All language subtitles for our.universe.s01e02.1080p.web.h264-bigdoc

It's
morning in the forest.

And for this troop
of chimpanzees,

it's time to get out of bed

and get on with the day.

But when you sleep in
a nest 40 meters up in the air,

it can be a bit of a challenge.

This morning ritual has
been playing out like clockwork

for countless generations.

A rhythm driven by one of the most
mysterious properties of our universe.

Time.

And time is playing an
extra important role

for one female chimp.

Celeste is in her mid-30s,

and she has a ticking
clock inside her.

A clock that was set
13.8 billion years ago.

From The Big Bang came atoms…

…and energy…

…which have journeyed across
vast reaches of space.

And these ingredients

are now assembling…

to create a new life.

In Celeste's womb, a tiny
chimpanzee is forming.

It will be another 150 days
before this baby meets the world.

That's the time it takes.

And without time,

nothing in our universe
would ever be born.

From the youngest chimpanzee…

to the oldest black hole.

But how did time start
in the first place?

Does everything experience
time in the same way?

And will our universe's
clock ever stop ticking?

The day begins for a
chimp much as it does for us.

Breakfast.

A critical meal… when
you're eating for two.

Celeste is already
an experienced mom.

Her firstborn, Apollo, is the
dominant male of the troop.

And he can be a bit slow to
get going in the morning.

Each chimp is a different age.

Each has a distinct personality.

But all of them are
creatures of routine.

Their lives governed
by the passage of time.

We can't see it.

Or hear it.

We can't influence it in any way.

And yet, every heartbeat,
every choice and action,

every inaction is a consequence
of time's continuous flow.

It can whiz by or drag on.

But time ticks ever onward.

Stars and planets
form, age, and die.

In their wake, new stars emerge.

And from a rare few,

the most mysterious objects
in the universe are born.

Black holes.

Time is the cosmic conductor.

Nothing can escape its grasp.

Although we have devices that
can track and measure time…

…chimps don't.

Celeste and her family use
the sun as their guide.

Rising and arcing
across the sky.

As it moves…

so do they.

Chimps rarely sleep in
the same nest twice.

Each morning, they head off
in search of fresh fruit.

Journeying from one part of
their territory to another.

But right now, the ripest fruit…

is on the other side
of an open plain.

Apollo and the strongest
members of the troop go ahead

to make sure it's
safe for the others.

Out in the open,

they're vulnerable to
predators, rival chimps,

and the heat of the rising sun.

They need to be quick.

Time is ticking.

The sun traveling across the sky

forms the chimps'
basic unit of time.

From sunrise to sunset
and back to sunrise.

The 24-hour day.

But a day is not actually
a measure of time at all.

It's a measure of motion.

As our planet
rotates on its axis,

the forest moves through space
at 1,600 kilometers per hour.

It takes 24 hours for
Earth to do one full turn.

Giving the chimps 24
hours of movement,

12 in sunshine and
12 in darkness.

Again and again.

It's our planet's steady spin
that sets Earth's master clock.

And is the chimps'
trusted timekeeper.

But this essential cycle
we take for granted…

is not universal.

As soon as you leave
our home planet…

…the 24-hour day
no longer applies.

Flying closest to the sun…

…is the planet Mercury.

Compared to us, it
rotates at a snail's pace.

Our neighbor Venus
spins even slower.

It takes longer to
rotate on its axis

than it does to orbit the sun.

Making Venus's day
longer than its year.

Each planet has its
own unique day length.

Including planets far
beyond our solar system.

Sixty-three light years away,

orbiting a young star,

is Beta Pictoris b.

It spins so fast…

…it bulges out at the sides.

It is the fastest-spinning
world we know of.

Here, a day lasts
just eight hours.

Every planet in our universe
spins at its own speed.

Billions of worlds,

each with their own clock,

ticking away to
different rhythms.

But all moving forward on a
universal cosmic timeline.

Back on Earth,

with the sun now almost
directly overhead,

the chimps know exactly
what time it is.

It's lunchtime.

And their crossing of the savanna
has been timed to perfection.

They've hit the jackpot.

These sweet berries of
the African grape tree

are only around for a few weeks.

A rare seasonal gift
from the forest.

Where the middle of the day
is a very productive time.

Animals of all sizes are
tending to their daily tasks.

And each experiences
time differently.

For small creatures that
live fast, short lives…

…lunchtime can feel
like a lifetime.

For slower, longer
living things,

an hour can go by in
the blink of an eye.

But whether you're
living in high speed

or in slow motion,

all life in the forest must
adhere to the same 24-hour day.

And as the world keeps spinning…

…those days keep ticking by…

dictating the lives
of every chimpanzee.

One in particular.

At just 15 weeks,

this baby's entire body could
fit in its mother's hand.

For it to fully form,

a cascade of perfectly
timed events must occur.

For the next 130 days,

every minute, every
nanosecond is critical.

New cells divide and grow with
remarkable speed and precision.

Right now,

brain cells are multiplying at a
rate of around 15 million per hour.

All of us, from our
very first moments,

have a deep biological
relationship with time.

As the sunlight wanes,

the chimps instinctively
switch gears.

To evening mode.

Nesting calls signal
to the whole troop.

It's time to find a safe
place to spend the night.

Their bedding needs
to be soft but strong.

It doesn't hurt if it
tastes good either.

The rhythm of every
day in the forest

is determined by the
sun's position in the sky.

But the chimp's
innate sense of time

comes from something
inside them.

Deep in their brains
is a biological clock.

Bundles of neurons
act as a pendulum…

…controlled by genes
that switch on and off…

and a cycle that
repeats every 24 hours.

These clock genes create a
circadian rhythm in the body

that waxes and wanes in sync
with our planet's rotation.

Controlling hormones…

…heart rates,

and energy levels.

And right now, the chimps' body
clocks are sending the message,

"It's time to get sleepy."

Not everyone can though.

Celeste's baby's brain
is still forming.

With no internal
clock of its own,

it relies on its mother's
hormones to keep it synchronized.

But baby doesn't
always get the memo.

Lucky for Celeste,

with so much growing to do,

her baby does
eventually drift off.

While the chimps go to
sleep high in the treetops…

other forest dwellers
are just waking up.

Body clocks tick away

in the cells of plants and
animals throughout the forest.

Clock genes evolved two and
a half billion years ago

in the first living cells.

Those that could anticipate the light
and dark of a day had an advantage.

And as life evolved,

it synchronized
to Earth's motion.

So that today,

these clocks exist in almost
every creature on Earth.

Although some creatures
prefer day and others night…

all life is dancing
to the same beat.

Thanks to cellular clocks

that tick in time with
the spin of our Earth.

As yesterday becomes a memory…

…another new day
begins in the forest.

A fresh cycle,

and yet, no clock can
ever truly be reset.

And there are subtle clues all
around the forest that reveal why.

Nothing is the same today
as it was yesterday.

Least of all Apollo,

who seems to have woken up
on the wrong side of the bed.

When he's in a bad mood…

the rest of the group just
need to keep their heads down.

He soon finds a target
for his rage, though.

Some of the younger chimps
have found honey for breakfast.

And they forgot to invite
Apollo to join them.

You soon learn, never get on the
wrong side of the dominant male.

He's got a nasty bite.

Thankfully, it's
not too serious.

With a bit of care,
this wound should heal.

But wounds leave behind scars,

etched into the chimps' bodies.

Indelible marks of the past that reveal
the one universal truth about time.

It has a direction.

You can never go back in time…

…only forward into the future.

This is time's arrow,

and it leaves
scars on everything

across Earth…

…and beyond.

Our moon is pockmarked with battle scars
that tell stories of ancient events.

So too are the planets.

Their surfaces testament to a lifetime
of bombardment by asteroids and comets.

But perhaps the most impressive
impact crater in our solar system

belongs to a moon of Saturn.

Mimas.

The Herschel crater is
130 kilometers across.

Whatever created
this enormous scar…

must have come close to
shattering the moon to pieces.

Mimas lives to tell the tale.

But events like this
are irreversible.

And they differentiate
the past from the present.

Impact craters are timestamps

that mark a unique
moment in history.

We can never revisit the
moment they were created.

But we can piece together
traces of past events

and map a course
back through time.

Before craters.

Before planets.

Before stars.

Back to a time before time.

Our universe had a beginning.

A very big bang…

that created
three-dimensional space

and time.

But space and time
are not separate.

Time is woven into the
fabric of the universe.

Bound to space as our
universe's fourth dimension.

The Big Bang set the
universe's clock ticking.

Propelling everything
into the future.

It created the arrow of time.

From our universe's
very first moments…

…it pushes us all
into the future,

causing everything to grow,

age…

…and change.

From childhood…

…to adulthood,

we all travel through life
in the same direction.

Getting older day by day.

And with age comes wisdom

as youthful innocence is
replaced by experience.

Time's arrow leads us
through these stages of life.

It shapes us.

Defines who we are.

From our first moments…

to our last.

Chimps rarely live
past the age of 40.

Nothing is immortal.

Everything that exists in our
universe has a finite lifespan.

Including, perhaps,
the universe itself.

Today, the galaxies
are filled with stars.

But 95% of stars that will ever
exist have already been born.

So, as our universe
journeys into the future…

…the stars…

…one by one, will blink out…

…leaving the universe to face
an ever-darkening future,

stretching out for trillions,

that's thousands of
billions, of years.

The age of starlight

will be followed by a
dark age of black holes.

These monsters feed on the
remnants of dead stars and planets.

And as they do,

their ever-increasing gravity scars
the very fabric of the universe.

Distorting both space and time.

The edge of a black hole,
called the event horizon,

is a region where gravity
has become so strong

it causes time to slow down
practically to a standstill.

But even black holes
can't escape time's arrow.

In the far, far future…

…when there are no stars
or planets left to consume,

they will begin to starve.

And slowly…

very slowly,

they will shrink.

When they die,

no one truly knows
what comes next.

But it could be the
end of our universe.

Here on Earth, none of us
can slow the passage of time.

And one of Celeste's aunts is
reaching the end of her time.

Retreating from the group, she
heads into the forest alone.

She has lived many years.

But this day will be her last.

While the world
continues to spin,

her body lies still.

But time doesn't just
carry us toward endings.

It also creates beginnings.

As days turn into weeks
and weeks into months,

there are big changes for
one special chimpanzee.

Say hello to Cosmo.

Her brain and limbs
are now fully formed.

And her eyes are ready
to see the world.

The exact timing of her
birth is impossible to know.

But she could be
born any day now.

She's been in the
womb for eight months.

But her journey
began long, long ago.

The elements that made
her came from dying stars.

The water that flows through her
body came from distant worlds.

The energy that powers her muscles
came from the heart of our sun.

But it's that most
mysterious ingredient,

the one that started ticking
13.8 billion years ago…

that has led all other
ingredients to this moment.

In this place.

On this planet.

Another sunrise,
another morning.

And this one is extra special.

Welcome to Earth, Cosmo.

This precious moment will
never be repeated for Celeste.

But Cosmo's journey
has just begun.

It will take around three months

for her body clock to synchronize
to the rhythm of the planet,

one year before she
can truly communicate,

and perhaps 15 years
until she is fully grown.

So much lies ahead.

Like Cosmo,

our universe is
still in its infancy

at the beginning of an
unimaginably long lifespan.

We are living in the
age of starlight.

A moment when time's arrow has
filled the universe with beauty…

…and wonder.

But it's a brief window of time

that will never be repeated in
the history of our universe.

No one can slow the
passage of time,

nor should we try.

Because without time,

there would be no now.

No moment in the sun.

No moments, period.

Without time,

there would be no life.

Next in the story
of our universe,

Earth's seasons.

Like a mother bear
raising her cubs…

…we all experience our planet's
yearly transformations.

But what created
Earth's seasons?

How are they connected to
the formation of our moon?

And why does only our planet have
conditions just right for life?