Superconductivity is the flow of electrical current without any resistance to that flow. Even the best conductors have some resistance to electrical current. But superconductors do not. Unfortunately, superconductors only exist in the extreme cold of near absolute zero.
Even though the practical application of this discovery has not yet been realized, superconductivity holds the promise of super-efficient electrical and magnetic motors, of electrical current flowing thousands of miles with no loss of power, and of meeting the dream of cheap and efficient electricity for everyone. Superconductivity will likely spawn whole new industries and ways of generating, processing, and moving electrical energy. But that potential still lies in the future.
Heike Kamerlingh Onnes was born in 1853 in Groningen, the Netherlands, into a wealthy family that owned a brick making factory. As he went through college and graduate school, he drew considerable attention for his talent at solving scientific problems. By the time he was 18, Onnes had become a firm believer in the value of physical experimentations and tended to discount theories that could not be demonstrated by physical experiment.
At the age of 25, Onnes focused his university research on the properties of materials at temperatures approaching the coldest possible temperature (-456°F or -269°C). The existence of that temperature, the temperature at which all heat energy is gone and all motion, even inside an atom, ceases, was discovered by Lord Kelvin, and is called 0° Kelvin (0°K) or absolute zero.
Several theories existed about what happened near 0°K. Lord Kelvin believed that absolute zero would stop the motion of electrons. Electrical current would cease and resistance to that current would be infinitely large. Others believed the opposite, that resistance would fall to zero and electrical currents would flow forever.
Everyone had a theory. Onnes decided to find out, to test the theories.
However, there was a problem. No method existed to cool anything anywhere near -269°C. Luckily, Onnes was the physics department chair at the University of Leyden, and that department came equipped with a well-funded physics lab that Onnes could use.
In 1907 Onnes invented thermometers that could measure temperatures as extreme as absolute zero. In 1908 he discovered a way to cool the gas helium so cold that it turned into a liquid. He was able to continue to chill the super-cold liquid until, late that year, he chilled liquid helium to 0.9°K, less than one degree above absolute zero. Onnes realized that he could use this liquid helium to chill other materials to near 0°K to measure their electrical resistance.
By 1911 Onnes had developed canisters capable of holding and storing his super-cold liquid helium and had set up a small production line. He began his electrical studies by chilling first platinum and then gold to near absolute zero. However, the electrical currents he measured were erratic, his results inconclusive.
Onnes decided to switch to liquid mercury. He filled a U-shaped tube with mercury and attached wires to each end of the U. The wires were attached to a meter to measure electrical resistance. He used liquid helium at 0.9°K to cool the mercury.
As the temperature dipped below 40°K (-229°C) electrical resistance began to drop. It dropped steadily as the temperature dipped below 20°K. And then, at 4.19°K resistance abruptly disappeared. It fell to zero.
Onnes repeated the experiment many times over the next few months and always got the same result. Below 4.19°K, there was no resistance to the flow of electricity. An electric current would flow unimpeded for ever. He called it superconductivity.
Onnes had discovered superconductivity, but he could not theoretically explain it. He only suspected that it had something to do with the (then) recently discovered Quantum Theory. It was not until 1951 that John Bardeen developed a mathematical theory to explain superconductivity.
A search began to find ways to create superconductivity at higher (more practically reached) temperatures. The current record (using, unfortunately, toxic ceramic compounds made with mercury and copper) is 138°K (-131°C). Once a way is found to create superconductivity at warmer temperatures, the value of Onnes’s discovery will be unlimited.
AT CERN, the European high-energy physics research lab, scientists used a one-time jolt of electricity to start an electrical current flowing through a superconductor circuit. That electrical current ran, with no additional voltage input, for five years with no loss of power. In common house wires, an electrical current would stop within a few milliseconds once the voltage is removed because of the resistance of electrical wires.