Diamagnetically stabilized magnet levitation

Stable levitation of one magnet by another with no energy input is usually prohibited by Earnshaw's theorem. However, the introduction of diamagnetic material at special locations can stabilize such levitation. A magnet can e ven be stably suspended between (diamagnetic) fingertips. A very simple, su rprisingly stable room temperature magnet levitation device is described th at works without superconductors and requires absolutely no energy input. O ur theory derives the magnetic field conditions necessary for stable levita tion in these cases and predicts experimental measurements of the forces re markably well. New levitation configurations are described which can be sta bilized with hollow cylinders of diamagnetic material. Measurements are pre sented of the diamagnetic properties of several samples of bismuth and grap hite. (C) 2001 American Association of Physics Teachers.