To live in the hearts of others is to never die in those we leave behind.

We can judge our progress by the courage of our questions and the depth of our answers, our willingness to embrace what is true rather than what feels good.

Scientists make mistakes. Accordingly, it is the job of the scientist to recognize our weakness, to examine the widest range of opinions, to be ruthlessly self-critical. Science is a collective enterprise with the error-correction machinery often running smoothly.

The cosmos is full beyond measure of elegant truths; of exquisite interrelationships; of the awesome machinery of nature.

Science is a way of thinking that helps you not to fool yourself.

The notion that science and spirituality are somehow mutually exclusive does a disservice to both.

I set before you two ways: You can use your technology to destroy yourselves or to carry you to the planets and the stars. It's up to you.