Most folks enjoy the beauty of a perfect sunset—but in reality, the celestial body of the sun never “sets”. Our planet Earth rotates (spins) on its axis at the same time that it orbits (revolves) around the sun.
Laymen use terminology of the sun “setting” even though Galileo proved Earth rotates toward the east, which is why the sun “rises” in the east and “sets” in the west.
The reason darkness comes upon Earth is because Earth turns away from the sun’s brilliant light—the sun never turns away from Earth. This means whichever continents that are within the sun’s rays will soon enter darkness as Earth turns away. And just like Earth always goes into darkness, the same can be said for why beings go into darkness: