June 18, 2021

Looking at the earth from the moon, why does it make people feel terrified?

In addition to the earth and the sun, the moon is the most familiar celestial body to mankind. Except for the new moon and rainy days, we can see the moon most of the time, sometimes even during the day. But have you ever thought about what it would be like to stand on the moon and look at the earth with your own eyes? Why do some people say they will feel fear?

Humans have not yet established a base on the moon, and there is no one on the moon. Mankind has launched many lunar probes. At present, the only ones that can work normally on the lunar surface are my country’s Chang’e-3 lander, Chang’e-4 lander and Yutu-2 rover. These unmanned probes have all operating hours Has greatly exceeded the design life.

Chang’e-4 and Yutu-2 are located on the far side of the moon, and the earth cannot be seen there. This is not because the moon does not rotate, but because the time for the moon to revolve around its axis is exactly the same as the time for it to revolve around the earth, both are 27.3 Earth days.

Due to this special phenomenon of synchronous rotation, the moon always hides behind one side, which becomes the back of the moon, which we cannot see on the earth. Because the back of the moon would block radio signals from reaching the earth, human probes had never been there before Chang’e-4.

The other side of the moon always faces the earth. This is the front side of the moon. We can only see this side on the earth. Conversely, only on the front side of the moon can we see the earth hanging in the sky. Chang’e-3 landed on the front of the moon and took a picture of the earth:

As you can see from this photo, the earth is not a complete circle, but a crescent shape. This is because the Chang’e-3 at the time was looking from the side of the part of the earth illuminated by the sun, and the part of the earth that was not illuminated was in darkness.

As the moon moves in its orbit, the phase of the earth will change accordingly, just as the moon has cloudy, sunny, and lack of sun. When the moon moves between the earth and the sun, a round earth will be seen on the moon, that is, “full of the earth”, while the moon cannot be seen on the earth at this time.

When the moon moves to the other side of the earth and the earth is between the sun and the moon, the night side of the earth will face the moon, and the side illuminated by the sun will face the moon, so it will not be visible on the moon. Go to the earth (maybe you can see artificial lights), and at this time you can see the full moon on the earth.

In addition, the earth seen by Chang’e-3 is always at the same position in the sky. The earth does not move in the sky, but only changes in phase. This phenomenon is caused by the synchronous rotation of the moon. From the front of the moon, only the “earth does not fall” can be seen, but the “earth out” and “earth fall” will not be seen.

So far, only the 12 Apollo astronauts who landed on the moon that year have seen the earth with their own eyes. Although the Earth in the photo of Chang’e-3 looks very small, because the Earth is much larger than the Moon, you can actually see a very large Earth on the Moon with the naked eye, which is equivalent to 14 times the size of the full moon we usually see. Such a scene will be full of oppressive feelings for people with giant phobias.

With a distance of only 380,000 kilometers, the environment of the earth and the moon is worlds apart. There is no vitality on the moon, but the earth is an oasis of life. Without the protection of the earth, human beings cannot survive in the universe at all. The earth is currently the only known oasis of life.

The Earth, carrying billions of people, is floating in the universe, surrounded by continuous darkness and cosmic rays. When human beings wantonly destroy the earth’s environment, have you ever thought that the earth itself is so fragile in the universe?

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