Movements Of The Earth

Spin of Earth — Days and Nights

It was the old belief that the Earth was stationary while the Sun and the Moon were revolving around it. The occurrence of days and nights was due to their motion. Later, when it was found that Earth is round, this idea was found to be wrong. By carefully observing the motions of other stars, scientists were able to prove that the Earth we are standing on is not only circling around the Sun but is also spinning about its own axis as well. Just like a top rotating about its pin (Figure 10.2), the Earth rotates about its axis. This rotation is known as spin of the Earth (Figure 10.3). The axis is an imaginary line passing through the North and South poles of the Earth.
   
The occurrence of days and nights is due to the spin of the Earth. The Earth rotates from West to East. That is why the Sun appears to rise in the East and sets in the West. Our Earth also rotates in front of the Sun in the same way. There is day in the half part of the Earth that is lighted up by the Sun and there is night in the other half not facing the Sun. Days and nights are caused by the spin of the Earth about its axis. The Earth completes its one rotation about its axis in 24 hours, so the total duration of one day and one night is 24 hours.