The levitating train

What happens when a material is cooled to extremely low temperatures?

In some cases, it can become a superconductor: a special state of matter in which electrical resistance disappears and the material acquires surprising magnetic properties.

One of the most fascinating characteristics of superconductors is that they behave as perfect diamagnets: that is, they tend to expel the magnetic field from within themselves. This phenomenon, known as the Meissner effect, allows a suitably cooled superconductor to interact spectacularly with magnets, to the point where it remains suspended above a magnetic track. For this reason, superconductors are also being studied for potential applications in high-speed transport and other advanced technologies.

The proposed activity consists of an interactive demonstration of magnetic levitation using a superconductor. A small superconducting sample is cooled with liquid nitrogen and placed on top of a magnetic track. Once the required temperature is reached, the sample can remain suspended and ‘frozen’ in place, moving along the track like a tiny levitating train.

The demonstration offers students an engaging opportunity to observe first-hand a phenomenon that may seem surprising at first glance but can be explained by the laws of physics, introducing concepts such as superconductivity, low temperatures, magnetic fields, the Meissner effect and the technological applications of quantum materials in a straightforward way.