The relativity principle in connection with the basic Maxwellian equations demands that the mass should be a direct measure of the energy contained in a body; light transfers mass. With radium there should be a noticeable diminution of mass. The idea is amusing and enticing; but whether the Almighty is laughing at it and is leading me up the garden path -- that I cannot know.

If you can't explain something simply, you don't know enough about it.

Understanding of our fellow human beings...becomes fruitful only when it is sustained by sympathetic feelings in joy and sorrow.

We have to do the best we are capable of. This is our sacred human responsibility.

Empathy is patiently and sincerely seeing the world through the other person's eyes. It is not learned in school; it is cultivated over a lifetime.

I no longer believed in the known God of the Bible, but rather in the mysterious God expressed in nature.

The comprehensibility of the world seems to me a wonder or eternal secret. Here lies the sense of wonder which increases even more with the development of our knowledge.