Stephen Fry hosts a new landmark wildlife series exploring how our annual journey around the sun impacts nearly all life on Earth. As we orbit our star, it is on a tilted axis of around 23.5 degrees and this creates the seasons. For those in the northern hemisphere, Winter brings plummeting temperatures, darkening days and times of hunger. On Svalbard's frozen sea-ice, a polar bear mother is preparing her cub for a life alone. Each week without food, she loses around a tenth of her body weight.