How magnetic levitation works: magnets, sensors, and floating objects

How does magnetic levitation work? One magnet repels another, but this repulsion alone is never enough to keep an object stationary in the air: it needs a system that constantly corrects its position. In a levitating lamp, this role is carried out by sensors and electromagnets hidden in the base. Here is the principle, its variants and its limits.

Why can't a magnet float on its own?

A magnet cannot float stably above other fixed magnets: this is a law of physics, not a manufacturing defect. The British mathematician Samuel Earnshaw demonstrated this in 1842: no arrangement of permanent magnets or stationary charges can keep an object in stable equilibrium in all directions.

In practical terms, repulsion can be adjusted to exactly compensate for the object's weight vertically. But as soon as the object shifts by a millimetre to the side, the force pushes it even further, and it tips over. Anyone can check this with two fridge magnets: they repel each other, then are turned around and stick together.

To circumvent this theorem, there are four ways out: active electronic adjustment, diamagnetic materials, superconductors or the rapid rotation of the object. Almost all decorative objects use the first.

How does magnetic levitation work in a decorative base?

A levitation base combines a permanent magnet, which supports the weight, and electronics, which prevent the object from escaping to the side. The globe or figurine itself contains a magnet; it is the "base magnet / object magnet" pair that creates the upward push.

The ring magnet: the force that lifts

At the centre of the base, a ring-shaped magnet repels the magnet housed in the object. This repulsion compensates for gravity at a precise height, the air gap, which is often around 1 to 3 cm in decorative models. The heavier the object, the closer it descends to the base, up to the system's load limit.

Sensors and electromagnets: the correction loop

Beneath the ring, four small coils, the electromagnets, face each other in pairs. A Hall effect sensor, which converts a magnetic field into electrical voltage, detects the slightest shift of the object. A circuit then adjusts the current in the coils to bring it back to the centre.

This "measure, correct" loop runs continuously, far too fast for the eye to perceive the movement. This is what circumvents Earnshaw's theorem: the equilibrium is not static, it is maintained at every moment. This is also why the object falls as soon as the power is cut.

Top levitation: the suspended object

A second design places the electromagnet above the object, in an arch. The magnet attracts the object upwards, and the sensor reduces the current as soon as it rises too high. This setup, which is rarer in decoration, is recognisable by its gantry-shaped structure.

How does light get into a floating globe?

In most floating light globes, the LED is powered wirelessly, by induction. An emitter coil in the base creates an alternating magnetic field; a receiver coil in the object picks it up and converts it into current, like a wireless phone charger.

The distance between the two coils remains small, which explains why the lighting only works when the object floats above the base. Placed on a table, far from its base, the globe becomes a simple inert object again.

Why can the object spin on its own?

A levitating object spins for a long time because it does not rub against anything: only air resistance slows it down. A slight push of the hand is enough to start a slow rotation that can last for many minutes.

Some displays maintain this rotation with a small fan blowing on the object, while others play with the coils. The result is the same: a smooth rotation, without a visible motor, which enhances the impression of an object from another world.

What are the other types of magnetic levitation?

There are four main ways to make an object levitate with magnetism. Not all can be used at home, but they illustrate the same physical laws.

Diamagnetic levitation provided a famous image: in 1997, researchers at the University of Nijmegen, in the Netherlands, made a living frog float in a field of around 16 teslas, hundreds of thousands of times more intense than the Earth's field. The body, composed mainly of water, is weakly repelled by such a powerful field.

Superconductors, on the other hand, only work at very low temperatures. Cooled with liquid nitrogen, to around −196 °C, they freeze the field lines and hold a magnet in place, even upside down. For other physics experiments that defy intuition, our article on fascinating physical phenomena and the objects that showcase them continues the discovery.

How can a train run without touching its rails?

A magnetic levitation train, or Maglev, floats above its track thanks to electromagnets or superconducting magnets. With no contact with the rail, it has neither wheels nor mechanical friction, which allows it to reach very high speeds.

Two families coexist. The Shanghai line, opened in 2004, uses attraction: electromagnets attached to the train, under the rail, attract it upwards, with a gap of around one centimetre that is constantly controlled, the same principle as our suspended objects. The Japanese system uses superconducting magnets and repulsion; it reached 603 km/h during a test in 2015, the record for a train.

The base placed on a desk and the 600 km/h train therefore follow the same idea: a magnetic force that compensates for the weight, and a control that keeps the whole thing centred.

How to place a levitating object without dropping it?

Levitating an object requires above all patience: you need to find the balance point above the centre of the base, then release the object without pushing it. The first attempts often fail, which is normal.

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