FORGET radioactive spider bites, exposure to gamma rays, or any other accident favoured in Marvel comics: in the real world, it’s quantum theory that gives you superpowers.
Take helium, for example. At room temperature, it is normal fun: you can fill floaty balloons with it, or inhale it and talk in a squeaky voice. At temperatures below around 2 kelvin, though, it is a liquid and its atoms become ruled by their quantum properties. There, it becomes super-fun: a superfluid.
“At room temperature, helium is normal fun. Close to absolute zero, though, it becomes super-fun”
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Superfluid helium climbs up walls and flows uphill in defiance of gravity. It squeezes itself through impossibly small holes. It flips the bird at friction: put superfluid helium in a bowl, set the bowl spinning, and the helium sits unmoved as the bowl revolves beneath it. Set the liquid itself moving, though, and it will continue gyrating forever.
That’s fun, but not particularly useful. The opposite might be said of superconductors. These solids conduct electricity with no resistance, making them valuable for transporting electrical energy, for creating enormously powerful magnetic fields – to steer protons around CERN’s Large Hadron Collider, for instance – and for levitating .
We don’t yet know how all superconductors work, but it seems the uncertainty principle plays a part (see “Quantum wonders: Something for nothing”). At very low temperatures, the momentum of individual atoms or electrons in these materials is tiny and very precisely known, so the position of each atom is highly uncertain. In fact, they begin to overlap with each other to the point where you can’t describe them individually. They start acting as one superatom or superelectron that moves without friction or resistance.
All this is nothing in the weirdness stakes, however, compared with a supersolid. The only known example is solid helium cooled to within a degree of absolute zero and at around 25 times normal atmospheric pressure.
Under these conditions, the bonds between helium atoms are weak, and some break off to leave a network of “vacancies” that behave almost exactly like real atoms. Under the right conditions, these vacancies form their own fluid-like Bose-Einstein condensate. This will, under certain circumstances, pass right through the normal helium lattice – meaning the solid flows, ghost-like, through itself.
So extraordinary is this superpower that in University Park checked and re-checked their data on solid helium for four years before eventually publishing in 2004 (). “I had little confidence we would see the effect,” says Chan. Nevertheless, researchers have seen hints that any crystalline material might be persuaded to perform such a feat at temperatures just a fraction above absolute zero. Not even Superman can do that.
Read more: Seven wonders of the quantum world
