1. A vast ocean of air

The skies above us are teeming with scientific mysteries which we're only just beginning to understand.

We may think that we inhabit the surface of our planet but in reality we live at the bottom of a vast ocean of air that's dynamic, fragile and home to some of nature's most powerful forces. But how can life survive in such a hostile environment?

To answer this a team of international experts spent a month studying the skies and carrying out groundbreaking experiments from a giant floating airship while flying across America. This unique science platform was called Cloud Lab.

2. Exploring the troposphere

The troposphere is a turbulent layer of air that begins at the Earth's surface and ranges from 23,000-65,000 feet above sea level, depending on the latitude, season and the time of day. Its name originates from the Greek word tropos, meaning change.

To collect samples at extreme altitude, extreme measures are required. Former paratrooper Andy Torbet jumped from 26,000ft with an oxygen mask and a collection dish to gather samples from the upper layer of the troposphere or free troposphere.

It's now known that bacteria actually exists in clouds and scientists believe that it plays a significant part in the creation of rain but little is known about life higher up. Microbiologist Dr Chris Van Tulleken has discovered that living bacteria can exist well above 10,000ft in a hostile environment with low pressure, increased UV radiation, freezing temperatures, high winds and no oxygen or water.

3. Living in the death zone

The human body has the ability to adapt to altitude, something often utilised by athletes who use it to improve performance but above 26,000 feet no human body can acclimatise.

Human beings must flood their lungs with pure oxygen to work at extreme altitude, to avoid dissolved gases such as nitrogen forming bubbles in the blood leading to the bends. How microscopic life survives at such heights has been a mystery. One answer could lie in the form of tardigrades or water bears that can completely dry out and live in a state of almost suspended animation.

Exploiting the boundary layer

While much is known about insects living close to Earth's surface, research suggests that other species exist on a vast scale higher up into the boundary layer. In a 1km square patch of countryside surveyed over the course of a summer month, as many as three billion insects pass overhead.

Insects at altitude

In the daytime smaller insects such as the leaf beetle are swept up into the atmosphere by turbulent air and carried on the winds. As the sun goes down, fast moving streams of air are created which larger insects use to assist their migration, selecting the most favourable altitudes and air streams to travel in.

Nocturnal moths

Noctuid moths such as the fall armyworm moth actively seek out these night-time air streams to carry them north and south across America following their migratory routes.

Flying spiders

You don't need wings to fly. Some young species of spider travel long distances by casting strands of silk into fast moving air columns. These act like parachutes and sometimes take them into the upper atmosphere, depositing them on remote islands and distant mountains.

The Himalayan jumping spider lives as high as 22,000ft above sea level. Its only source of food at these extreme heights is stray insects blown up by the wind.

4. Scaling the heights

Infographic showing heights and peaks, from the world's tallest building to commercial flights, ranging from sea level to the stratosphere.

Infographic showing heights and peaks, from the world's tallest building to commercial flights, ranging from sea level to the stratosphere.

5. Life above the clouds

Experts have not yet determined the upper limit for life on Earth but new research is finding a range of species living in the planet's upper atmosphere.

Adventurer Andy Torbet skydives from 26,000 feet in or order to collect bacteria samples.

Adventurer Andy Torbet from Operation Cloud Lab skydiving from a plane at 26,000ft to try and collect high altitude bacteria samples.

BBC/Percy Urgena

Biotechnology: a scientist with lab gloves on - Getty Images

More than 57 million tons of bacteria and fungi find their way into the atmosphere each year. Back on earth a dye is added to the samples collected. Cells reflect back microscope light showing up as glimmers of green.

Spiderlings on a web and a leaf by Getty Images.

Spiderlings are denser than air but can travel long distances by casting out strands of silk into fast-moving air columns that lift them up into the upper atmosphere.

Getty Images

A tardigrade or water bear under extreme magnification. Image by Getty Images.

Tardigrades or water bears can completely dry out and live in a state of almost suspended animation. Scientists believe they could hold the answer as to how bacteria can survive at high altitudes by regenerating damaged DNA.

Getty Images

Science Photo Library

Flying monarch butterflies. Image by Getty Images/ Werner Van Steen.

Familiar insects are often found at incredible heights above us including butterflies at 3,000ft and wasps, beetles and ladybirds at 5,000ft. Monarch butterflies have been spotted by pilots at 10,000ft.

Getty Images

6. How high can you go?

Many species have adapted their physiology over millions of years in order to live higher up, but which do you think can survive at the highest altitude?

Monarch butterflies

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Monarch butterflies

Some butterflies and moths exploit air currents during their migration particularly at night. Monarch butterflies have been seen by pilots flying at 10,000ft.

Indigenous people

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Indigenous people

People generally suffer from altitude sickness from 8,000ft upwards but locals in Tibet, Ethiopia and South America can live comfortably at 13,000ft.

Tibetan yaks

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Tibetan yaks

Yaks are the highest dwelling animals in the world, living up to 16,000ft in the mountains of Tibet thanks to their remarkable physiological adaptations.

Bar-headed geese

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Bar-headed geese

These geese migrate over the Himalayas regularly reaching heights of 21,000ft. Some have even been seen flying over the summit of Mount Everest at 29,029ft.