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How Does a Compass Work? You Will Be Amazed to Know

How Does a Compass Work
If you're lost in the woods or marooned out at sea, the use of a magnetic compass will surely get you out of your predicament. So what is it and how does it work? Read on to find out.
Rahul Thadani
Last Updated: Sep 26, 2018
Did You Know?
The earliest magnetic compasses consisted of a small piece of magnet floating in a small container of water. These were developed by the Chinese.
compass telescope and divider
A magnetic compass is a device that has been used for centuries now, and its utility in helping people find their way is beyond doubt. In fact, without this device, historic feats in navigation would be near impossible to imagine.
Before technology gave us the privilege of GPS (Global Positioning System), the act of finding out where you are and which direction you're heading to, was carried out simply with the help of this device.
What is a Magnetic Compass?
Compass sitting on top of old map
Simply speaking, a compass is basically a small magnet that has a needle attached to one end. The other end of the magnet is attached to a freely-moving pivot.
When the device is held out steadily, the magnet aligns itself with the magnetic field of the Earth. This property is not something unique to this magnet. In fact, every magnet on the planet will show a slight degree of response to the Earth's magnetic field.
How Does it Work?
True North
Compass On Antique Map
Also known as the geodetic north, true north is a direction that points to the Earth's north from the geographical point of view. It is extensively used in navigation and differs greatly from the Earth's magnetic north.
In order to determine the Earth's magnetic north, a genuine magnetic compass is required. The tip of the needle of this compass, that points to the North magnetic pole, is always marked in a prominent color that distinguishes it from the remaining elements.
Here, the magnetized needle gets aligned according to the Earth's magnetic field, and the colored tip stalls at the Earth's magnetic North.
Property of a Magnet
One of the inherent property of magnets is that like or similar poles repel each other, while opposite poles attract. Just get hold of two magnets, and try bringing them closer to one another. You'll see that a particular end of each magnet gets attracted to a particular end of the other magnet.
If you try bringing the other pair of ends close to each other, you'll experience a resistive force, which is nothing but the force of repulsion between like poles of a magnet. Now, as per the property of magnets, opposites attract (north to south).
So, when the magnetized needle points at the North magnetic Pole, it is only because it is attracted to the South magnetic Pole. Thus, the magnetic North is, in fact, the south pole of the Earth's magnetic field.
However, the north and south poles of the Earth's magnet do not exactly coincide with the geographic North and South poles. This deviation is termed as declination, and its value can differ slightly, depending on your location on the planet. To calculate the exact difference for a particular region, one may refer to local calibration charts.
Why Won't Just Any Suspended Magnet Work Instead?
In case you're curious to know why suspending any magnet won't tell you which direction you're heading to, then it's only because the earth's magnetic field is not strong enough to turn a heavy piece of iron (your magnet, what else!).
This is precisely why a very fine needle is used in a magnetic compass, and it is mounted on a bearing with little or no friction. Even a slight obstacle to the movement of the needle will make it impossible to move.
So, now that we know how a magnetic compass works, there should be one question that is bothering you: Is it for real that there is a magnet hidden beneath the layers of the Earth's crust? Well, this is just a theory.
In fact, a recent theory has stated that the Earth's core (the innermost layer) is made up of molten iron, a part of which gets converted to crystalline form due to extreme pressure. The rotational motion of the molten iron is what leads to the formation of the Earth's magnetic field.
A magnetic compass comes in handy for sailors, and people who go hiking or exploring the woods. In today's world, there are other advanced devices that do the same job, but they are all based on the same concept.
Once you have understood its working, it is easy to see why it has been around for so many years. The simplicity with which it can be made is commendable, and even today there are many people who gladly choose to use an old-fashioned magnetic compass.