DAVID ATTENBOROUGH: A Perfect Planet.
There is a nuclear reactor 93 million miles away.
We call it the Sun.
Its rays, travelling through space,
reach the Earth in just eight minutes...
..and give power to life throughout the planet.
Its daily and yearly rhythms
shape the existence of every creature on Earth...
..and has done so for over three billion years.
In the beginning...
..there was light.
Surprisingly, perhaps, almost every part of the Earth's surface
receives the same quantity of sunlight each year...
..4,380 hours of it.
But it's delivered in varying amounts
at different times of the year,
depending on where you are.
It's only here in the tropics, close to the equator,
that there are 12 hours of guaranteed daily sunlight
the year round.
And, here, that has created a great richness of life -
the tropical forest.
Each leaf is a natural solar panel which collects the sun's energy
and fuels a multitude of plants.
And, in Southeast Asia, gibbons live here.
WHOOPING
BIRD CALLS
A five-year-old female...
..and her lifelong partner are on a mission.
Every morning, they head out across their territory
to look for ripe fruit.
There is one kind of tree here that they need more than any other.
The fig tree.
These are the only plants in the entire forest that produce fruit
all year round.
Their flowers grow in dense clusters
inside undeveloped figs,
but these have not yet been pollinated
and are not yet edible.
The gibbons will have to wait.
To produce ripe fruit, the fig still needs two things...
..a large dose of sunlight
and some of the smallest creatures in the forest.
Tiny fig wasps.
They're only 2mm long.
The figs have a unique partnership with these insects.
A female wasp has the space of just a single day
when the fig will allow her to burrow into the undeveloped fruit.
It's such a tight squeeze that her wings are ripped off.
But she's not going to use them again.
Once inside, she makes her way to the tiny,
tightly packed internal flowers.
And, here within, she lays hundreds of eggs.
She then carefully unpacks fig pollen from her abdomen...
..and with it fertilises the tiny flowers.
When she's finished laying,
she dies...
..inside the unripe fig
alongside her eggs.
The sunlight now slowly ripens the figs
and helps the young wasps inside to develop.
After just five weeks, the eggs start to hatch.
The first to emerge are the golden, wingless males.
Things now become stranger than fiction.
These males start to mate with their unhatched sisters.
To reach them, they use a telescopic penis
that's twice their body length.
While their now-pregnant sisters are beginning to hatch,
the males themselves burrow their way to the outside world.
The brothers' final act is a chivalrous one.
They sacrifice themselves to marauding ants.
They're serving as decoys
so their sisters can take to the skies.
The young females, loaded with pollen, live for just 48 hours,
in which time they must find another fig tree at just the right stage
into which they themselves can burrow, as their mothers did.
With the sun's helping hand, the figs are now ready to eat.
The gibbons know all the fig trees in their territory.
And each day they travel up to two miles
to find one with fruit that's ready to eat.
Ripe figs at last...
..a major part of their diet and available the year round.
Thousands of animals rely on fig trees.
This abundance is only possible in a world without seasons
and constant daily sunlight.
But this 12-hour cycle of light and darkness
only happens close to the equator.
Elsewhere, the amount of sunlight fluctuates across the year.
That is because the Earth does not spin in an upright way.
Its axis is on a tilt.
23.5 degrees.
So as the Earth makes its annual orbit around the Sun,
keep your eye on the North Pole.
For the first half of the year, it's angled away from the Sun,
bringing darkness and winter to the northern hemisphere.
For the second part of the year,
the North Pole swings towards the Sun, bringing summer.
The Earth's tilt gives us the seasons.
And life has adapted
to deal with even the most extreme changes in light.
The High Arctic.
After six months of being angled towards the Sun,
it begins six months of freezing darkness.
This is Ellesmere Island,
the closest land to the North Pole.
It's winter, and for the last four, long months,
the only light here has come from the Moon.
Few creatures can survive this sustained darkness.
They have become specialists in living for months without sunlight.
WIND HOWLS
Muskox.
Remnants of the last Ice Age.
Having grazed all summer, they've built up fat reserves
that will enable them to survive the brutal cold of winter.
And this makes them a prime target for other sub-zero specialists.
GROWLING
Arctic wolves.
The Moon provides just enough light for them to see.
SHE SNIFFS
This alpha female leads the hunt.
Target in sight.
If her pack is to survive, they need to make a large kill
at least once every three weeks.
The alpha female signals the start of the attack.
They run at the muskox and the herd panics.
The muskox close ranks.
The wolves look for weakness.
MUSKOX ROARS
IT ROARS FIERCELY
WOLVES WHINE
Charging risks isolation from the crowd.
ROARING
And that is just what the wolf pack wants.
ROARING
The wolves can sense victory.
But the herd comes to the rescue.
And, once again, they close ranks.
Most winter hunts end in failure for the wolves.
MUSKOX ROARS, WOLVES WHINE
As the long polar nights drag on,
the hungry wolves turn to their only other source of food...
..arctic hares.
They've gathered together in their hundreds for safety.
Trying to catch one hare among hundreds
is harder than you might think.
Even if they do catch one, it's not much of a meal.
Sometimes you just have to admit defeat.
WOLF GROWLS
But life is about to get better for the wolves.
For the first time in six months, the sun rises above the horizon.
Its appearance marks the beginning of half a year of continuous light.
The sun's warmth will allow the muskox to give birth,
and that will provide easier hunting for the wolves.
It's early spring,
and much of North America is still locked in ice.
As our tilted planet orbits the Sun,
the northern hemisphere receives increasing sunlight...
..and wakens an animal with an almost supernatural ability.
It is frozen solid,
like a block of ice,
and has been all winter.
An ordinary-looking frog...
..but an extraordinary one.
A wood frog.
Its heart has stopped beating completely.
But, as the sun's power increases,
almost miraculously, it begins to change.
Its frozen blood is melting
and begins to flow through its veins...
..as its heart begins to beat again.
HEARTBEAT
The wood frog is cryogenic.
In just 12 hours,
it thaws and comes back to life, as if by magic.
This defrosting ability
means it's ready for the moment when, at last,
spring arrives.
All across the northern hemisphere,
the sun's warmth is bringing dramatic change.
As the sun rises higher and spring takes hold,
the warming air reaches the ground and the rocks beneath.
Here, thousands of animals begin to stir.
Garter snakes,
one of Canada's most northerly reptiles.
After six months of hibernation,
the males are the first to emerge.
They haven't eaten for months.
Even so, it's not food that is on their minds, it's something else...
..females.
But they stand no chance of doing anything about that
until they've charged their batteries.
Snakes are cold-blooded and they need to absorb the sun's heat
before they're able to move quickly.
After a few hours, the males are raring to go.
20,000 snakes,
the largest emergence of reptiles
anywhere on Earth.
Now a few females appear.
They're much bigger than the males...
..and warming will take them longer.
She releases a scent, a pheromone,
that attracts the males.
They outnumber her 100 to one.
To speed her own return to activity, she will absorb heat from them.
Intoxicated by her scent, the males compete for her,
wrapping themselves around her.
She now has hundreds of males on top of her,
making mating near impossible.
But she has a way of weeding out the men from the boys.
She'll make a daring ascent of the nearby cliff.
She barges her way through the crowd to get to the rock face.
As she climbs, only the strongest, fittest males can keep up with her.
She's made it to the top.
Only a few of her suitors have managed to rise to the occasion,
and she may reward them all.
This entire mating jamboree only lasts
for one short week in the year.
And when it's over, they all move off into the forest.
There, they disperse to lead solitary lives searching for food
until winter drives them back to the shelter of the rocks below ground.
It's June, halfway through the Earth's annual journey
around the sun, and summer has arrived in the northern hemisphere.
Karak Lake, in Canada, north of the Arctic Circle.
The summer will be brief,
but there is sunlight for 24 hours every day.
So the next few months are vital for every living thing here.
And this arctic fox knows it.
CUBS SQUEAK
Winter has been hard for her, and now with a new family to support,
she must make the most of the summer's abundance.
Her three-week-old pups have just emerged from the den.
CUBS SQUEAL
Each of these little bundles of fur
needs nearly 300 calories of food every day.
A tall order for Mum.
GEESE HONK
But a solution for her problem is just arriving.
Snow geese.
They have flown over a thousand miles from the United States,
timing their arrival to coincide with the end of the snow.
GEESE HONK
More than half a million will spend the summer here,
nesting and feeding on the grass.
There's fierce competition between couples
for the safest nesting sites.
The losers will have to nest on the outskirts of the colony...
..the first part to be raided by the foxes.
Mother is after eggs...
..but getting them is not going to be easy.
GEESE HONK
The geese will risk their lives to protect their eggs.
If they lose them, they can't produce another clutch this season.
The fox wins.
GEESE CALL
She gives the first eggs to her young pups...
..and then heads back for more.
GEESE HONK
Some of the eggs she stashes away.
They will be food to help her through the coming winter.
GOOSE HONKS
In just three weeks, she will steal over 800 eggs from the geese.
But eating a big egg is not easy
if one is rather small.
It's a technique the pups haven't quite yet cracked.
Mum shows how it's done.
GOSLING CHEEPS
Goslings are now hatching all across the colony.
And they will need all the food they can get
to build up their fat before their journey south.
Now that the chicks have hatched,
they can all find safety on the water.
CUBS SQUEAL
In these brief sunlit months, there's time for the cubs to play.
But there is no playtime for Mum.
But the Arctic is warming,
and the timing of the seasons and the migration of the geese
is becoming unpredictable.
Although the sun stays above the horizon continuously
throughout the Arctic summer,
its rays are comparatively feeble.
Closer to the equator, in our planet's deserts,
cloud cover is rare.
The sun here is not a friend...
..but an enemy.
WIND GUSTS
Africa.
The Sahara.
Few creatures can live here.
Get caught out in the open at the wrong time of day
and it's game over.
WIND GUSTS
By 10:00 in the morning, the temperature on the surface
of the sand is pushing 60 degrees Celsius.
Even the toughest will soon have to take cover.
But one creature is waiting underground
for the sun to get even hotter.
Temperatures are now so high
that everything else has to shelter.
The desert now belongs to the Earth's greatest solar specialist...
..the Saharan silver ant.
At midday, when the sun is at its fiercest,
they emerge to look for creatures killed by the scorching heat.
They're one of the fastest insects on Earth, and they need to be,
with just five minutes to find food before the heat kills them.
Getting lost would mean certain death,
so every few seconds they spin round,
taking a bearing from the sun.
When others are frying, these ants have solar tech
to stop them from overheating...
..special glassy hairs and shining bodies
that reflect the sun's lethal rays.
It buys them precious time.
To get their prize back as quickly as possible
to their underground den demands teamwork.
But shelter is a long way away.
Any technique will do.
The push and slide.
The spin.
Even dune surfing.
The nest is still 70 metres away.
Some are already collapsing in the heat.
Reinforcements are needed urgently.
Now the heat whips up violent gusts of hot desert air.
For an ant, these are hurricanes.
WIND HOWLS
They must get their prize underground as soon as possible,
and blown sand has blocked the entrance to their den.
Any longer out here and they will be toast.
One final effort.
The last of the team race home.
Shade, at last.
Much of the land on our planet could become as scorched
and lifeless as this if we allow our activities
to continue to change the atmosphere.
The Sahara alone has expanded by an area twice the size of France
in just the last hundred years...
WIND GUSTS
..part of a global desert invasion that threatens a third of all land.
The sun can certainly be a lethal threat,
but it could also be our saviour.
The solar energy that strikes our planet in just an hour
contains more power than that used by all of humanity
in an entire year.
By October, as the Earth completes its annual journey
around the sun, day lengths in the northern hemisphere
are shortening once again.
The sun's power is diminishing.
Trees are beginning to shut down their solar panels.
The green chlorophyll with which they collected the sun's energy
is broken down chemically and reabsorbed.
And the forests turn from emerald to gold.
It's autumn.
Once again, the living world away from the tropics is transformed.
Plants stop growing
and many animals begin to prepare for tough times ahead.
The forests of central China...
..home to the golden snub-nosed monkey.
They will not survive the fast-approaching winter
unless they stock up on calorie-rich food.
Top of their autumn menu - pine cones,
They grew during the summer sunlight and are rich in fats.
Few are now left,
and time to gather them is running out.
Dominant males patrol the troop,
making sure they get the pick of the crop.
MONKEYS SCREECH
As the number of pine cones dwindles,
tensions between rival families increase.
AGGRESSIVE SCREECHING
Mere threats between two males may not be enough to settle disputes.
MONKEYS SCREECH
Conflict is in the air.
There's going to be a fight.
MONKEY SCREECHES
Vital food is at stake,
so every pine cone is worth fighting for.
MONKEY SCREECHES
The victor and his family enjoy the spoils of war.
The losers get no more than a few dead leaves
and will have fewer energy reserves for the coming winter.
The sun's power dims.
Temperatures drop.
Everything slows down.
Ahead lies months of crippling cold.
MONKEY WHINES
Most of the life on Earth away from the tropics
has managed to adapt to the changing seasons,
but there are some creatures that have found a way
to avoid the cold of winter altogether.
Snares Island, New Zealand,
deep in the southern hemisphere.
CAWING
Here, sooty shearwaters have been nesting throughout the long summer
and gorging themselves on fish.
As a result, they've piled on quite a few pounds.
But the sun is now fading, and the southern winter is approaching.
No time to hang around.
SHEARWATERS CAW
When you're a touch tubby,
launching into the air...
..is a leap of faith.
They won't see land again for four weeks.
Setting off across the Pacific, they're starting on
one of the longest journeys made by any living thing.
Their aim - to avoid the consequences of the Earth's tilt
and follow the sun's warmth as it dwindles in the south
and increases in the north.
For those who survive the 10,000-mile marathon,
there will be a great prize.
The reward for travelling from one end of the planet to the other
is long summer days the year round.
This is their destination...
..Alaska's Aleutian Islands.
While the south of our planet is slipping into autumn...
..here, summer is just beginning.
Below the waves, vast clouds of plankton are blooming.
Triggered by the sunlight,
these tiny marine organisms
are food for crustaceans - krill.
This is the sun-fuelled bounty
for which the shearwaters have crossed the planet.
By cheating the tilt,
they're able to enjoy the riches of summer the year round.
But shearwaters are not the only ones to visit the warming seas.
WHALES CALL
Humpback whales.
They've been breeding in the tropics...
..and haven't fed for six months.
Up to 6,000 whales are now heading for these islands -
the only place where they can find food in the quantities they need.
The shearwaters begin to dive into a huge shoal of krill.
The humpbacks attack from below.
Each year, a million shearwaters join the whales
in these dramatic feeding frenzies.
It's one of the greatest gatherings of life on Earth.
And it only happens because some whales and some birds
have found a way to live in a summer that never ends.
Rolf Steinmann has wanted to be a wildlife cameraman
since he was a child, even if he has to remind himself from time to time.
I'm a lucky cameraman.
I'm a lucky cameraman...
To those who've worked with Rolf, his love of the wild is legendary.
You know, if he's not on location, he's at home watching
every other wildlife documentary that's ever been made.
I think Rolf is motivated by the beauty in the world.
I think he really has this pure heart.
Rolf alone with nature is Rolf at his best.
Rolf is a man obsessed.
The opportunity to be the first to film arctic wolves
in the polar night is Rolf's dream of a lifetime.
We have a lot of luggage. This is a major expedition.
And there's one piece of luggage that is very,
very special to me, and it's...
It's actually this book by Jim Brandenburg.
It's 30 years old, it's from the '80s.
And when I saw this book the first time,
it really triggered a dream to become a wildlife cameraman.
And this was the shot.
It's unmatched to this day.
When I saw it, I just wanted to experience it myself.
To go to Ellesmere now and to film wolves is...
..is my biggest dream coming true.
If I'm honest, I'm not just excited about the shoot,
I'm also a little bit anxious.
I haven't worked in -50 degrees,
and actually trying to find wolves in darkness, in the polar night,
is something that has not even been tried by anyone.
Ellesmere Island lies just 500 miles from the North Pole.
In the winter, the sun doesn't rise for four months.
The temperature regularly drops to -50 degrees...
..making it one of the coldest places on Earth.
It's such an unreal place.
It's like a...like a frozen dream.
There's so much space.
It's really like a different planet.
The wolves here can range for thousands of miles
across the frozen landscape.
If you look at that landscape,
how vast it is,
you can imagine how hard it is to find the wolves,
a white animal in a white landscape.
One wolf has a radio collar,
but this kind of telemetry only gives a rough direction to explore.
The fjord is just to the south, so I think the best plan
is cut across on the ice and see if we can find a way up.
The team race towards the wolf's last broadcast position
and get lucky.
They find the whole pack,
and something never seen before.
This is so incredible. HE LAUGHS
A herd of hundreds of arctic hares
are under attack from Rolf's white wolves.
HE CHUCKLES Wow.
We found our...
..our pack of seven wolves,
in their full beauty, which is amazing.
Filming the new behaviour ramps up the pressure on Rolf.
Oh, God, the situation is just right in the wrong spot.
Rolf is well known for his self-criticism.
He's a perfectionist.
You know, he wants that image to be absolutely perfect.
You're amazing, but I'm stupid, unfortunately.
A day later, the wolves disappear out of range of the telemetry.
It said they were here, but now they aren't here
and we don't get any signal from the telemetry.
So, now I think we realise how hard it will be to find the wolves
if we don't just run into them.
With no wolves to film, Rolf is determined
to capture the beauty of the landscape with a drone.
We just can't get the thing in the air.
Um, the motors, they've physically frozen solid.
And the drone's not the only thing that's freezing.
Look what I just found under my mask.
ROLF LAUGHS
THEY LAUGH
A plan to warm up the drone with a hairdryer and a duffel bag
could mean that the world record for the coldest flight is still on.
Success!
But the cold soon takes its toll on Jesse, the drone operator.
Argh! I'm sorry, I can't feel my hands.
I think we have to drift to the right a little bit more.
When you're on a shoot with Rolf, he'll just keep going
and going and going.
We can fly towards the big mountain.
I can get the... Argh! ..the big mountain, you know...
Yeah. ..like, more centred.
Argh! My hands!
Come on, it's coming, it's coming. You just fly straight, Jesse.
But I'm losing my sensation in my hands, Rolf.
Yeah, let's hit roll on it before we die... Let's record.
Come on, do it.
This feels like a totally different planet. It's really crazy.
OK, and I think now we could do a forward view. Yeah.
Argh! Perfect, Jesse. You can go a bit slower.
If you can, go a bit slower. My fingers are hurting.
Argh!
That looks really cool!
It's incredible.
With no sighting of the wolves in weeks,
the team decide to follow their prey instead.
Muskoxen.
And the tactic pays off.
The herd is being shadowed by the wolves.
MUSKOX GRUNT
They are very close to a herd of muskoxen there,
and something might happen.
Rolf is in the perfect spot to capture the first arctic wolf hunt
ever filmed in the polar night.
WOLVES WHINE
God, there was some good stuff, I think, if I got it in focus.
With the shots in the can, there is a magical experience for Rolf...
..one he's dreamed of since he was a child.
It doesn't get better than this.
WOLVES WHINE
Oh, my God. This is an absolutely...
..dream of a lifetime.
Honestly, you are the most beautiful living being I've ever seen.
Incredible.
Next time...
..weather.
This powerful force carries vital freshwater around the globe.
And all life on land is perfectly in tune with its annual rhythms.
The Open University has produced a free poster
exploring our perfect planet.
To order, please call 0300 303 0901.
Or go to bbc.co.uk/perfectplanet
and follow the links to the Open University.