ZAP // Pixabay / NASA
When Santa Claus finishes delivering gifts on Christmas Eve, he has to return home. Even if it’s snowing so much that the reindeer can’t see the way, the main challenge isn’t that: it’s actually getting to the correct North Pole.
There are two North Poles – the geographic North Pole that appears on maps and the magnetic North Pole on which the compass is based. They are not the same.
O Geographic North Polealso called true north, is the point located at one end of the Earth’s axis of rotation.
Try holding a tennis ball in your right hand, placing your thumb at the bottom and your middle finger at the top, and rolling the ball with the fingers of your left hand. The points where the thumb and middle finger of the right hand touch 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.
O Magnetic North Pole of Earth is different.
Hundreds more years ago, explorers began using compasses, usually made from a floating cork or a piece of wood with a magnetized needle inside, to orient themselves. The Earth has a magnetic field that acts like a giant magnet, and the compass needle aligns with it.
The magnetic North Pole is used by devices such as smartphones for navigation – and this pole moves over time.
Magnetic North Pole moves. Why?
The movement of the magnetic North Pole is the result of the Earth having a active core. The inner core, which begins about 2,000 miles below your feet, is solid and under such immense pressure that it cannot melt. But the outer core is molten, being composed of molten iron and nickel.
O heat from the inner core causes the molten iron and nickel in the outer core to movesimilar to soup in a pot on a hot stove.
O movement of the iron-rich liquid induces a magnetic field that covers the entire Earth. In turn, as the molten iron in the outer core moves, the Magnetic North Pole wanders.
For most of the last 600 years, the pole has roamed northern Canada. It moved relatively slowly, about 6 to 9 miles per year, until about 1990, when its speed increased dramatically, up to 34 miles per year.
It began moving in the general direction of the geographic North Pole about a century ago. Earth scientists can’t say exactly why, other than that it reflects a change in flow within the outer core.
How does Santa Claus know how to come home?
If Santa’s home is the geographic North Pole – which happens to be in the icy middle of the Arctic Ocean – how does he correct the course of his compass if the two North Poles are in different locations?
Regardless of the device you are using – compass or smartphone – they both rely on magnetic north as a reference to determine the direction in which you need to move.
While modern GPS systems can tell you precisely where you are as you head home, they can’t tell you exactly which direction to go without your device knowing where magnetic north is.
If Santa Claus is using an old-fashioned compassyou will need to adjust it for the difference between true north and magnetic north. To do this, you need to know the declination in the place where it is located – the angle between true north and magnetic north – and make the correction on your compass.
The National Oceanic and Atmospheric Administration has one that can help Santa.
If you happen to be using a smartphone, your cell phone has a magnetometer built-in technology that does this work for you – measuring the Earth’s magnetic field at your location and then using the World Magnetic Model to make the correction necessary for accurate navigation.
Whichever method Santa Claus uses, he may be relying on magnetic north to find his way home and then back home. Or Maybe the reindeer just know the way…
