Josua Craig, of Kings High School, asks :-
Why is the night darkest just before dawn?
Alan Gilmore, an astronomer at the University of Canterbury's Mt John Observatory, responded.
It isn't. The idea comes from an old English proverb but modern science doesn't support it. Measurements of the night sky show that its darkness doesn't change in any regular way between the end of evening twilight and dawn.
Meteors, or shooting stars, are more obvious before dawn than in the evening. Possibly this has given rise to the idea that the dawn sky is darker. In fact the prevalence of pre-dawn meteors is due to the movement of the earth. The morning side is the leading edge of earth's movement around the sun. Meteors are specks of dust mostly orbiting the sun in the same direction as earth. Evening meteors are catching up on earth so hit the atmosphere relatively slowly. Pre-dawn meteors are going in the opposite direction and we meet them head-on. Since the brightness of a meteor depends on its speed, morning meteors are brighter.
Possibly the proverb has a more subjective origin. Anyone forced to stay up all night is likely to be tired, cold and miserable by dawn. So the sky just seems darker.