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By making significant improvements in the material science and manufacturing of paramagnetic and diamagnetic materials. Magnetic bearings are limited by Earnsha
by akiselev 8y ago
By making significant improvements in the material science and manufacturing of paramagnetic and diamagnetic materials. Magnetic bearings are limited by Earnshaw's theorem [1] which states (roughly) that you can't stabilize some regular magnets using only their charge - they have to dynamically respond ti each other or they'll all just fly off. Usually this is done with electromagnets and a control system like in jet engines but its expensive and difficult. The alternative is passive para/diamagnetic materials whose magnetic fields change based on the other fields around them but those are usually rather exotic and have to be precisely engineered. Without that stabilization, the bearings would be worse that useless since they would never be able to prevent the rotor from touching the stator.
[1] https://en.wikipedia.org/wiki/Earnshaw%27s_theorem https://en.wikipedia.org/wiki/Earnshaw%27s_theorem
- adrianN 8y agoAs I understand it from the Wikipedia article, the theorem doesn't apply for spinning systems.
- ajuc 8y agoThere're so many loopholes: > Spinning ferromagnets (such as the Levitron) can—while spinning—magnetically levitate using only permanent ferromagnets > Pseudo-levitation constrains the movement of the magnets usually using some form of a tether or wall. This works because the theorem shows only that there is some direction in which there will be an instability. Limiting movement in that direction allows levitation with fewer than the full 3 dimensions available for movement (note that the theorem is proven for 3 dimensions, not 1D or 2D).