In 2014, the International Space Station had to move three times to avoid lethal chunks of space debris and there is an increasing problem of satellites mysteriously breaking down. With first-hand accounts from astronauts and experts, know the scale of the problem of space junk. Our planet is surrounded by hundreds of millions of pieces of junk moving at 17,000 miles per hour. Now the US government is investing a billion dollars to track them, and companies around the world are developing ways to clear up their mess - from robot arms to nets and harpoons. Learn the science behind the hit film Gravity and discovers the reality is far more worrying than the Hollywood fiction.

A documentary-horror film exploring the phenomenon of 'Sleep Paralysis' through the eyes of eight very different people. These people often find themselves trapped between the sleeping and waking worlds, totally unable to move but aware of their surroundings while being subject to frequently disturbing sights and sounds. A strange element to these visions is that despite the fact that they know nothing of one another, many see similar ghostly 'shadow men.' This is one of many reasons many people insist this is more than just a sleep disorder". This documentary digs deep into not only the particulars of these eight people's uncanny experiences, but it also explores their search to understand what they've gone through and how it's changed their lives. Directed by Rodney Ascher, he chose to focus on sleep paralysis as it had happened to him in the past. The film's crew initially began approaching participants via message groups, videos and a half dozen books that had been written.

This absolutely beautiful documentary on our World, its mystical beauty and miracles including slow motion footage of nature, animals, seasons, new life and daily beauties I've never seen nor imagined existed. The photography is sensational. The animal behaviour shown is incredible, beautiful and humorous. Even if you never have been a fan of nature documentaries, this blew you away

The digital era gives rise to unprecedented opportunity to exploit, and be exploited. Troves of child pornography are available at the click of a mouse. Who are these children - and who profits from their abuse? While facilitating the darker side of our impulses, technology is also being touted as a cure to rehabilitate predators. In this episode meet the children who are forced to perform sex acts on camera; people who use the same technology to protect kids and nab the perpetrators; plus, a pedophile who reveals the roots of his addiction.

Today, the topic of climate change is a major part of daily life, yet 40 years ago it was virtually unheard of. Since then, Horizon have followed scientists as they have tried to unpick how the climate works and whether it is changing. Dr Helen Czerski delves into this unique archive to chart the transformation of a little-known theory into one of the greatest scientific undertakings in history. It has been a constantly surprising journey of discovery that has revolutionised our understanding of climate, and seen scientists face unprecedented controversy and criticism.

Join investigators as they untangle the cause of Alzheimer’s and race to develop a cure. Alzheimer’s disease strikes at the core of what makes us human: our capacity to think, to love, and to remember. The disease ravages the minds of over 40 million victims worldwide, and it is one of the greatest medical mysteries of our time. Join investigators as they gather clues and attempt to reconstruct the molecular chain of events that ultimately leads to dementia". Follow key researchers in the field who have helped to develop the leading theories of the disease. Along the way, meet individuals from all walks of life who will reveal what it’s like to struggle with Alzheimer’s. Among them, members of a unique Colombian family who have learned that their genetic predisposition all but guarantees early onset Alzheimer’s. Yet there may be hope. Join these courageous patients participating in clinical trials, and then go behind the scenes of the major drug trials to see how researchers target and test therapies that may slow and even prevent Alzheimer’s