In the fourth episode of the series, legendary nature and cultural photographer Art Wolfe captures the great brown bear with the stunning backdrop of Alaska’s mountains and glaciers, immigrating wildebeests in the plains East Africa, and the hard-to-find gorillas of Uganda.

Professor Jim Al-Khalili investigates the amazing science of gravity. A fundamental force of nature, gravity shapes our entire universe. It sculpts galaxies and warps space and time. But gravity’s strange powers also affect our daily lives in the most unexpected ways. This is a story with surprises in store for Jim himself. In telling the story of gravity, his own understanding of the nature of reality comes to be challenged. Finally, Jim discovers that, despite incredible progress, gravity still has many secrets to unveil.

Laurie Anderson embarks on a cinematic journey through love, death and language. Cantering on Anderson's beloved rat terrier Lolabelle, who died in 2011, the film is a personal essay that weaves together childhood memories, video diaries, philosophical musings on data collection, surveillance culture and the Buddhist conception of the afterlife, and heartfelt tributes to the artists, writers, musicians and thinkers who inspire her. Fusing her own witty, inquisitive narration with original violin compositions, hand-drawn animation, 8mm home movies and artwork culled from exhibitions past and present, Anderson creates a hypnotic, collage-like visual language out of the raw materials of her life and art, examining how stories are constructed and told - and how we use them to make sense of our lives.

In the third episode, prominent adventure sports photographer Krystle Wright captures the immersive world of free-diving in Vanuatu, athletes who appear to walk on air in the canyons of Colorado, and powered para-gliders on the flooded salt pans of Utah.

The photographer of the second episode of the series is Richard I'Anson, who documents a fire rite, attempts to photograph the elusive Himalayan snow leopard and captures the colorful Festival of Holi.

In this series, the pursuit of the perfect image takes five adventurous photographers on journeys to the ends of the Earth, where they push the limits of their craft. In the first episode, Australian marine photographer Darren Jew captures mating humpback whales in Tonga, a 70-year-old biplane wreck and an active New Guinea volcano.