Question

What do you mean by the circle of illumination?

Answer 1

The circle of illumination is an imaginary line that separates the half of the earth that is illuminated by the sun (day) from the half that is in darkness (night). It divides the earth into two halves, one experiencing daylight and the other experiencing nighttime, and this division shifts as the earth rotates, causing the cycle of day and night. The length of day and night varies at different places and times of the year, with the least variation at the equator and the most at the poles.