This unusual device is a laboratory model of Earth’s core. The experiment aims to study the self-generation of magnetic fields as occurs in the geodynamo. The temperature of Earth’s iron core precludes ferromagnetism; our planetary field instead comes from induction, analogous to processes converting mechanical motions to electric currents in an electric generator. Yet deep mysteries remain about the structure and dynamics of Earth’s magnetic field. The need to understand it is driving experimental efforts worldwide (see the article on page 40), including this 3-meter-diameter model dynamo at the University of Maryland.
Shown here is the outer spherical vessel, whose temperature-regulating jacket gives it a ribbed appearance. Inside is a 1-meter-diameter sphere that simulates Earth’s solid inner core. Both spheres rapidly rotate (see http://www.youtube.com/user/n3umh), but the more hazardous aspect is the 12 tons of liquid sodium that will fill the intervening space to model the liquid iron of...
