Quantum Locking, also known as Quantum Levitation, is the incredible phenomenon where a superconductor is locked in space above a magnet.
When a metal gets cool enough (like minus 180 degrees Celsius cold), it is in a superconductivity state that does not like magnetic fields, and will do its best to expel magnetic fields from the inside.
However, when a superconductor has some imperfections, some magnetic strands about 1 billion of them across the disc in the experiment, are not expelled and locks the disc's position in three dimensional space.
Because it does not want to lose energy, the superconductor holds on to these strands and locks itself in place, but put it on a magnetic track and it will go on a journey that is frictionless and with zero energy loss.
The reason it stops after a while is because the superconductor needs to be cold enough to maintain its state, and the disc used in the demonstration simply doesn't remain below that critical temperature for a long period of time.
And don't be fooled by its small size of the disc shown in the images above. This seemingly frail looking disc can theoretically hold up to 70,000 times its own weight. A 2mm thick, 3 inch in diameter plate would be able to hold up to 1,000kg in weight (or about a small car).
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