How can we achieve levitation
The phenomenon that you saw here for a moment is called quantum levitation and quantum locking. And the object that was levitated here is a superconductor. Superconductivity is a quantum state of matter that is only possible below a critical temperature.
It's a well-known phenomenon that was discovered 100 years ago. But only recently, thanks to technical advances, have we been able to demonstrate quantum levitation and quantum locking.
A superconductor is determined by two properties. First: it has no electrical resistance and, second, it displaces magnetic fields from within. Sounds complicated, doesn't it? But what is electrical resistance? Electricity is the flow of electrons within a material. As they flow, the electrons collide with atoms and lose some of their energy with each of the collisions. They lose this energy in the form of heat, an effect we are all familiar with. These collisions do not exist in a superconductor and so no energy is lost.
Quite remarkable when you think about it. In classical physics there is always some friction and thus energy loss. But not here, since we are talking about a quantum effect. But that's not all. Superconductors do not like magnetic fields and try to displace magnetic fields from their interior, which they can achieve with the help of circulating currents. The combination of these two properties - the displacement of magnetic fields and the lack of electrical resistance - is exactly what defines a superconductor.
But theory and reality do not always agree 100%, sometimes a few bundles of magnetic field lines remain in the superconductor. Under the right conditions, which we have here, these bundles of magnetic field lines can be trapped in the superconductor. And these magnetic field lines inside the superconductor occur in discrete quantities. Why? Because it's a quantum phenomenon. It's quantum physics. And as it turns out, they behave like quantum particles.
In this movie you can see them flowing discreetly. They are bundles of magnetic field lines, not particles, but they behave like particles. That is why we call this effect quantum levitation and quantum locking.
What happens to the superconductor when we place it in a magnetic field? At first some bundles of magnetic field lines are trapped inside, but the superconductor doesn't like them to move because their movements consume energy and thus disrupt superconductivity. The superconductor locks these bundles, which are also known as fluxons, and holds them in place. As a result, the superconductor locks itself in place. Why? Because a movement of the superconductor would also mean a movement of the fluxons and would change their configuration.
So we get a quantum lock. Let me show you how this works. Here I have an insulated superconductor. Now if I place it on a normal magnet, it's just locked in the air.
It's not just levitation. It's not just repulsion. I can rearrange the fluxons and everything is locked in the new configuration. e.g. like this, or a little further to the right or left. So this is quantum locking - real locking - the superconductor is locked in three dimensions. Of course I can turn it upside down and it stays locked.
Now we understand that "levitation" is actually a lock. Yes, we understand. You shouldn't be surprised if I take this round magnet, in which the magnetic field is exactly the same all around, so that the superconductor can move freely around the axis of the magnet. Why? As long as it rotates, the lock remains. Can you see it? I can rearrange and rotate the superconductor. We have smooth movement. The superconductor is still floating, but can move freely.
So we have quantum locking and we can make it float on the magnet. But how many fluxons - bundles of magnetic field lines - are there in a single disk like this? Well we can calculate it, and there are many. One hundred billion magnetic field lines on this 7.5 cm disc.
But that's not the astonishing thing, I have kept one thing secret. The amazing thing is that the superconductor you see here is only half a micrometer thick. So extremely thin. And this incredibly thin disc can support more than 70,000 times its own weight. An incredibly powerful effect.
Of course, I can also extend this round magnet to form any track. E.g. a large round track like this one. And when I put the superconductor on this track, it can move freely.
And again, that's not all. I can change the position of the superconductor and make it rotate. He moves freely in his new position. And I can still try something new; let's try this for the first time. I can place this disc here and while it stays here - don't move it - I'll try to turn the track upside down and hopefully if I get it right the disc will stay in the air.
You can see it's quantum locking, not levitating. Let's spin the disk a little more while I tell you about superconductors. Um - (Laughter) - So we know we can run enormous currents in a superconductor. We can also use them to create strong electromagnetic fields. Those that we need, for example, in MRIs or particle accelerators. Since we have no energy loss in superconductors, we can also store energy with their help.
And we could produce power lines that we can use to move enormous amounts of electricity between power plants. Imagine if we could protect a single power plant with a superconducting cable. But what is the future of quantum levitation and quantum locking? Let me answer the question with an example. Imagine you had a disk similar to the one in my hand, three inches in diameter, but with one key difference. The superconducting disk is two millimeters thick instead of half a micrometer, i.e. quite thick. This two millimeter thick, superconducting disk could hold 1,000 kilograms, a small car, in my hand. Amazing. Many Thanks.
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