MOON AND ECLIPSE
un is the center of the solar system. The planets, the asteroids, the comets, the meteors and other bodies revolve around it. The satellites revolve around the planet. Earth is the only planet where life is possible. It has only one natural satellite, moon which revolves around it.
The Moon is the only natural satellite of the Earth. It can be seen from Earth. It is the source of light in the night on Earth. It is about 380,000 km away from the Earth.
It is much smaller than Earth about quarter of Earth’s size. The gravity on the moon is one-sixth of the Earth’s gravity. It means that something will be six times lighter on the Moon than on Earth. The surface of the moon is covered with rocks and dust. It has mountains and flat plains.
There are also large round ditches which are called craters on the surface of the moon. No life can exist there since it has no air and water. The moon revolves around the Earth. It takes moon 27 days 7 hours and 43 minutes to complete one revolution around the Earth.
The moon does not have light of its own. It shines because it reflects the light of the sun falling on it.
PHASES OF THE MOON
As we know that moon has no light of its own. It reflects the light of the Sun. When it revolves around the Earth different part of the moon gets lit up by the sun and hence moon appears differently each day from the Earth.
This difference in the appearance of moon each day, as visible from the Earth is called the phases of the moon. In a month, we might have noticed that moon first grows bigger upto full moon and then it gets smaller to no moon.
When the part of the moon gets bigger each night to full moon, it is called waxing. It is waning when moon appears to get smaller each night. There are total 8 phases of moon. They are as follows:
- The new moon is when the moon is not visible. The side facing us does not get sunlight and thus, we cannot see the moon.
- The crescent moon is the moon which is seen after new moon and before quarter moon. In this stage only a thin edge of its lighted side which appears to be in C shape.
- After the crescent moon the quarter moon appears; half moon is visible. If it is waxing of moon it is called first quarter, if the moon is waning, it is called last quarter.
- Between the full moon and the quarter moon there lays the gibbous moon. More than half of the moon is visible.
- After this comes the full moon. The whole moon is seen lit from the Earth.
- After this the full moon begins to shrink or wane. We then see a gibbous, last quarter and the crescent phase in order. After one month we get back at new moon.
MOON AND THE TIDES
The 75% of the surface of the Earth is covered with water. The periodic rise and fall of the water in sea or ocean due to the gravitational pull between the moon and the sun, and the rotation of Earth is called as tide.
Though the gravitational force of moon is weak but it has effects on the Earth. It occurs two times in a day. The water of the oceans bulges out in the direction of the moon due to its gravitational force. It causes high tides.
Another bulge occurs on the opposite side, since the Earth is also being pulled toward the moon (and away from the water on the far side). It causes the low tides. They depend on the phases of the moon. The highest tides occur at the times of the full moon and new moon.
When the three celestial bodies: the sun, the moon and the Earth are in a line then they have their shadows on each other. These are called eclipses. There are two types of eclipse: lunar and solar eclipse.
Solar Eclipse: The solar eclipse occurs when the moon walks between the Earth and the sun. The light of the sun is obstructed by the moon to reach the surface of the Earth. The moon partially or totally covers the sun. It occurs on ‘no moon’ day. It lasts for very short duration.
Lunar Eclipse: During the lunar eclipse the Earth comes between the moon and the sun. The shadow of the Earth falls on the moon. The light of the sun does not reach the moon. The moon appears red brown or black from the surface of the Earth. It occurs only on a full moon night. It lasts longer than solar eclipse.
A satellite revolves around the planets. There are both natural and artificial satellites in the space. The moon is the natural satellite of the Earth. There are many artificial satellites in the space today. They are of various shapes and sizes. The size of the satellite depends upon the function of the satellite.
The first artificial satellite that reached the space is Sputnik-1. It was launched by Russia in 1957. Aryabhatta was the first artificial satellites of India, launched in 1975. The other satellites launched by India are Cosmos, Rohini, RS-I, RS-DI, APPLE, RS-D2,INSAT-2C and many more.
Artificial satellites have wide variety of uses. Some of them are as follows:
- They are used in the research and study of the universe by the scientists.
- It helps in forecasting the weather.
- It helps in broadcasting TV programmes from one country to another.
- It helps in supporting the military activities.
- They enable aircrafts, ships and land vehicles to determine their locations accurately.
- They help in receiving alert messages before dangers like cyclones or storms.