Note on earnshaw's theorem

Many have seen the “electromagnetic levitator” in the General Electric Company's “House of Magic” demonstration lectures. In this demonstration, an aluminum disk is stably supported in an alternating magnetic field under the repulsive force between the induced eddy currents and field.5 Another and related problem is reflected in several recent and serious, but inevitably (utile, attempts to achieve stable suspension in space under the forces of permanent magnets alone. This article sheds further light on the basic theory involved, which was formulated a century ago by Samuel Earnshaw and seems quite largely to have been overlooked.