We always thought the living Earth was a thing of beauty. It isn’t. Life has had to learn to defend itself against the planet’s random geological savagery.

I will not be afraid because I understand ... And understanding is happiness.

One theory which can no longer be taken very seriously is that UFOs are interstellar spaceships.

Once you can reproduce a phenomenon, you are well on the way to understanding it.

My objection to organized religion is the premature conclusion to ultimate truth that it represents.

There is a special sadness in achievement, in the knowledge that a long-desired goal has been attained at last, and that life must now be shaped toward new ends.

Those wanderers must have looked on Earth, circling safely in the narrow zone between fire and ice, and must have guessed that it was the favourite of the Sun's children.