Observation always involves theory.

Science is the one human activity that is truly progressive. The body of positive knowledge is transmitted from generation to generation.

Observations always involve theory.

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

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.

There we measure shadows, and we search among ghostly errors of measurement for landmarks that are scarcely more substantial.

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