We are compelled to drive onward; we cannot turn back. There is a fire in men that does not let them rest. And so they must go on and on, until they find something real — or perish in the attempt.

The surface of the Earth is the shore of the cosmic ocean. On this shore, we have learned most of what we know. Recently, we have waded a little out to sea, enough to dampen our toes or, at most, wet our ankles. The water seems inviting. The ocean calls.

We shall not cease from exploration, and the end of all our exploring will be to arrive where we started and know the place for the first time.

It is not the strength of the body that counts, but the strength of the spirit. The world is not in your books and maps; it is out there.

The only way to discover the limits of the possible is to go beyond them into the impossible.