Eratosthenes's only tools were sticks, eyes, feet, and brains; plus a zest for experiment. With those tools he correctly deduced the circumference of the Earth, to high precision, with an error of only a few percent. That's pretty good figuring for 2200 years ago.

By exploring other worlds we safeguard this one. By itself, I think this fact more than justifies the money our species has spent in sending ships to other worlds. It is our fate to live during one of the most perilous and, at the same time, one of the most hopeful chapters in human history.

We are the product of 4.5 billion years of fortuitous, slow biological evolution. There is no reason to think that the evolutionary process has stopped. Man is a transitional animal. He is not the climax of creation.

Your god is too small for my universe.

It is far better to grasp the universe as it really is than to persist in delusion, however satisfying and reassuring.

Nature does not always conform to our predispositions and preferences, to what we deem comfortable and easy to understand.

The sacred truth of science is that there are no sacred truths.