Class 3 Science

Planet Earth – Class 3

Planet Earth

In our solar system, our Earth is the only planet to have life. About 71 per cent of the Earth is covered with water. Because we have so much water, Earth is also called the Blue Planet.

Earth - Blue Planet

Earth looks like blue planet when seen from space.

When the Earth was formed, it was a big ball, made up of rocks and gases. At that time it was very hot. There was no life on the Earth. As the years went by, its outer portion cooled down because of rain. We live on the outer, cool part of the Earth called the crust.

But it is still very hot deep inside the Earth. In the centre of the Earth is a solid ball of melted metals. It is called the core.

The part between the crust and the core is the mantle. It is also very hot. It is made up of hot flowing rocks.

The shape of the Earth

The Earth is a round ball. However, it is not perfectly round. It is slightly flattened at the top and bottom. Astronauts have seen the Earth from outer space. It looks like a blue ball from there.

The Earth spins

Push a pencil through a plastic ball. Now you can spin the ball around the pencil. Have you spin a top? It spins like a ball even though there is no pencil going through it. Our Earth spins in a similar way. It continuously spins around an imaginary line passing through it centre. This imaginary line is called the axis. The spinning of the Earth around its axis is called rotation.

Why don’t we feel the spin? This is because everything on the Earth spins along with it.

What causes day and night on the Earth? The spinning of the Earth causes day and night. At any time only one half of the Earth faces the Sun. Thus, only the part of the Earth that faces the Sun gets light and the other part remains in dark. As the Earth spins, the part of the Earth that was in dark gets light and the other part remains in dark. In this way, day and night occur. The part of the Earth which faces the Sun has day. The part of Earth which faces away from Sun has night. As the Earth rotates, day and night follow each other.

It takes 24 hours for the Earth to complete one rotation on its axis. That is why one day and one night make up 24 hours.

The Earth goes around the Sun

Planets moving around the Sun it its orbit.

The Earth while spinning on its axis, also keeps going around the Sun in its orbit. The orbit is a fixed path on which the Earth revolves around the Sun. This movement of the Earth is called revolution. The Earth completes one revolution around the Sun in one year (365 days and 6 hours).

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