TED Tuesday: From redwoods to north pole

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.