相对论不仅仅是一种科学理论；它是一种哲学理论。

Courage is the most important of all the virtues, because without courage you can't practice any other virtue consistently.

Flow is being completely involved in an activity for its own sake. The ego falls away. Time flies. Every action, movement, and thought follows inevitably from the previous one, like playing jazz. Your whole being is involved, and you're using your skills to the utmost.