Everyone’s talking about this crazy new hoverboard that looks too good to be true.
And it sort of is.
But trust me, the truth is super cool!
That was a pun.
You’ll get it once I explain how- y’know what, just roll the intro.
Hey McFly guys and girls, Julian here for DNews.
It’s 2015, the year Marty went re-back to the future, and Lexus has teased us all with
a short video of a functioning hoverboard being ridden around a skatepark.
Is it real?
Is it possible?
Yes and qualified yes.
I’ll explain:
What’s not shown in the video is the hidden magnetic track Lexus installed in the Barcelona
skate park.
That may seem like cheating, but it’s more complicated than just using magnets.
If you’ve ever played with magnets and tried to levitate one above the other, you know
it’s not easy.
As soon as you let go, the magnet will just flip around and get sucked to the other one
and that’s really the opposite of what you want.
But that problem doesn’t exist with some superconductors.
A superconductor is a material that, when cooled past a critical temperature, lets electrons
move freely within it with zero resistance.
Obviously this makes them great for high current wires, but the freely moving electrons do
something else too.
They create currents on the surface that screen the superconductor from magnetic fields.
As you cool a superconductor past its critical temperature it expels magnetic fields, and
this is called the Meissner effect.
If you put a superconductor by a magnet, it will repel it.
Put one above the other, and it’ll levitate.
This is called Quantum Levitation.
But not all superconductors are created equal.
Some, called Type-II superconductors, actually have little vortices of current and the center
of each vortex is like an eye of a storm.
In the middle, the material behaves normally and lets some magnetic field lines, or flux,
pass through.
When I say “some” I should note it’s still quite a lot.
A 3 inch disk can have as many as 100 billion flux lines passing through it.
The superconductor will actually pin the flux lines and will appear to lock itself in place
levitating above a normal magnet.
So they don’t just exhibit Quantum Levitation, but Quantum Locking too.
No, not like the weeping angels, Whovians.
Anyway, you can move the magnet around, even put the superconductor underneath it, and
it will still stay locked where it was.
Plus with all those flux lines pinned down, a 3 inch disk just half a micron thick can
support 70 thousand times its own weight.
So it locks in place above a normal magnet, but if the superconductor is above a circular
magnet, it can rotate around the axis of the magnet.
You can expand that circular magnet to a track any size and shape you want and, say, hide
it under a skate park.
Put a Type-II superconductor above it, give it a little push, and it can happily zoom
around the track no problem.
Mind you, there are limitations.
The superconductor has to be cold.
Like, really really cold.
Even so-called “High Temperature” superconductors need to be at least -135 degrees celsius.
To hit those temperatures you need to use liquid nitrogen, which explains the thin wisps
of smoke and frost coming from Lexus’ hoverboard.
The superconductor also has to be thin, because the thinner it is the stronger the flux-pinning
effect.
And the magnetic field can’t be too dense.
Too much flux per meter squared and the vortexes overwhelm the material, turning it back into
a not-so-superconductor.
By the way, the unit for magnetic flux density is the Tesla.
that’s right, Tesla has his own unit of measurement.
I thought you’d like that, internet.
Type-II superconductors were discovered in 1935, 20 years before the first Back to the
Future took place.
But Robert Zemeckis wasn’t around then to show us the way, and now in 2015 his vision
is finally realized.
So long as you keep your super thin superconductor supercooled, you too can have a hoverboard.
Provided you don’t mind going around in circles on a magnetic track.
Which would still be really cool, but wouldn’t help you if you’re trying to get away from
Biff’s larcenous grandson.
Magnetic levitation can be scaled up too and because the only friction is from air, that
means you can get going pretty fast.
Trace talks about maglev trains here.