Are rising temperatures driving Earth's ecosystems past a point of no return? We have promising technologies that put solutions within our grasp. Scientists are exploring solutions: from geoengineering to sucking carbon out of the air to cloud brightening, as means to cool the planet. Cutting-edge solutions and high-risk measures. But would they work? And what are the risks of engineering Earth's climate?

Peter Jackson's poignant WWI documentary 'They Shall Not Grow Old' to commemorate the centennial of the end of the first World War. The acclaimed documentary is an extraordinary look at the soldiers and events of the Great War, using film footage captured at the time, now presented as the world has never seen. By utilizing state-of-the-art restoration, colorization and 3D technologies, and pulling from 600 hours of BBC archival interviews, Jackson puts forth an intensely gripping, immersive and authentic experience through the eyes and voices of the British soldiers who lived it. Jackson recorded a special introduction to the film offering his perspective on why the film is important for audiences, who have never experienced WWI footage as anything but grainy black & white, and silent. Jackson opens a window to the past in a way that has never been seen or heard before, noting, 'Restoration is a humanizing process.'

What sort of alien civilizations might exist in the vastness of space? Terra is the fictional world imagined in Episode 4, a planet nine billion years old, twice as old as Earth. Old enough that a truly advanced intelligence could evolve. It was once a fertile world, now it is barren. But life can still thrive here in artificial domes. Over time, they've evolved not to need their bodies. They exist only as neural tissue. They never age, they never die. They're monitored and maintained by robots.
If alien civilizations are statistically so likely, why haven't astronomers found any sign of them? Where is everyone? Every time we look at an individual star, that's like dropping a bucket in the ocean. We're going to have to look at a lot of stars and to search through a lot of data until we find the clue that leads us to another civilization.

Planets beyond our solar system are known to astronomers as exoplanets. They are at trillions of miles from Earth and yet, it might be possible to detect a faint signature of life in them. From the light of the stars they orbit that passes through the atmosphere of an exoplanet, it is possible to capture the chemical fingerprint of the elements in that atmosphere.
The fictional world Eden is orbiting not one star, but two. The light from its twin stars powers photosynthesis, pumping more oxygen into the atmosphere than in Earth, allowing life to thrive. Grazers are constantly alert to danger, because the canopy is home to predators perfectly evolved to live among the trees. In Episode 3, another topic are fungi and the role they could play on exoplanets. Ecologist Thomas Crowther talks about the role mycelial networks play in the Rothiemurchus forest in Scotland.

Most planets we know of are so hellish, it seems impossible that anything could live. But it's amazing where life can take hold in the Earth. Astrobiologists look for simple single-celled microbes known as extremophiles in places as Danakil Depression, known in Ethiopia as 'The Gateway to Hell.'
In Episode 2, the fictional world is Janus, a planet in such a close orbit than its rotation is locked by the star's gravity and it always shows the same face to its sun. On one side of the planet, it's always daytime, a searing desert. On the other side, it's forever night, a frozen shadowland. Squeezed between the two, a sliver of perpetual twilight. Freezing meltwater flows from the cold side, carving canyons through the landscape. Deep in these canyons lives an extraordinary five-legged creature.

The series, depicted by state of the art CGI techniques, and applying the laws of life on Earth to the rest of the galaxy, blends fact with science fiction and conceptualizes what alien life might be like on other planets.
In the prologue, astronomer Didier Queloz makes an appearance to discuss the discoveries of exoplanets and how they are analyzed in the real world. In Episode 1, the fictional world imagined is Atlas, a world with higher gravity than Earth and a thicker atmosphere leading to airborne creatures. In explaining the aliens of Atlas, the episode also explores the handicap principle in insects, and shows a rehabilitative form of falconry as captive falcons are trained to live in the wild.