... like I'm 5 years old
Imagine you're holding a small, round box with a needle inside it. This needle is not just any needle, but a magnetized one, and it always points in one direction: North. This is the basic idea behind a compass. The Earth is a giant magnet, and the North Pole of this magnet pulls the needle of the compass towards it. That's why the needle always points North. So, if you're lost and you have a compass, you can always find your way by seeing which way the needle points.
Think of it like a game of tug-of-war. The Earth is on one side, pulling the needle towards its North Pole. No matter how you turn or tilt your compass, the Earth always wins and pulls the needle in a northern direction.
... like I'm in College
To understand how a compass works in more detail, let's dig a little deeper into the physics behind it. The Earth, as we know, has a magnetic field. This is caused by the molten iron in its core that generates electric currents. These currents, in turn, produce a magnetic field. The compass needle, being a small magnet, aligns itself with this magnetic field. So when we say that the compass points North, it's actually aligning itself with the Earth's magnetic field.
The compass needle is usually balanced on a pivot point that allows it to move freely. It's also painted in a way that one end (usually the North-pointing end) is distinguishable from the other. This way, users can tell the direction just by looking at the compass.
Imagine you have a large Lego baseplate, representing the Earth. Now, imagine a line of blue bricks running from one end of the plate to the other. This line represents the Earth's magnetic field.
Next, take a small Lego piece - this will be our compass. Attach a freely spinning Lego propeller on top of it. One blade of the propeller is red, representing the North end of the compass needle, and the other is white.
Now, no matter where you place or how you rotate the small Lego piece on the baseplate, the red blade of the propeller (representing the North end of the compass needle) will always try to align with the blue bricks (representing the Earth's magnetic field) running from one end of the plate to the other. This simple Lego setup illustrates the principle of how a compass works.
... like I'm an expert
At the expert level, we delve into the principles of magnetism and geomagnetism. The Earth's magnetic field, or geomagnetic field, is mostly dipolar, meaning it has two poles, North and South. It's generated by the convective motion of molten iron in the Earth's outer core, a phenomenon explained by the dynamo theory.
The magnetized needle of a compass aligns itself with the lines of the magnetic field, pointing towards the magnetic North. However, it's important to note that the 'true North' (geographical North) and 'magnetic North' are not exactly the same. This difference, known as magnetic declination, varies depending on one's location on Earth and needs to be accounted for in navigation.