- Imagine a line passing through the center of Earth that goes through both the North Pole and the South Pole. This imaginary line is called an axis.
- Earth spins around its axis, just as a top spins around its spindle. This spinning movement is called Earth’s rotation.
- The axis of the earth which is an imaginary line, makes an angle of 66½° with its orbital plane.
- The plane formed by the orbit is known as the orbital plane.
- The earth receives light from the sun.
- Due to the spherical shape of the earth, only half of it gets light from the sun at a time.
- The portion facing the sun experiences day while the other half away from the sun experiences night.
- The circle that divides the day from night on the globe is called the circle of illumination. This circle does not coincide with the axis.
- The earth takes about 24 hours to complete one rotation around its axis. The period of rotation is known as the earthday. This is the daily motion of the earth.
What would happen if the earth did not rotate?
The portion of the earth facing the sun would always experience day, thus bringing continuous warmth to the region. The other half would remain in darkness and be freezing cold all the time. Life would not have been possible in such extreme conditions.
