The search for extraterrestrial life

It's a search that has fired the imagination of countless people the past century, but even though humans have discovered almost two thousand planets - or exoplanets - outside our solar system, we've yet to discover any traces of life. Well, for a few days last month it was as if newsrooms around the world had been taken over by 12-year-old science geeks. NASA's New Horizons probe gave us our first close-up look at Pluto. But the excitement doesn't end there.

On another recent mission the Kepler space telescope discovered the closest thing we've found yet to another Earth - a roughly Earth-sized planet christened Kepler 452b - 1400 hundred light years away. It's the right distance from the right kind of star to have water in liquid form, which makes it a candidate to harbour life. And that makes it a candidate for research by SETI - the Search for Extraterrestrial Intelligence program - which got a huge funding boost from billionaire Yuri Milner.

Flanked by Stephen Hawking and other renowned scientists at the Royal Society in London, Milner announced he was investing $100 million into the Breakthrough Initiative: a 10 year program to search for intelligent life beyond the solar system.

These are heady times for space exploration and the quest to discover life beyond our planetary boundaries. But what exactly are we looking for? How will we know if we've found it? And if we do, what then? Guest host and admitted science fiction nerd Kevin Sylvester gets the answers from Dan Werthimer and Paul Davies, two of the scientists most deeply involved in the search and the big questions it raises.