Elara set down her quill. The line was perfect, invisible except for the ink. “No, Leo. A meridian is a promise. It says: you are not lost. You are somewhere. And from this line, all other lines make sense. ”

“I drew it,” she said. “Right through the ship’s log. I named it the Meridian of Last Hope.”

“What did you do?” Leo asked.

Leo stared at her new Prime Meridian—the one she was drawing now for the King’s own atlas. “So a meridian is just a story we agree to follow?”

And that, Elara would have said, is the whole truth of longitude meridians: they are imaginary lines we choose to be real, so that we may find our way home.