For centuries we have dreamt of reaching the centre of the Earth. Now scientists are uncovering a bizarre and alien world that lies 4,000 miles beneath our feet, unlike anything we know on the surface. It is a planet buried within the planet we know, where storms rage within a sea of white-hot metal and a giant forest of crystals make up a metal core the size of the Moon.
The air around us is not just empty space; it is an integral part of the chemistry of life. Plants are made from carbon dioxide, nitrogen nourishes the soil and oxygen gives us the energy we need to keep our hearts pumping and our brains alive. But how did we come to understand what air is made of? How did we come to know that this invisible stuff around us contains anything at all?
Off Australia's northeast coast lies a wonder of the world, a living structure so big it can be seen from space, more intricate and complex than any city, and so diverse it hosts a third of all fish species in Australia. The Great Barrier Reef as we know it -- 8,000 years old and home to thousands of marine species -- is dying in our lifetime.
Adventurer and journalist Simon Reeve heads to one of the most spectacular countries in the world - Colombia. For 50 years, Colombia has been in the grip of a brutal civil war that has killed more than 200,000 people and displaced seven million. But in late 2016, a peace deal was signed promising to end the conflict and finally bring peace to the country. In this hour-long documentary for the award-winning This World strand, Simon explores Colombia at a pivotal point in its history. He travels into the jungle and comes face to face with the guerrilla army FARC, which is now promising to lay down arms. In the Pacific coast city of Buenaventura, Simon finds out more about the fearsome right-wing paramilitary gangs who now dominate the cocaine trade. As the FARC abandon the countryside, there is a fear that these groups will only grow in power. Travelling in the countryside, Simon meets the coca farmers who are demanding government support to stop growing coca and stop the flow of money to criminal gangs. With land ownership, poverty and drugs at the heart of Colombia's problems, it is in the countryside that the country's precarious future will be decided.
Iain Stewart investigates a new and controversial energy rush for the natural gas found deep underground. Sometimes, this is right under the places people live in. Getting it out of the ground involves hydraulic fracturing - or fracking. Iain travels to America to find to find out what it is, why it is a potential game changer and what we can learn from the US experience. He meets some of the people who have become rich from fracking as well as the communities worried about the risks.
Over the last few years, our weather in Britain has become more extreme. Last winter was the wettest ever recorded, as deadly storms battered the country for weeks on end. But previous winters have seen bitter lows of -22, as Britain was plunged into a deep freeze. What everyone wants to know now is: why is our weather getting more extreme, can we expect to see more of it in the future, and has it got anything to do with climate change?