I have learned to use the word 'impossible' with the greatest caution.

In 1492 Columbus knew less about the far Atlantic than we do about the heavens, yet he chose not to sail with a flotilla of less than three ships. . . . So it is with interplanetary exploration: it must be done on the grand scale.

Don't tell me that man doesn't belong out there. Man belongs wherever he wants to go - and he'll do plenty well when he gets there.

What we will have attained when Neil Armstrong steps down upon the moon is a completely new step in the evolution of man.

It takes sixty-five thousand errors before you are qualified to make a rocket.

Science does not have a moral dimension. It is like a knife. If you give it to a surgeon or a murderer, each will use it differently.

It was very successful, but it fell on the wrong planet.