The ability of magnets to exert forces on one another without touching intrigues most children—and more than a few adults. It is a short step from pondering this curious phenomenon to wondering whether the force from one magnet could be used to levitate another, seemingly in defiance of gravity. Unfortunately, as any frustrated would-be levitator has discovered, the answer is no: A magnetic field can be arranged so that at some position it just balances the gravitational force on a small magnet, but any disturbance to the levitated magnet, no matter how tiny, causes it to crash. This inherent lack of stability is summed up in a statement of physical law known as Earnshaw's Theorem, first elucidated in 1842. It is a direct consequence of Maxwell's fundamental equations describing electricity and magnetism.
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