Put it in the category of invisible but vital: The magnetic field that envelops the Earth shields life from harmful ions spat out by the sun. Although unseen, it’s not undetectable (try a compass); auroras displayed when geomagnetic storms hit the polar regions hint at its presence. Our magnetic field has protected us for eons, its existence recorded in minute crystals hidden in ancient rocks.
Scientists believe that this magnetic field originates in the roiling of iron and dancing of electrons within the metallic soup of the Earth’s core. But exactly how that magnetism mechanism works has been a hard question to answer. From decades of study, geophysicists have pieced together a general picture of the process: The cooling of the planet’s solid inner core stirs up the liquid iron in the outer core. This movement creates electric currents, which