But Chris Chyba of Princeton University and Kevin Hand of the Jet Propulsion Laboratory in Pasadena, California, saw a way forward. This principle seems to squelch any idea that a stationary device on the Earth’s surface, moving at constant velocity through the nonrotating part of the Earth’s field, could generate any electric power. Equilibrium between the electric and magnetic forces is quickly established, so there is no net motion of charge following the small, initial rearrangement. But the displacements of the electrons and atomic nuclei quickly set up a static electric field that opposes the magnetic force. Charges within the material experience a sideways force that could, in principle, produce current. Any stationary object on the Earth’s surface sweeps through this component of the field, which is constant at any given latitude.Īnother basic result from electromagnetism says that no electric current will develop within a conducting object moving through a uniform magnetic field. There is a component of the Earth’s magnetic field that is symmetric around the rotation axis (which is not aligned with the magnetic poles), so according to this old principle, the axisymmetric component does not rotate. The power from the proposed device would be measured in nanowatts, but might, in principle, be scaled up.Ī century-old experiment showed that if any electromagnet with cylindrical symmetry (the symmetry of a bar magnet) rotates about its long axis, its magnetic field does not rotate.

They show theoretically that a device, sitting passively on the Earth’s surface, can generate an electric current through its interaction with the Earth’s magnetic field. It might seem that classical electromagnetic theory would hold few surprises, but two researchers argue that one aspect of received wisdom is wrong. A proposed device interacting with this component would extract energy from the Earth’s rotation to produce electric power. Although the Earth’s magnetic field is not aligned exactly with the planet’s rotation axis, there is a component of the field that is symmetric about this axis. of Edinburgh Tapping into Earth’s rotation.

Magnetic field around the earth