Niels Bohr, 1927: "Anyone who is not shocked by quantum theory does not understand it."
Richard Feynman, 1967: "Nobody understands quantum theory."
And since we're on the subject of the world being "not only stranger than we know, but stranger than we can know" (which scientist said this?? I remember reading it in a popular science book, but can't remember where or who??) ...
... not strictly regarding quantum physics, but since we're on the subject of human understanding and the subjectivity of perception, one of my very favourite quotes :
"... Einstein’s space is no closer to reality than Van Gogh’s sky. The glory of science is not in a truth more absolute than the truth of Bach or Tolstoy, but in the act of creation itself. The scientist’s discoveries impose his own order on chaos, as the composer or painter imposes his; an order that always refers to limited aspects of reality, and is based on the observer’s frame of reference, which differs from period to period as a Rembrandt nude differs from a nude by Manet." - Arthur Koestler
As a student of the history of science, I find scientific methodology so interesting ... from 'science fiction' to hypotheses to theories, always based on evidence ... so we've got the imagination, and the observations, combined ...
And regarding another of my favourite physics subjects, time, the great Douglas Adams' quote: "Time is an illusion. Lunchtime doubly so."
