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The Moon
Moon
All of you must have been seen the moon in the night sky. Though the moon and the sun look almost the same in size , but the moon is tiny is comparison to the sun . It looks big because it is very near to the earth. It is around 3,48,000 kilometre away from the Earth. The moon is a natural satellite of the earth . A natural satellite is a heavenly body that orbit a planet. The moon takes about 27.3 days to complete one revolution around the earth. The moon was probably formed 4.5 bullion years ago. It is believed that a large object hit the earth and blasted out rocks. These rocks together orbited the earth . They eventually melted, joined together , cooled and became the moon.
Why the moon shines
The moon does not have any light of its own, yet when full, it is the brightest object in the sky. The moon shines when the sun's light falls on its surface and its reflected back to the earth.
Condition on the moon
The moon is about one - fourth of the earth in size. Like the earth the moon also full all the object towards itself. This is called gravity. But the gravity of moon is only one- sixth of the gravity of the earth.
It means that if you can jump 1 m on the earth you can jump 6 m on the moon.
Due to this gravitational pull , the moon has no atmosphere.
The absence of atmosphere result in many phenomena.
➢ The moon has no wind or weather.
➢ As sound waves need air to travel, no sound can be hard on the Moon. So the moon is an absolutely quite place.
➢ We know that on the earth, the atmosphere absorb some of heat coming from the sun. But on the moon , days become extremely hot in the absence of an atmosphere.
Similarly at night, in the absence of an atmosphere , all the heat from the Moon's surface escapes. so, it gets freezing cold.
The average sarface temperature of the moon is 107°C the day and -153 °C at night.
No atmosphere means no protection from the meteoroid falling from the space. That is why , many meteoroid hit the moon's surface now and then.
The surface of the moon
The surface of the moon is covered with rock and dust. It has tall mountain and flat lava plains.
Mons Huygens is the tallest mountain on the moon. It is almost half has tall has Mt. Everest, the tallest mountain on the earth.
These are Many large and deep circular hollow on the surface of the Moon. They are called craters . They were formed from meteoroid , asteroids and other rock falling from space. Some of the craters are hundreds of the kilometre wide . You can see craters using a telescope . Due to the absence of an atmosphere, the surface of the moon can be seen clearly.
Movement of the moon
Like the earth, the moon also shows two kinds of movements - rotation and revolution .
But the time taken by the moon to rotate on axis is equal to the time it takes to orbit the earth . That is why we always see only one side of the Moon.
Phases of the moon
Moonlight is actually the light from the sun reflected off the Moon's surface. As the moon orbits the earth , the relative position of the sun , the earth and the moon keep changing. Thus, the lighted part of the moon as seen from the earth also keeps changing .
That is why the space of the moon appear to change everyday
The changing shapes of the Moon are called the phases of the Moon.
When the side of the moon facing the earth is not lit by the sun, no moon is visible . We call it the new moon . Gradually , some of the illuminated part of the moon faces the earth and we see that part of the moon .
One day when the whole side of the Moon that is lit by the sun faces the earth, the whole moon appear to be illuminated. We call it the full moon.
All the phases of the Moon from a new moon to a full moon are called waxing phases of the Moon . Waxing means increasing.
After the full moon, the illuminated part of the moon , as seen from the earth , keeps decreasing and finally becomes invisible. All the phases of the Moon from a full moon to a new Moon are called waning of the moon. Waning means decreasing.
Thus, the phases of the moon appear in a cycle. It take the moon 29.5 days to go from one new moon to next. This period is called lunar month.
