Picture an orchestra without a conductor, where every musician tunes to a neighbor. In the world of tiny magnets, that is how a neodymium sphere behaves as it floats above a superconducting film. The superconductor expels the magnetic field, so the sphere hangs in the air with no support. If you set this sphere swinging, it begins to oscillate, and its oscillations can give rise to a whole set of frequencies spaced at equal intervals, like the teeth of a comb.

Until now, such magnets had been studied only in simple cases: they either damped out or oscillated at a single frequency. But now researchers have found a way to make the magnet oscillate at many frequencies at once. To do this, they drive it at a special frequency equal to the sum of two natural oscillation frequencies. The oscillations then begin to mix and generate new frequencies. Then a third oscillation joins in, the rocking of the magnet around its axis, and the spectrum becomes even richer: it contains more than sixty teeth. Each tooth is separated from its neighbor by just half a kilohertz.

Such a spectrum is like a comb in which every tooth is rigidly linked to the others. If the external magnetic field changes ever so slightly, all the teeth shift together, and that shift is easy to notice. So a levitating magnet with a frequency comb could become a highly sensitive sensor. And in the future, if the magnet is cooled to a quantum state, its oscillations could help build quantum computers and make ultra-precise measurements.