A scientist naturally and inevitably ... mulls over the data and guesses at a solution. He proceeds to testing of the guess by new data-predicting the consequences of the guess and then dispassionately inquiring whether or not the predictions are verified.

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

The history of astronomy is a history of receding horizons.

Observations always involve theory.

All nature is a vast symbolism: Every material fact has sheathed within it a spiritual truth.

Not until the empirical resources are exhausted, need we pass on to the dreamy realms of speculation.

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