- In an endless and dark expanse floats a peaceful blue oasis. That is our vision of the Earth. And yet, our planet is far more complex. Air, earth and water are the planet's driving forces. (THUNDER RUMBLES) These forces shape the many cycles that have created the planet's amazing natural diversity... in the oceans, on the continents and in the atmosphere. Air is invisible, yet it is one of the foundations of our natural world. Our atmosphere subjects us to brutal weather, yet also protects us ` every one of us ` birds, insects and even mammals. The air hums with life. Without air, Earth would be... unearthly. Captions by Julie Taylor. Captions were made with the support of NZ On Air. www.able.co.nz Copyright Able 2021 Earth's atmosphere is a dynamic world of its own, constantly changing. Perhaps its most visible features are the clouds. But our skies are by no means empty. Indeed, they teem with life. Birds are particularly well adapted,... (BIRDS TWEET) ...especially the sooty tern. This sea bird spends up to 10 years of its life in the air,... eating, drinking and sleeping. This bird does them all while in flight. During its travels, the sooty tern covers tens of thousands of kilometres. However, the terns to have to make land in order to breed. They congregate in flocks of several thousand to lay their eggs, incubate them and rear their chicks. Naturally, this draws attention. Tern breeding colonies entice larger predatory frigate birds. The tern parents do everything they can to protect their offspring,... with limited success. (EERIE, UNSETTLING MUSIC) During the breeding season, this drama happens a lot. (BIRDS SQUAWK) (EERIE, UNSETTLING MUSIC CONTINUES) (SQUAWKING INTENSIFIES) Sometimes, the frigate birds fight over their prey in the air. A moment's distraction, and the chick breaks free and falls back to the earth. If this young bird's luck holds, it will soon take flight among thousands of other terns. Then it will embark on its own life high above the oceans, just one of the winged wonders of the skies. Earth's atmosphere consists of layers. The lowest is the troposphere, which reaches altitudes of around 8km above the poles and approximately 18km along the equator. This layer is both a habitat and the primary source of the Earth's weather. The troposphere contains approximately 90% of our planet's air mass and almost all of the atmosphere's water vapour and aerosols, giving us clouds. Scientists go to great lengths ` or rather, heights ` to study them. (WONDROUS MUSIC) A flying laboratory. Researchers use the high-tech airship to weigh clouds and discover how much water they contain. The lab is well equipped. A laser traces the shape and takes the cloud's measurements. Another piece of equipment lets scientists record the size and density of the drops of water that make up the cloud. The pilot and scientists confer one final time, then the experiments begin. The airship dives into the clouds. The instruments evaluate the first drops of water. Humidity here is 100%. The researchers even have time to enjoy the fresh air. Once the airborne laboratory has left the clouds, the scientists evaluate the data. The cloud they examined was relatively small, with a volume of 20 million cubic metres. - 20 million. - 20 million...? - Cubic metres. - They calculate the cloud's weight using its volume and the size and density of the individual drops of water. - So that small cloud weighed 4 tons. - Yeah. - That's incredible. - It is. - Despite their heft, clouds float on thermal updrafts until the drops of water become too heavy. Then it starts to rain. Clouds, wind and weather play an essential role in nature. Their impact is particularly apparent in high mountains, especially in winter. Life in the alps can get challenging once snow blankets the landscape. In the freezing air, the wind cuts like knives. - (CALLS) - (BLEATS) - A young, inexperienced golden eagle has difficulty finding somewhere to land in the featureless expanse. A crash landing in the soft snow might appear harmless,... but can prove fatal for the eagle. The danger increases every time the bird of prey sinks into the snow. The fresh snow is damp, and the air is freezing. - (CALLS) (CALLS) - More snow collects in the eagle's feathers with each failed attempt to land. The first lumps of ice have begun to form on the exhausted bird. Instinctively, the eagle reacts to the danger. It makes its way into a tree. It would probably not survive a night on the cold, icy ground. The weather turns and a storm gathers. The young eagle has no choice but to wait it out. Unlike the eagle, mountain hare use the deep snow to their advantage. Protected from the wind, they wait for storms to pass, even if it takes days. The same is true of ptarmigans. Golden eagles can usually withstand temperatures down to minus-30 degrees Celsius, thanks to their layers of downy feathers. Unfortunately, the ice in its outer feathers and the harsh weather conditions prove extremely challenging for the young bird. The animals begin to emerge. The golden eagle has survived the night in the tree and attempts to take flight. The warmth of the sun soon allows the bird to shake the ice out of its feathers. It may take a while, but this young eagle should eventually become the ruler of this mountainous kingdom. Across the Earth, the weather determines life and death. From space, the atmosphere can appear calm and peaceful. But a closer look reveals nature's full force. (THUNDER RUMBLES) Sometimes, the air itself spins out of control. Dust devils, water spouts and tornados are all forms of whirlwinds. America's Midwest is notorious for its tornados. Every year, whirlwinds leave trails of destruction, costing lives and causing millions of dollars in damage. (TENSE MUSIC) Scientists attempt to discover all they can about the destructive weather phenomena. Using radar, they can only measure wind speeds 50m above the Earth's surface. The goal is to understand the wind speed at ground level. But it's impossible to predict the course of a tornado, even if it were possible. The powerful whirlwinds would probably destroy the instruments. Is there perhaps some way to tame a tornado? Unfortunately not, but scientists in Ontario, Canada, have found a way to simulate the dynamics of a tornado in the lab. The walls contain 48 fans that push air into the chamber, where it begins to rotate. Additional fans in the ceiling draw the air upwards. The rotation plus the updraught create a man-made tornado. Researchers designed an experiment to try to measure the speed of a tornado at ground level. - I'm gonna start the fans. (FANS WHIRR) - The foam tiles are light enough to be picked up by the whirlwind and large enough to measure their progress. - We'll go a little bit up with the updraught at 35%. - The tiles spin through the air. The suction increases. - Just go up to 40. - A computer uses a camera to track the individual tiles to determine an average speed. Success. The miniature tornado rotates at 35km/h at ground level. Of course, a natural tornado is far larger and more powerful. But the experiment could help scientists measure whirlwinds in the real world. It may be possible to feed similar markers into a tornado, then determine their speed of rotation. This unique wind tunnel has already caused quite some turbulence within the scientific community. Another laboratory making discoveries about the weather floats high above the Earth. The International Space Station can spot powerful storms on the Earth's surface, even from 400km away. Nature's fireworks never stop. 100 flashes of lightning every second. The lightning is caused by a build-up of electrostatic charges within clouds. The electrified air discharges with an intense flash of light and more. (THUNDER RUMBLES, LIGHTNING CRACKS) The energy release by the lightning heats the surrounding air abruptly, causing it, for all intents and purposes, to explode. That's thunder. The thunderclap fades, but it demonstrates that without air, there would be no sound. (GIBBON HOOTS) - (HOOTS) - (YAWNS) - (SCREECHES) - (SQUEAKS) - (GROWLS) - (CAWS) - (SHRIEKS) - (GRUNTS) - (CALLS) - Without sound, animals would be unable to communicate acoustically. For example, when they see a predator. (ANIMALS CALL) Warning cries ring out. - (BARKS) (BARKS) - And the animals flee to safety. - (CALLS) - Sounds play important roles in the wilderness. Some calls announce the search for a mate, while others declare territories and harems. - (CLICKS) - (GRUNTS) (HOLLOW RATTLING) - Without plaintive cries for food, young ones may be over looked. Sound waves can ensure survival. Some animals, however, remain as quiet as possible. (DRAMATIC MUSIC) In the evolutionary arms race, some predators have learned the power of surprise. Silence is one of the greatest weapons in an airborne hunter's arsenal. Owls are masters of the quiet, deadly attack. A comparison between owls and pigeons reveals just how quiet an owl's flight is. Turbulence caused by the wings create sound. When a pigeon flies over a layer of feathers, it's visible. The feathers barely move when an owl passes above them. Unlike the pigeon, the owl causes very little air turbulence. Its feathers have adapted to enable extremely silent flight. Some animals are even quieter than owls. In fact, they are inaudible ` at least to human ears. Ultrasound allows bats to navigate in the darkness. The creatures emit calls at a very high frequency. These sound waves reflect off objects. These echoes reveal the presence of obstacles as well as insects to eat. Different bats use different signals. The Egyptian fruit bat emits only two ultrasonic cries close together. This is apparently enough to stop the bat bouncing off cave walls. Dean Waters of the University of Leeds hopes to discover whether these short clicks are enough to reveal smaller obstacles in total darkness. (BAT SQUEAKS REPEATEDLY) His equipment makes the ultrasonic waves audible to humans. Waters intends to eavesdrop on the fruit bat echolocation. (LOW CLICKING) The scientist places hooks in the roof of the cave, then attaches a series of thin ropes with bells at the end. They'll ring if a fruit bat brushes against the cord. In the cave's complete darkness, infrared cameras reveal truly fascinating behaviour. The fruit bats have a wingspan of more than half a metre, but the ropes have been placed just 40cm apart. The bats must draw their wings in to avoid the obstacles. - He's brought his wings up. He knows the strings are there. He's dropped through the strings, and then he's away on the other side, carrying on flying. - The fruit bats not only avoid the ropes; they actually navigate through them. - People have always thought this type of echolocation was very primitive. But these strings show that these bats are able to detect something which is very small. So it's a very sophisticated system; much better than we previously thought. - From the ultrasound of the bats to the other side of the scale. - Elephants are extremely social animals. (ELEPHANTS GROWL) They use many different methods of communication. - (GROWLS SOFTLY) - (GRUNTS) - (SQUEALS) - Physical contact, a clearly defined sign language and certain sounds allow the grey giants to communicate with each other. Sometimes, they have a lot to discuss. - (GRUNTS) (ZEBRA BRAYS) (BRAYING CONTINUES) - (GROWLS) - However, elephants also make use of another means of communication. Infrasound. The animals emit very deep sounds that, like the ultrasound of the bat, are inaudible to the human ear. Elephants create these sounds by expelling air from their lungs through their very long vocal cords. Elephants can hear these sounds over several kilometres. They use the infrasound calls to find other elephants or to warn them. (LOW GROWLING) Elephants form complex, highly evolved societies. From the smallest calf to the herd's matriarch, communication is essential. As the sun sets, the elephants have a last little chat at a watering hole. But air doesn't just carry soundwaves. It also carries chemical substances. There is something in the air. (BEE BUZZES) Scents provide important information about the wider world. The rainforests of Brazil are an olfactory feast, and some animals here are particularly attuned to the aromas of the jungle. South American coatis have an extremely well-developed sense of smell. The coati family explores its surroundings, hoping to sniff out something to eat. They are related to racoons and share their innate curiosity. The younger animals in particular will stick their noses anywhere. (UPBEAT MUSIC) The playful coatis explore their habitat. (UPBEAT MUSIC CONTINUES) The young animals still have a lot to learn ` for example, what might be food... and what most certainly isn't. (LOW, OMINOUS MUSIC) In situations like this, having older, experienced female relatives nearby really helps. When the monitor lizard leaves, the coast is clear. The family continues its quest for food, particularly insects and small animals. The coatis would do well to avoid the Brazilian wandering spider. The spider, the most venomous arachnid in the world, is usually nocturnal, but the coatis have awoken it. Instinctively, the nosy coatis stay cautious. From a distance, the spider seems less threatening. One of the older animals beats a hasty retreat. The young coatis have learnt another important lesson. Some dangers are not immediately apparent. The sun, for example, would appear to be a positive force, yet it could immediately erase all life on Earth if it weren't for the stratosphere. This layer of the atmosphere reaches an altitude of approximately 50km and contains the ozone layer. Sunlight consists of all the colours of the visible spectrum. In nature, it shows up in rainbows. The palette ranges from red to violet. However, sunlight also includes invisible rays. The ultraviolet wavelength has a higher frequency than violet rays. And UV radiation is extremely harmful to organisms. The ozone layer absorbs much of the UV radiation, protecting life on Earth. Sunlight also provides warmth, of course. Reptiles depend on it. Warming their bodies allows them to move quickly, which is sometimes necessary. This small lizard is too slow. A paradise tree snake discovers the tasty morsel... and prepares to pounce. Time to go. Even in a dense jungle, moving from treetop to treetop isn't an option. Some creatures find themselves trapped. But not this one. (DRAMATIC MUSIC) The gliding lizard sails to safety. Or maybe not. In these forests, the snakes can fly too. This time, the gliding lizard escapes. Plants also need air to reproduce, for one thing. Some depend on it to spread their seeds. Some float to earth,... while others spin wildly. Some hitch a ride on the wind, which increases their chance of finding a place to take root. In the rainforest, animals and plants wage constant battles for resources like air, nutrients and water. When a seed germinates, the plant reaches toward the sun. As it grows, the plant absorbs carbon dioxide from the atmosphere and produces oxygen. Sometimes, the tiny seeds give birth to giants. But some trees don't spread their seeds with the wind; instead, they enlist the help of aerial assistants. With wingspans of over a metre, they can cover great distances. They are among the largest flying mammals in the world. Every morning, the nocturnal animals congregate in the highest treetops to rest. The bats hang upside down among the branches. Their resemblance to another ground-based animal has given them their common name ` flying foxes. Flying foxes spend much of the day just hanging out, occasionally fanning themselves with their wings when it gets too hot. Females give birth once a year, and young flying foxes depend on their mothers for several months. Every new life contributes to the future of the forests, as the flying foxes are the caretakers of the trees. Every night, they embark on a quest for food, mostly fruit. And in the process, replant some of Sri Lanka's rainforests. The jungles have shrunk considerably from human encroachment. The flying foxes act as a form of courier between the last remaining patches of forest. They eat the fruit and swallow the seeds. Excreting the seeds helps spread them far and wide. Scientists believe that flying foxes play an integral part in natural reforestation. Earth's rainforests are subject to an eternal daily cycle. In the morning, mists rise from the jungles. More than 400 billion trees grow in the Amazon, and each releases up to 1000 litres of water a day into the atmosphere. During the day, an estimated 20 billion tons of water collect in the skies above the Amazon. Huge clouds form. The moisture that rose into the atmosphere as mist returns to Earth as water later in the day. No wonder they're called rainforests. The large amounts of water have created a unique ecosystem. It's natural recycling. More than half of the water that makes up this downpour was released by the trees themselves in the morning. The Amazon rainforest is one of the richest habitats in the world. This incredible diversity is the result of water and another less likely ingredient. (INTRIGUING PERCUSSIVE MUSIC) (WIND HOWLS) Namibia in South West Africa is one of the world's driest regions. Years may pass without rain, and yet life endures here. Giraffes have learned to survive in the harsh conditions. Drought and wind fill the air with sand and dust making it difficult to breathe and obscuring the landscape. Incredibly, sand and dust helps life to thrive. Winds propel these particles into the air in Northern Africa's Sahara Desert, carrying them 5000km across the Atlantic. 28 million tons of Sahara dust descend on the Amazon basin every year. This dust, rich in nutrients, fertilises the rainforest plants. When clouds begin to form, rain is never far off. Scientists use radar to make weather predictions. This Doppler effect radar in Texas can detect drops of water in clouds and make them visible. Experts have also used the equipment to discover flocks of birds and trace migration routes. Every year, ruby-throated hummingbirds congregate along Texas' Gulf Coast, their last stop on the way to their winter quarters in the south. Aided by the locals, the tiny birds eat their fill before embarking on their long journey. Once the hummingbirds are out of range of the radar, it becomes impossible to track them. Their exact destination remains a mystery. Researchers use a range of techniques to explore the role of the natural habitat above the Earth's surface, including sending up balloons with nets. They collect insects that move across the skies above the planet. Scientific instruments record altitude and temperature as well as the direction and speed of the wind. The apparatus collects samples day and night. It seems almost impossible to fully understand the animal world above our heads with just a few nets. And yet, the research has provided some astonishing results. Every day, billions of insects inhabit the skies high above us. Among them, the painted lady butterfly. The balloon experiment revealed they migrate further than any other insect. In spring, they travel from tropical Africa to the Arctic Circle. In autumn, following generations travel south again. Their journey takes them almost 15,000km. An impressive feat for the dainty butterfly. Other animals prefer to leap rather than fly. Some creatures perform athletic aerial manoeuvres; others seem to almost plummet. In the jungles of the Indonesian island of Sulawesi, a nocturnal predator lurks in the darkness. Tarsiers have large, extremely sensitive eyes... and excellent hearing. These powerful sensors allow the little creatures to detect prey in the dark. The smallest movement causes tarsiers to leap into action. Moving rapidly from tree to tree, the tarsier devours its hapless prey. The darkness and the speed of the surprise attack ensure that the animal does not go hungry. However, the tarsier is not alone. A colugo hangs in the branches just a few trees away. These gliding mammals live in the treetops of rainforests. Like flying snakes and gliding lizards, colugos try to avoid climbing. The animal glides from tree to tree at night. The membrane of skin stretches from the shoulder to the tip of the tail, like a cape, and the spaces between the colugo's fingers and toes are webbed. The mammal faces an arduous journey back into the treetops. But once it's there, it's in its element. Gliding saves both time and energy, which can be better used for finding food. They hang motionless against the tree trunk, their mottled fur providing camouflage. The colugo is ready for a day of rest. Reaching higher into the sky, beyond the realm of animals, the atmosphere's third layer is far from empty. The mesosphere lies approximately 50km to 85km above the Earth's surface. This layer is the realm of shooting stars. Space is peppered with meteoroids, remnants of the beginnings of our solar system. Sometimes, they come dangerously close to Earth. When a meteoroid descends towards the Earth, friction causes the rock to glow in the thin air of the mesosphere. Most burn up harmlessly. But not all of them do. (FAST-PACED PERCUSSIVE MUSIC) 15th of February 2013. A gigantic ball of fire appears suddenly in the skies above the Russian city of Chelyabinsk. The friction and the air pressure caused the Chelyabinsk meteor, with a diameter of 20m, to explode at around 30km above the Earth. The explosion damages thousands of buildings. And for the first time in recorded history, humans are hurt by a meteor. Approximately 1500 people are injured; most of them cut by shards of glass shattered by the explosion. Never before has a lump of space rock had such a dramatic effect on modern civilisation. In fact, the meteor did not even crash into the Earth, unlike many others over thousands of years. Our planet is covered in dramatic scars. Satellite footage reveals the traces of meteorite impacts across the planet. (THUD!) Around 50,000 years ago, a meteorite 50m across plunged into what is now Arizona. The energy released was almost 700 times of the bomb dropped on Hiroshima. The point of impact, known as meteor crater, spans more than 1km across. Imagine if it happened today. Which is why scientists keep a close eye on space. The Pan-STARRS telescope detects meteors and other bodies that may threaten Earth. It is located on the peak of Mt Haleakala, on the Hawaiian island of Maui. Astronomers have identified 20,000 near-Earth objects. They consider 2000 of them potential threats. Pan-STARRS and other telescopes are a first line of defence against space projectiles. Researchers keep their eyes on the orbits of these objects. They don't expect a major impact in the foreseeable future. However, the question isn't whether a meteorite or asteroid will collide with Earth, but rather when. Compared to the size of our planet, our atmosphere is merely a thin layer. Space officially begins just 100km above the Earth. That also marks the beginning of the thermosphere, which reaches up to approximately 500km above the planet. This layer is responsible for breath-taking auroras ` the northern or southern lights. The International Space Station orbits the Earth 400km above the surface, offering a truly spectacular view of the auroras. The sun causes the lights by emitting a constant stream of charge particles known as the solar wind. This wind consists largely of protons and electrons. The solar wind presses against the Earth's magnetic field, denting it. The charged particles enter the atmosphere above the polar regions. Here, they collide with air particles. Oxygen emits a reddish light at an altitude of around 200km. Below this, green light appears. Science at its most breath-taking. (INTRIGUING MUSIC) Auroras are perhaps the most beautiful phenomena created by Earth's atmosphere. (INTRIGUING MUSIC CONTINUES) The air itself appears to flicker and burn. This fire in the sky is a glowing example of our planet's fascinating natural world. And it all happens in the air. Captions by Julie Taylor. Captions were made with the support of NZ On Air. www.able.co.nz Copyright Able 2021