I hear people talking about the earths magnetic poles reversing but how exactly could/would that happen?
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The core of the earth, with iron/nickel solid inside a ring of iron-nickel liquid, sees convection (circulating movement) of the liquid, which also spins the solid, and this generates a magnetic field.
Exactly how powerful, and in what direction it is oriented, depends on the way the iron liquid is moving around, and that is somewhat chaotic. It is partly influenced by the way the earth rotates, so it tends to orient roughly the same way (which is why we have a north and south magnetic pole that is roughly the same as the true rotational axis poles), but it is also strongly influenced by heat transfer requirements, which affects the rate and strength of convection currents in the liquid. Sort of like how a pot of boiling water can get somewhat chaotic.
Now, for reasons we do not quite exactly understand in detail, every so often (hundreds of thousands of years or thereabouts) the field flips inside out/upside down (the north magnet side moves to the south rotational pole, and the south magnet end moves to the north rotational pole. Not exactly clear how this works and how fast it goes.
But that is what people usually mean when they talk about pole reversal. Some people seem to think, very incorrectly, that it is the rotational poles that switch somehow. The spinning of the entire earth does not change, though, so no such “reversal” happens. Only the direction a compass points will flip direction. Sun will rise the same place and at the same time as it always does, moon will go through its phases the same way. Magnets will be “backwards” though.
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