Chapter 1 Notes
The Earth in the Solar System
Class 6 – Social Science
|Chapter Name||The Earth in the Solar System|
|Chapter No.||Chapter 10|
|Category||Class 6 Geography Notes|
Question 1 Why we can not see the stars and moon during day?
Question 2 What are celestial bodies?
Question 3 What are the characteristics of stars?
Question 4 Why stars appears too tiny to us?
Question 5 What are constellation? Give examples.
Question 6 How can the pole star help in finding the direction?
Question 7 What is a planet? We live on which planet?
Question 8 What are satellites? Give example.
Question 9 What is a solar system?
Question 10 What are the favourable conditions that makes life possible on Earth?
Question 11 Why Earth is known as blue planet?
Question 12 What are asteroids?
Question 13 What are meteoroids?
Question 14 What is a galaxy?
Question 15 Explain some of the features of Earth.
Question 16 Differentiate between a Planet and a Satellite.
Question 17 What is the position of our planet, the Earth in our Solar System?
Question 18 How did people in the past determine directions?
Question 19 Why do we see shadows on the moon?
Question 20 Which is the biggest member of the Solar System? Discuss it.
Question 21 Why is Venus considered as ‘Earth’s Twin’?
Question 22 Why is the Milky Way galaxy named as Akash Ganga?
Question 23 How does the Moon appear different each night?
Question 24 Name the inner and outer planets. What are they made up of?
Question 25 Why do we see only one side of the moon all the time?
You can see one or two bright dots shining in the sky in the night. Soon the number increases and later the whole sky is filled with tiny shining objects – some are bright, others dim. They all appear to be twinkling. They simply glow without any flicker just as the moon shines.
Along with these bright objects, you may also see the moon on most of the days. It may, however, appear at different times, in different shapes and at different positions.
You can see the full moon only once in about a month’s time. It is Full moon night or Poornima. A fortnight later, you cannot see it at all. It is a New moon night or Amavasya. On this day, you can watch the night sky best, provided it is a clear night.
We can’t we see the moon and all those bright tiny objects during day time because the very bright light of the sun does not allow us to see all these bright objects of the night sky.
Celestial Bodies and Stars
The sun, the moon and all those objects shining in the night sky are called celestial bodies. Some celestial bodies are very big and hot. They are made up of gases. They have their own heat and light, which they emit in large amounts. These celestial bodies are called stars.
The sun is a star. Countless twinkling stars in the night sky are similar to the sun. But we do not feel their heat or light, and they look so tiny because they are very very far from us.
In the night various patterns are formed by different groups of stars. These are called constellations.
(1) Ursa Major or Big Bear is one such constellation.
(2) One of the most easily recognisable constellation is the Saptarishi (Saptaseven, rishi-sages). It is a group of seven stars that forms a part of Ursa Major Constellation.
In ancient times, people used to determine directions during the night with the help of stars. The North star indicates the north direction. It is also called the Pole Star. It always remains in the same position in the sky. We can locate the position of the Pole Star with the help of the Saptarishi.If an imaginary line is drawn joining the pointer stars and extended further, it will point to the Pole Star.
Some celestial bodies do not have their own heat and light. They are lit by the light of the stars. Such bodies are called planets. The word ‘planet’ comes from the Greek word “Planetai” which means ‘wanderers’.
The earth on which we live is a planet. It gets all its heat and light from the sun, which is our nearest star. If we look at the earth from a great distance, say the moon, it will appear to be shining just as the moon.
The moon that we see in the sky is a satellite. It is a companion of our earth and moves round it. Like our earth, there are seven other planets that get heat and light from the sun. Some of them have their moons too.
The solar System
The sun, eight planets, satellites and some other celestial bodies known as asteroids and meteoroids form the solar system.
The sun is in the centre of the solar system.
It is huge and made up of extremely hot gases.
It provides the pulling force that binds the solar system.
The sun is the ultimate source of heat and light for the solar system.
But that tremendous heat is not felt so much by us because despite being our nearest star, it is far away from us.
The sun is about 150 million km away from the earth.
There are eight planets in our solar system.
In order of their distance from the sun, they are: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune.
All the eight planets of the solar system move around the sun in fixed paths. These paths are elongated. They are called orbits.
(1) Mercury is nearest to the sun. It takes only about 88 days to complete one round along its orbit.
(2) Venus is considered as ‘Earth’s-twin’ because its size and shape are very much similar to that of the earth.
Till recently (August 2006), Pluto was also considered a planet. However, in a meeting of the International Astronomical Union, a decision was taken that Pluto like other celestial objects (Ceres, 2003 UB313) discovered in recent past may be called ‘dwarf planets.”
The earth is the third nearest planet to the sun.
It is the fifth largest planet.
It is slightly flattened at the poles. That is why, its shape is described as a Geoid. Geoid means an earth-like shape.
Conditions favourable to support life on the earth are :
(1) The earth is neither too hot nor too cold.
(2) It has water and air, which are very essential for our survival.
(3) The air has life-supporting gases like oxygen.
Because of these reasons, the earth is a unique planet in the solar system.
From the outer space, the earth appears blue because its two-thirds surface is covered by water. It is, therefore, called a blue planet.
Our earth has only one satellite, that is, the moon.
Its diametre is only one-quarter that of the earth. It appears so big because it is nearer to our planet than other celestial bodies. It is about 3,84,400 km away from us.
The moon moves around the earth in about 27 days. It takes exactly the same time to complete one spin. As a result, only one side of the moon is visible to us on the earth.
The moon does not have conditions favourable for life. It has mountains, plains and depressions on its surface. These cast shadows on the moon’s surface.
There are numerous tiny bodies which also move around the sun. These bodies are called asteroids. They are found between the orbits of Mars and Jupiter. Scientists are of the view that asteroids are parts of a planet which exploded many years back.
The small pieces of rocks which move around the sun are called meteoroids.
Sometimes these meteoroids come near the earth and tend to drop upon it. During this process due to friction with the air they get heated up and burn. It causes a flash of light. Sometimes, a meteor without being completely burnt, falls on the earth and creates a hollow.
A whitish broad band, like a white glowing path across the sky on a clear starry night is a cluster of millions of stars. This band is the Milky Way galaxy.
Our solar system is a part of this galaxy. In ancient India, it was imagined to be a river of light flowing in the sky. Thus, it was named Akash Ganga.
A galaxy is a huge system of billions of stars and clouds of dust and gases. There are millions of such galaxies that make the Universe.