"That which is not measurable is not science. — also attributed to Lord Kelvin"

“Don't let me catch anyone talking about the Universe in my department.”

“It was quite the most incredible event that has ever happened to me in my life. It was almost as incredible as if you fired a 15-inch shell at a piece of tissue paper and it came back and hit you.”

“The first point that arises is the atom. I was brought up to look at the atom as a nice hard fellow, red or grey in colour, according to taste. In order to explain the facts, however, the atom cannot be regarded as a sphere of material, but rather as a sort of wave motion of a peculiar kind. The theory of wave-mechanics, however bizarre it may appear... has the astonishing virtue that it works, and works in detail, so that it is now possible to understand and explain things which looked almost impossible in earlier days. One of the problems encountered is the relation between the electron, an atom and the radiation produced by them jointly; the new mechanics states the type of radiation emitted with correct numerical relations. When applied to the periodic table, a competent and laborious mathematician can predict the periodic law from first principles.”

“I have broken the machine and touched the ghost of matter.”

“Radioactivity is shown to be accompanied by chemical changes in which new types of matter are being continually produced. … The conclusion is drawn that these chemical changes must be sub-atomic in character.”

“An alleged scientific discovery has no merit unless it can be explained to a barmaid.”