Giraudon/Art Resource, NY

Tied to the mast of his ship, Odysseus listens spellbound to the song of the Sirens in this third-century A.D. mosaic from Dougga, Tunisia. To resist the seductive song, Homer’s hero orders his crew to bind him to the mast and to stop their own ears with wax.

Odysseus’s voyages throughout the Mediterranean suggest that ancient mariners boldly sailed the high seas—rather than hugging the coast, as once was thought. In recent decades, with the development of new technologies, Phoenician and Roman shipwrecks have indeed been found in the deepest waters of the Mediterranean far from the nearest shores. How did ancient mariners navigate the open sea, without compasses or charts? Homer himself provides a clue: The sorceress Calypso advises Odysseus to steer by “the Pleides and late-setting Boötes” (Odyssey 5.272)—that is, to set his course by the stars.