Ancient bricks from Mesopotamia have helped confirm a mysterious anomaly in Earth's magnetic field that occurred 3,000 years ago, a new study finds. Brickmakers baked the bricks, which were imprinted with the names of Mesopotamian kings, between the third and first millennia B.C. Iron oxide grains within the clay recorded changes in Earth's magnetic field when the bricks were heated, enabling scientists to reconstruct changes in the magnetic field over time, the team reported in a study pub