Question

What is the circle of illumination? Why does it not coincide with the axis of the Earth?

Answer 1

• The circle which separates day from night is called the circle of illumination.
• This circle does not coincide with the axis because of the inclination of the axis by $23{\frac{1}{2}}^{\circ }$ towards east.
• The earth takes 24 hours (one day) to complete one rotation around its axis.