Science writer Richard Preston talks about some of the most enormous living beings on the planet, the giant trees of the US Pacific Northwest. Growing from a tiny seed, they support vast ecosystems — and are still, largely, a mystery.
Lewis Pugh talks about his record-breaking swim across the North Pole. He braved the icy waters (in a Speedo) to highlight the melting icecap. Watch for astonishing footage — and some blunt commentary on the realities of supercold-water swims.