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

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