Al-Khalili travels to northern Syria to discover how, a thousand years ago, the great astronomer and mathematician Al-Biruni estimated the size of the earth to within a few hundred miles of the correct figure. He discovers how medieval Islamic scholars helped turn the magical and occult practice of alchemy into modern chemistry. In Cairo, he tells the story of the extraordinary physicist Ibn al-Haytham, who helped establish the modern science of optics and proved one of the most fundamental principles in physics - that light travels in straight lines. Prof Al-Khalili argues that these scholars are among the first people to insist that all scientific theories are backed up by careful experimental observation, bringing a rigour to science that didn't really exist before.

In the last episode, Al-Khalili turns detective, hunting for clues that show how the scientific revolution that took place in the 16th and 17th centuries in Europe had its roots in the earlier world of medieval Islam. He travels across Iran, Syria and Egypt to discover the huge astronomical advances made by Islamic scholars through their obsession with accurate measurement and coherent and rigorous mathematics.He then visits Italy to see how those Islamic ideas permeated into the west and ultimately helped shape the works of the great European astronomer Copernicus, and investigates why science in the Islamic world appeared to go into decline after the 16th and 17th centuries, only for it to re-emerge in the present day. Al-Khalili ends his journey in the Royan Institute in the Iranian capital Tehran, looking at how science is now regarded in the Islamic world

Fly over Africa on the back of a vulture and see the most animal-packed continent with fresh eyes. Arrow-dive with cape gannets among sharks, dolphins and whales as they join the great sardine run. Soar with fish eagles as they discover an S-shaped living island comprised entirely of flamingos, and join them on a spectacular hunt. Fly with kelp gulls as they study the hunting behaviour of the greatest underwater predator of all: the great white shark. On the wings of eagles, fly through the mist-filled Victoria Falls and dive for fish in the mighty Zambezi. Circle with vultures high above the Serengeti as they watch the drama of the wildebeest migration below, and discover what happens when this canny scavenger suddenly becomes prey. Among toxic soda lakes, find out what it is like to be a flamingo, vulnerable to every predator on the continent, including baboons and hyenas. Join these flamingos as they take part in one of the most beautiful dances in the bird world. This is Africa as never seen before - from the wings of birds

This episode includes footage of wildlife inhabiting underwater kelp forests, thousands of giant cuttlefish spawning along a restricted area of rocky reef off the south coast of Australia. Males outnumber females 11 to one, which leads to fierce competition. Larger males use brute force to drive off competition, while their smaller rivals use deception by mimicking the appearance of females. The programme also features tiger sharks hunting for green turtles in fields of seagrass and spider crabs trying to avoid predators while they shed their shells.

The turmoil of 1968 helps Nixon win the presidency. Troop strength in Vietnam peaks and the draft accelerates. Karl Marlantes endures bitter jungle fighting on Hill 484, and draftee Arthur Wiknik gets a grim introduction to combat on 'Hamburger Hill'. But shortly after winning both hills, US troops abandon them.

'It's really about terror and intimidation and people basically fighting for survival and often committing extraordinary violence in order to protect themselves or to stay safe. It's kind of like the weak dog in the pack. If others spot weakness, they're gonna pounce on you for a couple of reasons. You pounce on that guy, that gives you a little more status. So, I had to ask myself, are you gonna be a victim? No, I ain't gonna be a victim. Well, that really only left me one choice in my mind. That means I gotta be the victimizer. At some point, for some reason, might be legitimate, might not be, someone's gonna test you.. Even if you lose, you're gonna have to stand up for yourself. '
'A guy comes over, and it's your day to get your package, and he tries to take your package from you that your people sent you, if you let him do it, there's gonna be 10 other dudes, oh, yeah, he let that guy take his package, I'm gonna go get his TV, right down the line until somebody's after your ass. But if you stand up that first time and they see you'll stand up for yourself, even if you lose, people will respect that. Oh, don't mess with him. There's easier prey. Why do you have to go and get that guy and get a couple lumps for it when he can go get that guy's stuff over there, don't cost you nothing. It usually only has to happen once or twice but just as importantly that you didn't go to the man for help... you're gonna be all right.'