Jean Marchand, age 10, of Kingston, Ontario,Canada, for her question:
Why are the magnetic poles at the rotation axis?
The earth, as we well know, spins around like a top, once every 24 hours. It spins around an imaginary line that runs straight through the center of the globe. This is the axis of rotation. The North and South Geographic poles are situated where the two opposite ends of the axis come to the surface. Actually the two magnetic poles are some distance from the geographic poles, which makes them some distance from the ends of the axis.
We are told that the needle of a magnetic compass points to the North Pole. It is natural to assume that this is the geographic North Pole at one end of the earth's axis. The truth is that the compass needle points to the North Magnetic Pole, which is about 1,000 miles away from the Geographic North Pole. The axis North Pole is a pinpoint under the Arctic Ocean. The Magnetic North Pole is a sizeable oval area around Prince of Wales Island in Northern Canada.
The two poles in the southern Antarctic are even farther apart. The South Magnetic Pole is about 1,600 miles from the axis South Pole. What's more, the axis poles and the magnetic poles tend to drift closer and then farther apart. In the past 25 years, the two north poles have crept 70 miles closer and half a century ago they were 200 miles farther apart.
Our planet behaves as if a giant magnet were buried in the bowels of the earth. It is surrounded by an enormous magnetic field and its two opposite poles surface near, but not at, the axis poles. Scientists suspect that the earth's magnet may run like a mighty dynamo, powered by tremendous magnetic and electrical energies.
At present, nobody can explain exactly how it works. But we do know that our earth's mighty magnet misbehaves. Through the ages it grows weaker and then stronger. And for some mysterious reason, once in a great while it flip flops and the north and south poles switch places.
But this is by no means the entire strange polar story. Though the axis and magnetic poles stay within a few hundred miles of each other, the two pairs go on global tours. Or so it seems. About half a million years ago, the two north poles were on the map near Hawaii. About 350 million years ago they were near Japan. From there they wandered across the North Pacific toward their present location in the Arctic. Meantime the south axis and magnetic poles wandered from the Atlantic toward the Antarctic.
This is even more mysterious when we are told that the axis does not change. The North and South Pole continue to point to the same spots in the sky. What happens is this. The earth has a restless cruet that slithers around like a loose jacket. As it moves, different parts of the world map pass over the Polar Regions and through the ages the Polar Regions seem to go on global tours.