You may have little need for them today with all the fancy navigation and map applications around, but the compass is still the backbone of modern geography and navigation. This interesting and somewhat mythical device needs no batteries and no internet connection, running only on the magnetic fields of the earth. Sounds kind of magical right? As supernatural as it sounds, the principle of how a compass works is based on scientific philosophies that date as far back as 2000 years ago! So how exactly does a compass work? Read on to find out.
How the compass came to be
Before the invention of the compass, people used to navigate using the stars or watching the birds. Interestingly, both of these are based on the same principle as the compass - birds detect and follow magnetic fields, while celestial bodies provide reference points for direction. People generally weren’t brave enough to venture far out into the ocean though for fear of a cloudy night blocking the stars, or losing the birds along the way, so they generally sailed along the coastline. This limited people greatly and as you can imagine, it took much longer to get to where you were going.
Not very much is known about exactly who invented the compass, but many historians postulate that it was invented in the Middle East or China. Somehow, someone discovered that lodestone, a mineral native to the region, would always turn to a particular direction when it was suspended in water.
So how does it work?
It was only discovered much much later that a compass works because of magnetic fields generated by the Earth. A magnetic field is essentially rays of energy that begin at the very center of the Earth and radiate outward from what we call south to what we call north. Why or how the Earth generates these energies is very complex - it has to do with the movement of molten iron and nickel in the Earth’s core and the generation of electricity from that. It really feels very transcendental. So the Earth is essentially a giant magnet. Magnetic “waves” move from the north side of a magnet to the south side of a magnet. Why does it work the other way with Earth? Here’s where it gets tricky. So the part we call south is actually the north side of Earth’s magnet and the part we call north is the south side of Earth’s magnet. So, picture lines moving from the bottom of the Earth to the top.
Now, a compass itself is a magnetic bar with north and south sides too. When it is in Earth’s magnetic field, the north side of the compass points to the south side of Earth’s magnet (remember that’s actually at the top) because magnets flow from north to south. So the north of the compass points to the “top” part of the world, and that’s why we call it north!
How to read a compass
The needle of the compass will always point north. A compass has this needle on top of a piece of paper or plastic with the various directions drawn on. Picture yourself facing north. The needle will point to the north and be in line with the N on the compass. Now turn 90 degrees to your left: the needle will still be pointing north, but you are facing west, so on the compass the needle will rest on the east-west line. It’s really simple when you start by facing north, then turn yourself in the direction you want to go!