There are too many accidents that can befall life on a single planet.

If it were only a few degrees, that would be serious, but we could adapt to it. But the danger is the warming process might be unstable and run away. We could end up like Venus, covered in clouds and with the surface temperature of 400 degrees. It could be too late if we wait until the bad effects of warming become obvious. We need action now to reduce emission of carbon dioxide.

A snooze button is a poor substitute for no alarm clock at all.

I want my books sold on airport bookstalls.

People think I'm a Simpsons character.

The real challenge is to work out what aliens might actually be like.

There is a fundamental difference between religion, which is based on authority, [and] science, which is based on observation and reason. Science will win because it works.