If I finish a book a week, I will read only a few thousand books in my lifetime, about a tenth of a percent of the contents of the greatest libraries of our time. The trick is to know which books to read.

Even through your hardest days, remember we are all made of stardust.

The near side of a galaxy is tens of thousands of light-years closer to us than the far side; thus we see the front as it was tens of thousands of years before the back. But typical events in galactic dynamics occupy tens of millions of years, so the error in thinking of an image of a galaxy as frozen in one moment of time is small.

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.

Our ancestors lived out of doors. They were as familiar with the night sky as most of us are with our favorite television programs.

I promise to question everything my leaders tell me. I promise to use my critical faculties. I promise to develop my independence of thought. I promise to educate myself so I can make my own judgments.

In many cultures it is customary to answer that God created the universe out of nothing. But this is mere temporizing. If we wish courageously to pursue the question, we must, of course ask next where God comes from? And if we decide this to be unanswerable, why not save a step and conclude that the universe has always existed?