Superconductivity is a unique quantum state of matter in which a material acquires the ability to conduct electric current with absolutely zero resistance. This astonishing phenomenon was discovered in 1911 by the Dutch physicist Heike Kamerlingh Onnes when he cooled a liquid mercury wire to an extremely low temperature, close to absolute zero (approximately -269°C). In a conventional conductor, such as a copper cable, moving electrons constantly collide with vibrating atoms in the crystal lattice, causing some of the energy to be irretrievably lost as heat. In a superconductor, this process is completely eliminated: current flowing through a closed loop can circulate for billions of years without decay or recharge.