Topic outline

    • Our Earth

      Our earth is an interesting place where we live. We see high mountains, lush green valleys, deep oceans, sea, river, ponds, as well as vast desert.

      Our earth is one of the eight planets that revolve around the sun in the solar system. Eight planets of the solar system are: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune. The largest planet in the solar system is Jupiter, smallest planet is mercury, brightest planet is Venus and coldest planet is Neptune.

      Earth is the fifth-largest planet in the solar system and the third-closest planet to the sun. Earth is about 150 million km away from the sun. It is just at right distance from the sun, have liquid water and layer of air to sustain life.

      Is the earth really round?

      The earth seems to be flat to us and it is difficult to believe that earth is sphere with a bulge at its equator and flattened at its top. Long back, people believed that earth was flat that’s why they fear to sail far out to sea, as they may fell off the edge of the earth! Then some sailor sailed around the earth and came back to the same place from where they have started. Now it has been seen by astronauts from the space that earth is round, flattened from the top and swelled at the equator.


      Rotation of the earth

      Spin a bangle on any table top. Do you see any imaginary line in the spinning bangle? This imaginary line that we see is called axis.

      The earth also spins on its axis. This movement is called rotation. The earth spins from west to east and complete its one rotation in approximately 24 hours. We don’t feel earth spinning because everything including us is spinning along the earth at the same speed. It is the earth's rotation that causes day and night.


      Why do we have day and night?

      Earth is always moving on its axis which allows sunlight to shine on different parts of the earth. The area of the earth facing the sun receives sunlight, experiences day and the area of the earth which does not receive sunlight, experiences night. At all time, half portion of the earth is lighted by the sun and half of the earth remains in darkness.

      Let’s understand this with an activity.

      Take a globe and fix it on table. Now light a torch from front of the globe.

      What do you observe?

      We can see that half portion of the globe is lit by the torch represents day and the darker portion of the globe represents night.

      How we can say that the earth turns around like a top?

      Place long stick in the ground in the sunlight. We can see the shadow on the ground. Mark the shadow. Observe the shadow after of an hour. We can see that this time size and direction of the shadow is different. Repeat this observation for next 2 to 3 hour. We will find that the size and direction of the shadow keeps on changing every hour. Change in shadow position shows that the earth is constantly moving.


      Revolution of the earth

      As the earth rotates, it also moves around the sun in a fixed path. This fixed path in which earth moves around the sun is called Orbit. Movement of the earth around the sun in its fixed orbit is called revolution. Earth takes one year to complete one revolution. Earth is slightly tilted from its axis. Earth tilt’s and its movement around the sun in its fixed path causes seasons.

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