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This is the Microraptor,

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a carnivorous four-winged dinosaur
that was almost two feet long,

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ate fish,

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and lived about 120 million years ago.

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Most of what we know about it
comes from fossils that look like this.

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So, is its coloration here 
just an artist's best guess?

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The answer is no.

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We know this shimmering 
black color is accurate

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because paleontologists have analyzed
clues contained within the fossil.

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But making sense of the evidence
requires careful examination of the fossil

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and a good understanding of the physics
of light and color.

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First of all, here's what we actually see
on the fossil:

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imprints of bones and feathers that have
left telltale mineral deposits.

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And from those imprints,

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we can determine that these 
Microraptor feathers

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were similar to modern dinosaur,
as in bird, feathers.

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But what gives birds their signature
diverse colorations?

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Most feathers contain just one
or two dye-like pigments.

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The cardinal's bright red
comes from carotenoids,

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the same pigments 
that make carrots orange,

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while the black of its face
is from melanin,

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the pigment that colors our hair and skin.

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But in bird feathers,
melanin isn't simply a dye.

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It forms hollow nanostructures
called melanosomes

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which can shine in all the colors
of the rainbow.

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To understand how that works,

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it helps to remember 
some things about light.

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Light is basically a tiny electromagnetic
wave traveling through space.

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The top of a wave is called its crest

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and the distance between two crests
is called the wavelength.

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The crests in red light are about
700 billionths of a meter apart

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and the wavelength of purple light
is even shorter,

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about 400 billionths of a meter,
or 400 nanometers.

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When light hits the thin front surface
of a bird's hollow melanosome,

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some is reflected and some passes through.

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A portion of the transmitted light
then reflects off the back surface.

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The two reflected waves interact.

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Usually they cancel each other out,

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but when the wavelength
of the reflected light

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matches the distance between
the two reflections,

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they reinforce each other.

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Green light has a wavelength
of about 500 nanometers,

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so melanosomes that are 
about 500 nanometers across

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give off green light,

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thinner melanosomes give off purple light,

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and thicker ones give off red light.

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Of course, it's more complex than this.

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The melanosomes are packed together
inside cells, and other factors,

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like how the melanosomes are arranged 
within the feather, also matter.

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Let's return to the Microraptor fossil.

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When scientists examined its feather 
imprints under a powerful microscope,

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they found nanostructures 
that look like melanosomes.

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X-ray analysis of the melanosomes
further supported that theory.

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They contained minerals that would
result from the decay of melanin.

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The scientists then chose 20 feathers
from one fossil

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and found that 
the melanosomes in all 20 looked alike,

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so they became pretty sure this dinosaur
was one solid color.

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They compared these Microraptor
melanosomes to those of modern birds

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and found a close similarity,
though not a perfect match,

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to the iridescent teal feathers
found on duck wings.

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And by examining the exact size
and arrangement of the melanosomes,

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scientists determined that the feathers
were iridescent black.

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Now that we can determine
a fossilized feather's color,

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paleontologists are looking for more
fossils with well-preserved melanosomes.

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They've found that a lot of dinosaurs,
including Velociraptor,

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probably had feathers,

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meaning that certain films might not be
so biologically accurate.

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Clever girls.