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Many common materials such as water, wood, plants, animals, diamonds, fingers, etc. are usually considered to be non-magnetic but in fact, they are very weakly diamagnetic. Diamagnets repel, and are repelled by a strong magnetic field. The electrons in a diamagnetic material rearrange their orbits slightly creating small persistent currents which oppose the external magnetic field. Two of the strongest diamagnetic materials are graphite and bismuth.
The forces created by diamagnetism are extremely weak, millions of times smaller than the forces between magnets and such common ferromagnetic materials as iron. However, in certain carefully arranged situations, the influence of diamagnetic materials can produce startling effects such as levitation.
Today's science knows only one way to achieve REAL levitation, i.e. such that no energy input is required and the levitation can last forever. The real levitation makes use of diamagnetism , an intrinsic property of many materials referring to their ability to expel a portion, even if a minute one, of an external magnetic field. Electrons in such materials rearrange their orbits slightly so that they expel the external field. As a result, diamagnetic materials repel and are repelled by strong magnetic fields.
Three basic schemes using various aspects of diamagnetism allow the true levitation:
SUPERCONDUCTING LEVITATION
Superconductors are ideal diamagnetics and completely expel magnetic field at low temperatures. The picture shows a sumo wrestler standing on a levitating magnet platform that floats above a high-temperature superconductor. The superconductor is cooled by liquid air and hidden below the platform.
DIAMAGNETIC LEVITATION
An object does not need to be superconducting to levitate. Normal things, even humans, can do it as well, if placed in a strong magnetic field. Although the majority of ordinary materials, such as wood or plastic, seem to be non-magnetic, they, too, expel a very small portion (0.00001) of an applied magnetic field, i.e. exhibit very weak diamagnetism. Such materials can be levitated using magnetic fields of about 10 Tesla.
DIAMAGNETICALLY STABILISED LEVITATION
Low temperatures (such that air turns liquid) and powerful magnets (such that cooking pans are drawn from a distance of several meters) are not what one is likely to have at home to be able to watch the superconducting or diamagnetic levitation. To learn more, click on the title above. Now, there is a way - at last - to have miniature levitating devices that even schoolchildren can make.
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