A superconductor is an element, inter-metallic alloy, or compound that will conduct electricity without resistance below a certain temperature. Resistance is undesirable because it produces losses in the energy flowing through the material. Once set in motion, electrical current will flow forever in a closed loop of superconducting material–making it the closest thing to perpetual motion in nature. In the image below, a magnet is levitated on a superconducting material.