I don't have much positive to say about motor neuron disease, but it taught me not to pity myself because others were worse off, and to get on with what I still could do. I'm happier now than before I developed the condition.

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

There is nothing bigger or older than the universe.

Science is not only a disciple of reason but, also, one of romance and passion.

We are very, very small, but we are profoundly capable of very, very big things.

Never put off the work till tomorrow what you can put off today.

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