Between the blue sky above and the infinite blackness beyond lies a frontier that scientists have only just begun to investigate. In "At the Edge of Space," NOVA takes viewers on a spectacular exploration of the Earth-space boundary that's home to some of nature's most puzzling and alluring phenomena: the shimmering aurora, streaking meteors, and fleeting flashes that shoot upwards from thunderclouds, known as sprites.
As spring lights up the land, Alaska faces one of the greatest transformations on earth. Temperatures soar, and as the sun's rays hit the snow and ice, water, light and warmth return. Alaska's transition to spring may look magical, but for those animals emerging from a long winter's sleep, it's a time of intense competition, as everything is in a rush to cash in on Alaska's riches.
Modern life would be impossible without plastic – but we have long since lost control over our invention. Why has plastic turned into a problem and what do we know about its dangers? This video is a collaboration with UN Environment and their Clean Seas campaign, If you want to take action to turn the tide on plastics, go to http://www.cleanseas.org and make your pledge.
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.
Rip currents can appear without warning, turning an ideal beach outing into a horrific scene of chaos and panic. But groundbreaking new research could teach thousands of potential victims how to spot and escape these silent killers before it's too late.