Moon – The large round object that circles the Earth and that shines at night by reflecting light from the sun are called moon
The moon is our nearest neighbor in the solar system.
It is the only satellite of the earth.
Moon is 384,400 km from the earth.
Since it is so near from us, hence it appears so big; compared to any other celestial body.
The diameter of the moon is just one-fourth the diameter of the earth.
The moon takes about 27 days to make one revolution around the earth.
It takes the same number of days to complete one rotation around its axis.
Due to this, only one face of the moon is visible from the earth.
Due to this, we get to see different shapes of the moon on different days of the month.
The moon’s surface:
The surface of the moon is not plane.
It has hills, mountains, valleys and craters. Craters are deep holes in its ground created by hitting of the heavenly bodies like meteorites on to the moon’s surface.
Mountains on the moon are very rough and sharp.
They are made of bare rocks and soil.
Soil of the moon is dry and is made up of small pieces of rocks.
Life does not exist on the moon, due to the absence of air and water.
As there is no air on the moon, no sound can be heard there.
The temperature of the moon also changes very quickly.
It changes with day and night. Moon is very hot when sun shines on it.
On the darker side it is very cold.
Astronauts that visit moon have to wear special dresses to bear the quick change in temperature.
Phases of Moon – The different ways the Moon looks from Earth over about a month are called the phases of the Moon.
Different shapes of the moon are Full moon, New moon, Crescent and Gibbous.
All these phases repeat again and again.
The moon never changes its shape.
The changing shapes of the moon that we see from the earth are actually the shapes of its lighted part; as it revolves around the earth.
On the new moonlight (Amavasya) the dark hemisphere of the moon faces the earth and it cannot see.
When the moon appears like a sickle, it is called the crescent moon.
Sometimes, the moon appears like a semicircle.
A “gibbous” moon is any moon that appears more than half lighted but less than full.
When the moon appears like a circular disc, it is called the full moon.
On the full moon night (Poornima) the bright hemisphere visible to use and we see full moon.
Gravity of the moon:
The force of gravity can also be felt on the moon. But the gravity of moon is 1/61 times less than the earth.
In other words, we would weigh less on the moon.
For example, if our weight is 30 kg on the earth, our weight on the moon will be only 5 kg.
For the same reason, one would find it very difficult to walk on the moon.
Unless one is weighed down, he/she would float.
Tides:
Due to gravity, moon pulls water from seas and oceans towards itself. This is called tide.
Tides are of two types-high tide and low tide.
Every high tide is followed by a low tide.
When water is pulled by moon it is called high tide.
In the area between two high tides the water forms low tides.
The highest tide occurs on full moon night.
Tides are useful to ships.
When there is a high tide, ships can come easily to a port.
The knowledge of tides is also important to fishermen when they go out for catching fish in the seas.
In a low tide, they cannot bring back their boats to the shore because the sea water recedes far away from the shore.
Eclipse – A shadow formed in space that makes the sun or moon invisible for some time is called eclipse.
Eclipses occur due to the revolution of earth and moon.
The position of moon and earth keeps on changing due to the revolving movements.
Eclipses occur when the sun, the earth and the moon are in straight line.
These are the most spectacular shadows cast by the earth and the moon by blocking the sunlight falling on each other.
Lunar Eclipse
When earth comes between the sun and moon, lunar eclipse occurs.
When the earth revolves around the sun, sometimes it comes between the sun and moon.
The shadow of earth casts on moon.
The part of the shadow that totally blocks the sunlight is called the umbra.
The other part that blocks only a part of the sunlight is called the penumbra.
Lunar eclipse can be total or partial.
When moon is completely in the dark shadow of the earth, it is called total lunar eclipse.
When moon is only partly hidden by the shadow of the earth, it is called partial lunar eclipse.
Solar Eclipse
When the moon comes between the sun and the earth, solar eclipse occurs.
We know that moon is much nearer to the earth than the sun.
When the moon revolves round the earth, it sometimes comes between the sun and the earth.
The rays of the sun cannot reach the earth.
In other words, you can say the shadow of the moon casts on the earth.
This is called solar eclipse.
When sun is completely hidden by the moon, it is called total solar eclipse.
When only a part of sun is hidden, it is called partial solar eclipse.
Satellite – A heavenly body that moves around a planet is called moon.
Moon is the natural satellite of the earth.
Man has also made artificial satellites that revolve around the earth in space.
Artificial satellites are man-made objects sent into space to orbit a planet.
The spacecraft is launched in the space with the help of rockets.
Rockets are the vehicles which are powerful enough to carry spacecraft away from the surface of the earth.
Saturn-V is the largest rocket ever built.
It launched American spacecraft Apollo 11 to the moon on 20 July 1969.
Sputnik 2 was the first spacecraft in which a living creature, a dog named, Laika was sent for the first time to the space.
Uses of artificial satellites:
Artificial satellites are sent to space for performing different tasks.
For example, Military satellites can spy, guide missiles and even used as weapons.
Communication satellites relay television, radio and telephone transmissions.
Weather satellites help with weather forecasting and also give warning about cyclones.
Scientific satellites carry out studies of the earth and its environment.
India has also launched many satellites into the space.
Its first satellite Aryabhata was launched in 1975.
Since then, satellites of many types including Bhaskara, Rohini, Insat I A, Insat 1 B, Insat 1 C and others have been launched.
On February 2017, Indian Space Research Organisation (ISRO) launched 104 satellites in a single rocket (PSLV, (- 37) and created a history.
