We seem gradually to be groping toward an understanding of the world of subatomic particles, but we really do not know how far we have yet to go in this task.

The philosophical question before us is, when we make an observation of our track in the past, does the result of our observation become real in the same sense that the final state would be defined if an outside observer were to make the observation?

If we have an atom that is in an excited state and so is going to emit a photon, we cannot say when it will emit the photon. It has a certain amplitude to emit the photon at any time, and we can predict only a probability for emission; we cannot predict the future exactly.

In talking about the impact of ideas in one field on ideas in another field, one is always apt to make a fool of oneself.

Grades can matter, especially for those students and parents who live for the next round of applications to graduate or professional schools. But there's a problem with the grade emphasis. Math or science graduates earn more than students majoring in the humanities.

I am now convinced that theoretical physics is actually philosophy.

Gold and silver are no doubt subject to fluctuations, from the discovery of new and more abundant mines; but such discoveries are rare, and their effects, though powerful, are limited to periods of comparatively short duration.

An important scientific innovation rarely makes its way by gradually winning over and converting its opponents: What does happen is that the opponents gradually die out.