Admittedly, a jet ski/wakeboard that lets you fly across a lake is pretty awesome. But when we think of hoverboards, we don’t think of wetsuits and water jets, we think of Back to the Future. And the only way to get close to Marty McFly’s hoverboard is with magnets and superconductors.
A real hoverboard could take advantage of magnetic levitation (as in the GIF above). Superconductors are named as such because they are materials in a state that can conduct electricity with no resistance. Instead of heating up and eventually melting—like a normal copper wire would if you put too much electrical current through it—superconductors let electrons move through them as they please.
The other odd feature of superconductors is that they actively exclude magnetic fields from their interiors. Place a magnet above one and the magnetic field is forced around the superconductor, which creates a current. Called induction, the generated “supercurrents” within the material in turn produce their own magnetic fields! The opposing magnetic fields interact with the magnet and suspend it above the superconductor.
Change the magnet’s position above a superconductor and the supercurrents change along with it. Because the supercurrents flow without any resistance, levitating fields can respond to a magnet’s movement almost instantaneously and keep it floating, as you can see below:
Opposing magnetic fields generated in response to a moving magnet is the reason why dropping a magnet through a copper tube is so amazing to watch and how “Maglev” trains get around without friction. But there is another option if you want to make a real hoverboard—flip everything around and use “flux pinning.”
Instead of putting a magnet above a superconductor, you can put a special kind of superconductor above a magnet and “pin” it in space. Type type-II superconductors, like the one featured in this now viral “quantum locking” video, are superconductors that also expel magnetic fields from their innards, but not perfectly. These superconductors are thin enough for flaws in the material to allow small “flux tubes” or “quantum vortexes” to leak through. When that happens, it’s like suspending a pincushion on a bed of nails—the superconductor is locked in space.
The effectiveness of the pinning depends on the strength of the magnets and the distance of the superconductor from the magnets, but the results are incredible. Below, a flux-pinned superconductor levitates and follows above a magnetic track:
In fact, the closest thing I have ever seen to a real, Back to the Future-style hoverboard is one using superconductors suspended above magnets. The contraption below certainly looks the part:
So, knowing that Tony Hawk and Doc Brown totally lied to you about developing a real hoverboard, how close are we to making something like a flux-pinned board? You could have one right now if we built the infrastructure. All we would have to do is install high-powered magnets along all city streets and give everyone access to vast amounts of liquid nitrogen (that doesn’t sound dangerous at all!). Or, if we ever realize the dream of room-temperature superconductors—superconductors that don’t have to be freezing to conduct electricity without resistance—we could do away with the liquid nitrogen entirely.
Other than playing Bioshock Infinite (flux pinning is how the city floats!), the only way to really experience true hoverboards is to somehow commercialize flux-pinned travel (looking at you Elon Musk). Until then, the closest you’ll get to being McFly is to stand on a skateboard aboard a Maglev train.
Kyle Hill is the Chief Science Officer of the Nerdist enterprise. Follow the continued geekery on Twitter @Sci_Phile.