Gravity is the most powerful and exacting force in the universe. It is pervasive and penetrating. Gravity binds us together, its reach hangs stars in the sky and its grip crushes light. Gravity holds planets together, and leashes them to their suns. Without gravity, stars, comets, moons, nebulae, and even the Earth itself would not exist. Explore how science and humanity discovered, overcame and utilized gravity. Learn what it takes to propel objects into the heavens, to ride a wave or to ski down a slope. Take a front row seat as an astronaut subjects himself to the weightless wonders of the specially modified aircraft used to train astronauts known as the "Vomit Comet."

Low Earth Orbit, 120 miles above sea level, is where the majority of space exploration has occurred. This 1,100 mile band around Earth is where--for a cool $20 million--any private citizen can take the vacation of his or her life on the International Space Station. Commercial prospects for LEO are huge; but dangers lurk for any individual willing to travel here--radiation, cosmic rays, and space debris numbering in the thousands threaten any spacecraft travelling in orbit. It's the new frontier, or the final frontier...and the possibilities are endless if you are willing to travel to the edge of space exploration.

In the 1960s and 1970s a generation of Mexican Americans, frustrated by persistent discrimination and poverty, find a new way forward, through social action and the building of a new "Chicano" identity. The movement is ignited when farm workers in the fields of California, led by Cesar Chavez and Dolores Huerta, march on Sacramento for equal pay and humane working conditions. Through plays, poetry and film, Luis Valdez and activist Corky Gonzalez create a new appreciation of the long history of Mexicans in the South West and the Mestizo roots of Mexican Americans. In Los Angeles, Sal Castro, a schoolteacher, leads the largest high school student walkout in American history, demanding that Chicano students be given the same educational opportunities as Anglos. In Texas, activists such as Jose Angel Gutierrez, create a new political party and change the rules of the electoral game. By the end of the 1970s Chicanos activism and identity have transformed what it means to be an American. Chicano and Latino studies are incorporated into school curriculum; Latinos are included in the political process.

Richard Dawkins deals with some of the philosophical and social ramifications of the theory of evolution. Dawkins starts out in Kenya, speaking with palaeontologist Richard Leakey. He then visits Christ is the Answer Ministries, Kenya's largest Pentecostal church, to interview Bishop Bonifes Adoyo. Adoyo has led the movement to press Kenya's national museum to sideline its collection of hominid bones pointing to man's evolution from ape to human.[5] The collection includes the Turkana Boy discovered by Kamoya Kimeu, a member of a team led by Richard Leakey in 1984. Dawkins discusses social darwinism and eugenics, explaining how these are not versions of natural selection, and that 'Darwin has been wrongly tainted'. He then meets with evolutionary psychologist Steven Pinker to discuss how morals can be compatible with natural selection. He goes on to explaining sexual selection, with peafowls as an example. To find out whether sexual selection plays a role for altruism and kindness among humans, he visits women who are looking for sperm donors, as well as a sperm bank manager. Dawkins also explains kin selection and selfish genes.

This episode discusses the human exploration of Antarctica, in particular the mission led by Captain Robert Falcon Scott, whose team died on the way back from the South Pole. It shows the scientific work in the modern human bases in Antarctica, especially Mawson Base and its observation of Adelie Penguins (partially through tracking devices). The second half of the episode describes how the series was made. Most crucial was of course the camera work. To get access to the wildlife of the sea, for example, boats, divers, suspended capsules and remotely controlled cameras mounted on inflatables were used. Particularly dangerous to divers were Leopard Seals and other predators. The film concludes that although working in Antarctica is now much easier than during the early days of exploration, human footsteps on the continent are still exceedingly rare in part because of international treaties prohibiting industrial exploitation.

It is a nightmare that has stalked us for centuries: hordes of human beings transformed into mindless, cannibalistic monsters. Could this civilization-ending nightmare become reality? Scientists have discovered pathogens that turn insects into the walking dead. New strains of viruses are attacking humans every day. Mathematicians have calculated the likelihood of surviving a zombie virus outbreak: they’re not hopeful. Now neuroscientists are discovering how easy it is for us to lose conscious control of our bodies. Are we at risk of becoming puppets? If we were in the middle of a zombie apocalypse, would we even know it?