4 ms·

https://en.wikipedia.org/wiki/Earnshaw%27s_theorem https://en.wikipedia.org/wiki/Earnshaw%27s_theorem

• jacquesm 3y ago
  stationary. Hence the 'as long as it is moving' bit above. Because the motion allows for the coils to generate enough of a current to drive the compensation. So you need a support system to bring the assembly up to a certain minimum speed above which it will stably levitate.
  • floxy 3y ago
    Right. Everyone should just read up on Earnshaw's theorem to know what all the boundary conditions are. https://en.wikipedia.org/wiki/Levitron https://en.wikipedia.org/wiki/Levitron
    • jacquesm 3y ago
      I wonder how long you could get one of those to spin in a vacuum. Halbach arrays with compensating coils have been proposed for some interesting applications, such as low loss flywheels for electrical storage. I don't know if that ever got commercialized but I do recall that some prototypes were made by a US company. I can't find a reference to it though.
      • floxy 3y ago
        >I wonder how long you could get one of those to spin in a vacuum. Not too much longer apparently... https://www.youtube.com/watch?v=mn7IedCgva0 https://www.youtube.com/watch?v=mn7IedCgva0