The 3-metre-tall ribbed sphere looks like a 'visitor' from another planet, dramatically lit and encased within a sturdy steel box. In fact, the giant orb, housed in a cavernous warehouse at the University of Maryland, College Park, is meant to approximate Earth's core.

Ten years in the making, the US$2-million project is nearly ready for its inaugural run. Early next year, the sphere will begin whirling around while loaded with 13,000 kilograms of molten sodium heated to around 105 °C. Researchers hope that the churning, electrically conducting fluid will generate a self-sustaining electromagnetic field that can be poked, prodded and coaxed for clues about Earth's dynamo, which is generated by the movement of liquid iron in the outer core. If it works, it will be the first time that an experiment that mirrors the configuration of Earth's interior has managed to recreate such a phenomenon.