Hello, Magnetic North

A while back, I heard this very interesting Guardian podcast on the magnetic north pole. In case you’re wondering, “magnetic north” refers to wherever the compass points. As opposed to “geographic north”, which is the top point of the axis around which the earth rotates.

Edmund Halley convinced the British Navy to fund his idea of plotting points on the globe by comparing the deviation between magnetic north and geographic north. The obvious use of this was in sea navigation. In theory, that was a good idea. In practice, it didn’t work. Why? Because the data was collected over a few years. Trying to combine data collected in Year 1 with that from, say, Year 3 led to all kinds of weird errors! This may “sound like a failure of epic proportions” but it led to a major scientific finding.

The errors led to the realization that the magnetic north moves continuously, ergo data from different times wasn’t consistent! Today, we know the extent of the movement over the last few centuries. How? By going over maritime data from sea-faring vessels over time, we can see how much it has moved. For most of that recorded period, all the way until the last 50 years, the north magnetic pole was always somewhere near Canada, moving back and forth by 5-10 kilometer a year. Its speed of movement in the last few decades has increased to about 50-60 km per year. So much so, today magnetic north lies closer to Siberia than Canada!

But should we be worried about this? Or is it just trivia? Well, our GPS systems, including the ones on our beloved smartphones, use the world magnetic model map to calculate our orientation. So as the magnetic north moves, our GPS on the phone needs to adjust for the updated magnetic model map data. And yes, it would affect the aurora’s: we’d be able to view them from newer locations in a few decades time.

Archaeological data from the directions rock point to says that such movements have been happening throughout the earth’s history. But why does it move? The center of the earth is very hot, enough to melt the iron and nickel in there. The rotation of the earth causes the liquid iron and nickel to move around, which causes magnetic north to move. The recent acceleration seems to be because of a strong fluid flow in the outer core of the earth. The north magnetic pole has gotten caught in it and is getting pushed. In fact, it seems that North and South will switch in the next thousand years or so.

The magnetic field’s strength has only been measured over the last few decades. And it is getting weaker, at least over those few decades. But we can’t predict where things are headed yet as the root cause lies far too deep in the earth. The podcast calls it like the state of weather forecasting a hundred years back!