I suddenly remember being about seven, riding beside him in the car, and asking him how grown-ups found their way to places. After all, I had never seen him pull out a map."I guess we just get used to taking the same turns," he said, but I wasn't satisfied."Then what about the first time you go somewhere?""Well," he said, "we get directions."But what I want to know is who got them the very first time? What if no one's ever been where you're going? "Dad?" I ask, "is it true that you can use stars like a map?""Yeah, if you understand celestial navigation.""Is it hard?" I'm thinking maybe I should learn. A backup plan, for all those times I feel like I'm just wandering in circles."It's pretty jazzy math—you have to measure the altitude of a star, figure out its position using a nautical almanac, figure out what you think the altitude should be and what direction the star should be in based on where you think you are, and compare the altitude you measured with the one you calculated. Then you plot this on a chart, as a line of position. You get several lines of position to cross, and that's where you go." My father takes one look at my face and smiles. "Exactly," he laughs. "Never leave home without your GPS.
