In the second stop in his exploration of the wonders of the universe, Professor Brian Cox goes in search of humanity's very essence to answer the biggest questions of all: what are we? And where do we come from? This film is the story of matter - the stuff of which we are all made. Brian reveals how our origins are entwined with the life cycle of the stars. But he begins his journey here on Earth. In Nepal, he observes a Hindu cremation. Hindu philosophy is based on an eternal cycle of creation and destruction, where the physical elements of the body are recycled on to the next stage. Brian draws a parallel with the life cycle of the stars that led to our own creation. Next, he explains how the Earth's resources have been recycled through the ages. How every atom that makes up everything we see, was at some time a part of something else. Our world is made up of just 92 elements, and these same 92 elements are found throughout the entire universe. We are part of the universe because we are made of the same stuff as the universe.

Professor Brian Cox takes on the story of the force that sculpts the entire universe - gravity. Gravity seems so familiar, and yet it is one of the strangest and most surprising forces in the universe. Starting with a zero gravity flight, Brian experiences the feeling of total weightlessness, and considers how much of an effect gravity has had on the world around us. But gravity also acts over much greater distances. It is the great orchestrator of the cosmos. It dictates our orbit around the sun, our relationship with the other planets in our solar system, and even the way in which our solar system orbits our galaxy. Yet the paradox of gravity is that it is actually a relatively weak force. Brian takes a face distorting trip in a centrifuge to explain how it is that gravity achieves its great power, before looking at the role it plays in one of the most extraordinary phenomena in the universe - a neutron star. Although it is just a few kilometres across, it is so dense that its gravity is 100, 000 million times as strong as on Earth. Over the centuries our quest to understand gravity has allowed us to understand some of the true wonders of the universe, and Brian reveals that it is scientists' continuing search for answers that inspires his own sense of wonder.

It is high summer in the Polar Regions, and the sun never sets. Vast hordes of summer visitors cram a lifetime of drama into one long, magical day; they must feed, fight and rear their young in this brief window of plenty. Summer is a tough time for the polar bear family, as their ice world melts away and the cubs take their first swimming lesson. Some bears save energy by dozing on icy sun beds, while others go egg-collecting in an Arctic tern colony, braving bombardment by sharp beaks. There are even bigger battles on the tundra; a herd of musk oxen gallop to the rescue as a calf is caught in a life and death struggle with a pair of Arctic wolves. But summer also brings surprises, as a huge colony of 400,000 king penguins cope with an unlikely problem - heat. The adults go surfing, while the woolly-coated chicks take a cooling mud bath. Nearby, a bull fur seal is prepared to fight to the death with a rival. Fur flies as the little pups struggle desperately to keep out of the way of the duelling giants. Further south, a minke whale is hunted amongst the ice floes by a family of killer whales. The dramatic chase lasts over 2 hours and has never been filmed before. The killers harry the minke whale, taking it in turns to wear it down. Eventually it succumbs to the relentless battering. Finally, comical adelie penguins waddle back to their half a million strong colony like clockwork toys. The fluffy chicks need constant feeding and protection as piratical skuas patrol the skies. When an unguarded chick is snatched, a dramatic "dogfight" ensues.

For the animals in the polar regions, autumn means dramatic battles and epic journeys. Time is running out - the Arctic Ocean is freezing over and the sea ice is advancing at 2.5 miles per day around Antarctica. Polar bears gather in large numbers on the Arctic coast as they wait for the return of the ice. Soon, tempers fray and violent sparring contests break out. Meanwhile 2,000 beluga whales head for one special estuary, a gigantic 'whale spa' where they will thrash their snow-white bodies against the gravel and exfoliate. Inland, the tundra undergoes a dramatic transformation from green to fiery red. Here, musk ox males slam head-first into each other with the force of a 30mph car crash as they struggle to defend their harems. Frisky young caribou males play a game of 'grandma's footsteps' as they try to steal the boss's female. Down in Antarctica, Adelie penguin chicks huddle together in creches. When a parent returns from fishing, it leads its twins on a comical steeplechase - sadly there's only enough for one, so the winner gets the meal. Two months later and the chicks are fully feathered apart from downy Mohican hairdos - they're ready to take their first swim - reluctantly though, as it seems penguins are not born with a love of water! And with good reason - a leopard seal explodes from the sea and pulls one from an ice floe, a hunting manoeuvre that has never been filmed before. As winter approaches and everyone has left, the giant emperor penguin arrives and makes an epic trek inland to breed. The mothers soon return to the sea leaving the fathers to hold the eggs and endure the coldest winter on earth.

This episode focuses on the Jurassic period, a time when the first giant killers stalked the Earth and lurked in the seas; a time when the slightest advantage meant the difference between life and death. In North America the iconic allosaurus, an ambush hunter with a lethal bite, dominated. Not even the heavily-armoured stegosaurus was safe from this killer, and incredible evidence reveals a glimpse of a vicious battle between these two giants. Life in Jurassic oceans was no easier; in 2008, a fossil was dug out of a frozen island high in the Arctic. It was a colossal marine reptile, twice as big as most ocean predators, at 15 metres long and weighing about 45 tonnes. This was Predator X. Its skull alone was nearly twice the size of a tyrannosaurus rex's, and its bite force unmatched by anything in the Jurassic seas. The balance of power between predator and prey is a fine one, as prey continually evolves different ways to avoid predators. But for the most successful and enduring predators, the battle to survive has always been tipped in their favour

This episode of the documentary series focuses on the new giants, the heavyweights of the dinosaur world. It is only in recent years that experts have unearthed the biggest dinosaurs that ever lived. One monster eclipsed all others; more than seven times as heavy as diplodocus was the immense argentinosaurus - a single backbone was bigger than a human. For years, these giants were considered immune to attack from any predator - until the discovery of mapusaurus, a new giant killer whose fate appeared to be inextricably linked to argentinosaurus