In the last in the series Professor Jim Al-Khalili explores how studying the atom forced us to rethink the nature of reality itself. He discovers that there might be parallel universes in which different versions of us exist, finds out that empty space isn't empty at all, and investigates the differences in our perception of the world in the universe and the reality.

Montezuma Dan Snow journeys to the ancient heart of Mexico in search of the lost civilisation of the Aztecs and their last and greatest ruler, Montezuma II (1502-1520). Montezuma inherited an empire of five million people, stretching from present-day Mexico to Nicaragua, from his uncle. His rule was marked by incessant warfare. Enemy states were growing more powerful and conquered tribes were becoming more rebellious. Within months of taking the throne in 1502, he went changed a man of good reason into a pitiless autocrat who declared himself a god, believing that fear and ruthlessness were the only ways to stop the empire falling apart. Yet it was at the hands of Cortes and the Spanish conquistadors that Montezuma met his downfall. But what was his relationship with Cortes, and why did such a ruthless leader submit to his captors with such relative ease? As Dan Snow visits the ruins and picks through current excavations, he pieces together the evidence of a gripping story: a divine tragedy of errors, the clash of civilisations, the end of a world - and a very human God.

The definitive discourse with Noam Chomsky on the defining characteristic of our time - the deliberate concentration of wealth and power in the hands of a select few. Chomsky unpacks the principles that have brought us to the crossroads of historically unprecedented inequality - tracing a half century of policies designed to favour the most wealthy at the expense of the majority. "Requiem for the American Dream" is profoundly personal and thought provoking. Chomsky provides penetrating insight into what may well be the lasting legacy of our time - the death of the middle class, and swan song of functioning democracy. A potent reminder that power ultimately rests in the hands of the governed, "Requiem for the American Dream" is required viewing for all who maintain hope in a shared stake in the future.

We can survive for weeks without food, but only days without water: it is the essential element of life. Yet many millions of us live in parched deserts around the world. In the second episode of Human Planet, we discover how the eternal quest for water brings huge challenges - and ingenious solutions - in the driest places on Earth. Battling through a sand storm in Mali, Mamadou must get his cows to a remote lake but desert elephants have arrived first. Can he find a safe way through the elephant blockade? Alone for weeks on end, Tubu women and children navigate the endless dunes of the Sahara. How does young Shede know where to find the last oasis, three days walk across the sea of sand? At the height of the drought we witness a spectacular frenzy: two thousand men rushing into Antogo Lake to catch the fish trapped by the evaporating water. When the rain finally arrives in the desert it's a time for flowering and jubilation - and love. The Wodaabe men of Niger put on make-up for an intoxicating courtship dance and beauty contest.

Einstein's world-shaking Theory of Relativity says that time travel is perfectly possible -- if you're going forward in time. Finding a way to travel backwards requires breaking the speed of light, which so far seems impossible. But now, strange-but-true phenomena such as quantum nonlocality (where particles instantly teleport across vast distances) may give us a way to make the dream of traveling back and forth through time a reality. Step into a time machine and rewrite history, bring loved ones back to life, control our destinies. But if succeed, what are the consequences of such freedom? Will we get trapped in a plethora of paradoxes and multiple universes that will destroy the fabric of the universe?

A feature documentary about the Soviet Union and the most successful dynasty in sports history: the Red Army hockey team. Told from the perspective of its captain Slava Fetisov, the story portrays his transformation from national hero to political enemy. From the USSR to Russia, the film examines how sport mirrors social and cultural movements and parallels the rise and fall of the Red Army team with the Soviet Union. RED ARMY is an inspiring story about the Cold War played out on the ice rink, and a man who stood up to a powerful system and paved the way for change for generations of Russians. From Oscar nominated and Emmy award-winning filmmaker Gabe Polsky.