Electrostatic Levitation of a Titanium-Zirconium-Nickel Alloy

Electrostatic levitation is the process of using an

electric field An electric field (sometimes E-field) is the physical field that surrounds electrically charged particles and exerts force on all other charged particles in the field, either attracting or repelling them. It also refers to the physical field fo ...

levitate Levitation (from Latin ''levitas'' "lightness") is the process by which an object is held aloft in a stable position, without mechanical support via any physical contact. Levitation is accomplished by providing an upward force that counteracts ...

a charged object and counteract the effects of

gravity In physics, gravity () is a fundamental interaction which causes mutual attraction between all things with mass or energy. Gravity is, by far, the weakest of the four fundamental interactions, approximately 1038 times weaker than the stro ...

. It was used, for instance, in

Robert Millikan Robert Andrews Millikan (March 22, 1868 – December 19, 1953) was an American experimental physicist honored with the Nobel Prize for Physics in 1923 for the measurement of the elementary electric charge and for his work on the photoelectric e ...

oil drop experiment The oil drop experiment was performed by Robert A. Millikan and Harvey Fletcher in 1909 to measure the elementary electric charge (the charge of the electron). The experiment took place in the Ryerson Physical Laboratory at the University of Chi ...

and is used to suspend the gyroscopes in

Gravity Probe B Gravity Probe B (GP-B) was a satellite-based experiment to test two unverified predictions of general relativity: the geodetic effect and frame-dragging. This was to be accomplished by measuring, very precisely, tiny changes in the direction of ...

during launch. Due to Earnshaw's theorem, no static arrangement of classical electrostatic fields can be used to stably levitate a point charge. There is an equilibrium point where the two fields cancel, but it is an

unstable equilibrium In mathematics, in the theory of differential equations and dynamical systems, a particular stationary or quasistationary solution to a nonlinear system is called linearly unstable if the linearization of the equation at this solution has the form ...

. By using

feedback Feedback occurs when outputs of a system are routed back as inputs as part of a chain of cause-and-effect that forms a circuit or loop. The system can then be said to ''feed back'' into itself. The notion of cause-and-effect has to be handled ...

techniques it is possible to adjust the charges to achieve a quasi static levitation.

Earnshaw's theorem

The idea of particle instability in an electrostatic field originated with

Samuel Earnshaw Samuel Earnshaw (1 February 1805, Sheffield, Yorkshire – 6 December 1888, Sheffield, Yorkshire) was an English clergyman and mathematician and physicist, noted for his contributions to theoretical physics, especially " Earnshaw's theorem". ...

in 1839 and was formalized by

James Clerk Maxwell James Clerk Maxwell (13 June 1831 – 5 November 1879) was a Scottish mathematician and scientist responsible for the classical theory of electromagnetic radiation, which was the first theory to describe electricity, magnetism and ligh ...

in 1874 who gave it the title "Earnshaw's theorem" and proved it with the

Laplace equation In mathematics and physics, Laplace's equation is a second-order partial differential equation named after Pierre-Simon Laplace, who first studied its properties. This is often written as \nabla^2\! f = 0 or \Delta f = 0, where \Delta = \nab ...

. Earnshaw's theorem explains why a system of electrons is not stable and was invoked by

Niels Bohr Niels Henrik David Bohr (; 7 October 1885 – 18 November 1962) was a Danish physicist who made foundational contributions to understanding atomic structure and quantum theory, for which he received the Nobel Prize in Physics in 1922. B ...

in his atom model of 1913 when criticizing J. J. Thomson's atom. 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. Since the forces remain in balance, there is no inequality to provide a restoring force; and the particle remains unstable and can freely move without restriction.

Levitation

The first electrostatic levitator was invented by Dr. Won-Kyu Rhim at

NASA The National Aeronautics and Space Administration (NASA ) is an independent agency of the US federal government responsible for the civil space program, aeronautics research, and space research. NASA was established in 1958, succeeding t ...

's JPL lab in 1993.W. K. Rhim, S. K. Chung, D. Barber, K. F. Man, G. Gutt, A. Rulison, and R. E. Spjut, Review of Scientific Instruments 64, 2961 (1993). 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. The field is controlled through a feedback system to keep the levitated sample at a predetermined position. Several copies of this system have been made in

JAXA The is the Japanese national air and space agency. Through the merger of three previously independent organizations, JAXA was formed on 1 October 2003. JAXA is responsible for research, technology development and launch of satellites into orb ...

and NASA, and the original system has been transferred to

California Institute of Technology The California Institute of Technology (branded as Caltech or CIT)The university itself only spells its short form as "Caltech"; the institution considers other spellings such a"Cal Tech" and "CalTech" incorrect. The institute is also occasional ...

with an upgraded setup of tetrahedra four beam laser heating system. On the Moon the

photoelectric effect The photoelectric effect is the emission of electrons when electromagnetic radiation, such as light, hits a material. Electrons emitted in this manner are called photoelectrons. The phenomenon is studied in condensed matter physics, and solid st ...

and electrons in the

solar wind The solar wind is a stream of charged particles released from the upper atmosphere of the Sun, called the corona. This plasma mostly consists of electrons, protons and alpha particles with kinetic energy between . The composition of the sola ...

charge fine layers of

moon dust Lunar soil is the fine fraction of the regolith found on the surface of the Moon. Its properties can differ significantly from those of terrestrial soil. The physical properties of lunar soil are primarily the result of mechanical disintegra ...

on the surface forming an atmosphere of dust that floats in "fountains" over the surface of the moon.Bell, Trudy E., "Moon fountains"
FirstScience.com, 2001-01-06.
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References

External links

JLN Labs: Levitators

Electrostatic levitator — Marshall Space Flight Center

* ttp://www.nasatech.com/Briefs/Mar99/NPO20165.html Hybrid electric/acoustic levitation
Electrostatic levitation and transportation of glass or silicon plates

{{DEFAULTSORT:Electrostatic Levitation Electrostatics Levitation

Earnshaw's theorem

Levitation

See also

References

External links