Only realistic flight schedules should be proposed, schedules that have a reasonable chance of being met. If in this way the government would not support them, then so be it. NASA owes it to the citizens from whom it asks support to be frank, honest, and informative.

I don't feel frightened by not knowing things, by being lost in the mysterious universe without any purpose - which is the way it really is, as far as I can tell. Possibly. It doesn't frighten me.

We never are definitely right, we can only be sure we are wrong.

I am going to tell you what nature behaves like. If you will simply admit that maybe she does behave like this, you will find her a delightful, entrancing thing. Do not keep saying to yourself, if you can possibly avoid it, 'But how can it be like that?' ...Nobody knows how it can be like that.

A poet once said, "The whole universe is in a glass of wine." We will probably never know in what sense he meant that, for poets do not write to be understood. But it is true that if we look at a glass of wine closely enough we see the entire universe.

All we know so far is what doesn't work.

Science is like sex: sometimes something useful comes out, but that is not the reason we are doing it