Answer: Darkness does not fall on the earth immediately after sunset. The surface is illuminated in low light. This time is called twilight. Again, just before sunrise, the surface darkens and light emerges. This time is called dawn.
What causes twilight and dawn?
The sun is below the horizon before sunrise and after sunset. As a result, sunlight cannot reach the earth’s surface directly. At that time, the sun’s rays fall on dust particles and other particles floating in the air very high above the earth’s surface, resulting in scattered reflections of light. Some of that reflected light reaches the surface. The state of light before sunrise is called dawn and the state of light after sunset is called twilight.