Superconductive device and method for demonstrating autorotation
CROSS REFERENCE OF RELATED APPLICATION 
     This application is a continuation-in-part of application Ser. No. 07/571,451, filed Aug. 23, 1990, entitled &#34;Gadget and Method For Demonstration of Perpetual Motion.&#34; 
    
    
     FIELD OF THE INVENTION 
     This invention relates generally to superconductive devices and particularly to an apparatus for demonstrating autorotation. 
     BACKGROUND OF THE INVENTION 
     Throughout history, men have attempted to create an autorotation mechanism, or a device which rotates of its own accord, but up to now, such attempts have not been successful. In one attempt, and in a Japanese Patent No. 63-282774, a magnet is levitated above a superconductive material cooled by liquid nitrogen. However, in this patent, while the magnet is free of restraint, it must have an external force applied to it in order to cause it to rotate. As such, this apparatus does not demonstrate autorotation. Additionally, an article entitled &#34;A Double-Decker Levitation Experiment Using a Sandwich of Superconductors,&#34; by Anthony T. Jacob, Charles I. Pechmann, and Arthur B. Ellis, published in the December 1988 Journal of Chemical Education at page 1094, discloses an arrangement wherein a magnet is sandwiched between plates of superconductive materials which, when cooled by liquid nitrogen, causes the magnet and superconductive plate resting on the magnet to both be levitated. As in the Japanese patent, there is no suggestion that this arrangement is capable of autorotation. 
     Accordingly, it is an object of this invention to provide an apparatus for demonstrating the principle of autorotation wherein a magnet levitated above superconductive materials generally rotates of its own accord without externally applied forces. 
     Summary of the Invention 
     This invention relates to an apparatus and method for demonstrating autorotation of a levitated magnet in conjunction with stacked superconductors. In this apparatus, configurations constructed of superconductive oxides are vertically stacked one on the other and placed in an insulative container. A permanent magnet is generally centered on the stack of superconductors, and a coolant sufficient to lower a temperature of the stacked superconductors is placed in the container. After the temperature in the superconductors is lowered to below a temperature at which they become superconductive, the magnet is levitated and generally will begin to rotate without externally applied forces. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     The single figure of this invention is a cut-away side view thereof. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The drawing of FIG. 1 shows the device, which includes a plastic, insulative foam cup 1, about 2&#34; or more in diameter and about 0.75&#34; or more high. A first superconductive plate 2 about 1.0&#34; in diameter and about 0.25&#34; thick and constructed of yttrium oxide, barium oxide, and copper oxide, as is known in the art, is centered in the bottom of the cup. A second superconductive plate 3 of like dimensions and constructed of like materials is positioned over or stacked on superconductive plate 2. A round cover 4 of non-magnetic material, such as aluminium foil, and about the diameter of cup 1, may be placed loosely over the stacked superconductive plates. This cover prevents vapor generated by liquid nitrogen from obscuring the results. A SmCo (samarium, cobalt) disc-shaped permanent magnet 5 about 3/16&#34; in diameter and about 1/16&#34; thick is placed on cover 4 generally centered over the stacked superconductors 2 and 3. 
     For demonstrating autorotation, liquid nitrogen is poured over the aluminium foil, the liquid nitrogen flowing between edges of the aluminium foil and inner sides of the cup and into cup 1, and may be replenished as necessary as it vaporizes. After the stack of superconductive discs 2 and 3 cool to below their superconductive temperature, disc magnet 5 will begin to levitate in a plane generally parallel to the surface of the upper superconductive plate 3, and in most instances will begin to rotate of its own accord and in either direction about an axis 7 of disc magnet 5, as indicated by arrow 8. This is in contrast to the prior art, where the magnet must have an external force applied to it in order to begin the rotation, after which the magnet will stop rotating after a period of time. It is believed that this rotation occurs and continues because of imbalances in the levitating force, or the Meissner effect, between the upper and lower discs 2 and 3 and the magnet at superconducting temperature. 
     In instances where the magnet does not begin to rotate on its own, which occurs in less than fifty percent of attempts, the cup holding the apparatus may be moved, unbalancing the repulsing forces, and causing the magnet to begin its rotation.