Floating magnets demonstration

In addition to the zero resistivity, superconducting materials are perfectly diamagnetic in other words, magnetic fields (up to a limiting strength that decreases as the temperature rises toward Tc) cannot penetrate them (the Meissner effect). This is a consequence of the mobile, paired state of the electrons. Indeed, it is the demonstration of the Meissner effect, rather than lack of electrical resistivity, that is usually demanded as evidence of superconductive behavior. One entertaining consequence of the Meissner effect is that small but powerful magnets will float (levitate) above the surface of a flat, level superconductor.30... 

Superconductivity is demonstrated here as a superconducting ceramic pellet floats above an array of magnets. (Photo courtesy of the Argonne National Laboratory.)... 

The levitation demonstration works only with Type II superconductors because the magnetic field lines that do enter the superconductor resist sideways motion and allow the balance of magnetic repulsion and gravitation to float the magnet above the superconductor. With Type I superconductors, the magnetic field lines cannot enter the superconductor at all and, because there is no resistance to sideways motion, the magnet will not remain stationary over the superconductor. 

About the same time, advances in magnetic resonance spectroscopy allowed a measure of the dynamics of biological membranes, demonstrating that lipids behaved more like a fluid constrained to two dimensions than a solid. This finding, combined with experiments demonstrating the lateral diffusion of proteins in membranes, generated the concept of the membrane as a sea of lipids with a mosaic of associated proteins either floating on the surface or embedded within a bilayer of... 

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