Equipped with his five senses, man explores the universe around him and calls the adventure Science.

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 on to the dreamy realms of speculation.

The history of astronomy is a history of receding horizons.

Wisdom cannot be directly transmitted, and does not readily accumulate through the ages.

Astronomy is something like the ministry. No one should go into it without a call. I got that unmistakable call, and I know that even if I were second-rate or third-rate, it was astronomy that mattered.

The great spirals, with their enormous radial velocities and insensible proper motions, apparently lie outside our Solar system.

The great spirals... apparently lie outside our stellar system.