- Thank you to Brilliant for supporting PBS.
I need to talk to you about a bird.
- Our biggest wow factor is probably
this crimson topaz here and so-
- 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.
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.
This is a phenomenon called iridescence.
We find iridescence in loads of places.
even in that dirty puddle out in the parking lot.
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.
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.
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.
- Gives you a flash at the camera.
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
because pretty might indicate best genes,
best ability to care for offspring and so-
- You don't have a lot parasites crawling all over you,
There's like purple and green and everything.
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
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 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,
and are added together to make the reflected color
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
depending on the direction that you are looking at it.
Not bad for some little dinosaurs.
Okay, so hummingbirds are cool,
but they aren't the iridescent royalty
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
and beetles themselves seem to have
a particular fondness for iridescence.
Not every beetle is iridescent,
they have some of the most unbelievable colors in nature.
I mean, honestly, if you didn't know
you'd be forgiven for thinking that they were painted
by an artist or a YouTuber trying to trick you.
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.
like a greenish reddish rainbow,
but this one here, you hold it to light,
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.
"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.
the really bright metallic greens
or living places with lush green forests
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.
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,
But I've been saving my favorite kind
The beetle that I'm about to show you,
I have to admit, I didn't believe it was real, but it is.
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.
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.
from Australia that in fact has been opalized.
- Every part of what you just said is ridiculous.
It's a whale bone from Australia that's-
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.
- Every day I walk in here and I go,
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
This is also an Ethiopian opal.
- [Joe] This doesn't look real.
opals are made up with these little spheres of silica.
These are spheres of silica, silica and oxygen.
They're probably formed out of a silica rich solution.
These little spheres of silica are, you know,
are stacked together very perfectly.
I mean, it's kinda like, you know,
we always stack oranges in a grocery store, right?
- when the light hits those, they go hurrah,
and you get these great flashes
of color that we love in opals.
somebody went in- - Nature is-
and was placing these- - Well.
- Basically these little spaces in here,
these are about the right separation size
to cause refraction to take place.
And you get the flashes of color.
- Sure. - Well, light comes in
but what happens is light gets reflected
off of different layers. - Mhm.
- [Jeffrey] And then in some places, as the light combines,
it combines constructively and other places destructively.
- So some colors are taken out,
some are accentuated. - Some, some, that's right.
Light coming in at different angles,
different colors come off at different angles.
- As you're getting different parts of it,
- The orientation hits your eye.
I mean, those flashes are just unreal, aren't they?
- Yeah.
- The ordered structures that cause iridescence
in opals are called photonic crystals,
a kind of crystal where the bending
and reflecting of light is happening
in three dimensions in a periodic or repeated pattern.
Photonic crystals are also what make these weevils
look like they were dipped in glitter.
They are nano-sized, three-dimensional, repeating structures
Some of them are built like honeycombs
with orderly spaced pockets of air.
Others are sort of the opposite of that
with stacks of evenly spaced spheres with air in between.
And just like in an opal, light is bent,
waves combine constructively or destructively,
and different flashes of color appear.
All of these iridescent colors are the result
of physical structures that bend light,
or any of the other ways that color is created in nature.
Just the strange and beautiful result
of light waves interfering with each other.
What I love most about these things,
It's that we can look at rocks and shells
and bubbles and birds and even beetles,
and despite how different they all are,
they're all tied together by this colorful bit of physics.
Kind of makes the universe feel a bit less
I think we should call ourselves The Beatles.
you made it to the end screen.
By the way, if you haven't hit that subscribe button,
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Also, wanna say a huge thank you
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for not only helping us amass this great beetle collection
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If you'd like to join that esteemed club,
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