Tyson begins the episode by explaining the nature of the speed of light and how much of what is seen of the observable universe is from light emanated from billions of years in the past. Tyson further explains how modern astronomy has used such analyzes via deep time to identify the Big Bang event and the age of the universe. Tyson proceeds to describe how the work of Isaac Newton, William Herschel, and James Clerk Maxwell contributed to understanding the nature of electromagnetic waves and gravitational force, and how this work led towards Albert Einstein's Theory of Relativity, that the speed of light is a fundamental constant of the universe and gravity can be seen as distortion of the fabric of space-time. Tyson describes the concept of dark stars as postulated by John Michell which are not visible but detectable by tracking other stars trapped within their gravity wells, an idea Herschel used to discover binary stars. Tyson then describes the nature of black holes, their enormous gravitational forces that can even capture light, and their discovery via X-ray sources such as Cygnus X-1. Tyson uses the Ship of Imagination to provide a postulate of the warping of spacetime and time dilation as one enters the event horizon of the black hole, and the possibility that these may lead to other points within our universe or others, or even time travel. Tyson ends on noting that Herschel's son, John would be inspired by his father to continue to document the known stars as well as contributions towards photography that play on the same nature of deep time used by astronomers.

A Winning Design clarifies what makes a mammal different from reptiles and birds. No, it isn't egg-laying: both the platypus and the echidna are egg-laying mammals; it's their ability to adapt. And it's this adaptability that becomes the crux of the remainder of the series. From the tiniest bat to the massive blue whale, all mammals share the ability to nurture their young on milk and regulate their own temperatures.

Once life arrived in the Galapagos, it exploded into unique and spectacular forms. David Attenborough investigates the driving forces behind such evolutionary innovations. We learn that life must be able to adapt quickly in these ever-changing volcanic landscapes. It has resulted in species found nowhere else in the world, such as giant whale sharks and marine iguanas that can spit sea-salt from their noses, dandelion seeds that grow into tree-sized plants and spiders that can blend perfectly into the darkness. Adaptation has been the key to survival in these islands so far, but the story of life in the Galapagos doesn’t end here. The catalyst that triggers these explosions of life remains in place.

David Attenborough narrates the intimate story of a leopard mother and her two cubs. This very special family must survive in the wilds of Botswana alongside some less-than-friendly neighbours: lions, wild dogs and hyenas. The competition for food is tough, and if they are going to make it they must learn a new skill - they must learn to fish. This is an epic family drama. With them every step of the way is local cameraman Brad Bestelink. Brad's 18-month journey following the lives of these secretive big cats offers a rare glimpse into an otherwise hidden world.

Sir David Attenborough takes a breath-taking journey through the vast and diverse continent of Africa as it's never been seen before. From the richness of the Cape of Good Hope to blizzards in the high Atlas Mountains, from the brooding jungles of the Congo to the steaming swamps and misty savannahs, Africa explores the whole continent. An astonishing array of previously unknown places are revealed along with bizarre new creatures and extraordinary behaviours. Using the latest in filming technology including remote HD cameras, BBC One takes an animal's eye view of the action. The journey begins in the Kalahari, Africa's ancient southwest corner, where two extraordinary deserts sit side by side and even the most familiar of its creatures have developed ingenious survival techniques. Black rhinos reveal a lighter side to their character as they gather around a secret waterhole. Springbok celebrate the arrival of rains with a display of 'pronking'. Bull desert giraffes endure ferocious battles for territory in a dry river bed.

An epic true story set against the backdrop of one of the wildest places on Earth, African Cats captures the real-life love, humour and determination of the majestic kings of the savannah. Narrated by Samuel L. Jackson, the story features Mara, an endearing lion cub who strives to grow up with her mother’s strength, spirit and wisdom; Sita, a fearless cheetah and single mother of five mischievous newborns; and Fang, a proud leader of the pride who must defend his family from a rival lion and his sons.