.
Our biggest wow factor is probably this crimson topaz here.
- That's not real.
Hold on a second.
- Gives you a flash at the camera.
- Did you see that?
That looks fake.
It looks like somebody made a hummingbird
in a lab and said, "This would be cool."
Why do hummingbirds have these amazing colors?
- So hummingbirds, we think,
it's always a we think in science, right?
We think that hummingbirds have these amazing colors
because largely they're using them to attract mates,
picking who they might wanna have offspring with
based on who is the prettiest
because pretty might indicate best genes,
best ability to find food,
best ability to care for offspring and so-
- You don't have a lot parasites crawling all over you,
which I know- - Exactly.
- is a big problem in dating.
These look really cool.
There's like purple and green and everything.
- These are beautiful.
The different body parts of these birds
have different iridescent colors on them.
You get these brilliant greens on the body
and these really beautiful roses and violets on the tails.
- I mean, I can see how this would get attention
in the hummingbird dating community.
What is happening inside of these feathers
that helps create these colors?
- It's just a little bit of a trick of physics.
There are three things that make up the basics
of this iridescent color in these hummingbirds.
Melanin, which is the same pigment that colors your hair,
keratin, which is what makes up the feather,
and also similar to your fingernails and air.
- The way that light dances off of hummingbirds
doesn't come from the color of the pigment
in those feathers.
It comes from how the feathers are built.
Now, if we could shrink ourselves down
to the nano scale and look at them up close,
what we'd see is millions of these pancake shaped structures
in these orderly little pancake stacks
all packed with tiny air bubbles.
When waves of light enter the feather,
they bounce off of those layers.
Now, when light waves overlap, they can interfere
with each other in different ways,
depending on the wavelength of light,
the angle that it enters,
the crests and valleys might cancel each other out
to dim the color or make it disappear altogether.
But at certain angles for certain colors of light,
sometimes those waves line up
and are added together to make the reflected color
even more vibrant.
All of the light enters,
but only some light is allowed to come out.
So when you look at the feather from different angles,
different waves of light line up
as they're bounced back to your eye.
That is what creates the sensation
of shimmering, changing color.
- Yeah, that's the fundamental definition of iridescence
is that the color changes
depending on the direction that you are looking at it.
- Wow, that's pretty fancy.
Not bad for some little dinosaurs.
Okay, so hummingbirds are cool,
but they aren't the iridescent royalty
of the animal kingdom.
That title probably belongs to beetles.
Biologist J.B.S. Haldane once said
that if nature did in fact have a creator,
he has an inordinate fondness for beetles
because beetles make up a quarter
of all known animal species,
and beetles themselves seem to have
a particular fondness for iridescence.
Not every beetle is iridescent,
but the thousands that are,
they have some of the most unbelievable colors in nature.
I mean, honestly, if you didn't know
that some of these were real,
you'd be forgiven for thinking that they were painted
by an artist or a YouTuber trying to trick you.
But they are real.
The outer layer of a beetle's body
is made of this super stiff polymer called chitin.
And when light hits these layers,
it bends through a process called refraction.
Just like when we look through a glass of water,
the light waves seem to bend and not quite line up.
Same thing happens to light in this beetle's outer shell.
If those layers are spaced out just right,
we're talking a couple hundred billionth of a meter apart,
certain colors of reflected light waves will interfere
and only certain colors of light escape at certain angles.
Sometimes, those refraction reflectors
are in the farthest outer layer of the beetle's body,
or they can be buried a little bit deeper inside.
That's what creates the huge range
of iridescence that we see in beetles.
For instance, this one looks
like a greenish reddish rainbow,
but this one here, you hold it to light,
it looks like a hologram.
But being shiny and iridescent may look cool,
but one of the most important questions we have to ask
in biology is why something is the way it is.
Turns out, these flashy suits of armor
may have some surprising functions.
- You're probably thinking,
"Oh, how could this possibly be useful
as a defense or camouflage or something?"
We're pretty sure that nature doesn't bring
about any kind of a change that doesn't have a purpose.
And in most cases, you know,
the really bright metallic greens
or living places with lush green forests
with a lot of residual water,
so being shiny and reflective in just the right habitat
and just the right ecosystem can actually be beneficial.
So the same beetle, if you are six feet from it
may be really visible, but if you move back just 10 feet,
it will start to fade into the background
because of the way that the light is playing with it
and the position you're in observing it.
It's also easy for us to sort of look at this
from the standpoint of human color vision
which is actually pretty good,
versus say, birds, which are the most common predators
of insects, including beetles.
And so their perception of what that looks like
may be quite different than what our perception is.
There's also lots of other things that being shiny
might actually help you find mates.
Depending on the color patterns,
indicate that, you know, maybe you don't taste very good
so a bird would leave you alone.
And in some cases, it may actually be
about a non-visual thing altogether.
Something like thermal regulation is super important
in insects because they can't control their temperature.
They are impacted by the temperature around them.
So having an ability to reflect some of that UV back
so that you don't overheat, is probably a good thing.
So there's lots of speculated reasons,
but we still don't have definitive answers
as to for one particular species of beetle
why it's this way versus another species.
But it obviously serves them,
or it would have dropped out of the population.
- Now, what I think is the coolest thing about iridescence
is how completely distantly related animals
can sort of stumble on the same physics for making color.
This is a piece of abalone seashell that I keep on my desk.
It's made of layers and layers
of a different hard material called nacre.
Light is bending and reflecting and interfering
in almost the same way as in the beetle's shell,
using a totally different material.
And since the seashell stuff is basically rock,
the iridescence can even be seen
after these shells fossilized.
This is a fossilized ammonite,
and it's at least tens of millions of years old,
and it's still iridescent.
That is incredible.
But I've been saving my favorite kind
of iridescence for last.
The beetle that I'm about to show you,
I have to admit, I didn't believe it was real, but it is.
(curious music)
Come closer.
It's really small.
This is an actual earthling.
It's a type of beetle called a weevil,
and this particular one looks like it was dipped in glitter,
but this is also a form of iridescence.
But to understand how this kind of iridescence works,
we're gonna have to go to an unexpected place.
The rare minerals vault
at the Smithsonian in Washington D.C.
The rocks and crystals inside of this vault
are some of the rarest and most priceless minerals on earth.
To get in, we had to go through an armored door
with an actual laser palm scanner
like something out of a spy movie
which I was not allowed to film because of security reasons.
- So this is an opal from Australia
which is where a lot of the great opals come from.
This is actually a whale bone
from Australia that in fact has been opalized.
(Joe laughs)
- Every part of what you just said is ridiculous.
It's a whale bone from Australia that's-
- I know. - in the earth
that is not just a bone anymore,
but it's been turned into opal.
- Yeah, and basically the bone was there.
It gets saturated with water that has silicon in it.
That porous material that was the bone
got filled in with little spheres, opal, basically.
- That's probably the coolest fossil I've ever seen.
(Joe laughs) - Isn't that pretty?
I mean, it's one of the most beautiful, right?
- Yeah, that is incredible.
- It is.
- Every day I walk in here and I go,
"Something about the earth
just amazed me in a different way."
This is one of the most amazing opals
(Joe laughs) I've ever seen in my life.
- [Joe] This grew in the earth.
- [Jeffrey] This grew in the earth.
Have you ever seen an opal like that before?
- [Joe] No, it's, I mean, it's coming from
every direction. - [Jeffrey] It is.
- [Joe] And they're big chunks.
- You'd swear that somebody put a little battery
