The question that will decide our destiny is not whether we shall expand into space. It is: shall we be one species or a million? A million species will not exhaust the ecological niches that are awaiting the arrival of intelligence.

The thing that makes me most optimistic is China and India - both of them doing well. It's amazing how much progress there's been in China, and also India. Those are the places that really matter - they're half of the world's population. They're the places where things are enormously better now than they were 50 years ago. And I don't see anything that's going to stop that.

In the history of science it has often happened that the majority was wrong and refused to listen to a minority that later turned out to be right.

Scepticism is as important for a good journalist as it is for a good scientist.

I mean science was blamed for all the horrors of World War I, just as it's blamed today for nuclear weapons and quite rightly.

Have felt it myself. The glitter of nuclear weapons. It is irresistible if you come to them as a scientist. To feel it's there in your hands, to release this energy that fuels the stars, to let it do your bidding. To perform these miracles, to lift a million tons of rock into the sky. It is something that gives people an illusion of illimitable power and it is, in some ways, responsible for all our troubles - this, what you might call technical arrogance, that overcomes people when they see what they can do with their minds.

In the end it is how you fight, as much as why you fight, that makes your cause good or bad.