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At what height do navigation compasses stop working?
Mike Follows Sutton Coldfield, West Midlands, UK
A compass needle is essentially a thin bar magnet. If it were free to move in all three dimensions, a magnet would line up along any local magnetic field line. Field lines are graphical representations of the strength and direction of the magnetic field in a region of space.
In principle, a navigation compass will work anywhere there are magnetic fields (which exist throughout the universe), although this doesn’t guarantee that it would be helpful as a navigational aid.
Earth’s magnetic field, the magnetosphere, extends to at least two or three …