Magnetometer using superconducting rotating body

A method and apparatus for measuring the strength and direction of an unknown magnetic field are disclosed. A freely rotatable suspended superconducting body, such as a sphere, is maintained at a superconducting temperature. A magnetic field to be measured induces super current flow on the sphere's surface. The induced current causes the sphere to rotate at a rate that is proportional to the strength of the field, and the axis of rotation of the sphere aligns with the direction of the magnetic field to be measured. An operator applies current to orthogonal electromagnetic coils arranged relative to the sphere so as to apply variable magnetic fields to the sphere. Varying the current and the resulting fields nulls out the effect of the magnetic field to be measured; measurement of the nulling currents indicate the direction and strength of the unknown magnetic field.