The Moon is the nearest celestial
body. As it rotates not on a circular, but on an elliptical orbit,
the distance between the Earth and the Moon varieties from 363 000
km to 405 000 km and its average is 384 000 km. It makes a full
rotation around the Sun for 27 days and 8 hours and is always
turned to us with one hemisphere. This is so because the time for
around-the-axis rotation of the Moon coincides with the period, for
which it makes a full rotation around the Earth.The diameter of the Moon is 3 476 km. Its volume is 50 times smaller than this of the Earth and its mass- 81 times. The surface of the Moon altogether is almost as much as the territory of America. Because of its light mass, the Moon attracts the bodies with a slighter than the Earth’s power. That is why it couldn’t preserve its initial gas cover. Now it has no atmosphere. On the Moon’s surface the gravity force is only 1/6 of the Earth’s. A man, who weighs 72 kg on the Earth, would weigh only 12 kg on the Moon.
The day, just as the night on the Moon, continues almost for 15 Earth days ( 24 hour periods). Fir this time its soil succeeds to be warmed up to + 130 * C by the Sun rays and after the dawn of the Sun quickly cools to – 150*C.
Because it is very near to us and has no atmosphere to distract observations, the Moon is undoubtedly the best studied celestial body. Most detailed cards of its surface already exist.
There are no animals, plants and water on the Moon. It is a dead stone desert covered with uneven rocky substance. At dawn the Moon is reddish, high up on the night sky it is yellowish and on the background of the blue sky during the day it is almost white. But these all are optic illusions. The true color of the rocks covering the Moon is brown-darkgrayish.
A few dark spots can be seen on the Moon even with a naked eye. These are “seas”- planes with a darker, uneven surface. They are called “seas” only because of a tradition from the past, when people didn’t know that there is no water on the Moon. Their names are also historical, given by chance: Sea of the Rains, Sea of the Fertility, Sea of the Crises, Ocean of the Storms… Even though that there are no storms and rains on the Moon. With a telescope can clearly be seen around ten mountain chains named after terrestrial mountains: Apennines, Alps, Kavkaz, Carpets, Perinea…They are very high and on them there are tops which can be compared only to the highest top on the Earth.
The most characteristic formations on the surface of the Moon are undoubtedly the circular mountains with a hill in the center, which are called circuses ( the bigger ones) and craters 9 the smaller ones). Their number only on the visible hemisphere is beyond 300 000 ( with a diameter of above 1 km) and on the other side they are even more. Among them there are gigantic circuses with a diameter of more than 200 km and a number of very small craters ( called “poles”) with a diameter of a hundred meters.
The cosmic stations have helped a lot is studying the Moon. Taking photographs of the other hemisphere of the Moon has only become possible due to them. The Russian automatic interplanetary station “Moon-3”first succeeded to submit pictures on October, 7, 1959 from the invisible side of the Moon. Since then the surface of the Moon ( both from the visible and the invisible side) has been photographed in close-up many times by the Russian AIS “Moon” and “Sonda” and the American ones “Ranger”, “Surveyor”, “Lunar Orbiter” and ‘Apollo”. These flights gave scientists an opportunity to create a full and most detailed card of the Moon and to study carefully its surface. It was confirmed that it is not covered with dust, that it is uneven and hard enough to stand cosmonauts and transport equipment when people land on it. It was also found out that there are a lot of stones on its surface and that our natural satellite has practically got no magnetic field.
With the Moon is connected a phenomenon which we can observe almost every year ( sometimes even two or three times per year) – Moon eclipses. They are caused by the shadow of the Earth when the three celestial bodies ( Sun, Earth and Moon) happen to be in a straight line. As the diameter of our planet is nearly four times as much as the diameter of the Moon, its shadow, even at a distance of 380- 400 000 km, is two and a half times bigger than the dimentions of our satellite. Thus the Moon can completely disappear into the shadow and get darkened for a long time- up to 1 hour and 40 minutes.
In contrast to Solar eclipses, Lunar ones can be observed from the whole unlighted hemisphere of the Earth. This is so because the Moon, which does not have a loght of its own, actually stops shining. The Sun, on the other hand, cannot be seen only on these places, where the shadow of the Moon falls. Solar eclipses happen only during new moon, while Moon eclipses happen only during full moon.
Lunar eclipses repeat themselves at the same period of time as Solar ones do. During a saros there are approximately 13 full and 15 partial (when not the whole moon is in shadow) Moon eclipses.Both full and partical Lunar eclipses have been well-known and observed since ancient times and on their basis special Moon calendars were created.
