A variety of cosmic events have both helpful and harmful effects on life on Earth. From the beauty of the Aurora Borealis and rainbows to the dangers of UV radiation and cosmic rays, from the miracle of photosynthesis to the thrill of a meteor shower, this episode explores how the effects generated by the sun and other extra-solar sources can literally get under our skin, scramble our technology, make life possible and threaten our existence all at the same time

Muhammad Ali was arguably the greatest boxer of the 20th century, and that rare fighter whose presence in the culture of the day was equal to (or perhaps even greater than) his remarkable skills in the ring. Ali was a superb fighter who squared off against a variety of gifted athletes during his career, and filmmaker Pete McCormack offers a new perspective on Ali through this documentary, in which some of his opponents speak about their experiences with the man. Facing Ali includes interviews with Joe Frazier, who speaks of the bitterness that still remains of his rivalry with Ali; George Chuvalo, a Canadian fighter who recalls that while Ali defeated him, he went dancing with his wife afterward while the winner went to the hospital; George Foreman, whose memories include a powerful punch that Ali chose not to land; Leon Spinks, whose 1978 upset victory over Ali thrust him into a level of fame he was not prepared to handle; Ernie Terrell, who discusses the technique and strategy behind Ali's approach; and many more.

In 1985, two adventurous young mountaineers, Joe Simpson and Simon Yates, set off to climb the treacherous west face of the Siula Grande in the Peruvian Andes. They were experienced climbers, and climbed "Alpine-style," climbing the mountain in "one great push," without setting up ropes or base camps ahead of time. After dealing with a snowstorm and some dangerous climbing over powder formations, they reached the summit (about 21,000 feet) on the third day. The climb down proved to be far more difficult. Simpson fell and broke his leg badly. Yates decided to try to lower Simpson down the mountain, one 300-foot section of rope at a time. The climbers had run out of gas to melt snow, so they couldn't risk stopping as night came, and a violent snowstorm began. Their plodding, painful journey hit a snag when Yates inadvertently lowered Simpson over the edge of a cliff. In the storm, the men couldn't hear each other's cries, and, Yates, uncertain as to Simpson's position, and gradually sliding down the slope himself, decided to cut the rope that connected them, sending Simpson plummeting to certain death. Miraculously, Simpson survived the fall, and was faced with the prospect of getting off the mountain alone with no food, no water, and a broken leg. In Touching the Void, filmmaker Kevin Macdonald (One Day in September) tells their story, based on Simpson's book, using contemporary interviews with the two men, and a reenactment of their climb and descent, featuring Brendan Mackey as Simpson and Nicholas Aaron as Yates

The first episode looks at how birds first took to the skies in the wake of the insects. It begins in Mexico, where Sir Attenborough observes bats being outmanoeuvred by a red-tailed hawk. Pterosaurs were the birds' forerunners, some 150 million years after dragonflies developed the means of flight, but eventually went extinct together with the dinosaurs. Birds had by then already evolved from early forms like archaeopteryx, the first creature to possess feathers. Its ancestry can be traced through reptiles, and some current species, such as the flying lizard, possibly show paths this evolution may have taken." One of the biggest birds to have ever existed was the terror bird, which proliferated after dinosaurs vanished and stood up to 2.5 metres tall. By comparison, the ostrich, while not closely related, is the largest and heaviest living bird. It was probably the evasion of predators that drove most birds into the air, so their flightless cousins evolved because they had few enemies. Accordingly, such species are more likely to be found on islands, and Sir Attenborough visits New Zealand to observe its great variety, most especially the kiwi. Also depicted is the moa, another huge creature that is now gone. The takahē is extremely rare, and high in the mountains of New Zealand, Sir Attenborough discovers one from a population of only 40 pairs. Finally, another example on the brink of extinction is the kakapo, which at one point numbered only 61 individuals. A male is heard calling — an immensely amplified deep note that can be heard at great distances from its nest.

A look at the practices of certain US states toward juvenile offenders convicted of murder. In the last five years, more juvenile offenders were killed in Texas than in the rest of the world combined. America continues to defend its right to execute children.

The Last Shaman James is an all American boy whose promising life is brought to a halt by acute depression. Turning his back on the most progressive western treatments and medicines, James discovers ayahuasca in search of healing in the Peruvian jungle. Over the course of 10 months venturing from Shaman to Shaman, James finds friendship, answers and a kind of redemption hidden deep in the Peruvian amazon. (Click CC for subtitles)