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.

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.

In the third episode, the discovery of extraterrestrial life might face an impossible challenge: the physics of the universe itself; but using cutting-edge tech, experts might be on the verge of a groundbreaking find -- and the evidence could already be in hand.

Brian Cox looks at our attempts to answer one of the most profound questions we can ask – are we alone in the universe? With scientists sending space probes to the furthest reaches of our solar system and beyond, the scientific search for alien life has begun. Inspired by a childhood love of science fiction, Brian still hopes to hear from ET. In this film, he explains why this search deserves to be taken seriously, and he explores the chances of it happening.

An ancient piece of corroded metal is more than it seems: an alien-looking device of intricate dials and cogs; there are over 30 gears inside and some gears have up to 65 teeth on them. Using cutting-edge imaging technology, experts examine what could actually be a 2,000-year-old computer.
How can an ancient Roman cup change colour? It's not an optical illusion. It really does change colour from red to green.

The cosmos, with its billions of galaxies and countless stars, isn't the only one. We share our lives with another universe: The world of the small, of the viruses, of the bacteria. We call this strange hidden kingdom the Microcosmos. We share our world with the microcosmos. Will we coexist in an uneasy peace, or will it destroy us?
In 2020, A tiny virus caused a global pandemic, COVID-19. This pandemic makes people see the world completely differently, because there was an invisible universe, pretty much ignored for the most part. Very, very tiny things have a huge impact on our lives. The microcosmos is complex, while some parts kill us, others keep us alive. The microcosmos is responsible for the very oxygen that we breathe and the soil on which we live. And it will influence our future as we venture out into space.