[Newton's calculations] entered the marrow of what we know without knowing how we know it.

All science is full of statements where you put your best face on your ignorance, where you say: ... we know awfully little about this, but more or less irrespective of the stuff we don't know about, we can make certain useful deductions.

The scientist … must always be prepared to deal with the unknown. It is an essential part of science that you should be able to describe matters in a way where you can say something without knowing everything.

The kind of lecture which I have been so kindly invited to give, and which now appears in book form, gives one a rare opportunity to allow the bees in one's bonnet to buzz even more noisily than usual.

An observer situated in a nebula and moving with the nebula will observe the same properties of the universe as any other similarly situated observer at any time.

[Science doesn't deal with facts; indeed] fact is an emotion-loaded word for which there is little place in scientific debate.

... an opportunity to allow the bees in one's bonnet to buzz even more noisily than usual.