magnetic fields - Is Earth really a magnet?

I am a student of class 9. When I was going through magnetism and read that an earth is a magnet I got some doubts. My question is: is earth really a magnet? Doesn anyone have any proof that earth is a magnet? Is there a magnetic core at the center of the earth? Has anyone reached the core of the earth?

Answer

Earth has a magnetic field. You can verify this yourself; it is why a compass works. Just take any magnet and hang it carefully from a string. As long as there's nothing else magnetic around and it's well-balanced and free to rotate, it will line up with Earth's magnetic field.

We have measured the Earth's magnetic field all over the surface and up into outer space using satellites. The magnetic field is fairly weak; on the surface of Earth it is about a hundred times weaker than a simple refrigerator magnet, which is why we don't notice it often in daily life. No one has reached the core of the Earth; our knowledge about it is inferred using physics, mathematics, and geology.

Whether or not Earth "is a magnet" is a semantic issue, but the existence of the magnetic field is not in doubt. This magnetic field is important to life on Earth because it deflects a lot of the harmful radiation that reaches Earth through space. It is also responsible for the auroras that appear near Earth's poles.

The magnetic field is not caused by a part of the Earth being magnetized like a refrigerator magnet. Instead, it is caused by a the motion of liquid metal inside the Earth, which causes currents that generate a magnetic field. The metal moves because the Earth is different temperatures at different spots, because of gravitational forces, and because of Earth's rotation. This phenomenon is called "convection" and you can see it when you boil a pot of water.

The physics behind generation of Earth's magnetic field is called "magnetohydrodynamics". The equations involved are very complicated and difficult to solve, but there is little doubt about the fundamental mechanism. By examining old rocks, we know that Earth's magnetic field periodically switches directions. We can write computer programs that simulate Earth's magnetic field, but there is still uncertainty about details such as when the next reversal will be or how long the field will last.