I put up my thumb and it blotted out the planet Earth.

It's a great thing for a man to walk on the moon. But it's a greater thing for God to walk on the earth.

I suspect that even though the various questions are difficult and many, they are not as difficult and many as those we faced when we started the Apollo [space program] in 1961.

Good luck, Mr. Gorsky!

The single thing which makes any man happiest is the realization that he has worked up to the limits of his ability, his capacity. It's all the better, of course, if this work has made a contribution to knowledge, or toward moving the human race a little farther forward.

Pilots take no special joy in walking: pilots like flying.

Geologists have a saying - rocks remember.