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The black block underneeth is a "high temperature super conductor" . In the beginning it is warm. No super conductivity. Then it is cooled with liquid nitrogen and therefrom becomes superconducting. The superconductor has NO electric resistivity. If a magnet comes close, it tries to induce an electric current into the SC. If once a current is flowing, it will flow on and on: it will not change in strength, the Amperage stays the same. That is why the magnet above will float and not fall down. Funny that the magnet stays in whatever position it is left. The magnet fields around it become frozen. The big, strong magnet also floats, but is also capable of pulling the super conductor up.
When taking the SC out of the nitrogen bath its temperature will rise so that the superconducting effect comes to an end.
WiLi