Cosmos, the book by Carl Sagan, does something remarkable. It starts in a distant part of the universe. It does a slow zoom, through desolate space, through groups of galaxies, through the Milky Way, through a remote arm of the Milky Way, through the solar system, past the most distant plants, finally into Earth. It shows us as a tiny note of dust in an obscure part of the universe.

Then, it moves to one of the early civilizations, in Alexandria. To Alexander’s ideals of learning, his great library. It shows how, at that time, Earth was vast, unknown, many parts a mental blank. And it traces the change from that blankness to continents being connected within a human life span. Civilizations becoming known to one other. Until, finally, there are no unknown parts of Earth. No unknown continents or peoples. The rest of Earth was once other, but now it’s us.

The book returns to the question of space. Vast, unknown. Just like Earth once was.