Carl took on the military-industrial complex. He campaigned around the world for an end to the production of weapons of mass destruction. To him it was a perversion of science.

A lot of people have this ego need that makes them want to believe that Earth is the center of the universe and humans are the most important species, the supreme expression of creation.

People think that if you are a scientist you have to give up that joy of discovery, that passion, that sense of the great romance of life. I say that's completely opposite of the truth.

This planet seems to be in such sorry shape. And I can't ever think about the rest of the universe without coming back home and thinking what the implications for life here would be if we were to really have some definitive proof of extraterrestrial life.

The Internet has turned the world into one gigantic linked community, capable of instantly sharing vast amounts of incorrect information.

The worst thing to do when I'm feeling insecure or a bit vulnerable is to scroll through Instagram. You only show when life is good on social media. Everyone looks happy all the time.

My day starts with Radio 4's Today live or 'listen again' wherever I am in the world, thanks to digital radio - I even have an app on my iPhone that receives it.

Everything has yet to be invented. I never say 'green' - I say 'greener.' It's greener simply because this is a continuum of change, improvement and discovery.