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I was shown a toy, yesterday, which I would like help understanding qualitatively.

A fellow engineer showed me a kit which included three main parts:

1.) A base (black box), approximately 4 inches square and 2 inches high, weighing about 2 pounds (quite heavy for its size). No batteries.

2.) A rigid plexiglass window, also 4 inches square, which rested nicely on top of the base.

3.) A top. This object was about 1.5 inches tall. a flat metal washer (ID = about 0.25", OD = about 1.0") was mounted on the top-side of the top, and a plastic washer slid down over the top post of the top, to keep the metal washer securely in place. The owner said that the system was designed like that so that multiple metal washers could be used. (We only used one.)

OPERATION:

1.) Place the top in the very center of the plexiglass and give it a good spin.

2.) With the top spinning in the very center of the plexiglass, gently and slowly lift the plexiglas about 1 inch off of the base. The top will levitate up off the plexiglass about 4 inches, and hang suspended for about 1/2 a second before it falls off to a side (as if it were sliding off of an invisible 4-inch-tall and 4-inch radius hemisphere. EDIT: We must have been doing something wrong. I found a video of this top staying levitated for almost 2 minutes:

www.fatbraintoys.com/toy_companies/fascinations/levitron_platinum_pro_combo.cfm?display=video

3.) I noticed that on one of my trial runs, the washers flew off the top AFTER it had levitated and BEFORE it had fallen to the desk.

QUESTIONS:

1.) (My main question) How does this thing work?

2.) Anyone know where this kit (and/or other like-minded novelties) are sold? (I tried "Think Geek," but was disappointed in their selection of mag-lev products.) EDIT: Found a very similar toy at:

www.fatbraintoys.com/toy_companies/fascinations/levitron_platinum_pro_combo.cfm

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I think a picture of the toy would much help. :) –  Saeed Neamati Jul 15 '11 at 17:52
    
@Saeed: See links for something similar. I actually drew up a pic, but don't know how to add a .jpeg to my question. –  Vintage Jul 15 '11 at 19:07
    
i found this for levitron youtube.com/watch?v=sCpCam0cUiw –  anna v Jun 29 '13 at 18:52
    
from a deleted answer by Georg levitron.com/physics.html –  anna v Jun 29 '13 at 18:58
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1 Answer

What you are looking for is contained in these two articles, explaining the physics of the "Magnetic Levitron" ... pretty cool stuff.

Stability of Levitrons (Dullin, Easton) http://www.maths.usyd.edu.au/u/dullin/preprints/Levitron.pdf

The Levitron: An Adiabatic Trap for Spins (Berry) http://www.phy.bris.ac.uk/people/berry_mv/the_papers/Berry271.pdf

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