It is a mistake to think of creative activity as something unusual

The world can only be grasped by action, not by contemplation.

[John] Dalton was a man of regular habits. For fifty-seven years he walked out of Manchester every day; he measured the rainfall, the temperature-a singularly monotonous enterprise in this climate. Of all that mass of data, nothing whatever came. But of the one searching, almost childlike question about the weights that enter the construction of these simple molecules-out of that came modern atomic theory. That is the essence of science: ask an impertinent question, and you are on the way to the pertinent answer.

We gain our ends only with the laws of nature; we control her only by understanding her laws.

One original thought is worth the sum total of human knowledge, because it advances the sum total of human knowledge by that one original thought.

Knowledge is an unending adventure at the edge of uncertainty.

Astronomy is not the apex of science or of invention. But it is a test of the cast of temperament and mind that underlies a culture.