magnetic field (origin of the Earth's internal field) Although most of us have used a magnetic compass to orient ourselves, we do not often think in terms of the source of the energy that powers the compass needle. This energy is provided by the Earth's magnetic field. The origin of the field is a complex subject which has enthralled a large number of the best scientists for the past four centuries; Albert Einstein even referred to it once as one of the three most important unsolved problems in physics. Certain aspects of how the field is generated are, however, now fairly well understood. Earth's magnetic field originates in the fluid outer core and is generated by electrical ...