Editing Levitron (section)

==The top device==
{{Main|Spin-stabilized magnetic levitation}}
The toy top is essentially a [[permanent magnet]]ic ring and corresponding magnetic base plate with a ring or ring shaped magnetic configuration.  Functional parameters, such as the top [[rotation]] rate or top weighting, are stringent. Employing principles of the magnetic field and [[gyroscopic]] stabilization, the  Levitron top induces levitation through a series of interactive steps. The levitated top's stabilizing rotation undergoes natural, gradual slowing, so that the levitation phenomenon fails within four minutes unless external power is supplied to sustain rotation.

To levitate the top, a plastic plate is placed on top of the magnetic base, and the top is spun on the plate at 25–50 rotations per second (1500–3000 rpm). If too slow, the top falls over and slides off sideways; if too fast it does not orient itself to follow magnetic flux as it moves, and slides off.  Since it can be difficult to spin the top fast enough by hand, Creative Gifts produced a battery-powered, hand held device to spin the top with an [[electric motor]]. Next, the plate is lifted by hand until, if conditions are right, the top rises above it to an [[mechanical equilibrium|equilibrium]] point. The top must also be weighted with washers of various sizes supplied in the kit.  If too heavy it will not rise above the plate; if too light it flies off.<ref>{{cite web|publisher=Conversation for Exploration|author=Michael V. Berry|url=http://www.lauralee.com/physics.htm|title=Levitron Physics: Frequently Asked Questions About the Levitron|url-status=dead|archiveurl=https://web.archive.org/web/19961109065520/http://www.lauralee.com/physics.htm|archivedate=1996-11-09}}</ref>

After a few minutes, the top falls when [[air friction]] slows it below the critical speed.  Air temperature, air currents, ground vibration, and power source interruptions also alter the delicate equilibrium necessary to keep the top stable. More expensive laboratory versions can sustain a levitating top indefinitely by sustaining the top rotation, actively compensating for aberrations in rotation. The makers of the Levitron have developed a "Perpetuator", which sits under the Levitron and sends out an additional magnetic pulse.  The additional force nudges the spinning top enough to maintain a constant speed.  With a constant speed, and with the Levitron perfectly level, the Levitron top can spin for longer periods of time.