Every body continues in its state of rest or uniform motion in a straight line, except insofar as it doesn't.

We often think that when we have completed our study of one we know all about two, because 'two' is 'one and one.' We forget that we still have to make a study of 'and.'

In Einstein's theory of relativity the observer is a man who sets out in quest of truth armed with a measuring-rod. In quantum theory he sets out with a sieve.

I ask you to look both ways. For the road to a knowledge of the stars leads through the atom; and important knowledge of the atom has been reached through the stars.

The word reality frightens me.

It is impossible to trap modern physics into predicting anything with perfect determinism because it deals with probabilities from the outset.

Electrical force is defined as something which causes motion of electrical charge; an electrical charge is something which exerts electric force.