National Geographic News, Reporting Your World Daily

Thursday, October 28, 2010

Photo: Magnetic Field Weakening in Stages, Old Ships' Logs Suggest


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A 15th-century nautical compass sits on display in the Canary Islands. New analysis of compass data from old ships' logs shows that Earth's magnetic field has been weakening in staggered steps and not in a continuous decline.

Photograph by Victor R. Boswell, Jr./NGS