Earth's magnetic field is weakening — magnetic crystals from lost civilizations could hold the key to understanding why

An illustration of a piece of pottery with magnetic field lines radiating from it.

In 2008, Erez Ben-Yosef unearthed a piece of Iron Age "trash" and inadvertently revealed the strongest magnetic-field anomaly ever found.

Ben-Yosef, an archaeologist at Tel Aviv University, had been working in southern Jordan with Ron Shaar, who was analyzing archaeological materials around the Levant. Shaar, a geologist at The Hebrew University of Jerusalem, was building a record of the area's magnetic field.