In the spring of 1900, sponge divers working off the small Greek island of Antikythera located a Roman-era shipwreck at a depth of roughly 45 meters. The ship, dated to around 70–60 BC, had been carrying a cargo of luxury goods likely bound for Rome. Among the recovered items was a corroded lump of bronze, broken into several pieces, that initially drew little attention. It sat in the National Archaeological Museum in Athens for years, cataloged but not understood.

Wet and shivering, I rose from the outrigger of a Polynesian voyaging canoe. We’d been at sea all afternoon and most of the night. I’d hoped to get a little rest, but rain, wind and an absence of flat space made sleep impossible. My companions didn’t even try.