All language subtitles for 829698E76C2BC7216E6F69FE990FA552_eng

On Australia's Great Barrier Reef…

…something magical has happened.

After 50 days beneath the sand,

chemical elements
from across the cosmos have created life.

Combining to form the next generation

of green sea turtles.

The eggs have now exhausted their supply
of life-giving elements.

And today, the baby turtles
will take their first taste of air.

And as her brothers and sisters
scramble to make it to the water…

a little female…

is last to be born.

In order to grow to adulthood,

she will need to harvest chemical elements
from across the ocean.

It's a dangerous journey…

…with treachery at every turn.

But for the baby turtles,

the call of the ocean is irresistible.

From a nest of 100,

sometimes only one will survive.

Sometimes none.

But despite the risk,

the little female knows

she must make it to the water.

She spots an opening…

and takes her chance.

Today…

she's a lucky one.

The hatchling won't stop swimming
until she has left the reef far behind.

Safely past the predators
that gather in the shallow coastal waters,

she'll disappear into the great void
of the open ocean…

to spend her childhood feeding on atoms.

Atoms whose origins go back through
the entire life of the cosmos.

To the time our universe

was in its infancy.

Expanding from nothing
to everything in an instant.

Our universe was born in The Big Bang.

At first,

it was nothing but a hot, dense fog.

But as it continued to expand…

the fog began to cool.

And on the tiniest scale imaginable…

…something astounding began to occur.

The first atoms condensed out of the fog.

Atoms of hydrogen.

The very first element in the universe.

And in the ocean,

juvenile turtles are hunting it down.

As they emerge from the blue

to forage in the shallow waters
of the reef.

This is Stella.

One of the lucky ones
that made it off the beach

and into the ocean.

She's already more than 2,000 times
her hatching weight

and growing fast.

Feeding on creatures she's found drifting
in the open ocean,

she's harvested one element
more than any other.

Hydrogen.

It makes up more than half
of all the atoms in the food she eats.

And is the most abundant element
in all living things.

From fish

to invertebrates.

Anemones and coral.

Hydrogen atoms formed
at the dawn of the universe

have been passed on from star to planet,

planet to animal…

and from prey to predator.

Which means, for Stella,

the waters around the reef
are full of danger.

Tiger sharks, hungry for the same atoms,

hunt sea turtles
throughout their adult lives.

Stella's main defense is her trusty armor.

Its bone toughened
with calcium and phosphorus.

Elements that date back
to another pivotal moment…

in the life of our universe.

For the first 300 million years
after The Big Bang…

there are no planets and no stars.

The dark ages of the universe.

Concealed in the gloom,

vast tendrils
of hydrogen gas crisscross the cosmos.

And then, incredibly,

as they were drawn together by gravity…

…the first stars were born.

This is the cosmic dawn.

The moment the lights came on.

And deep within those first stars…

a remarkable process began.

Temperatures and pressures
were so extreme…

…that new elements were created.

Atoms of hydrogen
were forced together to make helium.

As they fused, energy was released.

Creating a chain reaction that produced
increasingly heavier elements.

Including those essential for life.

Three helium atoms combined
to make carbon.

The element on which all life is based.

Carbon and helium made oxygen.

The air we breathe.

Oxygen atoms combined to make phosphorus.

Then silicon and calcium.

The elements
that make up every living thing

were created in the hearts
of the very first stars.

For Stella,

some elements are so important…

…she'll travel great distances
to find them.

The warm, shallow waters
between Australia and Papua New Guinea

are a paradise of vibrant seagrass.

The prairies of the ocean.

Stella has traveled all the way here
to access their magic ingredients.

As it grows,

seagrass absorbs elements from outer space

that have found their way
to the ocean floor.

Burgeoning fronds
rich in calcium and phosphorus

provide Stella
with precisely the minerals she needs

to build and sustain her protective shell.

Hardening her armor for the trials ahead.

Stella will spend her adolescent years

searching the ocean

for atoms born in the stars.

Her journey toward maturity…

paralleled in the story of our universe.

Because three billion years
after The Big Bang…

…the universe was also coming of age.

It was entering an incredibly active phase
of star formation.

As they grew,

stars were pulled together
into vast galaxies.

Like our Milky Way.

And within those galaxies,

the chemical elements each star produced…

…were transformed into planets and moons.

After billions of years,

chemical elements have matured
into the Earth we know today.

Stella is now fully grown herself.

Over a meter long,

she has a thick shell
covered in green algae.

Ideal camouflage for cruising coral reefs.

She is now at one with the ocean.

Atoms from the stars

perfectly adapted to life at sea.

Just one example of life on Earth…

exquisitely shaped from the cosmos.

Stella is now ready
for the next stage of her life.

Because she's about
to become a mother herself.

Inside her body…

she's carrying a clutch of 100 eggs.

The first of many
she'll have over her lifetime.

Her own precious cargo of stardust.

All across the reef,

atoms are being assembled into new life.

Creating one of the richest ecosystems
on Earth.

But our planet…

…is an outlier.

In the rest of the solar system,

the very same elements

have created worlds
far less suited to life.

Closest to the sun,

Mercury is a planet rich in carbon.

But rather than creating life,

the carbon is baked into its crust.

On a world scorched by starlight.

While in the farthest reaches
of the solar system,

Neptune's freezing temperatures

cause carbon and hydrogen
to form clouds of methane.

The suffocating gas
that gives it its brilliant blue.

And even on Mars,

a planet with all the same ingredients
as Earth…

the lack of an oxygen-rich atmosphere

means complex life couldn't survive here.

Only on Earth are conditions just right.

But even here,

competition for elements is fierce.

And danger…

…is never far away.

Luckily, Stella has become
an expert at hide-and-seek.

Safe for now…

Stella faces the biggest challenge
of her life.

To return to the Great Barrier Reef

and the island of her birth…

to lay her own eggs in the sand.

But a lifetime spent wandering the ocean

means she's now 2,000 kilometers away.

How Stella navigates home

is one of the wonders
of the natural world.

Deep within the Earth,

our planet's core generates
a magnetic field…

which gives every place on its surface
a unique magnetic signature.

When she hatched,

her island's signature
was imprinted in Stella's brain.

And to find her way back,

she'll rely on
yet another chemical element.

One that connects her
to the planet's core.

An element that's only created
when stars die.

In a nearby part of the galaxy,

two and a half million years ago,

a dramatic change took place
in the core of a giant star.

For all its life,
it had been powered by nuclear fusion.

The energy released…

…creating heavier and heavier elements.

Until the core became so hot,

it started creating…

…iron.

Which caused a fundamental change
to take place.

Because making iron
doesn't release energy.

It consumes it.

As more and more
of the metal was produced,

it spread through the core like a disease.

Feeding off the star's heat.

Throttling it.

With no heat source to hold it up.

From this moment onward…

…the star was doomed.

The resulting explosion shone
with the brightness of 10 billion suns.

A supernova which propelled
iron-rich dust across the galaxy.

All the way to our planet.

And even now,

100 tons of stardust enters
Earth's atmosphere every day.

Some left over
from the formation of the solar system.

Some blown here from distant supernovas.

A direct link
between our planet and the stars.

And it's the iron in this dust

that allows Stella to find her way.

Because deep in her brain…

…specialized cells are thought
to contain crystals of magnetite.

An iron-rich mineral that aligns itself
to the Earth's magnetic field.

A compass,

pointing her in the right direction.

Allowing Stella to find
the unique magnetic fingerprint of home.

And so an element forged in a supernova…

…will now guide her across kilometers
of featureless ocean.

Back to the island…

on which she was born.

But there are other creatures
with magnetic homing abilities.

The tiger sharks have it too.

And it's leading them back
to the same island.

Because for a few months every year,

thousands of female turtles come here
to lay their eggs.

It's the largest gathering
of green sea turtles

anywhere on the planet.

And as they come to shore,

the feeding begins.

Stella must wait for the right moment…

to find an opening…

and avoid the onslaught.

When the danger has passed…

she finally swims ashore.

After an epic journey…

Stella emerges onto the sand

she last touched as a hatchling.

The elements she spent
a lifetime collecting…

are now safely delivered into the sand.

Stella's mission is complete,

and she returns to the ocean…

to begin gathering stardust once more.

The cycle of her life

mirroring the grandest cycle of all.

The lives and deaths of the stars.

Because far away across the galaxy,

the ashes of countless supernovas

have come together to form a giant nebula.

A cloud of stardust
tens of light-years across.

And buried within it are places
where the next generation of stars

are beginning to form.

Called proplyds.

They're like vast cosmic eggs.

Each one bigger than our solar system.

Inside their shells of ionized gas,

the force of gravity
is pulling stardust together.

And the stardust inside Stella's eggs…

is also beginning to take shape.

As the elements she collected
are being transformed…

into something that's starting
to resemble a tiny creature.

And within the proplyd…

gases like hydrogen and helium…

…are feeding an embryonic star.

And what was once an embryo…

is now a tiny turtle…

with shell, flippers, and beak.

Elements reimagined…

for a life at sea.

In the proplyd,

the new star's development
is also nearing completion.

Reborn from the ashes
of the previous generation,

its light now reveals a family
of growing planets in orbit.

New worlds.

But perhaps, new possibilities for life.

And beneath the sand,

the same stardust,

passed down through countless generations
of stars and turtles…

will start yet another journey.

Each new life

directly connected
to the origin of the universe.

Each new story beginning
at the end of the last.

And so,
the story of our universe continues…

…with Earth's most precious resource…

…water.

And a family of elephants
on a dangerous mission to find it.

Their journey every bit as extraordinary…

…as water's journey across the vastness
of space to our planet.

But why is Earth the only world
in the solar system

whose surface
is covered with liquid water?

And why is it so essential for life?