A rigid plastic tube with a square cross section² of 19 mm (3/4 in) was cut (a small, fine-toothed hobby saw works well) to leave 5 mm of the tube with a base (Fig. 1). Squares of pyrolytic graphite,³ 12 mm, were sawed from larger pieces and epoxied to the plastic with a 2-mm cubic NdFeB magnet⁴ trapped inside. Two large ceramic magnets⁵ placed with opposite poles facing each other were set 15 to 20 cm apart, standing on one of the narrow sides, on an overhead projector with the graphite squares enclosing the magnet at the center. The small magnet orients its poles to face the opposite poles of the large magnets. When it is below the center of the field, there are upward force components that provide lift. Pyrolytic graphite is highly diamagnetic. Since the force is repulsive when the magnet approaches the diamagnetic material, a negative feedback is produced, providing stability. Distances between the large magnets are adjusted so that the small magnet is levitated and near the center of its enclosure (Fig. 2). When the projector is focused on the magnet, its bobbing about the equilibrium position makes the levitation evident to all.

Figure 1.

Figure 2.

The ceramic magnets can be sealed in plastic boxes (not shown) that are lined with foam rubber to keep the magnet faces at a minimum distance of about 1 cm at all times. This reduces the chance of scratching the projector surface and the chance of injury or magnet chipping when the magnets slap against each other. If the boxes have a flat end, the magnets can still be stood on edge without tipping.