Dark energy - the mysterious force that is unexpectedly causing the universe's expansion to speed up. The effects of dark energy were discovered in 1998 but physicists still don't know what it is. Worse, its very existence calls into question Albert Einstein's general theory of relativity - the cornerstone of modern physics. The hunt for the identity of dark energy is on". Experiments on earth and in space generate data that might provide a clue, but there are also hopes that another Einstein might emerge - someone who can write a new theory explaining the mystery of the dark energy.

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.

Follow astronaut Scott Kelly’s record-breaking 12-month mission on the International Space Station, from launch to landing, as NASA charts the effects of long-duration spaceflight. A Russian Soyuz spacecraft carried Scott Kelly of NASA and Mikhail Kornienko of Roscosmos to the space station for the longest space mission ever assigned to a NASA astronaut". The expedition provided important insights into operational and scientific areas in human research in space and on Earth. Integrated scientific investigations between NASA and Roscosmos will combine resources to improve data sharing among space medical and human research communities, as well as help inform current assessments of crew performance and health and better determine and validate countermeasures to reduce the risks associated with future exploration as NASA plans for missions around the moon, to an asteroid and eventually to Mars.

A dynamic journey behind the scenes of the next step in the evolution of telescopes: NASA's James Webb Space Telescope. A new generation has been inspired to design and build this massive instrument, which is 100 times more powerful than the Hubble Space Telescope and will be a veritable time machine, capable of looking back on the origins of our universe and identifying signatures of potential life on planets far outside our solar system". With unprecedented access to the people and technologies that power its creation, including astrophysicists, engineers at Northrop Grumman, and personnel from NASA'S Goddard Space Flight Center and the Space Telescope Science Institute, the operations center for Hubble and Webb, Telescope spotlights the high-stakes mission of building this massive new scientific instrument. The film is a comprehensive look at the dynamic history of 400 years of telescopes starting with Galileo in 1609. The Webb is the next great telescope in society's ongoing mission to see farther into the universe and answer fundamental questions that have haunted mankind from the beginning of time. Directed by Oscar nominated filmmaker Nathaniel Kahn

Every day our planet faces cataclysmic events that threaten our very existence. Whether from natural or man-made forces, rising from the earth or menacing from space, the world seems beset by more catastrophes than ever. Some believe the signs of the coming Apocalypse are all around us–as outlined in the bible’s most compelling book of prophecies: Revelation". And even the non-religious can’t ignore what appears to be a growing rate of globe-threatening disasters. Are we approaching a biblical “End of Times”? And if so–how will it happen? Will it come from an act of God? Or a colossal misstep of man? Get an uncomfortably close front row seat to some of the most likely apocalyptic scenarios our world faces today–and the history, both scientific and biblical, behind them.

Explore the latest science behind the headlines and the coolest scientific developments that impact our lives. Technology catapults to new heights in 2015, going faster and further than ever before. We have canvassed the world in search of the best and most fascinating science and tech stories of the year for 2015 YEAR IN SCI-TECH". This action-packed hour of fun and intrigue revisits the world’s first glimpse of Pluto and images of water on Mars while exploring what this all could mean for intelligent life in the universe – all while earthling’s inch closer to becoming actual space tourists. Throughout the hour, we revisit the year’s most amazing techological feats and scientific discoveries, including new and elusive animal species discovered deep under the ocean, as well as the hottest tech trends – from hover boards to driverless cars and trucks, and the newest advances in mind-blowing virtual reality.