# Gravity-defying levitating superconductor on a magnetic Möbius strip

Andy from the Royal Institution made a large, suspended Möbius strip out of rare-earth magnets, then cooled down another magnet until it became a superconductor, and set it levitating and running around the track. The result is amazing, plus Andy’s explanation is cogent and fascinating. Plus, gravity-defying levitation! Levitating Superconductor on a Möbius strip (Thanks,… READ THE REST

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“Cooled down another magnet” – no. It starts off nonmagnetic. This trick works, as he describes, because the transition to superconducting “freezes” the magnetic field lines and thus the levitation position.

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It’s a very good explanation of elecro-magnetic induction. If you can find it, there’s the 1974 Royal Institution Christmas Lectures given by Professor Eric Laithwaite, who developed the linear motor (which is what this is).

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Sweet. Thomas the Tank Engine is sooooo last century.

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The title tripped me up. I guess I’d not call it “gravity-defying”, rather the less fantastical but more accurate, “gravity-overcoming”.

Does anybody else see a cartoon dog face drifting into the logo at around 0:05?

How are the magnets arranged? North pole on the outside and south pole on the inside? Or are they alternating so that the superconductor rides past north-south-north-south-etc? If the latter, the field would change, and then it wouldn’t work. But if we have north pole on one side, and south pole on the inside, then there must be at least one place on the track where the polarity changes as a Möbius strip doesn’t have an inside and an outside but just one side. What am I missing?

A mobius strip has no inside or outside like that. The magnets are arranged with one polarity in the center line of the strip and the other polarity surrounding it on the edges.

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Here’s another incredible video showing some more properties of this phenomenon that I don’t think this video illustrated very well. My mind was blown when I saw this:

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He should have shouted “Wingardium Leviosa” at the start.

One potential way to make it even more awesome: since the “car” has a reservoir for LN2 to keep the superconducting material cool, and that LN2 must be evaporating and venting away slowly, they should seal the reservoir well and direct the venting gas through a nozzle in the back of the car. No need to give it a push on each go-around anymore — the rocket-powered levitating Möbius strip train is departing the station, wheeeeeeee!

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Of course one issue will be that you would lose the Nitrogen and have to keep replacing it. However I do like the idea of use the warming of the nitrogen in some fashion. How do we use it? Could there be some sort of closed system with heating and cooling? Could it be used to create more liquid nitrogen?

Well, you’re going to lose the nitrogen one way or another - even if the “car” is insulated, it must be boiling away fairly rapidly in there. (In my experience if you fill a styrofoam cup, for example, at room temperature with LN2, the latter will all evaporate in the space of a few minutes.) I’m just suggesting directing the venting vapor so that it does some useful work

Unfortunately equipment capable of liquefying nitrogen (or otherwise achieve sufficiently cold temperatures that superconductors, even “high-temperature” ones such as the material in use in this demo, will superconduct) is far too heavy to be carried on that little car so a “closed” system (even if you could figure out a way to power it) is out of the question at this toy scale. Still, I bet if they designed it properly they could get the car to zoom around on its own “steam” for at least a few minutes on one charge of LN2.

Hmm… more elegant than my solution, which was to use a (tiny) battery powered propellor. Or perhaps there’s some variant on the Stirling Engine which might work…?

I want a superconducting skateboard and a magnetic skate park. One day…

A small part of the hole in the ozone layer is no doubt due to a car that my coworkers and I built once that was filled with the freezing spray used to cool electronic components, and vented through a little rocket nozzle on the back. It went really fast! That stuff boils at about -40c. I’m sure your idea would work.

Physics so freaking cool! This stuff should be built by kids as the are reading about superconductors have them build this and make a better transport device. SCIENCE IS AWESOME!

Maybe I missed something but it seems important that the initial cooling of the superconductor took place while it was positioned over the magnets, with a bit of spacing provided by the tray. Does this somehow “lock” the superconductor at a set distance from the magnet?

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