There is no greater test for life than winter, as temperatures plummet to 70 below and winds reach 200kph. Darkness and ice extend across the polar regions and only a few remarkable survivors gamble on remaining. We join a female polar bear trekking into the Arctic mountains to give birth as the first blizzards arrive. Out on the frozen ocean, the entire world's population of spectacled eider ducks brave the winter in a giant ice hole kept open by ferocious currents. Arctic forests transform into a wonderland of frost and snow - the scene of a desperate and bloody battle between wolf and bison, but also where a remarkable alliance between raven and wolverine is made. Beneath the snow lies a magical world of winter survivors. Here tiny voles dodge the clutches of the great grey owl, but cannot escape the ultimate under-show predator - the least weasel. Midwinter and a male polar bear wanders alone across the dark, empty icescape. Below the snow, polar bear cubs begin life in an icy den while fantastical auroras light the night skies above. In Antarctica, we join male emperor penguins in their darkest hour, battling to protect precious eggs from fierce polar storms. Weddell seals escape to a hidden world of jewel-coloured corals and alien-looking creatures but frozen devastation follows as sinister ice stalactites reach down with deadly effect.

Be prepared to fight your way past all kinds of computer animation. Somehow Patrick Moore's The Sky at Night manages to convey just as much excitement with little more than a couple of diagrams and the presenter's hyperactive enthusiasm. The series cover the history of the solar system and humanity's age-old desire to learn its secrets. Far beyond the inner planets of rock and iron lie the gas giants. Discover the most distant and alien worlds in our Solar System and the moment of genius that allowed scientists to explore them.

Where is everyone? We have been listening for messages from outer space for more than half a century, and so far... silence, why? Are we truly alone in the universe? Or is everyone else acting like us and just doing a lot of listening? Maybe we need to be louder. Maybe we need to send more messages out there. But how do you write a letter to an extraterrestrial whose language and culture and biology and mind we have no concept of? And what do you say?
Given all of the unknowns about what they might behave, should we say anything at all?

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.

NASA's brand-new Mars rover is on the hunt for alien life, and with the help of cutting-edge engineering, scientists embark on a search for fossilized remains, which might prove the Red Planet was once home to a vast ocean and extraterrestrial life. Perseverance carries seven scientific instruments to study the Martian surface at Jezero crater. It carries several cameras and two microphones. The rover is accompanied by the helicopter Ingenuity, which will help Perseverance to scout for locations to study.

To our medieval forebears the world could appear mysterious, even enchanted. Sightings of green men, dog heads and alien beings were commonplace. The world itself was a book written by God. But as the Middle Ages grew to a close, it became a place to be mastered, even exploited.