Concepts explained
A Room-Temperature Superconductor Will Change the World — The Three Technologies That Live at Minus 269
In the summer of 2023 a Korean paper claimed a superconductor that works at room temperature. Shares jumped, laboratories worldwide rushed to check, and a few weeks later the answer was no. But the fuss revealed something: fusion, quantum computers and hospital MRI all live at the same temperature, and making that temperature is the bottleneck all three share.
Zero resistance
Send electricity through a wire and the wire warms. The path is obstructed, and the obstruction becomes heat. That obstruction is resistance. An electric heater is resistance made deliberately large; a cable is made thick to make it small. But never zero.
In 1911 Onnes in the Netherlands cooled mercury to 269 below and its resistance suddenly vanished — not shrank, vanished. A current started inside it keeps circulating with nothing pushing it, and does not fade over years of watching. That is .
And it does one more thing. A superconductor pushes magnets away. Set one above a magnet and it floats. That is the picture you have seen of a levitating train.
Why does it vanish?
Current is electrons passing through a metal. Inside the metal the atoms are packed close, and an electron travelling alone keeps colliding — like pushing alone through a crowded corridor. Every collision is heat.
Very cold, something strange happens. The electrons pair up, and the pairs all move together in step. Not one person forcing through the crowd, but a line holding hands. A line does not collide. No collision, no heat; no heat, no resistance.
Three technologies at one temperature
Put the things this series has visited side by side.
KSTAR's magnets are superconducting. A magnet strong enough to hold a hundred-million-degree plasma would, in ordinary copper, survive only seconds before its own heat undid it. To run all day it must have zero resistance.
A superconducting qubit is a current circling in a superconducting loop, and to keep the waves from jumbling it must sit even closer to absolute zero — the coldest of the three.
Imaging the inside of a body needs a very strong magnet, and that magnet is superconducting. A superconducting machine in every hospital — the only one of the three already part of daily life.
Three technologies, born in different places and doing different work, with one bottleneck: making and keeping 269 below. And that hangs on one substance.
Helium
Minus 269 is the temperature at which helium becomes liquid. Of all substances helium stays liquid to the lowest temperature, so to go below it there is no other way than to immerse things in liquid helium.
But helium is scarce on Earth. It is extracted from the small amounts mixed into natural gas underground, and few countries produce it; Korea imports all of it. Once it leaks it is lighter than air, rises out of the atmosphere and is gone. KSTAR, the quantum laboratory and the hospital all employ people to keep this precious gas from escaping.
A little further in
So what is real and what is inflated?
Electricity lost in power lines is a few per cent of the total. Real, but not world-changing. The real prize is not the loss but the magnet: strong magnets that need no freezing would make fusion machines, MRI and trains cheaper and smaller all at once.
Laboratories worldwide made the same material and resistance did not reach zero. The apparent drop in the paper turned out to come from an impurity mixed in. But the speed of the checking was science working as it should.
In 1986 materials appeared that superconduct at −196, the temperature of liquid nitrogen, which is far cheaper and commoner than helium. Cables made of them already run beneath some city streets.
Under enormous pressure, superconductivity near room temperature has been reported. Without pressure, nothing yet — and no proof that it cannot exist.
Japan is building one between Tokyo and Nagoya. The opening has been postponed repeatedly — not for want of technology but of land and money.
Where the discovery came from
Superconductivity was not sought. Around 1900 there was a race in Europe to reach the lowest temperature. Kelvin had shown there was a floor, absolute zero, and how close you could get to it was a matter of pride.
Onnes won the race by liquefying helium in 1908. Then, dipping one thing after another into his liquid helium, in 1911 he saw mercury's resistance disappear. A by-product of a race to make ice. Why it happened was not explained until 1957, forty-six years later — the electron pairs described above.
So this technology has been in the making for over a century. The effect in 1911, the explanation in 1957, liquid-nitrogen temperature in 1986, room temperature not yet.
In Daejeon
Two places in Yuseong-gu make 269 below: KSTAR's superconducting magnets and the quantum computer at the Korea Research Institute of Standards and Science. When KSTAR was built no superconducting tokamak existed anywhere, and the wire for its magnets was wound by a Korean firm that had never built a tokamak. That experience now stands beside the refrigerator at the standards institute.
What you would study to do this
- Someone who hunts for new superconductors — physics and materials. The people at the centre of the 2023 uproar, still searching for one that works without pressure.
- Someone who makes superconducting wire — materials engineering. Most superconductors are brittle, and drawing them into wire that can be wound is a craft of its own.
- Someone who winds the wire into magnets — electrical and mechanical engineering. The people who wound KSTAR's.
- Someone who makes and keeps 269 below — cryogenic plant. The third time this seat has appeared in the series.
- Someone who recovers helium — plant and safety. Helium that escapes is never seen again.
The fifth line is the unexpected seat. Helium is scarce and once leaked is lost to space, so large hospitals and laboratories keep plant that collects used helium and turns it back into liquid. Whoever tends that plant is the person guarding the institution's superconductivity. It is work with pipework, pressure and gas, and a technical high school's pipefitting and gas certificates lead straight to it. The same seat as the cooling people in the fusion and AI pieces, appearing for the third time in this series. Three times is not a coincidence.
So
There is no room-temperature superconductor yet, and the 2023 one was not it. But the uproar showed something: fusion, quantum computing and MRI hang from one temperature, and that temperature costs helium and people. So the day a room-temperature superconductor truly arrives is the day all three technologies get lighter at once. One thing changes three. That is why the uproar.
Until then, the people who make and keep 269 below stand underneath all three. In the making.
The question that remainsIf a discovery nobody was looking for, a by-product of a race to make ice, holds up three technologies a century later — which of today's races will leave a by-product like that?