When you finally understand the universe, it will not only be stranger than you imagine, it will be stranger than you can imagine.

I'm sure we would not have had men on the Moon if it had not been for Wells and Verne and the people who write about this and made people think about it. I'm rather proud of the fact that I know several astronauts who became astronauts through reading my books.

If an elderly but distinguished scientist says that something is possible, he is almost certainly right; but if he says that it is impossible, he is very probably wrong.

It is not easy to see how the more extreme forms of nationalism can long survive when men have seen the Earth in its true perspective as a single small globe against the stars.

Good morning, Dr. Chandra. This is Hal. I am ready for my first lesson.

God said, 'Cancel Program GENESIS.' The universe ceased to exist.

Perhaps no other year before or since 1984 has been awaited with such eager anticipation.