The moment when one first meets a great work of art has an impact that can never again be recaptured.

I have encountered a few "creationists" and because they were usually nice, intelligent people, I have been unable to decide whether they were really mad or only pretending to be mad. If I was a religious person, I would consider creationism nothing less than blasphemy. Do its adherents imagine that God is a cosmic hoaxer who has created the whole vast fossil record for the sole purpose of misleading humankind?

When the Sun shrinks to a dull red dwarf, it will not be dying. It will just be starting to live and everything that has gone before will merely be a prelude to its real history.

I believe any malevolent supercivilisation would have rapidly self-destructed as we may be in the process of doing ourselves. If we do have contact, physical contact with aliens, I think it will be benign.

Space can be mapped and crossed and occupied without definable limit; but it can never be conquered.

I don't think there is such a thing as as a real prophet. You can never predict the future. We know why now, of course; chaos theory, which I got very interested in, shows you can never predict the future.

I can never look now at the Milky Way without wondering from which of those banked clouds of stars the emissaries are coming. If you will pardon so commonplace a simile, we have set off the fire alarm and have nothing to do but to wait. I do not think we will have to wait for long.