Levitation, ultra powerful server stacks, and gyroscopes that are so sensitive that they can directly measure the curvature of spacetime. Each one is a feature of a truly amazing type of material called a superconductor.
To see how it works, we have to start with electricity. Electricity is the movement of electrons through a material.
Electrons moving through copper cables power your home, your car battery pulls them from chemicals and throws them into your engine to start your car, and your computer opens and closes logic gates that control the flow of electrons through its circuit boards.
But when electrons flow, they create heat, which impedes the development of many more advanced technologies, like smaller, and more powerful computers. It happens because when electrons travel through the wire or circuit board, some of them smack into the atoms of the circuit board which makes them vibrate.
This collision slows down the electron and transfers some of their energy to the atom. If you looked at the circuit board with a powerful enough microscope, you’d see the atoms vibrate, and this vibration is heat. The material gets hotter as more electrons flow through it.
To get powerful computers, you have to cool them down (which is why computers have fans, or liquid cooling).
Some enthusiasts use aquariums to cool their high powered computers. They use oil, not water.
But another thing you can do is use special materials, like something called a ‘superconductor’. This is because for certain kinds of materials, at very low temperatures, a strange property from quantum mechanics emerges.
As a quick refresher, there are two categories of particles in quantum mechanics:
- Fermions, which include quarks and electrons, and
- Bosons, like gluons, which carry the fundamental forces.
These particles spin all the time like mini gyroscopes. The type of spin is what makes a particle a fermion or a boson.
Bosons spin in ‘whole’ amounts, like a regular gyroscope. They spin 360° degrees to get back to their starting position.
Fermions spin in ‘half’ amounts. There is no real analogy for this in our normal world. They spin 720° to get back to their starting position. Fermions are like are strange mathematical objects that should only exist in the mind of a deranged mathematician, but are actually a fundamental part of reality.
The fact that bosons and fermions particles spin in these discrete ‘quantities’ of whole or half is actually the basis of the name ‘quantum’ mechanics.
The spin has a bunch of effects, but the most important one for superconductors is ‘state’. Bosons can occupy the same state (i.e. position and momentum) and not interfere with each other, like different radio waves travelling through the air simultaneously.
Fermions can’t occupy the same state at the same time, like two tennis balls can’t sit on the same spot on ground at the same time. This is called the ‘Pauli exclusion principle’, and it won some guy a Nobel prize.
Ok, time for what a superconductor actually is.
In some special kinds of materials, and at very low temperatures, two electrons (which are half-spinning fermions) can join up together, forming a pair, and act like a whole spinning boson. Suddenly, like bosons, they can occupy the same state at the same time as other electron pairs.
This is actually incredible. They get zero resistance from the material they’re flowing through, or from each other (this is called ‘BCS theory’). The material is transformed into the perfect, heatless conductor of electricity.
These materials are called superconductors.
You can make a wire, a circuitboard, or anything out of a superconducter and pass electricity through it without creating waste heat.
That is pretty useful so far, but they can also levitate magnets.
Because all of the electrons inside the superconductor can move around inside it completely unimpeded, they create a magnetic field. But if you place a magnet on top of the superconductor, the flow of electrons will shift to accommodate the magnet, and the field they create will repel and attract the magnet at exactly the right about to suspend the magnet above it. What you end up with, is levitation.
The easiest superconductor to use is called Yttrium-barium-copper oxide. To get it to the right temperature, you have to pour liquid nitrogen on to cool it to -200oC. The problem is that it is too brittle to make into a wire or circuit board, and most of the other superconductors need way colder temperatures which makes them impractical. One of the holy grails of materials research is a superconductor that is malleable and can operate at room temperature.
This is called a ‘high temperature superconductor’, and it would probably change the world. Some practical uses could be:
- Replacing all copper wires with the superconducter. This would mean:
- Move electricity much more efficiently in a city’s central power grid.
- Replacing a city’s extensive electrical wires with a small, thin underground strip.
- Moving electricity across longer distances, making renewable sources of energy much more viable.
- Computers that give off very little heat allowing us to build them much smaller and much, much more powerful.
- Batteries that do not degrade over time.
- Making a ‘qubit’, the fundamental component of quantum computers.
- High precision gyroscopes that will be able to measure the exact curvature of space-time around the Earth.
- New types of high-speed magrail trains that will move with far less friction.
A superconductor on a special magnetised track, like a prototype super magrail train