Abracadabra! Magnets float in midair.
Physicists had never before achieved stationary levitation of a magnet without using superconductors (SN: 8/6/88, p. 86). A 157-year-old principle known as Earnshaw's theorem stipulates that no arrangement of magnets can make them stay in a stable equilibrium, says Andre K. Geim of the University of Nijmegen in the Netherlands. The slightest disturbance would cause one magnet to leap toward another or fall away.
Geim and his colleagues, however, learned that certain materials can stabilize a magnet that is being levitated by another. These so-called diamagnetic materials have no permanent magnetic character but generate magnetism that opposes an applied magnetic field. Superconductors are the strongest diamagnets, and many ordinary materials are weakly diamagnetic (SN: 12/6/97, p. 362).
A pair of well-placed fingers--made up of diamagnetic water, proteins, and organic molecules--is enough to do the trick. "The real surprise is that such weak repulsive forces are still enough to stabilize the magnet, preventing it from falling down or moving upward," says Geim. He and his colleagues report their finding in the July 22 NATURE.
This type of levitation could be used to make frictionless bearings for trains or energy-storage devices such as flywheels, says Geim. To illustrate the principle, his collaborator Martin D. Simon of the University of California, Los Angeles has assembled a handheld version of the levitator using permanent magnets and graphite plates.
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|Article Type:||Brief Article|
|Date:||Jul 24, 1999|
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