Beginning with the separation of the fuzzy thinking and pious fraud of astrology from the careful observations of astronomy, Sagan follows the development of astronomical observation. Beginning with constellations and ceremonial calendars (such as those of the Anasazi), the story moves to the debate between Earth and Sun-centered models: Ptolemy and the geocentric worldview, Copernicus' theory, the data-gathering of Tycho Brahe, and the achievements of Johannes Kepler (Kepler's laws of planetary motion and the first science-fiction novel).

Since Caesar's days, Germanic warriors and Roman legionaries had often met in battle. Rome's power seemed invincible. But then, in the year 9 AD, the Germans mounted a rebellion.

East Africa is a land which is constantly changing. To survive here, creatures must be able to deal with unpredictable twists and turns - wet turning to dry, feast to famine, cold to hot - no matter how hostile it becomes. From dense forests to snow capped peaks, steamy swamps and endless savannah, this unique and varied land is also a haven for life, supporting large animals in numbers found nowhere else on Earth. But away from the familiar, forever-travelling herds, there are a huge cast of other characters - lizards that steal flies from the faces of lions, vast dinosaur-like birds who stalk catfish through huge wetlands, and an eagle who risks everything on the arrival of ten million bats from a far off rainforest.

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.

We all agree lying is shameful. Yet we still deliberately deceive each other constantly. Are our brains wired for lying from a young age? The brains of pathological liars may provide insights. Will technology make it easier for us to be dishonest, or could it someday instantly reveal someone is lying? Perhaps we are deceitful because our limited senses prevent us from seeing the real truth. Scientists say our own memories deceive us, and have managed to implant false memories. Other scientists look for ultimate truth in the subatomic world … only to end up turning reality on its head.

How does light escape from the sun? We take a journey from the center of the sun, following the path of light. We witness its fiery birth from in the core, its 430,000 mile battle against gravity and magnetism, and its escape from the solar surface.