In keeping with the theme of TED2008, professor Stephen Hawking asks some Big Questions about our universe -- How did the universe begin? How did life begin? Are we alone? -- and discusses how we might go about answering them.

Scientists describe the discovery of organic molecules on the planet HD 189733b (Courtesy NASA/ESA/M Estacion/STScI)

Within the next 20 years, we may discover another planet capable of supporting life. What might such a planet look like? Where are we most likely to find it first? What types of life could be possible? These questions and more are explored by astronomers,astrophysicists, and biologists in this National Geographic special presentation. ...