The imaginary line that separates light from the darkness and day from the night is known as the circle of illumination. Earth’s axis refers to an imaginary line going through the centre of the earth from top to bottom. The circle of illumination cuts all latitudes into half on the spring and autumnal equinoxes. The circle of illumination bisects the equator while the circle of illumination separates light from darkness and day from night, the axis is a line along which the earth rotates.