600 miles off the coast of South America in the Pacific Ocean there are 120 tropical islands that erupted from the deep ocean floor more than 10 million years ago. Journey from the lava ramparts to its fiery heart, we'll discover how the Galapagos archipelago became one of the most important areas of biodiversity in the world. Those swept here by storms and currents survived million to one odds to find untouched islands free from competition. These hardy pioneers evolved in remarkable ways in what's known as Nature's Greatest Experiment. Home to bizarre specialists and unexpected giants, the most precious collection of island creatures on Earth.
In Southeast Alaska, there's an ice-bound Eden that harbors possibly the richest temperate rainforests of all. Where the coastal mountains meet the Pacific, lays the Alexander Archipelago, a remote island chain running for almost 300 miles along the Alaskan Panhandle. This frozen frontier is one of the last great wildernesses of North America. And a stronghold for the country's highest diversity of megafauna, feasting on the abundance of fleeting summers to make it through relentless winters.
In astronomy, we've been looking at different kinds of light and opening up the universe a little bit more of the time. But then in 2015, the roof came off. Something happened that changed everything, the ability to see waves in space and time itself. Gravitational waves help us roll back the clock to the dawn of time, discover epic cosmic collisions, on make Earth-shaking discoveries. Gravitational waves are the biggest game changer since the invention of the telescope. We have a completely new universe to view now. A new exploration of space is just beginning.
Seafood is a substantial part of the daily diet of over three billion people and oceans absorbs almost a third of all the greenhouse gases we emits. Buy the ocean it is not what it once was. Scenes of extraordinary ocean abundance now only exist in far-off places or in tales from the past. We urgently need to mend our relationship with our oceans and allow them to thrive once again. Prince William, David Attenborough and Shakira find out about inspiring people and projects across the world that can help us stop damaging the oceans and enable their revival.
Will Smith confronts his fear of nature on powerful white-water rapids in Iceland. "Over five expeditions, I've followed explorers into situations that were straight-up scary. It was worth it to discover the Earth's wonders. But your boy was tripping more than once. Because when I see wilderness, you know, nothing but nature, I get nervous because I don't understand it."
Those swept here by storms and currents survived million to one odds to find untouched islands free from competition. These hardy pioneers evolved in remarkable ways in what's known as Nature's Greatest Experiment. Home to bizarre specialists and unexpected giants, the most precious collection of island creatures on Earth.