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

The intelligent minority of this world will mark 1 January 2001 as the real beginning of the 21st century and the Third Millennium.

The universe must be full of voices, calling from star to star in a myriad tongues. One day we shall join that cosmic conversation.

In this single galaxy of ours there are eighty-seven thousand million suns. [...] In challenging it, you would be like ants attempting to label and classify all the grains of sand in all the deserts of the world. [...] It is a bitter thought, but you must face it. The planets you may one day possess. But the stars are not for man.

It is really quite amazing by what margins competent but conservative scientists and engineers can miss the mark, when they start with the preconceived idea that what they are investigating is impossible.

The Shuttle is to space flight what Lindbergh was to commercial aviation.

The space elevator will be built about 50 years after everyone stops laughing.