All materials normally have some amount of electrical resistance. Because of this, some energy is lost as heat when electrons move through a conductor. But for some materials, known as superconductors, this resistance reduces to zero if they are cooled to very low temperatures. This means that an electric current in a circuit made of a superconductive material could, once started, continue moving forever with no power needed.

Discovery

Superconductivity was discovered in 1911 by the Dutch scientist Heike Kamerlingh Onnes. Using liquid helium (which boils at -269°C or -452°F, just four degrees above absolute zero) to cool a wire made of solid mercury, he found that the metal's electrical resistance vanished.

​​​​​​​Why it did so remained a mystery until 1957, when three scientists explained that superconductivity arises as a result of mobile electrons bonding to form what are called "Cooper pairs". For ordinary metals, this effect happens only at extremely low temperatures, because the electron pairs are easily broken up by heat.

Superconductors that require extreme cooling are not, however, practical for use in electric power cables stretching for hundreds of kilometres; a material that superconducts at room temperature is needed. Were one to be discovered, it is probable that the main applications would be for creating strong magnetic fields. MRI scanners could be much cheaper and smaller so that every doctor's surgery could have one. Having electromagnets that wasted no energy once turned on would boost the use of maglev trains and enable the production of much more efficient motors, generators, wind turbines and even long-distance electric aircraft— all key technologies in the quest to achieve net zero by 2050.