The universe is incredibly old, astoundingly vast and populated by trillions of planets -- so where are all the aliens? Astronomer Stephen Webb has an explanation: we're alone in the universe. In a mind-expanding talk, he spells out the remarkable barriers a planet would need to clear in order to host an extraterrestrial civilization -- and makes a case for the beauty of our potential cosmic loneliness. "The silence of the universe is shouting, 'We're the creatures who got lucky,'" Webb says. Check out more TED Talks: http://www.ted.com/ The TED Talks channel features the best talks and performances from the TED Conference, where the world's leading thinkers and doers give the talk of their lives in 18 minutes (or less). Look for talks on Technology, Entertainment and Design -- plus science, business, global issues, the arts and more. Follow TED on Twitter: http://www.twitter.com/TEDTalks Like TED on Facebook: https://www.facebook.com/TED Subscribe to our channel: null