Few devices have had a greater influence on shaping human history than the magnetic
And yet its ability to guide our Earthly wanderings may be
ephemeral – here today, gone tomorrow. Well, maybe not tomorrow, but perhaps in the not too-distant future.
Not to worry; magnetism itself isn’t in jeopardy – the little cow
magnets on your fridge aren’t going to start sliding to the floor
along with all those important scraps of paper that help you
navigate through daily life.
What is changing is the thing that makes magnets useful in direction-finding:
our planet’s magnetic field. It’s not terribly strong
overall, and as navigators have known for centuries, what
strength it has varies quite a bit from place to place.
As a result of local distortions in the field, there are only a few
places in the world where a compass will actually point to the
geographic North Pole. Fewer still are the places where it will
point to the magnetic North Pole. The two are often hundreds of
miles apart, and while the former is the relatively fixed rotation
axis, the latter wanders noticeably on a daily basis.
Currently, it is in northern Canada and moving north at nearly
350 feet (107m) per day, or about 24 miles (38km) every year. At
this rate, the magnetic North Pole will be in Siberia in 30 years,
taking our sky-painting auroral displays with it.
On top of all that, roughly four times in every million years, the
North and South poles switch sides. Aaaaaaaaaaaaaaargh!