Galileo had already made a significant beginning toward a knowledge of the law of motion. He discovered the law of inertia and the law of bodies falling freely in the gravitational field of the earth.

About Newton: Nature to him was an open book, whose letters he could read without effort.

In their struggle for the ethical good, teachers of religion must have the stature to give up the doctrine of a personal god, that is, give up that source of fear and hope which in the past placed such vast power in the hands of priests. In their labors they will have to avail themselves of those forces which are capable of cultivating the Good, the True, and the Beautiful in humanity itself. This is, to be sure, a more difficult but an incomparably more worthy task.

I think and think for months and years. Ninety-nine times, the conclusion is false. The hundredth time I am right.

Watch the stars, and from them learn.

God has given me a mule-like stubbornness to stick with a difficult problem and the intuitive powers to conceptualize complex hypothetical situations in my mind.

I don't know what weapons will be used in the Third World War. But I can tell you what they'll use in the Fourth - rocks!