Science Puzzle
Which Way Does a Compass Really Point?
The end of a compass needle that points north is called its north pole. Magnets attract when opposite poles face each other, north to south, and push apart when like poles face each other.
So what kind of magnetic pole is there in the Arctic, pulling the north end of every compass needle towards it?
The Answer
Magnetically, it's a south pole. Opposite poles attract, so the north end of a needle can only be pulled towards a south pole.
The names come from history, not from physics. Long before anyone understood magnetism, the end of a compass needle that swung towards the north was named its "north-seeking" pole, later shortened to north pole. Earth's own magnetism then has to have a south pole near the Arctic to attract it. Geographers still call that place the North Magnetic Pole, because it's in the north, even though in magnet terms it's a south pole.
Earth's magnetism isn't really a bar magnet. It's generated by molten iron swirling in Earth's outer core, thousands of kilometres down, acting like a giant natural dynamo. And the magnetic pole isn't at the geographic North Pole. It's hundreds of kilometres away and it wanders, in recent decades by tens of kilometres a year, drifting from the Canadian Arctic towards Siberia, which is why maps have to be updated for compass users.
Every so often, over hundreds of thousands of years, Earth's magnetic field flips completely and compasses would point south. The last flip happened about 780,000 years ago, and the record of it is frozen into volcanic rocks that cooled at the time.
The principle: Opposite magnetic poles attract. A compass needle's north pole points towards Earth's magnetic pole in the Arctic, which must therefore be a south magnetic pole, even though it's named for its place on the map.