Objects shown floating are (top to bottom) a silicon crystal, a gallium arsenide crystal, a British 5 pence coin, a lead musket ball, and a gold sovereign coin. The materials are separated due to differences in their density, and float at vertical positions where the total Archimedean and magnetic buoyancy is equal to their weight. The experiments were performed using an Oxford Instruments superconducting magnet with closed-cycle cooling, a system specifically designed for experiments on levitation. The magnet has a 50mm diameter open bore and is capable of producing a maximum central field of 17 Tesla.

Diamagnetism occurs as a result of a magnetic field's interference with the motion of electrons orbiting the atoms or molecules of a material. When matter is placed in a magnetic field, the magnetic force acts upon the moving electrons in the matter, causing the electrons to be deflected. This movement of the electrons interferes with the motion of the magnetic field, so the atoms internally oppose the field. This causes the material to be slightly repelled by the magnetic field.

All materials demonstrate some degree of diamagnetism. Magnetic levitation occurs when the force on such an object is strong enough to balance the weight of the object itself. The technique of immersing an object in a liquid to enhance the diamagnetic effect is called "magneto-Archimedes" levitation, due to the buoyancy provided by the liquid.

Diamagnetism has been known since the early 19th century; the first experimental confirmation of diamagnetic levitation was done with bismuth in 1939. The technique also works with living creatures; a living frog was successfully levitated when placed in the bore of a Bitter solenoid with a field strength of about 16 Tesla (the magnetic field strength of the Earth varies from about .3 to .6 gauss at sea level; one Tesla equals 10,000 gauss).

Science fiction writers can't be expected to stay away from something as cool as levitation that really works. Isaac Asimov found a use for diamagnetic levitation in his 1962 story The Currents Of Space:

The ship rolled out of the hangar like an air-borne whale, moving slowly, its diamagnetized hull clearing the smooth-packed clay of the field by three inches. The ship came to a halt, pinpointed at the lip of a take-off pit. The diamagnetic field strengthened progressively towards the ship's prow and it began tipping upward. Terens was mercifully unaware of this as the pilot room turned on its universal gimbals to meet the shifting gravity. Majestically, the ship's rear flanges fitted into the appropriate grooves of the pit. It stood upright, pointing to the sky.
(Read more about diamagnetic levitation)

The lead investigators on this project, Professors Laurence Eaves and Peter King are sure that this technique will lead to many practical applications. Professor King said: "You can use this technology to accurately sort minerals. Under vibration you throw crushed ore into the air and in the magnet the different components experience different effective gravity. They therefore tend to land at different times and after a short while the vibration sorts them into bands according to their density. The method can discriminate between components with very small differences in density enabling you to extract the precious parts you require."