A stunning documentary about the escalating global nuclear arms crisis, Countdown to Zero is a fascinating and frightening exploration of the dangers of nuclear weapons, exposing a variety of present day threats and featuring insights from a host of international statesmen and experts. Among the voices are President Jimmy Carter, Mikhail Gorbachev, Pervez Musharraf, Tony Blair, former CIA Operations Officer Valerie Plame Wilson, the Ploughshares Fund’s Joe Cirincione and Stanford political scientist Scott Sagan. traces the history of the atomic bomb from its origins to the present state of global affairs: nine nations possessing nuclear weapons capabilities and others racing to join them, with the world held in a delicate balance that could be shattered by an act of terrorism, failed diplomacy, or a simple accident. It makes a compelling case for worldwide nuclear disarmament, an issue more topical than ever with President Obama and other world leaders working to revive this goal today. Written and directed by Lucy Walker, Countdown to Zero was screened for attendees of this year’s Global Zero International Conference in Paris and the TED Conference in Long Beach, California.

Principles of generosity and prosperity inform the selection of the last two crew members: Christopher Sembroski, a former member of the U.S. Air Force who served in Iraq and now works as a Lockheed Martin engineer, and Sian Proctor, a professor of geosciences and two-time NASA astronaut candidate. Excitement for the flight ramps up, but anxiety lingers.

In the dark depths of the oceans, nearly 90% of all species light up the darkness from within. These creatures flash, sparkle, shimmer, or simply glow. Whether it’s to scare off predators, fish for prey, or lure a mate, the language of light is everywhere in the ocean depths, and scientists are finally starting to decode it. Discover surprising ways to harness nature’s light—from tracking cancer cells to detecting pollution, lighting up cities, and even illuminating the inner workings of our brains.

They're the cooling corpses of stars like our sun, but new research proves white dwarfs are one of the driving forces of our universe. And they can tell us literally about the nature of the cosmos itself. Have scientists finally discovered how these small stars could be such massive galactic players?

brilliant mathematicians, whose genius has profoundly affected us, but which tragically drove them insane and eventually led to them all committing suicide. Georg Cantor, the great mathematician whose work proved to be the foundation for much of the 20th-century mathematics. He believed he was God's messenger and was eventually driven insane trying to prove his theories of infinity. Ludwig Boltzmann's struggle to prove the existence of atoms and probability eventually drove him to suicide.

We all project images of ourselves online - a curated identity that defines how we want to be perceived. But what temptations exist to embellish and what are the dark implications? In this episode, enter the world of Cyberbanging, where inner city youth are using social media to brag, conspire and incite violence; two African-American women bloggers who have turned the table on the trolls who threaten them; and the creator of Abdullah X, an online character who's trying to keep Muslim kids from falling under the spell of Islamic extremists.