Time has no independent existence apart from the order of events by which we measure it.

If you can't explain what you are doing to a nine-year-old, then either you still don't understand it very well, or it's not all that worthwile in the first place.

When you sit with a nice girl for two hours, it seems like two minutes; when you sit on a hot stove for two minutes, it seems like two hours. That's relativity.

Watch the stars, and from them learn.

I urge a willingness to reserve a place in rational science for non-rational wonder.

I am a determinist. As such, I do not believe in free will...Practically, I am, nevertheless, compelled to act as if freedom of the will existed. If I wish to live in a civilized community, I must act as if man is a responsible being.

But if the longing for the achievement of the goal is powerfully alive within us, then shall we not lack the strength to find the means for reaching the goal and for translating it into deeds.