All civilizations become either spacefaring or extinct.

Is mankind alone in the universe? Or are there somewhere other intelligent beings looking up into their night sky from very different worlds and asking the same kind of question?

Science cuts two ways, of course; its products can be used for both good and evil. But there's no turning back from science. The early warnings about technological dangers also come from science.

Perhaps the depth of love can be calibrated by the number of different selves that are actively involved in a given relationship.

We invest far off places with a certain romance... Long summers, mild winters, rich harvests, plentiful game; none of them lasts for ever. Your own life, or your bands, or even your species - might be owed to a restless few, drawn by a craving they can hardly articulate or understand, to undiscovered lands, and new worlds.

There are in fact 100 billion galaxies, each of which contain something like a 100 billion stars. Think of how many stars, and planets, and kinds of life there may be in this vast and awesome universe.

The universe is not required to be in perfect harmony with human ambition.