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

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.

The Milky Way, our galaxy, is a magnificent sight in the night sky, but we know surprisingly little about it for certain. What is its shape? How many stars does it actually contain? What lies at its centre? The Gaia space telescope will answer these questions, being armed with the most advanced camera to leave our planet, and it will allow us to see our galaxy as we've never seen it before. The Sky at Night visits the factory in Chelmsford that made the astonishing sensor at the heart of the mission.

Scientific advancements are challenging the concept of what it means to be human. Technology embedded in our bodies is fairly common: artificial limbs, pacemakers. But new research is taking us beyond replacement parts and into a new realm that is changing the nature of the human body and the human mind. Will the fusion of biology and technology change how we think, how we feel, how we experience the world?

The mission of the film is to underline the crucial ecological role of coral reefs play in maintaining the well being of our planet, and to point out and warn against the dangers that are destroying the world's coral reefs. Entirely filmed using digital technology, thanks to it, the film was shot almost entirely with natural light, thus showing the underwater world as it exactly is. This is the closest you can get to dive without being there. Shot on the Great Barrier Reef in Australia and in the Bahamas, it brings to you the amazing beauty of the many varieties of coral and the immense diversity of the marine life thriving there.

The Internet is an uncontrollable labyrinth of content and imagery that operates under loose laws and partial anonymity - a new frontier where people can do anything and see anything, whether they should or not. In this lawless landscape, who's in control? The protectors? The abusers? In this episode meet the content moderators who watch the worst of the Internet so you don't have to; a convicted hacker whose punishment was the virtual prison of the unplugged; plus, a blackhat hacker who encrypts and holds computer files hostage.