(1) Permanent magnet theory is the earliest theory, which holds that there is a huge permanent magnet inside the earth, and this permanent magnet generates the earth's magnetic field. This is an assumption of a permanent magnetic field. The earth originated from a huge magnet. /kloc-at the end of 0/9, the famous physicist Madame Curie discovered the physical characteristics of magnets, that is, when heated to a certain temperature, the original magnetism will disappear. This just proves that the earth was just a huge magnet at the beginning of its birth. It attracts asteroids, meteorites and magnets with iron, cobalt and nickel nearby. The high temperature for some reason makes the magnetic force of this magnet disappear and become the core in the middle of the electromagnet ... because this core is not fixed, the magnetic poles will be reversed. Newton discovered that the gravity of the earth is actually a magnetic force. Of course, these still need to be verified by scientists. According to the Curie point, ................... concluded that there could be no permanent magnet in the earth, but that doesn't mean that it wasn't a permanent magnet in the first place.
⑵ The internal current theory holds that there is a huge current inside the earth, forming a huge electromagnet to generate the earth's magnetic field, but this huge current is not observed, and it will decay rapidly and will not exist for a long time.
(3) The charge rotation theory (AD 1900, abbreviated as 1900) holds that there are charges with opposite signs and equal amounts on the surface and inside of the earth, and the earth rotates to form a closed current and generate a magnetic field, but this theory lacks theoretical and experimental basis.
(4) Piezoelectric effect theory (1929) holds that the matter in the earth separates the charges in the matter under ultra-high pressure, and the electrons move in such an electric field to generate current and magnetic field. But theoretically, such a magnetic field is only about one thousandth (10-3) of the geomagnetic field.
5. The theory of gyromagnetic effect (1933) holds that the rotation of strong magnetic substances in the earth can produce the earth's magnetic field, but the magnetic field produced by this gyromagnetic effect is only about 100 billion times that of the earth's magnetic field (10-1).
[6] Thermoelectric effect theory (1939) holds that the heat generated by radioactive materials in the earth causes the continuous uneven convection of molten materials, thus generating thermoelectric electromotive force and current, and then generating the earth's magnetic field, but the theoretical estimation is also inconsistent with the earth's magnetic field.
(7) The generator theory (1946- 1947) holds that the conductive liquid inside the earth generates a stable current, and the earth's magnetic field is generated by this current.
(8) The theory of rotating body effect (1947) is based on the empirical laws observed by a few celestial bodies, and it is believed that a rotating body with angular momentum will generate a magnetic moment, thus generating a magnetic field. This theory needs to use constants without scientific basis, which was rejected by the scientists who put forward this theory five years later based on accurate experimental results.
⑼ The theory of magnetic line kink (1950) holds that the tension characteristics of magnetic lines in the earth's magnetic field and the poor rotation of the core will amplify the original weak earth's magnetic field, thus producing the earth's magnetic field.
⑽ Hall effect theory (1954) holds that the Hall effect will produce Hall electromotive force and Hall current under the simultaneous action of the temperature difference current generated by the uneven temperature in the earth and the original weak magnetic field, thus producing the earth's magnetic field.
⑾ electromagnetic induction theory (1956) holds that after the strong magnetic activity of the sun reaches the earth through the solar wind of charged particles, it will generate the current inside the earth through electromagnetic induction and rectification, thus generating the earth's magnetic field. Among these theories, only the generator theory (also known as magnetohydrodynamic generator theory) has been proved more in observation, experiment and theoretical research, and the earth's magnetic field theory is more widely studied and applied.