For centuries, the precise workings of gravity have confounded the greatest scientific minds - from Newton to Faraday and Einstein - and the idea of controlling gravity has been seen as little more than a fanciful dream. Yet in the mid 1990s, UK defence manufacturer BAE Systems began a ground-breaking project code-named Greenglow. Nasa was simultaneously running its own Breakthrough Propulsion Physics Project". It was concerned with potential space applications of new physics, including concepts like 'faster-than-light travel' and 'warp drives'. Looking into the past and projecting into the future, Horizon explores science's long-standing obsession with the idea of gravity control. It looks at recent breakthroughs in the search for loopholes in conventional physics and examines how the groundwork carried out by Project Greenglow has helped change our understanding of the universe. Gravity control may sound like science fiction, but the research that began with Project Greenglow is very much ongoing, and the dream of flying cars and journeys to the stars no longer seems quite so distant.

As the early June sun begins to set over a calm river in Central Hungary, masses of ghostly shapes emerge from their larval cases to take to the air for the first time. They are mayflies and in a spectacular display, thousands of them demonstrate how the very first wings were used. From the stunning aerobatics of hoverflies in an English garden to the mass migration of purple crow butterflies in the valleys of Taiwan, this episode tells the tale of the first animals ever to take to the air. Unique footage reveals the lightning fast reactions of bluebottles and hoverflies, filmed with one of the world's fastest cameras, and Sir David Attenborough handles the world's largest (and perhaps most ferocious) insect - the Titan beetle.

More than a film, it was conceived as a gift to the public and has been a major event all over the globe. Since World Environment Day, June 5, 2009, when it was released worldwide across all media platforms more than 400 million people have watched the film. Home is truly an astounding cinematic experience - a soulful voyage, a feast for the eyes, a thought-provoking and unforgettable journey. Directed by Yann Arthus-Bertrand

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.

Citizenfour received the Academy Award for Best Documentary Feature at the 2015 Oscars. The film was directed by Laura Poitras concerning Edward Snowden and the NSA spying scandal." In January 2013, Laura Poitras received an encrypted e-mail from a stranger who called himself Citizen Four. In it, he offered her inside information about illegal wiretapping practices of the NSA and other intelligence agencies. Poitras had already been working for several years on a film about monitoring programs in the US, the result of the September 11 attacks. In June 2013, accompanied by investigative journalist Glenn Greenwald and The Guardian intelligence reporter Ewen MacAskill, she went to Hong Kong with her camera for the first meeting with the stranger, who identified himself as Edward Snowden. Several other meetings followed. The recordings gained from the meetings form the basis of the film.

In AD 856, a massive fleet of Viking ships appeared off the coast of East Anglia, heralding a change in Viking tactics - from raiding to invasion. Richards charts the years of attempted conquest that followed.