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

Andrew Graham-Dixon reveals how the Medici family transformed Florence through sculpture, painting and architecture and created a world where masterpieces fetch millions today. Without the money and patronage of the Medici we might never have heard of artists such as Donatello, Michelangelo or Botticelli, and Graham-Dixon examines how a family of shadowy, corrupt businessmen, driven by greed and ambition, became the financial engine behind the Italian Renaissance.

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.

Fifty years ago there were close to half-a-million lions in Africa. Today there are around 20,000. To make matters worse, lions, unlike elephants, which are far more numerous, have virtually no protection under government mandate or through international accords. This is the jumping-off point for a disturbing, well-researched and beautifully made cri de coeur from husband and wife team Dereck and Beverly Joubert, award-winning filmmakers from Botswana who have been Explorers-in-Residence at National Geographic for more than four years. Pointing to poaching as a primary threat while noting the lion's pride of place on the list for eco-tourists-an industry that brings in 200 billion dollars per year worldwide-the Jouberts build a solid case for both the moral duty we have to protect lions (as well as other threatened "big cats," tigers among them) and the economic sense such protection would make. And when one takes into account the fact that big cats are at the very top of the food chain-and that their elimination would wreak havoc on all species below them, causing a complete ecosystem collapse-the need takes on a supreme urgency.

Investigative journalist Jeremy Scahill travels to Afghanistan, Yemen, Somalia, and other countries where the United States has taken military action in the War on Terror. In Afghanistan, he investigates the United States military and government cover-up of the deaths of five civilians, including two pregnant women killed by US soldiers from the Joint Special Operations Command. After investigating the attack, Scahill travels to other sites of JSOC intervention, interviewing both proponents and opponents, and the survivors, of such raids,including U.S. Senator Ron Wyden. Scahill also investigates the assassinations of American citizens Anwar al-Awlaki and his son Abdulrahman al-Awlaki, meeting with their family at their home in Yemen. Scahill suggests that the War on Terror is in fact a "self-fulfilling prophecy" and causes the radicalization of Muslims. He also discusses the case of Yemeni investigative journalist Abdulelah Haider Shaye who was detained, tried and sentenced on terrorism-related charges after reporting on American drone strikes.

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?