[Epona]

Polar shift I believe happens every few ten thousand years or so, but the magnetic poles do move slightly all the time.

As an archaelogist, this is used to date production on ancient kiln sites. When a kiln is fired, the iron particles present in all ceramic (clay based) goods (including the kiln itself) are fixed in alignement with the poles of the earth. So you can use highly sensitive compasses to date when a kiln was last used, by comparing the alignment of iron particles to where magnetic north was at any given period in history. The constant shift of magnetic north makes this a fairly accurate dating method for ceramic production sites.

Thought you would find that interesting! [img]smile.gif[/img] Yet another wonderful use for natural magnetism.