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

To the pure geometer the radius of curvature is an incidental characteristic - like the grin of the Cheshire cat. To the physicist it is an indispensable characteristic. It would be going too far to say that to the physicist the cat is merely incidental to the grin. Physics is concerned with interrelatedness such as the interrelatedness of cats and grins. In this case the "cat without a grin" and the "grin without a cat" are equally set aside as purely mathematical phantasies.

Something unknown is doing we don't know what-that is what our theory amounts to.

It is reasonable to hope that in the not too distant future we shall be competent to understand so simple a thing as a star.

Whatever else there may be in our nature, responsibility toward truth is one of its attributes.

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 pursuit of truth in science transcends national boundaries. It takes us beyond hatred and anger and fear. It is the best of us.