Why does the moon shine? Why is the surface bright and dark?

The moon is the only natural satellite on our earth. When the curtain falls in the month and the weather is fine, we will see the moon shining, but some will blink? Then let's use constellation knowledge to reveal the reasons! Let's have a look!

Why does the moon shine?

The moon itself does not shine, but reflects sunlight.

The brightness of the moon varies with the angular distance between the sun and the moon and the distance between the earth and the moon. The brightness at the full moon is more than ten times higher than that at the top and bottom chords.

The average brightness of the moon is 1/465000 of the brightness of the sun, and the brightness varies from 1/630000 to 1/375000. The average brightness at the full moon is-12.7, etc. Its average illumination to the earth is 0.22 lux, which is equivalent to the illumination of 100 watt electric lamp at a distance of 2 1 meter.

The surface of the moon is not a good reflector, and its average albedo is only 9%, and the other 9 1% is absorbed by the moon. The albedo of Guangdong Sea is even lower, about 7%. The albedo of the lunar highlands and craters is 17%, and it seems that the mountains are brighter than the moon sea.

The distance from the moon to the earth is about 1/400 of the distance from the earth to the sun, so the moon is as big as the earth to the sun.

Because there is no atmosphere on the moon, the heat capacity and thermal conductivity of lunar materials are very low, so the temperature difference between day and night on the surface of the moon is very large. During the day, where the sun shines vertically, the surface temperature of the moon is as high as 127℃. At night, the surface temperature can be reduced to-183℃.

The temperature of lunar soil can be measured by radio observation. This measurement shows that the temperature in the deeper part of the lunar soil rarely changes, which is precisely due to the low thermal conductivity of lunar material.

Why is the surface of the moon bright and dark?

The brightness of the moon surface is caused by the topography of its surface. On earth, the dark part of the moon seen by the naked eye is actually the moon sea. The topography of the Moon Sea is generally low, similar to the basins on the earth. The moon sea is lower than the average horizon of the moon1000 ~ 2000m, and the southeast of some sea areas is even 6000m lower than the surrounding area. The albedo of the moon and the ocean (a physical quantity indicating the ability to reflect sunlight) is relatively low, so it looks dark.

The area above the Moon Sea on the surface of the Moon is called the Moon Land, which is generally 2000~3000 meters above the horizon of the Moon Sea. Because of the high albedo, it looks brighter. On the front of the moon, the area of the moon land is roughly equal to that of the moon sea, but on the back of the moon, the area of the moon land is much larger than that of the moon sea.

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Under the long-term effect of the earth's gravity, the center of mass of the moon is not in its geometric center, but on the side close to the earth, so the gravitational potential energy of the moon relative to the earth becomes the smallest. In the process of the moon's revolution around the earth, the center of mass of the moon always faces the side of the earth, just like the earth binds the moon with a rope.

The same is true of other satellites in the solar system, so it is not a coincidence that the rotation period of the satellite is equal to the period of revolution, but there are internal factors.