The Real Levitation


It is truly fascinating to watch an object freely hovering in mid-air and, not surprisingly, levitation has found its way into myths, science fiction and even politics . Leaving science fiction aside, physics does know scores of different ways to levitate things. For instance, a helicopter can be considered as a very impressive levitation device that uses a stream of air to keep floating. Scientists have also found many ways to levitate things without any noise or the need for petrol or air, by using electromagnetic fields. Levitating trains and levitating displays are but two examples of electromagnetic levitation. However, in all such schemes, a source of energy (an engine or a battery at least) is always required to keep an object afloat. Remove the battery and the levitation inevitably stops.

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 superconducting pallet levitating above a strong magnet. This levitation does not suffer any stability problems because the magnetic flux is pinned by defects in superconducting materials. For this fortuitous effect, superconductors can levitate even below a magnet. Superconducting levitation is a very well known phenomenon and not discussed further on this site. 
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. For several decades, this levitation possibility had been in oblivion - even for experts in high magnetic fields - until we levitated a live frog in 1996.
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. Engineers designing bearings in a motor or a disk drive are also unlikely to have ever considered levitating devices (magnetic bearings) that would require such conditions. Now, there is a way - at last - to have miniature levitating devices that even schoolchildren can make. As the picture shows, the real levitation is now at our fingertips.
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