Physicist, Paul Davies is interested in some of the biggest questions that we can ask. What is life? How did the universe begin? How will it end? And are we alone? His research has been broad and far-reaching, covering quantum mechanics, cosmology and black holes. In the 1980s he described the so-called Bunch-Davies vacuum - the quantum vacuum that existed just fractions of a second after the big bang - when particles were popping in and out of existence and nothing was stable.

As the chair of SETI (the Search for Extra-Terrestrial Intelligence) Post Detection Task Group, he’s the person responsible for announcing to the world when we make contact with aliens. He’s now Regents Professor of Physics at Arizona State University in the American south west where he runs research groups studying the evolution of cancer and the origins of life.

Paul Davies talks to Jim al-Khalili about how he applies the principles of physics to these big questions and about how he has worked closely with religious thinkers.

Producer: Anna Buckley