The earth doesn't move backward (very much) when you walk only because it's much more massive than you are.

The next question was — what makes planets go around the sun? At the time of Kepler some people answered this problem by saying that there were angels behind them beating their wings and pushing the planets around an orbit. As you will see, the answer is not very far from the truth. The only difference is that the angels sit in a different direction and their wings push inward.

In some sense, gravity does not exist; what moves the planets and the stars is the distortion of space and time.

Men knew better than they realized, when they placed the abode of the gods beyond the reach of gravity.

Only three constants are significant for star formation: the gravitational constant, the fine structure constant, and a constant that governs nuclear reaction rates.

You are ninety-eight cents' worth of cosmic star dust floating at the obscure edge of an ordinary galaxy, and yet you are the center of your own world; to friends and family, you may be precious beyond all worth. On one day, humanity seems the apex of all things beautiful, generous, mindful; another day, it seems a stupid beast.