Electrostatic levitation

It was used, for instance, in Robert Millikan's oil drop experiment and is used to suspend the gyroscopes in Gravity Probe B during launch.

Due to Earnshaw's theorem, no static arrangement of classical electrostatic fields can be used to stably levitate a point charge.

Earnshaw's theorem holds that a charged particle suspended in an electrostatic field is unstable, because the forces of attraction and repulsion vary at an equal rate that is proportional to the inverse square law and remain in balance wherever a particle moves.

The first electrostatic levitator was invented by Dr. Won-Kyu Rhim at NASA's Jet Propulsion Laboratory in 1993.

[4] A charged sample of 2 mm in diameter can be levitated in a vacuum chamber between two electrodes positioned vertically with an electrostatic field in between.