Billions and billions -- The Persian chessboard -- Monday-night hunters -- The gaze of God and the dripping faucet -- Four cosmic questions -- So many suns, so many worlds -- The world that came in the mail -- The environment: where does prudence lie? -- Croesus and Cassandra -- A piece of the sky is missing -- Ambush: the warming of the world -- Escape from ambush -- Religion and science: an alliance -- The common enemy -- Abortion: is it possible to be both "pro-life" and "pro-choice"? (cowritten with Ann Druyan) -- The rules of the game -- Gettyburg and now (cowritten with Ann Druyan)-- The twentieth century -- In the valley of the shadow -- Epilogue (Anne Druyan).