As ships explored the world from the Age of Sail through 20th century, mariners kept detailed navigation records using the Sun and stars. Scientists scoured these ship logs, many of which are preserved in European libraries, for clues about Earth’s magnetic field. The work, published in 2000, created the first-ever magnetic field map for the past four centuries.

Third Pod spoke with the historian who launched the project about the trials and tribulations of turning historical measurements into cutting-edge scientific data. Along the way, Nanci Bompey learns about sea shanties.

This episode was produced by Jenessa Duncombe and mixed by Kayla Surrey.

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