爱惜生命，就别浪费时光，因为生命是由时间堆砌而成。

Your smarts will come in handy because you will travel in a land of marvels. We humans -- plodding as we are -- will astonish ourselves. We'll invent ways to generate clean energy and a lot of it. Atom by atom， we'll assemble tiny machines that will enter cell walls and make repairs. This month comes the extraordinary but also inevitable news that we've synthesized life. In the coming years， we'll not only synthesize it， but we'll engineer it to specifications. I believe you'll even see us understand the human brain. Jules Verne， Mark Twain， Galileo， Newton -- all the curious from the ages would have wanted to be alive most of all right now. As a civilization， we will have so many gifts， just as you as individuals have so many individual gifts as you sit before me.

Three grand essentials to happiness in this life are something to do, something to love, and something to hope for.

The alternation of motion is ever proportional to the motive force impressed; and is made in the direction of the right line in which that force is impressed.