"Thus the explorations of space end on a note of uncertainty. And necessarily so. We are, by definition, at the very center of the observable region. We know our immediate neighborhood rather intimately. With increasing distance, our knowledge fades, and fades rapidly. Eventually, we reach the dim boundary — the utmost limits of our telescopes. There, we measure shadows, and we search among ghostly errors of measurement for landmarks that are scarcely more substantial.

"The search will continue. Not until the empirical resources are exhausted, need we pass onto the dreamy realms of speculation."