24 Hours on Earth

The sun.

It creates the daily rhythm

for life on Earth.

A player in almost every drama

that unfolds across our planet.

Hour by hour,

its exact position is critical.

For some, it brings moments

of enormous opportunity.

For others, it can spell disaster.

All over the world,

animals' lives are governed

by the sun's journey

through the sky.

How they respond can make

the difference between success

and failure,

life or death.

This is just an ordinary day

on our extraordinary planet.

It's dawn.

The sun hasn't arrived yet,

but its power will soon be felt,

and the world is waking.

HOOTING:

The day starts with a love song.

HOOTING:

HOOTING:

Lar gibbons.

With each note, they renew their bond

after the long night,

and remind other gibbons that

this patch of forest is theirs.

They've discovered that the hour

before sunrise is the perfect time

for their duet...

HOOTING:

..because sound travels furthest

in cool air.

And at dawn, a warm layer

sits above the cool air,

reflecting and amplifying every note.

It's the best time of the day

to be heard,

and the gibbons aren't the only ones

making the most of it.

BIRD SQUAWKS:

BIRDS CALL:

All over the planet, nature's

dawn chorus heralds the moment

the world's been waiting for.

SCREECHING:

PENGUINS TRUMPE Our star,

a burning giant,

reappears above the horizon.

Its rays, travelling at over

180,000 miles per second...

..flick the switch

and the world is flooded with light.

This meerkat family is up early

to greet the sunrise.

THEY CHIRRUP:

It's not high enough

to warm them up just yet...

..and they're finding it

difficult to get going.

But unbeknown to them,

the early light

is having an extraordinary effect

inside their bodies.

Sunlight triggers the brain

to shut off drowsy hormones,

replacing them with

waves of energising ones,

kick-starting their metabolism

and preparing them for the day ahead.

Suddenly, they're wide awake.

Time to find breakfast.

All over the world, the rising sun

is making its presence felt,

forcing animals into action.

For the last eight months,

South Africa's rocky shoreline

has been a nursery

for this young Cape fur seal.

He, too, is hungry,

but the need to fuel his body

is about to get him into trouble.

Each morning, with the rising sun,

the current moving past the mouth

of the bay brings rich pickings.

But with opportunity comes danger.

A killer patrols these waters...

..waiting for inexperienced pups

to take the plunge.

The older seals know

the great whites are out there,

but by midday, the biggest

fish shoals will be out of range.

The seals must leave now.

The pups' best chance is to

fall in with a convoy of adults.

Experienced seals

are notoriously hard to catch.

But in the first two hours

of the day,

the great white has a better chance,

thanks to an ally.

The sun itself.

The early-morning light

is strong enough

to silhouette the pup from below.

But the slanting rays

can't penetrate the depths.

The shark can see the pup,

but the pup can't see the shark.

This time, the pup is just small

and speedy enough to slip through

the shark's jaws.

Away from the coastline, he's safe.

And as the sun rises higher,

illuminating the shadowy depths,

the shark's

window of opportunity closes.

At least, until tomorrow.

As the sun climbs higher in the sky,

its character is changing.

For the first time in the day,

it's not just sensed as light,

but as radiant heat.

BIRDS CHIRP:

Clusters of Monarch butterflies

huddle close together

against the chilly Mexican night.

Up until now, the morning has been

too cold to leave the branches.

But as the sun hits their wings,

warming their bodies to a crucial

12 degrees, they can finally fly.

Each cluster revealing

tens of thousands

of individual butterflies.

The first warmth of the day is

just as important to small mammals.

These Madagascan lemurs

aren't meditating.

They're sunbathing.

Too small to regulate

their body temperature well...

..they lie back

and soak up the warmth

through their thinly coated

underbellies.

A much-needed morning heat fix.

But nowhere is the warming of

the landscape felt more keenly

than in the desert...

..of Namibia.

Overnight, the temperature

hit freezing point.

But this morning, the sun

is radiating heat

directly onto the sand dunes.

Three hours after sunrise

and, already, the temperature

has climbed by 30 degrees.

Exactly what this desert inhabitant

has been waiting for.

The Namaqua is unusual...

which, for a chameleon,

is really saying something.

Somewhere in its evolution,

it drew the short straw.

So whilst its cousins around

the world live hidden in trees,

the Namaqua is exposed

on sand-blasted dunes.

Just surviving the freezing night

has left the cold-blooded

chameleon sluggish.

Its energy supplies so drained

that breakfast passes

right under its nose.

It's going to need to get warm

before it can eat.

By angling its dark brown, scaly skin

towards the light,

it becomes a reptilian solar panel.

An hour or two on charge

and it will be good to go.

In less extreme parts of Africa,

this change in air temperature has

burnt the hanging morning haze away.

In just a couple of hours,

the ground will become so hot

that it will begin to generate

a heat haze of its own.

But right now,

in this brief window of clarity,

with nothing to spoil her view,

conditions for this cheetah

are perfect.

She's a mother,

with responsibilities.

Three of them.

They're growing fast

and they're hungry.

Mum needs to make a kill.

The lions who share her territory

have excellent night vision.

But the cheetah's eye

is designed for sunlight.

Packed full of colour receptors,

she sees the world

in razor-sharp detail.

The lions could threaten her cubs,

but they're stuffed full

from the night's hunt.

Right now is her best chance.

Black tear stains under her eyes

combat glare and help her focus

in the crisp morning air.

Just in time.

The heat haze will soon be shimmering

above the ground...

..making it difficult

to see in any detail.

Then the time for hunting

will be over.

The best option?

To spend

the rest of the day

in the shade.

In more temperate parts of the world,

plants have been working hard

since dawn...

..photosynthesising light

into energy.

In the next hour,

the sun's intensity will peak.

These light harvesters

are gearing up for what should be

the most productive moment

of the day...

..but it's also when the sun

becomes its most dangerous.

As damaging to plant cells

as it is to our skin.

As the sun blasts down

from overhead...

..these sunflowers

are carefully monitoring

its intensity,

flooding each leaf with a sunscreen,

protecting the plant from sun damage.

At 90 degrees, directly overhead...

..the sun's rays pass through

the least atmosphere.

Millions of watts of energy

beat down onto the Earth.

In the Australian outback,

temperatures have soared past

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