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.

But it is necessary to insist more strongly than usual that what I am putting before you is a model-the Bohr model atom-because later I shall take you to a profounder level of representation in which the electron instead of being confined to a particular locality is distributed in a sort of probability haze all over the atom.

You cannot disturb the tiniest petal of a flower without the troubling of a distant star.

Our ultimate analysis of space leads us not to a "here" and a "there," but to an extension such as that which relates "here" and "there." To put the conclusion rather crudely-space is not a lot of points close together; it is a lot of distances interlocked.

What we makes of the world must be largely dependent on the sense-organs that we happen to possess. How the world must have changed since the man came to rely on his eyes rather than his nose.

Science is one thing, wisdom is another. Science is an edged tool, with which men play like children, and cut their own fingers.

In any attempt to bridge the domains of experience belonging to the spiritual and physical sides of nature, time occupies the key position.