The Moon, the Earth's Companion
What do you norrqally observe about the Moon? Itshinesbrightest, whenever present in the night sky. It seems to go through phases and it seems to present the same side toward the Earth always. Let's first explain these observations. The Moon appears to be the brightest night object, because it is the nearest to the Earth. Its phases occur because of its revolution around the Earth. It revolves in an elliptical orbit round the Earth, once in 27.33 days. In the same time, it rotates once on its axis. Thus, we always see the same face of the Moon from the Earth. The Moon is the only other heavenly body on which human beings have landed. They have spent only a shdrt period, though, a total of only 13 days. They brought back samples of lunar rock and soil and much more information about the Moon which we'll
briefly describe. The Moon's surface has flat dark expanses called maria (seas), big and small aat$as,,mountabis and-qalleys. It also hasrilles, i.e., channels such as theones made on.the Earth by the cutting action of water in a river bed. There are also dome-like structures made of concentric mountain rings. The Moon rocks and soil are almost similar to the earth rocks and soil. However, they are older and contain much higher levels of some elements like titanium and lack elements like sodium and potassium. The lunar soil has the texture of fine damp sand. Unlike its face, the far side of the Moon has no seas, mountains or valleys. It has only uniformly distributed craters. The temperature of the Moon ranges from 130°C in areas directly under the Sun, to - 170°C on its night side. It has neither water nor any atmosphere. About three billion years ago the Moon's interior 'cooled. Since then, it has changed very little and has settled down to a quiet existence. Though the Moon is a dead world, it is of interest to us. Its mysteries are not fully understood yet. It awaits further exploration.