For thousands of years in the Marshall Islands, sailors successfully navigated across thousands of miles across open ocean in stick canoes in ways that baffle the best scientific minds on earth. They did this by studying the effects of waves on islands that might be far over the horizon. If you knew what to look for, you could detect incredibly subtle changes in waves distant islands created—blocking swells, counterswells, the refraction of swells as they encountered undersea island slopes, and the bending of swells around islands as they ran into swells coming from the opposite direction. They would map these with “stick charts” that look like poorly executed dream catchers your child might bring home from summer camp. These were made of coconut frond ribs and twine, with cowry shells tied in that represented islands. A sailor didn’t take the stick map with him to sea. He memorized it and left it behind.