The direction of geomagnetism is not fixed. About 780000 years ago, the Earth's magnetic field underwent a reversal, and then pushed forward, similar events occurred. However, the specific reason for the geomagnetic reversal is unknown so far. It is only known that this cycle will occur between 100000 and 50 million years. People still know very little about the structure of the Earth's interior, which can be said to be easy for heaven to enter but difficult for earth, To gain a deeper understanding of the Earth underground, drilling wells and tunnels is possible. However, currently the deepest drilling is only about 10 kilometers, and it is still far from reaching a depth of 2900 kilometers in the Earth's core.

The former Soviet Union once dug holes into the center of the earth, and stopped at a depth of 13000 meters. The reason is unknown. It is generally believed that the deeper the depth, the harder it is. In addition, the deeper the depth, the higher the temperature. Therefore, it is almost impossible for humans to understand the Earth through drilling holes. Therefore, someone took a different approach and decided not to drill holes directly. Instead, they measured some macroscopic parameters to simulate the accurate structure of the Earth's interior, For example, measuring the three-dimensional variation data of the Earth's gravity field can be achieved by launching satellites and using precision instruments to determine where the gravity is high, and the density inside it must be high. Then, a computer can be used to simulate the model. However, this method can only indirectly obtain some data, which is not direct enough. There are still many mysteries about the geomagnetic field that have not been solved.