Spin-stabilized magnetic levitation

A brief demonstration and small explanation about the Levitron levitating top device which demonstrates spin-stabilized magnetic levitation.

Spin-stabilized magnetic levitation is a phenomenon of magnetic levitation where a magnet is levitated via magnetic forces above another magnet or array of magnets, and stabilised by gyroscopic effect due to a spin that is neither too fast, nor too slow.

The phenomenon was originally discovered through invention by Vermont inventor Roy M. Harrigan in the late 1970s. A Delaware inventor named Joseph Chieffo who was not previously aware of Harrigan's invention made the same discovery in 1984 (using a somewhat different device configuration from Harrigan's).^[1][2] Harrigan received a United States patent for his original levitation device based upon this phenomenon on May 3, 1983.^[3][4] A spin-stabilized magnetic levitation device entirely based upon Harrigan's discovery is marketed as a science toy under the trademark brand name, 'Levitron'.

Physics

Earnshaw's theorem does not allow for a static configuration of permanent magnets to stably levitate another permanent magnet or materials that are paramagnetic or ferromagnetic against gravity. This theorem does not apply to devices consisting of a properly configured magnetic base and corresponding top, however, because the non-static nature of the spinning top acts as a gyroscope to prevent its magnetic field from aligning itself in the same direction as that of the primary field of the magnetic base (i.e.: via the top flipping). This gyroscopic property combined with the top's precession allows it to respond dynamically to the direction of the local toroidally shaped field of its base magnet and remain levitating about a central point in space above the base where the forces acting on the top (gravitational, magnetic, and gyroscopic) are in equilibrium thereby allowing the top to rest in an energy minima well.^[5] (see: magnetic levitation)

In the laboratory, experimental setups are able to levitate tops for indefinite periods by measuring the spin rate and maintaining it using a drive coil. However, variations in temperature can affect the stability, and without ambient temperature control the top will eventually fall after hours or days due to the temperature coefficient of the magnets.^[5]

The physics of the magnetic stability is similar to magnetic gradient traps.^[5]

References

1. ^ Rod Driver (1999-09-22). "An amazing invention, and a patent failure (Part 1 of 2)". The Providence Journal. Archived from the original on 2001-03-06. http://www.roddriver.com/science_990922.html. 
2. ^ Rod Driver (1999-09-23). "The patent that failed its invention (Part 2 of 2)". The Providence Journal. Archived from the original on 2001-03-06. http://www.roddriver.com/science_990923.html. 
3. ^ U.S. Patent 4,382,245
4. ^ Theodore Gray. "Ignorance = Maglev = Bliss". How2.0. Popular Science. http://www.popsci.com/popsci/how20/be199aa138b84010vgnvcm1000004eecbccdrcrd.html. Retrieved 2007-03-26. "This spinning top, which hovers above a magnetic base, was patented in 1983 by a Vermonter named Roy Harrigan." 
5. ^ ^{a b c} Martin D. Simon, UCLA Department of Physics, Lee O. Heflinger, S. L. Ridgway (1997). "Spin stabilized magnetic levitation". American Journal of Physics. http://www.physics.ucla.edu/marty/levitron/. Retrieved 2006-12-06.