Magnet is a common thing. The compass, one of China's the Four Great Inventions, is made of magnets. Everyone knows that magnets are attractive to iron. Why? Where does its energy come from? Starting from the microscopic world, as we all know, any substance in the world is composed of molecules, which in turn are composed of atoms. Atoms are composed of nuclei and electrons outside the nucleus, with nuclei positively charged and electrons outside the nucleus negatively charged. Electrons outside the nucleus move around the nucleus, creating a magnetic moment. Therefore, a single atom is magnetic. Therefore, everything is magnetic, but the atomic arrangement of general matter is disorderly, Magnetism cancels out each other, so its external appearance lacks magnetism.

From the above description, we can know that individual atoms also have magnetism. When the magnetic moments are arranged in an orderly manner, all the magnetic fields inside the atoms overlap with each other, and the object becomes magnetic, forming a magnet. Common magnets include metals such as iron oxide and nickel, and the atoms that make up them are very "disciplined". The atoms are arranged neatly and uniformly, and all the magnetic poles point in the same direction, which shows magnetism and becomes a permanent magnet, It can attract iron objects. There are natural magnets in nature, and iron tools can also be placed inside high-voltage coils for electromagnetic magnetization, which can be used to make magnets.

In addition, the Earth itself is also a large magnet. Due to the existence of the Earth's magnetic field, most of the charged particles invading the Earth are shielded by the Earth's magnetic field, protecting the Earth's organisms and environment from the invasion of the solar wind. So, how is the Earth's magnetic field generated? The simple answer is that the molten material in the Earth's crust forms an electric current through convective motion, which in turn forms a geomagnetic field. Of course, the cause of the geomagnetic field is relatively complex and currently there is no consensus.