The moon is the only satellite on the earth. Because the cycle of the moon's rotation around the earth's axis is the same as that of its revolution around the earth, which is 27.3 days, people have been facing the earth in the same way for billions of years, and people can only see 59% of the moon. How its back shape became an eternal mystery in the history of human civilization. It was not until1June 19591June 1959 that the first batch of photos of the back of the moon were taken by the "Moon 3" probe of the former Soviet Union, which enabled human beings to see the whole picture of the back of the moon. However, with the deepening of observation, the mystery behind the moon is becoming more and more complicated than in the past. This is mainly the obvious difference between the back of the moon and the front of the moon, which is puzzling
The biggest difference between the back and the front of the moon is its continental nature. More than 90% of the 30 or so "oceans", "lakes", "swamps" and "bays" on the moon are on the front, accounting for about half of the area of the regular hemisphere. There are only two complete "seas" on the back of the moon, accounting for less than 10% of the area in the back hemisphere, and more than 90% of the back of the moon is mountains. The distribution of mountains presents several huge concentric circles, and the terrain is seriously uneven, which is unprecedented in the past.
Another strange thing is that the longest radius and the shortest radius of the moon are on the back of the moon. General astronomy books say that the moon has a diameter of 3476 kilometers or a radius of 1738 kilometers, which means the average. In fact, the maximum radius of the moon is 4 kilometers longer than the average radius, and the minimum radius is 5 kilometers shorter than the average radius, and they are all on the back of the moon.
Another manifestation of the difference between the front and back of the moon is that the moon tumors are concentrated on the front. Lunar tumor, also known as lunar mass, is a place with relatively high gravity on the surface of the moon. Scientists estimate that in these places, more high-density substances are concentrated below the surface of the moon. In addition, there are some places on the moon where the gravity distribution is less than normal. Strangely, the positive anomaly area where the moon tumor is located and the anti-anomaly area with small gravity are all on the front, and many places have been found, but none on the back of the moon.
Why are there these remarkable differences between the front and back of the moon? There are different opinions in the scientific community. Some people think that when the earth moves between the sun and the moon, there will be a total solar eclipse on the moon (but it is a total lunar eclipse on the earth), and a huge temperature difference will be formed on the front of the moon. The sudden change of temperature again and again will cause differences before and after. Some people think that the earth attracts the moon, which leads to a phenomenon similar to tidal fluctuation, that is, the "solid tide" causes the difference before and after. But these explanations are not very convincing. Most people think that the mystery behind the moon should be explained by the structure and movement of the moon itself, but there is no good explanation today.