Hundreds of years ago in faraway Iceland the Vikings began to write down dozens of stories called sagas - sweeping narratives based on real people and real events. But as Oxford University's Janina Ramirez discovers, these sagas are not just great works of art, they are also priceless historical documents which bring to life the Viking world. Dr Ramirez travels across glaciers and through the lava fields of Iceland to the far north west of the country to find out about one of the most compelling of these stories - the Laxdaela Saga.

Marcus du Sautoy uncovers the patterns that explain the shape of the world around us. Starting at the hexagonal columns of Northern Ireland's Giant's Causeway, he discovers the code underpinning the extraordinary order found in nature - from rock formations to honeycomb and from salt crystals to soap bubbles. Marcus also reveals the mysterious code that governs the apparent randomness of mountains, clouds and trees and explores how this not only could be the key to Jackson Pollock's success, but has also helped breathe life into hugely successful movie animations.

Professor Brian Cox takes on the story of the force that sculpts the entire universe - gravity. Gravity seems so familiar, and yet it is one of the strangest and most surprising forces in the universe. Starting with a zero gravity flight, Brian experiences the feeling of total weightlessness, and considers how much of an effect gravity has had on the world around us. But gravity also acts over much greater distances. It is the great orchestrator of the cosmos. It dictates our orbit around the sun, our relationship with the other planets in our solar system, and even the way in which our solar system orbits our galaxy. Yet the paradox of gravity is that it is actually a relatively weak force. Brian takes a face distorting trip in a centrifuge to explain how it is that gravity achieves its great power, before looking at the role it plays in one of the most extraordinary phenomena in the universe - a neutron star. Although it is just a few kilometres across, it is so dense that its gravity is 100, 000 million times as strong as on Earth. Over the centuries our quest to understand gravity has allowed us to understand some of the true wonders of the universe, and Brian reveals that it is scientists' continuing search for answers that inspires his own sense of wonder.

The rainforest is home to more species of plants and animals than any other habitat on the planet. But for humans, life there is not as easy as it looks. Life in the trees requires great skill, ingenuity and sheer bravery. The Matis of Brazil carve 4-metre-long blow-pipes to hunt monkeys - in near total silence. Deep in the Congo forests, Tete defies death by scaling a giant tree using nothing more than a liana vine, and he must then negotiate an angry swarm of bees - all to collect honey for his family. Three children from Venezuela's Piaroa tribe venture deep into the jungle to hunt tarantulas - to toast for lunch! In West Papua the Korowai tribe show-off their engineering skills by building a high-rise home 35 metres up in the tree tops. Most memorable of all, in Brazil we join a unique monitoring flight in search an un-contacted tribe...

From lush cloud forests to bare summits that take your breath away, the higher you climb the tougher life gets on a mountain. Human Planet explores the extraordinary ways in which people survive at extreme altitudes where nature becomes utterly unforgiving. In the Altai Mountains in Western Mongolia the vast open spaces make hunting for animals almost impossible, so the locals have forged an astonishing partnership with golden eagles which can do the hunting for them. On the precipitous cliffs of the Simien Mountains of Ethiopia we join a young boy locked in a dramatic battle with fearsome gelada monkeys which are hell-bent on raiding his family's meagre grain harvest. In the Himalayan state of Nepal - the roof of the world - we witness a rarely seen ceremony: a sky burial. In a land where there is little wood to burn for cremation, and where burying the dead is virtually impossible, the dead are fed to vultures in the ultimate reverence of nature.

The planets of our solar system have experienced epic catastrophes throughout their long history, both raining down from outside and bubbling up from within. We'll voyage back in time to investigate the violent events that profoundly shaped the planets, including earth itself. We'll witness stunning revelations about what transformed Mars into a barren, hostile desert... The disaster that changed Venus from temperate to hellish... The impact that blew away Mercury's mantle, turning it into a planetary core... A colossal disturbance that rearranged the orbits of the gas giants... Titanic impacts on Jupiter... And how a lost moon may finally explain Saturn's rings.