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by rini17 2174 days ago
For similar reason you can't use Earth's magnetic field to lift stuff - it's so weak you need impractically strong magnet (note) and/or impractically big and at the same time lightweight structure.

(note) and it must not be permanent magnet, as the sibling explains - you must vary the magnetic field to "convert it" into electric field which then does the lift

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Maybe if magnetism is combined with a gravitational slingshot it would be possible to extract energy.