A variety of cosmic events have both helpful and harmful effects on life on Earth. From the beauty of the Aurora Borealis and rainbows to the dangers of UV radiation and cosmic rays, from the miracle of photosynthesis to the thrill of a meteor shower, this episode explores how the effects generated by the sun and other extra-solar sources can literally get under our skin, scramble our technology, make life possible and threaten our existence all at the same time

This episode focuses on the Jurassic period, a time when the first giant killers stalked the Earth and lurked in the seas; a time when the slightest advantage meant the difference between life and death. In North America the iconic allosaurus, an ambush hunter with a lethal bite, dominated. Not even the heavily-armoured stegosaurus was safe from this killer, and incredible evidence reveals a glimpse of a vicious battle between these two giants. Life in Jurassic oceans was no easier; in 2008, a fossil was dug out of a frozen island high in the Arctic. It was a colossal marine reptile, twice as big as most ocean predators, at 15 metres long and weighing about 45 tonnes. This was Predator X. Its skull alone was nearly twice the size of a tyrannosaurus rex's, and its bite force unmatched by anything in the Jurassic seas. The balance of power between predator and prey is a fine one, as prey continually evolves different ways to avoid predators. But for the most successful and enduring predators, the battle to survive has always been tipped in their favour

This episode of the documentary series focuses on the new giants, the heavyweights of the dinosaur world. It is only in recent years that experts have unearthed the biggest dinosaurs that ever lived. One monster eclipsed all others; more than seven times as heavy as diplodocus was the immense argentinosaurus - a single backbone was bigger than a human. For years, these giants were considered immune to attack from any predator - until the discovery of mapusaurus, a new giant killer whose fate appeared to be inextricably linked to argentinosaurus

Humans are so clever they’ve built their own habitat, designed to keep wild nature out. Yet as we discover the urban environment is totally dependant on the natural world. Over the three years of filming for Human Planet, the teams have spent time with over seventy different communities in countries across the planet. Despite seeing many different ways of living, there are some aspects of family life that remain the same whether you live in a tree house in West Papua, or a brick house in Bolton. These similarities became very clear when the urban team went to film on a rubbish dump in Kenya. Here on the Kibarani dump on the outskirts of Mombasa, Ali, Ashe and their family live and survive amongst the rubbish, and even here, just like anywhere on the planet, everything stops for a nice cup of tea!

Here, Aleks charts how the Web is forging a new brand of politics, both in democracies and authoritarian regimes. With contributions from Al Gore, Martha Lane Fox, Stephen Fry and Bill Gates, Aleks explores how interactive, unmediated sites like Twitter and YouTube have encouraged direct action and politicised young people in unprecedented numbers. Yet, at the same time, the Web's openness enables hardline states to spy and censor, and extremists to threaten with networks of hate and crippling cyber attacks.

In episode two, Professor Brian Cox is off to India, where he assesses arguably the first evidence of rational thought in literature, the poetry of the Vedic monks. They pondered mankind's origins, realising there must have been a day with no yesterday - a day of creation - prompting the age-old question of where did the universe come from? Brian marvels that the universe seems to follow a set of rules, the laws of physics, allowing space to be considered on the grandest scale, travelling to the most distant, farthest reaches of the cosmos just by using our minds. Brian also visits Japan, and offers viewers the idea that man lives in just one of an infinite number of universes that are being made all the time.