Researchers at the Univ. of Maryland have constructed a 30-ton sphere that spins at more than 90 mph to generate magnetic fields. The 10-ft.-dia. sphere is filled with 13.5 tons of liquid sodium to mimic the Earth’s liquid-iron center core. A 3.3-ft.- dia. stainless-steel sphere inside the larger one counterrotates to approximate the motion of the planet’s solid iron inner core. The action of Earth’s inner liquid produces a magnetic field that makes compasses work, deflects harmful cosmic rays and protects the planet from solar wind. The field reverses every couple of hundred thousand years. By using a model instead of a computer simulation, scientists hope to determine how these reversals occur and predict the next one.
However, the Three Meter Geodynamo experiment created by the Lathrop Lab is a bit of a handful. Both spheres are driven by 350-hp electric motors. At full speed the outer sphere spins at 240 rpm; the inner sphere reaches 960 rpm. The sodium used in the model is highly conductive and melts more easily than iron, but it can explode if touched by water. The lab in Maryland has no sprinklers. The corrugated half-pipes around the sphere are filled with oil, not water or steam, that heats the sodium inside to its melting point, 207.9°F.
