When Santa is done delivering presents on Christmas Eve, he must get back home to the North Pole, even if it’s snowing so hard that the reindeer can’t see the way.

He could use a compass, but then he has a challenge: He has to be able to find the right North Pole.

There are actually two North Poles – the geographic North Pole you see on maps and the magnetic North Pole that the compass relies on. They aren’t the same.

The geographic North Pole, also called true north, is the point at one end of the Earth’s axis of rotation.

Try taking a tennis ball in your right hand, putting your thumb on the bottom and your middle finger on the top, and rotating the ball with the fingers of your left hand. The place where the thumb and middle finger of your right hand contact the tennis ball as it spins define the axis of rotation. The axis extends from the south pole to the north pole as it passes through the center of the ball.

Earth’s magnetic North Pole is different.

Over 1,000 years ago, explorers

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