90 million miles away from us is the power that shapes our world - the sun. We see it shine in the sky above us, but beyond our sight something dramatic is happening - the sun is going into overdrive.
Venture into the danger zone of two volcanic craters posing widely divergent threats. Hawaii's Kilauea is a shield volcano that threatens communities with its slow-but-relentless lava flow, while the Sumatran Sinabung is a stratovolcano delivering carnage via a sudden and explosive surge of superheated gas and rock.
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.
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.