My experiences with science led me to God. They challenge science to prove the existence of God. But must we really light a candle to see the sun?

Science and religion are not antagonists. On the contrary, they are sisters. While science tries to learn more about the creation, religion tries to better understand the Creator. While through science man tries to harness the forces of nature around him, through religion he tries to harness the force of nature within him.

We can lick gravity, but sometimes the paperwork is overwhelming.

The greatest gain from space travel consists in the extension of our knowledge. In a hundred years this newly won knowledge will pay huge and unexpected dividends.

Man is not made for space. But with the help of biologists and medical doctors, he can be prepared and accommodated.

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

I believe that the time has arrived for medical investigation of the problems of manned rocket flight, for it will not be the engineering problems but rather the limits of the human frame that will make the final decision as to whether manned space flight will eventually become a reality.