A Model of
the Earth-Notes
The Earth
is like a bali
In this picture, you can see that the shape of the Earth is like that of the Moon. Bring some globes to the classroom. Ensure that each group of five to six students has a globe. A globe is a model of the Earth. It shows the shape of the Earth, the land and water, the continents and oceans and the countries of the world.
Doesn’t the Earth look like a blue moon? It looks blue because a large portion of the Earth is covered with oceans. In the above photograph, we can see only one part of the Earth which receives sunshine.
You can see that the earth is like a ball – spherical in shape. How do you think people stand on it? Place some standing toy people on different parts of the globe. It may seem that the person at the lower part is standing upside down or that the person in the middle might just fall from the Earth. We never fall off the Earth because the Earth acts like a powerful magnet which pulls us towards it. In fact, we can only fall on Earth but never off the Earth!
An interesting thing about the shape of the Earth is that if we keep travelling from one point in one direction without turning back, we come back to the same point. Try this on the globe. Start from any point and keep going in the same line and see if you come back to the starting point.
Scientists in ancient period in India and Europe had figured out that the earth was like a ball or sphere. Therefore, later around 1492 CE, sailors like Columbus, an Italian explorer set out from Europe with the hope of reaching India.
Oceans and
Continents
As you can see on the globe, most of the surface of the Earth consists of water in the form of oceans. If you go to a coastal village , you can observe hills.
Seas and Oceans stretch for hundreds and thousands of kilometers – just endless water! You can travel from one end to the other only with the help of ships and it may take many days or even months to do so.
Naturally, we cannot live in these oceans. We live on land. You can see large sheets of land on the globe which are called continents. There are seven continents.
Directions on the
globe
You had learnt about the four directions in the earlier chapter. You can locate the North and the South Pole. If you face north, the east is on your right and the west is on your left. The Earth rotates every day from the west to the east. Can you rotate the globe and see how this happens? You have observed the two poles on the globe. What are the poles? They are the two points on the opposite ends of the Earth. If you draw an imaginary line connecting the two poles passing through the interior of the Earth, it will form the axis or the line around which the Earth rotates.
To understand this better, put three or four dots on the globe in different colours from the Equator to the poles. Now rotate the globe and observe You would notice that if you put a dot on the pole, it will not move at all! What happens to the dot placed on the Equator?
Lines on
the globe
You will see many lines across the globe. Some run from the North Pole to the South Pole. The others run around the Earth from west to east. These imaginary lines drawn by map makers help us locate places on the globe and maps. We will see how they are drawn in later classes. Now, we will look at the most important lines. The concept of lines on the globe called Latitudes and Longitudes along with poles were well known to our Indian ancestors like Aryabhata, who used the terms to explain the places.
Latitudes
These are the imaginery lines that are drawn from west to east. Can you spot these lines? Compare the length of these lines. Do you think they are all of the same length?
The longest of these lines is called the Equator. It divides the globe into two equal halves called hemispheres. Identify the Equator on the globe and note down the continents it passes through. Also identify the northern and the southern hemispheres. In which hemisphere is India located? Which hemisphere has more water than land?
Longitudes
These imaginary lines run from one pole to the other. Unlike the latitudes, these lines are of the same length. There are two main longitudes – the Greenwich Line, which is also called the 0 degree longitude, and the International Date Line, which is also called 180° east/west longitude. You will learn more about the importance of these lines in higher classes.
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