If a very long bar magnet is made and is allowed to free fall in a black hole, a point will come when exactly the north pole is inside and south pole is outside the event horizon for a very small amount of time. At that point of time, the magnetic field lines from north pole must not travel outside the event horizon to the south pole and the south pole outside must behave like a monopole. Is this thinking perspective correct?
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1$\begingroup$ So why can't you just cut the bar into pieces, leaving one pole in one piece? $\endgroup$– Jon CusterCommented Jan 10, 2023 at 19:07
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3$\begingroup$ A bar magnet actually consists of many little magnetic dipoles. $\endgroup$– GhosterCommented Jan 10, 2023 at 21:23
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1 Answer
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At that point of time, the magnetic field lines from north pole must not travel outside the event horizon to the south pole and the south pole outside must behave like a monopole. Is this thinking perspective correct?
No, that is not correct. The magnetic field lines are not causal lines. They can be spacelike and thus go out of an event horizon.
What cannot travel outside the event horizon is changes in the magnetic field, that is electromagnetic waves. In fact, a black hole can be charged and spinning in which case the black hole itself will produce an electromagnetic field, just not a wave.
